balanced occlusion

Arranging prosthetic teeth and occlusion for the edentulous

patientBy:

Dr. Sayyed Masoud BayanzadehAssistant professor of Tehran university

Types of posterior teeth1. An anatomic tooth is one that is designed to simulate the

natural tooth form. The standard anatomic tooth has inclines of approximately 33 degree or more.

2. when the cusp incline is less steep than the conventional anatomic tooth of 33 degree it can be classified as a modified or semianatomic tooth. It can be considered basically anatomic and will articulate in three dimensions.

3. A nonanatomic tooth is essentially flat and has no cusp heights to interdigitate with an opposing tooth and has sulci to enhance its comminuting effect on food. They articulate in only two dimensions.

Many factors enter into the arrangement of the Artificial teeth in a denture. They act as a unit;And attached to a movable base resting on movable and displaceable living tissue, which are subject to damage; therefore, they must beArranged to function as a unit. However, Leverages, forces, vector of forces, discrepanciesin residual ridges, maxillomandibular Relationships, residual ridge relationships,Functional and parafunctional mandibular Movements, and preferences of patients vary.

The arrangement of teeth must be Physiologically And esthetically acceptable. Physiologically,They must be in a positioncompatible with the lips,Tongue, and cheekswhether the mandible is in a Relaxed position

or in motion.

Factors governing the position of teeth

1. The functions of the surrounding structures,

2. The cellular structure to the basal seat tissues,

3. The anatomic limits, and4. The mechanical aspects.

Factors governing the position of teeth for complete dentures

I. The horizontal relations to the residual ridges,

II. The vertical positions of the occlusal surfaces and incisal edges between the residual ridges,

III. The esthetic requirements, andIV. The inclinations for occlusion.

Horizontal positions 1• Involves placing the teeth anteroposteriorly

and mediolaterally (1) to provide stability, (2) to direct the forces of mastication to areas most favorable for support, (3) to support the lips and cheeks for esthetics, and (4) to be compatible with the functions of the surrounding structures.

Horizontal positions 2• Forces directed at right angles to the

supporting tissues are more stabilizing than forces directed at an inclined plane. Protrusive and lateral movements involving tooth contacts result in forces directed toward inclined planes, and these forces are capable of dislodging the dentures. Therefore many patients may change their habitual jaw movements to a more vertical closure.

Horizontal positions 3• This adjustment may not happen with

patients who have a low pain threshold. The dentist cannot always differentiate these patients. Therefore, all patients are instructed to crush their food by closing up and down and not from side to side and cut food into small pieces with the knife and fork.

• The forces of mastication should not be directed to tissue incapable of withstanding the force.

Arranging the artificial teeth for the trial denture 1

• Teeth are tried in before processing them in acrylic resin (1) to verify the maxillomandibular records that were made without teeth (tentative records),(2) to test for the acceptance of the established vertical dimension of occlusion,(3) to determine if the positions of the teeth and the contours of the denture base are compatible with the surrounding oral environment ,(4) to evaluate the arrangement for esthetic requirements, and(5) to make additional interocclusal maxillomandibular records if needed for further adjustment of the articulator.

Arranging the artificial teeth for the trial denture 2

• The anterior teeth are arranged in basic positions, principally for esthetics. The posterior teeth are arranged in maximum planned intercuspation (cusp form) or occlusal contact (noncusp form) on a plane.

Arranging the posterior teeth 3• In general, for developing the anterior plane of

occlusion, the plane should be located either at or slightly below the corners of the mouth. The position of the incisal edges of the mandibular anterior teeth eventually establishes the level of the anterior plane of occlusion. The posterior plane of occlusion is an extension of this anterior plane level with the junction between the middle and upper third of the retromolar pads bilaterally.

Arranging the posterior teeth 4

• These posterior references (retromolar pads) will place the overall plane at a level that is familiar to the tongue (2-3 mm below the dorsum of the tongue). If the plane located higher or lower, will interfere with normal tongue action.


• If the plane is too low in the anterior region or too high in the posterior region

• The buccolingual position of the posterior teeth and the posterior arch form are determined anteriorly by the position of the canine and posteriorly by the shape of the basal seat and the location of the retromolar pads.


• The posterior teeth are positioned in such a way that they are properly related to the bone that supports them and to the soft tissues that contact their facial and lingual surfaces. The posterior form of the arch will be determined largely by the “neutral zone”between the cheeks and tongue?


• The basic principle for the buccolingual positioning of posterior teeth is that they should be positioned over the residual ridge.

• The tip of the canine to the middle of the retromolar pad should provide guides for this arrangement.

