LECTURE 4- TMJ Flashcards
what are the main 2 articular structures that make up the TMJ
mandible and temporal
other bones contributing to the TMJ structure
maxilla , zygomatic , sphenoid, hyoid
what forms the 2 TMJs
condole of mandible and articular eminence of temporal
what type of joint is the TMJ
synovial joint
are the surfaces of the TMJ covered in fibrocartilage or hyaline cartilage?
avascular fibrocartilage
what type of movement joint is the TM joints
ginglymoarthrodial (diarthrosis) allowing for free movement
which layers of the joint surfaces are perpendicular to bony surface and what do they do
deep layers and withstand stress
how are the superficial layers of the joint surfaces arranged and what do they facilitate in the TMJ
parallel and facilitate sliding of joint
how much can a bite force be
up to 1200 N
what structure is the largest of facial bones
mandible
where do the mandible condyles sit in relation to the ear
anterior to external auditory meatus
what part of the mandible is the attachment site for temporalis muscle
coronoid process
what makes up for joint incongruence and separates articulation into inferior and superior TMJ functions
articular disc
how does the inferior TMJ function (type of joint and motion)
as an hinge joint - rolling posterior during opening
how does the superior TMJ function
as a plane joint , sliding anterior during opening
the articular disc of the TMJ is what shape?
bioconcave
what purposes do the articular disc of the TMJ serve
joint stability
minimize loss of mobility
reduce frication
decrease biomechanical stress at joint
where does the disc attach at the TMJ? what bony landmarks
- medial and lateral poles of the mandible condyle
- the bilaminar retrodiscal pad (posterior)
- joint capsule and tendon of lateral pteryoid muscle (anteriorly)
what do superior and inferior lateral pterygoid muscle restrict ?
posterior translation
what does the superior lamina allow the disc to do
translate anteriorly by stretching
what does the interior lamina limit
forward translation
what is the articular disc of the TMJ made up of
can it remodel?
collagen , proteoglycans , and elastin
no
what is the vascularity of the anterior band of the disc and where does it attach to
minimal to no vascular supply and attaches to joint capsule anteriorly
what is the vascularity of the intermediate zone of the disc and where does it attach to
no vascular supply and attached to medal and lateral condyle of mandible
what is the vascularity of the posterior band of the disc and where does it attach to
rich innervation and vascular supply from retrodiscal tissue and attached to retrodiscal tissue which is attached to capsule
where is the capsule for TMJ the stronger
laterally
what is the vascularity of the capsule forTMJ
highly vascular and innervated
3 ligaments of the TMJ
TM lig
stylomandibular lig
sphenomandibular lig
what does the oblique TM lig do
limits downward and posterior motion/ rotation of mandible
what does the horizontal TM lig do
resist posterior motion of condyle
what do both TM ligs do (what movement do they resist)
resists lateral displacement
what does the stylomandibular and sphenomandibular lig do
styloid - may limit protrusion of jaw , weakest
spheno - prevent foward translation
when is the TMJ engaged
mastication , swallowing and speaking
what are the arthokinematic movements of the TMJ
rolling
anterior slide
distraction
lateral glide
what are the osteokinematic motions of TMJ
depression
elevation
protrusion
retrusion
L/R lateral excursions
what is the Normal depression ROM of the TMJ
40-50 mm
2 finger functional
3 normal
what happens 1st during normal depression
11-25 mm anterior rotation of condyle on disc which leads to posteior roll of mandible
what happens 2nd during normal depression
translation : both condyle and disc anterior and interior which leads to
anterior slide of condyle
passive depression involves what
disc translate along the articular eminence and retrodiscal lamina limits translation
if there is active depression of the tmj what happens
there is no active contraction of superior lateral pterygoid
what happens passively during elevation of the mandible
elasticity of the superior retrodisc lamina apples traction force posteriorly
during active elevation of what eccentrically contracts to control posterior gliding and rotation of condyle
superior lateral pterygoid
what 3 muscles provide contrast pressure on disc to prevent dislocation during elevation
temporalis , medial pterygoid and masseter
cant win them all its ok
where do protrusion and retrusion occurs - superior or inferior joint of TMJ
in superior portion of the joint
what is anterior translation without rotation of inferior joint
protrusion
bilateral lamina stretch _____ to allow complete motion during protrusion
6-9mm
during protrusion teeth touching = ____ and lower teeth passing upper teeth = ___
normal
max
what does retrusion do
translation posteriorly (3mm)
what is retrusion limited by
TM lig and soft tissue in retrodiscal area
remember the earlier slide, TM limits posterior motion!
