TMJ movement

Question 1

State the 4 purposes of mastication and swallowing

Answer 1

• Breakdown of solid food into small pieces
• Stimulation of saliva production
• Contributes to taste and smell
• Aids digestion of certain foods like red meat, chicken and potatoes

Question 2

Describe the teeth as masticatory apparatus:

Answer 2

• Incisors: Biting and stripping
• Canines: Piercing and seizing
• Premolars and molars: Grinding
• Human teeth are evolving
• Cats are carnivores: That’s why they have pointy teeth as their carnivorous diet requires for them to tear the meat. They don’t need to grind food, that’s why they have sharp occlusal surfaces in place of a flat one.
• Sheep are herbivores: That’s why they have many molars and lack canines. They need to constantly chew on their foods
Humans are omnivores: That’s why we have a mixture of teeth like incisors, canines and molars.

Question 3

List the anatomy of the TMJ

Answer 3

• A: joint capsule
• B: Lateral ligament
• Articular eminence
• Articular disk

Question 4

List the movements that the TMJ is responsible for

Answer 4

1. Hinge: Horizontal rotation (inferior TMJ compartment)

2. Translation/ sliding: Sliding onto articular eminence

Question 5

List the 5 types of movements the TMJ conducts

Answer 5

Depression

Elevation

Protrusion

Retrusion

Lateral excursion

Question 6

For the TMJ movement of depression:

• State what type of movement it is
• Muscles involved

Answer 6

TMJ movement:
• If mouth is slightly open, it is a hinge and slight translation.
• If mouth is fully open, it is a hinge and translation movement

Muscles:
• Lateral pterygoid
• Mylohyoid
• Anterior belly of the digastric muscle

Question 7

For the TMJ movement of elevation:

• State what type of movement it is
• Muscles involved

Answer 7

TMJ movement:
Translation and hinge

Muscles:
• Temporalis (anterior fibres)
• Masseter
• Medial pterygoid

Question 8

For the TMJ movement of protrusion:

• State what type of movement it is
• Muscles involved

Answer 8

TMJ movement:
Symmetric translation

Muscles:
• Bilateral, medial and lateral pterygoids
• Assisted by masseter

Question 9

For the TMJ movement of retrusion:

• State what type of movement it is
• Muscles involved

Answer 9

Symmetric translation

Muscles:
• Bilateral, medial and lateral pterygoids
• Posterior fibres of temporalis

Question 10

For the TMJ movement of lateral excursion:

• State what type of movement it is
• Muscles involved

Answer 10

State what type of movement it is:
Left side example:
• Left head of condyle is retruded in socket
• Right head of condyle is protruding out of socket

Muscles involved:
• Left side: posterior temporalis
• Right side: Lateral and medial pterygoids