occlusion

COMPLETE DENTURE OCCLUSION

Dr. Monia MN Kandil
Balanced Occlusion and Articulation

Bilateral simultaneous occlusal contact of teeth, anteriorly and posteriorly, in both centric and eccentric positions.
Gliding of the teeth across each other during their movement from one position to another, without any interferences.

3- Increased efficiency of mastication.

1- Provide maximum denture stability during functional and parafunctional movements of the mandible.
2- Help in distribution of the masticatory pressure over the supporting tissues and reduce trauma to the underlying tissues.
4- Psychologically it is more comfortable to the patients who enjoy comfort and satisfaction only when eccentric balance is present.

achieving  Stable and physiologic occlusion. 1- Balance in centric

stability of complete dentures are well served by the freedom in centric (long centric) concept

There should be working and balancing side contacts, or

At least There a minimum of three-point contact between the lower centrals and posterior teeth on each side.
2- Balance in eccentric Occl.
During lateral excursions:

Teeth make contact in lateral excursion on the working and balancing sides

Excursive Movements
Laterotrusive and Mediotrusive
Non-working Side (Mediotrusive)
Working Side (Laterotrusive)
LEFT MANDIBULAR EXCURSION

2- Balance in eccentric Occl.

During protrosive excursions:
It should be at least three-point contact between the teeth on each arch one anterior and 2 posteriors.
If with anatomic teeth arrangments  follow compensating curves.

If with non-anatomic teeth, should use for example:

Tilting the second molar   Using balancing rump Reverse curve of Wilson 

Factors affecting occlusal balance

The condylar guidance The incisal guidance The inclination of plane of occlusion The compensating curve and cusp angle of teeth


A, Inclination of the condylar guidance. B, Prominence of the compensating curve C, Plane of orientation D, Height of the cusp E, Inclination of the I.G


Translation occurs when the mandible moves into a protrusive or lateral position, or a combination of the two Rotation occurs when the mandible makes a hinged movement.
The movements of the condyle in the glenoid fossa are either translation or rotation

No Translation

A- Rotation occurs when the head of the condyle rotates around an imaginary axis

Translation

B. Translation is the bodily movement of the head of the condyle

A- Rotation occurs when the head of the condyle rotates around an imaginary axis

B. Translation is the bodily movement of the head of the condyle


Condylar inclination is the angle formed by the steepness of the articular surface of the temporal bone as related to a horizontal line.
The condylar guidance: refers to the path of the condyle follows in the temporomandibular joint when the mandible moves into protrusive or lateral movements
1. The condylar guidance



The shape of the glenoid fossa. The variation of the thickness of the articular disc in its different parts. The relation of the condyle to the disc during movement. The extent of mandibular protrusion
The inclination of the condylar paths varies in different individuals and from side to side in the same person. It depends upon

The condylar guidance is the only factor given by the patient.

Bennett Angle
The angle formed by the sagittal plane (assumed straight protrusive path) and the path of the advancing (orbiting) condyle during lateral mandibular , when the movements as viewed in the horizontal plane.


The Condyler guidance (C.G.) of articulator is an appropriated duplication of the C.G. in the patient and is obtained by means of a protrusive record. So that the patient's temporomandibular joint is in harmony with the occlusion as programmed on the articulator

The incisal guidance It is the path taken by the lower anterior teeth as it move in a protrusive movements against the palatal surface of upper anteriors, till become edge to edge.
2-The incisal guidance


A) Anatomically: 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
The incisal angle



Incisal guide angle: B) On an articulator: That angle formed in the sagittal plane, between the plane of reference and the slope of the anterior guide table, as viewed in the sagittal plane

The incisal guide angle can be controlled when developing a balanced occlusion. With a given amount of vertical overlap (VO) the incisal guide angle can be made flatter by increasing the horizontal overlap (HO)

It can also be made less steep by reducing VO

A. Steep incisal guidance
B. Medium incisal guidance
C. Zero incisal guidance
B
Inc.G should be either equal to or less than Condy.G. Inc.G should not never be greater than Cndy. G.


Steep I.G. calls for steep cusps, steep O.P. or a steep C.C. to effect an occlusal balance. This type of occlusion results in harmful inclined planes with their harmful risk to the supporting tissues
Inc.G. can be set by the dentist according to esthetics and phonetics requirements.

Condylar guidance

Incisal guidance
Occlusal Plane
Cusp Height
Compensating curve
More controllable



Occl. P. is an imaginary plane formed by lines connecting tips of incisor teeth and disto-buccal cusps of the most posterior teeth on each side of arch
3- The Plane of Occlusion (Plane of Orientations)

Anterior and Posterior occlusal plane

Parallel to interpupillary line.
Parallel to the ala tragus line.

Occl.P. At (a) is the ala-tragus plane obtained from the patient. At (b) is a compromise plane midway between ridges. At (c) is a low plane necessary to favor weak lower ridges

The Plane of Occlusion

The orientation of the occlusal plane becomes a fixed factor of occlusion
Any necessary alteration for balancing the occlusion must therefore be made on other factors affecting the occlusion (that is, the cuspal inclination or the prominence of the compensating curve)


1- Aesthetic base 2- Functional base (chewing and speech) 3- Physical and mechanical (leverage action and parallelism).
Factors must be considered:
Determination of the occlusal plane

Determination of the occlusal plane

The Height Of Occlusal Plane Should Be 1-2 Mm. Below The Upper Lip. Anteriorly Is Influenced By: The Length Of The Lip, Ridge Fullness, Ridge Height, The Amount Of The Maxillomandibular Space And The Incisal Guide Angle.
Aesthetic base.