Arranging the posterior teeth 7The mandibular posterior teeth are arranged first because of:

1- there are more anatomic landmarks to locate the guide lines in the mandibular arch.

2- the lingual surfaces of the mandibular posterior teeth are not placed more in a medial direction than is the medial surface of the lingual flange of the denture base.

3- the mandibular canines are the turning points in the arch.

4- the retromolar pad is used to determine the vertical height of the mandibular molars.

Occlusal schemes for complete denture occlusion

• The occlusal scheme or the tooth molds selected for occlusal rehabilitation will depend on the concept of occlusion that has been selected to satisfy the need of the patient. Chewing efficiency tests have shown a slight advantage to cusped teeth.

Factors that affect occlusal balance

1. Condylar guidance2. Incisal guidance3. The plane of occlusion is established by the height of

the lower cuspid and in the posterior by the height of the retromolar pad. It is also related to the ala-tragus line, or camper’s line.

4. The compensating curve5. Cusps on teeth or the inclination of

cuspless teeth.

Concepts of the complete dentures occlusion 1

1. Bilateral balance,2. Monoplane or nonanatomical, and3. Lingualized articulations.Anatomical molds usually are selected for

bilateral balanced articulationNonanatomical teeth can be used in a

balanced concept with the use of compensating curves.

Concepts of the complete denture occlusion 2

• Nonanatomical or cuspless teeth are generally the choice for monoplane articulation, although teeth with cusps also can be used. For the lingualized occlusal concept, a combination of upper anatomical and lower nonanatomical molds has been introduced.

Indications of the monoplane occlusion

1) Flat ridge(s)2) Class 23) Class 34) Maxillofacial

patients5) Handicapped

patients

6) Cross bite7) Doubtful or Without

any perfect centric relation records

Arranging anatomical teeth to a balanced articulation

• The anterior teeth are set with a minimal vertical overlap of 0.5 to 1 to 2 mm of horizontal overlap to establish a low incisal guidance.

Number of posterior teeth set

• Decision on the number of teeth to use will depend on the available space for posterior teeth from the distal of the canine to the retromolar pad or the ascending incline forward the retromolar pad. If only three teeth are to be arranged, it is more convenient to drop the first premolar.

Setting the mandibular teeth first 1

• The facial surface of the premolars should be perpendicular to the occlusion rim.the long axis of the two premolars is positioned so that the cusp tips are level with the remaining mandibular wax occlusal rim. Then the upper first premolar should be positioned. These three teeth must be adjusted in their places because they are the key to the relative anteroposterior intercuspation of all the remaining posterior teeth.

Setting the mandibular teeth first 2

• In the positioning of the mandibular first molar, the central groove is placed on the canine to retromolar pad references line. The vertical height of the tooth is adjusted by positioning the cusp tips on the occlusal plane……..

Setting the lower teeth first is perhaps A little easier for two reasons:1- The teeth can be set over the moreImportant lower ridge directly2- The relation of the compensating Curve to the condylar and incisal Guides can easily be seen because The lower cast is directly attached to That part of the instrument which Carries these guides.

Setting the maxillary teeth first

• In arranging the maxillary posterior teeth first, start with the maxillary first premolar. After the two premolars and the first molar are placed, it is better to be placed the first molar to correct positioning of the posterior teeth (buccolingually- anteroposteriorly).

• The premolars palatal cusp tips and mesiopalatal cusp tip of the first molar must contact the mandibular occlusion rim.

Relating inclinations of teeth to concepts of occlusion 1

• When discussing the inclinations of the teeth for complete dentures, one must consider the concepts of different occlusal schemes. The neutrocentric concept using noncusp form posterior teeth arranged on a plane, the balanced occlusion concept using noncusp form posterior teeth arranged on a plane, the balanced occlusion concept using cusp form posterior teeth arranged in balance in the centric and eccentric jaw positions, and the lingualized occlusal concept, which can combine components of both of these occlusal schemes.

Relating inclinations …. 2

• Balanced occlusion is based primarily on the premise that stability is provided mechanically to the denture bases on their basal seats. When the teeth are brought together at any relationship of the jaws, at least a tripod type of contacting of the teeth provides stability to the bases.

Relating inclinations…. 3

• The neutrocentric arrangement of the teeth on a plane (flat) parallel with the bony support is based primarily physiologic principles that involve the influence of the somatic nervous system in control of muscle movement and proprioception. The mechanism involves the teeth making contact when the condyles are in a comfortable, stable position in the fossae and the denture bases are stable and comfortably seated on the basal seats. The arrangement of teeth on a flat plane does not provide stability in eccentric relationships.

