overdentures / orthodontic straight wire technique

OVERDENTURESINDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

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DEFINITION:

Overdenture is defined as a removable partial

denture or a complete denture that covers and rests

on one or more remaining natural teeth, the roots of

natural teeth, and/or dental implants.

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RATIONALE OF OVERDENTURES:

Retention of any tooth for an overdenture preserves a portion of one of the major sensory inputs i.e. input from the periodontal propioceptors, which contain information about the magnitude and

direction of the occlusal forces as well as about the size and consistency of the food bolus. This along

with the input of other receptors in the mouth, muscles, TMJ contribute to the overall response. The periodontal receptors input are also protective against occlusal overloading. Extraction of all teeth

results in total loss of all input from periodontal ligament receptors; where as use of an overdenture

preserves the sensory input. www.indiandentalacademy.com

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The natural anterior teeth give more discreet sensory input, but posterior teeth should also

be retained for overdentures whenever feasible even though their sensory input is lesser.

It is also known that the retention of teeth for overdentures provide better sensory feed

back regarding masticatory performance.The use of an overdenture preserves

alveolar bone, especially in the area of the retained teeth.


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Advantages of overdentures Equally effective and superior method of treatment Simplicity of construction Ease of maintenanceStabilityRetentionEsthetic excellenceOpen palate possibleReasonable costFamiliar Procedures Ease in making measurements Ideal OcclusionExcellent patient acceptance


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Less trauma to the supporting tissuesStabilization of existing structures Minimal adjustmentPossibility of using attachments or soft liners Transitional or training denturesConversion to complete denture ReversibilityEase in Cleaning Proprioceptive response Distribution of forces of mastication Fewer post insertion problems


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Disadvantages of overdentures

The overdenture treatment is more expensive than conventional denture treatment due to the endodontic therapy usually required and the subsequent restoration of the teeth with alloys or gold copings. Frequently teeth to be retained also need periodontal therapy.

The overdenture is bulkier than the fixed or removable partial dentures.

Many patients do not like any removable appliance and therefore may prefer a fixed partial denture. www.indiandentalacademy.com

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If the patient does not keep the retained roots or teeth and the overdenture clean, caries and periodontal disease may progress.

Maintenance problems:

Copings may become looseAttachment wear, loss and breakage

Alveolar ridge resorption Overdenture breakage Oral hygiene problems


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Indications: Younger the patient greater the indication In situations where retention is difficult to obtain

a. Absence of alveolar residual ridgeb. Xerostomiac. Loss of maxilla or partial loss of

mandible d. Congenital deformity (i.e. Cleft palate)

For patients with poor prognosis for complete dentures

a. High palatal vault and ridge slope b. Poorly defined sublingual fold spacec. In class III tongue patientsd. Knife edge ridge


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When pronounced vertical overlap is required to produce the desired esthetic result.

Unilateral overdenture can be given to provide good function and esthetics when a large amount bone and soft tissues have been lost on one side of the arch

Patient with badly worn out teeth.

When complete denture will be opposed by retained mandibular anterior teeth preventing combination syndrome.


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Contraindications:

Uncooperative: Under motivated patients

Psychologically some patient cannot accept removable prosthesis

Mentally and physically compromised

When patient cannot economically afford


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Contraindications for Endodontically involved teeth

Contraindications for periodontally involved teeth

• Uncorrectable soft tissue and osseous defects• Failure to establish sufficient zone of attached gingiva• Class III Mobility

• Vertical fracture• Mechanical perforation of root• Broken instrument• Horizontal fracture of root below bony

crestwww.indiandentalacademy.com

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Oligodontia

Types of over denturesI. Overdentures for congenital and acquired

defects:


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Class III Patient with missing teeth


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Patient with eroded teeth


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II. Transitional overdentures:

A Transitional or interim overdenture is made from an existing removable partial denture, the patients own teeth or from both. Frequently, the entire procedure can be done while the patient waits, or part of it can be done before the extraction visit. The objective is to do the most for the patients with the least of trauma.


