why is the term muscles of mastication misleading
because many other muscles are involved in mastication
the term mandibular muscles is suggested as an alternative
what is the origin of the masseter
zygomatic arch
what is the insertion of the masseter
lateral surface and angle of mandible
what is the action of the masseter
elevates the mandible
which patients may have a tender masseter
those who have a clenching habit
how do we examine the masseter
place on finger intra orally and the other on the check
what is the origin of the temporalis
floor of temporal fossa
what is the insertion of the temporalis
coronoid process and anterior border of ramus
what is the action of the temporalis
elevates and retracts mandible
which patients have a tender temporalis
patients who have a bruxism habit
how do you examine the temporalis
palpate its origin by asking the patient to clench the teeth together
how is digital palpation performed on the temporalis
it is performed between the superior and inferior temporal lines just above the ear, extending forwards towards the supra-orbital region
what is the origin of the lateral pterygoid
from the lateral surface of the lateral pterygoid plate
what is the insertion of the lateral pterygoid
anterior border of the condyle and intraarticular disc via two independent heads
what is the function of the lateral pterygoid
protrudes and laterally deviates the mandible and the inferior head functions with the mandibular depressors during openings
what does the inferior belly of the lateral pterygoid attach to
head of the condyle
what does the superior belly of the lateral pterygoid insert into
intra articular disc
how do we examine the lateral pterygoid
not accessible to manual palpation
best examined by recording its response to resisted movement
good correlation between the resisted movement test and the muscle being tender to palpitation
what is the origin of the deep head of the medial pterygoid
medial surface of the lateral pterygoid plate
what is the origin of the superficial head of the medial pterygoid
tuberosity of the maxilla
what is the insertion of the medial pterygoid
medial surface of the angle of the mandible
what is the action of the medial pterygoid
elevates and assists in protrusion of the mandible
why is the medial pterygoid not available for palpation
because of its location inside of the jaw
why is there no way of examining the medial pterygoid
does not respond well to resistive movement tests
why should bone be contacted when giving ID block
to ensure correct position within the pterygomandibular triangle and not to hit the soft tissues
what happens happens if you accidentally hit the medial pterygoid when giving ID block
trismus
what are the movements of the TMJ
rotation - initial opening
translation - wider opening
what happens in protrusion of the mandible
both condyles leave their fossa and move forward along their aritucular eminences
what happens in retrusion of the mandible
both condyles leave the eminences and move back into their respective fossa
what is the maximum biting/clenching forces
varies between teeth
maximum between molars is 200-700N
what are the psychological factors that effect the biting/clenching forces
fear of tooth fracture when maximum forces are used which can limit the maximum biting force recorded
how does muscle mass affect maximum biting force
bigger muscles = larger force
what are the muscle fibre types
type I type II sub types (IIA, IIX, IIB)
what are type I muscle fibers
slow, low forces
what are type II muscle fibers
fast, stronger forces
what are the sub type muscle fibres
predominant fibre type varies, depending on jaw morphology, diet
what do people with squarer jaws have more of which muscle fibres
type 2
can generate stronger btiting forces
which teeth generate the greatest biting forces
1st molars
what else effects force
tooth type and position
position relative to TMJ and muscles
root area - PDL support
what are the supra hyoid muscles
digastric
mylohyoid
geniohyoid
stylohyoid
what are the infra hyoid ‘strap’ muscles
sternohyoid
omohyoid
thyrohyoid
sternothyroid
what muscles act as jaw depressers
digastric
mylohyoid
geniohyoid
what do this intrinsic tongue muscles do
alter shape
what do the extrinsic tongue muscles do
alter shape and position
what are the intrinsic tongue muscles
longitudinal
vertical
transverse
what are the extrinsic tongue muscles
genioglossus
hypoglosus
palatoglossus
styloglossus
what do the facial muscles do
help to control food bolus and prevent spillage
what are the facial muscles
orbicularis oris
buccinator
What is Posselt’s envelope
the envelope of mandibular movements in the sagittal plane
What are the 5 points on Posselt’s envelope
RCP ICP edge to edge fully protruded fully open
What is the ICP
The intercuspal position is the ‘habit position’ where maximum intercuspation occurs. When you tell a patient to bite together, usually this is the position they adopt.
As the jaw protrudes towards end-to-end position what is it guided by
its position is guided by the cusps of the teeth (anterior determinants) and the slope of the fossae (posterior determinants
When the mandible opens how does it open (Posselt’s envelope)
opens in a smooth arc. The condylar head repositions as the jaw opens.
When the mandible closes how does it close (posselt’s envelope)
As the jaw closes to the RCP it does not make a smooth arc, only when the teeth are nearly together is the movement smooth.
What is the mnemonic for the supra hyoid muscles
my gravy spoon, darling
What is the mnemonic for infrahyoid mouses
TOSS
What is the mnemonic for the tongue muscles
SH the GP
