TMJ Flashcards
what is temporomandibular joint?
- the articulation of the head of the mandible with the mandibular (glenoid) fossa of squamois region of the temporal bone
- where all muscles of mastication are working
why is the condyle smaller than the articular fossa?
being smaller (along with cylindrical head) allows great mobility AND rotational movement
posterior vs anterior compartment
- anterior= mandibular fossa
* posterior= tympanosquamosal fissure, petrotympanic fissure
synovial joint
- -united by articular capsule composed of outer fibrous layer and inner serous synovial membrane
- -capsule makes joint unique
- -joint cavity is filled with lubricating synovial fluid secreted by the synovial membrane
what lines the bones in contact in synovial joint?
articular cartilage
over time what happens to joint?
articular cartilage wears down and membrane produces less fluid
name for the TMJ joint based on movement?
ginglymoarthrodial joint
TMJ movements
1) hinge =ginglymoid (depress and elevate)
2) glide = arthrodial aka plane (protract, retract, laterally swivel)
why is TMJ considered a complex synovial joint?
bc it is an articular joint with a DISC (most don’t have a disc)
what compartment of TMJ has what specific movement?
- superior = gliding (translational) movement
* inferior= hinge (rotational) movement
Hiltons law
any nerve that is passing by a joint, will give off branches to innervate that joint
TMJ innervation from?
V3
TMJ innervation and BS?
1) superficial temporal and branches (lateral)
2) maxillary artery and bracnhes (medial)
joint capsule
completely encloses the joint
highly vascularized and innervated (receives all blood and nerves)
temporomandibular ligament
prevent posterior dislocation
anterior to capsule
temporal zygo arch to neck of mandible
stylomandibular ligament
helps limit anterior protrusion of mandible
styloid process down to angle of mandible
phenomandibular ligament
may act as pivot and limit protrusion
most frequently DAMAGED in IAN block (trismus=pain)
what is important for preventing dislocation posterioly?
the amount of boney structures behind mandibular fossa
what is important about the lateral pterygoid muscle being attached to joint capsule AND pterygoid fovea AND head of mandible?
1) prime protractor
2) makes sure articular disc moves with mandibular anteriorly (bc don’t want bone on bone contact)
mouth closed starting position
0 degrees
mouth closed, teeth in occlusion
first movement ofTMJ
- rotational hinge motion in lower compartment
- *up to 20mm
- head of mandible remains in mandibular fossa, only tilts down
second movement of TMG
- translation gliding movement
- head of mandible does NOT stay in fossa
- you Must already be depressed 15-20 in -order to glide open/wide
- superior compartment motion
what depresses TMJ (opens mouth)
1) gravity *prime
2) supra/infra hyoid muscles
3) inferior head of lateral pterygoid
what elevates TMJ (closes mouth)
1) temporalis
2) masseter and medial pterygoid
what does protrusion of TMJ (protracting chin)
1) lateral pterygoid
2) masseter and medial pterygoid
* use head of mandible
what does retrusion of TMJ (retracting chin)
1) temporalis
2) masseter
* pulling coronoid process
chewing is what motion?
- Circular
* Contraction of ipsilateral retractors and contralateral protractors
subluxation of the TMJ
- dislocation of jaw
- anterior is common
- posterior in uncommon due to bone, head of mandible will break before you dislocate
lock jaw
- Going past anterior eminence
- (normal open jaw has head on top of eminence)
