TMJ

Design:

• Socket & fixed base

• In the socket, there is a lever with fulcrum (which is mandible)

• If mandible pushed back, it would normally impinge airway with fixed base

• Solved by making fulcrum moveable

  • Disc: collagen, fibers in different directions

  • Limited movements with ligaments

  • Surrounded TMJ with capsule

• Function: caused by muscles loading joint

• Teeth: fitting into the jaw to jaw relationship, made for harmony

How can you get deformed joint?

• Pathology: cysts, tumors (rare)

• Overload of joint (muscle strain w/ function)

Principles:

• 1) Teeth must fit the harmonious jaw to jaw relationship. Not vice versa

Disc wants to be able to rotate over top of condyle

• As condyle moves forward, disc moves from the front to the top of condyle

• Medial and lateral disc ligaments are what helps it rotates

What prevents disc from moving forward?

• Tethered by posterior ligament which prevents from displacing from the front of the condyle

  • • When this is intact, it can't displace/torn

    • Joint clicks when disc is in improper position

• Elastic fibers

What causes displacement then?

• Muscle attached to disc and condyle

  • ONLY source of tensive pulls

  • Disc alignment is thus related to muscle

• Loading on posterior band starts to compress/thinner

• Thus, beginning of disc dearrangment