TMJ articulation
mandibular condyles w/ temporal bone
TMJ
unique, most complex joint in human body; allows for
-chewing
-speech
-respiration
temporal bone
-articular fossa
-articular eminence
-zygomatic process
-postglenoid process
articular eminence
consists of smooth, rounded protuberance on inferior aspect of zygomatic process
articular fossa
depression on inferior aspect of temporal bone, posterior & medial to zygomatic arch
postglenoid process
sharper ridge posterior to articular fossa
mandible anatomy
-condylar heads
-fibrocartilage
-compact bone
-cancellous bone
-bone marrow & endosteum
mandible
articulates w/ each temporal bone @ heads of condyles of mandible w/ articulating surface of condyle
joint capsule
completely encloses TMJ; wraps around articular eminence & fossa & mandibular condyle
synovial joint
double lubricated cavity for smooth movement
joint motion
bilateral, mobile joint articulation of temporal bone & mandible
-synovial joint
-fibrous disk
fibrous disk
creates 2 synovial cavities, making it a double joint
TMJ ligaments
-temporomandibular ligament
-sphenomandibular ligament
-stylomandibular ligament
temporomandibular ligament
-lateral side of joint wrapped around capsule
-reinforcement of capsule
-prevents excessive retraction
sphenomandibular ligament
-medial side, from spine of sphenoid bone to lingula mandibular foramen
-landmark for inferior alveolar injection
stylomandibular ligament
medial side, from styloid process of temporal bone to angle of mandible
jaw movement of TMJ
combination of gliding & rotational movement
gliding movement
occurs b/w disc & articular eminence of temporal bone in the upper synovial cavity;
-protrusion & retraction of mandible
rotational movement
occurs b/w disc & condyle in lower synovial cavity;
-depressed & elevation of mandible
lateral deviation
combo of gliding & rotational
depression of mandible
lowering of lower jaw
elevation of the mandible
raising of mandible
muscles of mastication
-masseter
-temporalis
-medial pterygoid
-lateral pterygoid
free movement
interplay of masticatory muscles & morphology of teeth
masticatory movement
synergistic action of 3 groups of muscles
masseter
elevates jaw & clenches teeth w/ bi/lateral contraction of both sides
temporalis
retraction of mandible during elevation; elevates & retracts mandible, clenches teeth
medial pterygoid
elevates mandible; weaker than masseter
lateral pterygoid
lateral deviation of mandible is controlled by one muscle at a time; protrudes mandible & pulls articular disk forward- opens jaws
TMJ disorders
symptoms of tenderness, pain &/or muscle spasms associated w/ all 4 muscle groups
crepitus
an audible sound such as produced by the rubbing together of fragments of a fractured bone or by air moving in a tissue space
subluxation
acute episode of TMJ disorder in which both joints become dislocated often due to excessive mandibular protrusion & depression
temporomandibular disorder
disorder involving one or both TMJ
trismus
spasms of the muscles of mastication, resulting in inability to open or close mouth
myospasm
increased muscular tension & shortness that cannot be released voluntarily & prevents lengthening of muscles involved