temporomandibular joint-development and anatomy

SEMINAR ON

DEVELOPMENT & ANATOMY OF T.M.J

by Dr. Sangeeta Poriya MDS 1ST YEAR Prosthodontics

Temporomandibular joint. IntroductionIntroduction DefinationDefination EvolutionEvolution EmbryologyEmbryology Classification of jointsClassification of joints AnatomyAnatomy Muscles of masticationMuscles of mastication References.References.

INTRODUCTIONINTRODUCTION ““FUNCTION MUST BE UNDERSTOOD FUNCTION MUST BE UNDERSTOOD

BEFORE DYSFUNCTION CAN HAVE BEFORE DYSFUNCTION CAN HAVE MEANING”MEANING”

Masticatory system a functional unit of body Masticatory system a functional unit of body includes TMJ .includes TMJ .

Is responsible for chewing, speaking, Is responsible for chewing, speaking, swallowing etcswallowing etc

It is most complex joint of body. It is most complex joint of body. Hence its functions should be understood Hence its functions should be understood

before resulting in its dysfunction.before resulting in its dysfunction.

TMJ Defination TMJ Defination The articulation between the temporal The articulation between the temporal

bone and the mandible. It is bone and the mandible. It is diarthoidal,bilateral ginglymus joint (GPT).diarthoidal,bilateral ginglymus joint (GPT).

The area where craniomandibular The area where craniomandibular articulation occurs is called the articulation occurs is called the temporomandibular joint.temporomandibular joint.

The TMJ provides hinging movement in one The TMJ provides hinging movement in one plane and is considered as a ginglymoid plane and is considered as a ginglymoid joint.joint.

It also provides gliding movements, which It also provides gliding movements, which classifies it as an arthrodial jointclassifies it as an arthrodial joint

EVOLUTION OF TMJ.EVOLUTION OF TMJ.

Primitive vertebratesPrimitive vertebratesCollection of food led to dev of jaws Collection of food led to dev of jaws along with fins.along with fins.

Amphibians and reptilesAmphibians and reptilesGreater demand on jaw mechanics Greater demand on jaw mechanics to adjust to new habitat.to adjust to new habitat.

EVOLUTION OF TMJ.EVOLUTION OF TMJ.

Increasing efficiency of the feeding Increasing efficiency of the feeding mechanism- critical factor in mechanism- critical factor in vertebrate evolution.vertebrate evolution.

Earliest functional activity of TMJ.Earliest functional activity of TMJ.

prehension Control size of mass of food entering alimentary tract

EVOLUTION OF TMJ.EVOLUTION OF TMJ.

Mammals Mammals Greater benefit from food source Greater benefit from food source Modification in jaws, joint, dentitionModification in jaws, joint, dentition HumansHumans Upright posture / bipedal locomotionUpright posture / bipedal locomotion Food collection shifted to jaws.Food collection shifted to jaws.

EVOLUTION OF TMJ.EVOLUTION OF TMJ.

Primitive jaw Primitive jaw joint – reptilian joint – reptilian jointjoint

1.1. DentaryDentary2.2. Quardate(incus)Quardate(incus)3.3. Articulare(malleArticulare(malle

us)us) Dentary –Dentary –

squamosal squamosal joint/mammalijoint/mammalian jaw jointan jaw joint

EVOLUTION OF TMJ.EVOLUTION OF TMJ. Relationship of primitive jaw and cranial base.Relationship of primitive jaw and cranial base.

AMPHISTYLIC SUSPENSIONAMPHISTYLIC SUSPENSION upper jaw connected to cranium.upper jaw connected to cranium.

HYOSTYLIC SUSPENSIONHYOSTYLIC SUSPENSION Only lower jaw connected to cranium.Only lower jaw connected to cranium.

Behind eye

Hyomandibular cartilage attached to cranium

EVOLUTION OF TMJ.EVOLUTION OF TMJ.

