Occlusion Part II / orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY

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OCCLUSION (PART II)


CONTENTS1. Concepts of occlusion

2. Optimum orthopaedically stable joint position

3. Optimum functional tooth contacts

4. Normal versus ideal occlusionwww.indiandentalacademy.com

5.Criteria for Optimum functional occlusion

6.Occlusal contact patterns

a) Canine guided occlusion

b) Group function occlusion

7. Summary

8. References www.indiandentalacademy.com

“What is the best functional relationship or occlusion of the teeth” ?


Concepts of occlusion

Three occlusal concepts:The GnathologicalThe Freedom-in-centricEuropean conceptual model


THE GNATHOLOGICAL CONCEPT

•Mid 1920’s McCollum. Gnathology: exact science of mandibular movement and resultant occlusal contacts. Instruments:• Kinematic face bow, Gnathoscope and Gnathograph


Balanced occlusion:(complete dentures)“During functional excursions there is multiple simultaneous contacts present both on the working side and on the balancing side”Stallard and Stuart: organic or organised occlusion.-neglected that mastication is more vertical than lateral.


ARNE G. LAURITZENDirection of occlusal stresses-long axis of teeth. Centric relation=centric occlusion (condyles in uppermost and rearmost position)Simultaneous occlusal loads fall on as great number of teeth.Lateral excursion may be free.Canine guided occlusion.Group contact between upper and lower anterior teeth during protrusive movement.www.indiandentalacademy.com


NILES GUICHET AND GNATHOLOGYOptimal occlusion (1966)Canine guided occlusion- biomechanics Occlusion must be in harmony with the mandibular movements of each patient.Ganathograph and Pantograph.Denar articulator.


There is horizontal movement of the mandible from the maximal intercuspal position and teeth are capable of standing that horizontal stress in function .

(D’ Amicos)-canines - eight times stress than on the 2nd premolars.


VISION OF TRANSOGRAPHIC CONCEPT

Page’sFour principles:1. Opening axis2. Cranial plane3. Bennett movement4. Envelope of motion

1. Opening axis:12º to 15º of rotation. Transverse hinge axis –reproducible.


2.Cranial planes:No translatory condyles, so no practical support for horizontal plane.

3.Bennett movement: such a movement is because of mouth opening to 2 noncolinear axes, Page did not concede to the existence of the Bennett side shift.

4. In the discussions conceding the envelope of motion, when one takes the motions to a narrow functional terminal orbit, raised a great number of questions in the oral rehabilitation.www.indiandentalacademy.com

FREEDOM IN CENTRICPosselt was firstFunctional occlusion- Ramfjord and Ash- 1970’sCriteria are to attempt to eliminate the need for neuromuscular adaptation.According to this concept, Maximum intercuspation and centric relation are coincident but flat areas on the depth of the fossae, on which opposing


cusps occlude, will allow for a certain degree of freedom in both centric and eccentric movements without the guiding influences of occlusal inclines.

Vertical dimension of occlusion in maximum intercuspation and centric relation might be the same when all the interferences for closing in centric relation are eliminated.




OCCLUSAL CONCEPTS OF SCHUYLERCorrection of occlusal disharmonies in the natural dentition and to the concepts of freedom in centric and incisal guidance.According to Schuyler, Freedom in centric is a maxillomandibular position where maximum intercuspation and centric relation coincide to a certain degree of freedom for eccentric excursions without the influence of occlusal inclines.www.indiandentalacademy.com

Anteroposterior difference – 0.5 to 1 mm Variation in centric relation recording – not a point – area in relation to horizontal plane.Anterior guidance – Purpose: permit a condylar motion without restrictions along with the prevention of posterior contacts, during lateral excursions



BEYRON’S OCCLUSAL CONCEPTSBased on functional convenience and avoidance of discomfortMost physiological inter-relationship between morphology and function might be the most natural one.Neuromuscular mechanism- protects teeth – excessive loads – protective reflex- important role in mandibular movement patterns. www.indiandentalacademy.com

PANKEY MANN PHILOSOPHYMonson’s sphere (occlusal line and plane) + Meyer’s concepts of a functionally generated pathPankey Mann Philosophy – oral rehabilitationObjectives:- optimal health, masticatory efficiency, comfort and estheticsRecently, Pankey Mann Schuyler concept (based on group function)www.indiandentalacademy.com

Stable and Static contacts - greatest number of teethLong centric – Occlusal harmony with an anterior slide between centric relation and maximum intercuspation (1mm) and a small amount of lateral freedom for accommodation of the Bennett movement on the horizontal plane.Group function during lateral excursion (working side)Balancing side - No contactsProtrusion – Immediate disocclusionwww.indiandentalacademy.com


DAWSON’S CONCEPTPeter Dawson Manipulation of the jaw in centric

relation (Bimanual technique)

Recording the border movements (Modification of functionally generated path technique)


Anterior guidance: Anterior teeth are more capable of

supporting stress than posteriors:(a)Position of anteriors(b)Higher density of bone(c)Longer roots, better crown : root

ratio. Theory of “Nutcracker”


GERBER’S CONDYLAR DISPLACEMENT THEORY

European concept

“ The normal or ideal occlusion was one in which the teeth would be in maximum intercuspation, with the condyles centered in the articular surfaces in the median and uppermost position. Any deviation related to this mandibular centralization constitutes a condylar displacement.” www.indiandentalacademy.com


RAMFJORD AND ASH CONCEPTS OF OCCLUSION

Equilibrium between the different components of masticatory system.

