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Copy of Principles of Occlusion
Transcript of Copy of Principles of Occlusion
DIFFERENCE BETWEEN NATURAL AND ARTIFICIAL OCCLUSION
Dr. HAZEM MOURAD
BDS, MS, PhD, FICOI, FAOIA
Specialist Senior Registrar, Prosthodontics, DHA
Maximal Intercuspal Position.
Balanced Sliding Occlusion (Free Articulation)
Propriception and prematurities
Favofable area for mastication
Effect of non-vertical forces
Effect of incising
Independent movevement and response to pressure
Effect of malocclusion
CONCEPTS OF OCCLUSION IN NATURAL DENTITION
Unilateral Balanced Articulation
Mutually Protected Articulation
REQUIREMENTS OF COMPLETE DENTURE OCCLUSION
Stability of occlusion in centric relation.
Balanced occlusion contacts bilaterally in eccentric.
Unlocking the cusps mesiodistally.
Control of horizontal forces by buccolingual cusp height reduction.
Functional lever balance by favorable tooth to ridge crest position.
Cutting and shearing efficiency of the occlusal surface.
Anterior clearance of teeth during mastication.
Minimal occlusal contacts between the upper and lower teeth (lingualized occlusion).
Fundamentals for artificial occlusion
The smaller the area of occlusal surface acting on food, the smaller will be the crushing force on food transmitted to the supporting structures.
Vertical forces applied to an inclined occlusal surface causes non-vertical forces on the denture base.
Vertical forces applied to a denture base supported by yielding tissue causes the base to slide when the force is not centered on the base.
Vertical forces applied outside (lateral to) the ridge crest creates tipping forces on the base.
Balanced occlusion as related to complete denture
I. Lever Balance
It is present when there is equilibrium of the base on its supporting structures when a bolus of food is interposed between the teeth on one side and a space exists between the teeth on the opposite side.
Dircetion of force
Teeth close to ridge
Narrow BL teeth
II. Occlusal Balance
1. Unilateral occlusal balance
2. Bilateral occlusal balance
3. Protrusive occlusal balance
Factors affecting balanced occlusion (Hanau Quint - Laws of articulation)
Lateral condylar guidance
Horizontal condylar guidance
Overbit and overjet
As flat as possible
However, the effect of the occlusal plane as a determinant on balanced occlusion must be recognized, its position can be altered only slightly without creating serious functional problems. Its role is not as important as the other factors.
It’s one of the most important factors in establishing a balanced occlusion.
Curve of Spee
Curve of Wilson
Curve of Monson
Interactionof the 5 factors
SELECTION OF POSTERIOR TEETH FORM
Factors affecting selection of posterior teeth form
Patient’s age and neuromuscular coordination
Previous denture wearing experience
Classification of posterior teeth form
Balanced occlusion with non-anatomic teeth
Zero-degree teeth with inclination of the lower second molar.
Zero-degree teeth with balancing ramps placed posterior to the most distal tooth.
Zero-degree teeth set to steep compensating curves.
Balanced occlusion with flat teeth can be obtained by:
OCCLUSAL DESIGNS FOR BALANCED OCCLUSION
1. Spherical theory of occlusion
It involves positioning of the teeth according to compensating curves, anteroposterior curve, and lateral curve (to simulate natural teeth).
2. Centralizing occlusal concept
This concept centralizes the working occlusal surface toward the center of the ridge in the anteroposterior direction. The center of the basal seat is in the area of the bicuspids and the 1st molars, which is the area where the food is masticated.
3. Lingualized occlusion
Lingualized occlusion utilizes only the upper palatal cusps on each side to act as cutters operating in the central fossae of the lower teeth. This gives mortar and pestle type contact that lingualizes the resultant force without moving the teeth in relation to the ridge.
4. Linear occlusion concept
In this type of occlusion, the teeth are arranged so that the masticatory surfaces of the mandibular posterior teeth have straight, long, and very narrow occlusal form resembling that of a line articulating with opposing monoplane teeth.
5. Monoplane teeth arranged with compensating curve
The arrangement of monoplane teeth in a compensating curve of occlusion is similar to that for anatomic teeth.
6. Monoplane teeth arranged with balancing ramps
Monoplane teeth are arranges with balancing ramp just distal to the lower second molar.