STREPTOSTYLIC SUSPENSIONSTREPTOSTYLIC SUSPENSION Great degree of movement between Great degree of movement between

upper and lower jawupper and lower jaw Assists in swallowingAssists in swallowing

Amphibians and reptiles Amphibians and reptiles Maxillary , pterygoid elements attached Maxillary , pterygoid elements attached

to the craniumto the cranium

EVOLUTION OF TMJ.EVOLUTION OF TMJ.Development of muscles.Development of muscles.

Advanced reptiles – capitii Advanced reptiles – capitii mandibularismandibularis

Increased functional Increased functional activityactivity

Size of dentary bone,Size of dentary bone,heterodont dentitionheterodont dentition Forces directed away from Forces directed away from the jointthe joint Alteration in orientation of Alteration in orientation of

jaw musclesjaw muscles

EVOLUTION OF TMJ.EVOLUTION OF TMJ. Mammal like reptiles - Mammal like reptiles -

PrehensionPrehension Condyle Condyle

clamped by clamped by glenoid glenoid processesprocesses

EVOLUTION OF TMJ.EVOLUTION OF TMJ.Carnivore - cuttingCarnivore - cutting

Well dev caninesWell dev canines Coronoid – largeCoronoid – large Condyle encircled in Condyle encircled in

fossafossa Disc presentDisc present Masseter Masseter

+temporalis –well +temporalis –well devdev

No forward No forward Minimum lateralMinimum lateral

EVOLUTION OF TMJ.EVOLUTION OF TMJ.Rodent - gnawingRodent - gnawing

Incisors Incisors chisel shapedchisel shaped

Ant –post Ant –post oriented oriented glenoid fossaglenoid fossa

Forward Forward +upward +upward movement movement

Well dev Well dev MasseterMasseter

EVOLUTION OF TMJ.EVOLUTION OF TMJ.Herbivore - grindingHerbivore - grinding

Well dev molarsWell dev molars Ascending ramus Ascending ramus

increased heightincreased height Condyle ovalCondyle oval No articular eminenceNo articular eminence Post glenoid processPost glenoid process Disc & capsule presentDisc & capsule present Masseter + temporalis Masseter + temporalis

well devwell dev Lat pterygoidLat pterygoid Lateral movements Lateral movements

prominentprominent

Embryology.Embryology. Primary Jaw jointPrimary Jaw joint

Between Incus and MalleusBetween Incus and Malleus

Persists till 4 months IULPersists till 4 months IUL

Embryology.Embryology. Secondary jaw jointSecondary jaw joint Between the condyle and temporal Between the condyle and temporal

bonebone Differs from other synovial jointsDiffers from other synovial joints

Embryology.Embryology.TMJ - neonateTMJ - neonate

Lax Lax Stability –capsuleStability –capsule Fossa – flatFossa – flat Articular tubercleArticular tubercle absent absent

condyle,no condyle,no fossa/tuberclefossa/tubercle

DEVELOPMENTDEVELOPMENT• Meckel’s cartilage provide skeletal support Meckel’s cartilage provide skeletal support

for development of lower jaw.for development of lower jaw.

• The primary jaw joint The primary jaw joint - Articulation of Meckel’s cartilage with - Articulation of Meckel’s cartilage with Incal cartilage Incal cartilage - exists for 4 months till cartilages ossify - exists for 4 months till cartilages ossify & are incorporated in middle ear.& are incorporated in middle ear. Secondary jaw joint-TMJ begins to form at 3 Secondary jaw joint-TMJ begins to form at 3 months of gestation months of gestation

• Most synovial joints have appeared by 7Most synovial joints have appeared by 7thth wk in utero as a cavitation.wk in utero as a cavitation.

• TMJ arises from 2 widely separated TMJ arises from 2 widely separated centers that grow towards each other.centers that grow towards each other.

• Regions of mesenchymal condensation – Regions of mesenchymal condensation – temporal & condylar blastemas.temporal & condylar blastemas.