Freedom for condyle movement The occlusal concept applied should

promote occlusal stability, does not exceed the needs and finances of most persons, is controlled by general clinician and does not need a specialized laboratory technician.



Normal versus Ideal occlusion


Optimum orthopaedically stable joint position

Centric relation, is the position of the mandible when the condyles are in an orthopaedically stable position.


Centric relation1:The maxllomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior–superior position against the shapes of the articular eminences.This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superiorly and anteriorly.


It is restricted to a purely rotary movement about the horizontal axis(GPT-5).

2:The most retruded physiologic relation of the mandible to the maxillae to and from which the individual can make lateral movements.It is a condition that can exist at various degrees of jaw separation.It occurs around the terminal hinge axis(GPT-3).


3:The most retruded relation of he mandible to the maxillae when the condyles are in the most posterior unstrained position in the glenoid fossae from which lateral movement can be made , at any given degree of jaw separation(GPT-1).

4:The most posterior relation of the lower to the upper jaw from which lateral movement can be made at a given vertical dimension(Boucher).www.indiandentalacademy.com

5:A maxilla to the mandible relationship in which the condyles and the disks are thought to be in the midmost,uppermost position.The position has been difficult to define anatomically but is determined clinically by assessing when the jaw can hinge on a fixed terminal axis (upto 25mm).It is clinically determined relationship of the mandible to the maxilla when the condyle–disk assemblies are positioned in their most superior position in the mandibular fossae and against the distal slope of the articular eminence(ash).www.indiandentalacademy.com

6:The relation of the mandible to the maxillae when the condyles are in the uppermost and the rearmost position in the glenoid fossae.This position may not be able to be recorded in the presence of dysfunction of the masticatory system.

7: A clinically determined position of the mandible placing both the condyles into their anterior uppermost position.This can be determined in patients without pain or derangement in the TMJ (Ramfjord)www.indiandentalacademy.com


Centric relation has been described in three different ways: anatomically, conceptually, and geometrically.Anatomical:It is the position of the mandible to the maxilla, with the intra-articular disc in place when the head of the condyle is against the most superior part of the distal facing incline of the glenoid fossa.This can be paraphrased uppermost and foremost. www.indiandentalacademy.com

Conceptual:It is that position of the mandible relative to the maxilla, with the articular disc in place, when the muscles that support the mandible are in their most relaxed and least strained position.Geometrical:It is the position of the mandible relative to the maxilla,with the intra- articular disc in place, when the head of the condyle is in terminal hinge axis.www.indiandentalacademy.com

Dawson’s concept Gelb’s

concept


Optimum functional tooth contactsClosure in CR

Creates an unstable occlusion

Neuromuscular systemFeed back muscles

Mandibular position

More stable occlusionwww.indiandentalacademy.com

Musculoskeletal stable position

Stable occlusal condition

HARMONY




Conclusion:Optimum occlusal conditions during mandibular closure would be provided by even and simultaneous contact of all posterior teeth.


Criteria for optimum functional occlusion

Even and simultaneous contact of all possible teeth when the mandibular condyles are in their most superoanterior position, resting against the posterior slopes of the articular eminences, with the discs properly interposed.


Occlusal contact patternsDirection of force Amount of force




Criteria for optimum functional occlusion

First - Even and simultaneous contact of all possible teeth + centric relationSecond – each tooth should contact in such a manner that the forces of closure are directed through the long axis of the teeth.


Nutcracker theory


Canine guided occlusion


Group function occlusion


Buccal to buccal cusp contacts are desirableNo non-working side contacts


Protrusive contacts


Postural considerations and functional tooth contacts

Depends on head positionIn the alert feeding position, as well as in the normal upright position, the posterior teeth should contact more heavily than the anterior teeth (mutually protected occlusion).


Summary1. When the mouth closes, the condyles are

in their most superoanterior (Musculoskeletal stable) position, resting on the posterior slopes of the articular eminences with the discs properly interposed. In this position there is even and simultaneous contact of all posterior teeth. The anterior teeth also contact but more lightly than the posterior teeth.


2. All tooth contacts provide axial loading of occlusal forces.

3. When the mandible moves into a laterotrusive position, there are adequate tooth-guided contacts on the laterotrusive (working) side to disocclude the mediotrusive (nonworking) side immediately. The most desirable guidance is provided by the canines (canine guidance).


4. When the mandible moves into a protrusive position, there are adequate tooth-guided contacts on the anterior teeth to disocclude all posterior teeth immediately.

5. In the alert feeding position, posterior tooth contacts are heavier than anterior tooth contacts.


REFERENCES Occlusion series in BDJ, 2001;191:6-7 Okeson JP. Management of Temporomandibular Disorders and Occlusion, ed. 4th, 1998; Mosby Ash MM and Ramfjord S. Occlusion, ed. 4th, 1966; WB Saunders Company, Michigan


Santos JD. Occlusion Principles and Concepts, ed. 2nd, 1999; Ishiyaku EuroAmerica, Inc. U.S.A. Shillingburg HT. Fundamentals of Fixed Prosthodontics, ed.3rd, 1997;Quintessence



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Occlusion Part II / orthodontic courses by Indian dental academy

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