Concepts of Occlusionsdm.siue.edu/studentexams/Restorative/Fixed Prosthodontics/DROC … · Concepts of Occlusion Goldsmith “People seldom improve when they have no other model

Occ I - Anatomy: TMJ & Muscles of Mastication 1/23/08

© 2008 E M Langenwalter 1

1

Occlusion I

Concepts of Occlusion

Eric M. Langenwalter, DMD, MSDiplomate, American Board of Prosthodontics

OI_05_08 © 2008 E M Langenwalter, DMD, MS 2

Concepts of Occlusion

Goldsmith

“People seldom improve when they have no othermodel but themselves to copy after.”


Weepy Wilma




Weepy Wilma


Weepy Wilma


Definitions

• Occlusion• Is the act or process of closure or of being closed or

shut off

Glossary of Prosthodontic Terms - GPT-7




Definitions

• Gnathology• the science that treats the

biology of the masticatorymechanism as a whole: that is,the morphology, anatomy,histology, physiology,pathology, and the therapeuticsof the jaws or masticatorysystem and the teeth as theyrelate to the health of the wholebody, including applicablediagnostic, therapeutic, andrehabilitation procedures.



Definitions

• Centric Relation (Earlier)• C.R. is a maxilla to mandible relation in which the

heads of the condyles are in the rear-most, upper-most,and mid-most positions in the glenoid fossa with noregard to tooth contact

• R.U.M.



Definitions

• Centric Relation (Latest)• The maxillomandibular

relationship in which thecondyles articulate withthe thinnest avascularportion of their respectivedisks with the complex inthe anterior-superiorposition against the slopesof the articular eminences.





Definitions

• Centric Relation (Latest)• This occurs with a purely

rotary movement about atransverse (terminal hinge)horizontal axis,independent of toothcontact.



Definitions

Maximum intercuspation (MI)• Is the complete intercuspation

of the opposing teethindependent of condylarposition

• Aka – Intercuspal Position(ICP)



Definitions

Centric Occlusion (CO)• Old – C.O. is the

maximum intercuspationof the teeth at the mostclosed position.





Definitions

Centric Occlusion• New – C.O. is the occlusion

of opposing teeth when themandible is in centric relation.This may or may not coincidewith the maximumintercuspation position.



Definitions

CR to MI SlideOne or both condyles move either anteriorly, inferiorly, or both.


Definitions

Centric Relation Occlusion• Obsolete term• (No replacement term)• Is maximum

intercuspation of theteeth, in their most closedposition, with the condylein the Centric Relationposition





Definitions

Centric Relation Occlusion• If CRO exists, then CO (new)

exists.

• If CO (new) exists, then CROmay or may not exist.

• Why?


Optimum Functional Joint Position

Variation in the definitionof C.R.

• Early – R.U.M.• Latest – Superior/anterior• Challengers – downward

and forward



• Variation in the definitionof C.R.

• Evolution of thedefinition of C.R.• RUM

• Reproducibility-ligamentousposition

• Superior Anterior• Muscle function• Skeletal anatomy





Muscle force direction• Superoanterior

• Temporalis in contraction• Masseter in contraction• Medial Pterygoid in contraction• Infer. Lateral Pterygoid in tonus



Muscle force direction• Superoanterior• Downward and Forward

• Temporalis in contraction• Masseter in contraction• Medial Pterygoid in contraction• Infer. Lateral Pterygoid in

contraction



Optimum disc position• Properly interposed with

the thin middle zonebetween the condyle andthe eminence





Optimum joint position• Condyles are in their most

superoanterior position in thearticular fossa, resting againstthe posterior slopes of thearticular eminences, with thearticular discs properlyinterposed.

• A musculoskeletally stableposition

• C.R. defined by Dawson


Optimum Functional Tooth Contacts

Musculoskeletally stableposition:

• Is achieved only whenmuscles are in harmonywith a stable occlusion

• Even contact on teeth inclosure in CR



Direction of force on teeth• PDL response

• Vertical force – tension• Horizontal force - tension

& pressure





Direction of force on teeth• PDL response• Osseous response

• Pressure – destructive• Tension - acceptable



Direction of force on teeth• Osseous response• PDL response• Vertical forces achieved by:

• Tripodized contacts• Each cusp occludes with the

opposing fossa by making threecontacts



Direction of force on teeth• Osseous response• PDL response• Vertical forces achieved by:

• Tripodized contacts• Cusp tip-to-flat surface

• Force is applied to a surfacewhich is perpendicular to thelong axis of tooth

• More easily achieved thantripodization




Lever Systems

• Amount of force on teeth• Lever Systems


Which Lever System is the Mandible?


To which tooth can the most for beapplied due to the lever?





