Temporomandibular joint

1. Temporomandibularjoint & musclesof mastication
MASTICATORYSYSTEM
 An extremelycomplex systemcomprisedof structuresthatare integratedinthe act of
MASTICATION
ORAL MOTOR BEHAVIOR
Referstofunctionandparafunctionsof the mouthand associated structures
OTHER FUNCTIONS& PARAFUNCTIONS
 Speech
 Yawning
 Singing
 Bruxism
 Clenching,etc.
 Painand dysfunctionof musclesnotnecessarilyinvolvingthe masticatorymuscles
CRANIOMANDIBULARDISORDERS
TMJ
 The area where the mandible articulateswiththe temporal bone of the cranium.
 A jointon each side of the headthat allowsformovementof the mandible forspeechand
mastication
 * JOINT - a site of junctionor unionbetweentwoormore bone
 The TMJ articulationiscloselyassociatedwiththe functioningof the teeth
 Name isderivedfromthe 2 bonesthatenterintoits formation
 TEMPORAL BONE
 MANDIBULAR BONE
 It isan example of aDIARTHROSIS *
(bilateral synovial joint)

2. • Articulationthatpermitsfree movement
• Freelymovable joint
• The TMJ makesmuscularand ligamentaryconnectionstothe cervical regions,forminga
functional complexcalledthe
CRANIO-CERVICO-MANDIBULARSYSTEM
 It providesforHINGING movement, GINGLYMOIDJOINT
 At the same time isalsoprovidesfor GLIDING movement, ARTHROIDALJOINT
GINGLYMOARTHROIDALJOINT
Bonesof the joints
 CONDYLE of the mandible
 ARTICULARFOSSA/GLENOID/MANDIBULARFOSSA
(temporal bone)
 ARTICULAREMINENCE of the temporal bone
 GLENOID FOSSA & CONDYLE are linedbyFIBROCARTILAGEnothyaline cartilage like most
synovial joints
 * a cartilage thatcontainsfibrousbundlesof collagen
ARTICULARDISC/ MENISCUS
 Interposedbetweenthe condyle andthe temporal bone
 The condyle isnormallysituatedonthe thinnerintermediatezone of the disc
 Consistsof dense collagenousconnectivetissue,
 Relativelyavascular,
 Hyalinized,
 Devoidof nervesEXCEPTforthe extreme peripheryof the disc, BILAMINAR ZONE
 VASCULAR,INNERVATEDTISSUE
 ALLOWINGTHE CONDYLE TO MOVE FORWARD
 The articular discfunctionsasa thirdbone in the formationof the TMJ

3.  It isa non0ssifiedbone whichpermitsforthe complex movementsof the joint
 Thus,the TMJ is alsoclassifiedasa COMPOUNDJOINT
COMPOUNDJOINT
 A jointmade upof at leastTHREE bones
 The articular discdividesthe TMJinto2 compartmentsor SYNOVIALCAVITIES*
 UPPER SYNOVIALCAVITY
 LOWER SYNOVIALCAVITY
* Filledwithclear,lubricating,viscousfluid(like eggwhite) SYNOVIALFLUID
JOINTCAPSULE/CAPSULARLIGAMENT
 Completelyenclosesthe TMJ
 SUPERIORLY
 Wraps aroundthe marginsof the temporal bone’sarticulareminence andarticularfossa
 INFERIORLY
 Wraps aroundthe circumference of the mandibularcondyleincludingthe neck
Functions
 Acts to resistmedial,lateral orinferiorforcesthattendtoseparate or dislocate the articular
surfaces.
 To encompassthe joint,thusretainingthe synovial fluid.
 It iswell innervated&providesproprioceptivefeedbackregardingpositionandmovementof
the joint.
LigamentsassociatedwithTMJ
 The mandible isjoinedtothe craniumby*ligamentsof the TMJ .
 Stabilizesthe mandible
* Band of fibroustissue thatconnectsbones
Temporomandibularligament
 a.k.a.LATERAL LIGAMENT

