1i - TMJ anatomy

Question 1

what is the most common complaint of someone w TMJ disorder

Answer 1

ear pain

Question 2

what are examples of parafunctional habits

Answer 2

nail biting
clenching
grinding
lip biting
object biting
chewing gum
bruxism

Question 3

what is bruxism

Answer 3

unconscious grinding, clenching teeth
- at night

Question 4

what is a relevant characteristic of the TMJ capsule

Answer 4

thicker on outside

Question 5

OIA of temporalis

Answer 5

O: entire temporal fossa
I: coronoid process & medial border of mandibular ramus

A: elevation, retrusion/retraction, ipsilateral lateral excursion (unilateral)

Question 6

what is the main biting ms

Answer 6

temporalis

Question 7

what are characteristics of the temporalis

Answer 7

thin but very large
dives behind zygomatic arch so can’t get to ms tendon junction

Question 8

OI of masseter

Answer 8

superficial head
O: ant 2/3 of zygomatic arch
I: lat border of mandib angle

deep head
O: post 1/3 of zygomatic arch
I: superior border of mandibular ramus

Question 9

actions of the masseter ms

Answer 9

elevation
ipsilateral lateral excursion (unilateral)

deep: retrusion/retraction
superficiala: protrusion

Question 10

OI of medial pterygoid

Answer 10

O: lateral pterygoid plate of sphenoid bone and maxilla
I: medial surface of mandibular angle

Question 11

what are the actions of the medial pterygoid

Answer 11

elevation
protrusion
contralateral lateral excursion (unilateral)

tonic contraction acts as a functional sling around angle of mandible

Question 12

what holds the mandible in position

Answer 12

sphenomandibular lig needs a tonic contraction from the masseter, otherwise would just hang in fossa
- creates a functional sling

Question 13

OI of lateral pterygoid

Answer 13

superior head
O: greater wing of sphenoid
I: disc

Inferior head
O: lateral border of sphenoid
I: condylar neck

Question 14

what are the actions of the lateral pterygoid

Answer 14

protrusion (bilateral)
contralateral lateral excursion (unilateral)

superior: elevation
inferior: depression

Question 15

what is the lateral pterygoid’s role in elevation

Answer 15

helps to eccentrically control disc tension and its position w closing

Question 16

what is the lateral pterygoid’s role in depression

Answer 16

initiates open

Question 17

what is the role of infrahyoid ms

Answer 17

stabilize the hyoid

Question 18

what are the 4 infrahyoid ms

Answer 18

omohyoid
sternohyoid
sternothyroid
thyrohyoid

Question 19

what are secondary ms to the TMJ and what is their role

Answer 19

infra and supra hyoids

aren’t directly acting on TMJ, but impact posture and way TMJ sits

Question 20

what is the role of the suprahyoids

Answer 20

assist w mandibular depression

Question 21

what are the 4 suprahyoid ms

Answer 21

digastric
geniohyoid
mylohyoid
stylohyoid

Question 22

what are the primary ms innervated by and what are those ms

Answer 22

trigeminal (CN V) mandibular branch

masseter
temporalis
medial and lateral ptery
mylohyoid

Question 23

what nerves innervate the secondary ms

Answer 23

hypoglossal n. (CN XII)
facial n. (CN VII)
ventral rami C1 via CN XII
ventral rami C1-3

Question 24

what are the dermatomes relevant to the TMJ

Answer 24

C2-3: mandibular angle

mandibular branch of trigem (CN V) covers remainder of jaw

Question 25

what are the mandible's functional sling ms

Answer 25

masseter and medial pterygoid

Question 26

what cervical ms impact the TMJ

Answer 26

suboccipital ms SCM scap ms - UT, levator scap

Question 27

what cervical joints impact the TMJ

Answer 27

AO joint cervical facet joints

Question 28

what ms are involved in elevation

Answer 28

masseter temporalis medial pterygoid lateral pterygoid (superior fibers)

Question 29

what ms are involved with depression

Answer 29

lateral pterygoid (inferior fibers) suprahyoids infrahyoids

Question 30

what ms are involved with protrusion

Answer 30

masseter (superficial fibers) medial pterygoid lateral pterygoid

Question 31

what ms are involved w retrusion/retraction

Answer 31

masseter (deep fibers) temporalis suprahyoids (digastric)

