Tmj

Question 1

What is the tmj

Answer 1

Temporomandibular Joint Articulation between temporal bone and mandible
• Synovial hinge-type joint divided into two synovial
cavities by fibrocartilaginous disc

Question 2

What are some conditions that can affect the tmj

Answer 2

• Number of conditions can involve joint
– TMJ disorder (pain [often refers to ear, jaw, lateral side of head*], clicking, locking/)
– TMJ dislocation (e.g. secondary to trauma, yawning)
– Arthritis

Question 3

Which nerve innervated the tmj

Answer 3

• Joint is innervated by auriculotemporal nerve*

– Branch of mandibular division of trigeminal (Vc)

Question 4

Describe teh anatomy of the tmj

Answer 4

• Articular surfaces of bones lined with fibrocartilage and do not come into direct contact
• Separated by fibrocartilaginous disc into 2 parts
• Divides joint into two synovial-line cavities filled with synovial fluid - Sup and inferior joint cavity
• Stabilised by a joint capsule and a series of (3) extracapsular ligaments (not shown in image)

Question 5

Describe the hinge and gliding action of the tmj

Answer 5

• Initial opening of jaw (depression of mandible) is by hinge (rotational) action in the inferior half of the joint cavity
• Opening the jaw more widely requires the condyle to glide forward over the articular tubercle: this movement occurs in superior half of joint cavity
• Simple retraction and protraction of the mandible involves movements at the superior joint capsule (gliding)
• Number of muscles act to move the TMJ

Question 6

Desribe movements of the tmj and the muscles involved

Answer 6

Ss

Question 7

What does depression of the mandible require

Answer 7

Wide opening (depression) of the mandible requires rotation (hinge) action and gliding forward [protrusion]: lateral pterygoid muscle important for this action
Note, in normal depression the condyle does not pass in front of the articular process
When jap is fully depressed, the condylar process of mandible does not extend past articular proess

Question 8

Explain dislocation of the tmj

Answer 8

• Facial trauma (blow to side of jaw, especially if open) and yawning can cause TMJ dislocation
• Jaw locks as joint fixes in open position due to anterior dislocation of condyle over the articular tubercle (lies anterior to the tubercle)
• Contraction of muscles around joint (muscles of mastication) keep joint locked in anterior displacement