Relating inclinations…. 4• When the teeth contact on unstable bases, the

condyles are not in a stable position, result is discomfort. The somatic nervous system-the receptors in and around the joints, in the periosteum, and in the mucosa of the lips, tongue, and cheeks-notifies the central nervous system of the discomfort. It is notifying the central nervous system to modify the muscle pattern until comfort is established. The muscles is programmed to make a jaw closure to tooth contact when the condyles are terminally related in the fossa.

Relating inclinations…. 5

• DeVan stated this thusly, “the patient will become a chopper, not a chewer or grinder.”

• Arranging monoplane teeth in balanced occlusion provides a long inclined plane, a long cusp.

• The lingualized occlusion concepts represents a compromise between the concepts of balanced and neutrocentric occlusion.

Relating relations…. 6

• The concept of spheric occlusion involves the position of the teeth with anteroposterior and mediolateral inclines in harmony with a spherical surface.

• The concept of organic occlusion calls for altering the shape of the cusps of the teeth to provide prosthetic teeth that have cusps suitable for the individual patient.

Neutrocentric concept 1

• This term is used to denote a concept of occlusion that eliminates any anteroposterior or mediolateral inclines of the teeth and directs the forces of occlusion to the posterior teeth. The plane of occlusion should not be dictated by the horizontal condylar guidance and must be flat and the form of the posterior teeth is devoid of cusp. The horizontal and lateral condylar guidance may be set at zero.

Neutrocentric concept 2

• The direct force toward the center of the support and to reduce the frictional forces, the buccolingual width of the teeth is reduced and the number of teeth is reduced to direct the forces in the molar and bicuspid area of support and to refrain from placing a tooth on the ridge incline in the second molar area

Balanced occlusion 1

• The concept of centralizing the working occlusal surfaces requires bringing the occlusal surfaces toward the center of the denture foundation to their ideal positions for favorable leverage ( anteroposteriorly, is the area of the premolars and the first molars and mediolaterally, most favorable leverage obtained when the occlusal working surfaces are placed to the lingual sides of the ridge crests.


• Sufficient simultaneous contacts will take place in the three areas of the arches to exert a stabilizing force sufficient to prevent dislodging the denture. When a cusp form posterior tooth is used, it is necessary to develop balanced occlusion. If premature tooth contacts occur in gliding occlusion, they are evaluated in the mouth and removed by grinding the offending tooth or teeth.

Balanced occlusion 3• To adjust the articulator requires (1) a centric

relation record and (2) an eccentric protrusive record. Right and left lateral relation records are desirable if the articulator is capable of accurately accepting and being adjusted to the records. If the articulator will not receive the lateral records and is a Hanau type, use the formula suggested by Hanau to adjust the lateral condylar guidance:

• HL = -- + 12.

8

Balanced occlusion 4• When the accuracy of the centric relation

record has been verified, the vertical dimension of occlusion has been accepted for esthetic purposes, the protrusive relation record is made and the articulator is adjusted for condylar guidance.to balance the occlusion, the teeth are inclined to harmonize with the three controlling end factors, the right and left condylar inclinations, and the incisal guidance.


• Condyle paths are peculiar to each individual, and the dentist has no control over horizontal or lateral inclinations. The term incisal guidance refers to the influence on mandibular movements of the lingual surfaces of the maxillary anterior teeth. In complete denture construction, the dentist has control over the vertical incisal guidance and The lateral incisal guide angle.


• It is desirable to arrange the anterior teeth with a vertical and horizontal overlap with an incisal guide angle of near 0 degree. This positioning of the teeth reduces the inclines in a mediolateral and anteroposterior direction. Forces directed at inclines are more dislodging than forces directed at right angles to the support.

• It is desirable to arrange the anterior teeth with a vertical and horizontal overlap with an incisal guide angle of near 0 degree. This positioning of the teeth reduces the inclines in a mediolateral and anteroposterior direction. Forces directed at inclines are more dislodging than forces directed at right angles to the support.

Lingualized occlusion 1

• Encompassing balanced, nonbalanced, linear, functional, functional rotational, and organic occlusions.

• Lingualized occlusion is limited here to one where the maxillary lingual cusps are the main functional occlusal elements. These may oppose mandibular 0 degree or shallow cusp teeth in balanced or nonbalanced patterns depending on the needs for the patient.

