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Facial Prosthesis

Presented by:

DR. SUDHIR MEENA

Introduction

◼ The fabrication of an extraoral prosthesis is as

much an art as it is a science.

◼ The ideally constructed prosthesis must

duplicate the missing facial feature so precisely

that the casual observer notices nothing that

would draw attention to the prosthetic

reconstruction.

Ocular prosthesis

◼ The goal of any ocular prosthetic procedure is to return

the patient to society with a normal appearance and

reasonable motility of the prosthetic eye.

◼ The disfigurement resulting from loss of an eye can

cause significant psychological, as well as social

consequences.

◼ However, with the advancement in ophthalmic surgery

and ocular prosthesis, the anophthalmic patient can be

rehabilitated very effectively.

Anatomy of eyes

◼ Each eyeball is lodged

with in the bony socket

called orbit.

◼ The eye has 3 coat:

1. The outer coat, of

sclera and cornea.

2. Middle of uvea or

vascular coat.

3. Inner coat of retina.

◼ Ambroise Pare, a french surgeon-dentist, is considered

to be the pioneer of modern artificial eyes.

◼ In 1575, Pare fabricated artificial eyes made of glass as

well as porcelain. Acrylic resins has replaced this

material by the early 1940.

◼ Unlike a glass eye, an acrylic resin eye was easy to fit

and adjust, unbreakeable, inert to ocular fluids,

esthetically good, longer lasting, and easier to fabricate.

Surgical considerations in ocular

implants

◼ The surgical procedures in the removal of an eye

are classified into 3 category :

◼ Evisceration

◼ Enucleation

◼ Exenteration

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evisceration

◼ It involves removing the contents of the globe

but leaving the sclera and sometimes the cornea

in place.

◼ Motility of the implanted eviscerated globe is

excellent, since the extraocular muscles are

intact.

enucleation

◼ It is the surgical removal of the eyeball after the eyemuscles and optic nerve have been severed.

◼ The optic nerve and its associated are severed and tiedclose to the posterior wall of the capsule.

◼ The implant is placed, and the posterior portion oftenons capsule is closed over the implant providing thefirst layer of closure.

◼ Then, the anterior portion of tenons capsule andconjuctiva are then closed to from the second and thirdlayers over the implant.

exenteration

◼ It is the removal of the entire content of the

orbit including the including the extraocular

muscles.

Materials and types of ocular

implants

◼ The first material used for orbital implants was

glass.

◼ Mules introduced the hollow spherical glass

implant in 1884,which is still used today and

prefered by many opthalmologists.

◼ Since that time, many materials have been tried,

including cartilage, fat, bone, silk, wool

aluminium, cork ivory vaseline, and paraffin.

ocular implants are classified :

◼ Integrated

◼ Semi-integrated

◼ Non-integrated

Integrated and non-buried implant

◼ Rudermann introduced the

first partially exposed,

integrated implant. But these

implants had limited success

due to extrusion,migration

limited success due to

extrusion, migration and

excessive infection rate. They

were abandoned by the 1950.

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Semi-integrated and buried implants◼ These implants consist of an acrylic

resin implants with four protrudingmounds on the anterior surface.,these acrylic resin mounds on theimplant protrude against theencapsulating tissue.

◼ Since this implant is buried, there isalways tissue between the implantand the ocular prosthesis.

◼ The “keying” effect of theprotruding tissue mounds againstthe ocular prosthesis provideexcellent support and motility.

Non-integrated and buried implant

◼ The buried, non

integrated implant is the

most common method

of replacing volume loss

in the socket following

enucleation or

evisceration.

Ocular impression

◼ When the surgical site is well healed and

dimensionally stable fabrication of an ocular

prosthesis can begin. A thorough examination of

the enucleated socket must be made to ensure

proper healing and the absence of socket.

◼ Lignocaine is used as a surface anesthetic to

reduce the irritability of mucosa while taking

impression.

◼ An impression of the socket is made with an ophthalmic irreversible hydrocolloid in conjunction with a suitable impression tray .

◼ Stock acrylic resin impression tray have a hollow handle which accommodate an impression syringe.

◼ The alginate material may then be injected directly into the socket through the seated tray during impression making.

◼ The patient is seated in an erect position with the head tilted backward at approx. 45 degree, while the socket is being filled with the impression material.

◼ Once filled the head is moved back to the vertical position and the patient is directed to move their eyes both up and down.

◼ This will facilitate the flow of the impression material into all the aspects of the socket.

◼ After the material sets, the cheek nose and eyebrow regions are massage to break the seal.

◼ While the patients gazes upward, the cheek is pulled down and the inferior portion of the impression is rotated out of the socket.

◼ Then the impression is checked for accuracy and voids.

Preparation of the cast

◼ The impression is poured in 2 section with dental stone.

◼ The first poured stone is coated with a separating medium, such as a tin foil substitute and allowed to dry.

◼ The second half of the mold is poured with dental stone, leaving funnel shaped hole around the stem of the tray.

◼ This hole will be used as a funnel to fill the mold with molten wax. After the dental stone has set, the 2 halves of the mold are separated and the impression material is removed.

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Wax pattern

◼ Ivory inlay wax is used for wax pattern. After the wax has melted, it is poured through the funnel shaped hole and into the assembled mold.

◼ After the wax has cooled, the mold is opened and the wax pattern has been smoothed and polished.

◼ Then it is ready to be tried in the eye socket.

◼ The wax pattern will feel comfortable to most patient, but in some instance, it may cause mild irritation.

◼ The wax will not move as freely as the finished acrylic resin prosthesis, but the application of an ophthalmic lubricant will aid movement.

◼ Pressure points or areas of discomfort should be noted and relieved as necessary.

Iris Position

◼ The wax pattern is inserted in the socket and the patient instructed to look straight ahead at a distant point using the companion eye for comparison.

◼ A dot was placed with red ink in the location of the centre of the pupil, a circle was marked representing the iris area.

◼ A thin layer of approx. 0.5 to 1mm of wax from this marked area was removed and the iris-corneal button was placed over there and margins were flushed.

Selection of iris component

◼ Ocular discs which are

used in the iris painting,

are available in half mm

sized increments, ranging

from 11mm to13mm.

◼ They come in black or

clear, and either with or

without pupil apertures.

Fabrication of the sclera

◼ The wax sclera is now ready to be invested. After filling the lower portion of the flask with dental stone ,Stone is carefully vibrated onto the posterior surface of the wax pattern.

◼ The wax pattern is laid on top of the stone in the flask, taking care not to entrap air.

◼ After the stone has set, it is coated with a separating medium, such a tinfoil substitute.

◼ Then the flask is reassembled, the upper half of the flask is filled with dental stone, and the flask lid is placed on top to close the mold.

◼ After the stone has set, the flask is separated by

gently pyring it apart .

◼ The wax pattern is lifted out and the mold is

checked for voids.

◼ After the mold is cleaned, a coat of tinfoil

substitute is applied to both sides.

◼ Then white scleral acrylic resin is packed into

the mold, using the compression method.

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Painting the iris and sclera

◼ There are 5 basic component to painting an iris, namely, the pupil, base color, the detail, collarette and the limbus.

◼ Iris painting is usually completed in 2 stages:

◼ First the basic color of the body of the iris is selected , the base color is usually blue, gray, green, brown or a combination of these colors.

◼ Then, one or 2 coats of the mono-poly syrup is applied to the painted surface of the iris disc and allowed to dry.

Adhering the painted disc to the

corneal button and processing◼ To adhere the painted disc to the

corneal button the disc is placed on a flat surface, with painted side up.

◼ 1 or 2 drops of monopoly is applied to the painted surface immediately.

◼ The corneal button is position on top of the painted disc and press down lightly untill excess monopoly is forced out &the corneal button is seated firmly on the disc, the assembly is allowed to dry for about 30 mins.

◼ Now the corneal button

is ready to be inserted

into the mold.

◼ The scleral polymer is

mixed with monomer.

◼ Once the acrylic resin is

in the dough stage it is

added to the top of the

button and two half of

the flask press together

under pressure.

◼ Then processing is done.

Scleral and second iris painting

◼ After processing and removal, reduction of anterior curvature of the prosthesis is done to allow room for scleral and second iris painting.

◼ Reduction is approx. 1mm and is done by pear shaped bur.

◼ After smoothening of reduced surface a layer of monopoly is applied and allow to dry. Now prosthesis is ready for painting.

◼ Spokes of the iris are painted by using either a small

‘ooo’ brush or by flaring the hair of larger brush

◼ The collarette which is a circular area or star burst

found around the outside border of pupil is painted

with lighter or brighter color to that of the body of iris.

◼ Finally the limbus is added this is the area at the

junction of the iris and sclera, it is usually a

combination of grays and iris body color.

◼ Then the next step is scleralpainting, the natural sclera hasveins present that are usuallyapparent in both the nasal andtemporal corners of the eye.

◼ Red cotton fibers are used toreplicate the veins ,then the fibresare separated and cut fromcommercially available thread.

◼ The pattern of the natural eye arecopied by tacking the fibres to thesclera with a brush and monomer.

◼ The colors found in the sclera areusually yellow and blue orcombination .

◼ Once completed a coat ofmonopoly is applied to the sclera.

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Final processing

◼ It is done by clear heat cured resin.

◼ The eye is placed into the tissue side of the

molds anterior curvature facing up.

◼ The acrylic resin dough is placed on the painted

surface .

◼ After processing and removal the surface is

smoothed with a fine white stone and polished

with flour of pumice.

Delivery of prosthesis

◼ The prosthetic eye is washed with soap &water,a drop or two of an ophthalmic lubricant on thesurface of the prosthesis will facilitate insertion.

◼ After insertion eye are examined for aestheticappearance and the degree of movement byinstructing the patient to perform the movementin various direction.

◼ Necessary adjustment were carried and theprosthesis was finished , polished and inserted.

Auricular prosthesis

◼ Auricular defects occur secondary to congenital

malformations, trauma or surgical removal of

neoplasms.

◼ Before going for prosthesis one should look for:

1. Whether defect is reconstruction to total resection.

2. About recurrence for tumor.

If possible a preoperative impression and photographs,

make construction of post surgical auricular prosthesis

simple.

Surgical consideration

◼ If Surgical reconstruction of theauricle is not contemplated theentire ear should be removedleaving a flat tissue bed.

◼ The tissue bed should be lined witheither spilt thickness skin, fullthickness skin or pedical flap.

◼ Hair bearing flaps should beavoided, as the presence of hairprecludes the placement of implantand skin adhesive.

◼ The tragus however should beretain because this structure createsa less obvious anterior line ofjunction between the prosthesisand the skin.

Impression

◼ Impression of the defect side as well as impression of

a normal ear is necessary for making of wax pattern.

◼ The tissue bed is not displaceable in defect area. So

the distortion due to postural changes is less.

◼ Impression of the defect is taken in the supine

position of patient with the defect side up.

◼ Before impression:

1. Area is isolated with drape.

2. Ear canal is blocked with cotton.

3. Adjacent hair is covered by petroleum jelly.

◼ Impression of normal ear is done by

1. Presurgical impression.

2. By Donor technique.

3. By taking impression of other side and dividing

cast in equal section.

◼ A suitable impression material with good flow

properties is used. After material is set a layer

of backing of quick setting plaster will provide

suitable support for the impression.

◼ Now wax pattern is adapted and recontoured.

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◼ The entire must be stippledto match the skin texture ofthe patient. Stippling isnecessary.

1. For matching of prosthesis toadjacent skin.

2. For easy extrinsic tinting

3. For mechanical retention ofextrinsic colorants andlengthening the period of theservice of prosthesis.

◼ Now the margins arefeathered and the waxpattern is luted to the cast.

processing

◼ The wax ear is invested in a manner to construct a 3 part mold.

◼ Three part mold are necessary when using flexible materials, in order to remove the casting from the mold without tearing.

◼ Then the appropriate material is selected, base shade determined and the processing is completed.

Delivery and retention

◼ Besides the improvement of cosmetic additional benefits are derived from the prosthesis.

◼ As they help to support eyeglass frames and protect the ear canal from wind, dust & other particulate matter.

◼ Retention is accomplished by means of tissue adhesive or osseointegrated implants or by engaging bony or soft tissue undercuts.

Nasal Prosthesis

◼ The majority of nasal defects are secondary to

treatment of neoplasms, although occasionally

defects secondary to trauma are seen.

◼ In general, most partial nasal defects are best

restored surgically, whereas total nasal defects

are best restored prosthetically.

Surgical consideration

◼ When a total rhinectomy is contemplated, the nasal bones should be removed even though these structures may not be infilterated with tumor.

◼ If the nasal bone remain, the prosthesis must either terminate just above the superior surgical margin, disrupting concealment of the prosthetic margin, or extend superiorly over the nasal bridge.

◼ Retained nasal bone will dictate the prosthetic contours of the nasal tip, so the resultant prosthesis may then appear larger than normal, leading to an unpleasant esthetic.

◼ Care should be taken to avoid surgical displacement or distortion of the upper lip during resection & closure.

◼ During surgical resection of the tumor care should also be taken to avoid undue distortion of the cheeks and nasolabial folds. Obliteration or displacement of the nasolabial folds adversely affect the contour and position of the nostril and columella portion of the prosthesis.

◼ The nasal bone, alae, columella and the anterior portion of the nasal septum should be removed.

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impression

◼ As in orbital defects postural changes may result in distortion of the tissue bed, therefore it is advisable to obtain the master impression with the patient in an upright position.

◼ Elastic impression material that possess good flow properties are suitable.

◼ The nasal passage should be blocked with gauge to prevent entry of impression material.

sculpting

To be effective, the nasal prosthesis must reproduce the contour and texture of the resected nose. Another important factor is the placement & camouflage of the lines of juncture.

If a presugical facial cast has been fabricated, a wax duplicate of the nasal portion is adapted to the cast of the postsurgical defect.

If presurgical casts are not available, a mass of clay or wax is adapted to the cast of the defect and basic contours are completed. The patient will usually have numerous facial photograph, available for references.

◼ The alae should be located in their appropriate position in relationship to the nasolabial folds. By tucking a portion of the ala into the nasolabial fold, these margins can be made inconspicuous.

◼ The junction between columella & skin should be at a right angle or acute angle.

◼ As in auricular prosthesis, development of proper surface texture is also important , stippling is usually most prominent on the tip & nostril.

Processing and delivery of prosthesis

◼ The wax pattern is invested with appropriate mold material.

◼ Two piece molds are adequate.

◼ The wax pattern should be thinned internally to reduce wt. as well as to allow normal nasal air flow.

◼ When the prosthesis isprocessed it will be thin,flexible, and light in wt.,the basic shade of theprosthesis should closelymatch the lightest area ofcoloration in the localarea.

◼ Extrinsic colorationshould be applied withthe patient present andunder adequate lighting.

◼ Retention in theprosthesis is achievedwith adhesive,engagement of undercutsand with osseointegratedimplants.

Thank you

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IMPLANT LOADING

DR. SUDHIR MEENA

IntroductionPre-load and After-loadPhysiology of bone and loadingModeling and remodelingEarly functional loadingConsequences of biomechanical overloadEvolution of the concept of implant loading

Protocols of implant loadingElements of implant loadingImmediate occlusal loading Factors that decrease riskGuidelines for immediate loadingConclusionReferences

Prosthetic rehabilitation of missing structures in the oral and maxillofacial region in accordance with DeVan's principle of preservation has been the ultimate challenge to the prosthodontist. Over the years, traditional methods of tooth replacement are slowly and steadily being replaced by newer modalities like implants.

High success rates of implants and the advantages that go with them have earned them the name of the "third dentition".

Implants have come a long way from cast cobalt chromium tubes, pins, subperiosteal vitallium implants, endosseous blade implants, ceramic implants to the modern day root form implants made of titanium and its alloys.

Dental implants were commonly loaded at placement because immediate bone stimulation was considered to avoid crestal bone loss (Linkow & Chercheve 1970). Fibrous tissue interposition was considered the optimal response to implants as it was mimicking the natural periodontal ligament.

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In contrast to all other experimental studies of that time, Branemark et al (1969) showed that direct bone apposition at the implant surface was possible and lasting under loading at the condition that implants were left to heal in a submerged way.

The basis of the increasing popularity of dental implants is the coincidental discovery by Per-Ingvar Branemark and his co-workers of the tenacious affinity between living bone and titanium oxides, termed “Osseointegration”.

Success with Brànemark's protocol still has a deterring factor in the form of extended treatment period, which sometimes preclude patients from resorting to implant therapy. Increasing functional and aesthetic challenges have prompted implantologists to reduce the treatment period by loading the implant immediately at the time of placement.

The protocol has yielded encouraging results although they still need to match the time tested two-stage procedure, by way of success over an extended period of time.

The Immediate loading of dental implants clearly represents the change in dogma. To load the implant immediately or not to load is indeed the question today and the rationale that goes with the protocol which warrants discussion.

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The preloading or stretching the screw places the components under enough tension to create elongation of the material within its elastic limit. Preloading may reduce screw loosening.

As a result the components stretch and maintain fixation in spite of vibration and external forces. The elongation of metal is related to the modulus of elasticity, which is dependent on the type of material, its width, design, and the amount of stress applied per area.

Thus a gold screw exhibits greater elongation but lower yield strength than a screw made of titanium alloy. A prosthesis screw may exhibit a torsional ductile fracture at 16.5 N-cm Vs 40 N-cmfor an abutment screw of different material and size.

The material the screw is made from (eg. Titanium alloy or gold) has a specific modulus of elasticity. The plastic deformation or permanent distortion of the screw is the end point of the elasticity modulus. When the screw is stretched with a force 75% of its elastic length, it is able to better resist vibration and screw loosening.

In order to stretch the screw, a torque wrenchis necessary, although not completely accurate. Even an experienced clinician is unable to determine the amount of correct torque on the screw by tactile sense only.

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A screw may be described to permit more preload on the components.

The after-loading of implants is achieved by means of prosthesis brought into occlusion.

As a result of unique physiological mechanisms, bone serves two antagonistic functions:

structural support and calcium metabolism.

The strength of a bone (quantity, quality and distribution of osseous tissue) is directly related to loading.

As an energy conservation measure, bone that is not adequately loaded is resorbed, and the skeletal system continuously adapts to achieve optimal strength with minimal mass. The delicate structural balance is further challenged by metabolic function.

An adequate reserve of osseous tissue must be maintained to provide a continuous stream of ionic calcium without compromising structural integrity. To provide for a variety of conflicting demands, the skeleton has evolved structural and metabolic fractions.

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Osteopenia (inadequate bone mass) is a common clinical problem. It may be due to functional atrophy and/or negative calcium balance.

Prospective oral implant patients are likely to present with localized and systemic skeletal problems for three reasons:

Bone in edentulous areas is usually atrophic.

Metabolic bone disease is prevalent in middle-aged and older adults.

Integrated implants are often indicated for patients with a history of severe bone loss.

The clinical success and longevity of endosteal dental implants as load bearing abutments are controlled largely by the mechanical setting in which they function. The treatment plan is responsible for the design, number, and position of the implant.

Unique mechanisms of bone adaptation have evolved to maintain structural integrity, repair fatigue damage, and provide a continuous source of metabolic calcium.

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Modeling involves individual uncoupled sites of bone formation or resorption that change the shape or form of a bone. This is the principal mechanism for adapting osseous structure to functional loading.

Remodeling is the mechanism of bone turnover. It involves coupled sequences of cell activation (A), bone resorption (R) and bone formation (F). The duration of the ARFremodeling cycle (sigma) is about 4 months in humans.

Modeling is the principal means of skeletal adaptation to functional and therapeutic loads.Relatively modest changes in the distribution of osseous tissue along cortical bone surfaces can dramatically change the overall load bearing capability.

By a mechanism of focused bone resorption and formation events, trabeculae can form, reorient and change in size as a result of "micromodelling" to resist functional loads optimally.

A good example of this process is the networkof secondary tissues that forms in the marrow cavity to support an integrated fixture.

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Under most circumstances, cortical bone remodels at a rate of about 2-10% per year. Since only a portion of the cortex is in the metabolic fraction. The remodeling rate for cortical bone is usually 3-10 times less than for adjacent trabecular bone (metabolic fraction).

This complex interaction involves not only biomaterial and biocompatibility issues, but also the alteration of the mechanical environment that occurs when placement of an implant disturbs the normal physiologic distribution of forces, fluids, and cell communication.

In 1977, Branemark & coworkers published the first long-term follow up study on dental implants, thus providing the scientific foundation of today's implant treatment. The successful use of jaw bone anchored(osseointegrated) titanium dental implants to retain prosthetic constructions in the rehabilitation of the edentulous and partially edentulous patients has been well documented in several publications.

The original two-stage surgical protocol using a two-piece implant pillar was applied. The main reasons for this approach have been to ❖Minimize the risk of infection❖Prevent apical down growth of mucosal epithelium, and ❖Minimize the risk of undue early loading during the initial healing period.

In addition, a stress-free healing period of 3 to 6 months before the mucosa piercing abutments are placed and the supra-construction is connected to the implants was emphasized to predict a successful treatment outcome. Such a stress free period was even considered to be an ultimate prerequisite to achieve proper osseointegration.

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In other words, early stress on the implants was thought to jeopardize the osseointegration process.

Over the years, however, the high level of predictability in implant therapy has resulted in a re-evaluation of the original Branemark protocol for implant placement. Schroeder & coworkers were the first to show the possibility to achieve demonstrated successful clinical treatment outcome using the one stage surgical protocol with the Branemark system.

Similar successful clinical treatment outcomes, in the edentulous as well as the partially edentulous situation, have been reported using one-piece implants (ITI, Straumann) placed according to the original one-stage surgical protocol.

In several clinical studies the original dentures most often were adjusted and relined by a soft tissue conditioner 10 to 12 days following implant placement to minimize unfavorable functional loading, i.e., undue early loading. However, it has to be anticipated that implants placed according to a one-stage surgical procedure to some extent will be directly and unpredictably loaded during function in the initial healing period via the adjusted and relined denture.

Furthermore, such loading might be unfavorable for the implants, as the deformation pattern of complete denture base material would cause micromovements. In other words, "an initial and direct loading of implants piercing the mucosa via the adjusted and relined denture obviously does not jeopardize a proper osseointegration of the fixtures".

Such a statement is in agreement with clinical observations reported by Henry & Rosenberg, who concluded that “controlled immediate

loading” of adequately installed, non-submerged implants, by reinsertion of a modified denture, does not appear to jeopardize the process of osseointegration in the anterior mandible.

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" Similar observations were reported by Cooper et al. Furthermore, Becker et alconcluded that" one-step Branemark implants may be considered a viable alternative to two-step implants."

In former days, it was postulated "too-early loading of an implant leads to interfacial formation of fibrous tissue instead of bone". Others claimed "controlled immediate loading does not appear to jeopardize the process of osseointegration". Today's knowledge indicates that the degree of micromotion at the bone-implant interface during the initial healing phase and it may be not premature loading.

Premature loading leads to implant

movement

The end result “Soft tissue

interface”

“Bony interface”

As favorable loading conditions of tooth abutments are obtained via a rigid fixedappliance, it is reasonable to believe that successful treatment outcomes can be reached also when rigid fixed supraconstructions are connected to implants soon after implant placement.

To reduce the period during which the individual implants are exposed to direct and unpredictable loading, splinting of the individual implants through a rigid fixed device will most certainly decrease the micromotion at the bone-implant interface, thus facilitating proper bone healing (osseointegration).

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Based on the available information, Randow et albelieved it to be of interest to compare the rehabilitation of edentulous mandibles by fixed supraconstructions connected to implants placed according to either an early loaded onestage surgical procedure or the original two-stage concept, with the working hypothesis that there are no differencesbetween the two methods concerning the treatment outcome.

A total of 88 implants (16 patients) were placed according to the one-stage protocol and loaded via a fixed appliance within 20 days. The implants placed according to the original protocol were loaded about 4 months following placement. At the time of delivery of the fixed appliances, all patients were radiographically examined, an examination that was repeated at the 18-month follow-up.

The analysis of the radiographs revealed that during the 18-month observation period the mean loss of bone support amounted to about 0.5 mm around the implants, irrespective of early loading. All implants were at all observation intervals found to be clinically stable.

The authors concluded that it is “possible to

successfully load titanium dental implants immediately following installation via a permanent fixed rigid cross-arch supraconstruction”. However, such a treatment approach has so far to be strictly limited to the inter-foramina area of the edentulous mandible.

Schnitman and coworkers reported on 63Branemark implants placed in 10 patients. Of these 63 implants, 28 were placed and "immediately loaded to support an interim fixed bridge." The remaining 35 implants were placed according to the 'original two-stage protocol, osseointegrated properly, and are still in function. Of the 28 implants immediately loaded, four failed.

In other words, the survival rate for the immediately loaded implants was found to be about 85%.

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➢Early implant failure ➢Early crestal bone loss ➢Intermediate to late implant failure ➢Intermediate to late implant bone loss ➢Screw loosening (abutment and prosthesis coping) ➢Uncemented restoration ➢Component fracture ➢Porcelain fracture ➢Prosthesis fracture➢Periimplant disease (from bone loss)

The surgical and prosthetic protocols for the development of a predictable direct bone-to-implant interface with root-form implants were developed and reported by Branemark et al.

About 25 years ago, Branemark et al (1977) published the first long-term follow-up on oral implant, providing the scientific foundation of modern dental implantology. The predictability of implant integration according to Branemark and collaborators was obtained by adherence to a strict surgical and prosthodontic protocol. One of the most emphasized requirements was a stress-free healing period of 3-6 months, making implant treatment lengthy.

Presently however, early and immediate loading protocols are reported by an enhancing number of clinical (Chiapasco et al 1997, Schnitman et al 1997, Tarnow et al1997) and experimental publications.

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Following their 10-year clinical experience, recommendations ensuring durable osseointegration of dental implants were set.

The most important were:

➢ Use of sterile conditions as "in a fully equipped operatory"

➢ Use a mucobuccal incision and avoid a crestal one➢ Use of an atraumatic surgery involving low-speed

drilling➢ Use of a biocompatible material i.e. titanium ➢ Use of titanium ancillary➢ Use of a 2-stage procedure➢ Use of a stress-free healing period of 3-6 months before

loading➢ Avoid X-radiographs before the end of the healing

period➢ Use of acrylic occlusal contact surfaces

Early loading was identified as a detrimental factor for osseointegration' by Branemark et al During 'the course of their clinical trial (Branemark et al 1977). BUT TODAY THE SCENARIO HAS CAHNGED TO LOADING AND IMMEDIATE LOADING.

Brànemark's loading protocol

Flush with bone level, cover with gingiva.

Final prosthesis after 3 to 6 months of initial healing.

Soft/ hard diet.

Progressive loading

Flush with bone level, covered with gingiva.

Provisional prosthesis brought progressively into occlusion, depending upon bone density.

Soft/ hard diet.

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Non submerged single stage protocolNon-submerged implants, flush within 1-2 mm of gingival level

Soft diet

Immediate functional loadingTemporary restoration fitted on the same day as surgery, in occlusion

Soft diet

Immediate non-functional loadingTemporary restoration fitted on the same day as surgery, not in occlusionSoft diet

Early loadingFinal crowns within 3 weeks from surgery, in occlusionSoft/ hard diet

Delayed loadingImplant subjected to loading after more than 6 weeks post surgerySoft/ hard diet

Anticipated loadingProvisional prosthesis is fitted after about 2 months after surgerySoft/ hard diet

➢Time interval

➢Diet

➢Occlusal material

➢Occlusal contacts

➢Prosthesis design

The masticatory force for soft food is about 10 psi. This diet not only minimizes the masticatory force on the implants but also decreases the risk of temporary restoration fracture or partially decemented restoration. Either of these consequences can overload an implant and cause unwanted complications.

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The diet protocol should not be overlooked during the restorative procedure because most dentists have observed the fracture of acrylic prostheses with harder foods and greater occurrence of decemented restorations when they ignore type of diet during the transitional prosthesis stages.

After the initial delivery of the final prosthesis, the patient may include meat in the diet, which requires, about 21 psi in bite force. The final restoration can bear the greater force without risk or fracture or decementation.

After the final evaluation appointment, the patient may include raw vegetables, which require an average 27 psi of force. A normal diet is permitted only evaluation of the final prosthesis function, occlusion, and proper cementation.

Occlusal material:

The occlusal material may be varied to load the bone-to-implant interface gradually. During the initial steps, the implant has no occlusal material over it. At subsequent appointments, the dentist chooses acrylic as the occlusal material, with the benefit of a lower implant force than metal or porcelain.

Either metal or porcelain can be used as the final occlusal material. If para function or cantilever length cause concern relative to the amount of force on the early implant bone interface, the dentist may extend the softer diet and acrylic restoration phase for several months. In this way, the bone has a longer time to mineralize and organize to accommodate the higher forces.

Occlusion:

The dentist gradually intensifies the occlusal contacts during prosthesis fabrication. No occlusal contacts are permitted during initial healing. The first transitional prosthesis is left out of occlusion in partially edentulous patients.

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The occlusal contacts then are similar to those of the final restoration for areas supported by implants. The occlusal contacts of the final restoration follow the implant-protective occlusion concepts.

Prosthesis design:

During initial healing, the dentist attempts to avoid any load on the implants, including soft tissue loads. The first transitional acrylic restoration in partially edentulous patients has no occlusal contacts.

Its purpose is to splint the implants together, to reduce stress by the mechanical advantage, and to have implants sustain masticatory forces solely from chewing. In the second acrylic transitional restoration, occlusal contacts are placed on the implants with occlusal tables similar to the final restoration but with no cantilevers in nonesthetic regions

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Immediate functional loading protocol

Clinical trials successful osseointegration

(95-100% success rate- Completely edentulous patients)

✓ Bone quality is good

✓Functional forces are controlled

✓More favourable in mandible compared to maxilla

Over loading – Stress concentration, undermining bone resorption without apposition (Branemark 1984)

The other protocol for immediate occlusal loading of dental implants initially loads all of the implants inserted. The implants are splinted together, which decreases the stresses on all the developing interfaces and increases the stability, retention, and strength of the transitional prosthesis during the initial haling phase.

Often additional implants also are used with this technique compared with the traditional healing method.

The immediate load concept provides all the advantages of the one-stage surgical approach. In addition, implants are splinted together, which decreases the risk of overload because of a greatersurface area and improved biomechanical distribution.

Over the last few years, authors have reported on immediate loading in the completely edentulous patient, with 95% to 100% success rates.

However, the influence of immediate loading on crestal bone loss has few animal and clinical reports so as to compare the differences of immediate loading to a more traditional bone healing time with no functional load.

High success rates from immediately loaded implants in humans were first documented in the middle 1980s, when the 1-stage implant protocol gained popularity.

Babbush et al (1986) reported a cumulative success rate of 88% on 1739 immediately loading TPS implants. Subsequently, many authors have shown the possibility of loading implants immediately.

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Bone Microstrain:

Loaded bone changes its shape. This change may be measured as strain. Microstrain conditions 100 times less than the ultimate strength of bone may trigger a cellular response. Frost has developed a microstrain language for bone based on its biological response at different microstrain levels. Bone fractures at 10,000 to 20,000 microstrain units.

However, at levels of 20% to 40% of this value, bone already starts to disappear or form fibrous tissue and is called the pathologic overload zone. The ideal microstrain for bone is called the physiologic or adapted zone. The remodeling rate of the bone in the jaws of a dentate canine or human being that is in the physiologic zone is about 40% each year.

At these levels of strain the bone is allowed to remodel and remain as an organized, mineralized lamellar structure. This is called the ideal load-bearing zone for an implant interface. The mild overload zone corresponds to an intermediate level of microstrain between the ideal load bearing zone and pathologic overload. In this strain region, bone begins a healing process to repair micro fractures, which are often caused by fatigue. Histologically, the bone in this range is called reactive woven bone.

Rather than the surgical trauma causing this accelerated bone repair, the microstrain causes the trauma from overload. In either condition, the bone is less mineralized, less organized, weaker, and has a lower modulus of elasticity.

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One goal for an immediately loaded implant/prosthesis system is to decrease the risk of occlusal overload and its resultant increase in the remodeling rate of bone. Under these conditions the surgical regional acceleratory phenomenon may replace the bone interface without the additional risk of biomechanical overload.

When strain is placed on the horizontal axis and stress is positioned on the vertical axis, the relationship between these two mechanical indexes results in the flexibilities or modulus of elasticity of a material. Hence the modulus conveys the amount of deformation in a material (strain) for a given load (stress) level.

The lower the stress applied to the bone (force divided by the functional surface area that receives the load), the lower the microstrain in the bone. Therefore one method to decrease microstrain and the remodeling rate in bone is to provide conditions that increase functional surface area to the implant-bone interface.

The surface area of load may be increased in a number of ways:

implant number, implant size,implant design, and implant body surface conditions.

The force to the prosthesis also is related to the strain and may be altered in magnitude, duration, direction, or type. Methods that affect the amount of force include patient conditions; implant position, and direction of occlusal load.

Increase Surface Area:Implant number: The dentist may increase the functional surface are of occlusal load at an implant interface by increasing implant number. Hence rather than three to five implants to support a fixed restoration, use of additional implants when immediate loading is planned is more prudent. Immediate loading reports in the literature with the lowest percentage survival correspond to fewer implants loaded.

More implants typically are used in the maxilla (8 to 12) compared with the mandible (5 to 9). This approach helps compensate for the less dense bone and increased directions of force often found in the upper arch.

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Implant size:

The dentist also may increase the surface area of implant support by the size of the implant. The length of the implant in most systems increases in increments of 2 to 4mm. Each 3 mm increase in length can improve surface area support by more than 20%. However, the benefit of increased length is not found at the crestal bone interface but rather in initial stability of the bone-implant interface.

Implant body design:

The implant body design should be more specific for immediate loading because the bone has not had time to grow into recesses or undercuts in the design or attach to a surface condition before the application of occlusal load. For example, a press-fit implant with a cylinder design does not have bone integration the day of implant placement.

An implant body with a series of horizontal plates that is tapped or pressed into place does not have bone present between the plates the day of surgical placement. Macrospheres on an implant surface do not have bone present within or around the porous surface of the implant the day of implant placement.

For a threaded implant, bone is present in the depth of the threads form the day of insertion. Therefore the functional surface area is greater during the immediate load format. The number of the threads also affects the amount of area available to resist the forces during immediate loading.

The greater the number of threads, the greater the functional surface area at the time of immediate loading. Some threaded implants have a 1.5 mm distance between the threads (e.g., BioHorizons dental implants). The smaller the distance between the threads, the greater the thread number and corresponding surface area.

Implant thread design may affect the bone turnover rate (remodeling rate) during occlusal load conditions. For a V-shaped thread design, a 10 times greater shear force is applied to bone compared with a square thread shape. Bone is strongest to compression and weakest to shear loading. Compressive forces decrease the microstrain to bone compared with shear forces.

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Hence the thread shape and implant design may decrease the early risks of immediate loading while the bone is repairing the surgical trauma.

Implant design affects functional surface area more than implant size. A larger-diameter cylinder implant has less surface area than a smaller-diameter threaded implant. As a result, thread implants present considerable advantages compared with pres-fit implants for immediate load protocols because their design features do not require histologic integration to resist loads and they have greater surface are to resist occlusal forces.

A tapered implant design presents some disadvantages for immediate load applications. When the tapered osteotomy is prepared using tapered drills, the implant does not engage the bone physically until the implant is seated almost completely into the bone site. This reduces the initial fixation. In addition, the tapered implant has less overall surface areas compared with a parallel-walled, threaded implant.

However, few clinical trials have compared immediate loading with different implant thread design and tapered implant bodies in the completely edentulous patient. The short-term clinical reports indicate a high success rate, regardless of implant design. As a result, overall shape and thread geometry apparently may not be the most important aspect for immediate occlusal load survival. Implant number, implant position, and patient factors most likely are more relevant components of success. Future studies in this area certainly are needed.

Implant surface conditions:

Implant surface conditions may affect the rate of bone contact, lamellar bone formation, and the percentage of bone contact. The surface condition that allows bone formation in greatest percentage, higher bone-implant contact percentage with higher mineralization rate, and fastest lamellar bone formation would be of benefit in immediate loading. These factors have been noted in delayed and immediate loading environments with hydroxyapatite coatings.

Implant design and surface condition are independent issues that use a different mechanism to reduce the risk of overloading. For example, a hydroxyapatite surface may be applied to a cylinder or a threaded implant. The thread design would be more beneficial to an immediate load application.

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Yet the hydroxyapatite or roughened surface also may be of benefit during the following healing period, especially at the 3 to 5 weekswhen the bone is weakest. The majority of clinical studies have been made with threaded implant designs.

Surface conditions are more difficult to ascertain in the literature and have included a smooth machined surface, a roughened titanium plasma spray surface, and a hydroxyapatite surface condition without a clear deference in clinical survival. However, evidence is increasing that the machine surface condition is inferior in softer bone types.

Decreased Force Conditions:

The dentist may evaluate forces by magnitude, duration, duration, and type. The dentist should reduce conditions that magnify the noxious effects of these forces.

Patient factors:

The greater the occlusal force applied to the prosthesis. The greater the stress at the implant-bone interface and the greater the strain to the bone. Therefore force conditions that increase occlusal load increase the risks of immediate loading. Parafunction such as bruxism and clenching represents significant force factors because magnitude of the force is increased, the duration of the force is increased, and the direction of the force is more horizontal than axial to the implants with a greater shear component.

Occlusal load direction:

The occlusal load direction may affect the remodeling rate. An axial load to an implant body maintains more lamellar bone and has a lower remodeling rate compared with an implant with an offset load..

Therefore one should eliminate posterior cantilevers in the immediate-load transitional restoration because they magnify the detrimental effects of force direction.

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Implant position:

Dental implants have been used widely to retain and support cross-arch fixed partial dentures. Implant position is often as important as implants supporting three teeth is often as important as implant number. For example, elimination of cantilevers on two implants supporting three teeth is recommended, rather than positioning the implants next to each other with a cantilever.

The cross-arch splint forming an arch is an effective design to reduce stress to the entire implant support system. Hence the splinted arch position concept for the completely edentulous is advantageous for the immediate-load transitional prosthesis.

Implant position is one of the more important factors in immediate loading for completely edentulous patients. The mandible may be divided into three sections around the arch:

the canine-to-canine area

and the bilateral posterior sections.

The maxilla requires more implant support than the mandible because the bone is less dense and the direction of force is outside of the arch and the force is outside of the arch in all the eccentric movements. The maxilla is divided into at least four to five sections, depending on the intensity of the force conditions and the shape of the arch.

The minimum four sections are the bilateral canine area and the bilateral posterior regions. When force factors are greater, the regions of the maxilla are increase to five and include the incisor area. At least one implant should be inserted into each maxillary section and splinted together during the immediate-loading process.

Concerns have been raised regarding cross-arch splinting in the mandible because of mandibular flexure and torsion distal to the mental foramens. Clinical reports indicate the acrylic used in the transitional prosthesis is flexible enough to alleviate these concerns. However, the final restoration should be fabricated in at least two independent sections when implants are placed in both posterior quadrants.

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Mechanical properties of bone:

The modulus of elasticity is related to bone quality. The less dense the bone, the lower the modulus. The amount of bone-implant contact is also less for less-dense bone. The strength of the bone also is related directly to the density of the bone.

The softer the bone, the weaker the bone trabeculae. In addition, the remodeling rate of cortical bone is slower than that of trabecular bone. As such, the cortical bone is more likely to remain lamellar in structure during the immediate loading process compared with trabecular bone.

Bone grafting must depend on several factors to be predictable. Adequate blood supply and a lack of micromovement are two important conditions. The developing bone is woven bone and more at risk of overload. The bone graft in the region of the implant body may lead to less fixation and lower initial bone-implant contact percentages. Bone augmentation is more predictable when soft tissue completely covers the graft (and membranes when present).

All of these conditions make bone grafting, implant insertion, and immediate loading more at risk. Therefore the suggestion is that implants that are immediately loaded be placed in an existing bone volume adequate for early loading and the overall proper prosthetic design. Bone grafting, before implant placement and immediate loading, is suggested when inadequate bone volume is present for proper reconstructive procedures.

In cases where early loading is deemed appropriate, Tarnowhas suggested a set of guidelines to help achieve clinical success:

Immediate loading should be attempted in edentulous arches only to create cross-arch stability.

Implants should be at least 10 mm long.

A diagnostic wax-up should be used for template and provisional restoration fabrication.

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A rigid metal casting should be used where possible.

A screw-retained provisional restoration should be used where possible.

If cemented, the provisional restoration should not he removed during the 4- to 6-month healing period.

All implants should be evaluated with Periotest (a measure of the degree of resistance to perpendicular force) at stage 1, and the implants that show the least mobility should be utilized to provide resistance to rotational forces.

The widest possible anterior- posterior distribution of implants should be utilized to provide resistance to rotational forces. Cantilevers should be avoided in the provisional restorations.

The emergence of a 1-stage early loading protocol does not imply that submersion is no longer necessary, but rather suggests that is not always essential. The 2-stage procedure remains the treatment of choice. However, under the right circumstances successful early loading can reduce the length of prosthetic rehabilitation.

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Success criteria of implants

Schuitman and Schulman criteria (1979)

1) The mobility of the implant must be less than 1mm whentested clinically.

2) There must be no evidence of radiolucency

3) Bone loss should be less than 1/3rd of the height of theimplant

4) There should be an absence of infection, damage to structureor violation of body cavity, inflammation present must beamneable to treatment.

5) The success rate must be 75% or more after 5 years offunctional service.

Albrektson and Zarb G (1980)

1) The individual unattached implant should be immobile whentested clinically

2) The radiographic evaluation should not show any peri - implantradiolucency

3) Vertical bone loss around the fixtures should be less than0.2mm annually after first year of implant loading.

4) The implant should not show any sign and symptom of pain,infection, neuropathies, parastehsia, violation of mandibularcanal and sinus drainage.

5) Success rate of 85% at the end of 5 year observation period and80% at the end of 10 year service.

6) Implant design allow the restoration satisfactory to patient anddentist. - Smith and Zarb (1989)

The patient demand for esthetics is increasing day by day and the replacement of teeth immediately following extraction is attaining popularity. In this respect even the replacement of teeth immediately following the implant placement has to be considered as a serious issue. Therefore it is very much essential to know the requirements and bone responses to the occlusal loading in the healing period. Also the modifications in treatment plan to achieve the success of restoration are necessary.

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Carl E Misch: Contemporary Implant Dentistry.

Sumiya Hobo: Osseointegration and Occlusal Rehabilitation.

W E Roberts: Fundamental principles of bone physiology, metabolism and loading.

Osseointegration in clinical dentistry – Branemark, Zarb,Albrektsson

Endosseous implants for Maxillofacial reconstruction – Blockand Kent

Implants in Dentistry –Block and Kent

Dental and Maxillofacial Implantology – John. A. Hobkrik,Roger Watson

DCNA, 1986 vol. 30:151-174Int J Oral Surg, 1981 vol. 10: 387-416Int J Oral Maxillofac Implants, 1991 vol. 6: 405-412Clin Oral Impl Res, 2000 vol.11: 12-25Clin Oral Impl Res, 2003 vol.14: 515-527Int J Oral Maxillofac Implants, 2003 vol. 18: 250-257 Int J Oral Maxillofac Implants, 2002 vol. 17: 353-362Int J Oral Maxillofac Implants, 2003 vol. 18: 512-522Int J Oral Maxillofac Implants, 2003 vol. 18: 523-530J Periodontol, 1997 vol. 68: 591 597

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Management of

severely resorbed

mandibular ridgeDr. SUDHIR MEENA

Department of Prosthodontics Including Crown & Bridge, Maxillofacial Prosthodontics & Oral Implantology

Contents ◼ Introduction

◼ Etiology of ridge resorption

◼ Atwood’s Classification of resorbed ridge

◼ Management-

Surgical (pre-prosthetic surgery)

Surgical-prosthetic (implants)

Prosthetic (conventional complete denture procedure with modifications)

◼ Use of aids:

Springs

Suction chambers and disks

Magnets

Denture adhesives, liquid supported dentures.

◼ Patient’s education

◼ Conclusion

Introduction

In prosthetic sense, bone is considered to

be the base which provides support for

dentures. In the physiological sense, it is an area

where forces created while biting and chewing

foods are transmitted.

In the course of life continuous bone rebuilding occurs. Bone loss is considered to commence in humans at 35-40 yrs of age, after peak bone mass has been achieved, and the atrophic processes then continue with varying intensity.

According to Atwood, the degree of

mandibular loss of its alveolar portion is 3-4

times higher than alveolar resorption in the

maxilla, which is due to a smaller denture-

bearing area in the mandible and thus a greater

load per square cm.

Reduction of residual ridges

◼ Residual ridge resorption after loss of teeth is a

multifactorial oral problem.

◼ Loss of alveolar bone from the edentulous jaws

is a serious and common clinical problem,

especially among the elderly.

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The retention and stability of dentures are reduced,

but little is known about the pathogenesis of this bone

loss.

The existing data suggest that either local factors,

for instance occlusal trauma, or systemic factors such as

postmenopausal osteoporosis, contribute to edentulous

alveolar bone resorption.

Etiology of ridge

resorption

A) Anatomic factors

B) Mechanical factors

C) Systemic factors

A) Anatomic factors:

◼ Ridge resorption varies with-

➢ Quantity and Quality of the bone.

➢ Shape& Form of the ridges (Large, well-rounded ridges and broad palates would seem to be favorable anatomic factors)

➢ Density of the ridge (density at any given moment does not signify the current, metabolic activity of the bone and bone can be resorbed by osteoclastic activity regardless of its degree of calcification)

B) Metabolic factors

◼ Ridge resorption varies directly with some systemic or localized bone resorptive factors and inversely with some bone formation factors.

◼ Some local biochemical factors in relation to periodontal disease which affects the ridge resorption-

✓ Endotoxins from dental plaque on unclear dentures.

✓ Osteoclast activating factor (OAF).

✓ Prostaglandins.

✓ Human gingival bone resorption stimulating factors.

✓ Heparin acts as a cofactor in bone resorption which is produced from most cells, which are found close to bone margins.

◼ Systemic factors influence the balance between the normal bone formation and bone resorption. These factors create a natural resistance to unfavorable local factors. They are-

◼ Estrogen.

◼ Thyroxin.

◼ Growth hormone.

◼ Androgens.

◼ Calcium.

◼ Phosphorus.

◼ Vitamin D.

◼ Protein.

◼ Fluoride.

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Mechanical factors

◼ It is clear that, bone that is used as by regular

physical activity will tend to strengthen within

certain limits while bone that is in ‘disuse’ will

tend to atrophy.

◼ In considering force, following factors should be considered, which directly affects the amount of resorption-

❖ Amount of force.

❖ Frequency of force.

❖ Direction of force.

❖ Force per unit area.

❖ Damping effect of the underlying tissue.

Classification of residual ridge

◼ In order to provide a simplified method for categorizing the most common residual ridge configurations,Atwood (1963) described a system of six orders of residual ridge-

Order I – Pre extraction.

Order II – Post extraction.

Order III – High well rounded.

Order IV – Knife edge.

Order V – Low, well rounded.

Order VI – Depressed.

Management

◼ MM Devan’s statement: Our aim in

prosthodontics should be perpetual preservation

of what remains than meticulous restoration of

what is missing.

◼ The requirement of managing severely resorbed

alveolar ridge of mandible is important for two

reasons:

The problem of retention and stability.

Pain and discomfort.

◼ Management of severely resorbed residual

ridges has been divided into:

I. Surgical management.

II. Prosthetic & Surgical management.

III. Prosthetic management.

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I) Techniques to correct alveolar atrophy:

a) Direct augmentation of superior border of mandible.

b) Augmentation of inferior border of mandible.

c) Augmentation of mandibular ridge with pedicle or interpositional bone

grafts.

d) Augmentation with combined vertical and horizontal osteotomics.

e) Augmentation with synthetic graft materials.

f) Distraction osteogenesis.

II) Techniques to compensate for alveolar atrophy:

a) Vestibuloplasty.

b) Lowering of mental foramen.

c) High frenum attachment (frenectomy).

A) Surgical management: B) Surgical and Prosthetic management:

◼ Implants: Implants have revolutionized treatment of the edentulous patient. Conventional use of implants and a whole array of new procedure including bone grafting or osteotomies in conjunction with implants are giving the restorative dentist, surgeon, and patient more options of obtaining optimal restorative result.

◼ The common types of implants are:

a) Endosteal implants.

b) Sub-periosteal implants.

c) Mucosal inserts.

d) Mandibular staple implants.

C) Prosthetic management:

Metal supported denture

Fluid filled denture

Thick bordered denture

Hollow denture

Multiple suction-disc denture

Management :

◼ Case history.

◼ Clinical examination.

◼ Treatment planning.

Case-History:

◼ Prior to denture construction, a accurate medical

history should be taken. On identification of any

systemic factors appropriate medical advice should be

sought to clarify the prognosis.

◼ Problems of emotional nature in addition to ridge

resorption may also prevent a satisfactory result.

◼ A comprehensive dental history including-

previous prosthetic treatment

number of old dentures made

frequency of denture rebasing should be appreciated in

order to estimate both the apparent rate of progression

of RRR and the capability of the individual to cope up

with previous denture.

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◼ Intra-oral examination should determined the ridge form and extent of resorption. Mucosal form on and surrounding the ridge should be made along with palpation to locate any tender areas of mucosa.

◼ The assessment of quantity, quality, viscosity of the

saliva should be made. This may affect ‘physical

retention of the denture associated with the cohesive

and adhesive properties of saliva between the denture

and mucosa.

CLINICAL EXAMINATION:

◼ The tongue size and tongue movements should be assessed.

◼ Radiographs should also be taken which aids in assessing ridge resorption. Inadequate bone thickness(risk of spontaneous fracture). The position of the mental nerve and mandibular canal can also be established.

◼ Diagnostic models may also be taken to allow case evaluation in the absence of the patient.

Treatment planning

◼ According to the detailed case history, examination

(local & systemic) and with special considerations

following steps are to be followed:

Impression making (initial & final).

Recording of jaw relation.

Occlusion scheme selection, followed by teeth

selection.

