Aetiology of Malocclusion 2 - Local Causes, Part 2

Question 1

How can teeth vary in size or form?

Answer 1

Too large - macrodontia
Too small - macrodontia
Abnormal form

Question 2

Describe macrodontia

Answer 2

Tooth/teeth larger than average
Can be localised or generalised
Can cause crowding, asymmetry and aesthetic problems

Question 3

Describe microdontia

Answer 3

Tooth/teeth smaller than average
Localised or generalised
Leads to spacing
Linked to hypodontia

Question 4

Give examples of abnormal form of teeth

Answer 4

Peg shaped laterals
Dens in dente
Germinated/fused teeth
Talon cusps
Dilaceration
Accessory cusps and ridges

Question 5

Which teeth are most likely to be ectopic?

Answer 5

Third molars (8s)
Upper canines (3s)
First permanent molars (6s)
Upper centrals (1s)

Question 6

Describe the prevalence of ectopic maxillary canines

Answer 6

Affects 1-3% of population
80% are palatal

Question 7

Describe ectopic canines

Answer 7

Have a long path of eruption (eye teeth)
Palatal canines often occur in well aligned arches
Higher incidence in absent/peg shaped laterals and in class II div 2 incisor relationship
Buccal canines more associated with crowding

Question 8

What happens in a clinical assessment of ectopic canines?

Answer 8

1. Visualisation/palpating of any obvious bumps of 3
2. Inclination of 2s
3. Mobility of Cs or 2s
4. Colour of Cs or 2s

Question 9

How are ectopic canines found on radiographs?

Answer 9

2 radiographs needed to localise position - usually OPT and upper anterior oblique occlusal
Use parallax technique: 3 Ps - presence, position, pathology

Question 10

What are the management options for ectopic canines?

Answer 10

Prevention
Extraction of c to encourage improvement in position of 3 (interceptive)
Retain 3 and observe (accept its position)
Surgical exposure and orthodontic alignment
Autotransplantation

Question 11

What aids in prevention of ectopic canines?

Answer 11

Appropriate monitoring from age 9 onwards
Clinical assessment
Symmetry

Question 12

How are palatally ectopic canines treated?

Answer 12

Surgically exposed and aligned with fixed appliances

Question 13

Describe the prevalence of ectopic first molars

Answer 13

Affects less than 5% of population
Reversible before the age of 8
Caries risk

Question 14

What are the signs of ectopic first molars?

Answer 14

Crowding (greater in cleft lip and palate)
Mesial path of eruption
Abnormal morphology of E

Question 15

How can ectopic first molars be managed?

Answer 15

1. Separator
2. Attempt to distalise 6
3. Extract E

Question 16

How can ectopic upper central incisors be prevented?

Answer 16

Check for sequence and symmetry

Question 17

What are the possible causes of ectopic upper central incisors?

Answer 17

May be no obvious cause
Supernumerary - tuberculate or odontome
Trauma to primary predecessor - ankylosis of primary tooth, displacement of tooth germ, dilaceration of tooth

Question 18

What are transpositions and how are they classed?

Answer 18

Interchange in the position of two teeth
Can be true or pseudo

Question 19

Which teeth are most commonly affected by transposition?

Answer 19

Upper canines and first premolar
Lower canines and incisors

Question 20

What are the treatment options for transpositions?

Answer 20

Accept
Extract
Correct

Question 21

Give examples of causes of local abnormalities of soft tissues?

Answer 21

Digit sucking
Fraenum
Tongue thrust

Question 22

What may be caused by a non-nutritional digit sucking habit?

Answer 22

Proclined upper incisors
Retroclined lower incisors
Anterior open bite
Unilateral posterior crossbite - due to narrow maxillary arch, may cause mandibular displacement

Question 23

What is the negative consequence of a labial frenum?

Answer 23

May cause a median diastema

Question 24

Which local pathology may cause malocclusion?

Answer 24

Caries
Cysts
Tumours