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III. Immediate overdenturesAn immediate overdenture is an overdenture constructed for insertion immediately after the removal of natural teeth. It may be used as an interim prosthesis. The immediate overdenture enables a dentist to use a simplified construction technique that allows flexibility in planning treatments as requirements change. Many times with good oral hygiene and regular professional supervision an immediate overdenture may have a long life. Sometimes, it can be a prognostic aid before a more comprehensive overdenture procedure. If prognosis is poor and response to treatment is poor and immediate denture can be converted into a serviceable complete denture.


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IV. Remote overdenturesA remote overdenture is an overdenture other

than transitional or immediate. It is usually constructed for insertion at sometime remote from the removal of hopeless natural teeth.

The remote overdenture usually placed on well healed ridges usually after a period of satisfactory experience with an interim

overdenture which may be transitional or immediate. Although remote overdentures can

be entirely constructed of resin, metal bases are frequently used.


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Metal base overdentures:A metal base overdenture is complete denture with a cast metal base that is supported and

stabilized by selected natural teeth with contours that are modified for the purpose by preparation

and placement of copings.


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Metal base Overdenture


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V. Removable partial denture:A superior removable partial overdenture can be made for may patients by reducing some of the remaining teeth coronally so that the

prosthesis can be fabricated over them.

Tooth preparation Removable partial overdenturewww.indiandentalacademy.com

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VI. Implant overdentures

A wide variety of implant types and procedures have been used with an overdenture as the means of a

final restoration. The osseointergrated approach of implants with its use of titanium metal and rather

sophisticated techniques of placement has proven to be viable and worthy procedure. Although it is used

mostly with fixed type of prosthesis, on occasion single fixtures are placed on each side of the midline

and an overdenture is fabricated over fixture.


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DOWEL DESIGNS

There are mainly 5 categories:

1. Customized cast dowels 2. Prefabricated resin patterns 3. Prefabricated metal dowels

4. Threaded dowels5. Dowel systems


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1.CUSTOMIZED CAST DOWELS

When a dowel and coping are waxed together and cast as a unit the discrepancy is the same as when making an inlay and crown in the same casting. If the expansion for the coping were sufficient, the dowel would be oversized, the coping could not

seat, and the dowel could fracture the root during either try-in or cementation because of the wedge effect and the hydrostatic pressure of the cement. This factor can be reduced by preparing cement

-release groove down the long axis of the dowel. If the dowel were undersized, the coping would seat

properly, but the dowel would be retained by cement only.www.indiandentalacademy.com

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2. PREFABRICATED RESIN PATTERNSThe prefabricated dowel patterns are provided

with a matched set of burs for preparing the dowel space. The cross sectional strength of a pattern dowel is considerably less than that of a prefabricated metal dowel of the same size, for the metal dowels are drawn from a high fusing

alloy, different than that used for the copings, and do not have the potential porosity and fracture of

a cast dowel.


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3.PREFABRICATED METAL DOWELS

The prefabricated metal dowels have a big advantage over the two previous systems because of the exact fit and high metallurgic strength in the cross sectional area; they require minimal enlargement of the canal space and strengthen the tooth rather than

weaken it. The prefabricated metal dowels have matched sets of burs for exact fit of the preparation. The dowels are machined from high-fusing wrought metal that is specially alloyed for dowel usage. Most of these dowels have cement release grooves, which avoid the possible risk of incomplete seating or root

fracture during cementation.www.indiandentalacademy.com

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4.THREADED DOWELSThreaded dowels provide mechanical fixation in

addition to cementation. The VK and Kurer systems offer excellent retention with the

threading.5.DOWEL SYSTEMS

Schenker step pivot (European). V K and Kurer systemwww.indiandentalacademy.com

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CLASSIFICATION OF OVERDENTURES

Heartwell:I . NoncopingII. CopingIII.Attachments

I. NONCOPING OVERDENTURES:Selected abutments are reduced to a coronal height of 2 to 3 mm and then contoured to a convex or dome shaped surface. Most teeth require endodontic therapy followed by amalgam or composite restoration.