Fabrication of the prosthesis.

Impression making:

◼ In severely resorbed ridges, the ridges will be compromised. There are different impression techniques to follow. The principles employed in impression making should be maximal support, retention and stability.

◼ A broad area coverage with maximal denture

base extension decreases the force experienced

per unit area of the mucosa beneath the denture

and the likelihood of its trauma. However, in

resorbed ridge the extension of the base is

critical to avoid interferences with the

movement of border structure.

◼ Special techniques, to determine accurately the denture border extension have been evolved-

Fish (1932) recommended a technique where, sublingual fold space, extending from premolar to premolar region on each side was recorded. This horizontal flange acted as ‘tongue rest’ thereby increasing the stability and support.

Brill (1967) sought to gain facial and border seal by adapting an existing denture with a viscoelastic gel to eliminate space between the cheek tongue and the denture border and contour.

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Boucher (1958) made use of retromylohyoid fossa by extension of the distolingual flange across the mylohyoid muscle and ridge. This technique was also recommended by Nairn (1964).

In selective pressure technique, Boucher gave extra relief while taking impression for the areas which are unable to take load and distributemore to the primary stress bearing areas like mandibular buccal shelf area.

Dynamic Impression Methods:

Its significance:

Avoids the dislocating effect of the muscles on improperly formed denture border.

Complete utilization of the possibilities of active and passive tissue fixation of the denture.

Dynamic impressions in contrast to non dynamic impression records the tissues in an immobile condition, and

Semi dynamic impressions in which the denture borders are determined by partly passive and partly active movements as described by Fournet and Tuller.

Dynamic Impression Techniques by

Momme in 1872:

1) Fabrication of the special tray is done.

2) A ridge of self curing resin is built up in the premolar molar region on each side to support the thermoplastic material.

3) While the thermoplastic material is soft the tray is placed in position on the lower ridge in the mouth and the patient is asked to close the jaws slowly. The upper residual ridge will form an impression in the soft thermoplastic material at a height corresponding to the rest mandible. Tray is removed from mouth and cooled.

4) Lingually the mandibular rests should be concave to provide space for the tongue.

5) An irreversible hydrocolloid is used with 50% extra water sufficient amount of material to cover all tissues is placed directly into the mouth. The tray is pressed through alginate by digital force until the stops are firmly seated on the residual ridge. Then, the patient is asked to close his mouth slowly until the mandibular rests have obtained firm contact with the maxillae.

6) The patient should swallow three to four times at 10 seconds interval while the final impression material is still in a moldable condition. The action of the muscles that function in deglutition is accentuated because the mandibular rests prevent the mandible from reaching the vertical, relation of occlusion and force it to remain in its rest position. This procedure develops a registration of the denture space which ordinarily results in a proper extension of the lingual flanges of the finished dentures. Forceful protrusion of the lips brings the mentalis and orbicularis oris muscles into action and is responsible for forming the labial part of the impression.

7) In another method, an old denture can be used for a dynamic impression when opposing natural or artificial teeth are present. Often the vertical dimension at occlusion is decreased hence steps are placed at re-established height. The mandibular rests are built up include the inter-occlusal distance.

8) In still another method, denture is processed in a conventional manner. Then a correcting dynamic impression is made in the denture base to reshape and complete the final design and the denture is relined. This procedure was originally indicated by Momme in 1872.

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Dynamic impression technique by Russell and

Lench in 1934:

◼ This technique is used for flat mandibular ridges. This technique involves the use of tissue conditioning material. The powder consists of PMMA. The liquid is an aromatic ester in ethyl alcohol.

◼ A preliminary impression is made Resin tray is made on the cast. Border molding is done. Occlusal rim is adjusted to the corrected vertical dimension. The borders are reduced around 2-3mm. Now, either open mouth or closed mouth method using conditioning material.

◼ In general three applications of conditioning materials are used-

◼ I application- more viscous material is applied and allowed to remain in the mouth for 3-10 mins. Various movements of lips, cheeks, tongue are directed. The impression is removed rinsed and checked. Pressure areas are corrected.

◼ II application- same viscous material is applied and placed in mouth.

◼ III application- is the final wash and is made with relatively light bodied material.

◼ The end result is an impression that has a tissue placing effect, very thick and conforming, buccal borders and a relatively thick lingual and sublingual crescent area. This results in improved retention of the mandibular denture.

◼ Klein in 1957, suggested three distinct types of

impression techniques for mandibular dentures

depending on the type of foundation.

First condition-◼ When the mandibular ridge is almost completely resorbed with

just a rib of soft fibrous tissue along the crest. This rib of tissue is easily displaced and can be a constant source of irritation, if

the impression is not recorded correctly.

◼ After a routine modeling compound wax, mandibular impression is made in the usual manner approximately 3mm of compound is relieved over the crest of the ridge and a cast is poured. The clear acrylic resin tray processed on the preliminary cast will not contact the ridge crest. Three holes are drilled in the tray on each side in the areas of the ridge crest to prevent a building up of undesired pressure. The final impression is made inside the tray and the free flowing paste will allow the soft tissue along the crest of the ridge to place itself.

Second condition-

◼ In cases with almost complete resorption and with a spiny ridge of dense bony tissue along the crest of the residual ridge.

❖ Compound impression is made as above. In addition to the crest of ridge, compound is scraped away along the crest of mylohyoid ridge and posterior lingual flange to a depth of 2mm. Physiologic wax is added and primary impression completed. The cast is poured and the area of the mylohyoid ridge is relieved with 0.001 inch tin foil. The clear acrylic resin tray is made and final wash impression made. Master cast is poured. The knife edged ridge crest is again relieved with 0.001 inch tin foil. Thus forces of mastication will be exerted along the sides of the ridge rather than on the crest.

Third condition-

◼ In cases where ridge is flat or concave.

◼ The impression of lingual border is recorded accurately with the impression wax. Rest of the technique is same as stated above.

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Functional impression for the

mandibular complete denture

◼ A technique for producing a preliminary impression

of a resorbed edentulous mandibular ridge –

i. 2-mm metal wire is adapted to the curve of the

mandibular arch.

ii. A high-viscosity impression material is then formed

to the wire and placed in the patient's mouth.

iii. Speech movements are used to functionally shape

the material.

Aiche A. Int J Prosthodont. 1989 Nov-Dec;2(6):543-8 iv) Following polymerization, additional material is

added to create extensions not captured in the first

impression.

v) A final wash using a low-viscosity silicone or

polysulfide rubber material completes the impression.

The resultant preliminary impression has the advantage of

not being distorted by an ill-fitting stock tray or

artificially manipulated by the clinician

Jaw relation

◼ The physiological rest position of the mandible should

be ascertained accurately.

◼ In this position- the lateral borders of the tongue are generally

in contact with the teeth close to the occlusal surfaces and the

dorsum of the tongue contacts the hard and soft palate. This is

the starting position of the tongue when chewing. From this

position the tongue manipulates the food and keeps it positioned

between the teeth.

◼ The following considerations should be taken while recording jaw relations in cases of resorbed ridges-

The permanent base is of choice.

The occlusal plane of the lower denture should be such that at rest, the lateral borders of the tongue should touch the occlusal surfaces of lower rim.

Reducing the vertical dimension to some extent may be

advantageous (at the cost of lower denture) as this

reduces

◼ Forces of mastication.

◼ Decreased leverage action of the denture. Thus more

stability (Watt and MAC Gregor 1976) can be

achieved

Teeth selection

◼ Semi anatomic teeth are used where possible. The number of teeth can be reduced to decrease the pressure on the lower ridge.

◼ The teeth with less bucco-lingual width are preferredbecause this increases the stability and decreases the load on the lower ridge.

◼ Alternately, as Sears has suggested in 1957 that the choice of non-anatomic teeth may be considered with the use of flat occlusal table.

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Occlusion scheme

◼ During teeth arrangement it is advisable to provide a generous free way space because it is said to decrease the frequency and duration of functional and parafunctional tooth contact.

◼ Occlusion ramps: the occlusal ramps are made up of acrylic and are placed in the second molar region. The advantage of this is that there is always a simultaneous contact of the ramps on both sides in protrusive and lateral movements. This increases the stability of the lower dentrue and dislodging of the denture will not be there.

◼ Devan (1935) has used the neutrocentric concept of

tooth arrangement so that during the chewing

movement, there is no horizontal displacement.

In this method centric occlusion may be created as an

area which may be important where there is difficulty in

establishing entirely accurate relations due to lack of

retention of dentures.

Neutrocentric concept

Its significance:

It is the type of occlusion that eliminates any

anteroposterior or mediolateral inclines of the teeth and

directs the forces of occlusion on the posterior teeth.

Teeth are arranged on a plane, they are not inclined

to form compensating curves, thus eliminating the

lateral forces occlusion forces on the denture.

◼ George A Murell (1974)- utilized the concept

of lingualized posterior occlusion to increase

stability and comfort and to centralize the effect

of occlusal forces. He used 33º upper posterior

teeth with 20º lower teeth having custom

ground plane.

Lingualized occlusion scheme

Its significance:

Maxillary lingual cusps are the main functional

cusps, opposing mandibular 0º or shallow cusp

teeth in balanced or nonbalanced patterns.

The use of maxillary lingual cusps centralizes

the occlusal forces and reduces the frictional

resistance of flat teeth sliding over one another.

Use of devices

A) Springs

B) Suction chambers & discs

C) Magnets

D) Denture adhesives

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a) Springs:

◼ They are made up of solid stainless steel or gold plated

base metal. Theses have their ends attached to the

premolar and on both sides of upper and lower

dentures. The dentures are held in occlusion for

insertion into mouth.

◼ Disadvantages:

➢ Constant pressure may cause excessive resorption.

➢ Lateral movements are extremely restricted.

➢ They are unhygienic.

b) Suction chambers & discs:

◼ These are clearly defined outlined relief areas which are given. When the denture is inserted, there is a partial vacuum in this chamber while sucking and swallowing and this helps to keep the dentures in place.

◼ Disadvantage:

➢ They are functional only for few months.

➢ They causes palatal hyperplasia.

c) Magnets:

◼ Small magnets are embedded beneath the molar and premolar teeth. Similar poles are arranged opposite to each other.

◼ The repulsive effect of magnet will keep both the dentures in place, called as ‘repelling magnets’.

◼ Other magnets available are-

◼ Cobalt magnets

◼ Co-platinum magnets

d) Denture Adhesives:◼ These products are available in both powder and cream

forms. They contain substances which swell on

moisturing and become viscous. Eg. Carbonyl methyl

cellulose vegetable gums. Eg. Karaya, xantham etc.

Advantages: Disadvantages:

•Psychological security to the

patient

•Provides initial comfort to a

new denture wearer.

•Improves masticatory speech

efficiency.

•Unpleasant feeling.

•Support bacterial growth.

•Only a temporary retentive

measure

Special denture materials

1) A metal-based denture with soft liner.

2) Multiple suction cup dentures.

3) Hollow complete denture.

4) Thick bordered denture.

5) Implant supported overdentures.

1)Metal-base denture with soft liner.{Massad JJ. Metal-based denture with soft liner to accommodate

the severely resorbed mandibular alveolar ridge. J Prosthet Dent

1987; 57(6): 707-711.}

◼ Rationale:

The metal base provides the weight necessary to facilitate retention while maintaining adequate strength in a denture with modest extensions.

The soft liner accommodates ridge irregularities and changes such as excessive resorption, minimal keratinized ridge epithelium, thin lamina propria etc.

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Technique:

1) A full-coverage mucostatic impression is produced by using prefabricated impression trays.

2) Mandibular denture borders are outlined on the cast, which produces essentially a myostatic denture border.

3) The retromolar pad is outlined, and standard base-plate wax is adapted to a refractory cast following the complete denture border. The wax should be approximately 2-3mm thick to allow for adequate metal weight, but not so thick as to make it difficult to secure correct occlusal vertical dimension.

4) Wax framework is sprued, invested and casted.

5) 0º monoplane teeth or centrimatic posterior teeth

minimize lateral interferences, reducing instability of the

denture base.

Denture base is invested in the standard manner, with

acrylic resin cured between the teeth, cast metal base,

and tissue-bearing surfaces.

2) Multiple suction cup dentures:{ Engelmeier RL, Gonzalez ML. Restoration of the severely

compromized maxilla using multi-cup denture.

J Prosthodont 2008; 17:41-46}

◼ The multi-cup denture liner was developed to enhance retention, stability, and comfort for complete denture wearers, particularly those with significant resorption of their alveolar ridges.

◼ Precise Trefine holes had to be carefully perpared in the master cast with a special drill and contra-angle handpiece.

◼ The holes were 2mm in diam, approx. 1 mm deep, and had walls with a 12.5º taper.

◼ They were spaced 1 to 1.5 mm apart, and prepared perpendicular to the palatal and ridge surfaces.

◼ They were not prepared over frenum attachments or within 2mm of the denture borders. 200 holes for a maxillary cast and 150 for a mandibular cast.

◼ The prolastic liners were either added to processed dentures by creating space for the material in the base prior to making reline impressions or processed at the same time as the acrylic base of new dentures using a shim during packing.

◼ Or, the Prolastic material was added prior to final flask closure.

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◼ The liner space was prepared 2mm short of all denture borders with 90º butt joint margins and 1 to 2mm deep.

◼ Result: the expected shallow imprints of the suction cups; however, they have not shown signs of inflammation over the past 3-4 yrs.

◼ Found focal areas of slight inflammation where a hole had been drilled too deeply.

3) Hollow complete dentures:{ Bhat AM. A hollow complete denture for severely resorbed

mandibular ridges. J Indi Prosthet Dent 2006;6(3): 157-161.}

1) Two split dental flasks with interchangeable top halves were used.

2) Processed record base was made on the definitive cast by following conventional laboratory procedures.

3) Maxillomandibular relationship was recorded and transferred to the articulator.

4) Artificial teeth were arranged.

Hollow

complete

dentures

5) After trial insertion, the waxed mandibular denture

was invested in the first flask with dental plaster, wax

was bolied out the two halves of the flask were

separated.

6) Wax shim consisting of two layers of base plate wax

was then applied over the denture teeth area of the

flask assuring that the lid of the flask containing the

invested definitive cast and the processed record base

closed completely with the wax shim in place.

7) Bottom half of the first flask containing the denture teeth with the wax shim in place was then topped and flasked using the lid of the second flask, the wax shim boiled out, separating media was applied and heat polymerized acrylic resin was packed and processed as usual.

This resulted in two halves i.e., the processed record base and the half containig the denture teeth, which had to be then fused together.

8) Notches were made along the borders of the two halves to be fused.

9) Any excess acrylic resin on the inner surface of the half containing the denture teeth that would construct the hollow cavity was reduced.

10) Care was taken to avoid uneven reduction.

11) Two parts were then fused with auto polymerizing resin, during

the lab remounting stage and then tested for a complete seal by

placing it in water.

12) The denture floated ensuring a complete seal.

13) The denture was then finished and inserted.

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Implantology and the

severely resorbed

edentulous mandible

Eposteal dental implants:

◼ Eposteal implants: dental implants that receive their

primary bone support by leaning on the residual bone

of the mandible. Eg. Subperiosteal dental implants.

◼ The subperiosteal frame was introdued by Dahl in

1943. The technique was refined by Goldberg( 1949),

and later on by Linkow( 1998).

◼ Patients had to undergo two surgical interventions-

◼ First opertaion: Surgeon uncovers the bony edentulous

alveolar process and the surrounding basal mandibular

bone by raising a mucoperiosteal flap. Subsequently, an

impression was made of the denture-bearing area.

◼ Second operation: custom-made frame, made of a

cobalt-chromium alloy, was placed subperiosteally.

Fixed or removable prostheses could be connected to

several transmucosal posts.

◼ Disadvantages: Non-biological materials were inserted

into human tissues with open communication with the

oral environment, thereby creating transmucosal posts.

◼ Specific information about clinical performance in the

cases of severely resorbed mandible, is not much

available in the literature.

Transosteal Dental Implants

◼ Transosteal or transosseous dental implants are

implants composed of a metal plate and transosteal pins

or posts.

◼ The metal plate is held with retentive pins or screws

fixed to the inferior border of the mandible.

◼ This metal plate supports the transosteal pins/posts

that penetrate the full thickness of the mandible and

project into the mouth in the interforminal area.

Staple bone implant system{Transmandibular implant system (TMI)}

◼ The system was developed as an alternative to

subperiosteal frames.

◼ Main objective of the system:

To reduce forces on the implant and to make thin

transmucosal perforations.

To prevent overloading of this system, a tissue-borne

overdenture has to be made with stress-breaking

attachments to stabilize the denture.

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Mandible staple implant –is a type of transosteal implant that

allows the attachment of a lower denture to the abutments of two

or four threaded posts that go transcortically from a curved plate,

which has been inserted through a submental incision and fixed

into place at the inferior border of the mandible, through to the

canine areas of the alveolar crest of the mandible; retentive screws

partially inserted into the inferior border affix the rest of the plate.

Also known as mandibular staple implant and transmandibular

implant

◼ The staple bone implant system consists of a baseplate with two or four (parallel) tranosseous pins and from two to five retentive pins (or, screws) to stabilize the baseplate to the inferior border.

◼ The implant is made of a titanium alloy to allow for osseointegration.

◼ This system has been evalauted in several retrospective studies that have reported survival rates of between 86% to 100%.

Endosseous implant system

(short implants)

◼ The placement of short endosseous implants is another

option to treat the extremely resorbed mandible.

◼ In the case of severe ridge atrophy and short implants

(< 12mm), the ratio between implant length and the

distance to the occcusal plane is compromized,

resulting in favorable biomechanics.

◼ In a randomized clinical trial (by Stellingsma et al, 2004), that compared three treatment modalities viz.

transmandibular implant-

Augmentation of the mandible with an autologous

Bone graft followed by placement of four endosseous implant, and

Placement of four short endosseous implants for extremeyl resorbed edentulous mandible,

It was concluded that treatment with short endosseous implants is the treatment of choice due to the minimal complications, high survival rate, the staple bone-interfernace and patient can be treated in outpatirnt clinical set-up.

Grafting procedures

◼ Various techniques and materials have been developed to increase mandibualr height.

◼ Autogenous materials, such as bone and cartilage, and allogenic materials, such as hydroxyapatite or bone substitues, as well as combinations of these materials, are used for ridge augmentation.

◼ Depending on the clinical conditons, endosseous implants can be inserted at the same treatement session or after the graft has been incorporated for 3-4 months.

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◼ Onlay techniques as well as interposition of the graft in the inter-foraminal area are used.

◼ With both onlay or interposed bone grafts, hydroxyapatite can be used as a filler, alongside autologous bone, to achieve the desired volume and contour for the augmented mandible.

◼ Complications with grafting in the mandible: sensory disturbances of the mental nerve, wound dehiscence, infections of the grafted area, and with autogenous bone grafts, & donor area morbidity.

Distraction

Osteogenesis

◼ Besides grafting techniques, distraction osteogenesis

can be performed to improve the starting point for the

placement of implants in the inter-foraminal area of the

severely resorbed edentulous mandible.

◼ Distraction osteogenesis is a technique of gradual bone-

lengthening, allowing natural healing mechanisms to

generate new bone.

Procedure:◼ An osteotomy in the inter-foraminal area of the

mandible is made.

◼ Distraction device is placed.

◼ 5-7 days after surgery, active distraction is started at the rate of 0.5-1 mm/day.

◼ Between 4-8 weeks after the last day of active distraction, mineralization of the newly formed bone matrix in the distraction area has progressed sufficiently to allow for the placement of endosseous implants with sufficient primary stability.

◼ For next 3 months implants are left unloaded.

◼ Advantages: absence of any donor site

morbidity, presence of vital bone in the

distraction area, and the gain of soft tissues.

◼ Complication: fracture of the mandible,

necrosis of the superior fragment.

Options for restoration of extremely resorbed

mandible with implants:

1) Use of short endosseous implants in comination with eihter a fixed or removable prosthesis.

2) Augmentation of the mandible by means of distraction techniques or grafting procedures, followed by the placement of endosseous implants in combination with either a fixed or removable prosthesis.

3) Installation of a tranosseous implant system in combination with a removable prosthesis.

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Conclusion

Although challenging, the severely resorbed

ridges can be resorted to a certain level of

mastication with the help of improved

impression techniques, proper selection of

occlusion schemes and the use of specialized

dentures techniques. More recently, implant

supported overdentures are playing tremendous

role in the treatment of the severely resorbed

ridges.

References

◼ Bernard Levin. Impression for complete dentures. Quintessence publishing 1982.

◼ Atwood DA, Winkler S. essentials of complete denture prosthodontics. 2nd edition.

◼ Jermyn AC. Multiple suction cup dentures. J Prosthet Dent 1967; 18:316-325.

◼ Stellingsma C, Vissink A & et al. Implantology & the severely resorbed edentulous mandible. Crit Rev Oral Biol Med 2004; 15(4): 240-48.

Thank you

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MAXILLOFACIAL PROSTHODONTICS

BY: DR. SUDHIR MEENA

INTRODUCTION

Definition;Maxillofacial prosthodontia is the art and science of functional, or cosmetic reconstruction by means of non-living substitutes for those regions in the maxilla, mandible, and face that are missing or defective because of surgical intervention, trauma, pathology, or developmental or congenital malformation.

Maxillofacial prosthodontics is the branch of prosthodontics concern with restoration or replacement of the stomatognathic and craniofacial structure with prosthesis that may or may not be removed with regular or elective basis.-

CLASSIFICATION OF MAXILLOFACIAL PROSTHESES

A wide variety of maxillofacial prostheses are being fabricated in practice. Based on the location, use, and area of restoration, maxillofacial prosthesis can be classified as follows:

Prosthesis:

IntraoralMaxillary

. Congenital- Cleft lip- Cleft palate

Acquired

⚫ Total maxillectomy

⚫ Complete dentures⚫ Partial dentures

⚫Obturators⚫ Speech aids

⚫ Implants⚫ For partial maxillectomy

⚫ Complete dentures

⚫ Partial dentures

MandibularCongenital⚫ Cleft lip⚫ Early feeding devices⚫ Surgical.⚫ Orthodontic.⚫ Prosthodontic.⚫ Fixed partial dentures⚫ Complete dentures – ImplantsAcquired⚫ Complete dentures⚫ Partial dentures⚫ Flange prosthesis⚫ Mandibular exercisers - Implants

Extraoral

⚫ Auricular prosthesis

⚫ Ocular prosthesis

⚫ Orbital prosthesis

⚫ Nasal prosthesis

⚫ Composite prosthesis

⚫ Lip and cheek prosthesis

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Treatment supplements:

Radiotherapy supplements- Stents- Splints- Shields- Carriers-Positioners

Radiation appliances. Surgical supplements- Prosthetic dressings- Surgical splints-Surgical obturators

MAXILLARY DEFECTSPatients with maxillary defects will have difficulties in

mastication, speech and deglutition. The aim of a maxillofacial prosthesis should be to restore the normal physiological function in these patients. The fabrication of the various prosthesis used in the management of these defects are described in the next chapter.

Types of Maxillary DefectsMaxillary defects can be broadly classified as follows:Congenital⚫ Cleft lip⚫ Cleft palateAcquired⚫ Total maxillectomy

⚫ Partial maxillectomy

Congenital Maxillary DefectsCleft lip and cleft palate;

Cleft lip occurs due to improper fusion between the fronto-nasal and maxillary process. If this occurs on one side it leads to

a unilateral cleft. If it occurs on both sides, it leads to a bilateralcleft.

Veau's Classification of Cleft PalateVeau (1922) classified cleft palate into four types mainly,

⚫ Class I: Cleft involving the soft palate. It can also be a sub-mucous cleft, which appears normal

⚫ Class II: A midline cleft involving the bone, present only on theposterior part of the palate

⚫ Class III: A unilateral cleft extending along the mid-palatinesuture and a suture between premaxilla and palatine shelf

⚫ Class IV: A unilateral cleft extending along the mid-palatinesuture and both the sutures

Prosthetic consideration; For young patients, a permanent prosthesis

should not be provided, instead, a well fitting interim prosthesis should be provided. This interim prosthesis is replaced with a permanent one at around 25 years of age. A removable interim partial denture is preferred over a fixed prosthesis because it is more aesthetic in reproducing gingival contour, and it also helps to cover an unaesthetic residual alveolar cleft. The most important concern in the restoration of these cases is establishment of aesthetics.

Posterior cleft palate cases are usually treated using speech bulbs and palatal lift prosthesis. These maxillofacial prosthetic appliances are usually combined to the conventional prosthesis (RPD, CD, FPD) that may be required for the patient.

Types of Acquired Maxillary Defects

Acquired maxillary defects are usually classified based on their extent. If both the maxillae are resected, the defect is considered as total maxillectomy. Resection of one or a part of the maxilla or palate is considered as Partial Maxillectomy.

Aramany proposed a classification of partial maxillary defects based on their extent.

⚫ Class I: It is a unilateral defect involving one half of the arch and the adjacent palatine shelf. The defect extends to the midline (all the teeth in that side of the arch are missing)

⚫ Class II: It is a unilateral defect involving one side of the arch posterior to the canine (teeth posterior to the canine are absent)

⚫ Class III: It is a defect involving the centre of the

palatine shelves (all the teeth are present)

⚫ Class IV: It is a bilateral defect involving the one side

of the arch along with the entire premaxilla (all

anteriors along with the posteriors of one side are

missing)

⚫ Class V: It is a bilateral posterior defect (teeth

anterior to the second premolar are present)

⚫ Class VI: It is a bilateral anterior defect (teeth

anterior to the second premolar are absent).

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⚫Mandibular Defects⚫ Congenital Defects of the Mandible⚫ Congenital mandibular defects that require a

maxillofacial prosthesis are uncommon. Common congenital defects of the mandible include micrognathia, mandibulofacial dysostosis, ankylosis of the temporomandibular joint, etc.

Acquired Defects of the MandibleAs mentioned for the maxilla, neoplastic

resection is one of the most common causes for an acquired mandibular defect. The common neoplasia which advocate the need for resection are squamous cell carcinoma of the tongue, oropharynx and floor of the mouth.

Types of Acquired Mandibular DefectsBased on the amount of resection or bone loss (extent), mandibular defects can be classified as follows:

⚫ . Continuity defect: Here the superior portion of the mandible is resected and the lower border is left intact. These defects do not show any deviation and are easy to restore

⚫ Discontinuity defect: Here the entire segment of the mandible is resected. Since there is no connection between the remaining parts of the mandible, there will be midline deviation of the mandible due to the movement of the bone. Deviation may also occur when the remaining ends are surgically approximated in order to produce continuity.

VELO-PHARYNGEAL DEFECTS.They are basically defects of the palate, which effects

the closure of the naso pharyngeal and oro-pharyngealishtumus. This lack of closure will effect speech.

Treatment of Velo-pharyngeal Defects⚫ Congenital velo-pharyngeal defects due to palatal

insufficiency can be restored by surgical reconstructionfollowed with the insertion of an obturator to correct theresidual palatal insufficiencies.

⚫ Congenital velo-pharyngeal defects due to poor structuralintegrity can be treated with palatal surgery.

⚫ Acquired velo-pharyngeal defects due to surgicalresection can be treated by surgical reconstruction andprosthodontic rehabilitation (E.g. obturator).

⚫ Acquired velo-pharyngeal defects due to trauma andneurological deficiencies can be treated by prosthodonticrehabilitation using a palatal lift prosthesis.

EXTRAORAL DEFECTSDefects occur due to trauma,

neoplasm or congenital malformationThe common neoplasia of the head and neck include:

⚫Epithelial tumours: epithelial facial tumours may have a melanocytic, keratinocytic or adrenal origin.

⚫Connective tissue tumours: adenomas, fibromas, leiomyomas and lymphomas.

⚫ include:

Extraoral congenital malformations that

require maxillofacial prostheses include:

Auricular defects:

1. Microtia (small ear) associated withatresia of the external auditory meatus.

2. Anotia (complete absence of the auricle).

3. Smaller ear defects.

Nasal defects:

⚫ The defects arising due to surgery are

known as Rhinotomy defects.

⚫ Ocular defects: It involves the defects in the eyeball with intact eyelids (lacrymal apparatus. An orbital defect involves both the eyeball and the eyelids. Most of the ocular defects are acquired (by surgical procedures like evisceration-removal of the eyeball preserving the sclera, enucleation and excentration).

⚫ Lip and cheek defects like double lip, hemifacial microsomia etc.

⚫ Combination of the above mentioned defects.

⚫ Aesthetics is the major principle behind the placement of these prosthetic appliances. Hence, most of these prostheses are non-functional.

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THANK YOU

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➢ Introduction

➢ Development / Embryology

➢ Muscles of mastication (in detail about each)

➢ Movements of mandible at TMJ

➢ Physiology of masticatory muscles

➢ Mastication – Role of masticatory muscles

- Reflexes

➢ Investigations

➢ Disorders of muscles

MUSCULUS – “little mouse”

Is a soft tissue found in most animals

Muscle cells -protein filaments of actin & myosin -contraction – changes length & shape of the cell

Definition of Mastication : It is defined as the process of chewing food in prepration for swallowing and digestion.

Definition of Muscle : An organ that by the contraction produces movements of an animal; a tissue composed of contractile cells or fibers that effect movement of an organ or part of the body.

Day 17 – 3 germ layers

Day 19 – mesodermal plate cleaves – diff of somite plate - somites

Day 20-21 – 42-44 pairs of somites

Myocoele, Sclerotome , Dermatome, Myotome

Reference: Inderbir Singh

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4th week- the oral pit is surrounded by several masses of tissue. Pharyngeal arches are also evident below the pit & on the sides of the neck

During 5th & 6th weeks -primitive muscle cells from mesoderm of mandibular arch begin to differentiate.

By 7th week - cells migrate into areas where they will differentiate into muscles of mastication.

By 10th week - muscle masses become well organized & 5th cranial nerve branches are incorporated.

Reference: Inderbir Singh Reference: Inderbir Singh

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NERVE SUPPLY OF HEAD AND NECK

DR. SUDHIR MEENA

➢CRANIAL NERVES

➢AUTONOMIC NERVES

➢SOMATIC NERVES

➢NERVES SUPPLYING THE SKIN

CRANIAL NERVES

• 12 PAIRS

• DISTRIBUTED IN HEAD AND NECK

OLFACTORY NERVE

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Clinical Notes

• Lesions - anosmia

• Head injuries – cribiform plate fracture

• Tumors near pituitary glands

OPTIC NERVE

OCCULOMOTOR, TROCHLEAR AND

ABDUCENT NERVES

Clinical Notes

➢Occulomotor nerve – lesions – ptosis

➢Raised intracranial pressure

➢ Aneurysms – posterior communicating artery

➢ Internal carotid artery aneurysms

➢Trochlear nerve – superior oblique paralysis

➢Abducent nerve – lateral rectus paralysis

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TRIGEMINAL NERVE

• LARGEST NERVE

• MIXED FIBRES

• 3 DIVISIONS

• Anterior surface - pons

Clinical Notes

➢Trigeminal neuralgia

➢Frey’s syndrome

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FACIAL NERVE

Clinical Notes

• Bell’s palsy

• Forceps delivery – facial nerve paralysis

• Melkersson Rosenthal syndrome

VESTIBULOCOCHLEAR NERVE

GLOSSOPHARYNGEAL NERVE

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Clinical Notes

• Lesions cause:

• Loss of sensation

• Loss of gag reflex

• Difficulty in swallowing

• Glossopharyngeal neuralgia

VAGUS NERVE

Clinical Notes

• External laryngeal nerve - inability to tense cords

• Recurrent laryngeal nerve –decreases airway

ACCESSORY NERVE

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Clinical Notes

• Inability to turn the head

• Inability to shrug shoulder

HYPOGLOSSAL NERVE

Lesions - Deviation on protrusion

CERVICAL PLEXUSCERVICAL PART OF SYMPATHETIC

TRUNK

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Bibliograghy

•Bernard Liebgott:The Anatomical Basis of Dentistry. 2nd Ed: Mosby , 20•E.LLOYD Dubrul. Sicher & Dubrul’s Oral Anatomy. Ishiyaku Euro America. 8th Ed.1990

•G.J. Romanes: Cunningham’s Text Book of Anatomy. Oxford medical publications. 12th Ed.1995•GAG Decker, DJ du Plessis: Lee Mc George’s Synopsis of Surgical Anatomy.12th Ed. Varghese publishing house.1999•Keith Moore, Dalley. Clinically Oriented Anatomy. Lippincott Williams.4th Ed. 1992

•Richard , Wayne,Adam Mitchell.Gray’s Anatomy for students.Elsevier.1st Ed.2005

•Richard S. Snell. Clinical Anatomy for Medical Students. Lippincott Williams. 6th Ed. 1993• Williams & Warwick: Gray’s Anatomy.36th

Ed: Churchill Livingstone, 1986

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DR. SUHIR MEENA

INTRODUCTION

Unfortunately there are many patient today who had extracted their teeth at early age.

When our teeth are extracted the bone that supports the roots slowly dissolves away causing bony ridge & gums to shrink.

Eventually the patient will have difficulty in using the denture , especially the lower denture.

✓ Dental implant may provide stabilization , however there may be situation when it is not possible to provide on the grounds of medical & surgical or cost factors.

✓ There is technique which is not new but a valuable , which can be alternative for these complex situations.

✓ THE NEUTRAL ZONE TECHNIQUE

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DEFINTITION

✓ NEUTRAL ZONE: also known as stable zone (Gerber 1954) , Dead space, and Zone of minimal conflict ( Mathews).

✓ According to GPT 8: The potential space between lips & cheeks one side & tongue on the other side.

✓ That area or position where the forces between tongue & cheeks or lips are equal.

✓ Since these forces are developed through muscles contraction, during functions like;

: Swallowing

: Chewing

: Speaking

✓ They vary in: magnitude

: direction in different individual & different periods of life.

✓ The way these forces are directed against denture will either help to stabilize it or will tend to dislodge it.

The AIM of NEUTRAL ZONE is to construct a denture in muscle balance.

SOME OF THE INDICATIONS

✓ Partial glossectomy

✓Mandibular ressection

✓Motor nerve damage to the tongue.

✓Unfavourable denture bearing area

✓ Patient’s with poor neuromuscular control.

FACTORS AFFECTING NEUTRAL ZONE

✓ Muscles of cheek:

The outer limits of neutral zone are determined by the perioral musculature.( The Landmark work was done by Sidney Fredrick) , is the Buccinator muscle.

✓ Frederick observed the changes in both hard & softtissues caused by effects of different perioral muscular complexes ,as result of pressure resorption.

✓ Areas of resorption: directly related to specific band of buccinator , made clear that the length of the contracted muscle is strictly limits the size of the arch.

✓ If the arch is expanded beyond the acceptable length → resorption of tissues covering the labial surface of the roots.→thinning of soft & bone tissues.

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✓ These effects are seen primarily on the lower arch, greatest in anterior segment.

✓ In the lower anterior;

: The effect of pressure varies according to where

the lower band overlays the anterior segment.

: In this region lower band is classified

High

Middle

Low

✓ High: causes thinning of the soft tissue , gingival recession& thinning of labial bone.

✓ Low: is most common.

✓ Combined width of 3 bands :

✓ The arch is limited by length of the muscles when they contract.

✓ Strongest: Class 2 divsion2

✓ Weakest: Bimaxillary protursion.

✓ Constricted perioral musculature : Problem of alignment of teeth if they are too large.

✓ May effect the dentoalevolar arches from expanding to a normal alignment with skeletal base.

Splayed anterior teeth.The effect of strong tongue posture

combines with a strong lower band that is positioned low.

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4

✓ In function buccinator helps to place the food over the occlusal surfaces of the teeth in coordination with the tongue , which position the food over teeth from lingual.

✓ Lingualization of occlusion prevents the buccinator from performing its functions in 2 ways:

Space exist between external surface &

cheek→accumulation of food.

Neutraliztion of forces are lost

✓ MASSETER: has no influence on the neutral zone

: effect only the distobuccal border of

the denture.

✓ GREATER ZYOMATIC MUSCLE: pulls the angle of the mouth upward & backwards.

✓ RISORIUS: retracts the corner of the mouth.

✓ MENATLIS: turns the lower lip outward.

: shallow lower vestibule.

✓ TRIANGULARIS: exerts pressure on the teeth and

denture flanges.

MODIOLUS: strength

variability→ important in stability of denture

The denture should be contoured by narrowing in the premolar area→ unseat the lower denture.

✓ ORBICULARIS ORIS: form the lips In functions exerts: force against the teeth & flanges counteracted by the tongue.

TONGUE

✓ Tongue is composed: Intrinsic: Extrinsic muscles

✓ Tongue is capable of varied position ,shapes during all these it is in constant contact with lingual surfaces of the lower denture & palatal surface of upper denture.

✓ Because of this play a dominant factor in establishing the neutral zone &stability of lower denture.

✓ Wright has stated if the posterior teeth are set even 1mm lingually , the tongue space is deprived of 1000mm3 which can force tongue in retract position.

✓ The dentist has always been concerned with equalizing the vertical forces:

Delivered by occlusal surfaces which is counterbalanced by vault & ridges.

✓ It has ignored the importance of the horizontal forces acting on the denture surfaces

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5

WHAT ARE THESE DENTURE SURFACES

DENTURE SURFACES

Sir Wilfred Fish (1948) describe a denture as having 3 surfaces.

✓ Impression surface (intaglio): Concerns mainly with retention.

✓Occlusal surface: The stability of the denture when the teeth are in contact is determined by the fit of the impression surface against the tissues & fit of occlusal surface against each other.

✓ Polished surface: Of the denture which contact the tongue, cheeks & lip.

✓ The shape of this surface as a whole determines whether muscle movement will dislodge/ stabilize the denture., when properly formed the retentive force of the buccinator& tongue enables the patient to control the denture after resorption has occurred.

✓ The contour of the denture is largely depend upon:

: Buccolingual position of the teeth in relation to the

residual ridge.

: Wax up of the denture.

✓ The polished surface of denture exhibit a series of inclines:

✓ The palatal surfaces of upper denture looks inward & downward, while the lingual surface of the lower looks inward & upward.

key points

✓ Flanges of the lower denture extend : under the

buccinator & tongue , act as handle, Stability.

✓ Flanges must be narrower in the bicuspid region .

✓ Instability of denture:

:If the flanges are too wide in premolar region.

:Lingualization of occlusion .

:Buccal & lingual flange in the molar region

are parallel so that tongue & buccinator will

not hold them.

✓ The most important basic principle is that the teeth must occupy a position , so that tongue is pressed inward with just as much force as the cheek outward.

✓ The proper position for the teeth is not on the ridge, inside it, but at a point where the pressure of the tongue & cheek balance each other.

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6

MUSCLE INFLUENCE ON THE DEVELOPMENT OF DENTAL ARCHES

✓ Teeth erupts in the mouth under the influence of muscular environment which is created by the forces between :

:Tongue

:Lips& Cheeks

: + Genetic factor + Local environmental forces has

direct influence on:

Position of teeth

Arch form

Occlusion.

During childhood & adolescence

↓

Muscular activity & habits will develop

↓

After the teeth lost, these will still persists

↓

Have great influence on CD & RPD placed in mouth.

Our objective is to utilize the information of muscle function , so as to position the teeth & external surfaces of the denture that the force of musculature , instead of having negative influence will favorably affect the denture & seat it.

DETERMINATION OF NEUTRAL ZONE & DIAGNOSIS & TREATMENT PLANING

✓ Success in complete denture is dependent on what is done prior to the construction of denture as much as or more than on the skill & meticulous care utilized in the construction of dentures.

✓ Examination , diagnosis & treatment planning for complete dentures should be as meticulous & detailed as for any other branch of dentistry.

REVERSED SEQUENCE IN DENTURE CONSTRUCTION

✓ USUAL SEQUENCE

✓ Primary impression

✓ Construction of custom tray& final impression.

✓ Fabricate denture base

✓ Occlusion rim to establish VD& CD.

✓ REVERSED SEQUENCE

✓ Primary impression.

✓ Stable denture base

✓ Instead of wax modeling compound is used for occlusion rim.

✓ Rim molded to locate the neutral zone.

✓ Tentative VD, CR & Final impression.

✓ VD &CR are refined & finalized.

✓ The premise behind the rationale is that,, in our thinking & in our procedures, we should separate the denture base from that which rest on the denture base- the body of the denture.

✓ With Neutral zone approach,

✓ The impression surface of denture base is called as : Base.

✓ The polished surface : Body of the denture.

RATIONALE FOR THIS REVERSED SEQUENCE.

✓ Once the denture is processed , it is frequently very difficult , if not possible to evaluate which of 3 factors;

Overextension of the base→ impression surface.

Improper tooth position →polished surface.

Improper occlusion → occlusal surface, are

causing the instability .

✓ The PROBLEM is simplified if during construction of denture each surface is considered & fabricated so as not unseat the denture.

✓ This achieved by reversed sequence of denture construction, .

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7

✓ In neutral zone approach each surface/ factor is deal at a time, making us aware which is creating the problem.

✓ First, an acrylic base is constructed of self cure acrylic→ placed in patient’s mouth → check it if it is retentive or not.

✓ If unstable than →overextension of the borders of the base.

✓ At this stage only 1 Factor is to be consider :the border of the base since body & occlusion have yet not been constructed.

✓ If we place on this stable base the body of denture be of compound/any material which will replaced by teeth & external

surfaces of teeth , the base is no longer stable than →Cause is body.

Horizontal forces exerted against the body of the denture by the lips, tongue & lips.

✓ Solution: Adding /subtracting

: Physiologic procedures →the body is repositioned so that the forces of lips , cheeks & tongue do not unseat the base.

✓ We have an upper & lower base & body .

✓ If we make VD, and the denture bases are dislodged.

✓ Cause : occlusion

✓ Occlusion should be corrected.

✓ Thus following just outlined, we know exactly where the problem is & can correct or eliminate it.

All of us experience of inserting a lower denture as soon as seated

↓

Begins to pop up, jumps up during speaking.

↓

1st assumption :overextension of the denture base

↓

Reduction of denture base: not unusual to end up in denture base that is too smaller than original.

What we were not aware ?

It’s not only the denture base , is the cause of instability. but rather : body of the denture, tooth position ,& flange of the denture base.

CLINICAL & LAB PROCEDURES

✓ After thorough examination of the patient ,the stock trays are selected.

✓ Primary impressions are made.

✓ Two major consideration for obtaining a good impressions are : proper extension.

✓ Minimal tissue displacement so that acrylic base is stable to construct occlusion rims for locating the neutral zone.

CONSTRUCTION OF ACRYLIC BASE

✓ The base made in neutral zone approach serve 2 purposes:

:occlusion rim will constructed, which will molded by the patient to locate neutral zone & to establish a tentative VD& CR.

: As tray for final impression.

✓ For this it’s important that base is stable.

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8

CREATING STABLE BASE

✓ Is one that will stay in place & not dislodged during normal function.

✓ The stability is tested in 2 ways; base is placed in mouth & operator’s fingers are placed in the bicuspid region to seat the base →squishing sound comes →unstable.

✓ Ask the patient to open wide , purse the lip as in sucking wet, the lips→if movts →unstable.

✓Usually the lack of stability is overextension.

✓Methods used for checking the overextension

:Visual examination.

: Disclosing agents

Various design of base for retention of materials

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9

LOCATING THE NEUTRAL ZONE & OCCLUSION

✓ To locate the neutral zone & form the body of the denture , it is necessary to use material that can be molded by the horizontal forces of tongue, cheek & lip.

✓ MATERIALS used:

✓ Buchman & Gelb & Lott, Levin & Russell have used waxes.

✓ Klein has used self cure acrylic to form Piezograph( a form molded in a suitable impression material by tongue, lip & cheek in areas of mouth.

✓ Health used gels, i.e polmer of dimethyl siloxane with 12% of calcium silicate.

✓ Trench : modelling compound.

MANIPULATION OF COMPOUND

✓ To develop: the body of the denture

: register the neutral zone, by the use of compound,

✓ 3 factors are considered.

: securely Attached to the tray.

: Softened

: Hard

Consistency is similar to primary impression.

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10

LOCATING THE NEUTRAL ZONE FOR THE LOWER ARCH

✓ The patients lips are lubricated with petroleum jelly.

✓ Tray is inserted in to the patient’s mouth is instructed to swallow & the purse the lip as in sucking

✓ However some patients will have difficulty in swallowing for these patients there are some instructions/ procedures.

✓ Remove the rim from the mouth & instruct to swallow, if swallows correctly several times, explain that this exactly what shld be done.

✓ If difficulty still persist , place a drops of water on the tongue , ask the patient to swallow.

✓ Always ask the patient: to keep the lips together & swallow.

:not closed the lips & swallow, by doing this the patient may overclose & press against the maxillary rim , distort it.

✓ Problems encountered : Any excess material above the height should be removed→ improper molding of compound in to neutral zone.

:Difficulty in obtaining a narrow , properly molded neutral zone

✓ Cause: material is not soft

Tissue conditioner used as neutral zone impression

material

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11

What happens when we ask the patient to swallow ????

✓ Swallowing is freq repeated function,

✓ We swallow from 200-2,400 times per day.

✓ The most extreme movements of the posterior part of the floor of the mouth occur during swallowing

✓ Parts of the lower denture lies on : bone

: movable soft tissue, these parts are posterior part of lingual flange , buccal flange& retromolar fossae of denture.

✓ The posterior of lingual flange covers posterior part of mylohyoid extends in to the retromolar space.

✓ Buccal flange :buccal shelf.

✓Movements which occur during swallowing:

✓Mylohyoid : Raise the tongue-hyoid-larynx complex

: Acts as curtain which swings both inward & upward →which molds the material anteriorly to retromylohyoid

✓ At rest a space exits between lingual flange & mylohyoid: seals the denture.

✓ The anterior part of mylohyoid molds the anterior border of the lingual flange, results in s–shaped curve.

✓ Retromylohyoid region : Hyoglossus

: raises the tongue-hyoid larynx

: raises the tongue→compresses the space lingually & below to form the outward curve of lingual flange.

✓ Thus presses the mat against the passive lateral wall of retromyohyoid space.

✓ Superior constrictor: contracts: reduction of space.

ESTABLISHING THE OCCLUSAL PLANE

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12

✓ Testing the stability of the lower rim: Insert the rim in patient’s mouth.

✓ Asked the patient : to open wide

: Wet the lip with tongue

: Count from 1- 100

: Say exaggerated “oh”,

ahs & ees.

✓ Than locate the neutral zone for the upper arch same as lower.

JAW RELATIONS

✓ Tentative vertical dimension is registered by swallowing.

✓ The rationale behind this approach is that when a food is swallowed , the teeth meet at normal vertical dimension of occlusion.

✓ Shanahan: has noted that dentition erupt to a level & maintained at that level of normal vertical dimension by the repeated occlusal contacts that result from swallowing.

✓ The lower rim is lubricated & inserted in to the mouth.

✓ The upper rim is softened by flaming & tempering , is inserted in to the mouth

✓ Patient is guided to terminal hinge position.

✓ When the lower rim touches the softened compound of upper rim , the patient is inserted to swallow

→tentative VD is dictated by swallowing.

✓ Procedures for VD have their limitations. In this technique VD will be determined by swallowing checked by rest position& associated interocclusal space & finally verified by phonetics

USING THE NEUTRAL ZONE To OBTAIN MAXILOMANDIBULAR

RELATIONS

✓ Final impression

✓ Record base : stable.

✓ Contour the wax rim on maxillary base.

✓ Softened the compound & place it on mandibular base.

✓ Insert the mandibular base in the patient’s mouth ask to swallow & suck to mold in to the neutral zone.

✓ Place the maxillary rim in the patient’s mouth.

✓ Softened the mandibular rim, place in the mouth.

✓ Guide the patient in CR.

✓ Instruct to swallow.→imprint of maxillary occlusion rim in to the mandibular rim

✓ Tentative VD has been determined & anterior stop is created.

✓ Evaluate the VD

Facial support : VD at rest : Closet speaking space.

✓ Do not alter the anterior portion of the rims.

✓ Place V haped notch in both upper & lower rim.

✓ Face bow registration

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13

✓ Place both record base in the patient’s mouth, & guide it in the CR.

✓ Record the CR position by injecting fast setting vinyl polysiloxane.

✓ Advantage : Functionally molded in to the neutral zone, more stable base.

✓ Disadvantage: Incorrect VD , if material is not soft.

✓ Anterior stop may produce error due to possibility of displacement of record base.

FINAL IMPRESSION

✓ Impression material :Plaster of paris

: Alginates

: Rubber base

: Zno eugenol

✓ The material of choice depend upon operator.

✓ Impression techniques: Open

Closed

✓ Both these can be incorporated in to neutral zone but closed is preferred

Closed mouth /functional impression technique

✓ Objectives: To register the tissues in the position they would be in during function.

✓ The concept is not accepted now because:

✓ Functional impression will vary depending upon: Type of impression material

Direction of force exerted.

Amount of force exerted.

✓ Aim is to keep this pressure to minimum, necessary for proper adaptation.

✓ Advantages:

: More accurate functionally molding of

impression.

✓ Macmillan: Adequately trimming the lingual borders of lower arch , as he belief tongue movts are forceful in closed mouth.

✓ Disadvantages:

: No control over the pressure.

:Sometimes tendency for overextension.

: Appointment time is too long.

LAB PROCEDURE

✓ Face bow transfer done on the articulator.✓ Both upper & lower impression are boxed & cast are

made.✓ Compound rims thus formed indicate where teeth should

be placed so that denture will not displaced during functional movts therefore necessary provision for the preservation of the neutral zone for this:

✓ Fabrication of tongue, lip & cheek matrices:✓ Prior to this, the cast must be indexed so that the matrices

will fit back in their proper positions: holes , cross are made on the labial , buccal surfaces of the cast.

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14

ARRANGEMENT OF TEETH

✓ Sucess of complete denture upon the proper positioning of artificial teeth.

✓ Weinberg : Stated that buccal cusps & fossae of the posterior teeth should be directly over the ridge.

✓ Heartwell & Rahn: Posterior teeth should be positioned buccollingually on the ridge.

✓ Pound: Arranging the teeth on the ridge , condemned patient by accentuating facial deformity, phonetic problems.

