4 - Local causes of malocclusion

Question 1

Define a local cause of malocclusion.

Answer 1

Localised problem or abnormality within either arch, usually caused by one, two or several teeth producing a malocclusion

Question 2

What are categories of local causes of malocclusion?

Answer 2

• variation in tooth number
• variation in tooth size or morphology
• tooth position
• abnormalities of soft tissues
• local pathology

Question 3

Describe different ways in which tooth number can vary.

Answer 3

• supernumerary teeth
• hypodontia
• retained primary teeth
• early loss of primary teeth
• unscheduled loss of permanent teeth

Question 4

What are supernumerary teeth?

Answer 4

• tooth or tooth like structure which is additional to the normal amount of teeth
• most commonly found in anterior maxilla
• more common in males

Question 5

What are the different types of supernumerary teeth?

Answer 5

• conical
• tuberculate
• supplemental
• odontome

Question 6

Describe a conical supernumerary tooth.

Answer 6

• small, peg shaped
• close to midline
• may erupt
• do not prevent eruption but can displace adjacent teeth

Question 7

Describe a tuberculate supernumerary tooth.

Answer 7

• do not erupt
• paired
• barrel shaped
• can cause permanent upper incisors to not erupt
• usually extracted

Question 8

Describe a supplemental supernumerary tooth.

Answer 8

• extra tooth with normal morphology
• most commonly upper laterals or lower incisors (can be premolars)
• usually extracted based on treatment plan

Question 9

Describe an odontome supernumerary tooth.

Answer 9

• two types, compound and complex
• compound are discreet denticles
• complex are a disorganised mass of dentine, pulp and enamel
• require extraction
• can prevent eruption of surrounding teeth

Question 10

Define hypodontia.

Answer 10

Developmental absence of one or more teeth

Question 11

Describe the prevalence of hypodontia.

Answer 11

• more common in females
• hereditary
• most commonly affects upper laterals and second premolars

Question 12

When should you investigate retained primary teeth?

Answer 12

Difference of more than 6 months between exfoliation of contralateral teeth

Question 13

What are causes of retained primary teeth?

Answer 13

• absent successor
• ectopic successor or dilacerated
• ankylosed primary molars (can become infraoccluded)
• delayed development
• pathology
• supernumerary

Question 14

What is the management for an absent successor?

Answer 14

• maintain primary tooth as long as possible
• extract early to encourage spontaneous space closure

Question 15

Define an infra-occluded primary molar.

Answer 15

• process where tooth fails to achieve or maintain occlusal relationship with opposite teeth
• tooth appears to become more submerged under gingiva

Question 16

Define slight infra-occlusion.

Answer 16

Between occlusal surface and interproximal contact, less than 2mm

Question 17

Define moderate infra-occlusion.

Answer 17

Within occluso-gingival margins of interproximal contact

Question 18

Define severe infra-occlusion.

Answer 18

Below interproximal contact point

Question 19

What are the causes of early loss of primary teeth?

Answer 19

• trauma
• periapical pathology
• caries
• resorption by successor

Question 20

Define a balancing extraction.

Answer 20

• extraction of tooth from opposite side of side arch
• designed to minimise midline shift

Question 21

Define a compensating extraction.

Answer 21

• extraction of tooth from opposing arch of the same side
• designed to maintain occlusal relationship

Question 22

What is the management of early loss of primary incisors?

Answer 22

• little impact
• no compensating or balancing extraction

Question 23

What is the management of early loss of primary canines?

Answer 23

• unilateral loss in crowded arch can cause midline shift
• consider balancing extraction

Question 24

What is the management of early loss of primary molars?

Answer 24

• more space loss with Es than Ds
• more space loss in upper than lower (roots are mesial of crown so tilt more easily)
• 6s drift mesially and impinge on space for 5s
• no compensating extraction

Question 25

At what age do you assess prognosis of 6s?

Answer 25

8-9 years

Question 26

How does loss of 6s affect the upper arch?

Answer 26

Potential for rapid space loss

Question 27

How does loss of 6s affect the lower arch?

Answer 27

- spaced dentition will be left with spaces - aligned dentition will be left with spaces - crowded dentition will be left more aligned if extracted early

Question 28

What effect does timing have on the unscheduled loss of permanent central incisors?

Answer 28

- early results in drift of adjacent teeth - late results in permanent space

Question 29

How should you manage unscheduled loss of permanent central incisors?

Answer 29

- reimplant - simple denture - if lateral shift, reopen space for prothesis or build up lateral to mimic central

Question 30

Define macrodontia.

Answer 30

- tooth is larger than average - can be localised or generalised - causes issues with crowding, asymmetry and aesthetics

Question 31

Define microdontia.

Answer 31

- tooth smaller than average - can be localised or generalised - leads to spacing - linked with hypodontia - genetic link - can be managed by composite bonding

Question 32

Describe the different abnormal forms teeth can take.

Answer 32

- peg laterals - dens in dente (communication to pulp from enamel) - geminated teeth - talon cusp - dilaceration - accessory cusps or ridges

Question 33

What teeth are more commonly ectopic?

Answer 33

- 8s - upper 3s - 6s - upper 1s

Question 34

Where are ectopic canines typically found?

Answer 34

80% palatal

Question 35

What circumstances are ectopic canines typically associated with?

Answer 35

- class 2 div 2 - small or absent upper laterals - due to long path of eruption

Question 36

What makes up the clinical assessment for ectopic canines?

Answer 36

- palpate for buccal canine bulge from 9 years - inclination of laterals (distally) - mobility of c or 2s - colour of c or 2s

Question 37

How are radiographs used to assess ectopic canines?

Answer 37

- 2 required, OPT and upper anterior oblique occlusal - parallax technique (canine moves up = palatal side)

Question 38

What are the management options of ectopic canines?

Answer 38

- prevention - extract C to encourage 3 to erupt in correct position (interceptive) - retain and accept position - surgical exposure and orthodontic alignment - surgical extraction - autotransplantation

Question 39

Describe ectopic 6s.

Answer 39

- uncommon - more common in upper - reversible before age of 8 - caries risk

Question 40

What does an ectopic 6 indicate?

Answer 40

- crowding (common in CLP) - mesial path of eruption - abnormal morphology of Es

Question 41

How you manage ectopic 6s?

Answer 41

- distalise 6s - extract Es or allow to exfoliate

Question 42

Define transposition.

Answer 42

Interchange in position of two teeth

Question 43

What are the classes of transposition?

Answer 43

- true = crown and root aligned - pseudo = crown has moved position but roots are crossed

Question 44

Where are transpositions most common?

Answer 44

- upper 3s and 4s - lower canines and incisors

Question 45

What are the treatment options for transpositions?

Answer 45

- accept - extract - (correct)

Question 46

What are the soft tissue causes of malocclusion?

Answer 46

- digit sucking - tongue thrust - frenum - lip strap

Question 47

What are the consequences of digit sucking?

Answer 47

- proclined upper incisors - retroclined lower incisors - AOB - unilateral posterior crossbite (due to narrowed maxillary arch)

Question 48

How can a labial frenum influence tooth position?

Answer 48

Can cause median diastema

Question 49

What are the consequences of a tongue thrust?

Answer 49

AOB which relapses if treated

Question 50

What local pathology can effect tooth position?

Answer 50

- caries - cysts - tumours

Question 51

How can cysts impact tooth position?

Answer 51

- cause resorption of roots - move roots