Aetiology of Malocclusion 2 - Local Causes

Question 1

Define a local problem

Answer 1

A problem or abnormality within either arch, usually confined to one, two or several teeth producing a malocclusion

Question 2

What are the common local causes of malocclusion

Answer 2

Variation in tooth number
Variation in tooth size or form
Abnormalities of tooth position
Local abnormalities of soft tissues
Local pathology

Question 3

How can tooth number vary?

Answer 3

Supernumerary teeth (extra)
Hypodontia (developmentally absent teeth)
Retained primary teeth
Early loss of primary teeth
Unscheduled loss of permanent teeth

Question 4

What is a supernumerary tooth?

Answer 4

A tooth or tooth-like entity which is additional to the normal series

Question 5

Describe the prevalence of supernumerary teeth

Answer 5

Most common in anterior maxilla
Affects males over females
1% in primary dentition
2% in permanent dentition

Question 6

What are the different types of supernumerary teeth?

Answer 6

Conical
Tubercular
Supplemental
Odontome

Question 7

Describe conical supernumerary teeth

Answer 7

Small, pg shaped
Close to midline
May erupt
Usually 1 or 2 in number
Tend not to prevent eruption but may displace adjacent teeth

Question 8

Describe tubercular supernumerary teeth

Answer 8

Tend not to erupt
Paired
Barrel shaped
Usually extracted
One of the main causes of eruption of permanent upper incisors

Question 9

Describe supplemental supernumerary teeth

Answer 9

Extra teeth of normal morphology
Most often upper laterals or lower incisors
Can be third premolars, fourth molars
Often extracted - decision based on form and position

Question 10

Describe odontome supernumerary teeth

Answer 10

Can be:
Compound - discreet denticles
Complex - disorganised mass of dentine, pulp and enamel

Question 11

Describe the prevalence of hypodontia

Answer 11

Affects females over males, 3:2
Affects 4-6% of population (excluding 8s)
Commonly upper laterals and second premolars

Question 12

When should retained primary teeth cause concern?

Answer 12

A difference of more than 6 months between the shedding of contralateral teeth

Question 13

What are the reasons for retained primary teeth?

Answer 13

Absent successor
Ectopic successor or dilacerated
Infra-occluded (ankylosed) primary molars
Dentally delayed in terms of development
Pathology/supernumerary

Question 14

How should retained primary teeth be managed if the successor is absent?

Answer 14

Either maintain primary tooth as long as possible if good prognosis
Or extracte deciduous tooth early to encourage spontaneous space closure in crowded cases
Get orthodontic referral for advice

Question 15

What is a submerged tooth?

Answer 15

When a tooth fails to achieve or maintain its occlusal relationship with adjacent teeth

Question 16

Describe infra-occluded primary molars

Answer 16

Submerged
Temporary ankylosis
Affects 1-9% of people
Tooth gives percussive sound

Question 17

What are the reasons of early loss of primary teeth?

Answer 17

Trauma
Periapical pathology
Caries
Resorption by successor

Question 18

What is balancing extraction?

Answer 18

Extracting a tooth from the opposite side of the same arch to minimise midline shift

Question 19

What is compensating extraction?

Answer 19

Extracting a tooth from the opposite arch of the same side to maintain occlusal relationship

Question 20

What impact does early loss of primary incisors have?

Answer 20

Very little impact
No compensating or balancing extraction necessary

Question 21

What impact does the early loss of primary canines have?

Answer 21

Unilateral loss in crowded arch can give centre-line shift
Will get some mesial drift of buccal segments
Consider balancing extraction

Question 22

What impact does the early loss of primary molars have?

Answer 22

More space loss with E’s than D’s
More space loss in upper than in lower
6s drift mesially and steal 5’s space

Question 23

What percent of people in the UK are affected by malocclusion?

Answer 23

68%

Question 24

What are the different categories of causes of malocclusion?

Answer 24

Skeletal - class III
Dental - missing teeth
Soft tissue - lip trap
Other - habits

Question 25

How can unscheduled loss of 6s be prevented?

Answer 25

Routine assessment of 6’s prognosis happens at age 8-9
Planned loss at correct age is better than later enforced loss

Question 26

What influences the impact of the loss of 6’s?

Answer 26

Age at loss
Crowding
Malocclusion

Question 27

What happens if 6s are lost too early or late?

Answer 27

Upper arch is less important
Lower arch:
Late - if 7s erupted then there is often poor space closure
Early - distal drift of 5s particularly if E’s lost at the same time as 6’s

Question 28

How does unscheduled loss of 6’s affect crowding?

Answer 28

Upper arch - potential for rapid space loss
Lower arch - if spaces present or teeth are aligned - will have spaces, if crowding present already - best results likely

Question 29

What are the impacts of early and late unscheduled loss of central incisors?

Answer 29

Early will result in drift of adjacent teeth
Late will result in a long term space

Question 30

How is the unscheduled loss of a central incisor treated?

Answer 30

Ideally maintain space by re implanting or providing a simple denture