Murray & Watt: teeth should be placed where the natural teeth grow.

Beresin: the teeth should be arranged in the neutral zone

Boucher Carl o. Leverage is a concern for the teeth over ridge, where neutral zone considers muscular forces created during functions,

Leverage is not ignored but lack of favorable leverage is counterbalanced by tongue , lip & cheeks.

ARRANGEMENT OF TEETH

✓ Arrangement of anterior teeth:

✓ Different opinion: On the ridge , esthetic are compromised, increased stability.

: Arrange them in their original place.this result great deal of guesswork esp if there is considerable resorption of the ridge.

✓ Advantage of neutral zone : The labiolingual position of the teeth is limited by the boundaries of the nz, which greatly simplifies as to where to position the teeth

✓ POSTIONING OF LOWER TEETH: Lower NZ formed, wider than labiolingual thickness of anterior teeth.

✓ Allows leeway : Central : Labially : Lingually.

✓ But within the contour of NZ✓ The decision is based on :Esthetic

: Phonetic: Functional requirement.

✓ The vertical position of the lower anterior is based on the occlusal plane as established on lower rim.

✓ Postioning of upper anterior teeth.: Same like lower anterior teeth.

✓ Arrangement of posterior teeth:

✓ The neutral zone indicates the labiolingual position of the teeth.

✓ The occlusal form of the teeth to be used are essentially operator choice.

✓ With Neutral zone approach posterior crossbite occur:

✓ Action of tongue during swallowing→places the lower posterior teeth more buccal to conventional position over crest of ridge.

✓ During sucking→the cheeks place compound& therefore NZ over the crest of the upper alevolar ridge.→posterior crossbite.

✓ Weinberg(1958): stated that a crossbite is less efficient than normal buccolingual tooth positions.

✓ However , a crossbite on a very stable base is better than normal buccolingual relation of teeth on a unstable base.

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15

TRIAL DENTURE

✓ The purpose : Stability & Retention.

: Vertical dimension.

: Phonetics.

: Centric Relation.

✓ With Neutral zone there is important procedure of making external impression on the labial, buccal lingual surfaces i.e

Determines the Thickness , Contours & Shape of

polished surface.

✓ In our impression procedures: Primary impression is made→Custom tray→ Secondary impression.

✓ Similarly locating the Neutral zone with compound may be compared to the primary impression.

✓ Trail denture acts as tray for Secondary impression.

✓ The material used are: Zinc oxide eugenol.

: Low viscosity polyvinlysiloxane.

✓ Advantage: Ledge in the anterior region ( patient’s can tolerate it)

: Help to keep the tongue on them →Increased stability.

: Accumulation of food on the external surfaces of the denture is decreased.

: Forms the functionallycontoured external surface.

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16

THE NEUTRAL ZONE AS APPLIED TO PARTIAL & OVRDENTURES.

✓ THE NZ concept is used for extensive partial denture provide: function , comfort, esthetics, preservation of ridge & teeth.

✓ The principal is to: ✓ Minimize harmful forces to the remaining teeth is to

obtain maximum stability.✓ Metal framework is obtained.✓ Metal loops on metal base for retention of compund: NZ

& occlusal plane is determined.✓ If upper teeth are present it will dictate, the occlusal plane

of the lower.

•

METHODS FOR ALTERING THE NEUTRAL ZONE

✓ Orthodontics.

✓ Elimination of noxious habits.

✓ Myofunctional therapy.

✓ Reduction of tongue size.

✓ Surgical lengthening of the buccinator band.

✓ Vestibuloplasty.

Review of literature

Fish(1952): stated that the teeth must occupy a position so that the tongue is pressed inwards with just as much as force as the cheek is pressed outside, in this way denture occupy a dead space in mouth.

Tuckfield(1953): stated that polished surfaces are in contact with muscles, which can dislodge a denture if it is incorrectly shaped, but can have definite & strong stabilizing & in fact retentive force on denture.

Lammie G.A(1956); concluded that the teeth & denture base should be placed where the muscles & mucosa allows them for better retention & occlusion& not by just ruining the lower denture by setting the teeth to ideal occlusion.

Franklin(1960) said that nature’s method of tooth placement & contours of tissues resulted in more esthetic appearance, comfort of the patient.

Raybin Nathan : stated that lower anterior teeth should be placed over the ridge,as they forms fav inclines.

✓ Premolars: slightly lingual to ridge, no interference with modiolus.

✓ lower molars: placed on or buccal to ridge, create a favorable space for tongue & adequate flange for cheek support.

Sheppard Irving(1963) did a cineflurographic study in 10 patients by asking them to eat peeled apple, walnut, meat & banana.

✓ Concluded: more denture movement with teeth apart than during contact;therefore, effect of occlusion on stability & retention during mastication appeared less significant than that of musculature.

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17

Stromberg W.Ross& Judson C.Hickey(1965) compared the retention of bases whose external surfaces had been formed by manual & physiologic procedures.

✓ The result showed: that physiologically formed shows

Better retention.

Facial support &tooth location.

Brill N;G tryde(1965): stated that positioning of teeth cannot be based exclusively on static principles, dynamic principles operating in the denture space must also considered.

Fahmy F M : compared mastication , comfort & speech characteristics b/w two set of denture,1 with neutral zone & other with convectional, concludes that neutral zone denture were more preferred.

Fahmi F M (1992) states that as the period of edentulousness increases the more buccally or labially the neutral zone was located in relation in relation to alveolar ridge.

Wee Alvin,G Rogerb.Cuynar(2000):used the neutral zone technique for fabrication of mandibular complete denture in patient with maxillofacial defect.

Zarb et al: stated that the longer the period of edentulous, greater will be the loss of original muscle pattern & less easily & completely they will be relearned even when the best dentures are provided.

Faber .L.Ben surveyed 54 schools regarding the arrangement of artificial posterior teeth

The results shows: 59.2% of schools taught over crest.

Arranging over the crest :reduction of 2.75mm in arch width.

The author concluded that: physiologic method teeth shld be placed buccal to the crest as compared to anatomic method.

Tyson K.W(2000): presented treatment of complete denture problem with atrophic mandibular ridge, stated:

✓ The peripheral form of polished surface should be in harmony with surrounding musculature for stability.

✓ Cord J.F: stated that in patients with atrophic mandible it is prudent to position the teeth in area of minimal conflict , neutral zone , for stability.

Ohkubo chikaharo et al (2000) presented a technique for a patient who had undergone a surgical resection of 1/3 of tongue & composite resection of floor of mouth.

Technique :

✓ Master cast was obtained wax rims were fabricated.

✓ VD was established & soft tissue conditioner was adapted to rim & patient was asked to purse his lips & swallow .

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18

✓ Neutral zone was established. denture was processed & then direct relining on both tissue & polished surface with visible light cure resin was done. this method has been termed as border molding or relining technique.

✓ The author concluded that stability obtained with

technique not only for edentulous patient but also for oral deformities.

Advantages: as compared with neutral zone processed denture;

✓ The border can be molded well because both the intaglio & cameo surface are made simultaneously.

✓ Functional fit of the intaglio surface can be obtained with direct relining.

✓ Both the occlusal relationship & external forms can be recorded using only the occlusal rim.

✓ The no. of patient visits to the dentist for denture fabrication do not differ from conventional fabrication.

CONCLUSION✓ The neutral zone is based on concept that for each

individual there is specific area where the function of the musculature will not unseat the denture.

✓ The neutral zone has not been given due importance but CD& RPD failures, orthodontics relapses ,orthognathic relapses can be attributed to neutral zone imbalance.

✓ Regardless of the method of treatment , any part of the dentition out of harmony with neutral zone wil result in instability, interference with function, degree of discomfort.

✓ Thus neutral zone must be evaluated as important factor before any changes in arch form & alignment of teeth.

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• Beresin Victor E.& Frank J. Schisser: The neutral zone in complete &partial denture,2nd edition.,1978.

• Beresin Victor: The neutral zone in complete denture. J .Prosthet.1975,34:373-383.

• Brill N, G. Tryde: The dynamic nature of lower denture space. J Prosthet Dent. 1965;15 :401-408.

• Cord J.F & A.A Grant: complete denture : clinical assessment. Br. Dent .J 2000;188:372_383.

• Faber Ben l: Comparsion of an anatomic verus physiologic method of posterior toth placement for complete denture.J Prosthet. Dent 1992;67:410-414.

• Fahmi F.M: The position of the neutral zone in relation to the alevolar ridge.J Prosthet Dent. 1992;67:804-809.

• Fahmy F.M : A study of importance of the neutral zone in complete denture. J Prosthet Dent . 1990;64:459-462.

• Lammie g.a: aging changes &the complete denture. J Prosthet Dent.1956;6:450-464.

• Lott F: Compasion of phsiologically & manually formed denture bases. J Prosthet Dent. 1965:15;227.

• Lott Frank& Bernard: Flange technique: an anatomic & physiologic approach to increased retention, function of dentures.J. Prosthet Dent. 1966;16:394-413.

• Ohkubo chikharo: Neutal zone approach for denture fabrication for a partial glossectomy.J.Prosthet Dent .2000;84:390-393.

Stephen G Alfanso:Using the neutral zone to obtain maxillomandibular relationship records for complete denture:J Prosthet Dent 2001;85:621-3.

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1

OBTURATORS

PRESENTED BY:

DR. SUDHIR MEENA

INTRODUCTION

During the past few year, there is increasingincidence of carcinoma associated to maxilla.Treating such patients results in a large bonydefect an communication between oral cavity andrespiratory airways.

It is prothodontist’s duty to handle suchchallenging cases and rehabilitate them to ensuremaximum benefit of speech deglutition estheticsand psychological aspect. In this way obturator isone of the most important prosthesis to handlesuch critical patients.

OBTURATORS Derived from Latin word obturare:- to sealDefinition:-“A prosthesis used to close acongenital or acquired tissue opening, primarily ofthe hard palate and/or contiguous alveolarstructures.”Function:- It helps the patient to feed orally rather than

to fed through nasogastric tube. Can be Used as a stent to hold dressing. It reduces the flow of exeudates. To keep the wound clean post surgically. Important for esthetics. Help to reshape or re-contour the palatal

vault.

CLASSIFICATION

1. Obturators for Congenital Defects of Palate: A simple base plate type to correct the

swallowing feeding and speech. Obturators with a tail, consisting of a speech

appliance or a speech aid prosthesis. The third type is an overlay or superimposed

denture.

2. Obturators for Acquired Palatal defects: Immediate temporary/surgical obturator. Treatment/Transitional/Interim obturator. Definitive or permanent obturator.

CLASSIFICATION OF MAXILLARYDEFECTS AS PROPOSED BY ARMANY 1978

Armany classified the maxillary defect into 6classes on the basis of the extension of the defectonto the palate and involving teeth and correspondingalveolar structure.

CLASS I: Unilateral mid half palatal defect.

CLASS II: Unilateral palatal defect distal to thecanine.

CLASS III: Bilateral extension of the defect from thepalate excluding all the teeth.

CLASS IV: Unilateral palatal half plus contralateralanterior to the first pre molar Aramany, Classification of Maxillary defects

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2

CLASS V: Bilateral palatal defect posterior to the first premolar

CLASS VI: Bilateral anterior palatal defect anterior to the second premolar.

PREOPERATIVE CONSIDERATIONS

Preoperatively, the prosthodontist isconcerned with four objectives; psychologicalsupport Dental management preoperativeimpression and suggestion for the surgeon.

Dental Management: Teeth that would normally be considered non

restorable or of no value may becomeextremely valuable abutment teeth for anobturator.

Generally the potential risk of ostoteoradionecrosis resulting from dental treatment in the maxilla is minimum and well potential value of the teeth as abutments for an obturator prosthesis.

As a general rule all the maxillary teeth that can be maintained should be in maxillectomy patient.

Surgical enhancements and suggestions forthe surgeon :

Suggestion to surgeon as many of thealveolar processes and teeth as possible shouldpreserve without compromising complete removalof the tumor.

Prognosis improves dramatically by savingteeth on surgical site because the functionalfulcrum line shifts to a more favorable position.

Line of resection be made through thesocket of extracted tooth. Instead of attempting tocut between roots of adjacent teeth.

Interproximal cuts will result in loss ofalveolar support for the tooth adjacent to thedefect and can lead to the loss of the toothpost surgically. The tooth adjacent to the defectis critical as an abutment for the obturatorprosthesis and its alveolar support must bemaintained.If the alveolar support of theremaining tooth immediately adjacent to thedefect is not adequate, it should be consideredfor extraction prior to the design andfabrication of the definitive obturatorprosthesis.

The clinician will also plan treatment for the patient for necessary preprosthetic surgery to remove epuli, reduce pendulous tuberosities, and relieve bony undercuts. Ideally, these are performed concurrently with the tumor resection.

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3

In this situation the most

favorable points of

retention would be on

the mesial of the central

incisor and the

distobuccal of the third

molar.

The most effective

placement of retention

for this situation is to

clasp the facial of the

canine on the defect

side and the distobuccal

of the terminal molar.

Representation of a

maxillectomy that

preserves the posterior

alveolar of the defect side.

Representation of the line

of resection extending

through the socket of an

extracted first pre-molar.

SURGICAL OPTURATORS

It is a base plate type appliance constructedfrom pre-operative impression cast andinserted at the time of resection.

Advantage: Provides a matrix on which the surgical

packing can be placed. Reduces oral contamination of the wound. Enables the patient to speak. The prosthesis lessens the psychological

impact of the surgery. May reduce period of hospitalization.

Following Guide lines should follow: The obturator should terminate short of the

skin graft mucosal junction. Prosthesis should be simple, light weight and

inexpensive. Normal palatal contour should be reproduced. Posterior occlusion should not be established

on the defect side. Surgical obturator for the edentulous patients

is wired to the zygoma or residual alveolarridge or screwed into the palate (into vomerbone angled posteriar length of screw in14-16mm).

Retentive woles for zygomatic wires are placed bilaterally with a no.8 round bur in the premolar area through the prosthesis flanges.For the prosthesis to sutured position ,the same bur is used to drill six holes in the periphery of the anterior and lateral flanges.

If the midpalate is crossed during operation , the vomer bone will not be present. To bone screws can then be placed in the residual alveolar process at antagonistic angles through the denture in the lateral hard palate(at the junction of alveolus and the palatal vault) will secure the prosthesis.

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A small plug of tissue conditioner over the head of the screw will keep the screw attached to the denture in the event the patient dislodges the denture during the post operative period.

After 7-10 days surgical obturators is removed and discarded.

Fabrication of surgical obturators: Impression: It is important to make an

accurate impression of the vestibular depth onthe resected side.

Minimal mouth preparation may be required. The surgeon and prosthodontist should

discuss the surgery and outline the proposedsurgical margins on maxillary cast.

The maxillary cast is altered to the proposedsurgical resection.

The teeth an alveolar ridge is trimmedmodestly to reduce the tension upon the skinand lip closure.

The wire retainers are adapted on suitableteeth. The prosthesis is processed inautopolymerizing acrylic resin.

Delivery and adjustment: The prosthesis is immersed overnight in a

disinfectant. If the surgery is more extensive than planned

it is often preferable to add an interim denturereline material to the prosthesis.

The packing placed superiorly into the surgicalsite will be support by the prosthesis andobturate any discrepancies between thesurgical margins and the prosthesis border.

6-8 days post surgically, the prosthesis andpacking are removed. Necessary adjustmentsare made. A new application of interimtreatment liner improves seal adaptation andcomfort.

Patient is recalled after 1 week after giving proper instruction.

During early stages of healing the prosthesis be worn at night.

Cleaning the defect:

Mucous and secretions should be removed using adequate size gauze pads socked in warm water and betadine solution. Petroleum jelly may be used to soften the dry mucous membrane.

INTERIM OBTURATOR Interim obturator bridges the gap between the

immediate surgical obturator and definitiveobturator.

It is constructed from the post-surgical impressioncast which has a false palate and false ridge andgenerally has no teeth.

This prosthesis will be in service for approximately2-6 months.

The tissue surface of the existing prosthesis isrelined and bulb is fabricated with softliner.

As the tissues contracts borders will beoverextended, and the patient will have difficulty inseating the prosthesis. The patient may return ,complaining that there is discomfort on the nonsurgical area of the maxilla or that the prosthesisis no longer retentive.

Adjustments should not be made to the non surgical side of the prosthesis because the problem is likely to be tissue changes in the surgical area shifting the entire prosthesis.

These contour changes are usually a combination of edema and tissue contracture.

The prosthesis must be worn constantly, remove only for cleaning of the surgical site or prosthesis.

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Reason for constructing interim obturator are:

A definitive prosthesis is not indicated until the surgical site is healed and dimensionally stable.

For some patient especially with large defects appropriate function and comfort cannot be sustained without construction of either a new prosthesis or a significant modification of immediate/delayed obturator.

Addition of anterior and possibly posterior dental teeth is possible.

PERMANENT OR DEFINITIVE OBTURATOR:

➢ 3-4 months after surgery consideration must be given to the construction of a definitive obturator.

➢ The timing of its construction depend on :

1. Progress of healing.

2. Prognosis for tumor control.

3. Use and timing of post surgical radiationtherapy.

4. Effectiveness of the present obturator.

5. Presence or absence of teeth.

During a impression procedure (withirreversable hydrocolloid) The patient head ispositioned forward then right and left laterallyand finally backward and forward again. Thisallow the impression material to flow into theundercut areas of hard and soft tissues.

An Accurate diagnostic cast is made, customtray is fabricated and border molding is done.

The clinician should always be aware thatmanual seating pressure of the tray duringborder molding and impression making shouldbe obliquely directed against the remainingalveolar ridge and not against the midpalate asis done when seating a normal maxillarydenture tray. Seating against the midpalateoften causes the tray to rotate into the surgicalsite and away from the residual alveolar ridgewithout operator awareness.

There is commonly a soft tissue undercut at the junction of the oral mucosa and skin graft that lines the maxillary cavity called a cicatricial linedor scarband.

In the case of preserved maxillary sinus wall and it has been grafted with skin, it is possible to use them for vertical support. They should be captured in the border molding of the surgical site.

Because of the instability of the obturator prosthesis , monoplane occlusion is recommended for the completely edentulous patient .

Because of the facial contracture on the surgical side, it is often necessary to place the anterior teeth in an end-to-end or reverse horizontal articulation .

If the posterior teeth were placed in reverse articulation bite, it may be necessary to remove the palatal half of these teeth.

The superior height of the bulb should terminate at the junction of the oral and respiratory mucosa or at the level of the nasal floor.

The impression should extend about 1cm. onto the oral surface of the residual soft palate.

Finally impression is completed with elastic impression material.

General Consideration regarding bulbdesign

A bulb is not necessary with a small toaverage size central palatal defect.

It is not necessary in surgical or immediateobturator.

It should be hollow to aid speech resonance,to lighten the weight.

It should not be so high as to cause the eyeto move during mastication.

Its should be one piece, if possible. Its should not be so large as to interfere with

insertion if the mouth opening is restricted.

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Two piece hollow obturator fabrication

The cast is waxed with 2mm. thicknessincluding the all the walls of the defects.Keeping open the palatal ridge side.

The false palate and ridge are shaped andcontoured in clay leaving an 2mm. thicknessof the wax pattern.

The two portions of the prosthesis areprocessed with heat cure resin in separately.

The processed obturator portion and lidportion are finished and lid is fixed overhollow bulb by cold cure resin at the margin

One piece hollow obturator: In this case shim is fabricated using three stops

for proper positioning by auto polymerizing resin. Now lid and bulb are cured in heat cure resin as

a single unit.Advantage

There are no lines of the demarcation of thedenture to discolour.The undercut area of the defect are thickenough to allow for the adjustment.

Silicone Rubber obturator: Base portion is fabricated with heat vulcanized

medical grade silicone rubber material. Fabrication of obturator with a resilient material

allow the radioactive material to be placed inclosed and intimate relationship to the tumorside.

Implant Retained Obturator : Implant provide retention enhance support and

improved stability of the obturator. Implant are placed and left buried 6-8 months in

the mucosa. Fabrication of definitive obturator can begin

when periimplant tissue are well healed.Prosthetic Speech Appliance of Children: Three types of speech aids

can be constructed for children:(1) An obturated with a palatal

–velar – pharyngeal portion. (2) A base plate type (3) An interior prosthesis which

contours the upper lip and improve the anterior the occlusion.

SOFT PALATE OBTURATOR PROSTHESIS➢A soft palate obturator or speech aid prosthesis isrequired for patients who have a resection of theirsoft palate or have a soft palate deficit from a cleftpalate .

➢Absence of soft palate tissue disrupts speech andswallowing by allowing nasal escape of air duringspeech and nasal reflux during swallowing.

➢A pharyngeal extension can be added to a dentureprosthesis within a few days after resection.

➢ A posterior extension is added to a dentureprosthesis to contact the pharyngeal wall when itcloses during speech and swallowing . Theextensions should be made at the level of the hardpalate and at the level of the most activemovement of the pharyngeal sphincter.

➢The inferior extent of the pharyngeal extensionshould be at or below the inferior aspect of thepharyngeal sphincter.

➢ The overall height of the extension should notbe more than 1cm .

Troubleshooting the soft palate obturator

Prosthesis feels to long:- The patient complains that they feels the prosthesis in the back of their pharynx

Hypernasality:- during swallowing pharyngeal constriction is usually more pronounced than in speech . As the difference between pharyngeal function in swallowing and speech become greater , the more likely it is that the patient will have hypernasal speech.

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PALATAL AUGMENTAITION PROSTHESES

➢ During speech swallowing or mastication, the the tongue contacts the palate and teeth to move the food bolus and articulate speech sounds into language .when the tongue or contiguous oral cavity structures are resected for neoplastic disease, the deficit in tongue function are related to loss of tissue bulk , denervation , and tethering of the remaining portion of the tongue.

➢ Placing a tissue conditioner material on the palatal surface of the denture can be used to create a functional impression of the residual mobile tongue made during swallowing

➢ Patient undergoing glossectomy may not be able to curl the tongue or approximate the anterior palate in the mid line to create an air channel . placing a groove in the anterior palate may create the necessary air channel.

PHILOSOPHY OF DESIGN

➢ There is no unanimity of thought with regards to this type of obturator design but three basic types of philosophy can be applied to most cases:- light steel are platinum gold paladium wire soldered to cast base; conventional infrabulge , circumferential , an cast variation clasps; and the hinged gate or swing-lock framework.

➢ Most clinicians are in agreement that there should be a retentive element as far from the defect as possible(Curtis and Beumer 1979).

➢ As the defect approaches the mid line theteeth farthest from the defects become moreinvolved in resisting displacement and thedirection of displacement become moreimportant. Lingual retentive arms on these teethwill serve to resist the downward displacementof the obturator extension and will disengage anupward movement.

➢ A dual path of insertion has been suggestedto use a weak anterior abutment forretention(King & Gay 1979)

➢If the resection and mouth opening allow , the obturator should cover as much of the lateral wall superiorly as possible(Zarv 1967; Beumer 1979; Brown 1968). This will decrease the lever arm of the displacing force to the teeth and provide an extremely valuable area of resistance to vertical displacement.

DESIGN POSSIBILITIES

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OCCLUSION IN EDENTULOUS

PATIENT

DR. SUDHIR MEENA

INTRODUCTION

Occlusion is the factor that is common to all branches of the dentistry.

According to G.P.T.-8 , It is defined as-

1. the act or process of closure of being closed or shut off,

2. the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues.

ARTICULATION

According to G.P.T – 8 , it is defined as the dynamic contact relationship between the occlusal surfaces of the teeth during function.

The force that develop during occlusal contacts , may vary in magnitude and direction, it must always be resisted by supporting tissue. Control of this resultant force is a basic and perplexing problem that is controversial, especially in the field of complete dentures.

Q. How occlusion in dentulous mouth

is different from that in an edentulous mouth ?

Natural Occlusion Artificial Occlusion

1. Each tooth individually is supported by periodontal tissue and has its proprioceptive feedback

1. All the teeth are supported by a common denture base that rests upon the slippery tissue i.e. mucosa

2.Each tooth can move independently and can migrate slowly to favorable occluding positions.

2. All the teeth move as a unit with the denture base.

Natural Occlusion Artificial Occlusion

3. Incising with the anterior teeth does not affect the posterior teeth.

3. Incising from anterior teeth can potentially cause tipping of the denture from the posterior.

4.Balancing side contact rarely found, if present considered as balancing side interference.

4. Balancing side contact (bilateral balancing) necessary for base stability.

5. Due to proprioceptive mechanism a person can avoid premature contacts and interferences.

5. Due to lack of proprioceptive mechanism any premature contacts and cuspal interference will dislodge the denture.

6. Malocclusion of natural teeth does not evoke any immediate response.

6. Malocclusion on artificial teeth evokes an immediate response and affects all the teeth and base.

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Natural Occlusion Artificial Occlusion

7. Horizontal thrusts on one side during mastication are well tolerated and affect only the side involved.

7. The effect is bilateral and is usually traumatic in nature.

8. Molars are the power points of masticatory force , esp. II molars which are important for chewing of tough food.

8. Chewing from II molar region wil shift the denture base if it is on inclined foundation .

REQUIREMENTS OF COMPLETE DENTURE OCCLUSION

The difference between the natural and artificial teeth and the requirements for artificial occlusion make it necessary to consider the dentist created occlusion as an unique problem.

As we all know that mandibular dentures are inherently less stable than the maxillary dentures, so the occlusal design and the positions of the lower occlusal units should be given FIRST preference.

Acc. To Ortmann (1971) the requirements for complete denture occlusion are –

Stability of occlusion in centric relation;

Balanced occlusion for eccentric contacts;

Unlocking of the cusps mesiodistally to accommodate the inevitable settling of the denture base;

Control of horizontal force by buccolingual cusp height reduction according ridge;

Functional balance by favourable tooth to ridge crest relation;

Cutting and shearing efficiency;

Anterior clearance of teeth during masticatory function;

Minimal occlusal stop areas for reduced pressure during function.

REQUIREMENTS OF THE INCISING UNITS

1. Should be sharp to cut efficiently.

2. Should be out of contact during mastication.

3. Should have as flat an incisal guidance as is possible.

4. Should have horizontal overlap to allow for setting of the bases.

5. Should engage only during protrusive incising function.

REQUIREMENTS OF WORKING OCCLUSAL UNITS

1.Should be efficient in cutting and grinding.

2.Should be narrow buccolingually to decrease work force transfer to denture foundation.

3. Should be over the ridge crest or slightly lingual to it , for lever balance.

4.Should have surface to transmit occlusal force vertically.

5.Should center the work load anteroposteriorly on the denture foundation.

6.Should present a occlusion as nearly parallel to the mean foundation plane as is possible.

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REQUIREMENTS OF THE BALANCING OCCLUSAL UNITS

1. Should contact in 2nd molar region when the incising units contact during function.

2. Should contact at the end the masticatory stroke when the working units contact.

3. Should have smooth gliding contact for lateral and protusive sliding extrusions

Types of Posterior Teeth1. Anatomic teeth: Acc. To G.P.T- 8 , this is defined as

artificial teeth that have cuspal inclination greater than 0 degree, and which tend to duplicate natural teeth in appearance.

(a) Standard anatomic teeth: Those anatomic teeth which have cusp inclines of approximately 33o or more and closely resemble natural teeth.(b) Modified or semi anatomic teeth: Those anatomic teeth which have cusp inclines lesser than 33o (I.e. less steep) and they look somewhat like natural teeth.

2. Non-anatomic teeth: Non-anatomic teeth are flat with no cusp heights to intercuspate with opposing teeth. Their occlusal surface has various designs of flat planes and sulci to enhance their masticatory efficiency.

ANATOMIC TEETH

The natural teeth in dentulous mouth function in harmony with their opposing member giving efficient and comfortable mastication.

However in edentulous mouth these same teeth can cause trauma , discomfort, and instability to the bases because of the horizontal components they generate.

The basic problem initially is the coordination of these cuspal inclines to harmonize with the mandibular movements. Even if this is done , with meticulous records on adjustable articulator, it can not exist for long when transferred to the mouth.

1. It is mandatory to use an adjustable articulator.2. Both centric and eccentric records need to be made

for articulator adjustments.3. Mesio – distal locking will not permit settling of

the bases without development of horizontal forces .

PROBLEMS OF UNMODIFIED ANATOMICTEETH

4. Carefully balanced lateral positions become unbalanced with settling.

5. The bases need prompt and frequent refitting to keep the occlusion harmonious.

6. The presence of cusp generate more horizontal force during mastication.

7. Tooth contacts do not always occur in the same horizontal position (I.e. the centric recorded). Many jaw closures also occur anterior and lateral to this centric position. But due to prominence of the cusps, there is no freedom of tooth contact during such jaw closures, hence deflective forces act on the base during such jaw closures leading to base instability and increased residual ridge resorption.

NONANATOMIC TEETH

Acc. To G.P.T – 8 , nonanatomic teeth are defined as artificial teeth with occluding surfaces that are not anatomically formed. The term nonanatomic as applied to artificial posterior teeth , and especially their occlusal forms , means that such teeth are designed in accordance with the principles rather than from the viewpoint of anatomic teeth with flat occlusal surfaces set to flat occlusal plane.

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ADVANTAGES OF NON-ANATOMIC TEETH

1. Versatility of use, hence can be used in class II and III jaw relations also.

2. They are used more easily when variation in the width of upper and lower jaws indicate a cross bite setup.

3. Centric occlusion is more of an area and less of a precise point in these teeth hence they allow closure of jaws over a broad contact area.

4. Minimal horizontal pressures are created because of elimination of inclined planes.

5. Zero degree teeth permit the use of a simplified and less time consuming technique and offer greater comfort and efficiency for longer duration.

6. The accommodate better to the inevitable negative changes in the ridge that occur with aging.

According to the Jones ,the use of zero degree teeth should not only be limited to the patients with unfavorable prognosis, and their uses should be extended to include those patients with favorable prognosis, because those mouths which are favorable today will get unfavorable a decade or two later.

We must not forget the De Van's famous lines that we be as concerned with preserving what is left as with the restoration of what is missing.

DISADVANTAGES OF NON-ANATOMIC TEETH

1.Since these teeth are flat hence occlusion occurs only in 2 dimensions , but the mandible, due to the incline of condylar path, moves in three dimensional arcuate path.

Fig 13.25 , 238, winklr

2. Due to flatness of occlusion, bilateral and protrusive balance is not possible.

But it can be made to develop in monoplane occlusion with the help of balancing ramps, tripodization with tilting the 2nd molars, and by the incorporation of compensating curve.

3. They appear dull and unnatural to some patients and may create a psychological problem concerning function and esthetics.

4. The vertical component present in mastication and nonfunctional movements is not provided for , so that this form loses shearing efficiency.

5. They cannot be corrected much by occlusal grinding without impairing their efficiency.

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6. They don't function efficiently unless the occlusion surface provides cutting ridges and generous spillways (sluiceways).

7. If for phonetic and esthetic demands, a deep vertical overlap is required and overjet cannot be increased beyond a limit, then the monoplane occlusion has potential for anterior interference during, due to absence of cusp lift.

BALANCE AS RELATED TO COMPLETE DENTURE

When forces act on a body in such a way that no motion results, then there is balance or equilibrium. This should be the primary aim of the dentist I.e. to achieve a stable base. In order to do so the following axioms have to be followed: by Sears

1. The wider and larger the ridge and closer the teeth are to the ridge, the greater the balance.

2. Conversely, the smaller and narrower the ridge and farther the teeth from the ridge, the poorer the balance.

4. The wider the ridge and narrower the teeth buccolingually, the greater the balance.

5. Conversely, the narrower the ridge and wider the teeth, the poorer the balance.

6. The more lingual ( with in limits provided by the tongue) the teeth are placed in relation to alveolar ridge crest, the greater the balance.

7. The more buccal the teeth are positioned, the poorer the balance.

TYPES OF BALANCE

Balance may be lever or occlusal and unilateral, bilateral, or protrusive.

1. UNILATERAL LEVER BALANCEThis is present when there is balance of the base on its supporting structures when bolus food is interposed between the teeth on one side and a space exits between the teeth on the opposite side. Following points encourages the lever balance-

a) Teeth placement should be such that to direct the resultant force on the functioning side over the ridge or slightly lingual to it.

b) Having the denture base cover as wide an area on the ridge as possible.

c) Placing the teeth as close to the ridge as other factors will permit.

d) Using as narrow a buccolingual width occlusal food table as practical.

This is present when the occlusal surfaces of teeth on one side articulate simultaneously , as a group , with a smooth uninterrupted glide.

2. UNILATERAL OCCLUSAL BALANCE

3. BILATERAL OCCLUSAL BALANCE

This is present when there is equilibrium on both sides of the denture due simultaneous contact of the teeth in centric and eccentric occlusion. It requires a minimum of three contacts to establish a plane of equilibrium. This balance is dependent on the interaction of the incisal guidance, plane of occlusion, angulations of teeth, compensating curve, and condylar guidance.

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4. PROTRUSIVE OCCLUSAL BALANCE

This is present when the mandible moves essentially forward and the occlusal contacts are smooth and simultaneous in the posterior both on right and left sides and on the anteriors.

It is slightly different from bilateral balance in that it requires a minimum of three contacts, one on each side posteriorly and one anteriorly, and is dependent on interaction of the same factors as bilateral occlusal balance.

This entire concept of balanced occlusion must be considered in terms of the following:

1) The tooth size and position in relation to the ridge size and shape.

2) The extent of denture base coverage.3) Occlusal balance with stable contacts at

the retruded border position and in an area (long centric) anterior to it.

4) Right and left eccentric occlusal balance by simultaneous contacts at the limit of functional and parafunctional activity.

5) Intermediate occlusal balance for all positions between centric occlusion and all other functional or parafunctional excursions to the right, left and protrusive.

this balance is probably the most important , as it allows for smooth uninterrupted tooth contacts in the dynamics of daily mandibular movements.

ADVANTAGES OF BILATERALLY BALANCED OCCLUSION

Prime gave the concept of “ ENTER BOLUS EXITBALANCE” which implies that introduction of food

on one side will prevent the teeth of opposite side from contacting and hence occlusal balance is impossible during mastication.

However Sheppard (1964) later gave the concept of ENTER BOLUS ENTER BALANCE according to which even while chewing, the teeth cut through the bolus and come in contact with each other, for few fractions of a second. Hence the stability of the denture is maintained during various movements of mandible during chewing.

Moreover, the bilateral balanced occlusion is even more important during functional and the parafunctional activities like swallowing of the saliva, closing to seat the denture and bruxing of the teeth during times stress,etc.

Patient with balanced occlusal design do not upset the normal static , stable , and retentive position of their denture

Balanced occlusion thus will make such episode less damaging to the supporting structures during the times of stress.

FACTORS AFFECTING BALANCED OCCLUSION

As described by the Rudolph L.Hanau there are five factors involved in balanced occlusion of CD.

These factors are:

1. Condylar guidance

2. Incisal guidance

3. Plane of occlusion

4. Compensating curve

5. Inclination of the cusps.

Vincent r. Trapozanno (1963) criticized Hanau `s Five factors of occlusion , and concluded that only three factors out of five are important, viz, Condylar guidance, incisal guidance, and cusp angulation.

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CONDYLAR GUIDANCE

As defined by G.P.T-8, it is mandibular guidance generated by the condyle and articular disc traversing the contour of glenoid fossae.

There is controversy that whether condylar path is precise or not. However some studies says some thing different.

Kurth (1954) claims that condylar path is not same for varying incisal guidance.

Payne (1951) has shown that mandible can move to follow steep cusps, modified cusps and zero degree teeth when there is posterior harmony and no anterior interference is present.

Weinberg (1976) has demonstrated that the condylar path may vary with the variable pressure of occlusion.

As stated by Hanau ( and agreed by Trapozzanno) the condylar guidance is the factor edentulous patient presents and can no way be modified by the operator.

Factors which determine the registration of condylar guidance are –

a) Shape of the bony contour of glenoid fossae;

b) Muscles attaching to the mandible ;

c) Limitation of the movement by attached ligaments.

d) The registration method used. i.e. If registration method require bases to rest on tissue of mandible and maxilla, the REALEFF can modify the recordings.

INCISAL GUIDANCEAs defined by G.P.T- 8 it is the influence of the

contacting surfaces of the mandibular and maxillary anterior teeth on mandibular movements.

And incisal guide angle is defined as the angle formed by the intersection of the plane of occlusion and a line within the sagittal plane determined by the incisal edges of the maxillary and mandibular central incisors when the teeth are in maximum intercuspation.

As it is more near to masticating teeth surfaces ( as compared to condylar guidance) it has a dominant influence on contacting surfaces of the teeth posterior to it.

In C.D construction it is largely under the control of the dentist , the limitations governing it are-

a) Ridge relation,

b) Arch shape,

c) Ridge fullness

d) Interridge space

e) Phonetics and esthetic requirements of the patients.

Originally Hanau described 2 incisal guidance viz sagittal protrusive I.G and lateral I.G.

Coming to lateral I.G, is determined by considering the relationship of all incisors and cuspids , both maxillary and mandibular ( in pure right and left lateral movements ) .

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For C.D construction Incisal guidance should be as flat as esthetics and phonetics will permit.

Trapozanno( 1963) defined it as the steepest angle formed with the horizontal plane by drawing a line between the incisal edges of the maxillary and mandibular incisors and cuspids of both right and left segments when the teeth are in centric occlusion

PLANE OF OCCLUSION

Acc. To G.P.T -8 it is defined as the average plane established by the incisal and occluding surfaces of the teeth . Generally , it is not a plane but represents planer mean of the curvature of these surfaces.

This plane is established in anterior region by the height of lower cuspid which coincides with the commissure of the mouth and in the posterior region by the center ( Winkler) or junction of posterior and middle third of the retromolar pad ( Boucher).

These landmarks also provide a physiologically and functionally acceptable anteroposterior inclination of the occlusal plane that is nearly parallel to the lower mean foundation plane.

These landmarks also creates an occlusal plane essentially parallel to the ala-tragus line( Camper`s plane).

Okane (1979) showed that when occlusal plane is parallel is to the ala – tragus line, the closing force during maximum clenching was greater than when it was altered by +/- 5 degree.

• Its position can be altered only slightly without creating serious functional problem.

• Its role is not as important as are the other determinants.

COMPENSATING CURVE

Acc. To G.P.T -8 , it is defined as (1) the anterio-posterior curving (in median plane) and the medio-lateral curving ( in frontal plane) within the alignment of occluding surfaces and incisal surfaces of artificial teeth used to develop balanced occlusion.

(2) the arc introduced in the construction of complete denture to compensate for the opening influence produced by the condylar and insical guidance's during lateral and protrusive mandibular excursive movements.

It is determined by the inclination of the posterior teeth and their vertical relationship to the occlusal plane so that the occlusal surface results in a curve that is in harmony with the movement of the mandible as guided by the condylar path posteriorly and incisal guidance anteriorly.

Fig 6 , 131 ortman article Or 1328 245 wink

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A steeper condylar path requires a steeper compensating curve .A lesser compensating curve for steeper condylar guidance would result in steeper incisal guidance acting as anterior interference, causing loss of molar balancing contacts.

The primary function thus of compensating curve is to provide balancing contacts for protrusive mandibular movements.Without this curve it would be necessary to incline the entire occlusal plane at an angle.

With compensating curve it is possible to produce eccentric balance in monoplane occlusal scheme, which is otherwise said to be deficient in this.

The compensating curve incorporated in a properly oriented plane of occlusion starts with the first molar by raising it at distal and continuing this initiated curve with further rise in the 2nd molar. The radius of the curve is the result of the guiding influence of the angle of the incisal and condylar guidance.

Acc. to Boucher (1963) the value of compensating cusp is that it permits an alteration of the cusp height without changing the form of the manufactured teeth .It is means for making cusps longer or shorter to produce steeper or flatter cusps, simply by inclining the long axis of the teeth to conform to the end guidances.

It is also a determinant, as it modifies the effect of the plane of occlusion and the compensating curve.

The angulation of the cusp is more important than te height of the cusps per se.

The mesiodistal cusp heights that interdigitate lock the occlusion so that reposition of the teeth due to setting of the base cannot take place.To prevent this problem, it is advocated that all mesiodistal cusp heights be eliminated in anatomic type teeth.With the teeth so modified, only the buccolingual inclines need be considered as determinants of balanced occlusion.

INCLINATION OF THE CUSPSOut of the five factors , only four can be

controlled by the dentist.

The incisal guidance and plane of occlusion can be altered but only slightly because of esthetic and phonetic limitations.

The main factors which can be used and changed effectively are compensating curve and inclinations of the cusps of the teeth .

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TYPES OF OCCLUSION SCHEMES

Now let us discuss the three main occlusal schemes i.e Monoplane occlusion, Classical bilaterally balanced occlusion , and Lingulized occlusion .

It is of interest to note that none of the occlusal scheme has been proved to be superior to other (for all presenting conditions of edentulous mouths), although one type of scheme may offer some advantages over other.

MONOPLANE OCCLUSION

Acc. To G.P.T -8 ,it is defined as an occlusal arrangement wherein the posterior teeth have masticatory surfaces that lack cuspal height .

Hall (1929) is credited for the introduction of Zero degree teeth calling them inverted cusp tooth, but these teeth have the problem of clogging of food in the depressions onto the occlusal surfaces.

Myerson later designed a cusp less teeth with series of transverse buccolingual ridges and sluiceways between them.

ADVANTAGES OF MONOPLANE OCCLUSION / ZERO DEGREE TEETH

1. Versatility of use, hence can be used in class II and III jaw relations also.

2. This is used more easily when variation in the width of upper and lower jaws indicate a cross bite setup.

3. Centric occlusion is more of an area and less of a precise point in these teeth hence they allow closure of jaws over a broad contact area.

4. Minimal horizontal pressures are created because of elimination of incline plane.

5. Zero degree teeth permit the use of a simplified and less time consuming technique and offer greater comfort and efficiency for longer duration.

6. They accommodate better to the inevitable negative changes in the ridge that occur with aging.

As far as balanced occlusion is concerned in monoplane occlusion two important concepts prevail-

A) Non Balanced occlusion (in centric relation only) E.g Neutrocentric concept.

B) Balanced occlusion in centric relation and lateral excursions This can be achieved with the use of compensating curve, balancing ramps, Tripodization by tilting the 2nd maxillary and mandibular molars, and using monoplane with zero overbite ( but this will compromise phonetics and esthetics.)

NEUTROCENTRIC CONCEPT

This is an important example in first category.

Acc. to DeVan the main objectives of neutrocentric concept are-

I – Neutralization of the inclines and,

II – Centralization of the occlusal forces acting on the denture foundations.

In order to attain these objectives, it is necessary to reduce the size and number of teeth and to abandon attempts to secure balancing contacts in eccentric positions beyond the range of masticatory stroke.

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The neutrocentric concept should not be identified with that of the advocates of nonanatomic teeth, who merely dispense with cuspation.

It is dangerous to discard cusps without neutralizing other factors of articulation, that is;

1)Orientation of occlusal plane.2)Compensating curve.3)Incisal guidance.

These factors concern inclines of arrangement of teeth, whereas cusps are related to inclines of form.

There is only one factor of articulation which cannot be neutralized, ie., the condylar guidance, but which fortunately can be circumvented by a plan involving neutrocentric concept.

If the patient can be persuaded to avoid incising with artificial teeth, there is no need to be concerned with the sagittal condylar incline.

When incision is avoided and no projection exists above and below the occlusal plane, the condylar inclination on the articulator may be set at zero.

Stability is a tooth-bone relationship while retention is a tooth-mucosa borne relationship.

Stability is not necessary for function; a denture to function needs only to be retained.

When a denture is unstable however, the patient may not be able to maintain the initial chewing performance due to chaffing and irritation of the mucosa.

Furthermore, an unstable denture may prove traumatic to the ridge bone, in time causing its resorption.

According to DeVan, the five factors involved in the relation of the teeth to dental foundation are:

(a) POSITIONThere is probably no single tooth factor as important as

position.

Acc. to DeVan posteriors should be positioned in as central position on the foundation as allowed by the tongue, this way denture will be more stable due to enhanced lever balance, and more of the osseous foundation will be saved by the harmful tensile and shearing forces acting on bone and the overlying mucosa.

Clinical observations support the opinion that balancing contacts in eccentric positions don't nullify the unstabilizing effect of an off-ridge setup

Acc. to DeVan the employment of lateral balance intensifies rather than alleviates the problem of stabilizing the denture.

Eccentric balance does help to maintain retention; but if the use of inclines is essential for its establishment, then bilateral balance causes a decrease in stability.

Balancing inclines shift the denture farther toward the side of the mastication, preventing its dislodgement while increasing its side displacement.

B) PROPORTION

DeVan recommends reduction in the proportion of the artificial teeth as compared to size of natural teeth.

Reduction in proportion is necessary to develop centralization of forces, Reduction of frictional forces developing on occlusal surfaces which will transfer to the underlying mucosa and bone.

Reduction by 40% in width is possible without serious diminution of the food table.

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C) PITCH

Pitch is synonymous with inclinations or tilt .

In neutrocentric concept the plane of occlusion should be oriented so that it is midway and parallel to mean foundation planes of the maxilla and the mandible.

The compensating curve should be neutralized so that posteriors are placed on a plane rather than on spherical surface.

D) FORM

Artificial posterior teeth should be devoid of projecting cusps.

Contacting occlusal lines should be on a single plane.

This arrangement will avoid interference from TMJ and their inclines.

E) NUMBER OF TEETH

DeVan recommends reduction in no. of teeth from 8 per denture to 6 per denture.

This will aid in stability by freeing the lower ridge molar incline of occlusion.

Elimination of 2nd molar will result in establishment of centralization and reduction in occlusal area.

The 2nd category in monoplane occlusion involves bilateral balance in centric and eccentric relations.

A) WITH COMPENSATING CURVE

Acc. to this concept –a) No. of posterior teeth should be 3, i.e. mandibular

1st premolar should be omitted.

b) Antero-posterior comp. curve begins at the DMR of the 2nd premolar and continues till 2nd molar.The amount of this curve is dependent on steepness of the condylar guidance, but is rarely more than more than 20 degree from horizontal. This curve is used to provide the needed tooth structure for protrusive balancing contacts

c) Mediolateral compensating curve is also needed to achieve lateral balanced contacts. This curve is initiated from first replacement tooth and continued till the second molar. The degree to which the facial cusps are elevated to establish this curve will vary with the condylar and incisal guidances. The curve usually does not exceed 5-10 degree.

B) WITH BALANCING RAMPSBalancing ramps provide a tripodization of the denture

base.

As the patient moves the mandible from centric relation to protrusive or lateral positions, there is smooth contact anteriorly on the teeth and posteriorly on the ramps.

The balancing contacts give improved horizontal stability to the dentures. Esthetics and phonetics are greatly enhanced because there is more freedom in placing anterior teeth.

Nimmo art fig 2

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The ramps can be developed after the final try-in of the waxed dentures or at the time of clinically remounting the dentures at the insertion appointment

The procedure is performed on a properly adjusted articulator.

This technique can be applied to existing dentures by clinical remount.

Working contacts Balancing contact

C) WITH TILTING THE SECOND MOLARS

Acc to C G Porter, mandibular second molar is inclined to provide contact with maxillary dentures in all excursions.

The maxillary molars are also inclined but left out of centric contact.

He recommended the use of French modified posterior teeth which have sub-occlusal surfaces of mandibular buccal cusps directing the occlusal force downward and lingually.

LINGUALIZED OCCLUSIONAcc. to GPT-8, lingualized occlusion is defined as the

form of denture occlusion in which the maxillary lingual cusps articulate with the mandibular occlusal surfaces in centric, working and balancing mandibular positions.

Although S. H. Payne(1941) has being credited for being the first one to describe, it was Gysi who used this scheme approximately 20 years earlier.

The advantages of lingualized occlusion are:

1) Occlusal forces can be directed lingually without placing the teeth lingually

2) It is specially useful where esthetic demands of the patient is high but presenting oral conditions indicate non-anatomic teeth, e.g., severe ridge resorption, class II & III jaw relationships and highly displaceable supporting tissues.

3) The chewing efficiency is comparable to anatomic (semi) and definitely superior to zero degree teeth.

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4) As mesiodistal locking is eliminated by grinding the transverse ridges of the cusp teeth, freedom is provided in the occlusion to accommodate for the settling of denture base.

5) The lateral thrust control (during functional and para-functional movements) is provided by grinding the buccolingual inclines, which is based on the shape and prominence of the ridge and its ability to withstand lateral forces.

6) The para-functional habits are usually confined to a zone of activity around centric relation.

The lingualized occlusion provides for smooth balancing contacts with excursive movements of 2-3mm around centric relation, owing to creation of common central fossa in mandibular posteriors by selective grinding of transverse ridges in the process of mesiodistal unlocking.

CHARACTERISTICS ANATOMIC LINGUALIZED

NEUTROCENTRIC

ESTHETICS + + -

EASE OFPENETRATION

+ + -

DENTURE STABILITY (in parafunct movt )

+ + -

SIMPLER TECHNIQUE - + +DECREASED LATERAL FORCES

- + +

EASE OF ADJUSTMENT

- + +

CLASS II & III CASES - + +STABILITY WITH CENTRALIZED & NEUTRALISED FORCE

- + +

PLEASURE CURVEIn 1937, Dr. Max Pleasure described a reverse occlusal scheme in which the posterior teeth are set with buccal tilt providing total lever balance during function.

But with this scheme, there is no buccal rise on occlusal surface, so a balancing contact is not possible.

Later Pleasure himself modified his occlusal scheme by incorporating both a buccal tilt for lever balance, and lingual tilt for occlusal balance.

This is called Pleasure curve.

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Buccal tilt is given at the premolars , no tilt at first molars and a lingual tilt to second molars.

This scheme is specially beneficial for patients with class II jaw relation.

The lever balance obtained in the premolar area is nearly at the anterio-posterior center of the denture foundation coinciding with the zone where class II patient functions during light to heavy intermediate chewing.

The first molar occlusal surface directs the force directly to the ridge .

Lingual tilt of the second molar provides a buccal rise to its occlusal surface to provide for a lateral balancing contact.