7. Dynamic occlusion (functional generating path)
It’s considered the ultimate harmonious balanced occlusal form because the patient generates it himself resulting in an occlusion that in harmony with the TMJ and neuromuscular system.
When the foundation tissue is compromised, i.e. severely resorbed ridge, knife-edge, or one that is covered with thick movable flappy tissues, favorable control of occlusal forces can be utilized by the use of non-anatomic teeth arranged following the monoplane occlusion concept.
1. Monoplane Occlusion Concept
The monoplane occlusion concept utilizes non-anatomic teeth with flat occlusal surfaces set to a flat occlusal plane.
The objectives of this occlusal scheme are the neutralization of the inclines and the centralization of forces acting on the denture foundation. In order to maintain these objectives, it may be necessary to:
1. Reduce the size and number of teeth.
2. Position of posterior teeth in a central position.
3. Plane of occlusion is parallel to the mean denture foundation area.
4. Form devoid of projecting cusps.
2. Neutrocentric occlusion
DESIRABLE OCCLUSAL CONTACT RELATIONSHIP FOR REMOVABLE PARTIAL DENTURE
Simultaneous working side contacts should be obtained for the mandibular distal extension partial denture to distribute the stress over the greater possible area and improve masticatory function of the denture. Balancing and protrusive contacts are avoided since they would not enhance stability of the denture.
For class I mandibular RPD
Simultaneous working and balancing side contacts should be obtained to compensate for the unfavorable position of the maxillary bilateral distal extension partial denture posterior teeth whenever possible, which is usually lateral to the ridge, to accommodate position of the posterior teeth in the opposing arch.
For class I maxillary RPD
Simultaneous working side contacts only is required since balancing side contacts will not enhance denture stability as it is entirely tooth-supported by the framework on the balancing side.
For class II maxillary and mandibular RPD
Contact of anterior teeth in centric is desirable to prevent over eruption of opposing natural incisors. Contact of the anterior teeth in eccentric position is avoided as such contact will lead to unfavorable forces to maxillary anterior residual ridge and would be detrimental to the supporting tissues in this area, moreover, denture stability will be affected.
For class IV RPD
Contacts in working sides between the posterior teeth if the canine guidance does not make the molars out of occlusion.
No contacts in balancing side and protrusive in bounded spaces because it will not add stability of either and should be avoided.
In case of upper and lower bounded spaces
OCCLUSION CONCEPTS IN IMPLANT-SUPPORTED PROSTHESES
The types and basic principles of implant occlusion have largely been derived from occlusal principles in tooth restoration. Three occlusal concepts (balanced, group function, and mutually protected occlusion) have been established throughout clinical trials and conceptual theories. These occlusal concepts have been successfully adopted with modifications for implant-supported prostheses.
1. Bilateral stability in centric occlusion.
2. Evenly distributed occlusal contacts and force.
3. No interferences between retruded position and centric position.
4. Wide freedom in centric occlusion.
5. Anterior guidance in harmony with the border movements.
6. Smooth, even, lateral excursive movements without working/non-working interferences.
Basic principles of implant occlusion may include:
Occlusion Guidelines in Various Situations
Implant supported fixed prosthesis
Implant Supported Overdenture
a) opposing natural dentition
b) opposing a complete denture
Group function(widely accepted)
Mutually protected with shallow anterior guidance (recommended)
a) for normal ridges
b) severely resorbed ridges
Bilateral Balanced with lingualized occlusion
Class III or IV partially edentulous
Free standing FPD
Class I or II partially edentulous
Free standing FPD
Group function (when anterior teeth are periodontally compromised)
CONCEPTS OF OCCLUSION
Advantages of Balanced Occlusion
1. Distribution of load.
3. Reduced trauma on the supporting tissues.
4. Easier Functional movement.
5. Efficiency: grinding and cutting of food.
CONCEPTS OF OCCLUSION IN SINGLE DENTURE
The most important aspect when setting up the teeth is to ensure that the inclined planes do not make contact as the jaws closes into centric position and that the final occluded position of the teeth involves contact of surfaces which transmit forces vertically only, not horizontally. This can be avoided with either anatomic or non-anatomic teeth.
Space distal to canine
Cuspt to fossa