Occlusion

Question 1

What is canine guidance?

Answer 1

When the mandible moves TO the working side, there should ONLY be contact between the two canines on that side i.e. NO POSTERIOR TOOTH CONTACTS. No protrusive interference.
Known as a MUTUALLY PROTECTED OCCLUSION.

Question 2

What is group function and in what patient group is it most commonly seen?

Answer 2

When mandible moves towards working side - multiple teeth in contact on that side.
Bilateral group function frequently seen in tooth-wear.

Question 3

What problems can occur in dynamic occlusion?

Answer 3

Occlusal interferences

Question 4

What are types of occlusal interferences?

Answer 4

Working side
Non-working side
Protrusion - any posterior contact during protrusion

Question 5

What are the 2 types of bruxism and briefly explain each?

Answer 5

Eccentric - parafunctional grinding of teeth - involuntary rhythmic or functional grinding or clenching of teeth in movements of mandible other than chewing - may lead to occlusal trauma

Centric - Clenching - pressing and clamping of jaws and teeth together - associated with anxiety or physical effort.

Question 6

What are some signs and symptoms of bruxism?

Answer 6

Toothwear
Fractured teeth/ restorations
Tooth migration
Tooth mobility (even in absence of periodontitis)
Muscle pain and fatigue
TMJ disorder
Headache
Earache

Question 7

What is the difference between primary, secondary and fremitus occlusal trauma?

Answer 7

Primary - intact periodontium
Secondary - reduced periodontium
Fremitus - palpable or visible movement of a tooth when subjected to occlusal forces.

Question 8

What does ICP show in posselt’s envelope?

Answer 8

Inter-cuspal position - teeth in maximum interdigitation.
Tooth position regardless of condylar position. Comfortable bite. Can be called centric occlusion.

Question 9

What does E show in posselt’s envelope?

Answer 9

Edge to edge - teeth slide forwards until incisal edges of upper and lower teeth touch.

Question 10

What does Pr show in posselt’s envelope?

Answer 10

Protrusion
Condyle moves forwards and downwards on articular eminence. May have some incisal/ canines touch but eventually NO TOOTH CONTACTS.

Question 11

What does T show in posselt’s envelope?

Answer 11

Maximum opening
NO TOOTH CONTACTS - mouth wide open.
Full translation of the condyle over the articular eminence.

Question 12

What does R show in posselt’s envelope?

Answer 12

Retruded axis position
No tooth contacts
Most superior, anterior position of the condylar head in the fossa.

Question 13

What does RCP show in posselt’s envelope?

Answer 13

Retruded contact position
First tooth contact after mandible has been in retruded axis position.

Question 14

Describe the hinge movement of the TMJ

Answer 14

The hinge movement of the TMJ occurs when the mouth is opened slightly.
The condylar heads rotate around an imaginary line through the rotational centres.
The condyle is the axis around which the jaw rotates - called TERMINAL HINGE AXIS.

Question 15

What does a facebow do?

Answer 15

Records the relationship of the maxilla to the terminal hinge axis of rotation of the mandible.
Allows maxillary cast to be placed in an equivalent relationship on the articulator.

Question 16

Describe translation of the condyle

Answer 16

Lateral pterygoid contracts - pulls articular disc and condyle forward
Articular disc and condyle begin to move
Condyle travels downwards and forwards along the incline of the articular eminence

Question 17

What does Posselt’s envelope show?

Answer 17

3D mandibular movements = border movements of the mandible.
Describes the extremes of mandibular movement.

Question 18

What is disc displacement?

Answer 18

A common disorder of the TMJ
When the articular disc of the TMJ slides forwards past the articular eminence.
Causes pain as the retro-discal tissue is pulled between the condyle and the mandibular fossa

Question 19

What happens when the jaw is locked?

Answer 19

The condyle cannot slide past/ get back onto the articular disc. Prevents jaw opening fully. Clicking will usually go away at this point. Disc displacement without reduction.

Question 20

What is lateral translation?

Answer 20

Jaw moving side to side - also known as the bennet movement.
Lateral pterygoid muscles allow for this movement.

Question 21

What is the bennet angle?

Answer 21

The angle formed by the sagittal plane and path o mandibular condyle during lateral movement when viewed in the horizontal plane.

Question 22

What does the line between RCP and ICP show?

Answer 22

The RCP-ICP slide.

Question 23

Where are the ICP contacts in molars?

Answer 23

The lingual cusp of an upper molar contacts the fossa of a lower molar
The buccal cusp of a lower molar contacts the fossa of an upper molar