A compensating curve is developed in the first and second molar area to provide for protrusive balance.

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OCCLUSAL CONSIDERATIONS

FOR IMPLANTSUPPORTED PROSTHESIS

DR. SUDHIR MEENA

INTRODUCTION

The clinical success and longevity of endosteal dentalimplants as load-bearing abutments are controlled largely by themechanical setting in which they function. The treatment plan isresponsible for the design, number and position of the implants.After achievement of rigid fixation, proper crestal bone contour,gingival health, mechanical stress, and/or strain beyond the physicallimits of hard tissues have been suggested as the primary cause ofinitial bone loss around implants. After successful surgical andprosthetic rehabilitation with a passive prosthesis, such noxiousstresses and loads applied to the implant and surrounding tissuesresult primarily from occlusal contacts. Complications (prostheticand/or bony support) reported in follow-up studies underlineocclusion as a determining factor for success or failure.

The choice of an occlusal scheme for implant-supportedprostheses is broad and often controversial. Almost all concepts arebased on those developed with natural teeth and are transposed toimplant support systems with almost no modification. No controlledclinical studies have been published comparing the various implantocclusal theories.

RISK FACTORS - Implant prostheses with extendedcantilevers have been successful, however, biomechanical factorsclearly demonstrate an increased risk.

Biomechanical parameters are excellent indicators of theincreased risk because they are objective and can be measured. Onecan determine which condition presents greater risk, and by howmuch the risk is increased. Hence the occlusal concepts developed inthis seminar stem from biomechanical risk factors.

The prosthodontist has specific responsibilities to minimizeoverload to the bone-to-implant interface. These include a properdiagnosis leading to a treatment plan providing adequate support,based on the patient’s individual force factors, a passive prosthesis ofadequate retention and form and progressive loading to improve theamount and density of the adjacent bone and further reduce the riskof stress beyond physiologic limits. The final element is thedevelopment of an occlusal scheme that minimizes risk factors andallows the restoration to function in harmony with the rest of thestomatognathic system.

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TERMINOLOGY(GPT 1999)

Anterior protected articulationA form of mutually protected articulation in which the vertical

and horizontal overlap of the anterior teeth disengage the posteriorteeth in all mandibular excursive movements.

Balanced articulationThe bilateral, simultaneous, anterior, and posterior occlusal

contact of teeth in centric and eccentric positions

Canine protected articulationA form of mutually protected articulation in which the vertical

and horizontal overlap of the canine teeth disengage the posterior teethin the excursive movements of the mandible.

Implant ProsthodonticsThe phase of Prosthodontics concerning the replacement of

missing teeth and / or associated structures by restorations that areattached to dental implants.

Lingualized occlusionFirst described by S. Howard Payne, DDS, in 1941, this form

of denture occlusion articulates the maxillary lingual cusps with themandibular occlusal surfaces in centric working and nonworkingmandibular positions. The term is attributed to Earl Pound.

Payne SH. A posterior set up to meet individual requirements.Dent. 1941; 47:20-2.

Pound E. Utilizing speech to simplify a personalized dentureservice. J. Prosthet Dent. 1970;24:585-600.

LinguocclusionAn occlusion in which a tooth or group of teeth is located

lingual to its normal position.

Mutually protected articulationAn occlusal scheme in which the posterior teeth prevent

excessive contact of the anterior teeth in maximum intercuspation,and the anterior teeth disengage the posterior teeth in all mandibularexcursive movements.

Occlusion (1645)1: The act or process of closure or of bring closed or shut off

2 : the static relationship between the incising or masticating surfacesof the maxillary or mandibular teeth or tooth analogues

Spherical form of occlusionAn arrangement of teeth that places their occlusal surfaces on

the surfaces of an imaginary sphere (usually 8 inches in diameter)with its center above the level of the teeth (GPT-4).

IMPLANT PROTECTIVE OCCLUSION (IPO)

A proper occlusal scheme is a primary requisite for long-termsurvival, especially when parafunction or marginal foundations arepresent. A poor occlusal scheme both increases the magnitude ofloads and intensifies mechanical stresses (and strain) at the crest ofthe bone. Implant Protective Occlusion (IPO) was previously knownas medial positioned-lingualized occlusion. This occlusal conceptrefers to an occlusal plane that is often unique and specificallydesigned for the restoration of endosteal implant, providing anenvironment for improved clinical longevity of both implant andprosthesis.

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OCCLUSAL CONSIDERATIONS

Natural Tooth vs. Implant Mobility:In comparison to an implant, the support system of a natural tooth is

designed to reduce the forces distributed at the crestal bone. The fibroustissue interface (periodontal ligament) surrounding natural teeth acts as aviscoelastic “shock absorber”, serving to both decrease the magnitude ofstress to the bone at the crest, as well as extend the time in which the load isdissipated.

The presence of a periodontal membrane around natural teethsignificantly reduces the amount of stress transmitted to the bone,especially at the crestal region. Comparedwith a tooth the direct bone interface with animplant is not as resilient, so the energyimparted by an occlusal force is not partiallydissipated (the displacement of theperiodontal membrane dissipates energy), butrather transmits a higher intensity to thecontiguous bone. An analogy of this is hittinga nail with a steel hammer compared with arubber hammer.

The mobility of a natural tooth can increase with occlusaltrauma. This movement dissipates stresses and strains otherwiseimposed on the adjacent bone interface or the prosthetic components.After the occlusal trauma is eliminated, the tooth can return to itsoriginal condition with respect to the magnitude of movement. Mobilityof an implant can also develop under occlusal trauma. However, afterthe offending element is eliminated, an implant rarely returns to itsoriginal rigid condition. Instead, its health is compromised, and failureis usually eminent.

The width of almost every natural tooth is greater than the widthof the implant used to replace the tooth. The greater the width of atransosteal structure (tooth or implant), the lesser magnitude of stresstransmitted to the surrounding bone. The cross-section shape of thenatural tooth at the crest is biomechanically optimized to resist lateral(buccolingual) loads because of the tooth’s bending fracture resistance(moment of inertia) and the direction of occlusal forces. Implants arealmost all round in cross-section, which is less effective in resistinglateral bending loads and consequent stress concentration in the crestalregion in the jaws.

The elastic modulus of a tooth is closer to bone than any of thecurrently available dental implant biomaterials. The greater theflexibility difference between two materials (metal and bone or toothand bone), the greater the potential relative motion generated betweenthe two surfaces at the transosteal region. Hence under similarmechanical loading conditions, implants generate greater stresses andstrains at the crest of bone compared with a tooth.

The precursor signs of occlusal trauma on natural teeth areusually reversible and include hyperemia and occlusal or coldsensitivity. Condition often results with the patient seekingprofessional treatment to reduce the sensitivity, usually by occlusaladjustment and a reduction in force magnitude. If the patient does nothave an occlusal adjustment, the tooth often further increases inmobility to dissipate the occlusal forces. If the patient still fails to seekprofessional treatment for the increased mobility, the tooth mayorthodontically migrate away from the cause of the occlusal stress.Even excess tongue or oral habits can cause tooth migration awayfrom the causative element.

The initial reversible signs and symptoms of trauma onnatural teeth do not occur with endosteal implants. The magnitude ofstress may cause bone microfractures, place the surrounding bone inthe pathologic loading zone causing bone loss, and lead to themechanical failure of prosthetic or implant components. Unlike thereversible signs and symptoms exhibited by natural teeth, implantbone loss or unsecured restorations most often occur without anywarning signs. Implant occlusal sensitivity is uncommon andsignifies more advanced complications. The loss of crestal bonearound the implant is not reversible without surgical intervention andresults in a decreased implant support and increased sulcus deptharound the abutment. As a result, unless the density of boneincreases or the amount or duration of force decreases, the conditionis likely to progress and even accelerate until implant loss. Inaddition, implants cannot move orthodontically away from theoffending force.

The tooth can show clinical signs of increased stress such asenamel wear facets, stress lines, lines of Luder (in amalgam fillings),cervical abfraction, and pits on the cusps of teeth. An implant crownrarely shows clinical signs other than fatigue fracture. As a result,fewer diagnostic signs are present to warn the prosthodontist to reducethe stress on the support system.

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When teeth oppose each other, an interference perception isapproximately 20m. An implant opposing a natural tooth has aninterference perception of 48m, therefore more than twice as poor.An implant opposing implant has an interference perception of 64m,and when a tooth opposes an implant overdenture the awareness is108m (5 times poorer than teeth opposing each other). As a result,premature occlusal contacts on teeth are usually associated with amodification of arc of closure and with a decreased force, beforecentric occlusion or full interdigitation. In addition, the mandible mayclose in a different position to avoid the premature contact and resultin centric occlusion different from centric relation occlusion.Unfortunately, because of the decreased occlusal awareness ofimplants, the premature contact does not trigger such as an adaptation.In addition, premature contacts are often on smaller areas of load andtherefore result in greater stress (S=F/A). They are most often oninclines of posterior teeth, which also generates an angled load ofgreater stress to the implant bone interface.

Implants and teeth also have different proprioceptiveinformation relayed by both entities. Teeth deliver a rapid, sharp painsensation under high pressure that triggers a protective mechanism. Onthe other hand, implants deliver a slow, dull pain that triggers adelayed reaction, if any.

Clinical evidence of occlusal trauma on teeth includes anoverall increase in the periodontal membrane thickness and anincreased radiopacity and thickness of the cribriform plate around thetooth, observed on radiographs and not just localized at the crest.There are no generalized radiographic signs around an implant underexcess occlusal force, except at the crestal region, which demonstratesbone loss but may be misdiagnosed as periimplant disease frombacteria.

The tooth slowly erupts into occlusion and is present in the mouthfrom childhood. The surrounding bone has developed in response to thebiomechanical loads. The permanent teeth are gradually introduced, whileothers are present. Hence periodontal tissues have had time to organize inorder to sustain increasing loads, including those brought to bear by anattached prosthesis. The only progressive bone loading around an implantis performed by the prosthodontist, and in a much more rapid and intensefashion.

A lateral force on a natural tooth is rapidly dissipated away fromthe crest of bone toward the apex of the tooth. The healthy, natural toothmoves almost immediately 56 to 108m and pivots two-thirds turn towardthe tapered apex with a lateral load. This action minimizes crestal loads tothe bone. An implant does not exhibit a primary immediate movement, buta secondary movement 10 to 50m under similar lateral loads. In addition,it does not pivot (as a tooth) toward the apex but instead concentratesgreater forces at he crest of surrounding bone. Therefore if an initialangled load of equal magnitude and direction is placed on both an implantand a natural tooth, the implant sustains a higher proportion of the loadthat is not dissipated to the surrounding structures.

The natural tooth, with its modulus of elasticity similar tobone, periodontal ligament, and unique cross-sections and dimensionsconstitutes a near perfect optimization system to handle stress. In fact,the stress is handled so well, bacteria-related disease is the weak link.An implant handles stress so poorly (capturing the stress at the crestof the ridge), has an elastic modulus 5 to 10 times that of bone, and isunable to increase mobility without failure that stress is the weakestlink in the system. As a result, ways to decrease stress are a constantconcern to minimize the risk of implants complications.

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Occlusion on Natural Teeth and Implants:There has been an ongoing controversy regarding whether a

rigidly fixated implant may remain successful when splinted to naturalteeth. Because the implant has no periodontal membrane, concernscenter around the potential for the “nonmobile” implant to bear thetotal load of the prosthesis when joined to the “mobile” natural tooth.The actual mobility of potential natural abutments may influence thetreatment more than any other factor. In the implant tooth fixedprosthesis, four important components may contribute movement tothe system, the implant, bone, tooth, and prosthesis.

The sudden, initial tooth movement ranges from 8 to 28m in avertical direction under a 3 to 5 lb load, depending on the size,number, and geometry of the roots and the time elapsed since the lastload application. Once the initial tooth movement occurs, thesecondary tooth movement reflects the property of the surroundingbone and is very similar to the bone implant movement. The axialmovement of an implant has no initial, sudden movement and rangesfrom 3 to 5 m with little correlation to the implant body length.

When teeth oppose each other, the combined intrusivemovements of the contacting elements may be 56m (28m + 28m).When a tooth opposes an implant, the combined intrusive movement is33m (28m + 5m). When implant prostheses oppose each other, thebiomechanical mismatch between teeth in the rest of the mouth andimplants increase. The total combined movement may be 10m,compared with 56m in the rest of the mouth, and contrary to the teeththat move immediately, even with light loads, the implants only movethis amount under a heavy occlusal load. A lighter load may generate atotal implant movement of less than 3m.

For difference in vertical movement of teeth and implants inthe same arch, the existing occlusion is evaluated before implantreconstruction. Occlusal prematurities are ideally eliminated on teethbefore implant reconstruction. Thin articulating paper (less than 25mthickness) is then used for the initial implant occlusal adjustment incentric relation occlusion under a light tapping force. The implantprosthesis should barely contact, and the adjacent teeth should exhibitgreater initial contacts. Only axial occlusal contacts should be presenton the implant crown. Once the equilibration with a light bite force iscompleted, a heavier centric relation occlusal force is applied. Thecontacts should remain axial over the implant body and may be ofsimilar intensity on the implant crown and the adjacent teeth undergreater bite force to allow all elements to react similar to the occlusalload. Hence to harmonize the occlusal forces between implants andteeth, a heavy bite force occlusal adjustment is used because itdepresses the natural teeth, positioning them closer to the depressedimplant position and equally sharing the load.

If healthy anterior teeth and/or natural canines are present, theocclusion allows those teeth to distribute horizontal loads inexcursions, while the posterior teeth disocclude during excursions.Anterior, compared with posterior bite force measurements andelectromyographic studies provide evidence that the stomatognathicsystem elicits significantly less force when the posterior segments arenot in contact. As a result, all lateral excursions of IPO opposingfixed prostheses or natural teeth should disocclude the posteriorcomponents. The resultant lateral forces are thus distributed only tothe anterior segments of the jaws, resulting in a decrease in overallocclusal force magnitude because of diminished muscle firing andrecruitment.

This occlusal scheme should be followed whether or notanterior implants are in the arch. However, if anterior implants mustdisocclude the posterior teeth in excursion, two or more implantssplinted together should help dissipate the lateral forces.

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When anterior implants and teeth are not connected - Theinitial lateral movement of healthy anterior teeth ranges from 68 to108m before secondary tooth movement. Anterior implantmovements are not immediate and range from 10 to 50m. Because ofthe greater discrepancies in lateral movement, the occlusal adjustmentin this direction is more critical to implant success and survival. Lightforce and thin articulating paper(20m) are first used to ensure that noimplant crown contact occurs during the initial occlusal or lateralmovement of the teeth. A heavier force during centric occlusion andexcursions is then used to develop similar occlusal contacts on bothanterior implants and natural teeth.

Unlike teeth, implants do not extrude, rotate, or migrate underocclusal forces. Natural teeth exhibit mesial drift and slight changesin occlusal position do occur over time. The proposed occlusaladjustment does not encourage additional tooth movement becauseregular occlusal contacts occur. The teeth opposing implants are nottaken out of occlusion. Brief occlusal contacts on a daily basismaintain the tooth in its original position (similar to the rest of themouth). In addition, because most teeth occlude with two teeth, theopposing teeth positions are even more likely to remain the same.

No occlusal scheme will prevent mesial drift and minor toothmovement from occurring. An integral part of the IPO philosophy isthe regular evaluation and control of occlusal contacts at eachregularly scheduled hygiene appointment. This permits the correctionof minor variations occurring during long-term function and alsohelps prevent porcelain fracture and other stress-relatedcomplications on the remainder of the natural teeth.

For implants joined to natural teeth a similar scenario is usedfor the occlusal equilibration. A light force and thin articulating paperare used, and the implant crown exhibits minimum contact comparedwith the natural abutment crown. A gradient of force is designed onthe pontics. A heavy bite force is then used to establish equal occlusalcontacts for all abutments and the entire prosthesis, whether implantor natural.

Implant Orientation and Influence of Load Direction:Forces acting on dental implants are referred to as vectors (defined

in both magnitude and direction). Occlusal forces are typically three-dimensional, with components directed along one or more of the clinicalcoordinate axes.

Implants are designed for a long axis load to the implantbody. Stress contours were primarily concentrated at the transosteal(crestal) region. An axial load over the long axis of an implant bodygenerates a greater proportion of compressive stress than tension orshear forces.

Any load that is applied at an angle may be separated intonormal (compressive and tensile) and shear forces. The greater theangle of loads to the implant long axis, the greater the compressive,tensile and shear stresses. When FEA evaluates the direction of theforce changed to a more angled or horizontal load, the magnitude ofthe stress is increased by 3 times or more. In addition, rather than acompressive type of force primarily, greater tensile and shear forcesare also demonstrated and increase more than 10 times comparedwith the amount found with an axial force. These stress contoursresemble the pattern of early crestal bone loss on implants.

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BONE MECHANICS AND OCCLUSION

The effect of offset or angled loads to bone is furtherexacerbated because of the anisotropy of cortical bone. Anisotropyrefers to the character of bone, whereby its mechanical properties,including ultimate strength, depend on the direction in which the boneis loaded. Cortical bone of human long bones has been reported asstrongest in compression, 30% weaker in tension, and 65% weaker inshear. Therefore IPO attempts to eliminate or reduce all shear loads tothe implant to bone interface.

A force applied at a 30-degree angle decreased the bonestrength limits by 10% under compression and 25% with tension. A60-degree force reduced the strength 30% under compression and55% under tension. Therefore not only does the crestal bone loadincrease around the implant with angled forces, but the amount ofstress the bone may withstand is also decreased. The greater the angleof load, the lower the ultimate strength.

The primary component of the occlusal force should thereforebe directed along the long axis of the implant body, not on an angle orfollowing an angled abutment post. Angled abutments are used onlyto improve the path of insertion of the prosthesis or the final estheticresult. The angled abutment, which is loaded along the abutment axis,will transmit a significant moment load to both the implant crestalregion and abutment screw, proportional to its angle of inclination. Inaddition, the angled implant often requires an angled abutment.Angled abutments are fabricated in two pieces and are weaker indesign than a one-piece post. Furthermore, a larger transverse loadcomponent develops at the crest as a result of angled loads. An angledload to the implant long axis increases the compressive forces at thecrest of the ridge on the opposite side of the implant in which theforce is directed, increasing the tension component of force along thesame side. The greater the angle of force to the long axis of theimplant body, the greater the potentially damaging load at the crest ofthe bone.

Hence the angled load increases the amount of crestal stressesaround the implant body, transforms a greater percentage of the force totensile and shear force, and reduces bone strength in compression andtension. In contrast, the surrounding implant body stress magnitude isleast and the strength of bone is greatest under a load axial to theimplant body.

Premature occlusal contacts result in localized lateral loading ofthe opposing contacting crowns. Because the surface area of apremature contact is small, the magnitude of stress in the bone increasesproportionately (i.e., stress=force/area). All the occlusal force is appliedto one region rather than being shared by several abutments and/orteeth. In addition, the premature contact is most often on an inclinedplane, therefore creating a greater horizontal component to the load andincreasing compressive and tensile crestal stresses. Therefore occlusalevaluation and adjustment in partially edentulous implant patients aremore important than in the natural dentition because the prematurecontacts can result in more damaging consequences on implantscompared with teeth.

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The elimination of premature contacts is more important thanin natural teeth because the implant is less mobile and often cannoteffectively dissipate the forces. In addition, the teeth benefit from agreater occlusal awareness (proprioception) or oral tactile functionthan implants.

Once the natural teeth are removed, the bone remodels to theheight at or below the lowest level of the lateral cortical plates.Hence the implant crown height is often greater than the originalnatural anatomic crown, even in Division A bone. Crown height,with a lateral load, is a magnifier of stress to an implant to boneinterface. The greater the crown height, the greater the resultingcrestal moment with any lateral component of force that develops asa consequence of an angled load. Angled abutments loaded in thedirection of the abutment with an increase in crown height aresubject to even greater crestal moment loads because of both thelateral load and the increased lever effect from the crown height.

In the anterior maxilla, labial concavities may require that theimplant be angled away from the labial bone and the abutment toward thefacial crown contour. These implant bodies are more frequently loaded at anangle, and an angled prosthetic abutment is required. As a result, largerdiameter implants or a greater number of implants are indicated to minimizethe crestal bone stress on each abutment. IPO aims at reducing the force ofocclusal contacts, increasing implant number, and/or increasing implantdiameter for implants subjected to angled loads or with an increased crownheight or on the cantilever portion of a prosthesis.

OCCLUSAL SCHEMES

A primary goal of an occlusal scheme is to maintain theocclusal load that has been transferred to the implant body within thephysiologic limits of each patient. These limits are not identical for allpatients or restorations. The forces generated by a patient areinfluenced by parafunction, masticatory dynamics, tongue size,implant arch position and location, and implant arch form and crownheight. The prosthodontist can best address these force factors byselecting the proper implant size, number, and position, using stress-relieving elements, increasing bone density by progressive loadingand selecting the appropriate occlusal scheme.

CLASSIFICATION OF OSSEOINTEGRATED PROSTHESIS

Hobo et al

1. Fully bone anchored bridge

2. Overdenture

3. Freestanding bridges

a. Kennedy class I

b. Kennedy class II

c. Kennedy class III

d. Kennedy class IV

4. Bridge connected to the natural teeth.

5. Single tooth replacement.

Misch C.E et alTYPE DEFINITION

FP-1 Fixed prosthesis, replaces only the crown, lookslike a natural tooth

FP-2 Fixed prosthesis, replaces the crown and a portionof the root, crown contour appears normal in theocclusal half is elongated or hypercontoured in thegingival half

FP-3 Fixed prosthesis, replacing missing crowns andgingival colour and a portion of the edentulous site,prosthesis must often use denture teeth and acrylicgingiva, but may be porcelain to metal

RP-4 Removable prosthesis, overdenture supportedcompletely by implant

RP-5 Removable prosthesis, overdenture supported byboth soft tissue and implants

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IMPLANT PROTECTIVE OCCLUSION(IPO)

When teeth are present, the maxillary dentate posterior ridge ispositioned slightly more facial than its mandibular counterpart. Oncethe maxillary teeth are lost, the edentulous ridge resorbs in a medialdirection as it evolves from Division A to B, Division B to C, andDivision C to D. As a result, the maxillary permucosal implant sitegradually shifts toward the midline as the ridge resorbs.

As a result of ridge resorption inwidth the maxillary posterior implantpermucosal site may even be lingual to theopposing natural mandibular tooth. Theposterior mandible also resorbs lingually asthe bone resorbs from Division A to B. As aconsequence, endosteal implants are alsomore lingual than their natural toothpredecessors.

Occlusal Table Width:A wide occlusal table favors offset contacts during mastication

or parafunction. Narrower implant bodies are even more vulnerable toocclusal table width and offset loads. Wider root form implants canaccept a broader range of vertical occlusal contacts while stilltransmitting lesser forces at the permucosal site under offset loads.Therefore in IPO the width of the occlusal table is directly related tothe width of the implant body.

During mastication, the amount of force used to penetrate thefood bolus is also related to occlusal table width. For example, lessforce is required to cut a piece of meat with a sharp knife (narrowocclusal table), than with a dull knife (wider occlusal table). Thegreater surface area requires greater force to achieve a similar result.Hence the wider the occlusal table, the greater the force developed bythe biologic system to penetrate the bolus of food.

The posterior narrow occlusal table also facilitates daily homecare. The laboratory technician often attempts to fabricate occlusalfacial and lingual contours similar to that of natural teeth. This oftenresults in ridge laps or porcelain extension at the facial gingival marginof the implant, to create an occlusal table approximately 8 to 10 mmwide. As a result, home care in the sulcular region of the implant isimpaired by the overcontoured crown design. On the contrary, a narrowocclusal table combined with a reduced buccal contour (in the posteriormandible) permits easier sulcular oral hygiene in manner similar to atooth and improves axial loading.

The narrower occlusal contour also reduces the risk ofporcelain fracture. A facial profile similar to a natural tooth on thesmaller diameter implant results in cantilevered restorative materials.The facial porcelain is most often not supported by a metalsubstructure because the gingival region of the crown is alsoporcelain. As a result, shear forces result on the buccal cusp on themandibular crown or lingual cusps in the maxillary crown, and aremore likely to increase the risk of porcelain fracture.

Restorations mimicking the occlusal anatomy of natural teethoften result in offset loads (increased stress), complicated home careand increased risk of porcelain fracture. As a result, in nonestheticregions of the mouth, the occlusal table should be reduced in widthcompared with natural teeth.

DIVISION OF AVAILABLE BONE:A,B,C&D (MISCH)

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CROWN CONTOUR

Division A Bone

The primary component of the occlusal force is evaluated duringthe treatment-planning phase. In an edentulous ridge with abundantheight and width and little resorption, the implant may be placed in amore ideal position for occlusion and esthetics.

Offset loads are used to describe cantilevered buccal or lingualocclusal contacts, not directed along the long axis of the implant body.When offset loads are generated at an angle, the distance between theoffset contact and the long axis acts as a moment arm that magnifiesthe effect of the lateral force.

The most common implant placement corresponds to a centralposition in the residual ridge. The implant osteotomy begins in the centerof the crest and is gradually increased to the optimal width indicated inrelation to the recipient bone. Facial concavities are avoided, and thethinner facial cortical bone is protected, to limit surgical complicationssuch as labial dehiscence. As a consequence, whether in the maxilla orthe mandible, the implant is frequently placed under the central fossaregion of the former natural tooth.

To load the implant body in anaxial direction, the primary occlusalcontact should therefore be the centralfossa region in Division A bone. Thusfor maxillary implant opposingmandibular natural teeth, themandibular buccal cusp acts as theprimary tooth contact.

Because bone loss occurs at the expense of the facial plate, amodified buccal contour anatomy may need to be generated in DivisionA or B mandibles. The occlusal table width is reduced to favor an axialload on the implant in nonesthetic regions. The Division A mandibularimplant is placed under the central fossa region of the natural tooth.When opposing a natural maxillary molar, the primary contacting cuspbecomes the maxillary lingual cusp opposing the mandibular implantcrown, with the mandibular buccal cusp of decreased height and widthover the implant body. Hence all contacts are situated mediallycompared with those on natural teeth.

The lingual contour of the mandibularimplant crown is similar to the original naturaldentition in position, complete with horizontaloverlap to the maxillary lingual cusp toprevent tongue biting during function. Thereis no occlusal contact on the lingual cusp, sooffset loads during parafunction areeliminated.

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The posterior maxillary crown is reduced only from the lingualaspect, compared with a natural maxillary molar, to reduce the occlusal tablewidth. such a reduction increases the lingual overjet when the teeth are inocclusion. Narrower opposing mandibular occlusal tables are desirable todirect occlusal forces over the maxillary implant body. As a result, whenopposing maxillary implants, the buccal cusps of natural mandibular teeth(or crowns on implants) should be recontoured to minimize offset loads incentric relation occlusion. The maxillary buccal cusp may then be retainedfor esthetics, but the functional occlusal table is reduced.

When esthetics are not a concern the distal one half of the firstmolar and / or the entire second molar is often restored in cross bite toimprove the direction of forces. In the posterior esthetic regions of themaxilla with facial bone resorption and / or lingually placed implants, awider occlusal table is required to project the facial contours for idealesthetics. Bone grafting to increase bone width may be required in theseesthetics zones, so a larger diameter implant may be placed that permitsrestorations of the buccal contours with maintenance of cervical contourswith emergence profiles, which permit proper hygiene of the sulcularregions.

Posterior implants opposing each other attempt to axially loadboth entities. The facial cusp of the maxillary crown is required foresthetics. The other contours of the opposing crowns are reduced inwidth to minimize the occlusal table width and axially load theimplants.

WHENEVER POSSIBLE THE PORTIONS OF AN IMPLANTCROWN THAT ARE NOT SUPPORTED BY AN AXIALLYPOSITIONED IMPLANT SHOULD BE RECONTOURED SOTHEY DO NOT RECEIVE OCCLUSAL LOADS.ALTERNATIVELY, SEVERAL ADDITIONAL IMPLANTSSHOULD BE USED TO DISSIPATE THE FORCE.

DIVISION B BONE

Division B bone has maxillary and mandibular implants positionedunder the lingual cusp when compared with the original natural toothposition. As a result, mandibular crowns require even more reduced buccalcontours to avoid offset occlusal contacts. The primary contact of occlusionon an opposing natural posterior maxillary tooth is the lingual cusp, whichis reshaped to axially load the implant.

The buccal cusp of the mandibular implant crown is locatednear the original central fossa of the natural tooth. The mediallypositioned Division B mandibular implant crown may have a centralfossa, but it is more lingual than the original position. The lingualcontour of the crown is similar to that of the original natural tooth andhas an overjet with the opposing natural tooth to prevent biting thetongue during function. The mandibular posterior implant may, onoccasion, be angled medially because of the sub mandibular fossa.

As a result, an angled abutmentand a lingual straight emergence crownprofile to minimize the lingual volume ofthe restoration are indicated.Augmentation of the mandibularDivision B ridge is often required whenstress factors are moderate to improvethe implant position and prostheticguidelines.

A Division B maxillary implant is often placed under the palatal cuspregion of the original natural tooth. The maxillary occlusal table cannotalways be reduced from the facial aspect for esthetic reasons; therefore thebuccal cusp is offset facially but left completely out of occlusion (as withnatural teeth) in centric relation occlusion and during all mandibularexcursions. The buccal cusp of the opposing natural tooth is recontoured inwidth and height to reduce offset loads to the opposing crown on themaxillary implant. The primaryocclusal contact is centric relationocclusion is the maxillary palatalcusp over the implant body andthe central fossa region of themandibular natural tooth. Boneaugmentation for larger implantwidth is more indicated in themaxilla because of the less densebone and the prosthetic needs toreplace an esthetic buccal crowncontour.

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When Division Bimplants are placed in botharches, the maxillary andmandibular prostheses aresimilar to that described in theprevious scenario. However,it is usually not possible toload both arches with an axialload, so the weakest implantin bone density, width, orprosthesis type (fixed vs.removable) determines theaxial load, because it is themost vulnerable arch.

When further resorption occurs and the ridge evolves intoDivision C or D, the maxillary palatal cusp becomes theprimary contact area, situated directly over the implant body.Hence the occlusal contacts differ from those of a natural toothand may even be positioned more medial than the natural palatalcusp when the implant is placed in Division C or D bone.

Influence of Surface Area:An important parameter in IPO is the adequate surface area to

sustain the load transmitted to the prosthesis. It is important toremember that mechanical stress, in its simplest form, can be defined asthe force magnitude divided by the cross sectional area over which thatforce is applied.

When implants of decreased surface area are subject to angledor increased loads, the magnified stress and strain magnitudes in theinterfacial tissues can be minimized by placing an additional implant inthe region of concern.

Thus when narrow diameter implants are used in regions thatreceive greater forces, additional splinted implants are even moreindicated to compensate for their narrow design and to help decreaseand distribute the load over a broader region. When forces areincreased in magnitude, direction or duration (e.g., parafunction), ridgeaugmentation maybe required to improve implant placement, reducecrown height, and increase implant width and number to compensatefor the increased loads.

Maxillary Root surface area (mm2)

CENTRAL 204

LATERAL 179

CANINE 273

FIRST PREMOLAR

234

SECOND PREMOLAR

220

FIRST MOLAR 433

SECOND MOLAR

431

Mandibular Root surface area (mm2)

CENTRAL 154LATERAL 168CANINE 268FIRST

PREMOLAR180

SECOND PREMOLAR

207

FIRST MOLAR 431SECOND MOLAR

426

Radius (mm) Length (mm) Surface Area (mm2)

1.75 10

12

14

110

132

154

2.00 10

12

14

126

151

176

2.25 10

12

14

141

169

197

2.50 10

12

14

157

188

220

2.75 10

12

14

172

207

242

3.00 10

12

14

188

226

264

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The prosthesis type may also be modified from a fixedrestoration (FP-1 to FP-3) to a removable prosthesis (RP-4). This ismost effective when nocturnal parafunction is present because therestorations may then be removed while sleeping. In addition, stressrelieving elements may be included in the removable restoration, andadditional support may be gained from the soft tissue (RP-5restorations).

Wider diameter root form implants have a greater area of bonecontact at the crest than narrow implants (resulting from theirincreased circumferential bone contact areas). As a result, for a givenocclusal load, the mechanical stress at the crest is reduced with widerimplants compared with narrow ones.

Natural teeth follow similar principles of diameter and surfacearea as just described. The anterior region of the mouth ischaracterized by reduced bite force compared with the posteriorregion. Consequently, the anterior tooth cross section is smaller, andthe surface area is reduced compared with the greater diameter andsurface area of posterior teeth.

Design to the Weakest Arch:Any complex engineering structure will typically fail at its

“Weakest link”, and dental implant structures are no exception.The amount of force distributed to a system can be reduced by

stress relieving components that may dramatically reduce impact loadsto the implant support. The soft tissue of a traditional completelyremovable prosthesis opposing implant prosthesis is displaced morethan 2 mm and is an efficient stress reducer. Lateral loads do not resultwith as great a crestal load to the implants because the opposingprosthesis is not rigid.

The most common implant treatment, which includes atraditional soft tissue supported complete denture, is a maxillary dentureopposing a mandibular implant supported restoration. The occlusalscheme for this condition raises the posterior occlusal plane, uses amedial positioned lingualized occlusion, and has a bilateral balancedscheme. Whether the mandibular restoration is FP-1, FP-2, FP-3, RP-4,or RP-5, the maxillary denture follows these guidelines.

The mandibular implant supported restoration may exertgreater force on the premaxilla than a mandibular denture and causeaccelerated bone loss. Therefore modification of the occlusal schemeaims at protecting the premaxilla under a maxillary denture by thetotal elimination of anterior contacts with the mandibular anteriorteeth in centric occlusal relation.

Reduced occlusal forces with an absence of lateral contacts inexcursions are recommended on posterior cantilevers or anterioroffset pontics whenever possible. This minimizes the moment forceson the abutments.

It is better for mandibular cantilever pontics to opposemaxillary implants than the reverse situation.

Full –Arch fixed prostheses(FP-1 to RP-4)

Fixed prostheses on natural teeth opposing FP-1 to RP-4implant restorations should follow mutually protected occlusal schemeswhenever possible. In protrusion, there should be total absence ofposterior contacts, especially for cantilevered posterior units. Themasticatory force generated during lateral excursions is decreased inabsence of posterior contacts. This assists in reducing the noxiouseffect of lateral forces on the anterior implants. Two or more implantsshould share any lateral force, and lateral excursions should occur asfar forward as is practical and include the canine.

Minimal occlusal contact in the cantilevered regions and thetotal absence of posterior lateral contacts during excursions areindicated when opposing the natural dentition or a fixed restorations.

Seven to eight implants to support a complete implantprosthesis in two separate units are suggested in the mandible for afixed restoration opposing a fixed prosthesis or natural teeth withinadequate to severe stress factors.

In the edentulous maxilla, flexure of the bone is not aconcern. A full arch prosthesis may be fabricated in one section.

Eight to ten maxillary implants most often are required for atwelve unit fixed prosthesis opposing a fixed dentition on teeth and /or implants with moderate to severe stress factors. Posterior implantsare more critical in the maxilla, in order to eliminate cantilevers andincrease the anteroposterior implant distance, which furtherdecreases stress to the maxillary anterior implants.

Fully bone anchored bridge

Mandibular edentulous case for fully bone anchored

bridge

•Recommended to have a mutually protected occlusion.

•In centric it is necessary to have 30m clearance at the anterior region

•disocclusion should be employed.

•To avoid localization of stresses anterior group function should be employed.

•The anterior guidance should be made slightly flatter than natural teeth to avoid over stresses on the fixtures.

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Kennedy Class I

OCCLUSION FOR FREESTANDING BRIDGES

o Clearance of the anterior teeth should be smaller than the natural teeth.

o Amount of disocclusion required is same as natural teeth since the anterior guidance is provided by the remaining anterior natural teeth.

Protrusive : 1.1mmNon working side : 1.0 mmWorking Side : 0.5 mm

Kennedy Class II

•In centric the posteriorosseointegrated bridge shouldhave 30m open contacts, whileanterior teeth also should have 30m open contacts and begin tocontact under strong bite pressure.

•Amount of disocclusion requiredis same as natural teeth since theanterior guidance is provided bythe remaining anterior naturalteeth.

Protrusive : 1.1mmNon working side : 1.0mm Working Side : 0.5 mm

Kennedy Class III

➢ Vertical dimension is maintainedby remaining natural teeth

➢ The osseointegrated bridge shouldcontact only under strong pressure.

➢Amount of disocclusion requiredis same as natural teeth since theanterior guidance is provided by theremaining anterior natural teeth.

Protrusive : 1.1mmNon working side : 1.0 mmWorking Side : 0.5 mm

Kennedy Class IV

▪ To minimize horizontal loadsgroup function occlusion isrecommended.

▪ During lateral movementposterior teeth on working side canbear the horizontal load while nonworking side can be discluded.

▪Anterior guidance should be flatter than natural dentition to minimize load induced on the fixture during protrusive movement.▪Amount of disclussion suggested is as follows

Protrusive : 0.8 mmNon- working side : 0.4 mmWorking side : 0.0 mm

IMPLANT AND SOFT TISSUE SUPPORTED OVERDENTURE (RP-5)

Anterior Tooth PositionCentric stops or pressure from the tongue and muscle positions

usually prevent continued extrusion of anterior natural teeth. maxillaryanterior prosthetic teeth are positioned forward of the anteriorsupporting bone to satisfy phonetic and esthetic requirements. Momentforces result from contact with the anterior teeth, which may causeinstability of the maxillary prosthesis. Therefore the maxillary dentureusually does not have anterior incisal centric stops. This helps protectthe premaxilla from excess forces in centric occlusion relation andinitial excursions of the mandible, as the premaxilla is vulnerable toresorption from external stresses.

Posterior Tooth PositionThe maxillary edentulous posterior ridge resorbs in a medial directions

it transforms from Division A to B, Division B to C, and Division C to D.therefore the maxillary denture tooth gradually becomes more cantilevered offthe bone support, even when positioned in the same spatial location. Themandibular edentulous posterior ridge also resorbs in a medial redirection as ittransforms from Division A to B, but then resorbs laterally from Division B toC, and more lateral as it resorbs from Division C to D. In complete dentures,the position of the mandibular posterior teeth is often determined first. Bonesupport concepts of occlusion often position the mandibular teethperpendicular to the edentulous ridge. This positions the central fossa of theposterior mandibular teeth more medial than that of their natural predecessorsin Division B, but more facial in Division C, and very facial in Division Dcompared with the natural tooth placement.

The maxillary teeth are then situated farther facially than the originalteeth, if a normal cusp fossa relation is maintained. Consequently, maxillarydenture teeth are always placed lateral to the resorbing bony support, and thecondition is compounded in cases of advanced atrophy (Division C or Dbone).

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The basic, concept of lingualized occlusion was first introducedby Gysi. Later Payne suggested the maxillary buccal cusps of posteriorteeth should be reduced, so only the lingual cusps would be in contact.Pound discussed a similar concept, but reduced the buccal cusp of themandible and introduced the term “lingualized” occlusion. Pound alsoplaced the lingual cusp of the mandibular posterior teeth between linesdrawn from the canine to each side of the retromolar pad. Consistent inthe Philosophy of Payne and Pound, was the belief that the palatal cuspshould be the only area of maxillarytooth contact. These occlusal schemeswere designed to narrow the occlusaltable and improve mastication, reduceforces to the underlying bone, and helpstabilize a lower denture. Thetechniques of Payne and Pound may bemodified further to a medial positionedlingualized occlusion, proposed byMisch.

Medial Positioned Lingualized occlusion : Laboratory steps

1. Mount the upper cast using a face bow record. Mount the lowercast using the centric relation record. Set the horizontal condylarguidance according to the protrusive record.

2. Set the maxillary and mandibular anterior teeth for esthetics,phonetics, and lip support.

3. Cut back the posterior flange of the lower record base to exposethe retromolar pad. Outline the retromolar pad in pencil. Draw aline from the lingual border of the pad to the mesial aspect cuspid.The central fossa of mandibular posterior teeth will be set alongthis line.

4. Using a flat plane or 10 degree mold, set the mandibular posteriorteeth in a compensating curve. The curve should have both amediolateral and anteroposterior dimension that progressivelydevelops as the teeth are set posteriorly. The curve starts with thefirst premolar and becomes more accentuated in the molar region(closer to the condyle) (i.e., first premolar 0 to 5 degrees, secondpremolar 5 to 10 degrees, first molar 15 to 20 degrees, secondmolar 20 to 25 degrees). The anteroposterior angle of the curveis the second molar region and should ideally approximate thehorizontal condylar guidance (i.e., 20 to 25 degrees).

5. Drop the incisal pin of the articulator 1 to 2 mm.

6. Using a 30 to 33 degree mold, set the maxillary posterior teethwith the buccal cusp tilted out facially. The lingual cusp shouldcontact the central groove of the mandibular teeth (this will be theonly tooth contact point). There should be no contact between themandibular buccal cusp and the opposing maxillary tooth.

7. Return the incisal pin to the original position (up 1 to 2 mm).

8. Using articulating paper to check the contacts, grind a small fossain the mandibular tooth for the maxillary lingual cusp tip.Continue to adjust the occlusion until the incisal pin touches theincisal table. Check for balanced occlusion in excursions.

9. Festoon the set up for the try in appointment.

Overdenture

Maxillary edentulous case for overdenture

• Recommended occlusion foroverdenture is fully balancedocclusion with lingualizedocclusion.

• Incase maxillary overdenture isopposed by a mandibular fullybone anchored bridge, in centrica small clearance isrecommended in the anteriorteeth, while posterior contactsimultaneously.

• Disocclusion is not employedhere.

OCCLUSAL MATERIALS

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The materials selected for the occlusal surface of the prosthesisaffect the transmission of forces and the maintenance of occlusalcontacts. In addition, occlusal material fracture is one of the mostcommon complications for restorations on natural teeth or implants.Therefore it is wise to consider the occlusal material for eachindividual restoration. Occlusal materials maybe evaluated byesthetics, impact force, a static load, chewing efficiency, fracture, wear,interarch space requirements, and accuracy of castings. The three mostcommon groups of occlusal material are fixed prostheses on implantsare reviewed with relevance to the previous eight criteria.

Esthetics:

Esthetics is a major concern for patients. The most estheticmaterial available today is porcelain. Acrylic is acceptable for esthetics,and metal is a poor choice of materials when esthetics is the chiefcriterion. However, there are many situations in which esthetics is notan important aspect of the restorations. For example, when a maxillarysecond molar is restored, most patients do not expose this area whensmiling or laughing.

Forces:The materials on the occlusal aspect of the prostheses affect the

transmission of force to the bones. Impact loads give rise to brief episodes ofincreases force, primarily related to the speed of closure and the dampeningeffect of the occlusal material. The hardness of material is related to its abilityto absorb stress from impact loads. All porcelain occlusal surface exhibits ahardness 2.5 times greater than that of natural teeth. Acrylic resin has a Knoophardness of 17 kg/mm2, and enamel has a 350 kg/mm2 hardness. A compositeresin may exhibit a hardness of 85% that of enamel. Therefore impact loadsare lowest with acrylic, increase with composite and metal occlusals, increaseeven more with enamel, and further increase with porcelain. As aconsequence, it has been suggested to use resin because of its dampeningcharacteristics.

Clenching patients do not have a considerable amount of stressreduction when acrylic versus porcelain materials are used on the occlusalsurfaces.

Progressive bone loading is performed with acrylic transitionalprostheses. This material may reduce the impact force on the early implantbone interface. As the bone matures and its density increases, the need forforce reduction decreases.

Chewing efficiency:

Fixed prostheses exhibit an improve efficiency compared withremovable soft tissue borne prostheses, regardless of the occlusalmaterial.

Acrylic was 30% less efficient than porcelain or metal,whereas there was no difference between gold and porcelain.

Wear:

The definition of wear is the deterioration, change or loss of asurface caused by use. The factors affecting the amount of wear includemagnitude, angle, duration, speed, hardness, and surface finish of theopposing force and surface, together with the lubricant, temperature,and chemical natural of the surrounding environment. Most occlusalwear occurs as a result of bruxism. An intuitive feeling is the harder theocclusal material, the less the wear. However, surface hardness hasbeen shown to be a poor indicator of wear rate. Acrylic resin wears 7 to30 times faster when opposing gold, resin, enamel, or polishedporcelain, compared with gold opposing gold, enamel or porcelain.Gold occlusal surface exhibit less volume loss (sum of loss of opposingocclusal surfaces) than any other combination of materials. Porcelainopposing porcelain wears more than porcelain opposing gold or metal.

The wear rate of occlusal materials, especially in the partiallyedentulous patient with unrestored teeth, should be similar to enamel.In this way, occlusal changes will not dramatically change the occlusalscheme. Lambrechts et al in an in vivo investigation reported verticalwear of premolar and molar tooth enamel to be 20 to 40 um per yearwhen opposing the enamel of natural teeth.

In principle, for the partially edentulous patient it would bebetter to have more occlusal wear on implants, rather than less,because the additional forces on the teeth are better tolerated than onimplant prostheses. As a result, total volume wear may favor porcelainopposing enamel for the implant prosthesis opposing teeth in thepartially edentulous patient and metal opposing enamel in the otherregions of the mouth that require restorations of natural teeth.

The use of gold, regardless of the opposing combination,always provides the least total volume loss.

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Adhesive wear occurs when one hard surface slides over asurface of lesser hardness. As a result, wear fragments of onematerial adhere to the other material. Gold occlusal surfaces areobserved to have gold particles adhered to enamel. This may accountfor less total volume loss when opposing other materials.

For full arch implant supported prostheses, the restoringdoctor may consider metal occlusal to minimize wear and prolongthe accuracy of occlusal scheme long term. Porcelain in estheticregions opposing gold in the more nonesthetic area or metal occlusalin both arches when parafunction or marginal interarch space ispresent are the material most often selected as implant occlusalmaterials.

Materials fracture:

Materials fracture is one of the more common factors that leadto refabrication of a prosthesis. Porcelain, acrylic and compositefractures occur under excessive loads or even with a lesser load oflonger duration, angulation, or frequency. Acrylic or compositematerials fracture more easily. The compressive strength of acrylicresin is 11,000 psi, compared with 40,000 psi for enamel. Compositeresin is 3 times stronger than acrylic.

Porcelain opposing porcelain is not suggested with extremeparafunction, because it may fracture more often than porcelainopposing metal. Metal occlusals do not easily fracture, provide goodwear resistance, and have minimum impact load compared withporcelain.

Accuracy:

Metal shrinkage is 10 times less than porcelain or acrylic andtherefore permits the fabrication of a more passive casting. Whenaccuracy of the casting is paramount, as with screw retainedrestorations, the occlusal material may make a significant difference.This is most important in regions of long spans and / or with a largevolume of materials.

Interarch space:

Acrylic restorations receive their strength from bulk andtherefore require greater interarch space. Metal occlusals require theleast amount of space. In addition, when increased retention of acement retained prosthesis is required, a high abutment and greaterretention may be accomplished with a metal occlusal. Porcelain isintermediate in the interarch space requirement.

Therefore when all seven criteria are evaluated, metal isan excellent occlusal material, with improved properties inaccuracy, wear, fracture resistance, abutment retention, and goodqualities for impact or static force. Esthetics is best satisfied withporcelain, which has improved properties compared with acrylicconcerning fractures and retention.

REVIEW OF LITERATURE

J.B. Brunskin and J.A. Hipp in 1984 studied the in vivoforces on dental implants. Methods are presented formeasuring vertical force components or bridged titaniumdental implants in dog mandibles. These methods haveincluded custom made strain gauge transducers, plushard wiring and telemetric schemes for data collection.The essential components of the measurements systemare described, and typical bite force data are illustrated

Rangert et al in 1989 carried out a study on theforces and moments on Brenamark implants. Theplacement of fixture (implants) in relation to the geometryof a prosthetic restoration has a great influence on themechanical loading of the implant. Based on Theoreticconsideration and clinical experiences with the Brenamarksystem, this article gives simples guidelines for controllingthese loads. The emphasis is on design rules that can beused in clinical practice. With the class I lever as areference. Various clinical implant prosthesis situations arediscussed and evaluated.

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Parker et al in 1991 reviewed the occlusal considerations in restorativedentistry. The major topics include the assessment and treatment ofocclusal wear, the controversies surrounding treatment position of themandibular condyles, occlusal considerations in osseointegratedprosthesis, the two way relationship between occlusal factors andtemporomandibular disorders, design criteria and longevity studies inresin bonded, fixed partial denture.

Hobo et al in 1991 presented a case report on occlusion forosseointegrated prosthesis and concluded that the concept of occlusionsuitable for osseointegrated prosthesis is basically the same as thegnathological occlusion. However the natural tooth sinks about 30µmduring function, while an osseointegrated bridge which is supporteonly by the bone does not sink. Therefore it is necessary to adjust thecentric contacts of the osseointegrated fixed bridge slightly more openthan the natural teeth. During the eccentric movement, in order tominimize horizontal loading, the concept of disocclusion is generallyused.

James et al in 1993 discussed the edentulous implantsan emphasized that the occlusal contacts of the finalfixed restoration are affected significantly by implantposition. Lateral occlusal forces, may lead to abutmentscrew fracture. They may be due to either excessivelateral occlusal pressure or a malposed implant thatrequires non axial loading during normal function.

C.E. Misch et al in 1994 discussed an implant protectedocclusal on a biomechanical rationale. The clinicalsuccess and longevity of endosteal dental implants arecontrolled, in a large part, by the mechanical milieuwithin which they function. The occlusion is a criticalcomponent of such a mechanical environment. “Implant

protected occlusion” refer to an occlusal scheme that isoften uniquely specific to the restoration of endostealimplant prosthesis. Implant orientation and theinfluence of load direction, the surface area of implants,occlusal table width, and protecting the weakest area areblended together from a biomechanical rationale toprovide support for a specific occlusal philosophy.

Tashkandi et al in 1996 did an analysis of strain atselected bone sites of a cantilevered implant supportedprosthesis. the results revealed that the maximum strainoccurred at the strain gauge positioned on cortical boneover the apex of the most distal implant under 10 and 20 lbloading conditions.

