Aetiology Malocclusion - Local Cause

Question 1

What are the dental causes?

Answer 1

Tooth: tissue ratio
Number of teeth - linked dental arch length 
Abnormal form or position of teeth
Path closure
Pathology e.g cyst 

PR NAP

Question 2

How does tooth:tissue ratio cause malocclusion?

Answer 2

Imbalance of ratio teeth and jaw size can produce crowding or spacing

Question 3

What are aetiological factors in crowding?

Answer 3

Genetic - independent genetic control teeth/ evolution/ inter-mixing of racial or ethnic group
Environmental - diet

Question 4

What is prevalence of crowding?

Answer 4

Affect 60-70% population - depend ethnic group

Crowding deciduous dentition unusual

Question 5

Effects of crowding on dentition?

Answer 5

Overlapping, displacement, impaction, mesial movement of teeth

Question 6

Difference between anodontia, hypodontia and supernumerary?

Answer 6

Anodontia - no teeth
Hypodontia - few missing
Supernumary/ supplemental - extra

Question 7

Prevalence wrong no/ teeth and where is it common?

Answer 7

3-7% population

Affect end of series teeth most commonly

Question 8

What is severe hypodontia/ aetiology?

Answer 8

Type of ectodermal dysplasia - sex-linked recessive condition

Question 9

What can severe hypodontia be linked to?

Answer 9

Often smaller teeth - spacing

Affect alveolar bone and increase freeway space

Question 10

What are different types of supernumerary teeth and what % of population affected?

Answer 10

2%

Conical (mesiodens) - usually between 1/1 - often erupt and displace other teeth
Tuberculate - barrel shaped, don’t usually erupt - prevent eruption other teeth
Supplemental - resemble normal teeth, occur end of series and cause crowding

Question 11

How can premature loss of primary teeth affect malocclusion?

Answer 11

Incisors - little effect
Loss C - shift of centre line to XLA side
Loss D - can lead centre line shift
Loss E - first. perm molar moves medially - space loss greater in upper arch

Question 12

How can retention of primary teeth affect malocclusion?

Answer 12

Permanent teeth can become deflected - XLA primary teeth if necessary

Question 13

What should you look for if delayed eruption permanent teeth?

Answer 13

Normal variation, missing teeth, impeded eruption, supernumerary

Question 14

What is a submerged tooth?

Answer 14

Infra-occluded
Associated: missing perm teeth, ankylosed primary tooth
May need surgical XLA as can prevent eruption other teeth

Question 15

What are different abnormal forms of teeth?

Answer 15

1. Macrodontia - large (have large pulp chambers)
2. Microdontia - often seen upper lateral incisors
3. Peg-shaped lateral - associated ectopic canines

Question 16

What are different positions of teeth?

Answer 16

1. Transposition - teeth swap - common 3/4

2. Impaction

Question 17

How can lateral displacement of path of closure affect malocclusion?

Answer 17

If maxilla narrower than mandible - meet cusp-cusp –> no engaged occlusion
For inter-cuspation - lower jaw needs to shift for intercuspation
Often seen pt w/ cross bite

Question 18

How can forward displacement of path of closure affect malocclusion?

Answer 18

e.g Class III incisor

Have to bring mandible forwards to occlude