Chewing The height of occlusal plane should be convenient and at a level familiar to the tongue to perform its action easily and stop food escaping to the floor of the mouth.
The occlusal surface of the teeth should be below the greatest convexity of the tongue. This also improves the stability of lower denture.
Functional base (chewing and speech)


Speech: During speech, the tongue pushes against the sides of the teeth to produce a seal for better pronunciation of words.
Functional base (chewing and speech)

Leverage action Parallelism 3) Arch form

Principle of Physics and Mechanics
The amount of leverage or torque exerted on the occlusal plane is a function of the height of the plane above the ridge. Torque X = force (f) x Distance from fulcrum (R).

1) Leverage action: The nearer the occlusal plane to the basal bone of the jaws, the less the leverage action and the better the stability.
Principle of Physics and Mechanics



2) Parallellism: The occlusal plane should be parallel to both supporting ridges. In this way the biting forces are vertical on the ridges and there is no tendency for horizontal displacement of the dentures.
Effect of occlusal plane orientation on denture stability
Principle of Physics and Mechanics

3) Arch form

Both the width of the occluding surfaces and the contour of the arch form of the occlusion rims should be individually established to simulate the desired arch form of artificial teeth
Principle of Physics and Mechanics


1- Spee’s curve The anatomic curvature of the occlusal alignment of the lower teeth beginning at the tip of the lower cuspid and following the buccal cusps of the natural bicuspids and molars continuing to the anterior border of the ramus
4- Compensating curves


The buccal cusps of the lower posterior teeth are slightly higher than the lingual cusps, and a line drawn through the buccal and lingual cusps of the teeth on the other side forms a lateral curve called the curve of Wilson
2- Wilson’s curve

the curve of occlusion in which each cusp and incisal edge of upper and lower teeth of right and left sides touches or conforms to a segment of the surface of a sphere eight inches in diameter, its center in the region of the Glabella
3- Monson’s curve


The compensating curve of the artificial occlusion corresponds to a combination of these curves in natural teeth. It is considered one of the more important factors in establishing balanced occlusion


It is measured by the angle formed by the mesiobuccal cuspal incline to the horizontal plan when the long axis of the tooth is vertical to the plane
Cusp Angle
4- Cusp Height (cuspal inclines of tooth and inclination of cuspless teeth)

Types of posterior teeth

1- Anatomic teeth
2- Modified or semianatomic tooth
3- Non-anatomic tooth

Anatomic teeth

Simulate the natural tooth form. It has cusp height of varying degrees of inclination that will intercuspate with an opposing tooth of anatomic form. The standard anatomic tooth has inclines of approximately 33o

Non-anatomic tooth

Problems with anatomic teeth
1- The presence of cusp inclines can cause trauma, discomfort and instability to the bases because of the horizontal component of force that produced during function.
2- The use of adjustable articulator is mandatory. 3- Various eccentric records must be made for articulator adjustments.

4- Harmonious balanced occlusion is lost when settling occurs.

5- The bases need prompt and frequent relining to keep the occlusion stable and balanced.
6- Mesiodistal interlocking will not permit settling of the base without horizontal force developing. That acting on thin delicate mucosa and the underlying bone creates shearing that are not well tolerated


The arrows indicate the direction and the magnitude of the force generated by the two types of teeth as they penetrate the bolus of food during masticatory cycle

Sharp cusped teeth need less vertical force for penetration but produce more lateral force owing to the inclined plane effect. Flat teeth more vertical force but produce less lateral force components

Problems with non-anatomic tooth 1- Do not function efficiently unless the occlusal surface provides cutting ridges and spillways. 2- They can not be corrected by occlusal grinding without impairing their efficiency. 3- Appear dull and unnatural.

Selection of tooth forms is based on

1- The capacity of the ridges 2- Interridge distance 3- The ridge relationship

Strong well-formed resist horizontal force

1- The capacity of the ridges



A large interridge distance creates a long lever arm through which horizontal forces created by the inclines of cusps can act. 'Therefore, this force can be controlled by using flat teeth as the interridge distance increases.
2- Interridge distance

A large interridge distance

Non-anatomic posterior teeth used effectively to control the forces of occlusion and to stabilize the denture base supported by compromised weak ridge in either class II or class III ridge relationship
3- The ridge relationship

Classification of Relationship Between Arches

SkeletalDentalPosterior teethAnterior teethGeneral rulesClass 1 – mandibular only slightly backClass 2 – mandibular more backwardsClass 3 – mandibular more forward

1) Lever balance

2) Occlusal balance "Balanced Occlusion"

1- Lever balance

Dependent on tooth position as related to its base

Placing the teeth over the ridge or slightly lingual to it. Denture base area covers as wide area on the ridge as possible. Placing the teeth as close to the ridge as other factors will permit. Using as narrow a buccolingual width occlusal food table.

Is dependent on tooth contact

"stable simultaneous contact of the opposing upper and lower teeth in centric relation position with a continuous smooth bilateral gliding from this position to any eccentric position within the normal range of mandibular function".
2- Occlusal balance "Balanced Occlusion"

Bilateral balance in artificial teeth, is necessary to stabilize the bases.

All five factors of balance interact with each other, and changes in any one effect changes in the others. for the final analysis, the dentist can only control four of five factors. * The condylar guidance: can be completely fixed and is not his to change. * The incisal guidance and inclination of the plane of occlusion: can be altered within a small range according to esthetic and physiologic (phonetic) factors. * Cusps, on the teeth and tooth inclination of cuspless teeth and compensating curve: are the real working tools of balanced occlusion.

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