Osamu et al in 2002 did a study on influence of suprastructure materials on strain around an implant under twoloading conditions. The results showed under static andnon impact dynamic loading the three super structurematerials tested (highly filled composite resin, acrylic resinand gold alloy), had the same influence on the straintransmitted to the bone simulant that surrounded a singleimplant.

Kent et al in 2004 did a photoelectric analysis of the effectof palatal support on various implant supported overdenturedesigns and concluded that at the removal of the palatalsupport produces a greater effect and more concentratedstress difference for maxillary overdenture than differencebetween the attachment designs.

With palatal coverage Without palatal coverage

Steven et al in 2004 did a study of stress transfer of fourmandibular implant overdenture cantilevered designs. Hisresults condluded that under load all prosthetic designsdemonstrated a low stress transfer to the ipsilateralabutment and to the contralateral side of the arch. Theplunger retained prosthesis retained by two implantsdemonstrated a more uniform stress trasnfer to theipsilateral terminal abutment than the clip retainedprosthesis retained by three implants and provided moreretention.

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Lucie et al in 2004 Did a finite element analysis on the influence ofimplant length and diameter on stress distribution. Results showedan increase in the implant diameter decreased the maximum vonMises equivalent stress around the implant neck more than anincrease in the implant length, as a result of a more favorabledistribution of the simulated masticatory forces applied in this study.

Osseointegrated supported prosthesis (ISP) have shown high standardof success. This success rate depends not only on meticulous surgicalprotocol but also on understanding concept of occlusion.

Occlusion should be a key factor to overall success rate. The conceptof occlusion suitable for implant supported prosthesis is basically thesame as gnathological occlusion.

In Centric contact of the Osseo integrated crown or fixed prosthesisshould be slightly more open than natural teeth.

In centric Osseo integrated crown or fixed prosthesis should notcontact with opposing teeth under the soft bite pressure (to avoid theocclusal load on the I.S.P. which leads overload the bone structure)

Under the strong bite pressure Osseo integrated supported prosthesisshould contact after the natural tooth intrudes approximately 30µm.

SUMMARY

• To avoid overloading of the occlusal surface, the I.S.P. should nothave plane-to-plane contact.

• Point contact especially cusp-to-fossa tripodal contact is preferred.• During eccentric movement, in order to minimize horizontal

movement, the concept of disocclusion is generally recommended.• Anterior segments of the osseointegrated prosthesis should guide the

mandible to produce posterior disocclusion.• Canine guided occlusion is not recommend for the Osseo integrated

prosthesis to avoid excessive occlusal forces into the single implantfixture which is placed in the canine area. Group function isrecommended to distribute the stress over the entire fixture.

• The ideal place to bear the horizontal load is the trapezoid area,which is surrounded by the osseointegrated fixtures.

• Load transmitted to the fixture is not so destructive when extendedmesially in the anterior region, whereas more destructive whenextended distally.

CONCLUSION

The local occlusal considerations in implant dentistry includethe transosteal forces, bone biomechanics, basic biomechanics,differences in natural teeth and implants, muscles of mastication andocclusal force, and bone resorption. The incorporation of all thesefactors lead to an occlusal scheme (IPO) discussed in this seminar.

Occlusal schemes consider the weakest component, full orpartial edentulous arches, and posterior or anterior teeth and / orimplants. An IPO is a consistent approach for implant occlusalschemes.

The material from which the occlusal region are fabricatedmay affect implant loading and also affect implant reaction forces tothe opposing arch. These occlusal material also affect wear andfracture, which affects the occlusal contacts, vertical occlusaldimension, and esthetics.

References 1. Misch CE : Dentistry of bone and effect on treatment plans, surgical

approach, healing and progressive loading. Int. J. Oral implantol 6:23-31,1990.

2. Misch CE : Progressive bone loading, Pract Periodontics Aesthet Dent.2:27-30, 1990.

3. Misch CE : Progressive bone loading. In Misch CE, editor; Contemporaryimplant dentistry, pp 623-650, St. Louis, 1993, Mosby.

4. Bidez MW, Misch CE : Force transfer in implant dentistry; basic conceptsand principles, Oral implant 18: 264-274, 1992.

5. Misch CE , Bidaz MW : Implant protected occlusion, a biomechanicalrationale, Comp Cont. Dent Educ. 15(11):1330-1343, 1994.

6. Misch CE : early crestal bone loss etiology and its effect on treatmentplanning for implants, post Grad Dent. (2)3:3-17, 1995.

7. Jemt T, Linden B, Lekholm U : failures and complications in127consecutively placed fixed partial prostheses supported by Branemarkimplants ; from prosthetic treatments to first annual check up , Int. J. OralMaxillofac Impl. 7;40-44, 1992.

8. Isidor F : Loss of osteointegration caused by occlusal load of oralimplants, Clin Oral Implant Res.7:143-152, 1996.

9. Misch CE : Medial positioned lingualized occlusion, Misch InstituteManual, Birmingham, Mich, 1991.

10. Misch CE : Occlusal considerations for implant supported prostheses.In Misch CE, editior: contemporary implant dentistry, pp 705-733, St.Louis 1993, Mosby.

11. Muhlemann HR : Tooth mobility : review of clinical aspects andresearch findings, J. Periodontal 38:686 1967.

12. Van Steenbergh D : A retrospective multicenter evaluation of thesurvival rate of fixed prosthesis on four or six implants and modumBranemark in full edentulism. J. Prosthet Dent. 61:217-223, 1989.

13. Chee WWL, Cho GC : A rationale for not connecting implants tonatural teeth, J. Prosthod.6(1) :7-10, 1997.

14. Goldstein GR : the relationship of canine protected occlusion to aperiodontal index, J. Prosthet. Dent. 41:277-283, 1979.

15. Williamson EH, Lundquist DO: Anterior guidance its effect onelectromyographic activity of the temporal and masseter muscles, J.Prosthet Dent. 49:816-823, 1983.

16. Schupe RJ et al : effects of occlusal guidance on jaw muscles activity, JProsthet Dent 51:811-818, 1984.

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17. Manns A, Chan C, Miralles R : influences of group function and canineguidance on electromyographic activity of elevator muscles, J. ProsthetDent 57:494-501, 1987.

18. Ko CC DH, Hollister SJ : Micromechanics of implants /tissueinterfaces, J oral implantol 18: 220, 1992.

19. Misch CE: Three dimensional finite element analysis of two plateform neck designs, Master’s thesis, University of Pittsburgh, 1989.

20. Clelland NL, Lee JK, Bimbenet OC et al : A three dimensional finiteelement stress analysis of angled abutments for an implant placed in theanterior maxilla, J. Prosthodont 4(2):95-100, 1995.

21. Papavasillou G, Kamposiora P et al : Three dimensional finite elementanalysis of stress distribution around single tooth implants as a functionof bony support prosthesis type and loading during function, J. ProsthetDent 76: 633-640, 1996.

22. Reilly DT, Burstein AH : The elastic and ultimate properties of compactbone tissue, J Biomech 80:393-405, 1975.

23. Cowin SC : Bone mechanics, Boca Raton , Fla 1989, CRC Press.24. Parein AM, Eckert SE, Wollan PC et al : Implant reconstruction in the

posterior mandible : a long term retrospective study. J. Prosthet Dent78:34-42, 1997.

25. De Marco TL, Paine S : Mandibular flexure in opening and closuremovements, J Prosthet Dent. 31:482-485, 1974.

26. Chibirka RM, Razzoog ME, Lang BR et al : determining the forceabsorption, quotient for restorative materials used in implant occlusalsurfaces, J. Prosthet Dent 67 (3): 361-364, 1992.

27. Naert I, Quirynen M, Van Steenberghe D et al : A six year prosthodonticstudy of 509 consecutively inserted implants for the treatment of partialedentulism. J. Prosthet Dent 67:236-245, 1992.

28. Shultz AW : comfort and chewing efficiency in dentures, J. ProsthetDent. 65:38-48, 1951.

29. Okesm JP : Management of Temporomandibular disorders andocclusion, pp 259-260, St. Louis, 1989, Mosby.

30. Hudson JD, Goldstein GR, Georgescur M. Enamel wear caused by threedifferent restorative material, J. Prosthet 74:647-654, 1995.

31. Monasky GE, Tough DF: Studies of wear of porcelain, enamel and gold,J Proshet Dent 25(3):299-306, 1971.

32. Krejci I,Lutz F,Reimer M et al: Wear of ceramic inlays, their enamelantagonist and luting cements, J. Prosthet Dent 69: 425-431, 1993.

33. Seghi RR, Daher, Caputo A : Relative flexural strength of dentalrestorative ceramics, Dent. Mater 6:181-184, 1990.

THANK YOU

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SEMINARDR. SUDHIR MEENA

GOOD MORNING

Dr.RAMAKRISHNA.M

PHONETICS IN COMPLETE DENTURES CONTENTS⚫ Introduction⚫ Terminology⚫Mechanism of sound production⚫ Development of speech skills⚫ Neurophysiology of speech⚫ Types/Classification of speech sounds⚫ S sounds and their prosthodontic considerations ⚫ Different parts of oral cavity and their influence

on speech⚫ Different aspects of complete denture fabrication

and their influence on speech

⚫Speech tests

⚫Speech analysis methods⚫Speech defects and their management

⚫Special considerations of phonetics

⚫Review of literature⚫conclusion

⚫References

INTRODUCTION

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⚫ Speech is one of the oldest media of communication of thoughts. It has affected human behavior and progress so greatly that it has been one of the important determinants of psycho-social health of the human beings.

⚫ The development of vocal sound into meaningful speech was one of the major accomplishments which enabled the man to reach the pinnacle of the animal kingdom.

⚫ In this highly complex international society of today, man is judged by not just what he says ,but equally by the way he says it.

⚫ “proper speech is reflection of education, careless speech is an imputation of slovenliness, and a faulty speech is a handicap directly proportionate to the degree of speech incapability.”

WHAT IS SPEECH?

⚫ According to Trevor lee,

⚫ “Speech has been defined in its noun form, as an established communicative system of arbitrary and conventionalized acoustic symbols produced mainly by the action of the muscles of the respiratory and upper alimentary tracts………...

In its verb form, the term implies communicative behavior through the use of these conventionalized and arbitrary symbols.”

WHY SPEECH IS IMPORTANT IN DENTISTRY?⚫ The dental profession, as a guardian of oral health, is

engaged to a great extent in altering and restoring structures with in the oral cavity, to alleviate the ravages of disease and developmental abnormalities. A major portion of speech articulation takes place with in the oral cavity, and any alteration or restorations of structures therein will adversely affect speech proportionate to the location and magnitude of alteration.

⚫ For example, A missing bicuspid will permit lateral emission of air, which is intolerable to the precise speaker or singer. A poorly constructed denture with out regard to speech articulation will cause distortions in speech until the patient gets adapted to it.

⚫ But, faulty speech should never be desirable, even for short period of time also, as it may be unpleasant to the listener, psychologically embarrassing to the patient and also adds to the burden of adaptation of dentures.

⚫ So, the treatment objective of every dentist should be to construct artificial restorations like complete dentures that conform to the individual patient’s existing neuromuscular patterns, rather than rely too much on the patient’s ability to adapt.

⚫ For this, it does require knowledge of some fundamentals of phonetics and a precise knowledge of contact of tongue areas with teeth, lips, palate and alveoli for speech articulation, to all the dental practitioners.

TERMINOLOGY RELATED TO SPEECH

Phonetics :

The study of speech sounds, their production and combination and their representation by written symbols.

OR

The description and analysis of the sounds of a particular language.

Phonemics :

The description and classification of the phonemes of the specific language.

Phoneme :

A set of phonetically similar, but slightly differing stand in a language that are heard as a same sound by native speakers and are represented in phonemic transcription by the same symbol.In simple words it is an unit of speech by which we distinguish one utterance from another.Collectively about 40 phonemes make up phonemics of a language.

Eg : Phoneme |P| includes phonetically differentiated sounds represented by P in pin, spin, tip.

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Morphemes:smallest meaningful units of language.They are formed by

collection of various phonemes. In simple term, they can be called words.

PROSODY:It’s a term that describes all those variations in time, pitch,

and loudness that accomplish emphasis and lend interest to speech.

MECHANISM OF SOUND PRODUCTION

⚫ The essential characteristic of speech is the production and organization of sound into symbols.The production of these sound symbols is a phenomenon of highly integrated factors.we can divide these factors as follows,for the purpose of our discussion:

⚫ 1.respiration⚫ 2.phonation⚫ 3.resonance⚫ 4.articulation⚫ 5.neurological integration

RESPIRATION:The speech process is initiated by the energy inherent

in air.In normal speech,the respiratory apparatus providesduring exhalation,a continuous stream of air with sufficientvolume and pressure under voluntary control for phonation.Thestream of air is modified in its course from lungs by maxillo-facial structures and gives rise to the symbols which arerecognized as speech.

PHONATION:when air leaves the lungs,it passes through the larynx

whose true vocal folds or vocal cords modify the stream. Thetrue vocal folds opposing each other with different degrees oftension and space create a slit like aperture of varying size andcontour.The folds by creating resistance to stream of air,set up asequence of laryngeal sound waves with characteristic pitch andintensity.These laryngeal sounds provide the basis fororganization of speech.

• Thyroarytenoid muscle

• Inner edges – Vocalis

• Elastic tissue, stratified epithelium

• Vibrations

➢ Horizontal up to 4 mm

➢ Slightly vertical 0.2 – 0.5 mm

• Average length Males – 15 mm → Deeper pitch

Females – 11 mm

• Vestibular fold

VOCAL CORD RESONANCE:The sound waves produced by the vocal folds are still far from

being the finished product that we hear in speech.It is the resonators that give the characteristic quality to voice.The resonating structures are the air sinuses, organ surfaces and cavities such as the pharynx,oral cavity,nasal cavity and chest wall.The resonating structures do not contribute any energy to the stream of air.They act to conserve and concentrate the energy already present in the laryngeal tone rather than to let it dissipate into tissues.However, the resonating laryngeal tone is still not speech.

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RESONATORS

⚫ ARTICULATION:It is the function of articulatory mechanism to break up,to

modify the laryngeal tones and to create new sounds itself with in the oral cavity.The articulatory mechanism involves the lips,teeth,palate and tongue.

The final action of articulatory apparatus is to articulate in a fluid sequence all the sounds which have been synthesized into symbols.With out this articulating capacity the sounds produced would be only of variable pitch, volume and quantity

ARTICULATORS OF ORAL CAVITY

Soft palateActive

Lip, Mandible & Tongue

Passive

Teeth, Alveolar ridge, Hard palate

Naso-oral balance

Sound ‘K’

NEUROLOGIC INTEGRATION:The factors for speech production are highly coordinated,

some sequentially and some simultaneously by the central nervous system. Speech is a learned function and requires adequate hearing, vision,and normal nervous system for its full development.

Associated with speech is the whole phenomena of intelligence. When speech functions come into contact with the other vital functions of maxillo-facial structures, it is speech that suffers. This is particularly true when the conflict is with the important reflex actions, for example coughing, sneezing,hiccups, and regurgitation.

DEVELOPMENT OF SPEECH SKILLS

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Speech is characteristically and distinctively human, a unique form of behavior apparently limited to homosapiens. Although many animals make distinctive sounds and convey literal and limited messages, they cannot master the symbolizations and abstracts involved in speech.

Modern knowledge of the development of complex behaviors indicate that speech was an evolution rather than a spontaneous or even short time creation.with upright posture and development of manual dexterity came freedom of the mouth from crude grasping and manipulative duties.As a result structures of the throat and mouth were free to evolve into specialized organs, able later to sub serve the speech process.

⚫ Variations such as increased intricacy and flexibility of larynx , shortening and widening of the tongue and increased flexibility of lips, were associated with more obvious changes such as widening of and shortening of mandible, gradual appearance of chin and developing brow to elevate the facial plane from its apish slant. Other changes in ear, palate, muscles of mastication accompanied these more obvious changes.

⚫ These changes are suggestive of development of complex nature of speech. Speech apparently developed slowly from crude beginnings with selection and adaptation of appropriate symbols accomplished in total experience of living. Several other sensory- motor mechanisms which aided man’s communicative efforts, and are now in use by some animals might been usurped to serve the function of human language. A language of touch, for instance, survives now in lobsters and some insects. Gestural communication is used by lower forms and remains of use to man in spite of high development of language.

⚫ so in brief, the concept of communication we have at present took unknown number of centuries to develop from the period of primitive man to the present day ultra sophisticated man.

NEUROPHYSIOLOGY OF THE SPEECH

Sensory (language input) Motor (language output)

Sensory

Speaking a heard word Speaking a written word

FACTORS RELATED TO DEVELOPMENT OF SPEECH SKILL:

1.AGE: A cross sectional study of children shows a general agreement that the development sequence of speech sounds is somewhat as follows.

AGE(in months) CONSONANTS CORRECTLY USED INWORDS

Between 3-4 M,b,p,w,hBetween 4-5 N,t,d,k,g,jBetween 5-6 F,v,s,zBetween 6-7 L,thBtween 7-8 R,wh,s,z

2.INTELLIGENCE: The rate of mastery of the speech and language skill is importantly determined by the child’s intelligence.The mentally

retarded are typically delayed in their first use of words and sentences.They present more than average number of articulation errors, more prominently omissions of phonemes.Complete speechlessness can be attributed to mental deficiency(IQ=10 TO 25)

3.HEARING CAPACITY: For children to learn speech skills hearing is very much essential.Children who are deaf or profoundly hard of hearing display retarding in acquisition of symbol system and development of intelligible speech.That’s why a child who is born deaf is

also born dumb,unless speech methods of training are adapted.

4.IMPAIRMENT OF MOTOR CONTROL: Children with cerebral palsy and and patients with neuromuscular impairment may display impairment of speech apparatus with resulting DYSARTHRIA,as a part of their motor difficulty.

5.SPECIFIC LANGAUAGE DISABILTY: Some children display difficulty in understanding and using language even though testing reveals no hearing loss, motor defects,intellectual impairment or emotional disturbance…Such difficulty in handling the symbol

system is termed as specific language disability/developmental aphasia/congenital aphasia…This is due to the bilateral cerebral

lesions or defective of crucial neural substrate for language.

6. PSYCHOSOCIAL FACTORS: The family constitutes a primary influence on the child’s development. The number of people in

the family,relative position of the child in the group and socio economic status of the family all undoubtedly have some impact on acquisition of speech.Bilingual children have been found to be less proficient in linguistic skills than monolingual children.culturally disadvantaged children and children reared in silent and unstimulated environment can be expected to display communication disabilities.

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TYPES OF SPEECH SOUNDS

Phonemes of English language can be divided into four groups as follows,

1.VOWELS:Vowels are voiced sounds, that is, the vocal cords are activated by vibration of their production. They are formed by, a continuous air flow, the alteration in shape and size of the mouth and the lip opening giving the various sounds their characteristic form. -In English, vowels are a,e,i,o,u

2.DIPTHONGS: Are blends of two vowels spoken in a single syllable with out interruption of phonation.ex:boy, main,tone,dine.

3.CONSONANTS: Consonants may be either voiced or producedwith out vocal cord vibration, in which case they are called breathedsounds.The consonant sounds are produced by the air stream beingimpeded, diverted, or interrupted before it is released.

eg: p, b, m, s, t, r, z etc…

4.COMBINATION: Is blend of a consonanat and vowel articulated in quick succession that they are identified as single phonemes.

CLASSIFICATION OF SPEECH SOUNDS (BOUCHER)

ALPHABETSVOWELS CONSONANTS

PLOSIVES

FRICATIVES

AFFRICATIVES

NASALS

LIQUID CONSONANTS

GLIDES

I. CLASSIFICATION OF CONSONANTS: {Boucher}

⚫ Consonants are divided into groups depending on theircharacteristic production and use of different articulators and valves. They are as follows.

Plosive consonants: These sounds are produced when overpressure of the air has been built up by consonants between the soft palate and pharyngeal wall and released in an explosive way. Ex: P (pay), B (bay), T (to), D (dot)

Fricatives: are also called sibilants and are characterized by their sharp and whistling sound quality created when air is squeezed through the nearly obstructed articulators.

Ex: S (so), Z (zoo)

Affricative consonants: are a mix between plosive and fricative ones. Ex: Ch (chin), J (jar)

Nasal consonants :are produced with out oral exit of air.production involves the coupling of nasal cavity as resonators.When nasal cavities are blocked,the nasal sounds are produced hyponasally,the resulting in speech-we describe as talking with “stuffy nose”….Ex: M (man), N (name), NG (bang)

Liquid consonants(semi vowels) : are , as the name implies , produced with out friction. Ex: R (rose),L(lily)

Glides: that is sounds characterized by a gradually changing articulator shape Ex: W (witch), Y (you)

II. ACCORDING TO LARYNGEAL ACTION

Voice less / surd

• A periodic sound producedby impedance within oralcavity

Voiced / sonant

• Counterpart of surds

• Produced in similar mannerwith vibration of adductedvocal folds.

Plosives Fricatives Affricatives

Voice less p t k s f θ |ts|

Voiced b d g z v δ |dz|

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III. BASED ON PRESSURE CHARACTERISTICS :

• Variation in amount of intraoral breath pressure

• Fricatives, affricatives and plosives – pressure consonants

• Continuants > non continuants

• Voiceless > voiced

IV. CLASSIFICATION OF CONSONANTS BASED ON THE PARTS OF MOUTH INVOLVED IN

THEIR FORMATION

▪ For convenience, in clinical Prosthodontic applications the consonants are once again, classified based on the parts of mouth that are involved in their formation, as follows:

Bilabial sounds (Ex: P, B, M, N,W)Labiodental sounds (Ex: F, V)Linguodentals sounds (EX: Th)Linguoalveolar sounds (EX: T, D, S, Z, N)Linguopalatal sounds (Ex: Sh, Ch, J, R, Y)Linguovelar sounds (EX: K, G, H, Ng)

⚫ Bilabials- Are formed mainly by the lips. For the correct articulation of these consonants the lips are brought into active contact and then opened suddenly, this sudden opening of the lips produces an explosive sound [eg: B,P (plosives) ,M (nasals) and W (glides)]

⚫ In B and P, air pressure is built up behind the lips and released with or without a voice sound.

⚫ CLINICAL SIGNIFICANCE:To determine the anteroposterior positioning of the anterior teeth and thickness of the denture flange:Insufficient support of the lips by teeth or denture base can cause these sounds to be defective. Therefore the anteroposterior positioning of anterior teeth and thickness of the labial flange can affect the production of these sounds.To determine the vertical dimension of occlusion:Usually P and B are produced with an explosive effect, where as M sound is produced with a passive contact of lips. For this reason M can be used as an aid in obtaining the correct vertical height, since a strained appearance during lip contact indicates that the bite blocks are occluding prematurely

I. BILABIAL SOUNDS BILABIAL

Lip closure

|p|, |b| & |m|

I/O breath pressure is impounded behind closed lips

Lip rounding

|w|

Moves to appropriate position

II. LABIODENTAL SOUNDS⚫ Labiodentals- are formed by the lips and teeth. Usually

pronounced with lower lip touching the incisal edges of maxillary incisor teeth Eg: F, V, Ph (fricatives)

⚫ CLINICAL SIGNIFICANCE:

To determine the superoinferior position of anterior maxillary teeth:If the upper anterior teeth are too short (set too high), the V sound will be more like F. If they are too long (set too low), the F will sound like V.

To determine the correct occlusal plane:

If the occlusal plane is set too high the correct positioning of lower lip may be difficult, and if the occlusal plane is too low, the lip will overlap the labial surfaces of the upper teeth to a great extent than is required for normal phonation and the sound might be distorted.

To determine the anteroposterior position of the incisors:

If upper anterior teeth touch the labial side of the lower lip, while these sounds are made then the upper teeth are too far forward or the lower teeth are too far back in the mouth.

If the lower lip tends to raise the lower denture while pronouncing these sounds ,then the lower teeth are too far forward , and this means that the upper teeth also are too far forward.

If the upper anterior teeth are set too far back in the mouth or if the lower anteriors are set too far forward in relation to the residual ridge ,they will contact the lingual side of the lower lip when these sounds are made. .

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Upper incisors and labiolingual center to the posterior third

of the lower lip.

LABIODENTAL PICTURE SHOWING THE POSITIONS OF TEETH AND TONGUE DURING PRODUCTION OF LABIODENTAL SOUNDS (F, V, Ph)

EFFECTS OF MAXILLARY ANTERIOR TOOTH POSITIONING OF ‘F’ AND ‘V’ SOUNDS

III. LINGUODENTAL SOUNDS⚫ Linguodentals- are formed by the tongue and the teeth. During

the pronunciation of these sounds the tongue extends slightly between the incisal edges of the upper and lower anterior teeth. This sound is actually made closer to the alveolus (ridge) than to the tip of teeth. They are also called interdental sounds Ex: Th (fricative)

⚫ CLINICAL SIGNIFICANCE:

To determine the labiolingual position of the anterior teeth: Ask the patient to pronounce words like THIS, THAT, THESE, THOSE and carefully observe the amount of tongue that can be seen between teeth.

If about 3 mm of the tip of the tongue is not visible, the anterior teeth are probably too far forward (except in patients with class II malocclusion.) or may be excessive vertical overlap that does not allow sufficient space between the anterior teeth. If more than 6mm of the tongue extends out between the teeth, then the teeth are probably too far lingual.

• Tip of tongue extending slightly between upper and lower anterior teeth.

• Sounds are made closer to alveolus.

LINGUODENTAL

CONSONANT IV. LINGUOALVEOLAR SOUNDS

⚫ Linguoalveolar sounds are made with the valve formed by contact of the tip of the tongue with the most anterior part of the palate (alveolus) or the lingual side of the anterior teeth Ex: T, D (plosives), S, Z, (fricatives), N (nasals)

⚫ CLINICAL SIGNIFICANCE:To determine the horizontal and vertical relations of the anterior teeth:

Ask the patient to say /S/ and observe the relation of anterior teeth to each other. The incisal edges of upper and lower incisors should approach end to end, but not touch. A failure of incisal edges to approach exactly end to end indicates a possible error in the amount of horizontal overlap of anterior teeth.

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To determine the labiolingual position of anterior teeth:

Ask the patient to say a word TEND. If the teeth are too far lingual, the T in TEND will sound like a D.If they are too far anterior, the D will sound more like a T.This test will reveal the error but will not indicate whether it is upper teeth or the lower teeth that are incorrect labiolingually

To determine the thickness of denture base:

Any thickness in the rugae or anterior palatal region will cause distortions in these sound production.

To determine the vertical dimension of the occlusion:

Ask the patient to say , S, C or Z and observe the distance between the incisors. If the vertical dimension is excessive, the dentures will actually make contact as these consonants are formed and the patient will most likely complain of “clicking Teeth”.

10 sounds – divided into 5 types depending on distinct place and manner of production

a) t & d ; n

LINGUOALVEOLAR

b) Fricatives s & z

Formation of a midline groove of the tongue

c) Fricatives ‘sh’ & ‘zh’

• Broader groove compared to s & z

• Can be discussed as linguopalatal

d) |ts| & |dz| linguoalveolar or palatal affricatives

→ Tongue placement plosives → air exploded through constriction.

e) Lateral |l|

• Tip of tongue in contact with alveolus

• Lowered lateral margins – facilitates air flow .

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V. LINGUOPALATAL SOUNDS

⚫ Linguopalatals-Are formed by the tongue and hard palate. The tongue may contact portion of the hard palate just posterior to the area which is contacted while pronouncing linguoalveolar sounds i.e, alveolus . Ex: Sh (fricatives), Ch, J (affricatives), R (rose), Y (glides)

⚫ CLINICAL SIGNIFICANCE:

To determine the thickness of denture:When Sh sound is produced the air is allowed to escape between the tongue and the palate, and if the palate is too thick in the region of the rugae, it may impair the production of these consonants.

To determine the anteroposterior position of the maxillary incisors:If the maxillary incisors are placed too palatally then these sounds will be distorted.

• |r| & |j| - produced by lingual approximation to some portionof the palate.

• |r| → tip of the tongue is often pointed to an immediately postdental area.

• Tongue blades are arched and tip points down.

• Phoneme adjacent to |r| will determine the contour of thetongue.

LINGUOPALATAL

|j| - Linguopalatal glide

Tongue raised toward the front of hard palate but in thecourse it moves to a position appropriate for articulation offollowing phoneme.

VI. LINGUOVELAR SOUNDS⚫ Linguovelar sounds- are by tongue and soft palate. In these

sounds the air blast is checked by the base of tongue being raised upwards and backwards to make contact with the soft palate. Ex: K, G (plosives), H (fricative), NG (nasal)

⚫ CLINICAL SIGNIFICANCE:

To determine the thickness and posterior extension of denture :A denture which has a thick base in the post-dam area ,or that edge finished square instead of tapering, will probably irritate the dorsum of the tongue, impeding speech, especially causing distortion of velar sounds.

Indirectly the phonation influences post-dam seal area, i.e, when the velar sounds like K, H are pronounced the denture may loose its posterior palatal seal and gets unseated, requiring the sudden repositioning of the tongue to control and stabilize the denture , if its posterior borders extend too back on to soft palate.

LINGUOVELAR→ |k|, |g| & |ng|

•Contact of the middle of the tongue with soft palate.

SSOUNDS AND

THEIR PROSTHODONTIC COSIDERATIONS

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“Say now shibboleth; and he said sibboleth, for he could not frame to pronounce it right…..”

judges XII:6(THE BIBLE)

“ASWATHAMA HATHAHA…..paranthu gajeshu!!!!!”

(KURUKSHETRA)MAHABHARATA

From a dental point of view, the S sound is the most interesting one because its articulation is mainly influenced by the teeth and palatal part of maxillary prosthesis. Clinical experience suggests that S sound can cause most problems in a prosthodontic context. Among the sounds formed in the anterior maxillary region, the S sound is most frequently distorted , possibly because the S sound formation needs particularly fine adjustments of the tongue and depends on special neuromuscular and psychoaudative abilities. The inability to produce sibilant sounds correctly is referred to as SIGMATISM .

In nearly all languages of the world, S is a common speech sound. Some languages (Ex: Finnish and Spanish) have diverging S pronunciation, but generally the interlanguage quality variation is small. On the other hand the inter individual variation in teeth , palate, lower jaw, and tongue shape and size. Given this variation, different speakers have to shape the detailed S gestures differently to achieve a similar S quality.

CHARACTERISTICS OF /S/ SOUNDS⚫ The following phonetic properties or characteristics are

common to all S sounds:

ARTICULATORY CHARACTERISTICS:

The tip of the tongue is placed far forward, coming close to but never touching the upper front incisors.

A sagittal groove is made in upper front part of the tongue, with a small cross-sectional area.

The tongue dorsum is flat.

Normally, the mandible will move forward and upward, with the teeth almost in contact.

ACOUSTIC CHARACTERISTICS:

♦ The comparatively strong sound energy is concentrated to a high-frequency range, with a steep energy cutoff at about 3 to 4 kHz.

AUDITORY CHARACTERISTICS:

♦ The sound is fairly loud, with a light, sibilant (sharp) quality.

HOW ARE “S” SOUNDS PRODUCED?

S SOUNDS are also called SIBILANTS, which are a type of fricative ,linguoalveolar sounds. Ex: S, Z, Sh

The S sounds are produced equally well with two different tongue positions, but there can be some variation even behind the alveolus.

Most people make S sound with the tip of the tongue against the alveolus in area of rugae, but with a small space for air to escape between the tongue and alveolus. The tongue’s anterior dorsum forms a narrow groove near the midline, with a cross section of about 10mm2. The size and shape of this small space will determine the quality of the sound. Part of sibilant sound is generated when the teeth are being hit by a concentrated air jet.

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If the opening is too small, a whistle will result.

If the space is too broad and thin, the sound will be developed as an Sh sound, and its called LISP.

The frequent cause of undesired whistles with dentures is a posterior dental arch form that is narrow

The frequent cause of lisped sound in dentures is ,the contacting of

tip of tongue with upper front teeth.

About one third of patients, make S sound with the tip of tongue contacting the lingual side of anterior part of the lower denture and arching against the palate to form the desired shape and size of the airway.

The clinical significance of this way of pronouncing Ssounds is that, if the lower anterior teeth are too far back, the tongue will be forced to arch itself up to a higher position, and the airway will be too small.

If the lingual flange of the mandibular denture is too thick in anterior region, the result will be a faulty S sound.

It can be corrected when the artificial teeth are placed in same position as that occupied by natural teeth and the lingual flange of the mandibular denture is so shaped that it does not encroach on the tongue space.

PICTURE SHOWING THE TONGUE AND TEETH POSITIONS IN S-SOUND PRODUCTION

CLINICAL SIGNIFICANCE OF /S/ SOUNDS IN PROSTHODONTICS1. To determine the thickness of denture:

When producing the S, C, Z ,Sh sounds, if the artificial rugae are over-pronounced, or the denture base too thick in this area, the air channel will be obstructed and a noticeable lisp or “slushy” S Or Sh sounds results. A whistling sound occurs due to insufficient denture base palatal to the maxillary incisors.

2. To determine the Vertical dimension of occlusion:

If the vertical dimension is excessive, the dentures will actually make contact when pronouncing these consonants, resulting in “clicking of teeth”. During the pronunciation of the S sound, the inter-incisal separation, vertical distance, should average 1 to 1.5 mm. This is referred to as “ closest speaking space” (Silverman)

THE SPEAKING METHOD OF DETERMINING VERTICAL

DIMENSION :

Meyer M. Silversman (1953) Method :

• Head position

• Centric occlusion line

• Closest speaking line

Reevaluation of VD – Clicking of teeth ‘noisy teeth’.

• |m| - passive lip contact

• Strained lip contact or inability to contact lips : increase VD

No vertical overlap

3. To determine the antero-posterior postion of teeth:

If the anterior teeth are placed too far back a lisp may be noticed with the pronunciation of S sound. A whistling sound results if the maxillary teeth are placed too far labially..

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4. To determine the width of dental arch:

If the teeth are set to arch width which is narrow, the tongue will be cramped, thus affecting the size and shape of the air channel ; and this will result in faulty phonation of Ssound.

5. To determine the relationship of upper teeth to the lower anterior teeth by “S-POSITION”:

The S position refers to the relation of the lower anterior teeth to upper anterior teeth required to produce a clear S or Z sound during speech. This is a consistent position in which there is approximately 1 mm of space between the incisal edges of upper and lower anterior teeth, when the S sound is repetitively enunciated. It is also the most forward and closed position of the lower anterior teeth in relation to the upper anterior teeth during speech. Since teeth should not contact during speech, this method is not only ideal for functional positioning of the anterior teeth for complete dentures, but it is also helpful for locating the incisal edges of maxillary or mandibular anterior teeth for fixed or removable partial dentures.

S-position

TO DETERMINE VERTICAL AND HORIZONTAL RELATIONSHIPS OF ANTERIOR TEETH USING S-SOUNDS

DIFFERENT PARTS OF ORAL CAVITY AND THEIR INFLUENCE ON SPEECH

LIPS:Some patients have decreased activity of upper lip because of

inadequate support or disturbed musculature.This can affect thebilabials and fricatives.

TONGUE:The tongue is a principle articulator for speech and contacts

the front, middle and back portion of the hard palate in pronouncingmany of the vowels and consonants.The size and position of the tongue are significant for development ofarch form in natural and artificial teeth.Ill fitting dentures as a result ofover or under extensions of can contribute to misarticulations byinterfering with the necessary tongue co-ordinations.Acquired defects of tongue like macroglossia, microglossia, aglossiaetc..present insurmountable problems for prosthetic rehabilitation.

TEETH:Anterior teeth play a very important role as principle

articulating parts for most of sounds.loss of these teeth causes speech distortions.posterior teeth usually cause minimal or no speech distortion.

PALATE: The shape of palatal vault has been of particular interest

for prosthodontists.The role of palatal rugae in relation to speech has not been established.Their characteristic soft tissue ridges are present in all primates and there is no experimental evidence to support their consideration as speech organ.

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DIFFERENT ASPECTS OF COMLPETE DENTURE FABRICATION AND THEIR INFLUENCE ON SPEECH.

The Prosthodontist’s aim is to reproduce dentures which are

mechanically functional,aesthetically pleasing,and permit normal speech.The most satisfactory attainment of the first two requirements may cause slight defects in the patient’s speech

though undesirable.For this reason during fabrication of dentures,every prosthodontist should give due considerations to some important aspects of denture designing, as follows:

1. Denture thickness and peripheral outline2. Vertical dimension3. Occlusal plane4. Anteroposterior position of the incisors5. Post-damn area6. Width of dental arch7. Relationship of upper anterior and lower anterior teeth.

DENTURE THICKNESS AND PERIPHERAL OUTLINELoss of tone and incorrect phonation occurs due to decrease of airvolume and loss of tongue room in the oral cavity resulting fromunduly thick dentures.

The periphery of denture must not be over extended so as toencroach upon the movable tissues,since the depth of sulci will varywith movements of tongue,lips, and cheeks during the production ofspeech sounds.Any interference with the freedom of thesemovements may result in indistinct phonation,especially if thefunction of lips is in any way hindered.

Sounds that are affected by changes in this region are:-----T, D, S,Sh, Z, R, L, Ch and J

VERTICAL DIMENSIONWhen vertical dimension is excessive,the dentures will make contact resulting in “clicking teeth” as some consonants like M,S,Z are produced.

OCCLUSAL PLANEThe labiodental sounds F,V and Ph, are produced by the air stream being stopped and explosively released when the lower lip breaks contact with the incisal edges of upper anterior teeth.

If the occlusal plane is set too high the correct positioning of the lower lip may be difficult, if on other hand the plane is too low, the lip will overlap the labial surfaces of upper teeth to a great extent than is required for normal phonation and the labiodental sounds might be affected.

THE ANTEROPOSTERIOR POSTION OF THE INCISORSIf the upper anterior teeth are set too far palatally,the contact of lower lip with incisal and labial surfaces will be difficult,resulting in improper pronunciation of labiodental sounds like F,V,and Ph.

If both upper and lower anterior teeth are set to far back,some effect may be noticed on quality of palatolingual sounds like S,C and Z resulting in LISP,due to tongue making contact with teeth prematurely.

The tongue will readily accommodate itself to anteroposterior error in setting of teeth than to vertical errors.

THE POST-DAMN AREAIf the denture has a thick base in this area, or that edge finished square instead of tapering,then there will irritation of the dorsum of tongue, impeding speech especially when vowels like I and E, palato linguals like K,Ng,G and C are produced.

Post-damn seal influences phonation indirectly, for if it is inadequate the denture may become unseated during formation of sounds having explosive effect like K,Ng, requiring the sudden repositioning of the tongue to control and stabilize the denture.

WIDTH OF DENTAL ARCH:If the teeth are set to an arch which is too narrow, the tongue will be cramped, thus affecting the size and shape of air channel. This results in faulty phonation of such consonants as T,D,S,M,N,K,C and H, where the lateral margin of the tongue make contact with palatal surfaces of upper posterior teeth.

RELATIONSHIP OF UPPER ANTERIOR TEETH TO LOWER ANTERIOR TEETHThe abnormal protrusive and retrusive jaw relations will effect the Ssound predominantly, as S sound requires near contact of upper and lower incisors, so that the air stream is allowed to escape through slight opening between teeth.

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SPEECH TESTS

⚫ The phonetic aspect of complete denture construction deserves equal consideration with esthetics and mechanics and should be checked at the time of waxed denture try-in, when it is possible to alter the palatal contour to accommodate speech articulation. The speech test should be made after satisfactory esthetics, correct centric relation, proper vertical dimension and balanced occlusion have been attained and after wax up for esthetics has been completed.

TEST 1:TEST OF RANDOM SPEECHEngagae the patient in a conversation and obtaining a subjective

speech analysis by asking the patient say hoe he feels,how his speech sounds to him and what words seem most duifficult to pronounce.

⚫ TEST 2: TEST OF SPECIFIC SPEECH SOUNDSThis is best accomlpished by having the patient say 6-8 words

containing the sound and then combining these words into a sentence.The following is the list of sounds to be tested

S,Sh Six, sixty, ships, sailed Mississippi, sure ,sign, sun, shine

Sixty six ships sailed Mississippi. Sure sign of sun shine

T,D,N,L Locator, located, tornado, near, Toledo

Locator located tornado near Toledo

Ch,J Joe, Joyce, joined, George, Charles, church

Joe and Joyce joined George and Charles at church

K Committee, convented, political, convention, Connecticut

The committee convented at the political convention in connecticut.

F,V Vivacious, Vivian, lived, five, fifty, five, fifth, avenue

Vivacious Vivian lived at five fifty-five fifth avenue

TEST 3: TEST OF READING A PARAGRAPHMake the patient read a paragaraph containing abundance of S, Sh, Ch sounds.

SPEECH ANALYSIS

⚫ A number of methods are vailable for speech analysis.They are basically two categories.

1. PERCEPTUAL/ACOUSTIC ANALYSIS2. KINEMATIC METHODS OF MOVEMENT ANALYSIS

⚫ WHY DO WE REQUIRE SPEECH ANALYSIS?

⚫ When apatient presents with speech pathology problems, their clarity and pronunciation should preferably analyzed by a speech pathologist. So it would be valuable to to speech analysis before starting prosthodontic treatment,just to establish a basis for future comparison and if possible identify problems.

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⚫ PERCEPTUAL/ACOUSTIC ANALYSISThis analysis is based on a broadband spectrogram

recorded by a sonograph during the uttering of different phases containing key phrases. By doing this objective opinion of certain sounds may be achieved.

⚫ KINEMATIC METHODS OF MOVEMENT ANALYSIS

⚫ X-ray mapping⚫ Cineradiography ⚫ Optoelectronic articulatory movement tracking⚫ Electropalatography

With the use of spectral analysis, a sound event can be split into 3 dimensions: frequency, amplitude, and chronologic sequence.

The data obtained can be visualized as a 2- dimensional Cartesian coordinates with the color or grey shade as the third dimension and this is called a spectrum graph or sonogram.

A direct 3- dimensional profile representation that is obtained on a computer screen is called spectrogram.

BROADBAND SPECTRAL ANALYSIS

A PICTURE SHOWING A SPECTRUM GRAPH OR A SONOGRAM

PICTURE OF A SPECTROGRAM (3 DIMENSIONAL VIEW)

PALATOGRAMS⚫ To study the normal contact for tongue in pronouncing the various

phonemes

⚫ HOW TO OBTAIN A PALTOGRAM????

A uniformly thin artificial plate of methyl metjacrylate resin is made for each subject. The plate is positioned in place,the subject is made to practice some speech sounds until they are clearly pronounced.

Trial test is made by having the subject pronounce a given sound and open his mouth without again contacting the palate with his tongue. The plate is then removed, thoroughly dried, dusted with non-scented talcum powder and carefully inserted in the mouth. The subject is asked to carefully pronounce the previously practiced sound and then the plate is carefully removed and examined.

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⚫ The moist tongue removes the powder from the area of contact leaving a clear tracing (palatogram) on the artificial palate. After a short period this area dries and the tracing becomes obscure.

⚫ In order to preserve the palatogram for future study, the contacted area is outlined with glass marking pencil immediately after the palate is removed from the mouth.

⚫ For edentulous patients, the outlined area is waxed and contoured, redusted and another palatogram is made on same trial base. The procedure is repeated until a normal tongue-palatal contact is established to improve the phonetics.

Palatograms :

• Leslie Allen (1958)

• No two individuals contacted exactly the same area –

similarity to constitute a pattern.

• S and SH – individual similarity and distinct pattern.

Study of vowels :

• Tongue – palatal contact for all except with |O|

• Phone |e| occurs singly

• U = (ee – oo) i = (i – ee)

Palatograms for consonants :

• Occurs in consort with vowels

Eg: t or d → occlusive articulation → e

a follows j & k.

e precedes s, n and l.

• Isolation of consonants on palatograms

➢ Consonant produced initially → vowel

➢ Consonant + O = may not be a standard English word.

Sequence of palatograms :

1. s & sh palatograms are made

sh line – guide for waxing posterior alveolar area

s line – anterior alveolar area

• Formation of groove

• Whistling or hiss – larger goove

• Lisp (th for s) or indistinct ‘s’ – inadequate groove

• Sears – creation of groove

2. Palatograms for plosives (t, d) are made

3. Palatograms for ch & j are made

• Midanterior alveolar wax up may flow on palate bit posteriorly.

ELECTROPALATOGRAPHY

EPG is used for registration of tongue contact patterns during speech production.

The equipment consists of 60-80 electrodes inserted into an individually made acrylic plate,covering the are fron front teeth to the soft palate.The electrodes react when the tongue is in contact with the palate.In this way ,untouched and touched electrodes can be recoreded at high frequency and mapping achieved of tongue pattern.

This method enables the diagnosis of some speech disturbances,but must be combined with other methods to achieve an exhaustive analysis

ELECTROPALATOGRAPHY

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SPEECH DEFECTS

TERMINLOGY RELATED TO SOME SPEECH DISTURBANCES

⚫ APHASIA (DYSPHASIA): Means defective speech due to damage of cortical area required for speech making. (Broca’s area, Wernicke’s area). Commonly this is due to thrombosis of feeding artery to the region affected. .

⚫ DYSARTHRIA: Motor speech problems caused not due to sensory loss or mental retardation.

⚫ DYSLALIA: An articulatory problem without apparent neurologic basis.

⚫ SPEECH AND LANGUAGE RETARDATION: Delay in acquistion of communicating skills.

DISORDERS OF SPEECH

Hypernasality (Rhinolalia aperta)

Hyponasality (Rhinolalia clausa)

Denasality

Eg: m, n & ng

b d g

Morning → bordig

NASAL BALANCE

➢ Replacement of intended oral consonants formed farther down the vocal tract.

➢ To prevent adverse effect of defective articulator.

Distortion

Eg: Vowel → pop for pipe

Consonants → cah for car

DISORDERS OF ARTICULATION

Substitution

Eg: teef for teeth Omission

Eg: bow for boat

TESTING FOR NASAL BALANCE

• Vowels = resonated sound + little air flow.

• ee and oo → hypernasality

• |m| → hyponasality

• Undue nasal bridge vibration.

• Alternate occlusion and opening of nostrils

• Nasal emission of air with voiceless consonants

TEST FOR ARTICULATION:

• Recording of abnormal sounds

➢Phonetic symbols on paper or electronically on tape, disc or

spectrogram.

• Talking when nostrils open or closed.

• Wrinkles on nasal alae.

• Abnormal tongue movement – palatal defect

Eg: ‘n’ in banana.

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RELATION TO MAXILLOFACIAL DEFECTS

Acquired

• Accidental or surgical

• Nervous system –cerebral palsy, lateral sclerosis, poliomyelitis, myasthenia gravis, myotonic dystrophy

• Functional

• Atypical articulation Urban speech nasal snort

Congenital

Cleft palate,

Short palate,

Large velopharyngeal space,

Limited velar mobility,

Submucous cleft palate

•Correction of palatal defect itself

•Goal

•Fistual / hole – flanged acrylic button

•Vellar defects – palatal lift Prosthesis

Device

CORRECTING DISORDERS OF SPEECH IN CLEFT PALATE CASES

Prosthodontist Surgeon

Substitution

PALATAL DEFCTS AND OBTURATORCORRECTING SPEECH DEFECTS RELATED TO IMPLANT PROSTHESIS

A fully bone anchored prosthesis in maxilla can cause phonetic problems, due to the space between the prosthesis and residual ridge.

Normal pronunciation is possible after approximately 3 months, but can take as long as one year for speech recovery.

To correct this errors in speech, removable appliances like artificial gingival extensions made of silicones or resin materials should be given to close the gaps and also for esthetic purposes.

IMPLANT PROSTHESIS

SPECIAL CONSIDERATIONS OF PHONETICS

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TOTAL LARYNGECTOMY :

Rehabilitated by →

• Training in oesophageal speech.

• Using electric artificial larynx

• Asai technique

➢ Epithelial lined tube

➢ Excellent sound quality

➢ Aspiration of saliva and food

Labio dental – f & v

Bilabial closure

S, Z, L

‘th’ in | | | |

COSMETIC MODIFICATION OF ORAL

CAVITY

PHONETIC TECHNIQUE OF BORDER MOLDINGOF NEUTRAL ZONE IMPRESSION FOR MANDIBLE

JOSEPH EM et al, utilized both swallowing and phonetic techniques for making mandibular impression. Border molding of phonetic neutral zone was done using a tissue conditioning material mixed in 1:1 ratio.

The subject was asked to pronounce phoneme “SIS” 5 times followed by phoneme “so” once. These phonemes were used for molding the lateral segments of the tray. For the molding the anterior segment the subject was asked to pronounce successively the phonemes “DE”, “TE”, “ME”, “PE”, “SE” vigorously. The denture fabricated using this technique was narrower in the posterior region as compared to that of swallowing technique.

Involuntary, ceases on waking.

Vibration on inspiration.

Mouth breathing

Sleeping on back

No definite modality

Obstruction

Resistance to respiration

Pulmonary ventilation

Anoxia ( Co2)

Tone of breathing

Vibration of soft palate

Robin (1968) Adenoids & tonsils

Allergy, DNS,

Collapsed alae nasi

SNORING

•REVIEW OF LITERATURE

SIMON CLARENCE, discusses the relation of oral structures and speech. He states that although teeth are passive, they play an important role in speech. They serve as barriers to exhaled current of air and thus set up eddies in air stream which are interpreted as intelligible speech. If there are edentulous spaces in the anterior region, or if anterior teeth are irregular , the tongue cannot regulate the degree of closure, and sound substitution results and due to this labiodental and interdental fricatives as well as fricatives are most commonly affected.

ETTORE SEBASTIAN states that although teeth are important factors in articulation, their presence is not essential for articulate speech because almost all sounds can be formed by edentulous patients.

