temporomandibular joint/ fellowships in orthodontics

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TEMPOROMANDIBULAR JOINTTEMPOROMANDIBULAR JOINT

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

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Temporomandibular joint

Types of jointsEmbryologyFunctional anatomyMuscles of masticationBiomechanics of TMJEvolution


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Types of jointsTypes of joints

Depending on the types of tissues involved

1. Fibrous joints

2. Cartilaginous joints

3. Synovial joints


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Fibrous jointsFibrous joints

1. Sutures

2. Gomphosis

3. syndesmosis


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Cartilaginous jointsCartilaginous joints

1. Primary

2. secondary


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Synovial jointsSynovial joints

Permits significant movementSynovial cavity Synovial membrane Synovial fluidhyaline cartilage capsule


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Synovial jointsSynovial joints• Uniaxial/biaxial /multiaxial• Planar /ginglymoid

/pivot/condyloid/saddle/ball and socket

• Hiltons law

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


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TMJTMJ

GINGLYMOID

DIARTHROIDAL

SYNOVIAL

TRUE COMPOUNDwww.indiandentalacademy.com

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TMJ OTHER SYNOVIAL JOINTS

2 BLASTEMA-Temporal-Condylar

Cavity formation within a single blastema

Fibrous cartilage at the articular surfaces

Hyaline cartilage at the articular surfaces.

Cartilage acts as growth centre

Does notwww.indiandentalacademy.com

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Types of jointsEmbryologyFunctional anatomy Muscles of masticationBiomechanics of TMJ Evolution


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EmbryologyEmbryology Primary Jaw joint

Homologous reptiles. -maeckels cartilage

functions as the primary joint.mouth opening begins

Persists till 4 months IUL 6 weeks iu.-Membranous bone forms lateral to meckels cartilage at-body and ramus


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10th week-the joint forms both malleo- incudal and Definite jaw joint move together in synchrony for 8 weeks in fetal life. The accessory mandibular condylar cartilage develops as 1st blastema..

Grows towards the later developing temporal blastema.

EmbryologyEmbryology


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-Lateral pterygoid develops medial to future condyle and causes movement at through the primary meckelian joint.

Fossa Interposed connective tissue becomes thinner.

Two clefts develop in the fibrous connective tissue forming two joint cavities.



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1st inferior compartment2nd superior compartment.Invading synovial membrane compartment.Cavitation.Early immobilizationEarly functional activity



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Clefting and formation of joint cavity

Formation of condylar + temporal blastema and ossification


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Articular disc-biconcave.Ventarally –lpmDorsally –the superior laminae,inferior

laminae



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Fossa – flatArticular tubercle Absent condyle,no

fossa/tubercle


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3 components that make up the masticatory system

1. Maxillae 2. Mandible3. Temporal bone


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TMJTMJ

GINGLYMOID

DIARTHROIDAL

SYNOVIAL

TRUE COMPOUND


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FUCTIONAL ANATOMYFUCTIONAL ANATOMY

SQUAMOUS PART OF TEMPORAL BONE

ARTICULAR DISC

CONDYLE


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FUCTIONAL ANATOMYFUCTIONAL ANATOMYcondylecondyle

Poles of condyle

Convex articulating surface

Articulating surface –ant and post


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FUCTIONAL ANATOMYFUCTIONAL ANATOMYTemporal boneTemporal bone

Squamous part

Concave-Glenoid fossa

Squamotympanic fissure

Articular eminence

Roof - thin


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ARTICULAR DISCARTICULAR DISC

ANTERIOR BORDER

INTERMEDIATE ZONE

POSTERIOR BORDER

SAGITTAL VIEW

ANTERIOR VIEWwww.indiandentalacademy.com

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ARTICULAR DISCARTICULAR DISC

Devoid of blood vessels and nerve

Flexible and adaptable to functional demands


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Attachments of the articular disc-Attachments of the articular disc-

Retrodiscal tissue- Loose connective tissue Rich blood and nerve

supply Bilaminar zone

Superior retrodiscal lamina(elastic fibres)

Inferior retrodiscal lamina(collagenous fibres)


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Retrodiscal tissue

Temporal bone

condyle

Capsular ligament + superior LPM

Medially + laterally attached to the capsule which divides joint cavity

Attachments of the articular discAttachments of the articular disc - -


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ARTICULAR DISCARTICULAR DISC Articulating surfaces are covered with fibrous tissue

Synovial lining /fluid

Upper joint cavity

Lower joint cavity


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Functions of synovial fluidFunctions of synovial fluidI. Nutrition

II. Lubrication1. Boundary lubrication (moving joint)2. Weeping lubrication(compressive

forces)

• Minimizes friction


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Ligaments of TMJLigaments of TMJ Limit joint movement1. Collateral ligaments2. Capsular ligaments3. Temporomandibular ligaments

4. Sphenomandibular ligaments5. Stylomandibular ligaments

Functional ligaments

Accessory ligaments


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Collateral (discal) ligamentCollateral (discal) ligament

