dr keson b c tan bds (hons), msd

Dr Keson B C Tan BDS (Hons), MSD


Criteria for

Optimum Functional Occlusion


“the act of closure or state of being closed”

Dorland’s Medical Dictionary

OCCLUSION Definition:


Occlusion “relationship of the maxillary

and the mandibular teeth when they are in functional contact during activity of the mandible.”

Okeson, 3rd Ed, 1993


History of Occlusion 1. Balanced Occlusion 2. Gnathology 3. Unilateral Eccentric Contacts 4. Dynamic Individual Occlusion


Balanced Occlusion • Bilateral Balance • All lateral & protrusive movements • Complete dentures


Gnathology • The exact science of mandibular

movement and resultant occlusal contacts.

• Dogmatic treatment goals. All nonconforming occlusions were considered malocclusions and were treated to “ideal”.


Unilateral Eccentric Contacts • Schuyler, Stallard, Stuart • Laterotrusive & Protrusive contacts

only on anterior teeth • Anterior Guidance


Dynamic Individual Occlusion

• No specific occlusal configuration ideal

• Physiologic Occlusion - health & function of the Masticatory System

• Physiologic configuration acceptable regardless of specific tooth contacts.


Stomatognathic Orthopedics • A concept in dentistry concerned with Postural

Relationships of the jaws • Analysis of the harmful effects of improper

craniomandibular relationships on dental and other components of the stomatognathic system;

• The Diagnoses and Correction of such malrelationship; and

• The Treatment and/or Prevention of disturbances resulting therefrom.


Orthopedics • that branch of surgery dealing with

the preservation and restoration of the function of the skeletal system, its articulations and associated structures.


Pathofunction • not only includes the abnormal function but also the pathology and the tissue changes occurring as a result of that abnormality

• a state of morphofunctional

harmony between occlusal morphology and neuromuscular function

• this range of physiologic

response may show a biologic variation from an ideal response to a state of adaptation

Orthofunction

Krough-Poulsen


Somatognathic System

Dento-Alveolar Complex

Musculature CMA

CNS

The careful study of the interactions among the three components

(i.e. the Dento-Alveolar Complex, the Craniomandibular Articulation and

the Neuromusculature).


CRITERIA FOR OPTIMUM FUNCTIONAL OCCLUSION

Which occlusal configuration is most likely to eliminate occlusal pathosis?


Treatment Goal


1. Elimination of occlusal disorders 2. Restoration of the mutilated dentition


OPTIMUM ORTHOPEDICALLY STABLE JOINT POSITION

OPTIMUM FUNCTIONAL TOOTH CONTACTS



Somatognathic System

Dento-Alveolar Complex

Musculature CMA

CNS

The careful study of the interactions among the three components

(i.e. the Dento-Alveolar Complex, the Craniomandibular Articulation and

the Neuromusculature).


CRANIOMANDIBULAR ARTICULATION

• 1. Two TMJs • 2. Teeth

Contact and force application in 3 areas



• Considered to designate the mandibular position with the condyles in an orthopedically stable position

Centric Relation


Centric Relation

• Early definition of CR • Limited by ligaments • Ligamentous Position • Reproducible - used in Complete

Denture construction

Most Retruded Position


CR (Most retruded) = MI

Ramfjord, 1961 - Most physiologic position ??

Centric Relation


Recent concepts

• Most superior position (Apex of Force position) - Dawson, 1974

• Anterior-superior position - Glossary of Prosthodontic Terms, 1987

Centric Relation


Positional Stability • Not determined by disc • Like all other joints, determined by

muscles that pull across joint • Masseters & Medial Pterygoids -

superoanterior • Temporalis - superior • Inferior Lateral Pterygoids - anteriorly,

against posterior slopes of the articular eminences

OPTIMUM ORTHOPEDICALLY STABLE JOINT POSITION = CR


Anatomical Situation

(1) Disc of dense fibrous CT, devoid of nerves and blood vessels

(2) Disc to separate, protect and stabilize condyle in mandibular fossa.



Articular Disc Position • Disc morphology • Interarticular pressure • Tonus of superior lateral pterygoids • Disc rotated anteriorly on condyles as

far as allowed by: • discal spaces (determined by interarticular

pressures) • posterior border thickness



• Traditional “CR” • A border ligamentous position

was considered an optimum functional position?

• Border positions not considered optimum for any other joint in the body.