• Meniscus is formed- pair of clefts develop Meniscus is formed- pair of clefts develop in interposed condensation of mesenchyma in interposed condensation of mesenchyma which form upper and lower joint cavities.which form upper and lower joint cavities.

• 12 wks in utero- condylar blastema 12 wks in utero- condylar blastema differentiates into a condylar cartilage.differentiates into a condylar cartilage.

• The cartilage is replaced by The cartilage is replaced by membraneous bone & it’s posterior part membraneous bone & it’s posterior part persists in the condyle – site of active persists in the condyle – site of active growth. growth.

• Further adaptation of condylar Further adaptation of condylar morphology- functional & environmental morphology- functional & environmental changes.changes.

• Capsule develops by condensation of Capsule develops by condensation of surrounding mesenchyma- isolates the surrounding mesenchyma- isolates the joint.joint.

Clefting and formation of joint cavity

Formation of condylar + temporal blastema and ossification

CLASSIFICATION OF JOINTSCLASSIFICATION OF JOINTS BASED ON BASED ON

ANATOMICAL ANATOMICAL CHARACTERISTICS CHARACTERISTICS

(Structural (Structural classification)classification)

BASED ON BASED ON FUNCTIONAL FUNCTIONAL CLASSIFICATION: CLASSIFICATION:

( type of movement)( type of movement)

STRUCTURAL CLASSIFICATION:Based on presence or absence of joint cavity:

FIBROUS JOINT:CARTILAGENOUS JOINT:SYNOVIAL JOINT

FUNCTIONAL CLASSIFICATION:SYNARTHROSIS: Immovable jointsAMPHIARTHROSES: Slightly movable jointsDIARTHROSIS: Freely movable joints:

Types of joints.Types of joints.

SUTURE: sutura = seam Fibrous joint composed of thin layer of dense fibrous connective tissue that unites bones of the skull

GOMPHOSIS: to bolt togetherCone shaped peg fits into a socket eg tooth into alveolar bone through periodontal ligament

SYNCHRONDROSIS: syn= together , chondros=cartilageCartilaginous joint in which connective material is hyaline cartilage eg epiphyseal plate

SYNARTHROSIS: Immovable joints

AMPHIARTHROSES: (Slightly movable joints)

SYNDESMOSIS:band /ligament fibrous joint in which there is considerably more fibrous connective tissue than in a suture. The fit of the bones is not so tight. Some amount of flexible movement. EG distal articulation between fibula and tibia

SYMPHYSIS:growing togetherCartilaginous joint in which connecting material is broad flat disc of fibro cartilage EG intervertebral discs.pubic symphysis

DIARTHROSISDIARTHROSIS:: Also known as synovial joints. Presence of Also known as synovial joints. Presence of Synovial cavity and articular cartilage a characteristic feature.Synovial cavity and articular cartilage a characteristic feature...

(Freely movable joints.)(Freely movable joints.)

Based on types of movement:

GLIDING : eg intercarpal jointHINGE eg: elbow joint/ ankleCONDYLOID eg: joint between radius and carpalsPIVOT eg: joint between atlas and axisSADDLE eg : joint between carpus and thumbBALL AND SOCKET: eg : shoulder/ hip joint

BILATERAL SYNOVIAL GINGLYMOID (DIARTHRODIAL ) COMPOUND JOINT

Synovial joints.Synovial joints.

Permits significant movementPermits significant movement Synovial cavity Synovial cavity Synovial membraneSynovial membrane Synovial fluidSynovial fluid hyaline cartilage hyaline cartilage capsulecapsule

Synovial joints.Synovial joints. Uniaxial/biaxial /multiaxialUniaxial/biaxial /multiaxial Planar /ginglymoid Planar /ginglymoid

/pivot/condyloid/saddle/ball and socket/pivot/condyloid/saddle/ball and socket

Hiltons lawHiltons law

Muscles acting upon a joint have same Muscles acting upon a joint have same nerve supply as jointnerve supply as joint

SYNOVIAL JOINT:Specialized endothelial cells form a synovial lining and forms the synovial fluid which fills both joint cavities and performs two functions:

Medium for metabolic exchange: as the articular surfaces are avascularLubricant during function:

Two mechanisms by which lubrication occurs:

BOUNDARY LUBRICATION: primary mechanism;synovial fluid forced from one region to

another by movement of the joint itself.

