Lecture 8: TMJ Joint Final? Flashcards
Key considerations for mastication
involves chewing, tearing, teeth grinding, speaking, and swallowing
interaction between CNS and muscles
TMJ = one of the most used joints of the body
bones involved in mastication
mandible
maxilla
temporal bone
sphenoid bone
hyoid bone
where can you palpate the mandibular condyle
just anterior to the external auditory meatus
what is the temporal fossa
slightly concave region
formed by parietal, temporal, frontal, sphenoid, and zygomatic bones
attachment for temporalis muscle
describe characteristics of the mandible
largest of facial bones
very mobile
suspended by ligaments/capsule and muscles
many landmarks
describe characteristics of the maxilla
R and L sides fuse
it is fixed
forms the floor of nasal cavity and the orbit of the eyes
key considerations for the sphenoid bone
it does not contribute to the TMJ structure
it does provide proximal attachments for medial and lateral pterygoid muscles
hyoid bone is anterior to what
C3
describe the osseous structures of the TMJ joint
flattened front to back (condyle) thin dense layer of fibrocartilage (better at absorbing force than hyaline with superior reparative process)
medial and lateral poles
describe the mandibular fossa
it is articular (sloped anterior wall), load bearing, thin/compact bone, and lined with fibrocartilage
full opening - they condyle slides forward (~50 degrees) across this opening with shear and compression forces
superior and posterior areas are non-articular, thin, and non load bearing
capsular structures in the TMJ joint
loose fibrous capsule
synovial membrane
capsule is firm medially/laterlaly and provides support
lax anterior to posterior to allow mouth opening
ligamentous estrutures of the TMJ joint
lateral ligaments stabilize
have oblique and horizontal fibers
what osteokinematics take place at the TMJ joint
protrusion: mandible translates anterior without rotation
recursion: reverse
lateral excursion: side to side (contralateral and ipsilateral); average 11mm max unilateral
depression and elevation: avg opens about 45-50 mm; typical mastication is 18mm
describe the arthrokinematics of the TMJ joint
combo of rotation and translation
rotation: mandibular condyle rotates relative to the inferior surface of the disc
translation: the mandibular condyle and disc slide together
what arthrokinematics take place in the TMJ joint with protrusion and retrusion
mandibular condyle and disc translate anterior/posterior
1.25 max
follows the slope of articular prominence (i.e. protrusion = anterior and downward)
describe the arthrokinematics of the TMJ joint with lateral excursion
side to side translation
mandibular condyle on the lateral excursion serves as a pivot point with contralateral condyle making a wider arc of rotation
describe the arthrokinematics of the TMJ joint with depression and elevation
combo of rotation and translation
axis is constantly moving
no set radio of rotation/translation
early and late phase movements
describe the arthrokinematics of the TMJ joint with depression and elevation
combo of rotation and translation
axis is constantly moving
no set radio of rotation/translation
early and late phase movementsdesci
describe the arthrokinematics of the TMJ joint doing the early phase of depression/elevation
35-50% primarily rotation
posterior rotation on concave inferior surface of the disc
mandible goes inferior/posterior
describe the arthrokinematics of the TMJ joint during the late phase of depression/elevation
final 50-65%
primarily translation (1.5-2mm)
condyle and disc slide forward and inferior along the articular eminence
closing is reverse (tension in retrodiscal lamina helps)
innervation of the muscles of the TMJ joint
primary muscles = mandibular nerve (division of the trigeminal nerve- CN V)
sensory is from 2 branches of the mandibular nerve
what are the primary muscles of mastication
masseter
temporalis
medial pterygoid
lateral pterygoid
describe the masseter
thick, strong,
zygomatic arch to ramus of mandible,
line of force is perpendicular
large forces to crush food
describe the temporalis muscle
flat fan shaped
through space to anterior and medial ramus
elevates
describe the medial pterygoid
nearly parallel to the masseter
internal surface of ramus
bilateral elevation and unilateral/contralateral excursion
describe the lateral pterygoid
2 heads
travels horizontally
unilateral is contralateral excursion
bilateral strong protrusion
max human biting force
422 N (95 lbs)
what are the secondary muscles of mastication
supra hyoid: can assist with depression of mandible, speech/tongue movement, swallowing, and managing food bolus
infra hyoid: stabilizes
describe TMJ disorders
broad and vague
impairment of muscles, joints, ligaments, and discs
often from teeth grinding or FHP (and sometimes OA)
most cases are self limiting
what are signs and symptoms of TMJ disorders
popping
reduced bite force
reduced open range
locking
headaches
tinnitus
facial/scalp pain