RETRUDED POSITION


MOST SUPERIOR POSITION • A-P Range

? Superoposterior Most superior (Dawson)

Superoanterior (MS)

• Inner horizontal fibres of TM ligament - tight or loose


“Gelb” (4-7) Position

• Condyles halfway down posterior slopes of articular eminences

• Inferior lateral pterygoid must counter constant superior positioning action of elevators.


RETRUDED POSITION • Not physiological • Not anatomically sound • Retrodiscal tissue

– highly vascularised and innervated – not structured to accept loading

• Dry skull exam - thin bone


• Condyles in their most superoanterior position in the articular fossae

• Resting against the posterior slopes of the articular eminences

• Articular discs properly interposed • =CR



• Orthopedic joint stability maintained even with heavy elevator contraction

• Most musculoskeletally stable (MS) position of the mandible

• Similar to Dawson’s concept of CR



SUPERIOR-ANTERIOR POSITION

1. Most orthopedically sound position 2. Optimal musculoskeletally stable

position 3. Clinically reproducible for Prosthodontic

needs 4. Repeatable THA obtainable


CR LOCATING TECHNIQUES

Mandibular guiding techniques - Passive • Bimanual Manipulation (Dawson)

Muscle Seating techniques - Active • Anterior jig (Lucia) • Leaf gauge (Huffman)


Chewing Cycle Studies • Working condyle moves posterior to

MI during the final closing portion of a cycle

• Functional position? - transient • A-P range in ‘healthy’ joints - < 1 mm ?


IATROGENIC SUPERIOR-MEDIAL CLOSE-PACK POSITION OF THE CMA

• ISMCP • Synonymous with Centric Relation (CR) • A NON-Ligamentous Position • A Prosthodontic/Orthodontic CONVENIENCE

during Occlusal Rehabilitation / Reorganisation • Joint areas also loaded at MEDIAL poles once

MAXIMUM INTERCUSPATION is coordinated at that MMR

• BIOLOGICALLY ACCEPTABLE and CLINICALLY USEFUL if TMJs are HEALTHY


SELECTION OF A THERAPEUTIC

CONDYLAR POSITION

• IMSCP • LOOSE-PACK POSITIONS


Optimum Functional Tooth Contacts

Stable Occlusal Condition

Musculoskeletally Stable Joint Position

Harmony ( )



1. Effective function 2. Minimize damage to Masticatory

system • Joints • Teeth • Supporting structures

3. Accept heavy forces


Coordination of a Cybernetic Occlusal Interface at the prescribed MMR

Functional Considerations • Permissive Occlusal Specification • Directive Occlusal Specification

Parafunctional Considerations • Diurnal Clencher • Nocturnal Bruxer


Adaptive Mechanisms / Options Available • Avoidance engrams may be set up • Wear of offending tooth or ‘high’ restoration • Supra-eruption and/or depression

phenomena • Increased mobility due to occlusal trauma • Parafunctional erasure-type patterns may

be triggered? • Joint changes

OCCLUSAL INTERFERENCE

X ??


During Mandibular Closure • Occlusal stops • Bilateral • Even & simultaneous • Maximum no. of teeth to spread load • CR=MI



Direction of Forces on Teeth • Pressure vs tension

• Osseous tissue do not tolerate pressure resorption • PDL suspensory CT fibres transform occlusal load into tension




• Contact on: • Cusp tip - Axial • Ridge crest - Axial • Fossa bottom - Axial

• AXIAL FORCE • PDL aligned to accept and dissipate

Direction of Forces on Teeth


Direction of Forces on Teeth • Contact on :

• Incline - Tipping • HORIZONTAL FORCE

• PDL not effective in dissipating forces

• Compression & Elongation



Axial Loading 1) Cusp tips vs Flat surfaces perpendicular

to long axis 2) Tripodisation

• Cusp vs Fossa • 3 contacts around each cusp tip



Vertical Loading • Physiologic

Horizontal Loading • Pathologic bone responses • Neuromuscular reflexes to avoid / guard against incline contacts



Amount of Force on Teeth • Class 3 Lever System

• Fulcrum - TMJ • Force Vector - Masseter / Medial

Pterygoid • Load - Bolus on Teeth



• Force on Anterior Teeth << Posterior Teeth • Canines

• Best suited to accept horizontal forces • Longest and largest root • Best crown / root ratio • Dense compact bone • Sensory afferents • Less muscle activity with canine eccentric contact

Amount of Force on Teeth



Class 3 Lever System

Amount of Force on Teeth


Posterior Teeth >> Anterior Teeth


Canine Guidance • Disocclude or disarticulate posterior

teeth in eccentric movements



Group Function • Several WS teeth contact during laterotrusive

movement • Canine, premolars, m-b cusp of 1st molar • Buccal cusp - to - buccal cusp contacts • Posterior WS contacts undesirable - Greater force near fulcrum and force vectors



Mediotrusive (Balancing) Contacts • Destructive to masticatory system

• Magnitude and direction of forces • Neuromuscular responses -

increased muscle activity ?


