TMJ

Question 1

TMJ articulation

Answer 1

Articulation of mandibular condYle and mandibular fossa of temporal bone

Question 2

Is TMJ closed chain or open chain

Answer 2

Closed

Question 3

What kind of joint is the TMJ

Answer 3

Synovial joint

Question 4

What is the significance of the Articular eminence and mandibular condyle articulation?

Answer 4

Articular eminence and mandibular condyle are both convex resulting in an incongruent joint

-covered by fibrocartilage

Question 5

Describe the articular disc of TMJ

Answer 5

Disc is biconcave

Purpose: allow convex surfaces to remain congruent through ROM, increases stability, minimizes loss of mobility, reduces friction and decreases biomechanical stress on TMJ

• separates into sup and inf jts
  - sup: gliding jt
  - inf: simple hinge jt

Question 6

Attachments of articular disc

Answer 6

Attached to medial & lateral poles of condyle

-attached to jt capsule& lateral pterygoid anteriorly

• attached to bilaminar retrodiscal pad posteriorly
  - superior Lamina: assist the disc in translating ant with mandibular depression
  - inferior lamina: limits forward translation

Question 7

What do the passive structures of the TMJ do?

Answer 7

Available joint motion is determined by elasticity of the joint capsule and ligaments

• capsule is relatively firm medially/laterally
• capsule is thin and loose anterior and posterior
  
  • this allows for ant translation when mouth is open
  • TMJ is predisposed to anterior dislocation

Question 8

What is the normal resting position of mouth and what muscle helps?

Answer 8

Lips closed and teeth seven mm apart

Maintained by temporalis muscle

Question 9

What are the osteokinematics of TMJ

Answer 9

Depression/elevation
Protrusion/retrustion
L & R lateral excursion

Question 10

Mandibular depression/elevation phases

Answer 10

Depression (open)

• early phase: roll posteriorly
• late phase: slides anterior

Elevation (close)

• early phase: slides posterior
• late phase: rolls anterior

Question 11

Mandibular protrusion/retrusion arthrokinematics

Answer 11

Protrusion:
-anterior and slightly inferior slide of condyle and disc

Retrusion:
-posterior and slightly superior slide of condyle and disc

-no rotation at all

Question 12

Mandibular Lateral Excursion Arthrokinematics

Answer 12

-involved primarily side to side translation of condyle and disc within fossa

Left lateral excursion:
-left condole spins in place and right condyle slides anterior and to the left

Right lateral excursion:
-right condyle spins in place and left condyle slides anterior and to the right

Question 13

TMJ ranges for depression, mastication, function screening, protrusion, lateral excursion

Answer 13

Depression: 40-50mm
Mastication: 18mm of depression
Functional screen of depression
    -functional: 2 knuckles
    -normal: 3 knuckles

Protrusion: lower teeth surpass upper teeth
Lateral excursion: 8-11mm

Question 14

What are some symptoms of temporal mandibular disorders?

Answer 14

Pain, popping, reduced bite force, reduced ROM with mouth opening, HA, tinnitus trigger points

Question 15

What are factors associated with TMD?

Answer 15

• stress/emotional distrubance
• daily oral parafunctoinal habits
• asymmetric muscle activity
• sleep bruxism
• chronic forward head posture
• C-spine pathology
• sensitization of CNS

Question 16

Describe deviation and deflections of TMJ

Answer 16

Deviations:
Motion that produces an “s curve” with depression or protrusion

Deflections: Motion that produces an “c curve” with depression or protrusion

Question 17

Describe difference of articular disc displacement with and without reduction

Answer 17

With reduction

• click during mandibular depression and mandibular elevation
• reciprocal click

Without reduction
-disc does not relocate and patient will demonstrate limited mandibular motion due to mechanical obstruction due to the disc

-the later the click occurs in opening phase = greater degree of dislocation

Question 18

Describe the interaction between Masseter and medial pterygoid

Answer 18

• functional sling formed around the angle of mandible by masseter and medial pterygoid
• contraction of both = powerful note (95lbs)
• create shear force during grinding or crushing food

Question 19

Affect of C-spine and Posture of TMJ

Answer 19

Head and neck position may affect tension in cervical muscles which can influence the function of mandible