TMJ Flashcards
Where does the condyles of the mandible sit?
Mandibular fossa
What are the articular structures of the mandible?
Posteriorly - postglenoid tubercle
Anteriorly - articular eminence
Which of the two articular surfaces is the primary surface meant to sustain high forces?
Articular eminence
What type of cartilage does the articular eminence contain?
Fibrocartilage (not hyaline because hyaline cartilage cannot repair itself)
What type of cartilage can repair and remodel itself?
Fibrocartilage
What is the shape of the TMJ joint?
Convex on concave
What is the shape of the mandible?
Convex
What is the shape of the articular eminence?
Convex
What is the shape of the mandibular fossa?
Concave
How do you palpate the TMJ?
Through the external meatus to feel for the posterior aspect of the mandibularcondyles
What is the function of the articular disc?
Needed due to an incongruent joint
What are the two parts of the articular disc and what type of joint are they?
- Inferior - hinge joint (spins)
2. Superior - gliding joint (glides)
What comprises the inferior TMJ?
Mandibular condyle and the inferior surface of the articular disc
What comprises the superior TMJ?
Articular eminence and the superior surface of the articular disc
What is the function of the articular disc?
Increases stability, minimizes loss of mobility, reduces friction, and decreases biomechanical stress
Can the articular disc repair itself?
No, it is comprised of collagen, glycosaminoglycans, and elastin - but it is covered in fibrocartilage so that part can repair itself
What muscle assists with closing?
Lateral ptyergoid
What are the actions when opening the mouth?
Spin and then glide
What are the two parts of the bilaminar retrodiscal pad?
Superior lamina and inferior lamina
What is the function of the superior lamina?
Allows disc to translate anteriorly (opening)
Assist repositioning posteriorly (closing)
What is the function of the inferior lamina?
Limits forward (anterior) translation
What part of the lamina is stretched during dislocation?
Inferior lamina
What are the three positions where the joint capsule is loose?
Anterior, medial, and posterior
What is the main direction of dislocation?
Anteriorly
How does the doctor have the move the jaw when it is dislocated?
Doctor has to distract the jaw down and push the jaw back into place
Is the joint capsule innervated and vascularized?
Yes - aids in detailed info on movement and position
What is the main ligament in the joint?
Temporomandibular ligament - runs superior to inferior
What is the function of the temporomandibular joint?
Limits downward motion, posterior motion, and rotation during mandibular depression
What are the five osteokinematic motions?
- Mandibular depression
- Elevation
- Protrusion
- Retrusion
- Lateral excursion
What are the four arthrokinematic motions?
Rolling, anterior glide, distraction, and lateral glide (not a lot of movement due to lateral joint capsule being strong)
What is the normal ROM for depression?
40-50mm
Describe rolling and gliding when opening the mouth.
Both anterior motions - rolling (spin) occurs between mandibular condyle and inferior disc and gliding occurs between superior disc and articular eminence (opposite when closing)
What type of control occurs with the lateral ptyergoid?
Eccentric control of the disc when closing
What limits protrusion?
Bilaminar retrodiscal tissue (superior lamina)
What is protrusion important for?
Opening the mouth
What is retrusion limited by?
Temporomandibular ligament and compression of the retrodiscal area
What is retrusion important for?
Closing the mouth
What is normal ROM for lateral excursion?
8-11mm
What occurs during lateral excursion?
Ipsilateral condyle spins in transverse plane and contralateral condyle translates anteriorly - ex: left lateral excursion = left side spins and right side translates anteriorly
What is deviation?
“S” curve - returns to midline
What is deflection?
“C” curve - does not return to midline
What is the function of the temporalis?
Closing, retrusion, and ipsilateral deviation
What is the function of the masseter?
Closing and retrusion
What is the function of lateral pterygoid?
Protrusion and contralateral deviation
What is the function of the medial pterygoid?
Closing, protrusion, and contralateral deviation
What are the suprahyoid muscles?
Digastric, geniohyoid, mylohyoid, and stylohyoid
What is the function of the suprahyoid muscles?
Mandibular depression
What are the infrahyoid muscles?
Omohyoid, sternohyoid, sternothyroid, and thyrohyoid
What is the function of the infrahyoid muscles?
Stabilize the hyoid
What is the resting position of the TMJ?
1.5-5mm opening (teeth are not touching) - TMJ stress is decreased
What is the disadvantage of forward head posture?
Jaw retrudes which compresses the retrodiscal tissue, so the massication muscles have to overwork to close the jaw - infrahyoid muscles are put on stretch which pulls the hyoid posteriorly and causes retrusion
Which lateral pterygoid is contracted with deviation to the left?
Right lateral pterygoid
