Oral function muscles

Question 1

What are the 4 essential muscles for mastication (mandibular muscles)?

Answer 1

• Masseter
• Temporalis
• Lateral pterygoid
• Medial pterygoid

Question 2

What is the ‘origin’ of the masseter muscle?

Answer 2

• The zygomatic arch

Question 3

What is the ‘insertion’ of the masseter muscle?

Answer 3

• The lateral surface and angle of the mandible

Question 4

What is the ‘action’ of the masseter muscle?

Answer 4

• Elevates the mandible

Question 5

How would you examine the masseter muscle?

Answer 5

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

Question 6

In which patients would the masseter muscle be tender?

Answer 6

• In patients who have a clenching habit

Question 7

What is the ‘origin’ of the temporalis muscle?

Answer 7

• The floor of the temporal fossa

Question 8

What is the ‘insertion’ of the temporalis muscle?

Answer 8

• The coronoid process and anterior border of the ramus

Question 9

What is the ‘action’ of the temporalis muscle?

Answer 9

• Elevates and retracts the mandible

Question 10

In which type of patient will the temporalis muscle be tender?

Answer 10

• Patients who have a Bruxism habit

Question 11

How would you examine the temporalis muscle?

Answer 11

• 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

Question 12

What is the ‘origin’ of the lateral pterygoid muscle?

Answer 12

• From the lateral surface of the lateral pterygoid plate

Question 13

What is the ‘insertion’ of the lateral pterygoid muscle?

Answer 13

• Anterior border of the condyle and intra-articular disc via two independent heads

Question 14

What is the ‘function’ of the lateral pterygoid muscle?

Answer 14

• Protrudes and laterally deviates the mandible and the inferior head functions with the mandibular depressors during opening

Question 15

Where does the inferior belly of the lateral pterygoid attach to?

Answer 15

• The head of the condyle

Question 16

Where does the superior belly of the lateral pterygoid insert into?

Answer 16

• The intra-articular disc

Question 17

If someone has a clicking TMJ. Which muscle has been affected?

Answer 17

• Spasm of the lateral pterygoid which pulls on joint

Question 18

Can you examine the lateral pterygoid muscle by manual palpation?

Answer 18

• No

Question 19

How would you examine the lateral pterygoid muscle?

Answer 19

• 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 20

What is the ‘origin’ of the medial pterygoid?

Answer 20

• Deep head; medial surface of the lateral pterygoid plate

- Superficial head: tuberosity of maxilla

Question 21

What is the ‘insertion’ of the medial pterygoid?

Answer 21

• Medial surface of the angle of the mandible

Question 22

What is the ‘action’ of the medial pterygoid?

Answer 22

• Elevates and assist in protrusion of the mandible

Question 23

Is the medial pterygoid muscle able to be manually palpated?

Answer 23

• No, because of the location of the medial pterygoid, on the inside of the jaw, this muscle in not available for palpation

Question 24

Can the medial pterygoid muscle be examined by resisted movement tests?

Answer 24

• No, it does not respond well to these

Question 25

Hoe can we examine the medial pterygoid muscle?

Answer 25

- Unfortunately there is no reliable way of examining this muscle 

Question 26

Following an La injection, your patient was unable to open their mouth fully the following day. Which muscle was accidently hit by your needle?

Answer 26

- The medial pterygoid muscle 

Question 27

Hitting the medial pterygoid muscle accidently when giving an ID block might cause 'trismus'. What does this mean?

Answer 27

- Inability to open mouth as wide as should be able to | - Limited mouth opening

Question 28

What are the 2 movements of the TMJ?

Answer 28

- Rotation - initial movement | - Translation - Wider opening

Question 29

What kind of movement is the 'rotation - initial opening' of the TMJ?

Answer 29

- A hinge movement 

Question 30

The translation movement of the TMJ causes a wider opening on the mouth. These can be protrusive or retrusive movements. How does this occur?

Answer 30

- 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 31

What is the name for the chart that represents the border movements of the jaw?

Answer 31

- Posselt's envelope 

Question 32

What are the general maximum biting forces of molars?

Answer 32

200-700N

Question 33

What is an example of a psychological factor in relation to max biting forces?

Answer 33

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

Question 34

In relation to muscle mass, how does this affect the max biting force of an individual?

Answer 34

- Bigger muscles leads to larger forces 

Question 35

What is an example of a parafunction in relation to max biting forces and muscle mass of the jaw?

Answer 35

- Bruxism 

Question 36

What are the characteristics of  Type I muscle fibres? (2 points)

Answer 36

- Slow, low forces

Question 37

What are the characteristics of  Type II muscle fibres? (2 points)

Answer 37

- Fast, strong forces 

Question 38

What are different sub-types of type 2 muscle fibres? (3 points)

Answer 38

- IIA, IIX, IIB | - Predominant fibre type varies, depending on the jaw morphology and diet

Question 39

What is there evidence of with people who have square jaws?

Answer 39

- Tend to have more Type II fibres and can generate stronger biting forces 

Question 40

Why ate anterior teeth weaker than posterior teeth? (3 points)

Answer 40

- Smaller surface area of root - Posterior are nearer the centre of the force - Occlusal surface is larger

Question 41

Which teeth generate the greatest biting forces between them and why?

Answer 41

- 1st molars - Position relative to TMJ and muscles (molars are nearer the force generating muscles and the fulcrum) - Root area large (PDL support)

Question 42

The Suprahyoid and the Infrahyoid muscles are also muscles involved in mastication. What do they do?

Answer 42

- Stabalise the hyoid bone 

Question 43

What are the 4 suprahyoid muscles?

Answer 43

- Digastric* - Mylohyoid* - Geniohyoid* - Stylohyoid - When the hyoid bone is fixes, by the contraction of the infrahyoid's, the starred muscles act as jaw depressors

Question 44

What are the 4 infrahyoid ('strap') muscles?

Answer 44

- Sternohyoid - Omohyoid - Thyrohyoid - Sternothyroid

Question 45

The intrinsic muscles of the tongue alter the shape of the tongue. What are the names of the intrinsic tongue muscles? (3 points)

Answer 45

- Longitudinal - Vertical - Transverse

Question 46

The extrinsic muscles of the tongue alter the shape and position of the tongue. What are the names of the extrinsic tongue muscles? (4 points)

Answer 46

- Genioglossus - Hyoglossus - Palatoglossus - Styloglossus

Question 47

Which 2 facial muscles help to control the food bolus and prevent spillage out of the mouth?

Answer 47

- Orbicularis oris | - Buccinator