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ning

THE TEMPROMANDIBULAR JOINT(TMJ)

By:Mohammad Shafi Dar

INTRODUCTION

Temporomandibular joint Is an essential joint of the face, required

for mouth opening and closing, mastication, and speech

a synovial joint formed by the mandibular fossa of the temporal bone and the head of the condyle of the mandible with an intervening articular disc

The joint surface is completely covered by a thick fibrous capsule that allows for range of movements

INTRODUCTION

Lateral pterygoid muscle raphe

Lower head of lateral pterygoid muscle

Anterior band of articular disc

Mandibular condyle (head)

Posterior band of articular disc

Posterior disc attachment

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Temporomandibular Joint (TMJ) - Histology

Composed of Condyle Mandibular fossa Articular capsule Articular disc Synovial tissue

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Mandibular Condyle

Approx. 20 x 10 mm (ML x AP)

Perpendicular to the ascending ramus of mandible

Made up of inner core of cancellous bone and outer core of compact bone

Articulating surface of condyle is covered by thick dense fiberous perichondrium (hyaline cartilge)

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Mandibular Fossa

Dense cortical bony surface of temporal bone

Posterior to articular eminence

Posterior nonarticular fossa is formed by tempanic plate

Thin at the roof of the fossa and tympanic plate

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Articular Capsule and Disk

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Articular Capsule

Ligamentous capsule surrounds the joint

Attached to the neck of the condyle and around the border of the articular surface of the temporal bone

Covered with dense fiberous tissue, which contains fibroblasts and chondrocytes

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Articular Capsule

Consist of internal synovial layer outer fibrous layer

containing veins, nerves, and collagen fibres.

Innervation of capsule disk arises from CN V; auriculotemporal and masseteric nerves

Venous plexus at posterior aspect

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Articular Disk (Meniscus)

Biconcave oval structure interposed between the condyle and the temporal bone

1 mm in the middle and 2-3 mm at periphery

Dense collagenous connective tissue

Centre area is a vascular, hyaine and devoid of nerve

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Synovial tissue

Synovial cell and connective tissue covering the lower and upper-joint spaces

Synovial fluid, a proteoglycan-hyaluronic acid complex acts as a lubricant and may participated in nutritional and metabolic interchange for central part.

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TMJ Ligaments

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Ligaments

Temporomandibular ligament

extend from base of

zygomatic process of the

temporal bone downward

and oblique to the neck of

the condyle

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Ligaments

Stylomandibular ligament

From styloid process and

runs downward and

forward to attach broadly

on the inner aspect of the

angle of mandible

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Ligaments

Sphenomandibular ligament

arising from the angular spine

of sphenoid bone and

petrotympanic fissure, ending

at lingula of mandible

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Functions of Ligaments

Accessory ligaments may limit border movements of the mandible

Fibrous capsule and TM ligament may limit of extreme lateral movements in wide opening of mandible

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Masticatory Muscles

Masseter muscle

Temporalis muscle

Medial pterygoid

muscle

Lateral pterygoid

muscle

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Masster muscle

Superficial layer

O : lower border of malar

bone, Zygomatic arch &

zygomatic process of maxilla

R : Downward and Backward

I : Angle of mandible and

inferior half of the lateral side

of mandible

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Masster muscle

Deep layer

O : Internal surface of

zygomatic arch

R : Downward (vertical)

I : Ramus of mandible and

base of coronoid process

50 degree between 2 layers

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Temporalis muscle

3 bundles Anterior bundle (vertical fibre)

–Action: Mandible elevator

(Close jaws), crushing and

chewing at C.O.

–Inaction: Mandible

depression (except Max.

Opening and Opening against

resistance)

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Temporalis muscle

Posterior bundle (Horizontal bundle)

Action: Mand. retraction and positioner

Inaction: Mand. depression and protrusion

Intermediate bundle

Action: Protrisive movement

– Nerve supply

Ant. and Post. deep temporal nerve

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Med. Pterygoid muscle

O : Pterygoid fossa and medial surf. of the lateral pterygoid plate

I : Inf. + Post. border of ramus and angle of mand.

R : Downward and Backward

N : Medial Pterygoid nerve

Rectangular shape at medial surface of ramus, synergistic with masseter muscle

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Lat. Pterygoid muscle

Superior headO: Wing of sphenoid and

infratemporal crest

R: Downward and Backward

Inferior headO: Lateral surf. of lateral

pterygoid plate

R: Upward and backward

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Lat. Pterygoid muscle

Insertion of superior and inferior heads

Ant. portion of the condylar neck (pterygoid fovea)

Ant. surface of the articular capsule

Ant. Border of the disk

Function Open the jaws, protrude

and lateral movement with moving disk forward

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Lat. Pterygoid muscle

Superior head Synergistic with elevator group of muscle for closing and clenching

Inferior head Synergistic with suprahyoid group of muscle for opening jaw

Nerve supplyLateral pterygoid nerve

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Non Masticatory Muscle

Digastric muscle

Mylohyoid muscle

Geniohyoid muscle

Orbicularis Oris

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Non Masticatory Muscle

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Types of Mandibular Movement

Rotational movement Horizontal axis of rotation Frontal (vertical) axis of

rotation Sagittal axis of rotation

Translational movement

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Rotational Movement

Around the horizontal axis (hinge axis)

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Rotational Movement

Around the frontal (vertical) axis

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Rotational Movement

Around the sagittal axis

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Translational movement

Clinical considerations

Aplasia of condyle Hypoplasia of condyle Hyperplasia of condyle Dislocation Ankylosis Trauma to TMJ Arthritis

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