4.  A thickenedbandformedonthe anterolateral side of the capsule.
FUNCTIONS
 Helpspreventexcessive RETRACTION orMOVINGBACKWARDof the mandible
 Helpspreventexcessive LATERALorMEDIAL movementof the condyle outof the fossa.
 ONLY ligamentthatgivesDIRECTSUPPORTto the TMJ capsule
Accessoryligaments
 These ligamentsdonothave a directrelationshipwithmandibulararticulation,althoughthey
may stabilize the articularsystemduringjaw movement.
1. Sphenomandibularligament
A remnantof the embryoniclowerjaw,MECKEL’SCARTILAGE.
Thickenedfibrousbandconnectingthe spine of the sphenoidwithlingualof mandible.
2. Stylomandibularligament
Connectsthe styloidprocesstothe mandibularangle
 JOINT
 a site of junctionorunionbetweentwoormore bone
 Two bone joinedtogethertoallow movementbetweenthose bones
5 typesof joints
1. syndesmosis
A jointinwhichtwobonesare boundtogetherby FIBROUS TISSUE only
*amphiarthrosis –slightlymoveable joint
Ex:
ANKLE JOINT
2. synchondrosis
Jointwhere twobonesare joinedtogetherby CARTILAGE
Very STIFF andSTRONG joint
Ex:
STERNOCOSTAL JOINT– jointwhere the ribsmeetthe sternum
3. synostosis
A jointthathas become obliteratedbybonyunion
Ex:
CRANIAL SYNOSTOSIS
4. symphysis
Jointwhere twoopposingsurfacesare coveredby hyaline cartilage andjoinedby
fibrocartilage and strong fibroustissue
amphiarthrosis

5. Ex:
PUBIC SYMPHYSIS
5. synovial
A jointwhere twoopposingsurfacesare coveredby cartilage (hyaline orfibrocartilage) and
joinedperipherallybyafibroustissue capsule enclosing the jointcavitywhichcontains
synovial fluid.
Ex: ?????????????
 SYNOVIUM/SYNOVIALFLUID
 A specializedtissue whichprovideslubricationandnutritiontothe innerjointtissues
 clear,lubricating,viscousfluid(like eggwhite)
MASTICATION
 Act of chewingfood.
 Representsthe INITIALSTAGEof digestion.
 It isan enjoyable activityutilizingthe sensesof taste,touchandsmell.
 Masticationmay have a relaxingeffectby decreasingmuscle tonusandfidgeting.
 It has beendescribedashavingasoothingquality.
 It is a complexfunctionthat utilizesnot onlythe muscles,teeth,and periodontal supportive
structures but also the lips,cheeks,tongue,palate and salivary glands
The complete chewingstroke hasamovementpatterndescribedas
TEAR-SHAPED
PHASEOF CHEWING STROKE
 1. OPENING PHASE
 The mandible dropsdownwardfromthe intercuspalpositiontoapointwhere the
incisal edgesof the teethare about16 to 18 mm apart
 Thenit moveslaterally5to6 mm fromthe midlineasthe closingmovementbegins.
 2. CLOSING PHASE
 A. CRUSHING PHASE
firstphase of closure whichtrapsfoodbetweenthe teeth
B. GRINDINGPHASE

6. In thisphase,the teethare sopositionedthatthe buccal cuspsof the mandibularteethare
almostdirectly UNDERthe buccal cuspsof the maxillaryteethonthe side towhichthe mandiblehas
shifted
FORCESOF MASTICATION
 Maximal bitingforce thatcan be appliedtothe teethvariesfromindividual to individual.
 MALE 118- 142 lb/ 53.6 – 64.4 kg
 FEMALE 79- 99 lb/ 35.8 – 44.9 kg
 Range of maximal amountof force appliedtoamolar isusuallyseveral timesthatwhichcanbe
appliedtoan incisor.
 FIRST MOLARS 91 -198 lb
 Range of maximal amountof force appliedtoamolar isusuallyseveral timesthatwhichcanbe
appliedtoan incisor.
 FIRST MOLARS 91 -198 lb/ 41.3 – 89.8 kg
 CENTRAL INCISORS29 -51 lb/
13.2 -23.1 kg
SWALLOWING/ DEGLUTITION
 It isa seriesof coordinatedmuscularcontractionsthatmove a bolusof food fromthe oral
cavitythroughthe esophagustothe stomach.
Factors that influence the decisiontoswallow
 Degree of finenessof the food
 Intensityof the taste extracted
 Degree of lubricationof the bolus
Stabilizationof the mandibleisanimportantpartof swallowing.
Duringswallowing,the lipsare closed,sealingthe oral cavity.
The teethare broughtup intotheir maximumintercuspal postion,thusstabilizingthe mandible.
SOMATICSWALLOW
 The NORMAL ADULT swallowutilizingthe teethformandibularstability.