• Control Occlusal Force• Centric Force

• Best - Posterior Teeth• due to force being

applied along long axes.

• Worst - Anterior Teeth• due to loads being

applied oblique to thelong axes.



• Control Occlusal Force• Eccentric (Excursive) Force

• Best - Canines• Crown / root ratio• Greater sensory input• Weaker forces due to lever• Reflex reduction in muscle

force• Worst - Posterior Teeth

• Forces oblique to long axes• Less sensory input• Stronger forces due to lever• Reflex increase in muscle

force


Occlusal Scheme Goalsfor Natural Dentitions

• Avoid mediotrusivecontacts

• Avoid protrusive contactson posterior teeth

• Centric contacts even orslightly heavier onposterior teeth




Occlusal Schemes

• Balanced Occlusion• Cuspid Protected Occlusion• Anterior Group Function Occlusion• Unilateral Balanced Occlusion• Mutually Protected Occlusion• Dynamic Individual Occlusion


Occlusal Schemes

• Balanced Occlusion• All teeth touch bilaterally

• In Centric• And in Excursive

• For complete dentures• No longer used in fixed

prosthodontics


Occlusal Schemes

• Cuspid Protected Occlusion• Aka “canine rise,” “cuspid

disclusion”• Only working side canines touch

in lateral excursive• Often found in natural dentitions• This is a preferred occlusal

scheme for natural dentitions.




Occlusal Schemes

• Anterior Group Function Occlusion• Aka “Anterior Guidance”• Working side anterior teeth touch in

lateral• Used when cuspid is weak or

missing


Occlusal Schemes

• Unilateral Balanced Occlusion• Aka “Group function”• Working side posterior teeth touch

in lateral excursive movement• Most desirable group function

consists of the canine, premolarsand MB cusp of the first molar

• Contact posterior to MB cusp offirst molar is detrimental - Why?

• Typically used when patient has:• Class II Div I• Anterior Open Bite


Occlusal Schemes

• Mutually Protected Occlusion• In centric relation occlusion the

posterior teeth protect theanterior teeth by carrying thebrunt of the vertical forces

• In eccentric movements, theanterior teeth protect theposterior teeth by carrying theexcursive (oblique) forces

• Used for reconstruction• This is a preferred occlusal

scheme for natural dentitions.




Occlusal Schemes

• Dynamic Individual Occlusion• The occlusion is considered acceptable if the patient is

functioning efficiently and without pathosis - Okeson


Occlusal Schemes

• Dynamic Individual Occlusion• The occlusion is considered acceptable if the patient is

functioning efficiently and without pathosis - Okeson• As a clinician, you must know what pathosis looks

like in order to use this approach effectively.


Postural Influence on Tooth Contact

• Mandibular postural position• Normal upright position• Head extended position• Alert feeding position





• Mandibular posturalposition• Also known as

“physiologic rest position”• Usually 2 – 4 mm below

intercuspal positionNiswonger



• Normal upright position



• Head extended position• Face upward 45 degrees• Swallowing

• Go into CR whenswallowing - even if CR ≠MI.

• All teeth should contactevenly





• Alert feeding position• Head forward approx. 30 degrees• Eating Position• Long centric (Dawson)



• Alert feeding position• Head forward approx. 30 degrees• Eating Position• Long centric (Dawson)

• Misinterpretation: That CR isan area or a range

• CR is always a single positiondefined by the joints

• Long Centric influences Mxanterior lingual fossae

• Patients with Long Centricrequire greater concavity ofthe lingual fossae

• All teeth should contact evenly


Summary of Optimum FunctionalOcclusion

• Centric Closure Position• No deflective contacts in CR

• CR = MI = CRO• Bilateral even contact of

posterior teeth• Vertical forces carried by the

long axis of posterior teeth• Point – Flat Surface• Tripodization

• Freedom in the alert feedingposition

• Neuromuscular release




Summary of Optimum Occlusion

• Centric closure position• Eccentric positions

• Best teeth guide lateral movements• Canine rise• Anterior guidance• Group function

• No mediotrusive (non-working)contacts

• No posterior contacts in protrusive


Summary ofMutually Protected Occlusion

• CR = MI = CRO• Posterior teeth bear the vertical

forces• Anterior teeth have even or slightly

light occlusal contact• Anterior teeth bear the horizontal

forces• Anterior teeth disclude all posterior

teeth in lateral movement• Anterior teeth disclude all posterior

teeth in protrusive movement


Weepy Wilma




Weepy Wilma


Weepy Wilma


Weepy Wilma

Documents

Concepts of Occlusionsdm.siue.edu/studentexams/Restorative/Fixed Prosthodontics/DROC … · Concepts of Occlusion Goldsmith “People seldom improve when they have no other model