TMJ anatomy and biomechanics

regions interdependent with the TMJ

cranial, cervical, thoracic, the other TMJ

posture effect on TMJ

forward head posture and slouching cause the teeth to come together more and increase pressure on the joint

how does neck mommouvement affect mouth movement

mouth opens with extension and closes with flexion

motions of the TMJ

depression, elevation, protrusion, retrusion, lateral deviation

TMJ resting position

mouth slightly open, lips together, teeth not in contact

closed packed position of TMJ

max depression (anterior closed), max retrusion (posterior closed)

capsular pattern of TMJ

limited opening

lower joint of the TMJ

between mandibular condyle and inferior disc

upper joint of the TMJ

between superior disc and articular eminence

function of the articular disc

biconcave to increase stability when the condyle articulates with the articular eminence

structures connected to the disc anteriorly

joint capsule, lateral pterygoid

structures connected to the disc posteriorly

retrodiscal pad, superior/inferior lamina

function of superior lamina

stretch to retract the disc with elevation

function of inferior lamina

passive restrain to limit forward translation of the disc during depression

signs if retrodiscal pad is causing pain

intermittent clicking with yawning, TTP: external auditory meatus

function of medial/lateral collateral ligaments

attach the disc to the condyle to allow them to move together

function of medial/lateral capsular ligaments

provide restraint to opening and lateral deviation

ligaments of the TMJ

tempromandibular, sphenomandibular, stylomandibular

function of temporomandibular ligament

horizontal: limit posterior movement of the condyle, oblique: limits downward and posterior movement of the condyle

function of sphenomandibular ligament

limits protrusion

function of stylomandibular ligament

limits protrusion

motion of the lower joint

rotation

when does rotation occur during mouth movement

anteriorly during first half of mouth opening and posteriorly during last half of mouth closing

motion of the upper joint

protrusion/retrusion

movement of the condyle with protrusion

translates inferior and anterior

movement of the condyle with retrusion

translates superior and posterior

arthrokinematics of condyle during mouth opening

anterior rotation then anterior/inferior glide

arthrokinematics of the condyle during mouth closing

superior/posterior glide then posterior rotation

movement of the condyles during lateral deviation

contralateral protrusion and ipsilateral posterior spine

what is suggested by a lack of right lateral deviation

the left condyle is hypomobile and doesn’t want to protrude

what is suggested by end range deviations

upper joint dysfunction

cause of clicks during anterior disc displacement that reduces

first: condyle rearticulates with disc during opening, second: disc subluxes anteriorly during closing

what is suggested by an earlier opening click and later closing click

the disc is closer to the condyle

what happens during an anterior disc displacement that does not reduce

the disc stays in front of the condyle and blocks anterior translation to limit opening

muscles that depress the TMJ

digastric, suprahyoids, inferior lateral pterygoid (gravity)

muscles that elevate the TMJ

temporalis, masseter, medial pterygoid

function of medial pterygoid

elevation and protrusion

lateral pterygoid during opening

moves the articular disc anteriorly

muscles that protrude the TMJ

superficial masseter, medial pterygoid, lateral pterygoid

muscles that retrude the TMJ

posterior temporalis, deep masseter, anterior digastric