Occlusion

Question 1

Digastric muscle

Answer 1

Origin: Mastoid Notch on Process

Insertion: Digastric Fossa (internal surface of mandible)

Innervation:

• Anterior belly: Mylohyoid nerve - branch of Mandibular division of Trigeminal nerve.
• Posterior belly: Posterior Auricular branch of Facial nerve.

Action:
- Depress and retract the mandible
- Elevate the hyoid bone
~ Utilised during swallowing and speech

Question 2

Lateral pterygoid muscle

Answer 2

Origin:
Upper head - Infra-temporal surface of Greater Wing of Sphenoid
Lower head - lateral surface of Lateral Pterygoid Plate

Insertion:

Innervation:

Action:

Question 3

When should an inter-occlusal bite record be taken?

Answer 3

When the ICP is not clear on the models, they should be taken minimally and close to the preparation.

Question 4

Interference

What is it?

What are the consequences for the pt?

Answer 4

Tooth on tooth contacts occur during normal mandibular movements i.e. closing, protrusion, lateral excursions. When these movements are restricted or displaced by a contact that is out of place this leads to what is called an INTERFERENCE.

This can result in several consequences for the pt and their teeth. Such as:

• Pain due to overloading of the PDL
• Wear facets
• Fracture of teeth and restorations
• Mobility of teeth

NB: A common reason for many of these problems is due to a restoration being left high.

Question 5

Temporalis

Answer 5

Contraction -> Elevation and Retraction of the mandible

Question 6

What protective mechanism exists to prevent interferences of the non-working side teeth during lateral excursions?

Answer 6

Condylar Guidance

= the translational movement if the condyle down the articular eminence on the non-working side -> downwards displacement and .’. disclusion of the posterior teeth on non-working side of the mandible as the pt rotates the mandible laterally

Question 7

2 paths of movement of the mandible during opening

Answer 7

1. ROTATION
   Rotational movement
   Condyles remain within the glenoid fossa
2. TRANSLATION
   The condyles move down the articular eminence to allow maximum opening; usually approx 40mm

Question 8

Situations when canine guidance ill advices

Answer 8

1 - Heavily restored canine
2 -
3 -

Question 9

During mandibular protrusion 2 protective mechanism serve to disclude the posterior teeth:

Answer 9

• The posterior most = CONDYLAR GUIDANCE
• when the condyles translate down the articular eminence.
• The anterior most = INCISAL GUIDANCE
• the movement of the lower incisors over the palatal aspect of the upper incisors

NB: Preparation of multiple crowns for the upper anterior teeth can lead to the loss of incisal guidance, however this can be reproduced or reinstated by asking the technician to create a custom incisal guidance table.

Question 10

Masseter

Answer 10

Mandibular movements facilitated by masseter:

• Elevation
• Protrusion