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II.COPING OVERDENTURES:

Coping TypesA coping fitted to a prepared abutment is called a primary coping. The sleeve, or coping, that fits over this primary coping is referred to as a secondary coping.There are four basic types of primary copings:1. Long copings (6-8 mm).2. Medium copings (4-6mm).3. Medium-short copings (2-4 mm).4. Short copings (1-2 mm).


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1. Long Copings (6-8 millimeters for vital teeth):


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2. Medium Copings (4-6 millimeters for vital and non-vital teeth):


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Abutment preparations for medium copings

Medium copings


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With bar attachments To engage plunger

Studs cantilevered


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3. Medium short copings (2-4 mm for nonvital teeth):


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4. Short Copings (1-2 millimeters for non-vital teeth):


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III. Overdenture with Attachments:

The attachments essentially increase the crown-root ratio and then torque. Or apply horizontal or vertical dislodging forces to the root abutments. Here, low caries index, proper home care, periodontal health and inter ridge distance are absolutely necessary.


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TELESCOPE CROWNS:The telescope crown is a prosthodontic retainer for a fixed or removable prosthesis and usually consists of the conical preparations with a like casting and a secondary telescope casting that is embedded in a prosthesis or is an abutment or crown itself. It is a system used to stabilize an overdenture where 4 mm or more of clinical crown is available. The advantage of the telescope crown or telescope preparation over the standard overdenture is the increased stabilization and retention of the denture while using remaining vital or nonvital teeth without dowels or screws.


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TELESCOPE OVERDENTURE:

The telescoped overdenture is an excellent alternative to routine complete dentures. As the name implies, a telescoped overdenture fits over natural teeth with that portion of the overdenture fitting like a sleeve. These supporting abutments may simply be endodontically treated teeth reduced slightly, shaped, smoothed, polished and left in this manner to support this denture; or, these roots or teeth may be restored with metal copings. The size of these primary copings, the copings on the teeth, may be medium or long. They may be designed only to provide support, or to provide support and retention.


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Advantages:1. Conserve the alveolar ridge2. Provide support and often retention 3. Retains some natural proprioception4. Emotionally accept the overdenture 5. Easy modification possible 6. Auxiliary retention devices can be added 7. Easy to master 8. Less expensive than attachment fixation

overdenturesDisadvantages:1. Retention is fixed, and not variable2. Retention must be modified frequently 3. The overdenture is bulky and less esthetic 4. Expensive than a conventional complete denturewww.indiandentalacademy.com

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ATTACHMENTS CAN BE CLASSIFIED ACCORDING TO SHAPE, DESIGN, AND PRIMARY AREA OF USE AS FOLLOWS: (Mensor)

Coronal1. Intracoronal attachments2. Extracoronal attachments

Radicular3. Telescope stud attachments (pressure buttons) 4. Bar attachmentsa. Jointsb. Units www.indiandentalacademy.com

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Accessory

5. Auxiliary attachmentsa. Screw unitsb. Pawl connectorsc. Boltsd. Stabilizers/balancerse. Interlocksf. Pins/screwsg. Rests


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The Gerber Attachment The Gerber stud system is a versatile stud attachment used routinely. It consists of a male post soldered to the coping and a retentive female secured within the denture base of the overlay prostheses. The Gerber attachment is furnished in two different types - a resilient and non-resilient form.

Resilient Gerber Non resilient Gerber www.indiandentalacademy.com

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The male post consists of two parts - a threaded base, which is soldered to the diaphragm of a coping, and a removable sleeve with a retentive undercut

The resilient female consists of a housing, coiled spring, C-spring, a retention sleeve and lock screw. The non-resilient female has a female housing, C spring and a screw cap and no copper shim and coil spring.


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Dalla Bona AttachmentThe Dalla Bona is a simple stud attachment making an

excellent overdenture attachment available in a resilient or nonresilient series. It is useful when there is minimal vertical space and where rotation, resilience and retention are desired. It consists of a single piece

male stud soldered to the coping and a single unit female processed within the denture. It is available in

two types: 1.Cylindrical 2.Spherical

One form even has an internal coiled spring much like the resilient Gerber. This spring helps control vertical

movement. The Dalla Bona series is an excellent attachment.