7. INFANTILESWALLOW/ VISCERALSWALLOW
 Whenteethare not present,asinthe infant,the mandible isbracedbyothermeans.
 The mandible isbracedbyplacingthe tongue forwardandbetweenthe dental archesorgum
pads.
FREQUENCY OF SWALLOWING
 24 hr period – 590 times
 Breakdown
 Eating– 146 cycles
 BetweenmealswhileAWAKE–394 cycles
 Sleeping–50 cycles
SPEECH
 It occurs whena volume of airisforcedfrom the lungs by the diaphragmthroughthe larynx and
oral cavity.
 Because speechiscreatedbythe release of airfromthe lungs,itoccurs during the EXPIRATION
STAGE OF RESPIRATION
SOUNDSAND STRUCTURES
 LIPS – LettersM, B andP
 TEETH – S sound
 TONGUE & PALATE– letterD
 “TH” soundisproducedwhenthe tongue touchesthe maxillaryincisors.
 F & V – the lowerliptouchesthe incisal edgesof the maxillaryteeth
 K & G – posterior portionof the tongue risestotouch the softpalate
Central patterngenerator(CPG)
 A pool of neuronswithinthe brainstemthatcontrol rhythmicmuscle activitiessuchas
breathing,walkingandchewing.
Musclesof mastication and physiologyof the masticatory system

8. Muscle
 a band or bundle of fibroustissue inahumanor animal bodythat has the abilitytocontract,
producingmovementinormaintainingthe positionof partsof the body.
 Provideslocomotionforsurvival
 Made up of muscle fibers
Typesof muscle fiberaccordingtothe amountof MYOGLOBIN
MYOGLOBIN
a red proteincontaining*heme thatcarriesandstoresoxygeninmuscle cells.Itisstructurally
similartoa subunitof hemoglobin.
*heme – an iron-containingcompound
1. Slow/ type 1
 fiberswithHIGHER concentrationof myoglobin
 DEEPER RED
 Capable of SLOW but SUSTAINED contraction
 Theyhave well-developedaerobicmetabolism;therefore,
 RESISTANT to fatigue
2. Fast / type 2
 FiberswithLOWERconcentrationof myoglobin
 WHITER
 FEWER mitchondriaandrelymore on ANAEROBIC activityforfunction
 Capable of quick contraction but they fatigue more rapidlythan slow fibers
 All skeletal musclescontainamixture of fastandslow fibers,reflectingof theirfunctions
 Musclescalledupontoresponed QUICKLY are made up predominantlyof WHITEfibers(type II
/FAST)
 MusclesneededforSLOW,CONTINUOUSactivityhave higherconcentrationsof RED fibers
(type I / SLOW)

9. MUSCLES OF MASTICATION
1. MASSETER
RECTANGULAR musclesthatextendsfromthe zygomatic archandextendsdownwardtothe
lateral aspectof the lowerborderof the ramusof the mandible.
 Function: ELEVATION of the mandible
 It isa powerful musclethatprovidesthe force necessarytochew efficiently.
2. TEMPORALIS
Large FAN-SHAPEDmuscle thatoriginatesfromthe temporal fossaandthe lateral surface of the
skull.
PART DIRECTION OF FIBERS
 ANTERIOR VERTICALLY
 MIDDLE OBLIQUELY
 POSTERIOR HORIZONTALLY
 Function: ELEVATION of the mandible
 Because of the angulationof itsmuscle fibersvaries,itiscapable of coordinatingCLOSING
movements.
 Therefore,itisa significantPOSITIONINGmuscle of the mandible
3. MEDIAL/INTERNALPTERYGOID
Originatesfromthe pterygoidfossaandextendsdownward,backwardandoutwardalongthe
MEDIAL surface of the mandibularangle
 Function: ELEVATION and PROTRUSION of the mandible
4.LATERAL/EXTERNALPTERYGOID
 Made up of two distinctanddifferentmuscleswithopposite functions
a. Inferiorlateral pterygoid
Originatesatthe OUTER surface of the lateral pterygoidplate andextendsbackward,upward
and outwardto the NECKof the condyle
ACTIVEduringOPENINGof the mandible
b. Superiorlateral pterygoid
SMALLER thanthe inferiorlateral pterygoid
Originatesfromthe infratemporal surface of the greatersphenoidwing
INACTIVEduringOPENING
 ACTIVEduringthe *POWER STROKE and whenthe teethare heldtogether.