WEEPING LUBRICATION:The articular surfaces itself absorb some amount of synovial fluid

which due to the pressure during function is forced in and out of the articular tissues and provided the medium for metabolic exchange. This occurs only during compression but not all other movements.

Functions of synovial Functions of synovial fluid.fluid.

NutritionNutrition

LubricationLubrication1.1. Boundary lubrication Boundary lubrication 2.2. Weeping lubricationWeeping lubrication

• Minimizes frictionMinimizes friction

COMPONENTS OF THE TMJ:CONDYLAR HEAD

GLENOID FOSSA

ARTICULAR EMINENCE

MUSCLES OF THE TMJ:

MUSCLES OF MASTICATION

SOFT TISSUE COMPONENTS:

ARTICULAR DISC

JOINT CAPSULE

LIGAMENTS

ARTERIAL AND NERVE SUPPLY TO THE JOINT

CONDYLAR HEADCONDYLAR HEAD The oval condylar head is shaped like a rugby ball The oval condylar head is shaped like a rugby ball The lateral pole is slightly at a a lower level to the The lateral pole is slightly at a a lower level to the

medial polemedial pole The long axis makes a line of 140 degrees with the line The long axis makes a line of 140 degrees with the line

joining the external acoustic meatusjoining the external acoustic meatusThe cartilage layer is thicker laterally and posteriorly suggesting the growth direction is more active in these areas.Anteromedially the cartilage becomes thin early and bone forms in this region of attachment of the lateral pterygoid

The glenoid fossa:

Shallow oval depression in the infratemporal area

Bone of the deepest part is quite thin and shows that this part of the joint is not designed to play an active functional role in the joint.

The articular eminence:

The two slopes of the articular eminence are considered to be a functional part of the joint.

The posterior slope resorbs with edentulism

Muscles of mastication: mastication is a a harmonious and skillful activity which requires the presence and co ordination of not only the muscles of mastication but also the supra infrahyoid muscles, and the facial muscles

Muscles of mastication.Muscles of mastication. Masseter.Masseter. Temporalis.Temporalis. Medial pterygoid.Medial pterygoid. Lateral pterygoid.Lateral pterygoid. Digastric.Digastric.

The The Temporalis.Temporalis.

The strongest of the masticatory muscles

Divided into three parts

Well developed in carnivores and animals requiring a strong bite force

It elevates the mandible when it contracts.

Contraction of the anterior part raises the mandibleContraction of the middle part elevates and retrudes the mandible

Temporalis muscletendon

The The masseter.masseter.

Powerful elevator muscle

Superficial muscle helps in protruding the mandible

Deep portion helps in stabilizing the condyle against the articular eminence when biting in a protruded position.

Unilateral movement helps in lateral movement of the mandible

Well developed in ruminantsDeep portion

Superficial portion

The medial pterygoid muscle.The medial pterygoid muscle.Originates from the pterygoid fossa and extends downwards backwards and outwards to insert in the medial side of the ramus of the mandible forming a sling along with the masseter at the angle of the mandible.

It assists in closing of the jaw and contraction of the muscle also causes protrusion.

The lateral pterygoid muscle.The lateral pterygoid muscle.Superior lateral pterygoid muscleOriginates form the infratemporal surface of the greater wing of the sphenoid, extends almost horizontally backward and outward to insert on the articular capsule the disc and the neck of the condyle.60 to 70% of the fibres attach to the condyle and the rest to the disc. Plays an active role not during opening but during closing (power stroke)

Originates at the outer surface of the lateral pterygoid plate and extends backward upward and outward to insert into the neck of the condyle.When there is bilateral contraction the condyles are pulled down the articular eminences and the mandible is protruded.