RITCHIE AND ARIFFIN reported speech defects caused by different incisor positions in maxillary incisors irrespective of the shape of palatal vault and found that a displacement of maxillary incisors in labial direction was most likely to cause speech problems

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SAIZER PEDRO AND TENCH , sates that excessively high lower denture not only causes functional and esthetic difficulties but also gives rise to impaired speech production. If the teeth are placed high in lower dentures, the upper half of anterior 3rd of tongue does not function well above the lower denture when the patient speaks. They are of the opinion that mandibular dentures should not occupy more than one half of the space existing between the edentulous ridges.

SAIZER PEDRO studied the effect of lower dentures on speech and states that widening of lower arch improves defective pronunciation, when there is less tongue space due to constricted palatal arch

KESSLER states that if position of artificial teeth do not deviate too much from those of natural teeth, compensation of minor abnormal speech habits (that have already been established due to long periods of edentulism and old age) will occur in most patients.

He also reported that occasionally, stippling and carving give rise to frictional interferences with free movements of the upper lip during speech, resulting in distortion of speech sounds.

He also states that reproduction of rugae in artificial acrylic dentures makes the denture base too thick in the region just lingual to the anterior region. This leads to phonetic difficulties, particularly in production of T and D sounds.Thinner and more accurately contoured rugae in metal dentures seem to be better in this respect

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ROTHMAN states that if dentures are correct phonetically for the consonants, the vowel sounds generally present no trouble at all.

WEPMAN states that prolonged edentulous periods may cause changes in the position of the arches formed by the anterior faucial pillars. This may result in change in the resonance after teeth are restored.

SAGGERS recognizes the importance of making thin dentures as these do not in any way hinder the free movement of the tongue. He states that arch formations encroaching on space normally occupied by tongue will cause faulty articulation.

ROTHMAN pointed that tongue contacts a specific part of the teeth, alveolar ridge, or hard palate during the production of each consonant. As these structures are covered or replaced by denture, an appropriate restoration is necessary for undisturbed sound production. Disturbed pronunciation may result as direct influence of artificial teeth and palate on air flow but also may be caused by a different tongue position or movement.

TANAKA, found that artificial palatal vaults of maxillary dentures often have a concave shape. In contrast natural palatal vaults are convex shape in alveolar region. He concluded that palatal vaults of maxillary dentures should be shaped like natural ones to facilitate correct pronunciation. He also reported that quality of speech sound production improved with in the first week of insertion of new denture

MARTONE, in a series of articles reviewed the physiology of speech and, subsequently, discussed which defects might occur. These defects may be attributable not only to the dentures but also to ill health or age changes. Defects in pronunciation may occur because of loss of lip support, errors in tooth positioning, tongue spread, increased facial height, or the patients inability to exert fine control over the soft tissues.

ROTHMAN reported that, because speech is an essential human activity, phonetics must be considered one of the cardinal factors contributing to the success of complete dentures. To use speech as part of a complete denture fabrication technique, he examined palatograms to determine where oral contacts occurred in an attempt to prescribe an appropriate denture design.

VINCOFF employing palatogram studies on a group of persons who had their natural teeth and normal speech, found that the palatograms made for T,D,N and L are not distinguishable frl one another.

BENEDIKTSSON stated that during normal /S/ sound production, the sides of tongue are against the alveolar ridges and gingival margin areas of the maxillary teeth and that the middle of the tongue is lowered to create a groove. At the same time, the tip of tongue contacts the palatal surfaces of the maxillary teeth or alveolar ridge.

HAMMOND et al, reported that speech sounds like /S/, /Sh/, /Th/, and /T/ were most affected sounds by an increase or decrease in VDO.

BANKSON AND BYRNE, who examined the effect of missing incisors on the consonant phonation of children, and reported that among the examined consonants, only S sound was affected.

HEYNICK et al, found that 28(21%) of 131 denture wearing individuals from elderly Dutch population had speech problems, especially in the pronunciation of S sound among the sounds formed in the anterior maxillary region, because S sound production requires particularly fine adjustments of the tongue and neuromuscular abilities, which are decreased in old age .

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CHRISTOPH RUNTE et al studied the influence of maxillary central incisor position in complete dentures on S sound production and concluded that the labial angulation seemed to have greater effect on palatal angulation.

HEYDECKE G, Mc FARLAND DH, et al conducted a study with maxillary implant prosthesis. They concluded that maxillary implant overdentures with and without palates enable patients to produce more intelligible speech than fixed prosthesis.

LUNDQUIST et al reported that the gap between mucosa and fixed prosthesis is thought to be major cause of speech errors and this gap can be closed by removable appliances, but these usually cover the palate that may interfere with speech.

BAWN , Mc FARLAND et al said that when palate of dentate object is covered experimentally, the articulation of consonants is often abnormal even after prolonged periods of adaptation.

DAWN EILEEN in reviewing oral anomalies and speech defects, writes that organic causes of speech defects, include any diseases or injury of the larynx that results in vocal distorttion, abnormal conditions of nasopharyngeal tract, anatomic defects such cleft lip, tongue tie, abnormal uvula and abnormal conditions of jaw. Other speech defects are cased by neurologic disorders, chorea and muscle spasms and endocrine disturbances.

CONCLUSION

⚫ The specific relation between dentistry and speech pathology is still emerging. As orodental morphological features influence an individuals speech, the dentist should recognize the role of prosthetic treatment on speech activity. Thus the treatment objective of every dentist should be to make dentures which are not only mechanically functional, esthetically pleasing, but also phonetically accurate.

REFERENCES

⚫ Zarb-Bolender, Boucher’s text book of prosthodontic treatment for edentulous patients,complete dentures and implant-supported prosthesis, edn 11th,St. Louis: Mosby 2004.

⚫ Sharry’s text book of complete denture prosthdontics,ed 2nd,McGraw-Hill ,Inc. 1968

⚫ H.B.R.Fenn’s text book of clinical dental prosthetics,2nd

edn,

⚫ Sheldon Winkler’s, Essentials of complete denture prosthodontics,2nd edn, Ishiyaku Euro America publishers,Inc.2000

⚫ Charles M.Heartwell,Arthur O .Rahn, Syllabus of complete dentures,4 th edn,Verghese publishing house,1992

⚫ William R Laney, Joseph A Gibilisco, Diagnosis and treatment in prosthodontics,1st edn,1983

⚫ Guyton, Hall ,Textbook of medical physiology.10th edn

⚫ Timothy s Miles, Brigette Nauntofte, Peter svenson,Clinical oral physiology

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⚫ Allen .R , Improved phonetics in denture construction, JPD 1958;8;753-763.

⚫ J.F. McCord, H.J. Firestone, A.A. G rant. Phonetic determinants of tooth placement in complete dentures. Q.I 1994;25(5);341-345

⚫ John M. Palmer, Structural changes for speech improvement on complete upper denture fabrication. JPD-May 1979,volume 41(5);507-510

⚫ Meyer M. Silverman, a classic article on The speaking method in vertical dimension,JPD,85(5); May 2001

⚫ Christoph Runte, Spectral analysis of S sound with changing angulation of maxillary central incisors, IJP 2002;15;254-258.

⚫ George A. Murrel, Phonetics,function, and anteriorocclusion;JPD – july,1974;23-31

⚫ Earl pound, Utlizing speech to simplify a personalizeddenture service; JPD ,24(6);Dec,1970;586-600

⚫ Tanaka H, speech patterns of edentulous patient’s andmorphology of the palate in relation to phonetics. JPD1973,29;16-28.

Thank you

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POSTERIOR PALATAL SEAL

DR. SUDHIR MEENA

CONTENT

• Introduction

• Parts of PPS

• Structures that guide PPS

• Anterior and posterior vibrating line

• Soft palate

• Techniques for developing PPS

• Functions

• Clinical considerations

• Conclusion

INTRODUCTION

Definition : That portion of the intaglio surface of a maxillary removable complete denture, located at its posterior border, which places pressure, within physiologic limits, on the posterior palatal seal area of the soft palate; this seal ensures intimate contact of the denture base to the soft palate and improves retention of the denture. (GPT-9)

• The peripheral seal of a maxillary denture is the area of contact between the mucosa and the peripheral surface of the denture, which prevents ingress of air between the denture and the soft tissues.

• This seal depends upon proper placement and extension of the posterior border of the denture.

• Terminating the denture borders on the soft palate will allow the mucosa to move with the denture base thereby maintaining the seal.

Reference: Manapapllil’s textbook for complete denture

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Parts of PPS

• Pterygomaxillary seal

• Post palatal seal

• Posterior Palatal Seal consists of two separate but confluent areas: Pterygomaxillary seal, which extends through the pterygomaxillary notch/ hamular notch and continuing for 3-4mm antero-laterally approximating the mucogingival junction & Post palatal seal which extends medially from one tuberosity to the other. PPS area lies between the anterior and posterior vibrating lines.

• Pterygomaxillary notch is the palpable notch formed by the junction of the maxilla and the pterygoid hamulus of the sphenoid bone.

• The postdam is a raised portion of the denture base at the posterior extent of the upper denture and is located on its fitting surface. It extends bilaterally from the midline to the pterygomaxillary notch regions and lies on a displaceable portion of the junction of the hard and soft palates, which appears clinically immobile during phonation.

• Maxillary tuberosity and hamular notch.

STRUCTURES THAT GUIDE PPS FOVEA PALATINI

• Fovea palatine are the ductal opening into which ducts of other palatal mucosal glands drains.

• They do not represent the junction of hard and soft palate .

• Guidelines to the placement of posterior palatal seal.

According to a study fovea palatina :-

• In 7% of subjects they are located within 1to2 mm posterior to the vibrating line.

• In 18.8% it lies within 2to3 mm posterior to the vibrating line.

• In 27.1% it lies within 3to4 mm posterior to the vibrating line.

• In 16% it lies within 4to5mm posterior to the vibrating line

• In 4.9% within 5to6 mm posterior to vibrating line

• 1.4% more then 6mm posterior to the vibrating line.

Reference article: Reliability of the fovea palatini for determining the posterior border of the maxillary dentureM S Chen

Anterior and posterior vibrating line.

• Posterior palatal seal area lies between anterior and posterior vibrating line.

• Location varies with contour of hard and soft palate .

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Anterior vibrating line

• Lies at the junction of attached tissues of the hard palate and movable tissues of the soft palate.

• Not a straight line due to posterior nasal spine.• Always on the soft palate.• Methods to determine :-1. Valsalva maneuver -

- with nostril held firm- blow gentle through the nose.

2.“ah” with short vigorous bursts.

Posterior vibrating line.

• Its an imaginary line at the junction of aponerosis of tensor veli palatine muscle and muscular portion of the soft palate.

• Most distal extension of the denture.

• Method :-

• “ah” in short bursts in a unexaggerated fashion.

Soft palate.

• Is a movable , muscular fold ,suspended from the posterior border of the hard palate.

• Mucosa over here is transition between fixed and loosely types, so why some soft palates afford desirable posterior seal area and others less desirable.

• House Classification:-

1. Class I

2. Class II

3. Class III

Soft palate

• Class I :-

1. Horizontal as it extends posteriorly.

2. Minimum muscular activity

3. More then 5mm of movable tissue available

4. Wide posterior palatal seal.

5. More tissue surface can be covered.

6. More retentive and most favorable.

7. Posterior borders can be made fairly thin up to 1to 2 mm.

Class II

• Which lies between class I and class III

• 1 to 5 mm of movable tissue available

• Good retention is usually possible.

• Soft palate turns downwards at 45 degrees from hard palate.

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• Class III:-

1. Acute contour in relation to hard palate, palate turns downwards at 70 degrees.

2. Smaller area for posterior palatal seal area .

3. Less then 1mm of tissue available

4. Usually with “v” shape palatal vault.

5. As little or no area for posterior seal so the borders can be made thicker (3 to 5mm).

6. Sudden drape of soft palate.

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CROSS SECTIONAL VIEW OF VARIOURS PPS

winland and young, maxillary complete denture posterior palatal seal: variation in shape, sizeand location, prostho dent, march 1973

• Bead

• Double Bead

• Butterfly

• Butterfly With Bead

Various shapes of posterior palatal seal

• A bead posterior palatal seal extending through the hamular notch

• Double bead posterior seal

• A butterfly posterior palatal seal

• A butterfly posterior palatal seal with a bead on the posterior limit of the denture

• A butterfly posterior palatal seal with the hamular notch cut to half a depth

Techniques for developing posterior palatal seal.

• Many techniques have been suggested in literatures .

• They are:-

1. Conventional

2. Fluid wax

3. Arbiratory scrapping

4. Bouchers

5. Extended palatal

Examination and marking• Stage of recording: at the start of jaw relations.

• Advantages:-

1. Trial denture will be more retentive.

2. Accurate maxillomandibular records.

3. Patient and clinicians can experience retentive qualities in trial denture

4. Extent of posterior border can be experienced

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Disadvantages

1. Not a physiological technique2. Over compression

MATERIALS:A.”T”BURNISHER OR MOUTH MIRRORB.INDELIABLE PENCILC.WELL ADAPTED RESIN OR SHALLAC TRAYD.KINGSLEY SCRAPER

• All the procedures for location and transfer marking of the anterior and posterior vibrating lines are same as for the conventional approach.

• Indelible transfer markings are recorded on the final wash impression.

• Designed to flow at mouth temperature.

• The melted wax is painted onto the impression surface with the outlineof the seal area and allowed to cool to below mouth temperature toincrease its consistency and make it more resistant to flow.

• The impression is carried to the mouth and held in the place undergentle pressure for 4-6 minutes to allow time for the material to flow.

• After 4-6 minutes, the impression tray is removed from the mouth andthe wax examined for uniform contact through out the posterior palatalseal area.

• If tissue contact has not been established, the wax will appear dull. Ifthe tissue has been contacted, the wax will have a glossy appearance.

• Where the wax appears dull, more wax should be applied and theprocedure repeated.

• The secondary impression is reinserted and held for 3-5 minutes of firmpressure applied to the midpalatal area of the impression tray.

PRECAUTIONS

• The patient should not protrude his tongue beyond theapproximated position of the incisal edge as this may shortenthe posterior border of the final impression.

• The patient should be cautioned against rinsing with coldwater as this may contract the tissues and reduce the flowproperties of wax.

• The borders of the wax should terminate in feather edge towards the vibrating line .If a butt joint is formed, proper flow may have not taken place.

• Advantages:

1. Is a physiological technique

2. Over compression is avoided

3. Mechanical scrapping is avoided

4. Posterior palatal seal is incorporated in the trial denture.

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Disadvantage:

• Time consuming

• Handling of the materials is difficult.

• Materials :

Wax-

1.IOWA WAX (white)

2.KORECTA WAX (orange)

3.H-L PHYSIOLOGICAL PASTE

(yellow white)

4.ADAPTOL (green)

EXTENDED PALATAL TECHNIQUE(Silverman 1971)

•Denture border is extended 8mm approximately beyond the anterior vibrating line.•Not widely used currently.

•Method -1.After border molding tray is extended by adding compound.

2.Green stick compound is added to the seal area and record is made with head flexed 30 degree downward.

BOUCHERS TECHNIQUE

• Stage of recording- during jaw relations

• Method: the posterior vibrating line is located and transferred on to the master cast.

• The temporary denture base is reduced to this line.

• This will create a raised narrow and sharp bead along the posterior portion of the denture which sinks into the tissues and forms a seal.

• Advantage: According to Boucher a narrow bead like seal is more effective.

Arbiratory scrapping.

• Least accurate

• Most unphysiological

Adding PPS to a pre-existing denture

• There are times when a completed denture is deficient in the posterior palatal seal area. The deficiency may be either in depth or in the length of the denture base, or in both.

• Method : utilizes the fluid wax technique. All of the steps outlined for locating, marking, and placing the wax in the seal area are followed, except that this time the wax is placed on the processed denture base. An indelible pencil is used to outline the anterior extent of the seal on the denture. Fluid wax is painted in PPS area. After the PPS is recorded (4-6 mins.), the denture is removed from the mouth. Stone is vibrated into the denture wax surface.

• After the stone has set, the wax is eliminated. The auto polymerizing acrylic powder is sprinkled between the denture base and the cast while holding on a vibrator. The monomer is then added drop wise. The denture is then replaced on the stone cast and held firmly with rubber bands. They are then placed in a pressure pot with water (140 (F) for 20 minutes under 30-psi pressure. After the cast and denture are separated, the excess acrylic is trimmed and the border polished lightly. The denture should be stored in water for 24 to 36 hours to reduce harmful residual monomer.

By: Moghadam and Scandrett

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Functions

• In complete maxillary prosthesis:-

1. Primary purpose is to maintain retention of the maxillary denture .

2. Maintain contact with anterior portion of the soft palate during functional movement( i.e. mastication,deglutation ,& phonetics)

3. Reduce awareness of the posterior palatal area with subsequent reduce in gag reflex.

4. It provides a thick border to counteract denture shrinkage.

5. Reduces/ prevents food accumulation under the denture.

6. Reduces tongue irritation as posterior border merges better with palate.

REVIEW OF LITERATURE

• 1958, Hardy and Kapur stated - Retention and stabilityderived from the forces of adhesion cohesion and interfacialsurface tension resist only the dislodging forces actingperpendicular to the denture and fail to resist thedislodgement of the dentures by horizontal forces and lateraltorques.

• This dislodgement can be resisted by the retention provided bythe partial vacuum created by the denture border seal.

• In the posterior region sealing is done by developing aposterior palatal seal.

• Such a seal will create a partial vacuum that will not operatecontinuously, but one that will come into play only whenhorizontal or tipping thrusts tend to dislodge the denture andthen only long enough to overcome the emergency.

• This partial vacuum is unlikely to operate long enough to doany damage to the supporting or border tissues.

• Sidney Silverman (1971) conducted a study and concluded complete maxillary dentures can be extended for an average of 8.2mm dorsally to the vibrating line or flexion line, where the soft palate joins the hard palate.

• This extension varies from 4-12mm dorsally to a transverse region.

• Antolino Colon, Keki Kotwal and DavidMangessdorff (1982) found that the form of thepalate has direct influence on the retention ofcomplete dentures and will aid in the selection of thetype of posterior palatal seal needed.

• Rajeev M. Narvekar and Marc B. Appelbaum in1989 used ultrasound instrumentation as an non-invasive procedure to locate the anatomicstructures in the PPS region.

• In 1997, Izharul Haque Ansari described a methodto establish posterior palatal seal during the finalimpression stage.

A comparative study of retention of complete denture base with different types of posterior palatal seals - an in vivo study.ClinCosmetInvestigDent

• AIM To evaluate retention of complete denture base with different types of posterior palatal seals.

• MATERIAL AND METHODS Ten male patients between the age group of 50 years to 60 years were selected for the study. After the primary and secondary impressions were taken, five casts were made including a cast without posterior palatal seal, a cast with single bead posterior palatal seal, a cast with double bead posterior palatal seal, a cast with butterfly shaped posterior palatal seal, and a cast with posterior palatal seal with low fusing compound by functional method.

• RESULTS It was observed that retention increased up to 108% in the posterior palatal seal with low fusing compound with functional method and the posterior palatal seal that was obtained by using functional method provided greater retention than a denture base without posterior palatal seal.

• CONCLUSION It was concluded that the incorporation of a posterior palatal seal is important for obtaining optimum retention of the maxillary complete denture.

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A study of correlation between posterior palatal seal width and soft palatal angulation with palatal contourRupalJ. Shah,Sanjay B. Lagdive,DivyeshkumarB. Modi,BhavyataDarji,VedanshiA. Amin,andGhanshyambhaiC. Patel

• Aims: The study was carried out to evaluate the relationship between PPS width of the patient intra-orally and cephalometric tracing of the same patient. Second part of the study was formulated to determine whether the anterior and posterior vibrating lines can be distinguished as two separate lines by different observers.

• Materials and Methods: A lateral cephalogram was made to trace the hard and soft palatal contour, and the angle of the palatal contour was measured with the v-ceph program. Correlation analysis was conducted to examine the relationship between the distance from anterior to posterior vibrating lines and the angle of the palatal contour at the junction of the hard and soft palate.

• Statistical Analysis Used: The data were analyzed using the Karl Pearson Correlation test.

• Results: Correlation of the angle of the palatal contour to PPS width, showed perfectly positive value; whereas, correlation of angle between anterior nasal spine-posterior nasal spine (ANS-PNS) and PNS-Uvula (U) to PPS width showed partially positive value.

• Conclusion: The correlation of angle between hard tissue and soft tissue to PPS width, and the angle between ANS-PNS and PNS-U to PPS width, increases with an increase in PPS width.

Evaluation of the conventional method for establishing the posterior palatal sealAuthor links open overlay panelAlaa’aM.Salloum

• Objective Providing sufficient posterior palatal seal (PPS) of a maxillary denture is necessary for retention. This research was designed to estimate the arbitrary scraping method used for establishing the PPS.

• Methods and material Eight complete edentulous patients were selected. They received conventional complete dentures by using a scraping method for establishing the PPS. The posterior retention of the maxillary dentures was measured, the postpalatal area for each patient was visually estimated, and smears were made from the postpalatal areas at insertion appointment, 7, 30, and 90 days after denture placement.

• Result The study revealed that the posterior retention of the maxillary dentures did not change during the stages of the study, and the epithelium of the postpalatal area converted gradually to a keratinized one.

• Conclusion It is concluded that the scraping method used for establishing the PPS is an effective and safe technique.

Clinical considerationsConclusion

• The construction of a posterior palatal seal varied greatly and is developed as early as the maxillary final impression and as late as processing of the denture

• Its outline varies with the place ability of the tissues along the vibrating line

• A careful examination of anatomic structures prior will not only aids in maximum retention of the complete denture but it also encourages the patient psychologically.

References

• Complete denture prosthodontics – John J. Manappallil

• Zarb Bolender, Mosby,Prosthodontic treatment for edentulous patients,12th edition

• Sheldon Winkler ,A.I.T.B.S. Publishers,Essentials of complete denture Prosthodontics,2nd edition

• Arthur O. Rahn & Charles M. Heartwell, Elsevier,Textbook of complete dentures,5th edition

• B.D. Chaurasia , Human Anatomy- Vol.3 Head and Neck

• Internet sources

• Posterior Palatal Seal (PPS): A brief review Ali Mariyam, Verma AK, Chaturvedi Saurabh, Ahmad Naeem, Shukla Anuj

• Prosthetic treatment of the edentulous patient – R M Basker and J C Davenport

• Kwabe’s complete denture

• Textbook of Prosthodontics – Deepak Nallaswamy

• Textbook of Prosthodontics – Ranjarajan

• The Posterior palatal seal- a review RL Ettinger, FR Scandrett

• Boucher C.O. Swenson's Complete Dentures

• Establishing the posterior palatal seal during the final impression stage – I H Ansari- the journal of prosthetic dentistry

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Rationale of dental implant

DR. SUDHIR MEENA

◼ According to MISCH the primary reason for suggesting the fixed partial denture over implant are its clinical ease &reduced treatment time but it is not the best alternative to replace missing tooth , he said if this concept is expanded ,extractions would replace endodontics, removable partial denture could replace fixed partial denture & complete dentures even could replace orhtodontics

OPTIONS FOR REPLACING MISSING TEETH(ON BASIS OF SUPPORT)

◼ IMPLANT SUPPORTED PROSTHESIS◼ FIXED PARTIAL DENTURE

▪ TRIDITIOINAL FIXED PARTIAL DENTURE

▪ CANTELIVER FIXED PARTIAL DENTURE ▪ RESIN-BONDED FIXED PARTIAL DENTURE

◼ REMOVABLE DENTURE▪ PARTIAL DENTURES ▪ COMPLETE DENTURES

ADVANTAGE OF SINGLE TOOTH IMPLANT

◼ High success rate (better than 97% for 10 years )◼ Decrease risk of caries of adjacent tooth◼ Decrease risk of endodontic problem of adjacent

teeth◼ Improved hygiene ◼ Decrease cold or contact sensitivity of adjacent

teeth◼ Psychological advantage ◼ Decrease abutment tooth loss◼ Preserves bone of edentulous area

ADVANTAGE OF IMPLANT OVERDENTURE

◼ Minimum bone loss◼ Improved retention, stability, support,

esthetics, phonetics, chewing efficiency & force

◼ Reduced prosthesis size ◼ Decrease soft tissue abrasion

SINGLE –TOOTH REPLACEMENT WITH FIXED PARTIAL DENTURE

◼ Most common treatment ◼ Less time required◼ Few bone & soft tissue considerations ◼ Restoration of function & esthetic◼ Better proprioception

ADVANTAGE

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DISADVANTAGE ◼ 1986 Walton et al (1986 ) reported mean life span

of 9.6 years ◼ Caries & endodontic treatment of abutment teeth

are most common complications◼ Increased plaque retention around pontic ◼ Damage to healthy tooth◼ Failure of prosthesis related to loss of abutment

teeth 8% -18% within 10 years ◼ Do not maintain bone

◼ Unfavorable outcome include not only the need to replace the failed prosthesis but also the loss of an abutment &need for additional pontics & abutment teeth in replacement bridge

SINGLE –TOOTH REPLACEMENT WITH REMOVABLE PARTIAL DENTURE

◼ Hygiene◼ Soft tissue replacement in esthetic zone◼ Maxillary lip support in gross defect ◼ Minimum tooth preparation ◼ Reduced cost

ADVANTAGE

DISADVANTAGE

◼ Bulk ◼ Bone loss( due movement in speech &

phonetics ) ◼ Highest loss of abutment teeth (upto

44%within 10 years )as reported by Shugars in J.A.D.A 1998

Thank you

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RESTORATION OF CONGENITAL AND

ACQUIRED INTRAORAL AND EXTRAORAL DEFECTS

DR. SUDHIR MEENA

Definition;Maxillofacial prosthodontia is the art and science of functional, or cosmetic reconstruction by means of non-living substitutes for those regions in the maxilla, mandible, and face that are missing or defective because of surgical intervention, trauma, pathology, or developmental or congenital malformation.

Maxillofacial prosthodontics is the branch of prosthodontics concern with restoration or replacement of the stomatognathic and craniofacial structure with prosthesis that may or may not be removed with regular or elective basis.-

CLASSIFICATION OF MAXILLOFACIAL PROSTHESES

A wide variety of maxillofacial prostheses are being fabricated in practice. Based on the location, use, and area of restoration, maxillofacial prosthesis can be classified as follows:

Prosthesis:

IntraoralMaxillary

. Congenital- Cleft lip- Cleft palate

Acquired

⚫ Total maxillectomy

⚫ Complete dentures⚫ Partial dentures

⚫Obturators⚫ Speech aids

⚫ Implants⚫ For partial maxillectomy

⚫ Complete dentures

⚫ Partial dentures

MandibularCongenital⚫ Cleft lip⚫ Early feeding devices⚫ Surgical.⚫ Orthodontic.⚫ Prosthodontic.⚫ Fixed partial dentures⚫ Complete dentures – ImplantsAcquired⚫ Complete dentures⚫ Partial dentures⚫ Flange prosthesis⚫ Mandibular exercisers - Implants

Extraoral

⚫ Auricular prosthesis

⚫ Ocular prosthesis

⚫ Orbital prosthesis

⚫ Nasal prosthesis

⚫ Composite prosthesis

⚫ Lip and cheek prosthesis

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Treatment supplements:

Radiotherapy supplements- Stents- Splints- Shields- Carriers-Positioners

Radiation appliances. Surgical supplements- Prosthetic dressings- Surgical splints-Surgical obturators

MAXILLARY DEFECTSPatients with maxillary defects will have difficulties in

mastication, speech and deglutition. The aim of a maxillofacial prosthesis should be to restore the normal physiological function in these patients. The fabrication of the various prosthesis used in the management of these defects are described in the next chapter.

Types of Maxillary DefectsMaxillary defects can be broadly classified as follows:Congenital⚫ Cleft lip⚫ Cleft palateAcquired⚫ Total maxillectomy

⚫ Partial maxillectomy

Congenital Maxillary DefectsCleft lip and cleft palate;

Cleft lip occurs due to improper fusion between the fronto-nasal and maxillary process. If this occurs on one side it leads to

a unilateral cleft. If it occurs on both sides, it leads to a bilateralcleft.

Veau's Classification of Cleft PalateVeau (1922) classified cleft palate into four types mainly,

⚫ Class I: Cleft involving the soft palate. It can also be a sub-mucous cleft, which appears normal

⚫ Class II: A midline cleft involving the bone, present only on theposterior part of the palate

⚫ Class III: A unilateral cleft extending along the mid-palatinesuture and a suture between premaxilla and palatine shelf

⚫ Class IV: A unilateral cleft extending along the mid-palatinesuture and both the sutures

Prosthetic consideration; For young patients, a permanent prosthesis

should not be provided, instead, a well fitting interim prosthesis should be provided. This interim prosthesis is replaced with a permanent one at around 25 years of age. A removable interim partial denture is preferred over a fixed prosthesis because it is more aesthetic in reproducing gingival contour, and it also helps to cover an unaesthetic residual alveolar cleft. The most important concern in the restoration of these cases is establishment of aesthetics.

Posterior cleft palate cases are usually treated using speech bulbs and palatal lift prosthesis. These maxillofacial prosthetic appliances are usually combined to the conventional prosthesis (RPD, CD, FPD) that may be required for the patient.

Types of Acquired Maxillary Defects

Acquired maxillary defects are usually classified based on their extent. If both the maxillae are resected, the defect is considered as total maxillectomy. Resection of one or a part of the maxilla or palate is considered as Partial Maxillectomy.

Aramany proposed a classification of partial maxillary defects based on their extent.

⚫ Class I: It is a unilateral defect involving one half of the arch and the adjacent palatine shelf. The defect extends to the midline (all the teeth in that side of the arch are missing)

⚫ Class II: It is a unilateral defect involving one side of the arch posterior to the canine (teeth posterior to the canine are absent)

⚫ Class III: It is a defect involving the centre of the

palatine shelves (all the teeth are present)

⚫ Class IV: It is a bilateral defect involving the one side

of the arch along with the entire premaxilla (all

anteriors along with the posteriors of one side are

missing)

⚫ Class V: It is a bilateral posterior defect (teeth

anterior to the second premolar are present)

⚫ Class VI: It is a bilateral anterior defect (teeth

anterior to the second premolar are absent).

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⚫Mandibular Defects⚫ Congenital Defects of the Mandible⚫ Congenital mandibular defects that require a

maxillofacial prosthesis are uncommon. Common congenital defects of the mandible include micrognathia, mandibulofacial dysostosis, ankylosis of the temporomandibular joint, etc.

Acquired Defects of the MandibleAs mentioned for the maxilla, neoplastic

resection is one of the most common causes for an acquired mandibular defect. The common neoplasia which advocate the need for resection are squamous cell carcinoma of the tongue, oropharynx and floor of the mouth.

Types of Acquired Mandibular DefectsBased on the amount of resection or bone loss (extent), mandibular defects can be classified as follows:

⚫ . Continuity defect: Here the superior portion of the mandible is resected and the lower border is left intact. These defects do not show any deviation and are easy to restore

⚫ Discontinuity defect: Here the entire segment of the mandible is resected. Since there is no connection between the remaining parts of the mandible, there will be midline deviation of the mandible due to the movement of the bone. Deviation may also occur when the remaining ends are surgically approximated in order to produce continuity.

VELO-PHARYNGEAL DEFECTS.They are basically defects of the palate, which effects

the closure of the naso pharyngeal and oro-pharyngealishtumus. This lack of closure will effect speech.

Treatment of Velo-pharyngeal Defects⚫ Congenital velo-pharyngeal defects due to palatal

insufficiency can be restored by surgical reconstructionfollowed with the insertion of an obturator to correct theresidual palatal insufficiencies.

⚫ Congenital velo-pharyngeal defects due to poor structuralintegrity can be treated with palatal surgery.

⚫ Acquired velo-pharyngeal defects due to surgicalresection can be treated by surgical reconstruction andprosthodontic rehabilitation (E.g. obturator).

⚫ Acquired velo-pharyngeal defects due to trauma andneurological deficiencies can be treated by prosthodonticrehabilitation using a palatal lift prosthesis.

EXTRAORAL DEFECTSDefects occur due to trauma,

neoplasm or congenital malformationThe common neoplasia of the head and neck include:

⚫Epithelial tumours: epithelial facial tumours may have a melanocytic, keratinocytic or adrenal origin.

⚫Connective tissue tumours: adenomas, fibromas, leiomyomas and lymphomas.

⚫ include:

Extraoral congenital malformations that

require maxillofacial prostheses include:

Auricular defects:

1. Microtia (small ear) associated withatresia of the external auditory meatus.

2. Anotia (complete absence of the auricle).

3. Smaller ear defects.

Nasal defects:

⚫ The defects arising due to surgery are

known as Rhinotomy defects.

⚫ Ocular defects: It involves the defects in the eyeball with intact eyelids (lacrymal apparatus. An orbital defect involves both the eyeball and the eyelids. Most of the ocular defects are acquired (by surgical procedures like evisceration-removal of the eyeball preserving the sclera, enucleation and excentration).

⚫ Lip and cheek defects like double lip, hemifacial microsomia etc.

⚫ Combination of the above mentioned defects.

⚫ Aesthetics is the major principle behind the placement of these prosthetic appliances. Hence, most of these prostheses are non-functional.

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THANK YOU

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RESIDUAL

RIDGE

RESORPTION

DR. SUDHIR MEENA

CONTENTS

•Introduction.

•Basic concept of bone.

•Mechanism of bone resorption

•Pathology of RRR

•Pathophysiology of RRR

•Pathogenesis of RRR

•Changes in maxilla and mandible

•Epidemiology of RRR

•Etiology of RRR

•Calcium homeostasis and RRR

•Osteoporosis and RRR

•Management of RRR

•Summary

•Conclusion

•References

Introduction

Residual ridge is a term used to describe the

shape of the clinical alveolar ridge after healing

of bone and soft tissues after tooth extractions.

It consists of the denture-bearing mucosa,

submucosa and periosteum, and the underlying

residual alveolar bone.

•After tooth extraction, a cascade of inflammatory

reactions is immediately activated, and the extraction

socket is temporarily closed by the blood clot.

•Epithelial tissue begins its proliferation and migration within the first week and the disrupted

tissue integrity is quickly restored.

•The most striking feature of the extraction wound

healing is that even after the healing of wounds, the

residual alveolar ridge bone undergoes a life-long

catabolic remodeling.

•The size of the residual ridge is reduced most rapidly in

the first 6 months, but the bone resorption activity

continues throughout life at a slower rate, resulting in

removal of a large amount of jaw structure.

•This unique phenomena has been described as

RESIDUAL RIDGE RESORPTION (RRR).

•The rate of RRR is different among persons and even at

different sites in the same person.

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The mechanical aspect of bone remodeling is usually associated with Wolff’s law of bone transformation (1892) which states that “EVERY CHANGE IN THE FORM AND FUNCTION OF BONE , OR OF THEIR FUNCTION ALONE,IS FOLLOWED BY CERTAIN DEFINITE CHANGES IN THEIR INTERNAL ARCHITECTURE, AND EQUALLY DEFINITE ALTERATION IN THEIR EXTERNAL CONFORMATION, IN ACCORDANCE WITH MATHEMATICAL LAWS.”, which simply means that bone

remodels in response to the forces applied. However, the mere reference to ‘Wolff’s law’ in relation to bone

resorption is an inadequate explanation of this complex physiologic process.

Consequences of RRR

•Apparent loss of sulcus width and depth.

•Displacement of the muscle attachment closer to the crest of the residual ridge.

•Loss of vertical dimension of occlusion.

•Reduction of lower face height.

•An anterior rotation of the mandible.

•Increase in relative prognathia.

•Changes in inter-alveolar ridge relationship.

•Morphological changes such as sharp, spiny, uneven

residual ridges.

•Resorption of the mandibular canal wall and exposure of

the mandibular nerve.

•Location of the mental foramina close to the top of the

mandibular residual ridge.

This provides serious problems to the clinician on how

to provide adequate support, stability and retention of the

denture.

Basic concept of bone:A basic concept of bone structure and its functional

elements must be clear before bone resorption can be

understood. The structural elements of bone are:

a) Osteocytes found in bone lacunae.

b) The intercellular substance or bone matrix consisting of

fibrils and calcified cementing substance.

c) Osteoblasts.

d) Osteoclasts

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(a) Osteocytes:These are small, flattened and rounded cells embedded in the bone lacunae. They are the main cells, of the developed bone and are derived from the matured osteoblasts.

Function:• Help to maintain bone as a living tissue because of

their metabolic activity. • Play an important role in maintaining the exchange

of calcium between bone and extra cellular fluid.(b) Calcified cementing substance:

Consists of mainly polymerized glycoproteins and mineral salts namely CaCo3 and phosphate which are bound to these protein substances.

(c) Osteoblasts:Concerned with bone formation and are situated on the outer surface of bone in a continuous layer.

Functions:• Responsible for synthesis of bone matrix. • Role in calcification. (d) Osteoclasts:

They are the giant multinucleated cells found in the lacunae of bone matrix.

Functions:• Responsible for bone resorption during bone

remodeling. Bone resorption always requires the simultaneous elimination of organic and inorganic components of the intercellular substance.

Mechanism of bone resorption

•The organic components of the intercellular substance are removed by proteolytic action of the osteoclasts.

•Then, the Ca salts (inorganic) are dissolved by a chelating action of the osteoclasts.

•As resorption takes place, the osteocytes released may revert to osteoblasts or become osteoclasts, depending on the physiologic and pathologic demands.

• Histologically, bone apposition and resorption take place in close approximation, making possible the bone balance of shape and size.

Pathology of RRR

Gross pathology:The basic structural change in RRR is a reduction in the size of the bony ridge under the mucoperiosteum. It is primarily a localized loss of bone structure. In some situations, this loss of bone may leave the overlying mucoperiosteum excessive and redundant. In order to provide a simplified method for categorizing the most common residual ridge configurations, a system of six orders of RR form has been described. Order 1 - Pre extractionOrder 2 - Post extractionOrder 3 - High, well-roundedOrder 4 - Knife edgeOrder 5 - Low, well-roundedOrder 6 - Depressed

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•It is clear that RRR does not stop with the residual

ridge , but may well go below where the apices of the

teeth were, sometimes leaving only a thin cortical plate

on the inferior border of the mandible or virtually no

maxillary alveolar process on the upper jaw.

•Sometimes a knife edge ridge maybe masked by a

redundant or inflamed soft tissue, which can be detected

by palpation or by Lateral cephalometric radiographs.

Microscopic pathology:

• Studies have revealed evidence of osteoclastic activity

on the external surface of the crest of the residual ridges.

The scalloped margins of Howship’s Lacunae sometimes

contain visible osteoclasts .

•Studies have shown total absence of periosteal lamellar

bone on the crest of the residual ridge, and a presence of

cortical layer consisting of an endosteal type of bone, or no cortical layer but simply a medullary type of trabecular

bone.

•Varying degrees of inflammatory cells ,including lymphocytes and plasma cells, have also been seen.

PATHOPHYSIOLOGY OF RRR

•It is a normal function of bone to undergo constant

remodeling throughout life through the process of bone

resorption and bone formation.

•Growth : ↑ Bone formation.

•Osteoporosis/localized periodontal disease: ↑ Bone

resorption.

•RRR is a localized pathologic loss of bone that is not built back by simply removing the causative factors.

•Yet, the physiologic process of internal bone remodeling goes on even in the presence of this pathologic external osteoclastic activity that is responsible for the loss of so much of bone substance.

•It has been shown that remodeling takes place in 3 dimensions such that certain portions of bone become narrower to the extent that all existing cortical bone in that area is removed by external osteoclastic activity and is replaced by a new cortical layer that is formed by simultaneous endosteal bone formation.

•Even if a great deal of RR is removed in total, there is often a cortical layer of bone over the crest of the ridge. This means that new bone has been laid down inside the RR in advance of the external osteoclastic removal of bone.

•The mechanism of the reduction of the mandibular residual ridge actually represents a modified version of the Enlow’s “V” principle, showing external resorption

accompanied by endosteal deposition.

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Based on the clinical fact that :

•RRR is not inevitable

• Its rate varies

• The rate of resorption is greater that the rate of formation in some patients ,

….RRR should be considered a pathologic process.

Pathogenesis of RRR

Order I: pre-extraction: The tooth is in its socket with thin labial and lingual cortical plates merged with the lamina

dura.

Order II: postextraction: The healing period includes clot formation and organisation, filling of the socket with the

trabecular bone and epithelisation over the socket site. The edges of the residual ridge are still sharp.

Order III: High , well rounded residual ridge: The cortical

plates are rounded off by external osteoclastic resorption, narrowing of the crest of the ridge begins and remodelling

of the internal trabecular structure takes place.

Order IV: Knife edge RR : Sharp narrowing of the labio-

lingual diameter of the crest of the ridge with a

compensatory internal remodelling leading to a sharp

crest of the ridge.

Order V: Low well rounded RR : Progressive labio lingual

narrowing of knife edge ridge leads to a widely rounded

and lower residual ridge.

Order VI: Depressed RR: Eventually further progression of

the resorption leads to a flat, depressed ridge.

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•RRR is chronic, progressive, irreversible and cumulative. Usually, RRR proceeds slowly over a long period of time flowing from one stage imperceptibly to the next. Autonomous regrowth has not been reported. Annual increaments of bone loss have a cumulative effect leaving less and less residual ridge.

Changes In The

Maxilla And The

Mandible

•Maxillary teeth are generally directed downward and outward, so bone reduction generally is upward

and inward. Since the outer cortical plate is thinner

than the inner cortical plate, resorption from the outer cortex tends to be greater and more rapid. As

the maxilla becomes smaller in all dimensions, the denture bearing area (basal seat) decreases. •The bone of the maxillae resorbs primarily from the occlusal surface and from the buccal and labial surfaces.•Thus the maxillary residual ridge looses height and maxillary arch becomes narrower from side to side and shorter anteroposteriorly.

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•The anterior Mandibular teeth generally incline upward and forward to the occlusal plane, whereas the posterior teeth are either vertical or incline slightly lingually. •The mandibular ridge resorbs primarily from the occlusal surface.•Because the mandible is wider at its inferior border

than at the residual alveolar ridge in the posterior part of the mouth, resorption, in effect, moves the left and

right ridges progressively farther apart.

•The mandibular arch appears to become wider, while the maxillary arch becomes narrower.•Thus, RRR is centripetal in maxilla and centrifugal in mandible.•The cross section shrinkage in the molar region, is downward and outward. In the anterior region it is first downward and backward ,and then moves forward.•The surface of the arches maybe resorbed out of parallelism which can result in diminished stability of dentures.•Severe ridge resorption can also result in increased inter arch space.

Epidemiology of RRR:•To date, it would appear that RRR is world-wide, occurs in males and females, young and old, sickness

and in health, with and without dentures and is unrelated to the primary reason for the extraction of

the teeth (Caries / periodontal disease). •Rate of RRR is variable

-between persons.-within the same person at diff. times.

-within the same person at diff. sites.

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Etiology of RRR

It is postulated that RRR is a multifactorial,

biomechanical disease that results from a

combination of:

• Anatomic.

• Metabolic.

• Functional.

• Prosthetic factors.

ANATOMIC FACTORS:It is postulated that RRR varies with the quantity

and quality of the bone of the residual ridges: RRR α anatomic factors

The amount of bone:• It is not a good prognostic factor for the rate of RRR, because it has been seen that some large ridges resorb rapidly and some knife edge ridges may remain with little changes for long periods of time. •Although the broad ridge may have a greater potential for bone loss, the rate of vertical bone loss may actually be slower than that of a small ridge because there is more bone to be resorbed per unit of time and because the rate of resorption also depends on the density of bone.

Quality of bone:On theoretic grounds, the denser the bone, the

slower the rate of resorption because there is more bone to be resorbed per unit of time.

METABOLIC FACTORS.Generally, body metabolism is the net sum of all the building up (anabolism) and the tearing down (catabolism) going on it the body.

RRR α bone resorption factorsbone formation factors

•In equilibrium the two antagonistic actions (of osteoblasts and osteoclasts) are in balance. In growth, although resorption is constantly taking place in the remodeling of bones as they grow, increased osteoblastic activity more than makes up for the bone destruction.

•Whereas in osteoporosis, osteoblasts are hypoactive, and, in the resorption related to hyperparathyroidism, increased osteoblastic activity is unable to keep up with the increased osteoclastic activity. The normal equilibrium may be upset and pathologic bone loss may occur if either bone resorption is increased or bone formation is decreased, or if both occur.

•Since bone metabolism is dependent on cell metabolism, anything that influences cell metabolism of osteoblasts and osteoclasts is important.

•The thyroid hormone affects the rate of metabolism of cells in general and hence the activity of both, the osteoblasts and osteoclasts. •Parathyroid hormone influences the excretion of phosphorous in the kidney and also directly influences osteoclasts.

•The degree of absorption of Ca, P and proteins determines the amount of building blocks available for the growth and maintenance of bone. •Vit C aids in bone matrix formation.

•Vit D acts through its influence on the rate of absorption of calcium in the intestines and on the citric acid content of bone.•Various members of Vit B complex are necessary for bone cell metabolism.

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•According to Reifenstein, in the young person, there is a relative predominance of anabolic hormones (estrogen and testosterone) over the anti anabolic hormones( cortisone and hydrocortisone) resulting in continued growth of skeleton.

•He further states that, as people get older, the anabolic hormones are so reduced that the antianabolic hormones are in relative excess with the result that bone resorption may take place faster than bone formation and that bone mass may be reduced.

FUNCTIONAL FACTORS

•Forces within the physiological limits are beneficial

in their massaging effect. On the other hand,

increased or sustained pressure produces bone

resorption.

•Bone that is used as by regular physical activity

will tend to strengthen within certain limits , while

bone that is in disuse will tend to atrophy.

Disuse atrophy

•It is directly proportional to the extent of disuse.

•It does not result from the direct loss of non

functional bone, but the lack of replacement of bone not needed for function.

•After the loss of natural teeth, bone cannot be stimulated by a denture base as the teeth did

internally. The lack of internal stimuli contributes to

the disuse atrophy.

•The amount and frequency of stress and its

distribution and duration are important factors.

•The reaction of bone to pressure can cause both

apposition and resorption.

•Whenever pressure interferes with the blood or nerve

supply of the bone, resorption occurs.

•The interference maybe due to pressure directly from

the bone or inflammatory in origin.

PROSTHETIC FACTORS➢Excessive stress resulting from artificial

environment: • Human tissues have not evolved in nature to

accept ranges of artificial things and the denture acts as an artificial entity.

➢Abuse of tissues from lack of rest:• Abused tissues are always manifested with a

slung, glistering surface. Bone is moldable. It can tolerate masticatory forces within the limits of physiologic tolerance but exceeding that it causes damaging forces which will result in resorption of the alveolar bone and alteration in tissue form .

➢Long continued use of ill fitting dentures: • In ill fitting dentures, there is an improper relation of

the denture base to the supporting tissue. Ill fitting dentures may be due to :

• Long use• Loss of bone• Incorrect occlusion• Incorrect jaw relation

➢UNDER EXTENDED DENTURES:• Lead to less retentive dentures and increase load

per unit area. Common sites are:• Lingual flange• Buccal shelf area• Retromylohyoid area• Retromolar pad

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➢Faulty improper procedures employing compression forces:

• Before impression procedures, care has to be taken on selection of trays. If the tray selected is too large, it will distort the tissues around the borders of the impression, away from the tissues. If it is too small, the border tissues will collapse inward onto the residual ridge. This will reduce the support of the lips by the denture flange.

• The use of minimal and selective pressure impression techniques should be implicated in order to avoid distortion of the mucosa and ridge area which may be under considerable pressure otherwise.

➢Error in relating maxilla to the cranial landmarks (orientation relation):

The plane of the maxilla should be oriented to the facial

reference line (Camper’s plane or ala tragus line). If not,

may cause instability of denture leading to resorption.

➢Lack of freeway space due to increased vertical dimension of occlusion:

Freeway space is present in the teeth in the physiologic rest position. It is normally 2-8mm but in complete

dentures it is around 2mm. At times, due to lack of

freeway space the bone resorbs because of increased vertical height in an attempt to create the space.

➢ Incorrect Centric relation record:

If the Centric relation is not recorded properly, the

mandibular teeth will not occlude properly with those on

the maxillary arch. This proper occlusion is essential to

the health of bony support. Otherwise, during eccentric

movement, it causes pressure on bone due to failure of

denture stability. Hence resorption of base occurs.

➢Faults in selection and placement of posterior teeth:The selection of proper tooth size is based on :

•Capacity of ridges to receive and resist the

forces of mastication. •Space available for the teeth.

•When the ridge is weak, resorbed and covered by only lining mucosa, then the use of the

posterior teeth should be smaller. This will limit the occlusal surface, which in turn will minimize

the forces directed to such a ridge.

➢ If occlusal corrections are not done:• These errors which may be caused due to processing

techniques if not corrected causes premature contacts resulting in increased stress.

• Selective grinding should be done to minimize lateral stress and resulting tissue trauma.

➢Overclosure• The loss of proper vertical dimension after the insertion

of complete dentures results in the triggering of a cyclic series of events detrimental to the health of the residual alveolar ridge.

• Overclosure causes the mandible to be moved or rotated in an upward and forward direction causing occlusal disharmony and excessive trauma to anterior region .

Bone resorption and Ca homeostasis:The only sources of Ca for the body are

•Diet •Bone reservoir.

Ca homeostasis is maintained by controlling Ca obtained from these 2 sources. This can occur by altering internal absorption mechanisms (income) or tubular reabsorption (recycling) or by liberation of Ca from the skeleton via resorption (savings). There is a reciprocal relationship between Ca concentration and bone resorption to maintain Ca homeostasis. As the level of serum calcium develops, resorption is stimulated and factors that would inhibit resorption are depressed.

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•Skeletal depletion of calcium occurs as a result of stimulation of parathyroid gland and the alveolar bone is the first to be affected. This is due to the function of parathyroid hormone in maintaining the blood calcium level by mobilizing it from bones by osteoclastic activity.

•Simultaneously , there is an increased renal excretion of phosphate, which disturbs the blood calcium:phosphorous ratio by raising the blood calcium level. This results in mobilization of phosphates from bones by osteoclastic activity.

•Under these conditions , alveolar bone becomes susceptible to diseases like osteoporosis.