Lingualized occlusion 2• The use of maxillary lingual cusps could be

expected to centralize the occlusal forces and reduce the frictional resistance of flat teeth sliding over one another. Additional stability can be gained during parafunctional movements if a series of surfaces is used that allows for occlusal balance and an area (rather than a point) of closure. Lingualized occlusal scheme can be used in which anatomic teeth are used in balanced occlusion or where o degree teeth are applied in neutrocentric or monoplane occlusal schemes.

C lingualized occlusion and D working position of This type occlusion

Evaluating bilateral balanced articulation

• This position can be inspected after all the maxillary and mandibular teeth have been arranged. The lateral movement of the articulator should be minimal, usually bringing the maxillary and mandibular canines into an end-to-end relation to each other will suffice.

Arranging nonanatomical mandibular posterior teeth to

balanced articulation• Number of posterior teeth set most often, the

number of posterior teeth used in balanced articulation with nonanatomical teeth will be limited to three. Therefore it often is necessary to position the two the two molars slightly to the facial.

• Anteroposterior compensating curve this curve begins at the distal marginal ridge of the first posterior tooth (which is usually the second premolar) and continue through the second molar. The degree of this curve is usually below 20.

Arranging nonanatomical mandibular ……..

• Mediolateral compensating curve this curve also is needed to provide the needed tooth structure to achieve balanced articulation during lateral movements. This curve is initiated with the first replacement tooth and continues through the second molar. The degree of this curve will vary with the condylar and incisal guidances.the curve usually does not exceed 5 to 10degrees from the horizontal plane of orientation.

Arranging nonanatomical maxillary posterior teeth to

balanced articulation

• First premolar for most patients, only three maxillary posterior teeth will be used. The first premolar will be used because of its longer occlusal cervical height, which provides a more esthetic arrangement. A sufficient overjet must be provided.

Arranging nonanatomical teeth to monoplane articulation

• With this concept of occlusion, there is no attempt to eliminate deflective occlusal contacts in lateral or protrusive excursions. When the nonanatomical teeth are arranged to satisfy the monoplane occlusal concept, the condylar inclinations on the articular are set at 0 degrees. When the positioning of the maxillary posterior teeth completed, the occlusal surfaces of them should be flat against the mandibular wax occlusal rim.

The inclination of the teeth and the compensatingcurve are of more importance to balance than is the Inclination of the occlusal plane.The average denture patient may make many toothcontacts during the hours between meals. They Are light fleeting contacts which would not Seriously test denture retention. If this is true,Then balance as an aid in retention is probablyUnnecessary for the most patients. But manypatients enjoy comfort only when eccentric balance Is present.

Occlusal modifications and the selective reshaping process

Establishing maximum intercuspation 1

• Once maximum intercuspation is achieved, balanced articulation in the several eccentric movements may be attained in the mouth.

• Premature contacts most often are at the central fossae or marginal ridges of the lower teeth and on the lingual inclines of the maxillary facial cusps. Continue marking the contacts and reshaping the teeth until all maxillary lingual cusps demonstrate maximum intercuspation with their mandibular antagonists.

Establishing maximum intercuspation 2

• Remember this procedure is one that establishes the maxillary lingual cusp as the main supporting cusp in the occlusal contact pattern.

Adjusting the working and balancing contacts 1

• Working side interferences will result from contact between the lingual inclines of the maxillary facial cusps and the facial inclinesof the facial cusp of the mandibular tooth in lateral excursions.


• Balancing side interferences will occur between the lingual cusps of the maxillary teeth as they move across the lingual inclines of the facial cusps of the mandibular teeth in lateral excursions. Balancing contacts are the direct result of the compensating curves being out of harmony with the lingual cusps.


• Balancing interferences and maximum intercuspation contacts may occur very near to each other on the occlusal surfaces of the mandibular teeth. The maximum intercuspation stop is generally in the central portion of the tooth, whereas balancing contact marking may be very small and begin in the same area and move in a distal facial direction onto the lingual inclines of the mandibular facial cusps.


• If the balancing contact must be reduced, it will be only the facial portion of the mandibular marking that is altered. Selective grinding of the entire contact area will result in the loss of maximum intercuspation.

Adjusting the protrusive contacts

• Protrusive contacts result from the maxillary lingual cusps gliding over the distal lingual “cusp” of the mandibular tooth in a straight protrusive movement. And also may appear between the lingual inclines of the maxillary facial cusps and the facial inclines of the mandibular facial cusps. Contacts may be eliminated by grinding on the mandibular facial cusp.

C Anti Monson curveD Pleasure curve first premolars ( anti Manson)- secondpremolars (anti Manson)- first molars (monoplane occlusion)

And second molars (Manson)