Unilateral contraction causes a mediotrusive movement of that condyle and lateral movement of the mandible to the other side

. The inferior lateral pterygoid is active during opening in contrast to the superior part.

Other muscles Other muscles coordinating Mandibular coordinating Mandibular

movements.movements.

Summary of Summary of mandibular mandibular movements movements & muscles & muscles involvedinvolved

Soft tissue components of the Soft tissue components of the TMJ.TMJ.

Articular disc, capsule, ligaments and muscles

ARTICULAR DISC. ARTICULAR DISC. AttachmentsAttachments

Retrodiscal tissue

Temporal bone

condyle

Capsular ligament + superior LPM

Medially + laterally attached to the capsule which divides joint cavity

Articular disc

Superior head of the lateral pterygoid

Inferior head of the lateral pterygoid

Articular Disc.

ARTICULAR DISC.ARTICULAR DISC.

ANTERIOR BORDER

INTERMEDIATE ZONE

POSTERIOR BORDER

SAGITTAL VIEW

ANTERIOR VIEW

ARTICULAR DISC.ARTICULAR DISC. Articulating surfaces are covered with Articulating surfaces are covered with

fibrous tissuefibrous tissue

Synovial lining /fluidSynovial lining /fluid

Upper joint cavity

Lower joint cavity

ARTICULAR DISC.ARTICULAR DISC. Devoid of blood vessels and nerveDevoid of blood vessels and nerve

Morphology maintainedMorphology maintained

Flexible and adaptable to functional Flexible and adaptable to functional demandsdemands

ARTICULAR DISC. Divides the joint into two compartments

According to Rees divided into 4 parts: Anterior band –thickened Intermediate band- narrow and thin Posterior band – again thick Bilaminar zone-

upper part having ELASTIC fibres and attaching to the posterior margin of the glenoid fossa and the tympano squamous fissure,forms the posterior border of the upper compartment.lower part: mainly collagen fibres and attached to neck of condyle.Posterior border of the lower compartment.

Articular disc

Joint capsule

Lateral ligament of the

TMJ

Articular disc has the shape of a laterally wide ovoid.In frontal section the disc is wedge shaped thicker medially and thinner laterally

Articular disc

Joint capsule

The intermediate band: It is the functional zone of the disc Blood vessels are rarely found here in the intermediate part of the disc

Unlike other synovial joints the TMJ condyle and temporal bone do not fit together in the absence of the disc.

The disc fills the wedge like gap and stabilizes the join during rotation and translation.

Normally there is no space between the disc and the articulating bones except the antero- superior and inferior recesses and the postero -superior and inferior recesses.

These recesses are filled with synovial fluid and movement of the joint squeezes them into the other recesses so a thin film of lubricant is obtained on the moving parts.

The disc also acts as a shock absorber.

They are made up of collagenous connective tissue which do not stretch and do not actively participate in the normal function They act as guide wires restricting certain movements while permitting certain others.They restrict movement mechanically as well as through neuro muscular reflex activity.Ligaments do not stretch. They can be elongated by traction forces but once they have been elongated joint activity is usually compromised.

LIGAMENTS:LIGAMENTS:

Ligaments of TMJ.Ligaments of TMJ. Collateral ligaments(Discal).Collateral ligaments(Discal). Capsular ligamentsCapsular ligaments Temporomandibular ligamentsTemporomandibular ligaments

Sphenomandibular ligamentsSphenomandibular ligaments stylomandibular ligamentsstylomandibular ligaments

Functional ligaments

Accessory ligaments

The collateral ligaments (discal).