Question 32

what ms are involved in lateral excursion

Answer 32

ipsi temporalis (uni contxn) ipsi masseter (uni contxn) contra med pterygoid (uni) contra lat pterygoid (uni)

Question 33

what is the osseous articulation of the TMJ

Answer 33

superior aspect of mandibular condyle on mandibular fossa of the temporal bone

Question 34

what is the signficance of the coronoid process

Answer 34

important landmark for attachment poitns

Question 35

how is the fibrocartilage structured and what is the importance of this

Answer 35

high density collagen content which allows for repetitive forces thru jaw to be withstood moving it constantly w talking, eating, swallowing - have to withstand repetition and force of eating

Question 36

where is the fibrous capsule in relationship to the disc

Answer 36

fibrous capsule attaches to entire periphery of disc

Question 37

anterior articulations of the TMJ disc

Answer 37

temporal bone (articular eminence) mandibular condyle superior head of lat ptery

Question 38

posterior articulation of TMJ disc

Answer 38

retrodiscal lamina

Question 39

what is the main function of the fibrocartilage surrounding the TMJ disc

Answer 39

dissipate and endure loads and stresses

Question 40

why does the TMJ disc have such a high water content

Answer 40

dissipate forces mobile when loaded - if load front part of disc, water contents move post

Question 41

how does the thickness of the disc change and why

Answer 41

thin intermediate region - accommodates convexity of condyle thicker anteriorly and posteriorly - maximize congruency to dec pressure biconclave shape that accommodates the convexity of the joint and inc the surface area

Question 42

how does the vascularity and innervation change throughout the disc

Answer 42

thin intermediate region is avascular and not innervated - can't have pain which is good bc that is what contacts the fossa thicker ant and post is vascular and innervated -> source of pain

Question 43

how does the elasticity change throughout the disc and how does this impact the functioning

Answer 43

superior portion elastic - stretches w opening inferior portion less elastic - stabilizes joint

Question 44

what motions compose mastication

Answer 44

elevation and depression w lateral excursion and protrusion - random and asymmetrical combo

Question 45

what does mastication cause at the jiont

Answer 45

joint compression

Question 46

what is mastication

Answer 46

tearing, chewing, and grinding motions via coordination of all ms

Question 47

what are the arthrokinematics of depression

Answer 47

early phase - post rotation late phase - rotation - ant and inf translation of condyle and disc together

Question 48

when is there the greatest ligamentous tension in the TMJ joint

Answer 48

maximal opening

Question 49

how much motion is there in the early phase of depression

Answer 49

0-26mm

Question 50

how much motion is there in the late phase of depression

Answer 50

26-50mm

Question 51

what functions are possible with <10mm of depression

Answer 51

can only drink

Question 52

what functions are possible with 10-20mm of depression

Answer 52

push food in mouth

Question 53

what functions are possible with 20-30mm of depression

Answer 53

can eat food using fingers

Question 54

what functions are possible with 30-38mm of depression

Answer 54

can use fork and small pieces

Question 55

what functions are possible with >38mm of depression

Answer 55

can eat normally

Question 56

what initiates the arthrokinematics of elevation

Answer 56

tension in retrodiscal ligament

Question 57

what are the arthrokinematics of elevation

Answer 57

condylar head and disc translate post and superiorly condylar body rotates ant slight ant rotation of disc d/t eccentric contraction of superior head of lateral ptery (helps to sit back into place)

Question 58

what is the closed pack position of the TMJ

Answer 58

teeth clenched - greatest joint congruency

Question 59

arthrokinematics of lateral excursion

Answer 59

ipsilateral condyle - rotation/spine contralateral condyle - translation

Question 60

arthrokinematics of protrusion

Answer 60

ant translation

Question 61

arthrokinematics of retrusion

Answer 61

post translation

Question 62

what are protrusion and retrusion important components of respectively

Answer 62

protrusion - max opening retrusion - max closing

Question 63

what ROM is necessary for protrusion and why

Answer 63

26mm at the end range of opening