MasticatoryAnatomy TheMusclesofMastication A. TemporalisMuscle Origin:

Masticatory. Anatomy

The. Musclesof. Mastication

A. Temporalis. Muscle Origin: temporalfossa& temporalfascia Insertion: coronoidprocess &anterioroframus

A. Temporalis. Muscle Function: Elevationand positioningofthe mandible

B. Masseter. Muscle Origin: zygomaticarch Insertion: lateralsurface oframus, coronoid process&angleof mandible

B. Masseter. Muscle Function: powerwith verticalelevationof themandible; deep portionstabilizesthe condyleinprotrusive closure

C. Medial. Pterygoid. Muscle Origin: medialsurfaceof lateralpterygoidplate, pyramidalprocessof palatinebone&Mx tuberosity Insertion: medialsurface oframus&angleof mandible

C. Medial. Pterygoid. Muscle Function: elevationof themandible, protrusionofthe mandibleandlateral movementofthe mandiblewith unilateralactivation

Pterygomasseteric. Sling

D. Inferior. Lateral. Pterygoid. Muscle Origin: lateralsurfaceof lateralpterygoidplate Insertion: pterygoid foveaofcondyle

D. Inferior. Lateral. Pterygoid. Muscle Function: protrusion, lateralmovementand contributestoopening

E. Superior. Lateral. Pterygoid. Muscle Origin: infratemporal surfacegreaterwingof thesphenoidbone Insertion: pterygoid foveaofthecondyle andvariabletothedisc

E. Superior. Lateral. Pterygoid. Muscle Function: activewiththe musclesofclosure, especiallyaiding stabilizationofthe condyleduringthe powerstroke

Temporomandibular. Joint Anatomy

“ Craniomandibular. Joint”: a diarthrodialorsynoviallinedjoint

Acompoundjoint: >2 components • Temporal. Bone • Mandibular. Condyle • Articular. Disc

A. Temporal. Bone • Cranialcomponent • Mandibularfossa • Articulareminence • Articularsurfacefrom superiorfossatothe anterioraspectofthe eminence, thickest bone.

B. Mandibular. Component: Condyle • Condylardimensions: AP 810 mm ML 1520 mm • Articularsurface: anteriorsuperioraspect

B. Mandibular. Condyle • Variationsidetosidein sizeandshapeiscommon. Responsetoloading • Lateralpoleanteriorto medialpole.

C. Articular. Tissue • Origin: modified periosteumof intramembranousbone, NOTendochondralorigin. Aconsequenceof 2 embryonictissuemasses growingtowardseach other, NOTasingletissue massclefttoformajoint articulation.

C. Articular. Tissue • Function: 1) loaddistribution 2)synoviallubrication • Character: NOT hyalinecartilage, but fibrousinnature 1)avascular 2)NOTinnervated 3)resistanttoshear, tensionforces 4)increased remodelingpotential

D. Articular. Disc • Composition: avascularconnective tissue, collagenous • Shape: biconcavein crosssectionwith posteriorband, intermediatezoneand anteriorband • Position: posterior bandedgeat“ 12: 00”

D. Articular. Disc

E. TMJoint. Capsule • Function: 1)limitextreme. ROM 2)synoviallining 3)confinessynovial fluid 4)jointproprioception

F. Mandibular. Ligaments Restrictandlimit jointrangeofmotion

A. Temporomandibular Ligament • Lateralthickeningof the. TMjtcapsule • Limits: retrusionand inferiorcondylar distraction

B. Collateral. Ligaments • Medialandlateral • Limit: medialand lateralmovementof thediscrelativetothe condyle

C. Accessory. Ligaments • Sphenomandibular Ligament: nonfunctionalvestige orremnantof Meckel’scartilage • Stylomandibular Ligament: limits extremejaw protrusion

TMJoint. Stability • NOT ligaments • Muscles pulling acrossjoints • Articular. Disc Geometry

TMJoint. Anatomy: sagittal • Lateral. Pterygoid. M Superiorheadinsertion condyle&sometimesdisc Inferiorheadinsertion condyle • Retrodiscaltissues 1)Superiorelastic 2)Inferior“check ligament” 3)Loose. C. T. venous compartmentand innervated • Synovialtissues

TMJoint. Retrodiscal. Tissue

TMJoint. Innervation: V

TMJoint. Functional. Anatomy Readpagesin. Okeson, pp. 2226!

Centric. Relation (Okeson, 2003) Jawpositionwiththe condylesintheirmost superoanterior postionsinthe articularfossae, restingagainstthe posteriorslopesofthe articulareminences, withthearticulardiscs properlyinterposed.

Biologyof. Centric. Relation • Muscloskeletal. Stability: astablepositioninwhich toloadthejoint, mmpull acrossjtsseatingcondyle • Clinical. Evidence: patientsdowellwith. IP coincidentalwithjaw positionin. CR(clinical experience)

Biologyof. Centric. Relation • Clinicallyrepeatable: a referencepositionfor restorativedental procedures … but. NOTimmutable! (Celenza. FV, JPD 1973) … (~1 yr? )