Occlusion

Question 1

Define occlusion

Answer 1

Contacts between teeth

The relationship of the dental arches when tooth contact is made

Question 2

Determinants of occlusion

Answer 2

TMJ - tempomandibular joint/positioning

Muscles of mastication

Teeth

Neuromuscular control

Question 3

TMJ allow 2 types of movement?

Answer 3

Hinge

Sliding movement

Question 4

How are muscles of mastication controlled and how do they move?

Answer 4

Under control of neuromuscular system

Exert powerful forces and can produce fine, controlled movement

Question 5

Neuromuscular control

• what is it?

Answer 5

Feedback system to CNS from periodontal ligament, muscles, tendons, TMJ

Emotional, environmental stress can over ride this - sensitive system

Question 6

What is an ideal occlusion?

Answer 6

Teeth are aligned such that the masticatory loads are within the physiological range

Lateral jaw movements occur without undue mechanical interference

In the rest position of the jaw, the gap between the teeth is correct for the individual

The tooth alignment is aesthetically pleasing

Question 7

Physiological occlusion?

Answer 7

Occlusion within the patient’s adaptability

There is no breakdown of the periodontium, no tooth wear, teeth stay in position

Adaptive mechanisms
- New jaw position
- Condylar remodelling
- Teeth can change their position

Question 8

Pathological occlusion

Answer 8

A pattern of occlusal contact resulting in one or more of the elements of the masticatory system being overstretched therefore may cause parafunction

Symtoms
- Pain/Temporomandibular disorders
- Fracture
- Tooth wear – localised or generalised
- Drifting, mobility

Question 9

Concepts in occlusion that cause differences in individuals

Answer 9

• dental arches - size varies
• angulation of teeth within alveolus varies considerably
• intercuspal position (ICP)

Question 10

Intercuspal position (ICP) - what is it? varies depending on?

Answer 10

Position of the mandible when the maxillary and mandibular teeth are maximally meshed together (maximum intercuspation)

Varies depending on the size of the arches and the position of the teeth

Question 11

Malocclusion - what is it? what causes it?

Answer 11

An anatomical variation rather than an abnormality

Malocclusions result from one or combination:
- malposition of individual teeth
- malrelationship of the dental arches
- variation in skeletal morphology of the jaws

Question 12

Classifications of malocclusion

Answer 12

Angles molar classification
- position of the first molar

Incisor classification
- position of the incisor teeth

Question 13

Angles class 1 molar relationship

Answer 13

The mesiobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar

Question 14

Angles class 2 molar relationship the mesiobuccal cusp on the upper first molar occludes mesial to the class 1 position

Answer 14

The mesiobuccal cusp off the upper first molar occludes mesial / more anterior to the class 1 position

Question 15

Angles class 3 molar relationship

Answer 15

The mesiobuccal cusp of the upper first molar occludes distal / more posterior to the class 1 position

Question 16

Angles molar classification

Answer 16

Class 1

Class 2

Class 3

Question 17

Incisor classification

British institute classification

Answer 17

The position of the contact of the lower incisor with the palatal surface of the upper incisor

Class I
Class II div 1
Class II div 2
Class III

Question 18

Incisor relationships

Answer 18

Over jet - distance between the tip of the lower incisor and upper incisor (measured in mm)

Overbite - distance between the tip of the lower incisor and upper incisor (measured in mm)

Question 19

Incisor relationships - class 1

Answer 19

Incisor tip of lower incisor occlude with the palatial (mid) third of upper central incisors

Question 20

Incisor relationships - class 2

Division 1 and 2

Answer 20

Division 1 - upper incisors occlude anterior to the lowers

Division 2 - upper incisors try to meet lower incisors - retroclined

Question 21

Crowding?

Answer 21

Teeth are markedly out of line of the dental arch because there is disproportion between size of arch and size of teeth

Question 22

Anterior open bite

Answer 22

Occurs when there is no incisor contact and no incisor overbite

Eg from dummy / suck thumb

Question 23

Crossbite

Answer 23

A transverse abnormality of the dental arches where there is an asymmetrical bite

Unilateral / bilateral

(Some teeth over and some under)

Question 24

What are guidance teeth?

Answer 24

The teeth that determine the movement of the jaw

• incisal guidance
• canine guidance
• group function

Question 25

Occlusal examination - what do we look for

Answer 25

Extra oral examination - skeletal pattern

Intra oral examination -
- soft tissue factors
- generally shape of arches
- missing teeth
- crowding / cross bite
- occlusal relationships - Angles incisor
- guidance teeth / presence of interferences

Use of articulating paper / study models

Question 26

Orthodontics

Answer 26

directed towards alteration of the occlusion of the teeth and the jaw relationships

Question 27

Periodontics
- does it affect occluding surfaces of teeth?

Answer 27

Periodontal disease does not directly affect the occluding surfaces of the teeth.

Trauma from the occlusion has been linked with periodontal disease for many years

Despite extensive research over many years, the role of occlusion in the aetiology and pathogenesis of inflammatory periodontitis is still not fully understood

There is no scientific evidence to show that trauma from occlusion causes gingivitis or periodontitis

The p’d ligament physiologically adapts to increased occlusal loading by resorption of the alveolar crestal bone resulting in increased tooth mobility

Occlusal trauma may be a co-factor which can increase the rate of progression/mobility of an existing periodontal disease

Question 28

Why is occlusion important in paediatric dentistry?

Answer 28

The difference between paediatric dentistry and most other branches of dentistry is that in the child the occlusion is changing

In children we have to make the right clinical decisions for the future occlusion

Question 29

Issues within paediatric dentistry

Answer 29

• premature loss of primary teeth = shifting of midline / disruption of developing occlusion
• submerging teeth
• premature loss of a first permanent molar
• missing permanent tooth
• prevention of crowding in the permanent dentition
• decision to restore / extract