1. Medial discal 2. Lateral discal Divide joint medio laterally Allows passive movement of

the disc Permits anterior + posterior

rotation of disc on condyle Blood vessels + nerves Proprioception


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Capsular ligamentCapsular ligament

Surrounds the TMJResists forces that

separate the articulating surfaces

proprioception


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Temporomandibular ligamentTemporomandibular ligament

1. Outer oblique portion 2. Inner horizontal portion Reinforces capsular

ligament OOP- Prevents

excessive dropping of condyle / limits extent of mouth opening

IHP


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Temporomandibular ligament-Temporomandibular ligament-actionaction

• Limits rotational opening

• Seen only in humans – erect posture

• Prevents damage to submandibular / retromandibular structures


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Temporomandibular ligamentTemporomandibular ligament

IHP- Limits posterior

movement of condyle and disc

Prevents damage to the retrodiscal tissue


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Sphenomandibular ligamentSphenomandibular ligament

Extents from spine of sphenoid to lingula

No significant limiting effects on mandibe


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Stylomandibular ligamentStylomandibular ligament

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

Limits excessive protrusive movement


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Muscles of masticationMuscles of mastication

MasseterTemporalisMedial pterygoidLateral pterygoidDigastric

Muscles of masticationMuscles of mastication


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The masseterThe masseter

Origin insertion &

direction

Function –elevation


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The temporalisThe temporalis

Origin & insertionFunction –

elevation

retrusionwww.indiandentalacademy.com

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The medial pterygoidThe medial pterygoid

Origin & insertion

Function - elevation

Protrusion Muscle sling with Masseter

U/l - mediotrusivewww.indiandentalacademy.com

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The lateral pterygoid- inferior The lateral pterygoid- inferior portionportion

Origin & insertion

Function-protrusion

U/l – mediotrusive

With depressors – downward+forwardwww.indiandentalacademy.com

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The lateral pterygoid- superior The lateral pterygoid- superior portionportion

Infratemporal surface of greater wing of sphenoid – capsule ,disc ,neck

Active during power stroke

Closure with elevators


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The lateral pterygoidsThe lateral pterygoidsExert medial pull on disc & condyle


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The digastricusThe digastricus

Function– b/L contraction depression of mandible with fixed hyoid bone

Raises hyoid –swallowingwhen mandible is fixedwww.indiandentalacademy.com

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Other muscles coordinating Other muscles coordinating Mandibular movementsMandibular movements

Coordinated movements of-

SupahyoidInfrahyoid Posterior neck muscles


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Summary of Summary of mandibular mandibular

movements & movements & muscles muscles involvedinvolved


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Biomechanics of TMJBiomechanics of TMJ Based on structure and function can be divided

into 2 systems First joint system -Inferior joint cavity• Second joint system -Superior joint cavity


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Biomechanics of TMJBiomechanics of TMJ

Articular disc as meniscus

1. Not a determinant of joint movement2. Attached on one side and unattached on

the other.3. Freely extends into the joint space


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TMJ - no attachment Yet stable due to musclesResting stage – tonusIncrease muscle activity - increase

interarticular pressureAbsence of pressure - dislocate


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Biomechanics of TMJBiomechanics of TMJDisc space varies with

pressure Increased – disc space

narrows Decreased – space widensCondyle on anterior /

posterior zone


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Biomechanics of TMJBiomechanics of TMJMandibular opening and closingMandibular opening and closing

SRL –retract the disc

Closed joint position – relaxed

Stretched – during opening


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Biomechanics of TMJBiomechanics of TMJ Mandibular opening and closingMandibular opening and closing

SLP – protractor of the disc

ILP – protractor of condyle

So forward movement – articular cartilage – disc morphology.

opening

closingwww.indiandentalacademy.com

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Biomechanics of TMJBiomechanics of TMJclosed mouth resting closed mouth resting

positionposition SLP - tonus SLP > SRL Resting position-interarticular pressure

reduced,disc space wide. Disc rotated anteriorly Condyle contacts intermediate & post zone Open mouth –SRL stretches , SRL > SLP Disc

rotated posteriorly


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Biomechanics of TMJBiomechanics of TMJPower stroke / chewingPower stroke / chewing

pressure reduced on biting side Fulcrum around food Pressure increased on contralateral side Same side – separation – dislocation SLP - active ,positions disc anteriorly on condyle Stabilizes joint Teeth approach intercuspation –pressure increases Mechanical post rotation – intermediate zone-

resting positionwww.indiandentalacademy.com

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Biomechanics of TMJBiomechanics of TMJ Points to remember

1. Ligaments do not actively participate in function of TMJ

2. Ligaments do not stretch3. Articular surfaces must maintain constant

contact


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Adaptive morphology is dependent upon- Locomotion

Feeding


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EVOLUTION OF T.M.JEVOLUTION OF T.M.J

Primitive vertebratesCollection of food led to dev of jaws along

with finsAmphibians and reptiles Greater demand on jaw mechanics to adjust

to new habitat


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Mammals Greater benefit from food source Modification in jaws, joint, dentition