??X


Protrusive Contacts • Horizontal forces best received

by anterior teeth • Anterior Guidance - disarticulate posteriors



• Posterior protrusive contacts • Destructive to masticatory system • Amount and direction of forces • Neuromuscular responses

Protrusive Contacts



Posterior Teeth • Stop mandible in Closure • Axial loading

Anterior Teeth • Guide mandible in eccentric movements • Labial inclination - Axial loading not possible • Destruction of supporting structures with

heavy occlusal contacts (eg. Posterior Bite Collapse )



Mutually Protected Occlusion

• Occlusal contacts in CR / MI • Posterior Teeth > Anterior

Teeth



Postural Considerations • Posterior contacts > Anterior

contacts in all postures • Alert Feeding Posture

• Check in this position after treatment in reclined position



What is Optimal Occlusion?

Perhaps that occlusion which most provides continuing

Functional Homeostasis (One that best adapts to its changing

functions)

Moyers, 1969


PATHOFUNCTION • not only includes abnormal function but

also the pathology and the tissue changes occurring as a result of that abnormality

• A state of morphofunctional harmony between occlusal morphology and neuromuscular function

• this range of physiologic response may show a biologic variation from an ideal response to a state of adaptation

ORTHOFUNCTION

Krogh-Poulsen


Form & Function


ORTHOFUNCTION

DYSFUNCTION

DEGREE OF ADAPTATION

FORM (Occlusion)

FUNCTION (Neuromuscular

Response)

Ideal Function

Normal Function

No adaptation necessary

Wide zone of adaptation

No occlusal interferences

Occlusal Interferences a. interference with closure (IP, RCP, MCP) b. excursive interferences c. mandibular displacement

No muscular hyperactivity

Minimal muscular activity

SUBLIMINAL SYMPTOMS FUNCTIONAL DISORDERS (tissue lesions)

a. periodontium b. muscles c. joints

Narrow zone of adaptation Uncontrolled adaptation

FUNCTIONAL DISTURBANCES a. decreased function b. spasm with fatigue c. bruxism

Major or minor occlusal interferences

Increased muscle hyperactivity


PATHOLOGIC OCCLUSION

Any occlusion judged to be a causal factor in the formation of traumatic lesions or disturbances in the supporting structures of the teeth, muscles and temporomandibular joints.

DEFINITION:


Pathologic Occlusion

Whether or not an occlusion produces injury. Not how the teeth occlude.

Criterion:


Orthofunction Pathofunction

Zone of Physiologic

Tissue Response

Morphofunctional Disharmony

Zone of Adaptation

or of

Subliminal

Effects

or

Symptoms

Zone of Pathologic

Tissue Response

Morphofunctional Harmony


Asymptomatic “Supernormal”

Adaptive Orthofunction

Dysfunctional Pathofunction Functional Spectrum

All individuals can be located on continuous function spectrum ranging from “supernormal” asymptomatic status to dysfunctional.


Structural and Behavioral Objectives


Stomatognathic Orthopedics • A concept in dentistry concerned with Postural

Relationships of the jaws • Analysis of the harmful effects of improper

craniomandibular relationships on dental and other components of the stomatognathic system;

• The Diagnoses and Correction of such malrelationship; and

• The Treatment and/or Prevention of disturbances resulting therefrom.



1a). Condyles in most superoanterior position (musculoskeletally stable), resting on the posterior slopes of the articular eminences with the discs properly interposed.

1b). Even, simultaneous contact on all posterior teeth.

1c). Anterior teeth also contact but more lightly than posterior teeth.

Summary


Summary

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

3. In laterotrusion, adequate tooth-guided contacts on laterotrusive (working) side to disclude mediotrusive (nonworking) side immediately. Canine guidance desirable. Group function acceptable.



4. In protrusion, adequate tooth-guided contacts on anterior teeth to disclude all posterior teeth immediately.

5. In alert feeding posture, posterior tooth contacts remain heavier than anterior tooth contacts.

Summary


dr keson b c tan bds (hons), msd

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