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Dalla bona attachments on two cuspids makes it excellent overdenture arrangement

Spherical Bona with undercut for retention


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Male is a solid stud, female is a single component with retentive lamellae. A clear Teflon ring covers the female lamellae

Restored roots with copings and spherical bonas


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Cylindrical Dalla BonaThe cylindrical male post has parallel walls

without an undercut. The female lamella fits

snugly over the male posts, providing frictional

retention. A PVC ring fits around the female

lamellae. This aids in fabrication, and permits

the lamellae to flex. The cylindrical Dalla Bona

must be parallel; therefore, the male posts

must be assembled using a paralleling

mandrel and surveyor.www.indiandentalacademy.com

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Spherical Dalla BonaThe spherical Dalla Bona is similar to the cylindrical, but the male post is spherical. This sphere provides a retentive undercut which is engaged by the retentive lamellae of the female. If a spacer is used during fabrication, this attachment will be resilient; without the spacer, it will be nonresilient.


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The Rotherman AttachmentThe Rotherman is another excellent stud attachment.

The Rotherman consists of a solid stud (that is soldered to the coping) and a clasp like female (that is mounted in the overdenture. Like many stud attachments, it is available in both resilient and nonresilient designs. The resilient form

has a taller male and is supplied with special spacers.The Rotherman is particularly applicable where

interocclusal space is limited, as the nonresilient design has a vertical dimension of just 1.1 millimeter and the

resilient just 1.7 millimeter.


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BAR ATTACHMENTSAs the name suggests, bar attachments consist of a metal bar that splints two or more abutments and a companion mechanism processed within the tissue area of the overdenture. This mechanism snaps on the bar to retain the prosthesis.Bar attachments are available commercially in a wide variety of forms or they can easily be "custom" fabricated.


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Types of Bar Attachments

Bar units

Bar joints


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The Bar UnitThis bar has parallel walls providing rigid fixation

with frictional retention. It can be used for retention with long, medium or short copings, but

only when the appliance is to be an all tooth supported appliance (i.e. where no stressbroken or rotational action is indicated). It is never used when a bar joint is indicated (when rotational or

vertical action is necessary); however, a bar joint can be used whenever a bar unit is indicated.


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The Bar JointThe action of this attachment provides rotational or

vertical movement. In other words, it is a stress broken attachment. It has a rounded or semi

rounded contour so the retention clip and prosthesis can rotate slightly during mastication.


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The Dolder BarAn ideal bar attachment is the Dolder bar. It is well

designed for splinting two or more abutments to provide support, stability and retention for the

overdenture.This bar attachment is manufactured in two forms a bar joint and a bar unit. It is also available in two

different diameters and lengths.


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Dolder bar joint

The pear shaped bar joint is designed to provide vertical and rotational action so it is indicated where a stress-broken,

resilient attachment is desired. It can also be used as a bar unit for an all tooth supported prosthesis by fabricating the

overdenture without planned vertical movement.

Dolder bar unit

The bar unit is in the form of an inverted U with parallel walls. It does not permit

rotational or vertical movement; therefore it only

provides retention and support, but maximizes the

masticatory load on the abutments.


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The Hader Bar SystemThe Hader system is an excellent bar attachment. Similar to the customized bar, the Hader system

consists of a plastic bar pattern with gingival extension and small plastic clips that are

processed into the overdenture. This system has some advantages over others; the plastic bar pattern's gingival extension can be trimmed to

conform to the ridge. In addition, worn clips can be easily replaced at chair side using a special

seating tool.


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AUXILLARY ATTACHMENTS

In addition to bars and studs, other attachment systems are applicable for overdenture

prostheses. These auxiliary attachments may be in the form of screws or spring loaded plunger

attachments.


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overdentures / orthodontic straight wire technique

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