TMJ

Question 1

two bones

Answer 1

1) temporal and mandible
2) articular eminence

Question 2

bony landmarks

Answer 2

1) mandibular fossa
2) articular eminence
3) squamotympanic fissure
- petrotympanic fissure

Question 3

bony components of the TMJ

Answer 3

1) thin bone forms the roof of the fossa (area cannot withstand occlusal forces)
2) articular eminence is composed of dense bone that can withstand the forces of heavy loading

Question 4

articular disc lies between the 2 bones

Answer 4

1) attached to joint capsule 360 around

Question 5

articular disc of the TMJ

Answer 5

1) composed of dense fibrous connective tissue
2) better regenerative properties
3) can be better deformed
- flexible
4) wears better
5) not a great load bearing surface

Question 6

capsular ligament

Answer 6

1) temporomandibular ligament
- outer oblique and inner horizontal portions
- both parts of the capsule
2) lateral portion is thicker than medial
3) limit disarticulation

Question 7

joint spaces of the TMJ

Answer 7

1) 2 joint spaces
- separated by the articular disc
- form 2 separate synovial spaces with 2 different movements
2) upper joint space
- translation
3) lower joint space
- rotation

Question 8

articular disc of the TMJ

Answer 8

1) attaches to condyle on medial and distal ligaments
2) biconcave
3) thinnest in center
4) thickest posteriorly
5) thicker medially than lateral
6) disc moves with the mandible

Question 9

articular disc and distal ligaments

Answer 9

1) moves anteriorly and posteriorly with mandible and rotates over head of mandible

Question 10

attachments of articular disc

Answer 10

1) anteriorly
- superior head of lateral pterygoid m. (inferior head to neck of condyle)
2) posteriorly
- retrodiscal tissue sandwiched between two lamina = bilaminar zone
- superior lamina = elastic fibers
- inferior lamina = collagen fibers

Question 11

nerve supply of TMJ

Answer 11

1) primary
- auriculotemporal nerve to restrodiscal tissue
2) secondary
- masseteric nerve anteriorly
3) general sensory
- primarily to retrodiscal tissue

Question 12

vasculature of TMJ

Answer 12

1) primarily to retrodiscal tissue
2) drainage to pterygoid venous plexus

Question 13

biomechanics of the TMJ

Answer 13

1) closed
- condyle rests in the thinnest part, the inter mediate zone, against the posterior slope of the articular eminence

Question 14

muscles of mastication

Answer 14

1) primarily elevators

Question 15

muscle actions

Answer 15

1) jaw movements
- elevate
- depress
- retrude
- protrude
- lateral excursion

Question 16

accessory muscles of mastication

Answer 16

1) suprahyoid and infrahyoid muscles
- minor assistance in jaw movement

Question 17

biomechanics of TMJ

Answer 17

1) opening first movement is rotation
- within the inferior joint space (hinging)
- can only achieve limited opening
2) second movement is translation
- within the superior joint space
- can now achieve maximum opening

Question 18

lateral movement

Answer 18

1) lateral pterygoid
2) medial pterygoid
3) anterior temporalis
4) medial temporalis

Question 19

normal cycling of opening and closing

Answer 19

1) opening
- disc translates forward with the mandible while rotating posteriorly over its head
2) superior retrodiscal lamina stretches - it’s elastic
—
3) opening
- inferior head of lateral pterygoid is contracting
4 )closing
- superior head is contracting
—
when teeth bite into food, the condyle is fulcrumed away from the articular eminence
5) closing
- superior head of lateral pterygoid muscle balances posterior pull of elastic superior retrodiscal lamina to keep the disc positioned between the two bones

Question 20

abnormal cycle

Answer 20

1) pops and clicks
2) in the closed position, the disc may not slide all the way back to its normal position
3) the head of the condyle rests on the posterior border of the disc rather than the intermediate zone
= anterior displacement (with or without reduction)
4) condyle pops over the posterior border of the disc (this is with reduction)
- creates pop or click

Question 21

why doesnt the disc slide all the way back to its normal position?

Answer 21

1) the superior head of the lateral pterygoid muscle never fully relaxes
2) the superior retrodiscal lamina loses elasticity
3) the joint ligaments become lax

Question 22

what may happen with abnormal cycle?

Answer 22

1) compression of retrodiscal tissues may cause degeneration, often with pain
2) then leading to degeneration of the articular surfaces