Osteoporosis and RRR

•Osteoporosis is characterized by low bone mass and micro architectural deterioration of the bone, which leads to increased bone fragility and risk of fracture.

•It has two forms.

•The more prevalent Type I (post menopausal) affects women for a decade or so after menopause.

•The Type II ( senile or idiopathic) attacks males and females at any age for no obvious reason.

•RRR maybe a manifestation of Type I osteoporosis .

•Both cortical and trabecular bone are affected.

Treatment for osteoporosis•Estrogen replacement therapy

•Ca supplement

•Good nutrition and regular exercise•New drugs for systemic osteoporosis are

under evaluation, including biophosphonates to inhibit osteoclasts and injections and

calcitonin to reduce resorption.

Detection of bone loss i.e. radiographs

•Digital subtraction radiography •Dual energy x-ray absorptiometry

Methods of evaluation of bone loss in RRR

• Radiographs:

- Cephalometrics .

- Panoramic.

• Tetracycline labeling

• Mercury porosimetry

• Anatomic studies

• Remount jig procedure

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Management of RRR

➢Systemic evaluation

➢Diet

➢Tissue treatment therapy

➢Pre prosthetic surgery

➢Prosthetic management:

-Impression techniques.

-Denture base selection.

-Teeth selection and arrangement.

-Implant supported prosthesis.

Systemic evaluation

•Any systemic condition that can contribute to the degeneration of the bone condition should be

corrected and stabilized, for e.g.: osteoporosis, hyperparathyroidism, diabetes mellitus.

•Any dental treatment should follow only after the condition is under control and the patient is fit for

treatment.

•In cases where limited help can be given, the patient should be counseled about its effect on dental health.

Diet.•Patients with bone disease need a diet high in proteins, vitamins and mineral content.•Should reduce or stop intake of refined carbohydrates, white flour, and white sugar.•In all dietary prescriptions , the consistency of food prescribed must take into account the patients ability to masticate.

Tissue Treatment Therapy.•Soft conditioning materials can be used to rejuvenate the tissue-bearing area.•Hypertrophied tissues, previously treated by surgery, can be reconditioned by using this material.

Pre-prosthetic surgery

▪It aims at providing a good healthy surface for the insertion of the dentures.

▪It includes all the surgical procedures by virtue of which an ideal smooth, healthy U shaped ridge , without any unfavourable undercuts or bony growths and with sufficient vestibular depth is achieved.

▪It includes the following surgical procedures:

•Ridge correction.

•Ridge extension/vestibuloplasty.

•Ridge augmentation

•Surgical correction of maxillomandibular relation.

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Ridge Corrective surgery

Soft tissue deformities

•Labial frenectomy.

•Lingual frenectomy.

•High buccal frenal attachments.

•Hyperplasia of soft tissues.

Bony deformities

•Sharp irregular ridge.

•Alveoloplasty.

•Alveolectomy.

•Excision of tori and genial tubercles.

Ridge extension surgery/vestibuloplasty

•Labial.

•Lingual.

•High mental foramen.

•Zygomaticoplasty.

•Tuberoplasty.

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Ridge augmentation

It is aimed at :

•Increase in the ridge height and width providing a large denture bearing area ,

•Protection of neuro vascular bundles

•Restoration of proper maxillomandibular arch relationship.

Ridge augmentation has been tried with:

•Bone transplants

•Autogenous and homogenous cartilage

•Hydroxylapatite

•Acrylic implants.

Prosthetic management.

Impression technique

In patients with severely resorbed ridges, lack of ideal amount of supporting structures decreases support and the encroachment of the surrounding mobile tissues onto the denture border reduces both stability and retention. Thus the main aim of the impression procedure is to gain maximum area of coverage. For e.g., in mandibular ridge, obtaining a fairly long retromylohyoid flange helps to achieve a better border seal and retention.

Selection of proper trays and the correct impression procedure is very essential for an accurate impression.

• Selective pressure techniqueThis technique is most widely advocated to manage RRR.It makes it possible to confine the forces acting on the

denture to the stress bearing areas .This helps in better withstanding the mechanical forces

induced by denture wearing.• Winkler describes a technique which uses tissue

conditioners. An over extended primary impression of alginate is made. Occlusal wax rims are constructed and the borders are adjusted so that the lingual flange and sublingual crescent area are in harmony with the resting and acting phases of the floor of the mouth by an open and closed – mouth technique.

3 applications of conditioning material are used – each application approximately 3-10 minutes. The third and final wash is made with a light bodied material. This technique results in the impression that has tissue placing effect with relatively thick, buccal, lingual and sublingual crescent area borders.

•Miller used mouth-temperature waxes instead of tissue conditioners .

Mucodynamic technique.

It is intended to integrate the changes in the shape of the vestibules when functional movements are made. A highly viscous thermoplastic reversible impression material is placed in the custom tray, then carefully adapted to the residual ridge and held with light and uniform pressure while the functional movements are made. As soon as the entire surface is smooth and the buccal and lingual borders are molded to the outer circumference without any folds, the impression is complete.

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Selection of denture base

For degenerative ridge patients there are three types of denture bases:

•Methyl methacrylate resin denture bases

•Cast metal bases

•Processed resilient , lined denture bases

Methyl methacrylate resin denture bases

•These are the standard bases normally used.

•These bases are quickly and easily processed.

•Dimensionally stable.

•But in a short time the base appears to soften and change color, and is not strong.

Cast metal bases.

•Main advantage is the great accuracy of fit to the tissues by surface tension, than acrylic denture bases.

•They maybe of gold, chromium cobalt or aluminium.

Processed resilient , lined denture bases.

Its greatest advantage is its cushioning effect on the mucosa and its ability to distort and spring back.

Indications:

•Patients with severely undercut ridges, but for whom surgery is contraindicated.

•Patients with parafunctional mandibular movement habits.

•Patients with flat ridge and delicate tissues.

Limitations:

•They can be used only under a hard-processed acrylic resin base, and the lining works best when there is a 2 mm thickness.

•Deterioration of the liner in some mouths.

In spite of this , it can be held up well in dentures by proper cleansing and brushing with soft tooth brush.

Teeth selection and arrangement

Teeth can be selected acc. to their form and size:

•Anatomic or cuspal teeth

•Semi anatomic teeth

•Non anatomic or zero degree teeth.

The following requirements have to be met during teeth arrangement:

•Stability of occlusion in centric relation.

•Balanced occlusion for eccentric contacts.

•Unlocking of the cusps mesio distally to accommodate the settling of denture bases.

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•Control of horizontal force by buccolingual cusp height reduction acc. to residual ridge shape and inter arch space.

•Functional balance by favorable tooth to ridge crest position.

•Cutting and shearing efficiency.

•Anterior clearance of teeth during mastication.

•Minimal occlusal stop areas for reduced pressure during function.

•Teeth should be placed in neutral zone to create co ordination between the primary and secondary masticatory organs.

•Relative to each other, the maxillary and mandibular

residual ridges are known to be in a favorable position

for normal arrangement of posterior teeth if the

connecting line between the midridge line of the max.

and mand. residual ridges are at an angle of more than

80 degrees.

•An angle less than 80 degrees necessitates a cross bite or

reverse occlusion arrangement of posterior teeth.

•A prognathic mandible necessitates the arrangement of

anterior teeth in a reverse occlusion.

•Non anatomic teeth have known to cause fewer

denture sore spots and lesser ridge resorption.

•Semi anatomic reverse curve posterior teeth favor

the lower ridge

•Anatomic posterior teeth cause more denture

soreness and ridge resorption.

•Few studies state that anatomic posterior occlusion

favors lower dentures and non anatomic posterior

teeth favor upper denture.

Implant supported prosthesis.The various problems associated with RRR and stability of removable soft tissue borne dentures have aroused

interest in dental implantology to provide stable mechanical support to the dental prosthesis. This is

because of the following advantages offered by implant supported prosthesis:

•Maintenance of alveolar bone•Maintenance of occlusal vertical dimension.

•Height of alveolar bone is found to be maintained as

long as the implant remains healthy.•Improved psychological health.

•Regained proprioception.•Increased stability, retention and phonetics.

•Maintenance of structure and function of muscles of

mastication and facial expression.•Immune to caries.

•Increased trabeculation and density of bone.•Overall volume of bone is maintained.

•Efficiency to take up stress and strain.•There is 20 fold decrease in the loss of structure with

implants when compared with resorption that occurs with

removable prosthesis.•Preventive implant is given following extraction to retard

ridge resorption.

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Prosthodontic classification of implants.

FP-1 : Fixed prosthesis replacing only crown.

FP-2 : Fixed prosthesis replacing crown and portion of root.

FP-3 : Fixed prosthesis replacing missing crowns and portion of the edentulous site.

RP-4 : Removable prosthesis : overdenture supported by implants.

RP-5 : Removable prosthesis : overdenture supported by both soft tissue and implant.

•The success of implant supported prosthesis,

however, depends on the technical

knowledge and mastery of the

implantologist, and is directly related to the

selection of patient and implant, surgical

technique, follow up procedures and patient

acceptability.

Summary

•Residual ridge resorption is a chronic, progressive, irreversible, and disabling disease , of multifactorial origin.

•Much is known about its pathology and pathophysiology, but a lot remains to know about its pathogenesis, epidemiology and etiology.

•RRR requires a multiple approach for diagnosis and treatment planning.

•The cause must be detected, by the aid of a physician, and then eliminated or stabilized before dentures are constructed.

•Construction of a stable functioning denture and a regular follow up treatment can help in the restoration of function, and thus, the restoration of the physical and mental vitality of the patient.

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Conclusion

•The preservation of supporting tissues is a sacred trust

that cannot be ignored.

•The application of the basic concepts and the advances

made in the basic sciences will help to keep this trust in the hands of the dental profession.

•As prosthodontists, we need to perform the most meticulous and intelligent prosthodontic care of the

patient within our capabilities.

•…and then , it would not seem a nebulous hope that

some day there will be control over residual ridge

resorption.

References

•Ortman HR: Factors of bone resorption of the residual ridge. J Prosthet Dent 1962;12,3:429-440.

•Atwood DA: Reduction of residual ridges: A major oral disease entity. J Prosthet Dent 1971;26:266-279.

•Atwood DA: Some clinical factors related to rate of resorption of residual ridges. J Prosthet Dent 2001;86:119-125.

•Wendt DC: The degenerative denture ridge – Care and treatment. J Prosthet Dent 1974;32,5:477-492.

•Ortman HR : The role of occlusion in preservation and prevention in complete denture prosthodontics. J Prosthet Dent 1971;25,2:121-138.

•Sobolik FC : Alveolar bone resorption. J Prosthet Dent 1960;10,4:612-619.

•Jahangiri L, Devlin H, Ting K et al :Current perspectives in residual ridge remodelling and its clinical implications: A review. J Prosthet Dent 1998;80;224-237.

•Atwood DA : Post extraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms. J Prosthet Dent 1963;13:810-824.

•Winkler S : Essentials of complete denture prosthodontics. 2nd edition,2000.•Boucher CO : Prosthodontic treatment for edentulous patients. 12th edition,2004.•Alfred H G :Color Atlas of Dental Medicine – Complete Denture and Overdenture Prosthetics.2nd edition,1993.•Misch CE : Contemporary implant dentistry. 2nd

edition,1999.•Eroshenko VP : di Fiore’s Atlas of histology. 7th

edition.1993.

Thank you

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DEPARTMENT OF PROSTHODONTICS

Presented By:

DR. SUDHIR

MEENA

TMJ ANATOMY AND ITS APPLIED ASPECTS

TEMPOROMANDIBULAR JOINTTemporomandibular joint is the articulation between the squamous part of

temporal bone and the head of the condyle of mandible.TMJ is enclosed in a fibrous capsule that defines the anatomic and functional

boundaries of the joint.

◼ It is also called as

Gingilimo Diarthrodial

joint.

◼ It is called so because :

Gingylimo : hinge

Arthrodial : gliding

Development

◼ The synovial joint is formed by three

mesencymal layers.

◼ The two outer layers are continuous with the

perichondrium covering the cartilaginous ends

of the articulating bones .

◼ The middle layer becomes loose and forms the

synovial cavity.

Development

◼ The capsule and ligaments are formed from the

surrounding mesenchyme cells.

◼ The articulating bones i.e. the temporal and

mandible are formed separately .

◼ Mandible is formed by the Meckel’s cartilage.

◼ Temporal bone is formed by ossification of the

cartilage of Otic capsule.

Anatomical Components Of TMJ

◼ Condyle: This is the “ball” in the joint.

◼ It is a part of the mandible (lower jaw) to which all the muscles are attached and

◼ Is the movable part of the articulating joint.

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Anatomical Components Of TMJ

Mandibular Condyle◼ Medial and lateral

projections called poles◼ Medial pole more prominent◼ 15-20mm mediolaterally◼ 8-10mm anterioposteriorly

Anterior view of mandibular condyle Okeson Fig. 1-8

Anatomical Components Of TMJ

Mandibular Condyle◼ Articulating surface

◼ Superior◼ Anterior◼ Posterior

Anterior view of condyle showing articulating surface Okeson Fig. 1-10a

Anatomical Components Of TMJ

Mandibular Condyle◼ Articulating surface

◼ Superior◼ Anterior◼ Posterior

◼ Slight convexity mediolaterally◼ Significant convexity

anteroposteriorly

Posterior view of condyle showing articulating surface Okeson Fig. 1-10b

Anatomical Components Of TMJ

◼ The Glenoid Fossa :The fossa is the “socket”, or

depression in which the condyle sits. It is located in the temporal bone of the skull.

Anatomical Components Of TMJ

Temporal bone◼ Posterior portion of the roof of the

glenoid fossa is thin◼ Non-load bearing

◼ Articular eminence◼ Dense bone◼ Designed to handle loads

Lateral view of skeletal components of TM joint Okeson Fig. 1-11a

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3

ARTICULAR CARTILAGE

◼ Articular cartilage is the presence of soft

cartilage on the articulating surfaces i.e. head of

the condyle and glenoid fossa.

◼ On repeated mandibular movement there is

severe compression of the articulating surfaces

which can cause some pathology to them. This

cartilage provides a cushioning effect .

Anatomical Components Of TMJ

Articular disc: is an oval fibrous plate that divides the joint into an upper and lower half.

The upper half permits gliding whereas lower part permits both gliding and rotary.

Anatomical Components Of TMJ

TM capsule and ligaments

◼ Capsular ligament

◼ TM ligament

◼ Collateral ligament

Accessory ligaments

◼ Sphenomandibular ligament

◼ Stylomandibular ligament

Lateral view of TM jointAsh Occlusion Fig. 1-5

Anatomical Components Of TMJ

◼ Articular capsule : the TMJ is enclosed in a

fibrous capsule that defines the anatomic and

functional boundaries of the TMJ. It consists

of two layers:

1. Outer layer

2. Inner layer

ARTICULAR CAPSULE

◼ The inner layer is the synovial layer which serves three functions:

1. Reduce friction between articulating surfaces.

2. Provide nutrition to non vascularized tissue.

3. Secretes synovial fluid containing hyaluronic

acid (slippery).

Anatomical Components Of TMJ

TM ligament◼ Two portions

◼ Outer oblique◼ Inner horizontal

◼ Responsible for second arc of opening after 20-25 mm of hinge axis rotation

◼ Gliding movement involving upper compartment

◼ Fully extended ligaments cause condyle to move anteriorly and inferiorly toward eminence. Lateral view of TM joint

Ash Occlusion Fig. 1-20

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4

Anatomical Components Of TMJ

Collateral ligament◼ Attaches the disc to the medial and

lateral poles of the condyle◼ Medial discal ligament◼ Lateral discal ligament

◼ Divide joint in to upper and lower compartments.

◼ Collagenous connective tissues.◼ Don’t stretch.

◼ Acts as a restrictive barrier for disc movement away from condyle.

Frontal view of TM cross section through head of condyle Okeson Fig. 1-17

Anatomical Components Of TMJ

Sphenomandibular ligament

◼ Spine of sphenoid bone to the lingula of the mandible.

◼ This is a accessory ligament and has minimal effect on limiting mandibular movement.

Accessory ligaments Okeson Fig. 1-21

Anatomical Components Of TMJ

Stylomandibular ligament

◼ Styloid process to angle of mandible

◼ Limits excessive protrusive movement

Accessory ligaments Okeson Fig. 1-21

Muscles Of Mastication

Temporalis muscle

◼ Origin lateral surface of skull

◼ Insertion coronoid process and ramus of the mandible.

◼ Elevates and retracts jaws and assists in rotation.

Masseter Muscle

◼ Origin from zygomatic arch.

◼ Insertion at angle of the mandible.

◼ Elevates and protracts the jaws and assists in lateral movement.

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Medial Pterygoid Muscle

◼ Origin from pterygoid fossa and medial surface of lateral pterygoid plate.

◼ Insertion at medial surface of angle of mandible.

◼ Elevation , lateral movement and protrusion.

Lateral Pterygoid Muscle

•Superior part from greater wing of sphenoid .•Inferior part from inferior surface of lateral pterygoid plate.•Insertion at neck of the mandible.•Protrusion , depression and lateral movement.

Examination of TMJ

◼ TMJ dysfunction can be checked by two ways:

1. Joint sounds.

2. Joint restrictions.

Joint Sounds

◼ Joint sounds are of two types;

1. Clicking: click is a single sound of short duration.

2. Crepitation: Crepitation refers to multiple sound while opening and closing the mouth.

Methods used for TMJ Sound/Vibration Recording

◼ Palpation

◼ Auscultation with stethoscope

◼ Electronic recording with skin contact transducers

◼ Sonography

◼ Thermography

Palpation◼ Palpation is done by placing fingertips

over the lateral surface of the joint.◼ Patient is asked to open and close the

mouth slowly and any sound discrepancy is checked.

◼ Palpation has a limited value. We can feel low frequency vibrations and the movements of joint components with our fingers but that is not hearing. Sounds cannot be palpated with fingers.

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Auscultation with Stethoscope

◼ Auscultation is hearing of TMJ sounds with the help of stethoscope.

◼ However one has to be very precise about these sounds as he will hear multiple sounds with a stethoscope.

◼ Also these investigations can not be recorded.

Electromyography

◼ Electromyography (EMG) is the study of muscle function through the inquiry of the electrical signal when the muscle emanates.

SONOGRAPHY

◼ Sonography is the technique of recording and graphically demonstrating joint sounds. They can be:

1. Audio amplifying devices

2. Ultrasound echo recordings.

This technique is known to record joint sounds accurately.

THERMOGRAPHY

◼ Thermography is a technique that records and graphically illustrates surface skin temperatures.

◼ It has been suggested that an individual should have bilaterally symmetrical thermo grams.

◼ Any deviation is suggestive of a temporomandibular disorder.

Bruxism is the most common reason for

pain in TMJBRUXISM

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Signs of bruxism

◼ Masseter hypertrophy

◼ Non-functional wear

facets

Types Of Occlusal Appliances

◼ The two most commonly used are:

1. The stabilization appliance

2. The anterior positioning appliance

INDICATIONS

◼ Stabilization appliance are generally used to treat

muscle pain disorders.

◼ Anterior positioning appliance are used for

treatment of disc derangement disorders.

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Management of Traumatic Dislocation of the Mandibular Condyle into the Middle Cranial Fossa

Robert P. Barron, • Vesa T. Kainulainen, • Albert W. Gusenbauer,• Richard Hollenberg,• George K.B. Sàndor,

J Can Dent Assoc 2002; 68(11):676–80

TMJ trauma

Condylardislocationinto middlecranial fossa

Signs and symptoms

Shortening of height of mandibular ramus.

Open bite or crossbite.

Inability to performlateral excursions.

Deviated mandibular midline

Diagnostic aids

Panoramic radiograph,

mandibular series: PA,lateral cephalogram,

CT scan

ENT and neurologic signs

CSF otorrhea

Lacerations of external auditory canalParalysis of facial nerve

Hearing deficit

Hemorrhage from middle meningeal arteryDural tears

Subdural and epidural hematoma

Altered level of consciousness

Pupillary dilatation

Nausea

Deviation of mandible toopposing side

Pre-auricular hollow or depression

Pain on mandibular movementand on pre-auricular palpation

Shortening of height ofmandibular ramus

Premature occlusion with open bite

Chin abrasion or laceration with or without symphysis fracture

TMJ trauma Signs & Symptoms Diagnostic aids ENT and neurological signs

Panaromic radiograph,

CT scan

Laceration of External Auditory Canal

Condylar fracture The glenoid fossa itself may need to be reconstructed.

Sources of autogenous bone such as cranial and rib grafts have typically been used, in addition to allogeneic bone.

The type of reconstruction chosen is based upon the size of the defect and the amount of condylar displacement.

The goals of glenoid fossa reconstruction are to prevent recurrent condylar dislocation, to re-establish posterior facial height, and to restore normal joint function by repairing the damaged articular disk, if it issalvageable

Treatment for condylar dislocation: manual reduction, maxillomandibular fixation

SUBLUXATION

۞ It is a clinical description of condyle as it moves anterior to the crest of the articular eminence.

۞ It is not a pathologic condition but reflects a variation in anatomic form of the fossa.

CAUSE

❑ Patient who have a steep short posterior slope of the articular eminence followed by longer flat anterior slope seem to display a greater tendency towards subluxation.

❑ Patient reports a locking sensation whenever the mouth is opened too widely.

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➢ During the final stage of maximal opening, the condyle shows a quick sudden jump forward, leaving a clinically noticeable preauricular depression.

➢ Patient education.➢ Patient must learn to restrict opening so as not to

reach the point of translation that initiates the interferences.

CLINICAL CHARACTERISTICS

TREATMENT

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OSTEOARTHROSIS

❑ As remodeling occurs the condition can become stable, yet the bony morphology remains altered.

❑ Osteoarthrosis is a natures way to adapt to the functional demands of the system.

❑ Because osteoarthrosis represents a stable adaptive phase, the patient does not report symptoms.

❑ It is confirmed when structural changes in the subarticular bone are seen on radiographs.

❑ As osteoarthrosis represent an adaptive process, no therapy is indicated for the condition.

RHEUMATOID ARTHRITIS

❑ Rheumatoid arthritis is a chronic systemic disorder of unknown cause.

❑ This condition produces a persistent inflamatory synovitis that leads to the destruction of articular surfaces and subarticular bone.

❑ Supportive therapy for rheumatoid arthritis is directed towards pain reduction.

THANK YOU

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TEMPEROMANDIBULAR JOINT

PRESENTED BY

DR. SUDHIR MEENA

CONTENTS :⚫ INTRODUCTION

⚫ ANATOMY OF TMJ AND ASSOCIATED STRUCTURES

⚫ NEUROPHYSIOLOGY OF MANDIBULAR MOVEMENTS

⚫ CLASSIFICATION OF MANDIBULAR MOVEMENTS

⚫ CONTROLLING FACTORS OF MANDIBULAR MOVEMENTS

⚫ PROSTHODONTIC CONSIDERATION OF MANDIBULAR MOVEMENTS

⚫ CONCLUSION

⚫ REFERENCES

INTRODUCTION

⚫ Masticatory system is extremely complex .

⚫ It is primarily made up of bones, muscles,ligaments and teeth .

⚫ Movement is regulated by intricate neurologic controlling mechanism that occurred during mastication ,swallowing speech respiration and facial expression

⚫ A knowledge of mandibular movements is essential for dentist to understand :

⚫ various aspects of occlusion

⚫ to arrange artificial teeth

⚫ select and adjust recording devices and articulators

⚫ Each movement is coordinated to maximize the function while minimizing damage to any structure.

⚫ To study mandibular movements one should have knowledge about anatomy of TMJ ,function and neurophysiology of masticatory system and mechanics of mandibular movements hence mandibular movements are described under three sections

⚫ TMJ⚫ Neuroanatomy and physiology of masticatory

system⚫ Mechanics of mandibular movements

DEVELOPMENT OF TMJ

⚫ It develops between the mandibular condyle and the temporal bone of the skull.

⚫ These developing bones are initially separated by a mesenchylmal filled space .

⚫ The condylar secondary cartilage appears between the 10 and 12 week and grows towards temporal bone.

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⚫ The intervening mesenchme differentiates to form fibrous connective tissue in which parallel horizontal clefts appear adjacent to the bone ,thereby giving rise to the central articular disc between the upper and lower joint cavities.

Temporomandibular Joint

⚫ The area where the craniomandibular articulation occures is called the temporomandibular joint

⚫ Bilateral diarthrodial joint

⚫ Atypical synovial joint

⚫ Ginglymoarthrodial joint

⚫ Compound joint

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⚫ Definition the articulation of condyloid process of the mandible and the inner articular disc with the mandibular fossa of squamous part of the temporal bone.

⚫ TMJ IS MADE UP OF⚫ Condyloid process⚫ Squamous portion of temporal bone ⚫ Fibrous inter articular disc⚫ Ligaments⚫ Muscles

Condyloid process

⚫ It is the portion of the mandible that articulates with the cranium around which movement occurs

⚫ Anterior view it has a medial and lateral projection s which are called as poles

⚫ Mediolateral length of the condyle is 15 to 20 mm and anteroposterior length is 8 to 10mm.

⚫ The articulating surface of the condyle extends both anteriorly and posteriorly to the most superior aspect of the condyle.The posterior articulating surface is greater than anterior surface.

⚫ The articulating surface of condyle is quite anteroposteriorly and only slightly convex mediolaterally.

⚫ A shallow concavity, the pterygoid fovea is located on the anteromedial aspect of the mandibular neck where inferior head and most fibres of the superior head and lateral pterygoid muscle insert on the mandible.

Squamous part of the Temporal bone

⚫ The mandibular condyle articulates at the base of the cranium with the squamous portion of the temporal bone.This portion of the temporal bone is made of concave mandibular fossa in which the condyle is situated and which has been called as mandibular or articular or glenoid fossa

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⚫ Posterior to the mandibular fossa is the squamotympanic fissure which extends mediolaterally .

⚫ Anterior to the mandibular fossa is a convex bony prominence called the articular eminence.

⚫ The degree of the convexity of the articular eminence is highly variable but important since the steepness of this surface dictates the pathway of the condyle when it is positioned anteriorly

⚫ Medial part of the fossa is reinforced with a thick bone which acts as a stop for the upward force the Elevator muscle and inward pull by the medial pterygoid muscle.

⚫ The posterior roof of the mandibular fossa is quite thin indicating that this area of the temporal bone is not designed to sustain heavy forces.

⚫ The articular eminence however consist of thick dense bone and is more likely to tolerate such forces

ARTICULAR DISC⚫ It is composed of dense fibrous connective

tissue devoid of blood vessels and nerves.

⚫ Sagital plane it is divided into three regions according to the thickness.

⚫ Central area is thinnest and it is called intermediate zone

⚫ Anterior is thick

⚫ Posterior is thick

⚫ In the normal joint articular surface of the condyle located on the intermediate zone of the disc bordered by the thicker anterior and posterior regions .

⚫ From anterior view disc is generally thicker medially than laterally which corresponds to the intermediate space between the condyle and the medial portion of the joint.

⚫ The precise shape of the disc is determined by the morphology of the condyle and the mandibular fossa

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⚫ The articular disc is attached posteriorly to the region of loose connective tissue that is highly vascularized and innervated which is called as retrodiscal tissue or posterior attachments.

⚫ The articular disc is attached to the capsular ligament not only anteriorly and posteriorly and also medially and laterally this divides the joint into two distinct cavities.

⚫ The upper or the superior cavity is bordered by the mandibular fossa and the superior surface of the disc.

⚫ The lower or the inferior cavity is bordered by the mandibular condyle and the inferior surface of the disc.

⚫ The internal surfaces of the cavities are surrounded by endothelial cells that form the synovial lining .

⚫ This lining along with the specialized fringe located art the anterior border of the retrodiscal tissues produces a synovial fluid which fills the joint cavities thus it is turned as a synovial joint.

⚫ Synovial fluid serves two purposes

⚫ Since articular surfaces of joint are nonvascular, the synovial fluid acts as a medium for providing metabolic nutrients to these tissues

⚫ The synovial fluid also serves as a lubricant between articular surfaces during function

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HISTOLOGY OF ARTICULAR SURFACES

⚫ The Articular surface of the condyle and mandibular fossa are composed of four distinct layers

⚫ Articular zone

⚫ Proliferative zones

⚫ Fibrocartilaginous zone

⚫ Calcified zone

Blood supply to temporomandibular joint

⚫ TMJ is richly variety of vessels that surround it

⚫ Superficial temporal artery from the posterior

⚫ Middle meningeal artery from the anterior ⚫ Internal maxillary artery from the inferior ⚫ Deep auricular ,anterior and ascending

pharyngeal arteries

⚫ The condyle receives its vascular supply through bits marrow spaces by the way of inferior alveolar artery and also receives vascular supply by way of feeder vessels that enter directly into condylar head(both anteriorly and posteriorly ) from larger vessels

Nerve supply⚫ As with all joints TMJ is innervated by same nerve that

provides motor or sensory innervation to muscles that control it (Hiltons law) that is trigeminal nerve

⚫ Branches of mandibular nerve provide afferent innervation

⚫ Most innervation is provided by the auriculotemporal nerve as it leaves the mandibular nerve behind the joint and ascends laterally and superiorly to wrap around the posterior region of joint

⚫ Additional innervation is provided by deep temporal and masseteric nerves

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Ligaments

⚫ As with any joint system, ligaments play an important role in protecting the structures

⚫ The ligaments of joints are made up of collagenous connective tissues which do not stretch.

⚫ They do not enter actively into joint function but instead act as a passive restraining devices to limit and restrict border movements

⚫ 3 functional ligaments that support the TMJ

⚫ Collateral ligaments

⚫ Capsular ligaments

⚫ Temporomandibular ligament

⚫ 3accessory ligaments

⚫ Sphenomandibular ligament

⚫ Stylomandibular ligament

⚫ Retinacular ligament

Collateral ligaments

⚫ Also called as discal ligaments

⚫ They attach the medial and lateral borders of the articular disc to the poles of the condyle

⚫ Medial discal ligament –attaches the medial edge of the disc to the medial pole of the condyle

⚫ Lateral discal ligament-attaches the lateral edge of the disc to the lateral pole of the condyle

⚫ These ligaments are responsible for dividing joint mediolaterally into superior and inferior joint cavities

⚫ The discal ligaments are true ligaments, composed of collagenous c.t fibers –they do not stretch

⚫ Restrict the movement of disc away from the condyle that means they allow the disc to move passively with condyle as it glides anteriorly and posteriorly

⚫ The attachment of discal ligaments permit the disc to be rotated anteriorly and posteriorly on the articular surface of the condyle thus the these ligaments are responsible for the hinging movements of the TMJ.

⚫ The discal ligaments have a vascular supply and are innervated

⚫ This innervation provides information

⚫ regarding joint position and movement

⚫ Strain on these ligaments produce pain

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Capsular ligament

⚫ Entire TMJ is surrounded and encompassed by the capsular ligament

⚫ The fibers of capsular ligament are attached superiorly to the temporal bone along the borders of articular surfaces of the mandibular fossa and articular eminence

⚫ Inferiorly attach to the neck of the condyle

⚫ Capsular ligament acts to resist any medial ,lateral or inferior forces that tend to separate or dislocate articular surfaces

⚫ A significant function of the capsular ligament is to encompass the joint ,thus retaining the synovial fluid.

⚫ The capsular ligament is well innervated and provides proprioceptive feedback regarding position and movement of the joint.

Temporomandibular ligament

⚫ The lateral aspect of the capsular ligament is reinforced by strong,tight fibers that make up lateral ligament or temporomandibular ligament.

⚫ The temporomandibular ligament is composed of 2parts

⚫ Outer oblique portion⚫ Inner horizontal portion

⚫ Outer oblique portion-extends from the outer surface of the articular tubercle and zygomatic process posteroinferiorly to the pouter surface of condylar neck.

⚫ Inner horizontal portion-extends from outer surface of the articular tubercle and zygomatic process posteriorly and horizontally to the lateral pole of the condyle and the posterior part of the articular disc.

⚫ Oblique portion of the TM ligament resist as excessive dropping of the condyle,therefore limiting the extent of mouth opening .

⚫ This portion of ligament also influences the normal opening movement of the mandible

⚫ During the initial phase on opening,the condyle can rotate around a fixed point until the TM ligament become tight as its point of insertion on the neck of the rotated posteriorly.

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⚫ When ligament is taut,the neck of condyle cannot rotate further.

⚫ If mouth were to be open wider ,the condyle would need to move downward and forward across the eminence.

⚫ This change in opening movement is brought about by tightening the tm ligament.

⚫ This unique feature of tm ligament which limits rotational opening is found only in humans

⚫ The inner horizontal portion of TM ligament limits posterior movement of the condyle and disc.

⚫ When force applied to the mandible displaces the condyle posteriorly,this portion of ligament becomes tight and prevents the condyle from moving into the posterior region of mandibular fossa by which it protects the retrodiscal tissues from trauma.

⚫ The inner horizontal portion also protects the the lateral pterygoid muscle from over lenghtening or over extension

⚫ SPHENOMANDIBULAR LIGAMENT:

⚫ It is one of the two accessory ligaments

⚫ It arises from the spine of the sphenoid bone and extends downward to a small bony prominence on the medial surface of the ramus of the mandible called as lingula

⚫ It does not have any significant limiting effects on mandibular movements

⚫ STYLOMANDIBULAR LIGAMENT:⚫ SECOND ACCESSORY LIGAMENT

⚫ It arises from the styloid process and extends downward and forward to the angle and the posterior border of the ramus of the mandible.

⚫ It becomes taut when the mandible is protruded but is most relaxed when the mandible is opened.

⚫ The stylomandibular ligament therefore limits excessive protrusive movements of the mandible

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RETINACULAR LIGAMENTS⚫ Recently it has been described in association with TM

joint.

⚫ Arises from the articular eminence, descends along the ramus of the mandible.

⚫ Insertion: fascia overlying the masseter muscle at the angle of the mandible.

⚫ As the ligament is connected to the posterolateral aspect of the retrodiscal tissues and contains an accompanying vein.

⚫ Action: It maintains blood circulation during the masticatory movements.

Neuro anatomy and physiology of masticatory

system⚫ The function of the masticatory system is complex

⚫ Discriminating contraction of the various head and neck muscles are necessary to move the mandible precisely and allow effective functioning.

⚫ A highly refined neurologic control system regulates and coordinates activities of the entire masticatory system.

⚫ Neuromuscular system is divided into two major components.

⚫ Muscles

⚫ Neurologic mechanism

Muscles

⚫ MASSETER:

⚫ Arises from the zygomatic arch

⚫ Insertion-into the lateral surface of ramus and angle of the mandible.

⚫ It is made up of two portions or heads

⚫ The superficial portion consists of fibers that run downward and slightly backward

⚫ The deep portion consists of fibers that run in predominantly vertical direction

⚫ Nerve supply-massetric nerve ,branch of trigeminal nerve.

⚫ Arterial supply-massetric artery,branch of the inter maxillary artery.

⚫ Actions-as the fibers of the masseter muscle contract,the mandible is elevated(to close the jaw)and teeth are brought into contact

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⚫ The masseter muscle is a powerful muscle that provides the force necessary to chew efficiently.

⚫ Its superficial portion may also aid in protruding the mandible.

⚫ When the mandible is protruded and biting force is applied, the fibers of the deep portion stabilise the condyle against the articular eminence

⚫ Elevation and protrusion

⚫ TEMPORAL MUSCLE:⚫ Origin-it arises from the temporal fossa

which is comprised of parts of the parietal,temporal,frontal and sphenoid bone

⚫ The anterior fibers run vertically⚫ Middle fibers run obliquely⚫ Posterior fibers horizontally⚫ Insertion-coronoid process and anterior

border of ramus of the mandible⚫ Nerve supply-temporal branches of

mandibular division of trigeminal nerve.

⚫ Blood supply-middle temporal artery,a branch of the superficial temporal artery and deep temporal artery,a branch of internal maxillary artery

⚫ Actions-when the temporal muscle contracts,its elevates the mandible and the teeth are brought into contact.

⚫ If only portions contract ,the mandible is moved according to the direction of those fibers that are activated.

⚫ Anterior portion contracts-mandible is raised vertically

⚫ Middle portion contracts-elevates and retrudes the mandible

⚫ Posterior portion contraction-controversial⚫ Dubrul states that the fibers below the root of

zygomatic process are the only significant ones and therefore causes elevation and significantly retrusion

⚫ Because the angulation of muscle fibers varies,the temporal muscle is capable of coordinating closing movements therefore it is a significant positioning muscle of the mandible

⚫ Elevation and retrusion

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⚫ MEDIAL(INTERNAL) PTERYGOID:

⚫ Origin-arises from pterygoid fossa

⚫ These fibers run downward,backward and outward

⚫ Insertion-medial surface of the mandibular angle

⚫ Along masseter muscle,it forms a muscular sling that supports the mandible at angle

⚫ Nerve supply-medial pterygoid ne4rtve,branch of trigeminal nerve

⚫ Blood supply-internal maxillary artery

⚫ Actions-contraction of fibers ,elevates the mandible and teeth are brought into contact

⚫ This muscle also active in protruding the mandible

⚫ Elevation and protrusion

⚫ EXTERNAL PTERYGOID(LATERAL):

⚫ ORIGIN-two heads of origin

⚫ Superior

⚫ Inferior

⚫ Superior-smaller than inferior and originates from infra temporal surface of the greater sphenoid wing

⚫ Inferior-it is larger -outer surface of lateral pterygoid plate and extends back ward,upward and outward

⚫ Insertion:-⚫ Superior-articular capsule ,disc and neck of the

condyle

⚫ Inferior-neck of the condyle

⚫ Nerve supply-buccal or masseteric branch of mandibular division of trigeminal nerve

⚫ Blood supply-branch of internal maxillary artery

⚫ Action-to open the jaws(depress) and to protrude the mandible

⚫ It is believed to be initiator of jaw opening

⚫ Unilateral contraction-it will the condyle and its attached disc anteriorly,lingually and inferiorly along the posterior slope of articular eminence,causing the mandible to move to opposite side.

⚫ It is therefore an important muscle in lateral movements of mandible

⚫ Important role in determining the position of the condyle relative to eminence

⚫ Protruding the mandible

⚫ Depression(closing) and protrusion

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⚫ DIGASTRIC:IT IS ONE OF SUPRAHYOID GROUP

⚫ Origin-two bellies,anterior and posterior

⚫ Posterior-from mastoid notch,just medial to mastoid process and fibers run forward,downward and inward

⚫ Anterior-from fossa on the lingual surface of mandible just above the lower border and close to the midline

⚫ Insertion –Two bellys are joined by the common tendon which is called as intermediate tendon which can slide through a fascial pulley attached to the hyoid bone.

⚫ Nerve Supply –Anterior part-Mylohyoid nerve of trigeminal nerve.

⚫ Posterior –branch of facial nerve .

⚫ Actions –They assist in retruding the mandible.

⚫ When left and right digastric muscles contract and the hyoid bone is fixed by the suprahyoid and infrahyoid muscles ,the mandible is depressed and the teeth are brought out of contact.

⚫ When the mandible is stabilized ,suprahyoid and infrahyoid muscle elevate the hyoid bone which is necessary for swallowing .

⚫ One of the muscles that are responsible for opening the mandible and raise the hyoid bone.

⚫ Suprahyoid muscles –muscles that are attached from the mandible to the hyoid bone.

⚫ Infrahyoid muscles –muscles that are attached from the hyoid bone to the clavicle.

⚫ Suprahyoid and infrahyoid play a major role in coordinating the mandibular function.

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⚫ GENIOHYOID:

⚫ Origin –Genial tubercles

⚫ Insertion-Hyoid bone

⚫ Nerve supply-1 and 2 cervical nerves via hypoglossal.

⚫ Action-Depress and retrude the mandible.

MYLOHYOID

⚫ Origin- Mylohyoid line on the inner surface of the mandible.

⚫ Insertion- hyoid bone.

⚫ Nerve supply –Mylohyoid nerve.

⚫ Action- To raise the hyoid bone ,the tongue and the floor of the mouth.

⚫ Group Action Of SupraHyoid Muscles:

⚫ Dual

⚫ To raise the hyoid bone on the base of the tongue during swallowing .

⚫ To help depress the mandible during the jaw movement

⚫ Infrahyoid Muscles:

⚫ They are located below the hyoid bone and draw it inferiorly

⚫ This group includes Thyrohyoid ,omohyoid and sternothyroid and sternohyoid.

⚫ Nerve supply-1,2 and 3 cervical nerves.

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⚫ FACIAL GROUP:

⚫ The muscles of the facial group number over 20, and the only two most relevant to the chewing will be considered here.

⚫ Orbicularis Oris :It runs transversly within the lips ,some of its fibres derived from the adjacent facial muscles.

⚫ Action: To close the lips⚫ To press the lips against the teeth ⚫ To protrude the lips.⚫ Nerve supply :Buccal branches of facial nerve.

⚫ Buccinator:

⚫ Main muscle of the cheek

⚫ It forms a wide, flat, muscular and lateral wall for the oral cavity.

⚫ Origin-It is on the alveolar process of the maxilla and mandible in the region of molars and from the pterygomandibular raphe.

⚫ Insertion: The fibres converge and insert anteriorly into the mucous membrane around the corner of the mouth via interlacing muscle fibres into the skin of the of the lateral parts of the lips.

⚫ Nerve supply :Buccal branches of the facial nerve.

⚫ Action :To cause tension in the cheek therby moving food onto the teeth from the lateral side and preventing cheek folds from being bitten by the teeth during jaw closure.

⚫

⚫ Cervical Group:

⚫ Indirectly involved in mandibular function .

⚫ They are Trapezius, Sternocleidomastoid ,Anterior vertebral muscles,the lateral vertebral muscles and other deep posterior cervical muscles.

⚫ They act to stabilize head posture during the active contraction of the masticatory ,suprahyoid and infra hyoid muscles during the mastication and swallowing

CONCLUSION

Knowledge of mandibular movements is important for the dentists for the fabrication of the complete dentures

Irrespective of the complete denture fabrication mandibular movements have to be understood to for the proper functioning and training to the patients.

REFERENCES

⚫ HUMAN ANATOMY _ CHAURASIA

⚫ GRAYS ANATOMY

⚫ HUMAN EMBRYLOGY INDEBIR SINGH

⚫ ESSENTIALS OF COMPLETE DENTURE PROSTHODONTICS WINKLER

⚫ TEXTBOOK OF PROSTHODONTICS BOUCHER

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Seminar on

TREATMENT PLANS FOR PARTIALLY AND COMPLETELY

EDENTULOUS ARCHES IN IMPLANT DENTISTRY

Presented by DR. SUDHIR MEENA

CLASSIFICATION OF PARTIALLY EDENTULOUS ARCHES:Classification of edentulous arches allows the profession to visualize and communicate the relationship of hard and soft structures.

Though there are 65,000 possible combination of teeth and edentulous spaces in a single arch, there are only few systems of classification which are familiar and accepted by the professional like Kennedy's, Cummer’s and Bailyn’s.

Kennedy’s classification of partially edentulous arches with Applegate's modifications is universally accepted.

Implantologists usually follow a classification [for diagnosis and treatment planning for partially or completely edentulous patients requiring implant prosthesis] by which the doctor is able to convey the dimensions of the bone available in the edentulous area and also indicate the strategic position of the segment to be restored.

The implant dentistry bone volume classification developed by Misch and Judy builds on the four classes of partial edentulism described in the Kennedy-Applegate system.

This facilitates communication among the large segment of practitioners already familiar with this classification and enables the use of common treatment methods & principles established for each class.

The implant dentistry classification for partially edentulous patients also includes the same four available bone volume divisions.

TREATMENT PLANNING CLASS I:Bilateral distal posterior edentulism with

natural anterior teeth.Majority of this class have only missing

molars and almost all have retained six or more anterior teeth.

These anterior teeth once restored to proper occlusal VD, contribute to the distribution of forces throughout the mouth in centric relation occlusion.

These anterior teeth also permit excursions during mandibular movement to disclude the posterior implant supported prostheses and protect them from lateral forces.

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On observation it is seen that most often class I patients have Division C bone- with either decreased width or height or length.The cause for reduction of the various dimensions is due to the fact that most often Class I patients are treated with removable partial dentures which when not properly designed cause rapid resorption of the bone in the edentulous areas as well as abutment area.

Class I Division A

a. Edentulous areas have abundant bone height(>10mm) & Length(>7mm) for endosteal implant

b. Direction of load is within 30º of implant body axis

c. Crown implant ratio is <1

d. Root form implants and independent prostheses often are indicated

Division B

a. Edentulous areas have moderate available bone width(2.5 to 5mm) and atleast adequate bone height(>10mm) & length(15mm).

b. Direction of load is within 20º of implant body axis.

c. Crown implant ratio is <1

d. Surgical options include osteoplasty, small-diameter implant and /or augmentation.

Division C

a. Edentulous areas have inadequate available bone for endosteal implements with a predictable result because of too little bone width,length,height or angulation of load.

b. Crown implant is>1.

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c. Surgical options incase of inadequate width include Osteoplasty or augmentation;for inadequate height Subperiosteal implants or augmentation.

d. Root forms may be considered with augmentation and for nerve repositioning

Division D

1. Edentulous areas have severely resorted ridges, involving a position of the basal or cortical supporting bone.

2. Crown implant ratio is >5

3. Surgical options usually in augmentation before implant are involved.

Also due to improper designing the remaining natural anterior teeth exhibit mobility due to overload. Therefore these patients often require the posterior implant prostheses to be independent from the mobile anterior teeth and in addition the occlusal scheme must accommodate the specific conditions of the mobile anterior teeth.

This requires greater attention and frequency for occlusal adjustments and more implant support in each posterior section than Class II or III.

❖The treatment plan must consider the factors of force previously identified and relate them to the existing condition.

❖Osteoplasty cannot be as aggressive in class I compared with completely edentulous patient because of the opposing anatomic landmarks.

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❖Augmentation procedures may be required to improve posterior bone volume, increase the implant surface area, and permit the fabrication of an independent implant restoration.

❖If the treatment is to be carried in stages, the posterior region with the greatest volume of bone is restored first.

CLASS II:

❖Partial edentulism with missing teeth in one posterior segment.

❖These patients are not likely to wear a removable denture as they may be able to function without a denture and as a result are less likely to tolerate or overcome the minor complications of wearing the prostheses.

❖The available bone is therefore often adequate for endosteal implant even when long term edentulism has been observed.

❖Still the local density of bone may be decreased.

❖Endosteal implants with minimal osteoplasty are a common modality in these patients, who are more often class ll Division A or B types.

❖Because the patients is less likely to wear a removable denture, the opposing natural teeth have often extruded into the posterior edentulous area. the occlusal plane and tipped or extruded teeth should be closely evaluated and restored as indicated to provide a favorable environment in terms of occlusion and forces distribution.

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CLASS III:

❖Bounded unilateral posterior edentulous space– either a single tooth or a long edentulous span.

❖A posterior edentulous region most often can be restored as an independent restoration but can also be joined to a posterior natural abutment.

❖But a single tooth implant is indicated

primarily in the posterior regions of

the mouth or when the patient does

not agree to crown the adjacent teeth

in the anterior region

CLASS IV :

❖Patients with anterior edentulous space that crosses the midline.

❖Lack of anterior bone is a common scene and therefore bone graft before implant placement becomes necessary to prevent the implants from being placed palatally in relation to the natural roots.

DIVISION A Treatment plans :

❖In class l or ll types, when an implant is considered an independent implant supported fixed prosthesis is usually indicated.

❖Two or more endosteal root form implants are required to replace independent molar prostheses.

❖The greater the no., of teeth missing, the larger the size and/or no., of implants required.

❖Posterior height is limited by the maxillary sinus or the mandibular canal and hence care should be taken during placement.

❖Partial dentures should be generously relieved or not worn at all during the healing process, esp., if parafunction is present.

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❖In class lll type, patients often have endosteal root implant placed in the edentulous space.

❖This situation is also indicated when occlusal forces are too great for the natural abutments to act as support for a fixed prostheses but are not mobile.

❖If the adjacent teeth are mobile, the implant must support both the missing teeth and mobile teeth during occlusion.

❖As a general rule, the final prostheses should be completely implant supported, and 2 implants should support each section of 3missing tooth roots [not 3 missing crowns].

❖Mobile natural teeth adjacent to the edentulous span cause greater loads on the implants, therefore 1 implant for each missing root may be indicated and the occlusion is adjusted to allow initial tooth movement before implant crowns contact in occlusion.

DIVISION B Treatment plans :❖Class l or ll patients have narrow bone in

posterior edentulous spaces and anterior natural teeth.

❖Osteoplasty is of limited application here. Endosteal small diameter root form may be placed in the posterior Division B edentulous region but greater no., are used than for Division A ridge. The smaller the diameter suggests the use of one implant for every missing tooth root, and no cantilever should be used.

➢ The patient missing molars and both premolars require additional implant support.

➢ Four division B root forms may be the foundation of an independent fixed partial denture, depending on the other stress factor.

➢Molar endosteal implants should not be rigidly cross splinted to each other in the class I patient. Flexure of the Mandible during opening may cause a rigid splint to exert lateral forces on the posterior implants.Hence, independent restorations are indicated.

➢Class III Division B patients have narrow –diameter endosteal implants placed in the middle of a long-span edentulous space.

➢ This treatment plan is primarily used for fixed prosthodontic treatment when the span is too long or occlusal forces are for great for the natural abutments to act sole support for the final prosthesis. The final implant prosthesis should be independent of these teeth.

➢ Class IV patient most often treated with augmentation before implant placement.

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➢ If the ridge is division B and inadequate in width for Division A root form implants, the narrow-diameter root forms compromise esthetics and oral hygiene procedures.

➢ Bone augmentation is more often used in anterior edentulous areas with narrow bone, so Division A root from implants may be used with improved crown contour,esthetics and hygiene. Implant and tooth replacement should remain independent.

➢ Canine is an important natural abundant.When missing, the final prosthesis includes both anterior and posterior natural abutments,which compromises the occlusal scheme.

➢ Likewise,single implants to replace canine one indicated but the occlusion should decrease the lateral loads by distributing some of the forces to the adjacent teeth.