Humans Upright posture Bipedal locomotion Shrinkage of human face


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1.Prehension

2.Control size of mass of food entering alimentary tract

-sharp cusps

-force in a direction effective

-sharp cutting edges

Earliest functional activity of Earliest functional activity of TMJTMJ


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Jaw joint has been classified into-Jaw joint has been classified into-

1.Primitive jaw joint\reptilian jaw joint\quadrate-articular occlusion

2.Mamalian type of jaw joint\dentary squamosal articulation\early TMJ


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Primitive jaw joint –reptilian joint

Maxillae Palatoquadrate barMandible Hyomandibular(stapes) Quardate(incus) Articulare(malleus) DentaryDentary –squamosal

joint/mammalian jaw joint


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Most primitive jawFlexible plate of fibrocartilage connects the

upper and lower cartilagenous jaws(shark) -1st arch no longer forms the gill and grows

under the brain as palatoquadrate bar.It extends front to back under the base of the skull to join the lower jaw(maeckels cartilage )at the epiceratobranchial joint.

The second arch modified to support the first arch in its function-hyomandibular cartilage.


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AMPHISTYLIC SUSPENSION Upper jaw connected to cranium-2 places

Behind eye

Hyomandibular cartilage attached to cranium

Relationship of primitive jaw and Relationship of primitive jaw and cranial basecranial base


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HYOSTYLIC SUSPENSION

. Hyomandibular element was the only articulation between the jaws and the cranial base


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Autostylic suspension Upper jaws are firmly fused to the cranial base.eg

chimera



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STREPTOSTYLIC SUSPENSIONGreat degree of movement between jaws

and cranial baseAssists in swallowing Reptiles and modern snakesThe pterygopalatine component can remain

clamped onto the animal while other parts shifted their grip



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Amphibians and higher vertibratesMaxillary palatine , pterygoid elements

attached to the cranium,but hyomandibular (stapes) ,quadrate (incus) and articulare (malleus) continued to form movable joint.

Mobility of upper and lower jawsMobility of upper and lower jaws


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Bones dentine and enamelBones dentine and enamel

Bones dentine and enamel first appeared in fossil records as-dermal plates of primitive creatures.

In primitive sharks the denticles extend into the jaws to give rise to teeth. The dermal bones sank into the skin . They gained attachment to muscles.


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`̀ Pre maxillae-with ant teeth Maxillae – with marginal teeth Jugal bone-lower orbit Quadrato-jugal Quadrate Squamosal bone

The bones at the margin of upper jaw-


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Maeckels cartilage(core of the lower jaw)became invested in 8 separate dermal bony plates.

Dentary(with marginal row of teeth) 2 spenials Angular Surangular Prearticular 2 coronoid bones

Lower jawLower jaw


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Development of musclesDevelopment of musclesAdvanced reptiles – capitii

mandibularis and pterygoid muscles.

Well divided musclesIncreased functional

activitySize of dentary

bone,heterodont dentition


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Development of musclesDevelopment of muscles

Alteration in orientation of jaw muscles

Forces directed away from the joint


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Development of inter-articular Development of inter-articular discdisc

Primitive joint did not have any cartilage.Lateral part of the muscle that extended

from the pterygoid region to the maeckels cartilage gives rise to the cartilage.


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Functional activity of the Functional activity of the mamalian TMJmamalian TMJ

PrehensionTearingCrushing


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Prehension

Condyle clamped by glenoid processes

Reptiles have enlarged teeth at corners


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PrehentionPrehention

1. Speed -temporalis muscle2. Constant reproduction of jaw closure -interlocking canines -hinge like tmj


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TearingTearing

Combination of –muscles controlling the dentition and movement of the jaws

–neck muscles Carnivore dentition Grazing activity of the

ungulate


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Crushing Crushing

1. Slicing (carnivores)2. Gnawing (rodent incisors)3. Grinding (herbivores)


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Slicing in carnivoreSlicing in carnivore Well dev canines Condyle encircled in fossa

at level of occlusal surface of mandibular teeth

Coronoid – large Disc present Right and left halves are

not united at the symphysis.


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Slicing in carnivoreSlicing in carnivore

Masseter +temporalis –well dev

Zygomatic arch-strong No forward Minimum lateral


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Rodent - gnawingRodent - gnawing

Incisors chisel shapedContinuous erruptionDifferential wearAnt –post oriented

glenoid fossaNo side to side

movement


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Well dev molars Ascending ramus increased

height Condyle oval No articular eminence Slight post glenoid process Capsule is present. Anisognathous-do not

occlude simultaneously.

Herbivore - grinding


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Disc & capsule present

Masseter + temporalis well dev but not as much as the carnivores.

Lat pterygoid Lateral movements prominent

Herbivore - grinding


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References References

JEFFEREY P OKESONGUNNAR E CARLSSON RICHARD TEN CATEGRAYS ANATOMY


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temporomandibular joint/ fellowships in orthodontics

Education