Attach the medial and lateral poles of the articular disc to the poles of the condyle. They are two in number:- medial and lateral .They function in allowing the disc to move passively with the condyle as it glides anteriorly and posteriorly.

They also allow the disc to be rotated anteriorly and posteriorly on the articular surface of the condyle..

Thus these ligaments are responsible for the hinging movements of the condyle which occurs in the lower compartment.

Capsular ligament.The capsular ligament encompasses the joint retaining the synovial fluid. It is fibroelastic, very well vascularised and well innervated and provides proprioceptive feedback regarding the position and movement of the joint..

Capsular ligament

Lateral ligament

Temporomandibular Temporomandibular ligament.ligament.

Reinforces the lateral Reinforces the lateral aspect of capsular aspect of capsular ligamentligament

Outer oblique portion Outer oblique portion Inner horizontal Inner horizontal

portionportion OOP- Prevents OOP- Prevents

excessive dropping of excessive dropping of condyle / limits condyle / limits extent of mouth extent of mouth openingopening

IHP

TM ligament.It has two parts outer oblique and an inner horizontal.

The outer part extends from the articular tubercle to the neck of the condyle

The outer oblique part has the following functions: It restricts excessive dropping of the condyle and therefore

limits the normal opening of the mandible.Secondly during opening of the mouth, the condyle rotates

till this ligament becomes tight as its point of insertion is rotated posteriorly. When it becomes taut the neck cannot rotate any further.

This unique feature is found only in humans preventing excessive rotation for the mandible from impinging on the vital mandibular and retromandibular structures behind the jaw.

the inner horizontal part extends backwards from the articular tubercle to insert into to the lateral pole of the condyle and posterior part of the articular disc.

Function:

The inner horizontal portion protects the posterior retrodiscal tissues from trauma and also prevents the lateral pterygoid muscle from over lengthening.

Accessory ligaments:

Sphenomandibular ligament

Stylomandibular ligament.

It becomes taut when the mandible is protruded and thus limits the excessive protrusive movements of the mandible.

Sphenomandibular Sphenomandibular ligament.ligament.

Extents from Extents from spine of spine of sphenoid to sphenoid to lingulalingula

No limiting No limiting effects on effects on mandibemandibe

Stylomandibular Stylomandibular ligament.ligament.

Extends from Extends from the styloid the styloid process to the process to the angle + post angle + post border of ramusborder of ramus

Limits excessive Limits excessive protrusive protrusive movementmovement

Vascular supply:

Superficial temporal arteryMiddle meningeal arteryMaxillary artery

Innervation:

Auriculotemporal nerveDeep temporal and masseteric nerve

Others : deep auricular , anterior tympanic, ascending pharyngeal

VASCULAR SUPPLY AND INNERVATION OF THE JOINT

Blood SupplyBlood Supply Branches from superficial temporal Branches from superficial temporal

and maxillary arteryand maxillary artery

Nerve supplyNerve supply a. Auriculotemporal nervea. Auriculotemporal nerve b. Masseteric nerveb. Masseteric nerve

RefrencesRefrences Jeffrey P .Okeson, Management of Jeffrey P .Okeson, Management of

temporomandibular disorder and temporomandibular disorder and occlusion, 5occlusion, 5ththedition;8-26; 258-74. edition;8-26; 258-74.

Gray’s Anatomy 34Gray’s Anatomy 34thth edition;459-61. edition;459-61. White & Pharoah; Oral radiology principles White & Pharoah; Oral radiology principles

and interpretation,5and interpretation,5thth edition;538-49. edition;538-49. UdoStratmann, et al Journal of UdoStratmann, et al Journal of

Prosthodontic Dentistry 2000 (3):548-54; Prosthodontic Dentistry 2000 (3):548-54; CLINICAL ANATOMY AND PALPABILITY OF THE CLINICAL ANATOMY AND PALPABILITY OF THE INFERIOR LATERAL PTERYGOID MUSCLEINFERIOR LATERAL PTERYGOID MUSCLE