COMPLETE DENTURE OCCLUSION
Dr. Monia MN KandilBalanced 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) conceptThere 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:
Excursive Movements
Laterotrusive and MediotrusiveNon-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 teethA, 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 axisTranslation
B. Translation is the bodily movement of the head of the condyleCondylar 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 condyler guidance is the only factor given by the patient.
Can’t be changedIt is a complex lateral movement or lateral shift of the mandible resulting from the movements of the condyles along the lateral inclines of the mandibular fossae during lateral jaw movement.
Bennett Movement
The immediate Bennett side-shift which occurs at the beginning of the translation. The progressive Bennett side shift.
The Bennett movement can be studied in detail by “pantographic registration”, which shows that it consists of:
In the immediate Bennett side shift: The condyle moves essentially straight medially as it leaves centric relation at the beginning of the lateral jaw movement. while The progressive Bennett side shift: Creates an angle (the Bennett angle) formed by the sagittal plane and the path of the advancing condyle during lateral mandibular movement as viewed in the horizontal plane
Bennett Movement & Angle
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 articulatorThe 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 vertical overlap (VO)
A. Steep incisal guidanceB. 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 Condy. G.
Steep Inc.G. calls for steep cusps, steep Occlu.Plane or a steep Comp.Curve 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 guidanceOcclusal Plane
Cusp Height
Compensating curve
More controllable
Occlu. Plane 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 occlusionAny necessary alteration for balancing the occlusion must be made in rarely, for other factors affecting the occlusion (eg, the cuspal inclination)
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 MechanicsThe amount of leverage or torque exerted on the occlusal plane is a function of the height of the plane above the ridge. Torque = force x Distance from fulcrum.
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 teethPrinciple 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 teeth2- 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 33oNon-anatomic tooth
Problems with anatomic teeth1- 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- Inter-ridge distance 3- The ridge relationshipStrong well-formed resist horizontal force
1- The capacity of the ridgesA 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.
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 relationship3- The ridge relationship
Classification of Relationship Between Arches
SkeletalDentalPosterior teethAnterior teethGeneral rulesClass 1 – mandibular only slightly backClass 2 – mandibular more backwardsClass 3 – mandibular more forward1) Lever balance
2) Occlusal balance "Balanced Occlusion"1- Lever balance
Dependent on tooth position as related to its basePlacing 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"