what is a important component of mandibular elevation from maximally depressed mandible
retrusion
what is the normal range of lateral excursion
8-11 mm
if someone does a right lateral excursion what happens at the joint
right TMJ rotation and L TMJ translation
limited right lateral excursion of the jaw, the muscles on the ____ side (especially the ___ lateral pterygoid) are likely tight or dysfunctional. This can restrict the ability to move the jaw to the right,
left
during lateral excursion there is an …
ipsilateral mandibular condyle rotation and contralateral mandibular condyle translations
what is it called if the mandible moves away from mandible during mandibular depression and stays to the L or R
deflection
C CURVE
what is a deviation
when the mandible move away from mideline during depressions or protrusion but then returns to midline at end range
S CURVE
what muscles help depression
digastric & suprahyoids
inferior lateral pterygoid
gravity
DIGS
what muscles help elevation
temporalis
masseter
medial pterygoid
superior lateral pterygoid
TMMP
what muscles help assist protrusion
Bil: masseter , medial and lateral pterygoid
what muscles help assist with retrusion
bil: temporalis , assisted by anterior digastric
what muscles help with lateral deviation
unilateral contraction of medial and lateral pterygoids to pull to contralateral side ( R medial and lateral will pull to L)
temporalis will pull to ipsilateral side
what are considered secondary muscle of TMJ
diagastric muscle (anterior belly)
mylohyoid
stylohyoid
geniohyoid
what are considered deep cervical flexors
longus colli and longus capitus
what are the bilateral and unilateral actions of the longus colli
bilateral: neck flexion
uni: SB with contralateral rotations
same as SCM
what is the unilateral and bilateral action for longus capitus
bilateral: neck flexion
unilateral: SB with ipsilaterla rotation
what position does forward heard posture put the mandible in?
retraction of mandible after malalignment
Contact of the upper and lower teeth limits TMJ motions when the mouth is ___ (closed or open)
So losing teeth would…
affect the mechanics!
Should the teeth touch during the day at rest?
no
maximal intercuspation
teeth are approximated occlusion position
linked together maximally in normal jaw closed position
what is the freeway space of the teeth
normal rest position with 1-5 mm of space between supper and lower teeth at rest
foward head ___ freeway space
decreases
what are teh structural changes of the disc
wear and tear may lead to OA
is it possible for normal wear and tear to occur without symptoms or disfunction?
yes!
what might lead to dysfunctions of the TMJ
trauma, postural habits, oral habits, bruxism (grinding)
capsular fibrosis of TMJ will lead to
overproduction of connective tissue leading to loss of tissue function with painful movements
inflammation of TMJ will lead to
capsulitis and synovitis leading to RA
joint hyper mobility of the TMJ is when there is …
an opening over 40 mm
if you have joint hypermobility at the TMJ what will happen
there will be a deflection of mandible to contralateral side when opening
what muscle hypertrophy, atrophy, or contracture if someone has joint hypermobility
lateral pterygoid muscle
dislocation of the TMJ will cause
opening with deviation and inability to close due to anterior translated disc
if you have an articular disc displacement with reduction then what happens
the condyle is behind the disk at rest so it translates anteriorly with depression with a click and translates posterior and slips out from under the disc during elevation with a click
if you have articular disc displacement without reduction then what happens
the posterior attachments to the disc are overstretched and are unable to relocate during depression
no clicking
disc stays in front the whole time, and condyle never pops on it, no clicking sound, locked jaw
if you have articular disc displacement without reduction when do you have pain
chewing , talking , yawning
