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BDS2 BAMS > Oral Function - Muscles > Flashcards

Oral Function - Muscles Flashcards

1
Q

mandibular muscles

muscles of mastication

A
  • Masseter
  • Temporalis
  • Lateral Pterygoid
  • Medial Pterygoid
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2
Q

origin of masseter

A

zygomatic arch

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3
Q

insertion of masseter

A

lateral surface and angle of mandible

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4
Q

action of masseter

A

elevates the mandible (closing the jaw)

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5
Q

masseter in patients with clenching habit

A

tender

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6
Q

examining masseter

A

Place one finger intra-orally and the other on the cheek

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7
Q

origin of temporalis

A

floor of temporal fossa

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8
Q

insertion of temporalis

A

coronoid process and anterior border of ramus

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9
Q

action

A

elevates and retracts the mandible

- closing the jaw and retraction

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10
Q

temporalis is tender in patients who have….

A

bruxist habit

clenching and grinding teeth at night - parafunction

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11
Q

examining temporalis

A

Palpate its origin by asking the patient to clench the teeth together, because it is difficult to palpate the insertion area.

Digital palpation is performed between the superior and inferior temporal lines just above the ear, extending forwards towards the supra-orbital region

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12
Q

origin of lateral pterygoid

A

from the lateral surface of the lateral pterygoid plate

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13
Q

insertion of lateral pterygoid

A

anterior border of the condyle and intra-articular disc via two independent heads
- superior and inferior heads so 2 points of insertion
clinically important

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14
Q

inferior (top) belly of the lateral pterygoid attaches where

A

to the head of the condyle

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15
Q

the superior belly of the lateral pterygoid attaches where

A

into the intra-articular disc

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16
Q

jaw click is a sign of

A

spasm of lateral pterygoid

Tense pull disc = click

Limited mouth opening - improves with day and click will disappear

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17
Q

function of lateral pterygoid

A

protrudes and laterally deviates the mandible and the inferior head functions with the mandibular depressors during openings.

Lateral movement and opening of jaw

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18
Q

what does clenching and grinding do to the lateral pterygoid

A

clenching and grinding wears muscle out
as lateral deviation of the jaw as well as opening

  • Physiotherapy or splint can reduce load on muscle
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19
Q

examining lateral pterygoid

A

Not accessible to manual palpation

Best examined by recording its response to resisted movement.
- Give idea on the muscle

There is a good correlation between the resisted movement test and the muscle being tender to palpation.

Test – try to open jaw and clinician pushes upwards, jaw move to one side and you push it the other way.
- Problem is causes pain

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20
Q

origin of medial pterygoid

A

deep head
- medial surface of lateral pterygoid plate

superficial head:
- tuberosity of maxilla

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21
Q

insertion of medial pterygoid

A

medial surface of angle of mandible

Masseter is from the lateral side.
- Together they hold the jaw like a swing

22
Q

action of medial pterygoid

A

elevates and assists in protrusion of the mandible

23
Q

examination of medial pterygoid

A

Because of the location of the medial pterygoid, on the inside of the jaw, this muscle is not available for palpation.
- It also does not respond well to resistive movement tests.

Therefore, unfortunately, there is no reliable way of examining this muscle.

24
Q

following an injection, patient was unable to open the mouth fully on the following day.
which muscle was accidentally hit by the needle?

A

ID block coming from inside

  • Inserted into area in cheek
  • Medial pterygoid affected as from the inside

Try to avid bulk/mass of muscle when inject

Bone should be contacted to ensure correct position within the pterygomandibular triangle and not t hit soft tissues.

Hitting this muscle by the needle accidentally might cause “trismus”

25
Q

2 movements of the TMJ

A

rotation

translation

26
Q

rotation of TMJ

A

initial opening

hinge movement

27
Q

translation

A

wider opening

Protrusive or Retrusive Movements

  • As the mandible moves during protrusion, both condyles leave their fossae and move forward along the articular eminences.
  • When the mandible retrudes, both condyles leave the eminences and move back into their respective fossae
28
Q

Posselt’s Envelope

A

full TMJ movement

  • 2 movement of TMJ - rotation and translation
  • Chart represents the border movements of the jaw/mandible
    Important for prosthetics dentistry
29
Q

Posselt’s Investigation (1953)

A 
65 fit & healthy dental students
- Age 20 -29
- 2 or fewer missing posterior  teeth
- No present dental disease
1 Cadaver

Graphical recordings in Occlusal & Sagittal plane + profile radiography

30
Q

average maximum biting/clenching forces between molars

A

200-700N on average

varies between teeth and people

  • Forces of 1200-1500N reported in some groups (Eskimo)
  • ‘World record’ is >4300N
31
Q

‘psychological’ factors that impact maximum biting/clenching forces

A

Fear of tooth fracture when maximum forces are used
- This could limit maximum biting force recorded

Exceed capacity = tooth splits

32
Q

physical factors affecting maximum biting force

A

Muscle mass
- Bigger muscles = larger forces
- Parafunction (Bruxism)
(Hypertrophic masseter muscle due to excessive use; Asymmetrical face shape)

only Unilateral chewing (wrong should be bilateral – assess, to avoid muscle effect)

33
Q

type I muscle fibres

A

slow, low forces

34
Q

type II muscle fibres

A

fast stronger forces

35
Q

sub types muscle fibres

A

IIA, IIX, IIB

36
Q

predominant muscle fibre type in jaw

A

varies depending on jaw morphology and diet

37
Q

muscle fibre type in people with ‘squarer’ jaws

A

more Type II fibres and can generate stronger bite forces

38
Q

where is the greatest bite force generated?

A

between the 1st molars

posterior teeth

39
Q

why is the greatest bite force generated between the 1st molars?

A

Position relative to TMJ and muscles
- Molars are nearer the force generating muscles and the fulcrum (TMJ)
Root area (PDL support)

Your jaw joint would be where the hinge of the nutcracker is.
- Your front teeth would be at the ends of the handles and your molars would be close to the hinge itself.

  • If you place the nut far away from the hinge you will have to use extra force trying to break the nut open; maybe not even cracking it.
  • Whereas, if you place the nut close to the hinge, the nut cracks easily with only a modest amount of force. .

Further back = closer to hinge = less force needed (posterior teeth)

40
Q

what do the suprahyoid and infrahyoid muscles do?

A

involved in mastication too

- stabilise when you chew

41
Q

4 suprahyoid muscles

A
  • Digastric
  • Mylohyoid
  • Geniohyoid
  • Stylohyoid
42
Q

4 infrahyoid muscles

A
  • Sternohyoid
  • Omohyoid
  • Thyrohyoid
  • Sternothyroid
43
Q

infrahyoid muscles a.k.a

A

‘strap’ muscles

44
Q

what suprahyoid muscles act as jaw depressors when the hyoid bone is fixed?

A
  • Digastric *
  • Mylohyoid *
  • Geniohyoid *

contraction

45
Q

2 types of tongue muscle

A

intrinsic

extrinsic

46
Q

intrinsic tongue muscles role

A

alter shape

47
Q

3 types of intrinsic tongue muscle

A

longitudinal
vertical
transverse

48
Q

extrinsic tongue muscle role

A

alter shape and position

49
Q

4 extrinsic tongue muscles

A
  • genioglossus
  • hypoglossus
  • palatoglossus
  • styloglossus
50
Q

facial muscles role in mastication

A

Help to control food bolus and prevent spillage

- Role in keeping the bolus in the centre of the oral cavity

51
Q

2 facial muscles that have a key role in mastication

A
  • Orbicularis oris

- Buccinator

BDS2 BAMS (54 decks)

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