Occlusion in Complete Denture

جامعة الموصل
كلية طب الاسنان/ فرع صناعة الاسنان Lec.: Mohammed A. Abdulla
المرحلة الرابعة/ صناعة اسنان

Occlusion in Complete Denture

Definition: the relationship between the occlusal surfaces of the maxillary and mandibular teeth when they are in contact. It is a static position when the jaws are centrically or eccentrically related .
Objectives:
Should provide for maximum intercuspation of the teeth with condyles in centric relation.
should provide for horizontal movement of mandible from the centric related intercuspal position.
Should be designed to facilitate chewing efficiency, stability, retention of the denture, and comfortable for the patient.
Should not traumatize the oral supporting structures , and preserve the alveolar bone and soft tissue.
Classification:
Based on occlusal relation ship of posterior teeth. Angle classified occlusion as follows:
Class I
The mesiobuccal cusp of the mandibular first molar occludes in the embrassure area between the maxillary second premolar and first molar.
The mesiobuccal cusp of the maxillary first molar falls in the buccal groove of the mandibular first molar.
The mesiobuccal cusp of the maxillary first molar is situated in the central fossa area of the mandibular first molar.


Class II
The mesiobuccal cusp of the mandibular first molar is situated in the central fossa area of the maxillary first molar.
The distobuccal cusp of the maxillary first molar falls in the buccal groove of the mandibular first molar.
The distolingual cusp of the maxillary first molar is occludes in the central fossa area of the mandibular first molar.

Class III

The distobuccal cusp of the mandibular first molar is situated in the embrassure area between the maxillary second molar and maxillary first molar.
The mesiobuccal cusp of the maxillary first molar occludes in the embrassure between the mandibular first and second molars.
The mesiobuccal cusp of the maxillary first molar is occludes in the mesial pit of the mandibular second molar.

Theories of occlusion:

Bonwills theory of occlusion:
According to this theory, the teeth move in relation to each other as guided by the condylar and the incisal guidances. The distance between the condyles is equal to the distance between the condyle and the midpoint of the mandibular incisors.

Conical theory of occlusion:

According to this theory, mandibular teeth move over the surface of the maxillary teeth as over a surface of a cone generating an angle of 45 degree with occlusal plane.




Spherical theory of occlusion:
According to this theory, mandibular teeth move over the surface of the maxillary teeth as over a surface of sphere (over the glenoid fossa and articular eminence) with a diameter of 8 inches (20cmm)

Types of occlusion in natural dentition:

Bilaterally balanced occlusion:
In this type of occlusion there is bilateral, simultaneous, anterior and posterior occlusal contact of teeth in centric and all eccentric positions. This type of occlusion occur in few people.

Canine guided occlusion:

the vertical and horizontal overlap of the canine teeth opening the posterior teeth in the excursive movements of the mandible.

Group function:

There is unilateral, anterior and posterior occlusal contact of teeth in lateral movements on the working side to which mandible moves.

Mutually protected occlusion:

It is occur most commonly in natural dentition in which one or group of teeth protected the other teeth during various mandibular movements.

Types of occlusal concepts in complete denture occlusion

Balanced occlusion
Definition: is the bilateral, simultaneous, anterior and posterior occlusal contact of teeth in centric and eccentric positions.
Aim:
In the case of balanced occlusion, is to achieve even contacts between all maxillary and mandibular teeth on the working side ( the side which the mandible moves) during lateral movements. At the same time, there should be multiple contacts between the mandibular and maxillary teeth on the balancing side (i.e. the side from which mandible moves)

Advantages:

Enhance retention and stability of complete denture.
Forces are distributed equally all over the denture bearing area resulting in reduced resorption of alveolar bone.
Patient is more comfortable in performing various mandibular movements.

Disadvantages:

Increases horizontal force
Difficult to adapt to abnormal jaw relation


Factors affecting balanced occlusion
According to Hanau, there are five factors which affect the balanced occlusion , - Condylar guidance
Is define as mandibular guidance generated by condyle and articular disc traversing the contour of the glenoid fossa. Condylar path should be determined on the patient and set on the instrument so that the patients TMJ is in harmony with the occlusion as recorded in articulator.
Horizontal Condylar guidance of patient is programmed in the articulator with the help of protrusive jaw relation records.
Lateral Condylar guidance of patient is programmed in the articulator with the help of lateral jaw relation records or by using Hanau's formula in the case of Hanau articulator:
Hanau's formula L = H + 12
8
L= lateral Condylar guidance
H= horizontal inclination
Incisal guidance
Is the influence of the contacting surfaces of mandibular and maxillary anterior teeth during mandibular movements. It is usually expressed in degree of angulations from the horizontal by a line drawn in the sagittal plane between the incisal edges of upper and lower incisor teeth when closed in centric occlusion (incisal guidance angle) . For increasing stability of the complete denture less vertical over lap and horizontal over lap during arrangement of anterior teeth result in shallow incisal guidance angle.
Plane of occlusion
It is the average plane established by the incisal and occlusal surfaces of the teeth. In complete denture fabrication, plane of occlusion should be parallel to alatragus line and inter pupil line.
Cuspal inclination
It is the angle by the average slope of a cusp with the cusp plane measured mesiodistally or buccolingually. It modify the effect of the plane of occlusion and compensatory curves.
Compensatory curve
It define as the anteroposterior curvature ( in the median plane) and the mesiolateral curvature in the frontal plane in the alignment of the occluding surfaces and incisal edges of the artificial teeth that are used to develop balanced occlusion.
The compensatory curve called this ; because they compensate for the space formed between the upper and lower occlusal surfaces of posterior teeth during protrusive and lateral movements of the mandible. That is compensate for the Christensen's phenomenon occurring in natural dentition, so that upper and lower occlusal surfaces of posterior teeth occlude with each other and there is no any space between them during protrusive and lateral movements of mandible( providing stability and balanced occlusion for dentures).




Mono plane occlusion
Cuspless teeth set on a flat plane with 1.5-2 mm over jet.
No cusp fossa relation
No anterior contacts present in centric position
No over bit

Lingualized occlusion

Lingual cusp contacts opposing fossa
Mandibular cuspal inclines are shallow (0-10) degree
Less lateral displacement

Curves in artificial dentition:

Anterio-posterior compensating curve or curve of Spee
It deigns at the distal marginal ridge of the first posterior replacement tooth (which is usually the second premolar) and continues through the second molar. The amount of curvature developed is dependent on the steepness of the Condylar guidance.


Curve of Spee

b- Medio-lateral compensating curve

It is needed to provide the needed tooth structure during lateral movements of mandible. It compensates for the wedge-like opening formed when the mandible is moved laterally to the opposite side.

Compensating curve for Monson curve

This curve runs across the buccal and palatal cusps of maxillary molars.
The artificial teeth should be set following this curve in order to obtain lateral balance of occlusion

Compensating curve for curve of Wilson

This curve is obtained by tilting the maxillary molar such that the buccal cusps are higher than the palatal cusps, the mandibular molars are tilted lingually which results in lateral balance of occlusion.
This curve runs opposite to the direction of Monson curve and hence also called as anti-Monson curve.