Oral Biology: Mastication

Question 1

What is the role of mastication? (3)

Answer 1

1) breakdown in foodstuffs (preparation for swallowing, increase surface area for chemical digestion, release chemicals for sense of taste)
2) stimulation of salivary flow
3) growth and maintenance of oro-facial tissues

Question 2

In a shortened dental arch, how many teeth are sufficient for satisfactory masticatory function?

Answer 2

the presence of at least UR5-UL5, LL5-LR5 allows for a functional occlusion, meaning that there is not always a need to replace all lost posterior teeth

Question 3

In the mechanics of ingestion, what happens at Stage I transport?

Answer 3

food from lips move to posterior teeth

Question 4

what happens after stage I transport?

Answer 4

mastication (chewing) except for liquids

Question 5

Stage II transport follows on from mastication. What happens at this stage?

Answer 5

food from posterior teeth move to the back of the tongue

Question 6

What happens after stage II transport?

Answer 6

swallowing of food

Question 7

Name the four components of the mechanics of mastication

Answer 7

1) jaw movements (chewing cycles)
2) tongue movements (directing food, crushing food, mixing food with saliva)
3) cheek movements (directing food)
4) lip movements (accepting food, retaining food: anterior oral seal, directing food)

Question 8

How long is one chewing cycle in it’s duration (s)?

Answer 8

0.5-1.2 seconds duration

Question 9

What are the four phases of a chewing cycle?

Answer 9

1) opening
2) fast closing
3) slow closing
4) intercuspal phases

Question 10

During which two phases of the chewing cycle does the breakdown of food occur?

Answer 10

The slow closing phase and the intercuspal phase

Question 11

Describe the action of the condyle on the:

1) working side
2) non-working side

Answer 11

1) working side: the condyle rotates around a vertical axis with a lateral bodily movement (of 1-1.4mm) known as the BENNETT MOVEMENT
2) non-working side: the condyle moves downwards, forwards over the articular eminence and moves medially, and is described by a BENNETT ANGLE

Question 12

During closing, what are the movements of the condylar head on the working side during a chewing cycle?

Answer 12

During closing, the working side head moves MEDIALLY to normal position in glenoid fossa and rotates back to normal orientation

Question 13

During closing, what are the movements of the condylar head on the non-working side?

Answer 13

during closing, the non-working side head moves upwards, backwards and laterally, then returns to normal position in the glenoid fossa

Question 14

What is the sequence of muscle activation during the opening phase?

Answer 14

1) mylohyoid
2) digastric
3) lateral pterygoid

Question 15

what is the sequence of muscle activation during closing?

Answer 15

1) temporalis
2) masseter
3) medial pterygoid

(lateral pterygoid is also active)

Question 16

What are the factors leading to a preferred side of chewing? (4)

Answer 16

1) whether side is dentate, partially dentate or edentulous
2) restored with a fixed or moveable prosthesis
3) pain/pathology leads to avoidance
4) occlusal interference

Question 17

What are the controls of mastication?

Answer 17

1) Higher Centres (cerebral cortex)
2) General Neural Pattern Generator (otherwise called the ‘chewing centre’
3) Motor nucleus signal masticatory muscle motoneurones to masticatory muscles
4) peripheral feedback is sent from muscles of mastication back to higher centres, chewing centre and motor nucleus