TMD- Anatomy + Biomechanics

Question 1

What % of ppl with TMD require tx

Answer 1

3.6-7% of indvs

Question 2

What % of TMD is due to internal derangemnt and muscular disorder

Answer 2

int derangment- 26-51%

Muscular disorder- 30-33%

Question 3

What type of jt is the TMJ

Answer 3

ginglymaorthroidal (hindge + gliding)

Question 4

What is the ant and post wall of mandibular fossa

Answer 4

ant- articular eminence of squamous temporal bone

post- Tympanic plate

Question 5

What is the load bearing portion of the TMJ + where will most degerneration occur

Answer 5

the articular eminance (articular surface)

–mandibular condyle and lower jt space.

Question 6

What does the articular disk split and what mm attaches to it

Answer 6

Firm, oval fibrous plate bw condyle and articular fossa–splits it into upper (discotemporal) and lower compartments (discomendibular)

Sup head of lat pterygoid

Question 7

What is found posterior to disk and feature of it

Answer 7

bilaminar zone (retrodiscal)- very well innervated and vascularized. - causes pain/problematic

Question 8

What allows rotational movement at the tmj

Answer 8

Medial and lateral attachments to the condyles through collateral ligaments allow rotational movement of the disc on the condyle during opening and closing.

Question 9

What does the articular capsul form and where is it thickest and what does it limit

Answer 9

Froms tempomandibular lig
-Thick anterolat and lat (thin anteromed, med + post)

-limits movement of the mandible

Question 10

What are the 2 accessory ligs of the mandible and what is there function

Answer 10

1. sphenomandibular- no influence on madibular mvmt (protects blood vessels and nerves)
2. Stylomandibular lig- limits end ranges of protrusion

Question 11

What are the 2 main movement of the TMJ

Answer 11

Rotary/hinge- axis around centers of condyle

Translatory- mvmt of mandible in the AP/ML directions

Question 12

what compartment does rotation and translation typically occur

Answer 12

1. Rotation is primarily between the disc and condyle in the LOWER compartment. (1st step)
2. Translation is primarily between the articular eminence and disc (and mandible) in the UPPER compartment.

Question 13

What is the primary and secondary movers in depression of mandible

Answer 13

Prime- gravity

Secondary- Supra/infrahyoid mm, lat pterygoid, digastric, geniohyoid, mylohyoid

Question 14

What mm are used in elevation of the mandible (3)

Answer 14

Tempralis
Masseter
Medial pterygoid

Question 15

how wide should u be able to open your mouth and how much do u need for ADLs

Answer 15

3 fingers (40-60mm)

need 25-35mm for adls

Question 16

What is the typical opening sequence of the TMJ

Answer 16

condyles rest on disk
as madible moves ant with opening the disc moves med and post untill collateral ligs and lat pterygoid stop its mvmt (disc is not seated)

Question 17

if there is a c curve while opening what does it indicate

Answer 17

Hypomobility to towards side of deviation (displaced disc without reduction/unilat hypomobility)

Question 18

if there is a s curve while opening what may it be due to

Answer 18

• mm imbalance/ spasm

- late deviation due to capsulitis

Question 19

What should be the primmary mm in protrusion and what measurement should it be over

Answer 19

Protrusion primarily by LP and should be over 7mm

Question 20

What should be the normal amount of retrusion

Answer 20

1-2mm

Question 21

if laterally moveing to the right what side would be the working and balancing side

Answer 21

R- Working side (but esentially resting/not moveing)

L- balancing side (but moving inf + medially)

Question 22

On what side of the jt does DJD and disc perforations typically occur

Answer 22

along lat aspects of the TMJ

Question 23

With unilateral tmj pain what side should u chew on

Answer 23

On same side as pain (as Working Side actually has less mvmt than balancing side)