Mandibular Muscles

Question 1

What are muscles of mastication known as and why?

Answer 1

Mandibular muscles- more muscles involved in mastications

Question 2

Why do we need to check for abnormalities in TMJ before doing fillings?

Answer 2

Can lead to fracture of fillings

Question 3

What is the most powerful muscle in the body?

Answer 3

Masseter

Question 4

How much forces can the masseter carry?

Answer 4

Up to 50N

Question 5

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

Answer 5

Origin: zygomatic arch
Insertion: Lateral surface and angle of mandible
Action: Elevates mandible

Question 6

How is the masseter examined?

Answer 6

Palpate one finger intra-orally and one on the cheek. Tender in patients who have a clenching habit.

Question 7

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

Answer 7

Origin: floor of temporal fossa
Insertion: coronoid process and anterior border of ramus
Action: elevates and retracts mandible

Question 8

How is the temporalis examined?

Answer 8

Tender in patients with bruxist habits. Palpate between between superior and inferior temporal lines above ear extending forward towards the supra-orbital region and ask patient to clench.

Question 9

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

Answer 9

Origin: lateral surface of lateral pterygoid plate
Insertion: anterior border of condyle and infra-articular disc via 2 heads
Action: protrudes and laterally deviates the mandible and the inferior head functions with the mandibular depressors during openings.

Question 10

Where does the inferior and superior bellies of the lateral pterygoid insert?

Answer 10

Inferior: head of the condyle
Superior: intra- articular disc

Question 11

What causes a clicking sound?

Answer 11

Spasm in superior belly of lateral pterygoid pulling on the disc.

Question 12

How is the lateral pterygoid examined?

Answer 12

Record its response to resisted movement.

Question 13

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

Answer 13

Origin: the deep head- medial surface of LP plate, the superficial head-tuberosity of maxilla
Insertion: medial surface of angle of mandible
Action: elevates and assists in protrusion of mandible

Question 14

How is the medial pterygoid examined?

Answer 14

It cannot be examined.

Question 15

What are the movements of the TMJ and what are they collectively called?

Answer 15

Possult’s envelope- rotation and translation

Question 16

What is Possult’s envelope and what does it represent?

Answer 16

Border movements of the jaw, represent pressure protrusion of the mandible

Question 17

Which tooth has the greatest bite force and why?

Answer 17

First molar- proximity to the hinge

Question 18

What is the maximum biting force between molars?

Answer 18

200-700N

Question 19

What are the suprahyoid muscles and which of them act as jaw depressors when the infrahyoid muscles contract

Answer 19

Jaw depressors- digastric, mylohyoid, geniohyoid
Stylohyoid

Question 20

How are the suprahyoid and infrahyoid muscles involved in mastication?

Answer 20

Stabilise bone during mastication

Question 21

What are the infrahyoid muscles?

Answer 21

Sternohyoid, omohyoid, thyrohyoid, sternohyoid

Question 22

What does the intrinsic tongue muscle do what are the different types?

Answer 22

Alter shape- longitudinal, vertical, transverse

Question 23

What does the extrinsic tongue muscle do and what are the different types?

Answer 23

Alter shape and position of tongue- genioglossus, hypoglossus, palatoglossus, styloglossus

Question 24

What are the facial muscles for?

Answer 24

Mainly for expression, important in chewing

Question 25

What does the orbicularis oris and buccinator do in terms of mastication?

Answer 25

Prevent spillage and help control food bolus