Oral Functions: Muscles

Question 1

What are the mandibular muscles?

Answer 1

lateral pterygoid
medial pterygoid
masseter
temporalis

Question 2

What is the origin, insertion and action of the masseter?

Answer 2

Origin - zygomatic arch

Insertion - ramus
and angle of mandible

Action - elevates mandible

Question 3

How to examine the masseter muscle?

Answer 3

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

check the bulk of the muscle, it is tender in patients who have a clenching habit

Question 4

What is the origin, insertion and action of the temporalis?

Answer 4

Origin - floor of temporal fossa

Insertion - coronoid process and
anterior border of ramus

Action - elevates and retracts mandible

Question 5

How to examine the temporalis?

Answer 5

Palpate its origin by asking the patient to clench the teeth together.

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

It is tender in patients who have a bruxist habit

Question 6

What is the origin, insertion and action of the lateral pterygoid?

Answer 6

Origin: surface of the greater wing of the sphenoid and lateral surface of the lateral pterygoid plate

Insertion: anterior border of the condyle and intra-articular disc
via two independent heads

Action: protrudes and laterally deviates the mandible. depresses the mandible

Question 7

Where do the inferior/ superior belly of the lateral pterygoid attach?

Answer 7

• The inferior belly of the lateral pterygoid attaches to the head of the condyle.
• The superior belly inserts into the intra- articular disc

Question 8

How can you examine the lateral pterygoid?

Answer 8

Not accessible to manual palpation

Best examined by recording its response to resisted movement.

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

Question 9

What is the origin, insertion and action of the medial pterygoid?

Answer 9

Origin - deep head: medial surface of lateral pterygoid plate ; superficial head: tuberosity of maxilla

Insertion - medial surface of angle of mandible

Action - elevates and assists in protrusion of the
mandible

Question 10

How to examine the medial pterygoid?

Answer 10

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.

Question 11

When injecting a nerve block, what may happen and what can prevent this?

Answer 11

Accidentally hit the medial pterygoid with the needle causes trismus (spasm of the jaw muscles, causing the mouth to remain tightly closed)

therefore

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

Question 12

What are the two movements of TMJ?

Answer 12

• Rotation - initial opening
• Translation-wider opening

Question 13

What type of movement is rotation?

Answer 13

hinge movement

Question 14

What type of movements is translation?

Answer 14

Sliding
Wider opening: Protrusive or retrusive movements

Question 15

How does translation happen?

Answer 15

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

Question 16

What is Posselt’s Envelope of Motion?

Answer 16

refers to the full TMJ movement which involves rotation + translation.

(max movement jaw can create)

Question 17

Which teeth have max biting force?

Answer 17

molars (200-700n)

Question 18

What psychological factors could limit max biting force recorded?

Answer 18

Fear of tooth fracture when maximum forces are used

Question 19

What oral disorder could too much force cause?

Answer 19

parafunction (bruxism)

Question 20

What are the types of muscle fibres and what are their qualities?

Answer 20

• Type 1 = Slow, low forces.
• Type 2 = Fast, stronger forces.
• Sub-types (IIA, IIB, IIX) = Predominant fibre type varies, often dependent on jaw morphology and diet

Question 21

What fibres do people with squarer jaws have more of?

Answer 21

type 2

Question 22

Where is the greated bit force generated and why?

Answer 22

• Greatest bite forces generated between 1st molars
• Position relative to TMJ and muscles (Molars are nearer the force generating muscles and the fulcrum (TMJ)
• Root area (PDL support)

Question 23

What are the suprahyoid muscles?

Answer 23

– Digastric
– Mylohyoid
– Geniohyoid
– Stylohyoid

Question 24

What groups of muscles surround the hyoid bone?

Answer 24

infrahyoid (strap) muscles
suprahyoid

Question 25

What are the infrahyoid (strap) muscles?

Answer 25

–Sternohyoid
–Omohyoid
–Thyrohyoid
–Sternothyroid

Question 26

What muscles depress the jaw?

Answer 26

diagastric
mylohyoid
geniohyoid
lateral pterygoid

Question 27

What are the two types of tongue muscles and what do they do?

Answer 27

intrinsic (alter shape of tongue)

extrinsic (alter shape, position)

Question 28

What are the intrinsic muscles?

Answer 28

Longitudinal, vertical, transverse

Question 29

What are the extrinsic muscles?

Answer 29

Genioglossus
Hyoglossus
Palatoglossus
Styloglossus

Question 30

What facial muscles help control food bolus and spillage?

Answer 30

–Orbicularis oris
– Buccinator