➢A hydroxyapatite graft is often placed on the labial aspect of the Division B edentulous ridge for enhanced soft tissue contour, proper emergence profile and improved lip support for esthetics when pontics are used in the region.

Division C Treatment Plans

➢ In this case, several options must be considered.

➢ The first option, [unfortunate from an implantologists view] is to go for conventional removal partial prosthesis though a traditional soft-tissue borne restoration is possible but it worsens the bone loss.

Second option is to use bone augmentation procedures :

a. If the intention is to change it to Division B & A , autogenous graft is preferred.

➢ Most often used in Class I or II maxilla where sinus graft with a combination of allografts and autogenous bone are a predictable modality.

➢b. If bone augmentation is performed for improved ridge contour and soft tissue support only, non-resorbable HA is recommended. A convention soft tissue-borne prosthesis is then indicated and if there is adequate natural abutment support, fixed prostheses can be used.

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➢ Third option is to place a subperiosteal implant-more often is mandible. Mandibular circumferential(around the teeth) subperiosteal implants may be considered for class I patients.These implants can be treated with independent fixed prostheses with no attachment to natural teeth.

➢ Class III or IV patients rarely have subperiosteal implants. Augmentation is performed before endosteal implant placement in these patients.

➢ Fourth option in the mandible is nerve repositioning and endosteal implants in class I &II patients who are poor candidates for bone augmentation or subperiosteal implants.

➢However, certain disadvantages do exist like

a. Paresthesia- Hyperesthesia and pain

b. Grains of height only permit theplacement of 10mm high implants-

insufficient to compensate for the

increased crown height resulting

in unfavorable crown:root.

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➢ Class III & IV patient may have root forms placed without augmentation since the masticatory dynamics and bone density are not as unfavorable as the posterior regions.

➢ Maxilla usually require augmentation before implant placement.

Division D Treatment Plans

➢ Class I or II and Division D - seen commonly in the long term edentulous maxilla.

➢ Sinus graft performed before implant placement .

➢ Mandible- rare finding. If found (due to trauma or surgical excision of neoplasm) need autogenous bone onlay grafts to improve implant success and prevent pathologic fracture before prosthodontic reconstruction.

TREATMENT PLANS FOR COMPLETELY

EDENTULOUS ARCHES

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Classification of completely edentulous arches is also based on bone volume present.

➢ Edentulous jaw is divided into 3 regions:

1. Anterior –> Maxilla– between right& left I Premolars/ anterior to maxillary sinus.

Mandible– between right& left I Premolars/anterior to mental foramina.

2. Right posterior

3. Left posterior Maxilla- from right &

left II Premolars respectively

Mandible- Mental foramen

to the Retro molar pad

The classification of the edentulous jaw is then determined by the division of bone in each section of the edentulous arch.

The three areas are evaluated independently from each other. Hence, there may be one, two or three different divisions of bone.

TYPE 1

Type 1 edentulous arch the division of bone is similar in all three anatomic segments. Therefore 4 different categories of Type 1 arches are present.

Type 1 Division A ridge- abundant bone in all three sections, therefore as many root forms as needed may be used wherever desired to support the final prostheses.

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➢ Type 1 Division B ridge- adequate bone in all 3 sections to place narrow- diameter root form implants. The anterior section can be changed to Division A by osteoplasty to place full- size root form implants in this region.

➢ a. Type 1 Division C-w edentulous arches have inadequate bone width & therefore requires an autogenous onlay graft for implant restoration.

➢ Type 1 Division C-h edentulous arches have inadequate bone height. In this case, an implant supported or implant- tissue supported removable partial prostheses, is indicated to reduce occlusal loads.

Mandibular arch may be treated with a complete subperiosteal implant or root form implants in the anterior section.

➢ Maxilla is treated with conventional removable prostheses. For additional retention or stability HA can be used to augment premaxilla. Fixed prostheses may need autogenous graft to change the division and improve long term success and esthetics.

➢ Type 1 Division D- most challenging to traditional and implant dentistry because if an implant fails in this case, pathologic fractures or almost unrestorable conditions may result.

Endosteal implants may be placed in the anterior mandible. However, the unfavorable crown-implant ratio is often greater than 5 to 1 and mandibular fracture during implant placement or after implant failure may result in significant complications.

The best solution is to change the division with autogenous grafts, then reevaluate the improved conditions and appropriately alter the treatment plan. Autogenous grafts include iliac crest& particulate grafts. After 6 months a total of 6 to 10 implants may be placed.

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Type 2

➢ The posterior sections of bone are similar but differ from the anterior segment .the most common arches in this category present less bone in the posterior regions, under the Maxillary sinus or over the mandibular canal Type 2 A,C (Designated as Type2 followed by bone Division in the anterior segment and then bone Division in the posterior segment

➢ Type2 Division A,B arch has posterior sections that maybe treated with narrow-diameter implants, whereas the anterior section is adequate for larger diameter root form implants to support the prostheses

➢ The posterior Division B may be changed into Division A. Autogenous grafts are more debilitating and require extended healing periods, but indicated when stress factors and patient desires are high

➢ Type 2 Division A,C presents two primary modes of implant treatment

➢ The most common mandibular situation is to use only the anterior section for implant supported root form implants.The maxillary arch may be treated with the combination of sinus grafts and endosteal implants if additional posterior support is required for the prostheses.

➢ Type 2 Division A,D though uncommon,is treated in a similar manner as Type2 Division A,C

➢ Type 2 Division B,C can be treated with two main treatment options

The anterior section may be changed to Division A by Osteoplasty and then treated as Type2 Division A,C

The posterior Division may be changed by Sinus grafts to convert it into Division B

➢ Type 2 Division B,A – Anterior mandible maybe changed to Division C by Osteoplasty and a mandibular complete Subperiosteal implant may be selected as onlay are less predictable.

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➢ Type 2 Division B,D almost never occurs in the mandible, but it can be found on occasion in the maxilla.These patients are treated in a manner similar to patients with Type2 Division B,C

Type 3

➢ Posterior sections of the maxilla or the mandible differ from each other.

➢ Less common than other two types and more frequent in the maxilla

➢ Anterior bone volume is listed first then the right posterior followed by the left posterior

➢ Type 3 division A,B,C requires a narrow-diameter implant in the right posterior, root form in the anterior sections.

➢ Type3 Division A,C,B is treated as a mirror image of Type3 Division A,B,C

➢ Type3 Division A,D,C are A,C,D receives a treatment plan similar to Type2 Division A,C

➢ Even when the anterior region is similar to one of the posterior sections, the arch is Type 3.Anterior section usually determines the treatment plan.

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Velopharyngeal dysfunction and restoration of soft palate defects

DR. SUDHIR MEENA

Structures active in velopharyngeal closure

1 Velum (soft palate) : • the position and movement of the soft palate changes with age – at

birth and shortly there after ,the soft palate at rest is parallel to the roof of the pharynx (below the palatal plane) and closure is achieved by superior-inferior movement of the soft palate. In adults the closure occur above the palatal plane with an anterior-posterior movement of the soft palate.

• The extent of closure with posterior pharyngeal wall varies with head position. An extended head position results in deeper nasopharynx than when the head is held in the Frankfort plane

• The pattern of soft palate movement varies between men and women. Soft palate is longer, elevation is greater, the amount of contact with posterior pharyngeal is less, and the inferior point of contact is higher in men than in women.

• Musculus uvulae- it is responsible for velar stretch, velar eminence and is essential for normal velopharyngeal closure. Each of the two bundles of the musculus uvulae has its origin from the tendinous palatal popneurosis, which is posterior to the hard palate and anterior to the insertion of levator veli palatine muscle. The bundles converge above and at rt angles to the sling of the levator veli palatini, and redivide and insert into the basement membrane and connective tissue of the uvula.

• While the entire soft palate increases in length during closure, the central and posterior portions demonstrate a proportionally greater degree of lengthening along with thickening. This lengthening during closure has been termed velarstretch. The amount of velar stretch seems related to the task and/or anatomical or functional

• Pigott, describes the velar eminence as a large ridge occupying the central one third of the nasal surface of the soft palate and rising to a height almost equal to its width. He said that velar eminence was an essential component of velopharyngeal closure.

• Croft demonstrated hypernasal speech, small central gaps on velopharyngeal closure and normal palatal morphology on oral examination. This triad of conditions is delineated as occult submucous cleft palate. There is a lack of velar eminence in this condition.

• Levator veli palatine and other muscles- levator veli palatini are responsible for palatal elevation. Tensor veli palatini contributes little to the form and function of the soft palate, and that its primary function is dilation of the Eustachian tubes. The palatoglossus and palatopharyngeus create a downward pull on the soft palate and oppose the upward contraction of the levator. Therefore , the levator must contract more forcefully if the palatoglossus and/or palatopharyngeus contract forcefully. The important function of the palatoglossus and palatopharyngeus in speech is to aid in positioning the tongue and pharynx. If the palatoglossus contracts to aid in tongue elevation and/or the palatopharyngeus contracts to restrict the pharynx, the levator veli palatini must contract to achieve the desired velar elevation. Thus, there is a reciprocal relationship between the 3 muscles in positioning the soft palate and the tongue.

Tongue posture and movement may differ with velopharyngeal incompetence or insufficiency. These patients often have a more posterior and superior tongue position during speech. Warren – a high tongue position would increase vocal tract resistance for patients with velopharyngeal deficiency. This compensatory tongue posture assisted with soft palate elevation, contributes to the faulty articulation in these patients.e.g. the tongue contacted the soft palate during speech in 13 of 28 cleft palate patients , whereas , in a matched control group of normal patients , this contact was not observed.

2. Posterior pharyngeal wall : most normal speakers do not exhibit any detectable forward movement of the posterior pharyngeal wall during velopharyngeal closure. However with velopharyngeal incompetence and/or insufficiency , the degree of PPW mobility is more likely to be observed.In 1863 and 1869, Gustof Passavant

described a horizontal “cross roll” on the PPW which occurred during speech and swallowing in cleft palate patients. This forward bulge corresponds to the level of atlas, has been termed Passavant’s ridge or pad. This serves as a guide for proper placement of the soft palate obturator prosthesis.

3. Lateral pharyngeal wall: the lateral pharyngeal walls move medially to close against the velum or just behind the velum. The LPW movement is essential if normal speech is to be achieved with either prosthetic obturation or surgical reconstruction.

Velopharyngeal closure tends to be sphincteric in nature. Movement of the PPW blends with the movements of the LPW and soft palate. The level is at or slightly above the tori tubari (the median bulging of the pharyngeal terminus of the Eustachian tube.). Recently the level of closure of lateral velopharyngeal closure has been questioned. Croft found that it was approx 1cm below the torus tubaris, or at about the level of palatal bone.

The palatopharyngeus contributes little to the medial and posterior movement of the LPW. Its primary function is to mobilise the larynx and narrow the pharynx in speech and swallowing .

The palatoglossus muscle, which forms the anterior tonsillar pillar , acts as an antagonist for the levator veli palatini by elevating the tongue and lowering the soft palate.

Since both palatoglossus and palatopharyngeus narrow and bulge in their central portion during contraction, the imprint of both muscles can be noted during waxing procedures for construction of the obturator prosthesis for patients with extensive soft palate defects

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• At rest the soft palate drapes downward so that oral pharynx and nasopharynx are open and coupled , allowing normal breathing through the nasal passages . Classically when closure is required , the middle one-third of the soft palate arcs upward and backward to contact the PPW at or above the level of the palatal plane . The LPW move medially to contact the margins of the soft palate at or slightly below the level of the torus tubaris, and the PPW may move anteriiorly to facilitate contact with the elevated soft palate . Complete or near complete closure is required for normal deglutition and the production of some speech sounds, such as plosives . For other phonemes, such as vowels and nasal consonants, the velopharyngeal port will be open in varying degrees

• Variations in velopharyngeal closure:• Non pneumatic closure- swallowing,

gagging and vomitting • Closing is high in the nasopharynx and is

exaggerated • Pneumatic closure-sucking, whistling,

blowing, speech

• Innervation : the descrete and precise movements of the velopharyngeal complex during speech may be attributed to the facial nerve , while grosser movements are the responsibility of the vagus and glossopharyngeal nerves.

Velopharyngeal dysfunction

• Classification and etiology:VPD is the most common cause of

hypernasality. There are several types of VPD based on the basis of underlying cause. These are as follows-

1. Velopharyngeal insufficiency:Caused by anatomical defects. Refers

to patients with inadequate length of the hard and/or soft palate to affect velopharyngeal closure, but movement of the remaining tissues within normal physiological limits. The defect is secondary to a structural limitation.

e.g. History of cleft palate or submucous cleft

Short velum or cranial base anomalies

Post adenoidectomyIrregular adenoids Past maxillary

advancementEnlarged tonsils

2.Velopharyngeal incompetence :It is caused by physiological defects. Refers to patients with essentially normal

velopharyngeal structures, but the intact mechanism is unable to affect velopharyngeal closure.

e.g. Poor muscle function d/t h/o cleftVelar paralysis d/t brain stem or cranial nerve injuryDysarthria d/t central insultApraxia d/t congenital or acquired neurological causes

3.Velopharyngeal mislearning:Conversion disorderAbnormal posterior articulation of certain sound particularly sibilant soundPhoneme specific nasal air emission

Velopharyngeal dysfunction –effect on speech

1. Hypernasality – it occurs when there is too much sound resonating in the nasal cavity during speech. The severity depends on the size of opening , the etiology and even articulation .

2. Nasal air emission- it occurs when there is audible emission of air stream through the nasal cavity during consonant production specially during production of pressure sensitive sounds. Nasal grimace often accompanies

3. Weak or omitted consonants – reduced intraoral breath , pressure d/t nasal air emission causes consonants to become weak in pressure or even omitted.

4. Short utterance length – breath support for speech can be compromised when there is a significant leak of air pressure through a large VP opening

5. Compensatory articulation production- when the individual is unable to build air pressure in the oral cavity to produce sounds normally , he may learn to produce sounds in an alternate way by using air pressure in the pharynx.

6. Dysphonia- is(hoarseness, breathing, low intensity and glottal fry .) common in VP dysfunction. The cause is vocal fold nodules d/t strain that occurs throughout the vocal tract when attempting to close the VP wall or d/t use of glottal stops as a compensatory articulation production.

Oral sounding speech and nasal sounding speech

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Evaluation of velopharyngeal dysfunction

1. Perceptual assesment- resonance• By evaluating connected speech (spontaneous or reading )• Determine the type of resonance ( normal, hypernasal or

hyponasal , cul de sac resonance or mixed)• Rate on severity scale as mild, moderate or severe.2. Perceptual assesment-nasal emission , compensatory or

obligatory errors. Etc• single word articulation test • Repetition of pressure sensitive phonemes• Repetition of sentences with pressure sensitive phonemes• Counting for 60 to 70• Connected speech (spontaneous or reading)3. Intra oral examination• Cannot assess velopharyngeal function• Can evaluate oral structure and assess oral abnormalities.

4. Methods of evaluation of velopharyngeal closure by instruments

• Multiview videofluoroscopy: Skolnick and others in a series of classical studies, employed 3-D videofluoroscopy to examine the velopharyngeal mechanism in the frontal, sagittal, and base views simultaneously. From these recordings, they were able to trace the movements of soft palate, LPW ,PPW from rest to complete closure during speech and non speech tasks. In speech, only the superior fibers of superior constrictor appear to be involved during closure. In swallowing the pharynx is more forcefully involved in closure.

• Nasal endoscopy: this procedure has the advantage of visualisation of velopharyngeal sphincter from above, in the naso pharynx, without interference with the speech mechanism or exposing the patient to radiation.

• Patterns of closure as viewed with nasal endoscopy1. Coronal pattern: the majority of valving is palatal and accomplished by the

full width of the soft palate contacting the posterior wall. The lateral walls exhibit limited movement to contact the lateral margins of the velum. There is no PPW movement.

2. Sagittal pattern: the majority of the valving is pharyngeal. LPW move extensively to the midline and approx each other. The velum does not contact the PPW but elevates to contact the approximated LPW. The PPW does not contribute to the closure.

3. Circular pattern: there is equal participation from the soft palate and the LPW, with the contracting uvulae acting as a focal point. The LPW contacts the uvulae as it contracts and contacts the non mobile PPW.

4. Circular pattern with Passavant’s ridge: the same pattern as circular closure, except that the PPW (Passavant’s ridge) moves forward to complete the closure pattern around the musculus uvulae posteriorly.

• Pressure flow studies: this method was developed by Warren and co workers at University of North Carolina. This study helps in understanding of the physiology of speech complex. It has provided an insight into these complex inter relationship.

• velopharyngeal orifice size- Warren found that this opening should be less than .2cm sq. during the production of plosive and fricative sounds . If it is greater than .2cm sq the respiratory effort must be increased to compensate for velo pharyngeal inadequacy and provide improved oral pressure for speech.

• nasal resistance- the resistance to nasal airflow may contribute to increase oral pressure and , consequently , improve the effectiveness of speech for patients with larger velopharyngeal orifice.

• nasal valve-Laine introduced the concept of nasal valve. The valve is considered the area between the upper and lower lateral cartilages, pyriform aperture, and the anterior terminus of the inferior turbinates. Physiologically the nasal valve is considered as a regulator, with smallest cross sectional area with in the nasal cavity based on anatomical and flow resistive characteristics

• Oral vs nasal breathing- restrictions within nasal cavity may lead to oral breathing in repaired cleft lip and palate patient. Warren et al felt that individual with nasal valve areas less than .40cmsq should be considered to have impaired nasal airway and they will be predominantly oral breathers with the potential to alter the dento facial complex.

• Prosthesis evaluation- both nasal endoscopy and/or pressure air flow equipment have been used as an aid during prosthetic treatment. Oral nasal airflow data may be used to compute the nasopharyngeal orifice and nasal valve areas as guidelines during obturator fabrication and adjustment.

Prosthodontic rehabilitation• The objective of the obturation are to

provide the capability for the control of nasal emission during speech, and to prevent the leakage of material into the nasal passage during deglutition.

• Definitive obturation: Pts exhibiting considerable movement of the

residual velopharyngeal complex during function have an excellent prognosis for achieving normal speech with a prosthesis. Movement of LPW is essential for control of nasal emission. The obturator should be rigid and does not attempt to duplicate the movement of the soft palate. It is a fixed platform of acrylic resin which provides surface contact for the remaining musculature of the velopharyngeal mechanism during function. As a general rule , the following guidelines for location of the obturator segment of the prosthesis-

1. The obturator for an adult pt should be located in the nasopharynx at the level of normal velopharyngeal closure.

2. The inferior margin of the obturator should not extend below the lower level of muscular activity exhibited by the residual velopharyngeal complex.

3. The superior margin of the obturator should not extend above the level of muscular activity.

4. The inferior extension of the obturator will usually be an extension of the palatal plane, and extended to the PPW

Obturation of Total soft palate defects

• Methods of fabrication:• in obtaining impressions for diagnostic casts, the palatal portion of the stock tray

should be extended with wax so the defect will be recorded. Partial denture designs for the patients with defects or functional deficiencies of the soft palate and contiguous tissues are similar to partial denture designs for non surgical patients. However the long lever arm created by the extension of the obturator must also be considered. This extension is not within the confines of the bony palate and teeth, and this additional weight and length increases the effect of gravitational forces and the potential for rotation around the fulcrum line. The effect of this extension will be most significant for patients requiring Kennedy class I and II and minimal for patients with class III and IV partial denture design. For class I and II patients multiple indirect retainers are suggested , which will tend to resist the downward displacement of the obturator and increase the stability of the prosthesis.

• The stability and support can also be enhanced by covering as much of the hard palate as feasible.

• In patients with anterior edentulous area , consideration should be given to the placement of crowns on the adjacent abutment teeth with the attachment of an anterior tissue bar. The bar will act as indirect retainer and provide excellent stability and retention for the obturator extension. Modelling plastic is added to the tray resin. After the warm modelling plastic is placed in patient’s mouth ,the pt is instructed to move head in circular manner from side to side to extend head forward and backward and to speak and swallow.

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• These movements activate the remaining velopharyngeal musculature and mold the modelling plastic.

• A mouth temperature thermoplastic wax is added to the obturator , then the wax is heated and tempered , and the prosthesis is placed in the mouth. The functions activating the velopharyngeal musculature are repeated in order to reestablish the contours of the obturator. When contour of the obturator exhibits , the prosthesis is tempered in a water bath and replaced in the mouth for extended pd(1to3hrs).the prosthesis is removed and chilled in ice water

• The prosthesis is processed in heat or chemically activated acrylic resin.• The superior surface should be convex and well polished to facilitate

deflection of nasal secretions into the oropharynx. The tongue surface side should be concave.

• Size and position of the obturator- the lateral dimension are determined by the LPW and PPW movement. If the obturator is positioned correctly at the level of greatest LPW and PPW movement , a superior extension of 10mm is sufficient.

• Speech evaluation:the obturator is adjusted to the point where patient can produce a clear “p” and a sustained “”F” or “”s’” sound without emission of air through the nose , as well as understandable consonant sounds , such as “m”.

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Obturation of soft palate posterior border defects

• Median posterior border defect -preliminary impr should include the residual soft palate plus the defect posterior to the soft palate. Diagnostic cast obtained serves diagnostic purposes and is useful for adaptation of the wireloop extension for the obturator. The basic prosthesis is completed as before .

• If posterior border of the resected soft palate is scarred and exhibit little motion, it may be feasible to extent the obturator across the nasal surface of soft palate for a short distance. This extension provides some retention for the obturator and is esp helpful for edentulous patients.

• After the extension across the soft palate has been recorded, tray resin is added to the wireloop in the area of defect . Modelling plastic is then added and the pt is instructed to perform head and swallowing movement to mold the obturator . Thermoplastic wax is added to the obturator and the modelling procedure are repeated.

• After processing and prior to insertion the superior surface of the obturator is trimmed and rounded slightly to form a convex surface , and the extension of resin across the soft palate is thinned as much as possible. This extension will be approx 10mm wide and 2-3 mm thick. Usually , this width will not interfere with tongue function but excessive thickness of the resin can be bothersome.

• Lateral posterior border defect- these defect usually result from the surgical resection of sq cell ca arising from tonsillar tissue, retromolar trigone or postero lateral tongue region. Flaps are often used to close the lateral portions of the surgical defect, leading to an immobile LPW. As the wound contracts , the soft palate is pulled downward and forward , preventing normal soft palate elevation and compromising access to the velopharyngeal area therfore resurfacing these areas with myocutaneous or free flaps is preferred. Whatever the method of closure the prosthesis must engage the opposite and still functional LPW behind the residual soft palate in order to achieve velopharyngeal closure.

• Methods of fabrication – the complete or partial prosthesis must be constructed before the obturator can be fabricated. In most instances the residual soft palate and LPW on the defect side will display little movement. The residual soft palate does not exhibit normal elevation on the unresected side because the soft palate is tethered on the defect side. This condition leads to VPI behind the soft palate and medial to the oral defect. Consequently, to effect VP closure, the prosthesis must extend from the defect side superiorly behind the soft palate along the PPW to the opposite LPW.

• Implant retained and supported obturator prosthesis- if the soft palate defects has not resulted in the compromise of PPS area and the residual palatal structures are favorable, 2 implants placed in the premaxillary segment in the region of the cuspids, will be sufficient supplement to the retention,stability and support derived from the residual structures. If the defect has compromised the PPS area and/or the residual palatal structures provide insufficient stability and support, 4 or more implants should be placed. The retention provided by the implants can be positioned to maximize the antero-postero spread. In most patients, the number and distribution of implants will require that occlusal forces be shared between the implants anteriorly and the traditional denture bearing surfaces posteriorly and attachments which permit the prosthesis to rotate around a predictable access.

Special obturator prosthesis• Palatal lift prosthesis- it was first advocated by Gibbons and Bloomer. It is useful for

the patients with velopharyngeal incompetence who exhibit compromised motor control of the soft palate and related musculature e.g. myasthenia gravis,, bulbar poliomyelitis, CVA, cerebral palsy, traumatic brain injuries or injury to the soft palate (as sequlae following adenoidectomy, tonsillectomy or maxillary resection.) or with cleft palate patients with palatal insufficiency and sub mucous cleft palate . The objective of palatal lift prostheses is to displace the soft palate to the level of normal palatal elevation, enabling the closure by pharyngeal wall action. If the length of the soft palate is insufficient to effect closure after maximal displacement, the addition of the obturator may be necessary behind the displaced soft palate. Adequate LPW movement is necessary for the lift to be effective . A Space for breathing should be present laterally between the displaced soft palate and the pharyngeal wall at rest.

Advantages-1. The gag response is minimised d/t superior position and the sustained pressure of

the lift portion of the prostheses against the soft palate.2. The physiology of the tongue is not compromised d/t more superior position of the

palatal extension.3. The access to the nasopharynx for the obturator (if necessay) is facilitated4. Lift portion may be developed sequentially to aid patient adaptation to the prostheses5. The lift principle has application to a divese patient population that cannot be treated

as effectively with palatal surgery or other types of obturator prostheses.

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• Contraindications –1. Adequate retention is not available

for basic prostheses2. Palate is not displaceable 3. Patient is uncooperative Hardy felt that the hyperactive gag reflex

of the neuromuscularly handicapped child with a UMN lesion contraindicates the use of a conventional obturator prostheses. In his view lift prostheses minimise the gag response and therefore were the treatment of choice.

In order to achieve appropriate displacement of the soft palate, these prosthese are necessarily quite broad posteriorly and shaped like a beaver tail. Speech should be monitored for appropriate nasal resonance during the waxing sequence . the obturator can be extended behind the deficient soft palate if displacement doesnot achieve adequte obturation. The lift may be extended posteriorly gradually by sequential additions over several appointment if adaptation to the prostheses is difficult for the patient .

• Meatal obturator prostheses-described by Schalit and later advocated by Sharry. It establishes closure with te nasal structures at a level posterior and superior to the posterior terminus of the hard palate. It extends superiorly and slightly posteriorly from the hard palate border seperating the nasopharynx and the nasal cavity at the level of posterior chonae . There are no movable tissues in this area and closure is established against the turbinates, the , residual vomer , and the roof of nasal cavity. The palatal defect must be as wide as the area to be obturated . they are used infrequently but can be indicated for pts with extensive defects of soft palate who exhibit very active gag reflex . They may be obturator of choice for edentulous pts when retention is a problem. It is not as lengthy as conventional obturator as contact with mobile tissues is not a consideration . Thus less wt is added to maxillary CD . Also downward displacement force from obturator extension is closer to the supporting tissues of parent prostheses.

• Disadvantages-1. It does not enable the pt to control nasal air emission because it is

positioned in an area devoid of muscle function. Nasal airflow is created by drilling hole in the obturator or by reducing lateral extension.

Sharry suggested placing a hole or vent approx 5mm in diameter through obturator to permit nasal breathing . An alternate method is to place 2 small holes through the obturator to correspond with nasal compartment . Taylor and Desjardins suggested that the vent be placed in the superior 3rd of anterior surface and angled 45 degrees downward to minimise the regurgitation of fluid during swallowing.

• 2. distortions in nasal resonance are evident because the oral cavity and the oropharynx and nasopharynx are increased in size and nasal cavity is reduced proportionately.

• 3. the anterior surface of the meatal obt may act as a dam by hindering normal post nasal drainage patterns , leading to accumulation of mucous secretions anterior to prostheses thus requiring frequent cleaning

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WASTE DISPOSAL

in

Dental PracticesDR. SUDHIR MEENA

➢Introduction.➢Environmental hazards caused by materials used in dentistry.➢Regulations affecting dental practice.➢Planning.➢Designation.➢Categorisation.➢Segregation.➢Handling and storage.➢On-site treatment.➢Treatment off-site.➢Contingency planning➢Public relations.➢Summary and Conclusion.➢References.

CONTENTS

Introduction

Modern dentistry has been described as probably among the least hazardous of all occupations, although there remain many hazards in dental practice, like exposure to infectious diseases, radiation and mercury. Where the hazards cannot be excluded from the work place, good occupational hygiene practices need to be adopted by dental practitioners.

However, there is probably less awareness of the environmental impact we dentists have as individuals in our professional lives and of the remedial measures we should be taking.

Environmental hazards caused by materials used in dentistry

➢ Chemicals used like etchants and monomers, X-ray processing solutions, drugs etc cause inactivation of the biological systems.

➢ Contaminated needles and scalpel blades have been sources of infection and allergies.

➢ Base metal debris and mercury from amalgam cause poisoning of the biological systems.

➢ Liquid waste containing toxic substances flushed down a drain or sink to sewers, might affect the biological waste treatment works in the sewers.

Health hazards

Blood, body fluids and body secretions which are constituents of

bio-medical waste harbour most of the viruses, bacteria and parasites

that cause infection. This passes via a number of human contacts, all

of whom are potential ‘recipients’ of the infection. HIV,Hepatitis,

tuberculosis, pneumonia, diarrhoeal diseases, tetanus, whooping

cough etc., are other common diseases spread due to improper waste

management.

➢Improper practices such as dumping of bio-medical waste in municipal dustbins, open spaces, water bodies etc., leads to the spread of diseases.

➢Emissions from incinerators and open burning also leads to exposure to harmful gases which can cause cancer and respiratory diseases.

➢Exposure to radioactive waste can in the waste stream can also cause serious health hazards.

➢Bio-medical waste can cause health hazards to animals and birds.

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➢Hence as a measure for the safe disposal of dental

waste, different organizations around the globe have

developed regulations to safeguard the natural

environment.

REGULATIONS

AFFECTING

DENTAL

PRACTICE

Dental offices are subject to a variety of national, state, and

local regulations concerning the safe handling of their waste

materials. The US Congress set up few agencies for this

purpose, for e.g.,

➢Environmental Protection Agency (EPA)

➢Occupational Safety & Health Administration (OSHA)

➢Centers for Disease Control and Prevention (CDC).

The EPA's mission is to protect human health and to

safeguard the natural environment (air, water, and land.)

OSHA’s mission is to prevent work-related injuries,

illnesses, and deaths. OSHA promulgates regulations, also

known as “standards,” which have the power of law. OSHA

then applies the tenets of its standards through inspections

and when necessary the imposition of citations and

penalties.

The CDC’s mission is to promote health and quality of life by

preventing and controlling disease, injury, and disability. The

CDC is interested in the well being of healthcare workers,

their patients, and the community. Advice to healthcare

providers usually comes in the form of

recommendations. CDC recommendations, however, are

usually so well developed they commonly serve as industry

“gold” standards.

To be in compliance, dental offices must first be aware of all

mandates - national, state and local rules - concerning

regulated waste applicable in their area.

➢In exercise of the powers conferred by section 6, 8 and 25 ofthe Environment (protection) act, 1986 the central government,om

2nd June notified the rules for the management and handling of bio-medical waste. These rules are called the Bio-Medical Waste (Management and Handling) (Second Amendment) Rules, 2000.

➢These rules apply to all persons who generate, collect, receive, store, transport, treat, dispose, or handle bio medical waste in any form.

➢According to this,"Bio-medical waste" means any waste, which is generated during the diagnosis, treatment or immunisation of human beings or animals or in research activities pertaining thereto or in the production or testing of biologicals.

The Bio-medical Waste (Management and Handling) (Second Amendment) Rules,2000.

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PLANNING

A regulated waste management plan contains a number of important components. These include

1. Designation

2. Categorization

3. Segregation

4. Handling And Storage

5. On-Site Treatment

6. Treatment Off-Site

7. Contingency Planning

8. Public Relations.

DESIGNATION

Many people mistakenly consider the terms hospital

waste, biohazardous waste, biomedical waste, red bag

waste, medical waste, and infectious waste to be

synonymous. However, hospital waste, dental office waste,

or household waste refers to the total discarded solid waste

(which includes solids, liquids, semi-liquids, and gases)

generated by all sources within a given location.

Various Types of Waste

Contaminated Waste

Items that have had contact with blood or other body fluids and secretions, such as saliva.

Infectious Waste

Waste capable (as shown through epidemiological studies) of causing an infectious disease - sufficiently contaminated with blood or other body fluids so as to be able to transmit disease.

Medical /Dental Waste

Any solid waste that is generated in the diagnosis, treatment, or immunization of human beings or animals in research pertaining thereto, or the production or testing of biological agents. The term does not include hazardous waste (e.g., harsh or reactive chemicals) or household waste.

Regulated Waste

Infectious medical/dental waste that requires special storage, handling, neutralization, and disposal.

Infectious waste is a small subset (estimated to be 3% in

hospitals and 1-2% in dental offices) of the total waste to be

discarded. Infectious waste is the part of medical/dental

waste that has been shown, through controlled studies, to be

capable of transmitting an infectious disease. For e.g.,

contaminated sharps, teeth, pathological waste and blood

soaked items. Also known as hazardous waste.

Factors such as the number and virulence of the

microorganisms present, host resistance, and the presence

and availability of portals of entry play important roles in

whether an infection does or does not occur.

Regulated waste, according to OSHA definition, is liquid or

semi liquid blood or other potentially infectious materials and

items that would release blood or other potentially infectious

materials if compressed.

Other potentially infectious materials are body fluids that are

visibly contaminated by blood.

Infectious/hazardous waste is also included under

Regulated Waste because certain segregation, storage, and

disposal procedures must be followed.

While this waste is in the dental office and a potential hazard

to the employees, it is covered by OSHA regulations.

CATEGORIZATION

Many categories of infectious waste have been

proposed. The real qualification is if an item or material

meets the scientific definition of “shown capable of producing

an infectious disease.”

For dental offices, there are five types of regulated waste. All

five possess the capabilities of transmitting infectious

diseases and, therefore, require special handling, storage,

and disposal methods

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The five types are:

1. Bulk (in a liquid or semi-liquid form) blood or blood products and other potentially infectious materials, OPIM (for dentistry, saliva is considered to be as hazardous as blood);

2. Items such as a cotton roll saturated with blood/saliva or OPIM which readily release fluids during handling (by squeezing or are actually dripping or caked);

3. Pathologic waste (e.g., exfoliated or extracted teeth);

4. Used sharps (contaminated items that can penetrate intact skin), such as injection needles, scalpel blades, instruments, burs, and broken contaminated glass;

5. Potential sharps, such as anesthetic carpules, which can contain aspirated blood and could break possibly causing injury and exposure.

SEGREGATION

•All waste from dental offices can be divided into two basic categories: Regulated and Non-regulated.

•Regulated waste must be placed into appropriately designed containers, usually red biohazard bags or sharps boxes.

•Ideally, segregation should occur as close as possible to the point of origin.

•The person disposing of an item should know best which type of container to select.

•Segregation increases patient and practitioner safety and prevents contamination of non-regulated waste.

•The majority of soiled items are not regulated waste. For

example, used gloves, masks, and gowns are not considered

regulated dental waste and thus can be added to the regular

trash.

•The same is true for environmental barriers (e.g., plastic bags or

sheets and aluminum foil) used to cover equipment during

treatment.

HANDLING AND STORAGE

➢ Safe handling of regulated waste is essential. Written procedures will help in this process. Involved personnel must be informed of the possible health hazards present and trained in appropriate handling, storage, and disposal methods.

➢ Stored regulated waste must be placed into labeled or color-coded bags or containers. Usually such items are red and have biohazard symbols attached.

➢The receptacles should be covered with properly fitted lid that can be opened with a foot pedal. Keeping the lid closed prevents air movement, as well as the spreading of contaminants.

➢Waste receptacles should be lined with sturdy plastic bags that can be removed without touching the interior of the liner. Double-bagging of liners may also be recommended to eliminate accidental exposure should one of the bags rip or tear.

➢Ideally, regulated waste should be stored as soon as possible with a minimum of transport.

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➢Maintaining bag and container integrity is vital and overfilling must be avoided.

➢Regulated waste must be stored in a properly ventilated, secured area that cannot be readily seen by patients.

➢Generally, waste should not be stored for more than 30 days.

➢Waste containers must be designed to prevent the development of offensive odors.

➢Waste is discarded in a leak - resistant package that is impervious to moisture.

➢The bag is sealed to prevent leakage during transportation to the final dumpsite.

➢If hazardous waste is shipped, store the containers in an

exclusive refrigerator to maintain the integrity of the contents

and to control odor until the pick-up date.

➢In almost all locations, blood in a liquid or semi-liquid form,

even when mixed with other fluids such as saliva, can be

poured or evacuated directly into the office waste water

system. Sink traps and evacuation lines should be thoroughly

rinsed at least daily. Passage of an effective, environmentally

compatible disinfectant or evacuation cleaner (low sudzing)

through the system would help. A final water rinse should

follow.

Non-Hazardous waste

➢Disposable paper towels, paper mixing pads, disposable

covers of operating surfaces.

➢Should be discarded in separate covered containers made

of durable material such as plastic or metal receptacles.

➢For ease in handling, the receptacles should be lined with

plastic bags.

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OSHA HOUSEKEEPING REQUIREMENTS

The housekeeping section of the OSHA Bloodborne Pathogens Standard includes provisions for handling :

➢Contaminated sharps

➢Spills

➢Broken contaminated glassware

➢Regulated waste.

Sharps.

The term sharp means any sharp or pointed object that can penetrate the skin or oral mucosa. In dentistry, the most common types of sharps are:

➢Needles

➢Scalpel blades and disposable scalpels

➢Exposed ends of dental arch wires

➢Broken glass

➢Burs and endodontic instruments

The OSHA Bloodborne Pathogens Standard contains specific guidelines concerning sharps containers:

➢ Sharps containers must be closeable, leak-proof, puncture-resistant items labeled with a biohazard symbol or color-coded red to identify it as a hazard.

➢ They should be capable of maintaining their impermeability during storage, transport, treatment, and disposal. This will help prevent occupational exposure to container contents.

➢Sharps should be quickly placed into sharps containers after use. They must be placed into acceptable containers as close as practically possible to their point of use.

➢Sharp items should be considered as potentially infectious materials and thus handled with extraordinary care to prevent accidental injuries.

➢Contaminated sharps are never touched with bare hands, but by wearing appropriate gloves or by using transfer forceps.

➢Sharp containers should be replaced routinely before they are over filled.

Discarding used needle.

Of special concern among contaminated sharps are used needles. The CDC estimates that healthcare workers sustain nearly 600,000 percutaneous injuries annually involving contaminated sharps. In response to a continuing concern of exposure and the development of technological advances that increase employee protection, the US Congress passed the Needlestick Safety and Prevention Act in 2000. Enforcement of the new provisions in the standard began on July 17, 2001.

Proper handling of sharps is essential because personal protective barriers, such as gloves, will not prevent all needlestick accidents. To minimize the potential for exposures, needles should not be recapped, bent, or broken by hand.

Instead a “hands-free” or a “one-hand” technique must be used.

The hands free technique involves the use of a cap holder, which allows the slipping of the needle into it without touching it.

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In a one-hand technique, the needle guard is placed on a tray, and the used needle is wiggled into the cover. Once the end of the needle is covered, it maybe safely brought in to position.

The recapped needle is then discarded in the nearest sharps container.

Needle disposal unit.

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Infectious material spills.

➢ Spilled or dropped potentially infectious materials such as gauze saturated with blood, must be cleaned up immediately.

➢Utility gloves and protective barrier clothing are worn.

➢The area of spillage is wetted with a suitable disinfectant such as 1:10 sodium hypochlorite solution.

➢Use a large wad of paper towels so that the gloves do not contact the liquid. Discard the towels after use.

➢Apply the disinfectant again. Leave the area wet for 10 mins and then dry it with fresh paper towels.

➢Remove gloves carefully to avoid touching the contaminated outside, and wash hands immediately. Wash, dry and autoclave gloves after use.

Broken glass.

➢If contaminated broken glass or something sharp drops, do not pick it up with the hands. Instead use tongs, forceps, or a dustpan and brush.

➢Discard, clean and disinfect, or sterilize items used for this purpose.

➢Broken glass or dropped sharps are discarded in the sharps container.

➢After the sharp material has been removed, disinfect the area as after a spill.

Discarding local anesthetic cartridges.

➢If the glass anesthetic cartridge is broken, pick up the broken glass as previously described and discard the broken glass with the sharps.

➢If the glass anesthetic cartridge is not broken and not visibly contaminated with blood, discard it with other nonhazardous waste.

➢If the glass anesthetic cartridge is visibly contaminated with blood, discard it with regulated waste.

Laboratory specimens

Medical lab specimens, such as biopsy samples of

suspected oral cancerous lesions, to be transported

outside of the office for evaluation must be placed in

leakproof bags and labeled appropriately.

Dental impressions must also be placed in leakproof bags

and labeled appropriately.

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Contaminated laundry

➢The dental personnel should either use disposable

uniforms or make arrangements for laundering or

professional cleaning of protective clothing.

➢Clothing dispatched to a commercial laundry should be

packed in red laundry bags, clearly labeled with a

biohazard symbol.

Mercury from dental amalgam.

➢ Placement and removal of dental amalgam restorations generate amalgam waste particles that can be suctioned into the dental unit vacuum line and discharged in to the public sewer system.

➢Waste water treatment plants are facing increasing pressure from environmental regulators .

➢treatment plants are looking to identifiable sources of mercury or mercury containing waste .

➢Mercury compounds may be absorbed by organisms and concentrated as they pass up the food chain.

➢But available data suggest that the solubility of the metals in amalgam, in tap water or sewerage is very low.

Amalgam disposal.

Three aspects of amalgam waste may be considered.

➢Amalgam scrap.

➢Other waste contaminated with amalgam.

➢Amalgam in waste water.

Amalgam scrap: Is stored under radiographic fixer solution in a covered container. Should be recovered and recycled whenever possible. It is considered as hazardous waste with chances of mercury leaching out of amalgam scrap. Hence they should be disposed off as required for that of a regulated waste and as per local regulations. It should not be disposed with waste that would be eventually incinerated since amalgam decomposes on heating.

Other waste contaminated with amalgam: like amalgam

capsules, extracted teeth with amalgam restorations, cotton

rolls and gauze with amalgam particles. Here again they should

not be incinerated and should be recycled or disposed off as

regulated waste in sealed leak proof bags.

Amalgam in waste water:

➢Chairside traps and vacuum pump filters.

➢Sedimentation tanks.

➢Electrical and chemical separation

➢Commercially available amalgam separators.

Amalgam separators

They are devices used to remove amalgam waste particles in dental office discharge by several separation techniques, either alone or in combination, like:

➢Sedimentation.

➢Filtration.

➢Centrifugation.

➢Ion exchange.

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Management of mercury spills.

➢Never use a vacuum cleaner, broom or paintbrush or household cleaning products like ammonia or chlorine.

➢Never allow mercury to go down the drain.

➢In case the shoes are contaminated with the spilt mercury, the person is asked not to walk around or leave the spill area until the contaminants are removed.

➢Sprinkling of sulfur powder on mercury spills has shown to be ineffective and inadequate to control the problem, because of the slow reaction.

➢Mercury spills are cleaned up properly by using trap bottle, tapes, or fresh mixes of amalgam to pick up droplets, or use commercial clean up kits.

➢If the floor carpeting in the operatory gets contaminated with mercury, removal of the carpeting may be the only effective way to ensure decontamination. Chemical decontamination of the carpeting may be ineffective since mercury might seep through the carpet and remain inaccessible to the decontaminant.

Managing silver and lead waste.Silver in used radiographic fixer solutions

➢Use of an in-office silver recovery unit to remover silver from used fixer solutions and recycle the used cartridge.

➢Send used fixer solution to a silver reclaiming facility.

➢Send it to a medical radiology lab or a commercial photographic processing lab, on agreement.

Lead foil in intraoral radiograph film packets.

➢Should be collected and recycled through a licensed facility.

➢The same would apply to lead aprons and lead collars.

ON-SITE TREATMENT

Many areas allow in-house treatment of regulated medical/dental waste. An easy and effective procedure is sterilization by moist heat (autoclaving). Dry heat ovens should not be used. Of course, the performance of the sterilizer must be biologically monitored regularly.

Where allowed, sharps containers can be sterilized in-house. The open containers should be placed into the sterilizer in an upright position.

Recommendations Procedures for Sterilization of Sharps Containers in Steam Autoclaves

1. 1. Use only containers approved for the collection and storage of sharps and

which are autoclavable.

2. 2. Biologically monitor the autoclave used on a regular basis (e.g., weekly).

3. 3. Consider the following procedural recommendations:

a. a. Fill containers no more than ¾ full

b. b. Leave container vents open

c. c. Place the containers in an upright position in the autoclave chamber

d. d. Process containers for 60 minutes (e.g., two regular length cycles, unless a

single longer cycle can be used)

e. e. Remove containers after processing and allow them to cool

f. f. Carefully close container vents

g. g. Label and dispose of containers according to local governmental regulations

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➢In-house treated regulated waste items can then be added to the non-regulated office waste. These items should be labeled as “treated” or with other information as required by local laws.

➢Pathologic waste is considered to be potentially infectious and must be regulated.

➢Teeth without amalgam restorations and other tissues can be placed directly into a biohazard bag or a sharps container. Where allowed, the waste can then be sterilized.

➢Teeth with amalgams could release mercury vapor during sterilization, thus, they should be neutralized through disinfection (ideally, immersion for 30 minutes in a fresh solution of a tuberculocidal disinfectant held within a sealed container). Treated teeth can then be rinsed with water and are ready for disposal or returned to pediatric patients.

➢Items heavily soiled (even saturated) with blood/saliva can

be placed into a sharps container. However, it may be easier

to store them in small biohazard bags until treated. Used

anesthetic carpules should also be placed into sharps

containers.

TREATMENT OFF-SITE

Some areas may require regulated waste be removed,

neutralized, and disposed of by a commercial waste hauling

service, regulated by the local government.

Final disposal

Chemical decontamination can be carried out in a special

decontamination tank with drainage facilities and also a chain

and pulley block for loading/introducing operations of the large

buckets in which the waste are placed for decontamination.

Disposal of incinerator ash

The ash generated by the incinerator can be disposed of in an

Engineered Band fill which is chemically treated to prevent

seepage of metal into the earth. The ash generated by

incineration will contain mercury, arsenic, lead and cadmium all

heavy metals harmful to the human body.

The Bio-medical Waste (Management and Handling) (Second Amendment) Rules, 2000 states the colour coding and type of container for disposal of bio-medical wastes:

Colour Coding

Type of Container -I Waste Category Treatment options/disposal.

Yellow Plastic bag Human Anatomical Waste, Soiled Waste(Items contaminated with blood, and body fluids including cotton, dressings, soiled plaster casts)

Incineration/deep burial

Red Disinfected container/plastic bag Soiled Waste(Items contaminated with blood, and body fluids including cotton, dressings, soiled plaster casts), Solid Waste(wastes generated from disposable items other than the waste sharps such as tubings, catheters, intravenous sets etc).

Autoclaving/Micro waving/ Chemical Treatment/shredding

Blue/White Translucent

Plastic bag/puncture proof Container.Solid Waste(wastes generated from disposable items other than the waste sharps such as tubings, catheters, intravenous sets etc), Waste sharps(needles, syringes, scalpels, blades, glass, etc.)

Autoclaving/Micro waving/ Chemical Treatment and destruction/shredding

Black Plastic bag Discarded Medicines and Cytotoxic drugs(wastes comprising of outdated, contaminated and discarded), Chemical Waste(chemicals used in production of biologicals, chemicals used in disinfection, as insecticides, etc.)

Disposal in secured landfillchemical treatment and discharge into drains for liquids and secured landfill for solids

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CONTINGENCY PLANNING

It is best if offices prepare sets of written procedures concerning their regulated waste. Such prepared programs should always list the person or persons responsible in the event of an emergency.

The success of any safety program is highly dependent on proper employee training and employer monitoring. All office personnel must be well versed in the handling, storage, treatment, and disposal of regulated medical waste.

PUBLIC RELATIONS

➢A good portion of the population has an aversion to blood (liquid or dried) and medical/dental sharps, especially needles. Such anxiety also can exist among those charged to collect, haul, and dispose of waste.

➢It would be best if properly treated and labeled regulated waste containers were placed within some other type of container (e.g., cardboard boxes) that can more readily conceal the actual contents. This is an example of “out-of-sight…out-of-mind.”

SUMMARY

Proper handling, neutralization, and disposal of regulated

dental waste are important elements of every dental office’s

infection control program. Correct procedures will help protect

office employees and patients, contract workers, and the local

community. An effective program is based on planning, which

includes a firm understanding of the regulations that apply in

their location. All office personnel must be knowledgeable as

to the correct procedures and the appropriate equipment. .

CONCLUSION

As producers of hazardous waste, dentists have a responsibility and a duty of care for the correct management of waste within their practice.

If properly designed and applied, regulated waste management can be a relatively easy and inexpensive venture, yet one that is also an effective and efficient compliance-related practice.

REFERENCES.

➢ Council on dental materials and devices, Council on dental therapeutics; Infection control in dental office; JADA 97;4:673-677,Oct1978.

➢ Council on dental materials instruments and equipments, Council on dental therapeutics and practice;Infection control recommendations for the dental office and the dental laboratory ; JADA: 116;Feb1988.

➢ Recommended clinical guidelines for infection control in dental education institutions: Journal of Dental Education;55:9;1991.

➢ States act to regulate medical waste:JADA;122:Sep1991.

➢ P.L. Fan, Dorthe Arenholt-Bindslev;Environmental issues in dentistry- mercury;International Dental Journal: 47;2:1997.

➢ Nairn H.F.Wilson,EdwardG.Bellinger;Dental practice and the enviornment,International Dental Journal:48:3;161-166,1998.

➢ Amalgam in dental office wastewater,JADA: 133;585-588;May2002.

➢ ADA Council on scientific affairs Managing silver and lead waste in dental offices,,JADA,134:1095-1096;Aug2003.

➢ KEVIN. R. MCMANUS,P.L.FAN:Purchasing , installing and operating amalgam separators- Practical issues;JADA;134,1054-1065:Aug2003.

➢ ADA Council on scientific affairs Dental mercury hygiene recommendations , :JADA;134,1498-1499;Nov2003.

➢ HAZEL. O. TORRES et al : Modern dental assisting 5th edition .

➢ Clifford.M. Sturdevant et al :The art and science of

Operative dentistry 3rd edition .

➢ Ann Ehrlich et al ; Essentials of dental assisting :2nd edition.

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