10.  *movementsinvolvingclosure of the mandible againstresistance,asinCHEWINGor CLENCHING
the teeth
MECHANICSOF MANDIBULAR MOVEMENT
MANDIBULAR POSITIONS
 CENTRIC OCCLUSION/ INTERCUSPALPOSITION (acquired/habitual centric)
 Maximumintercuspationof the teeth
 Tooth determinedposition
 CENTRIC RELATION
 Positionof the mandibleinwhichthe condylesare in theiruppermostpositioninthe
mandibularfossaandrelatedanteriorlytothe distal slope of the articulareminence
 It is a jaw-to-jawrelationdeterminedbythe condylesinthe fossa.
 REST POSITION
 A Postural positionof the mandible determinedlargelybyneuromuscularactivityandto
a lesserdegree byviscoelasticpropertiesof the muscles
 May be affectedbyemotionalstressandlocal factorslike sore tooth.
 the usual position of the mandible whenthe
 patientisrestingcomfortably inthe upright
 position andthe condyles are ina neutral
 unstrained position inthe glenoid fossae.
 1-3 mminterocclusal space withinthe INCISORS
 But can range to a maximumof 8-10 mm withoutevidence of dysfunction
Primary/basicmovementsof the TMJ
 ROTATIONAL MOVEMENT
 Hinge movement
 Thisoccurs whenthe mouthopensandclosesarounda fixedpointoraxiswithinthe
condyle.
*the processof turningaroundan axis;movementof abodyabout an axis.

11.  TRANSLATIONAL MOVEMENT
 Lateral movement
 Thisoccurs whenthe mandible movesforward,asinPROTRUSION
*definedasa movementinwhicheverypointof the movingobjectsimultaneouslyhasthe same
directionandvelocity
Bennettmovement
 Appearsduringlateral movements
 The condyle appearstorotate witha slightlateral shiftinthe directionof the movement
 Whenthe mandible movestothe RIGHT,the rightside movement- LATEROTRUSIVE
MOVEMENT (rightworking movement)
 The leftside movesmediallyandlaterally- MEDIOTRUSIVEMOVEMENT(balancing/
nonworkingmovement)
 Maximumopeningmovement –50-60 mm
 Maximumlateral movement –10-12mm
 Maximumprotrusive movement –8-11mm
 Retrusive range (adult&children) –1mm
TMD
TEMPOROMANDIBULARJOINTDISORDER/DYSFUNCTION
 Painand dysfunctionof the masticatorysystem
 SYMPTOMS:
 PAIN
 RESTRICTED MANDIBULAR MOVEMENT
 NOISESOF THE TMJ
TMJ DISLOCATION
 “LOCKJAW”– TMJ is dislocatedanteriorly
TMJ discdisplacement
 Collateral ligamentsloosenortear,allowingthe lateral pterygoidtopull the discanteromedially

12. Tmj noises
CLICK
 Happens withanteriordiscdisplacement
Firstclick:
 OPEN – the discclicksoverthe anteriorlymovingcondyle (condyle clickspastthe thick
posteriorbandof articulardisc)
Secondclick:
 CLOSED – condyle movesposteriorlypastthe disc.Canalsohear thisclickwith
lateral excursionstothe contralateral side
CREPITUS
 Associatedwithosteoarthritisof the condyle (degenerativedisease)
DULL THUD
 Withself-reducingsubluxationof the condyle
 *slippingthe condyle fromitssocket
TMJ / MANDIBULARMOVEMENTS
1. PROTRUSION
2. RETRUSION
3. OPENING
4. CLOSING
5. MEDIAL AND LATERAL EXCURSIONS