Classification of Malocclusion

Question 1

What is malocclusion?

Answer 1

An appreciable deviation from the ideal occlusion that may be considered aesthetically or functionally unsatisfactory

Question 2

Name 4 reasons for treating malocclusions

Answer 2

1. Dentofacial aesthetics
2. Dental health (trauma, OH, periodontal health)
3. Functional (TMJ, speech, eating)
4. Facilitate restorative treatment

Question 3

Describe the prevalence of malocclusion

Answer 3

• 35% normal / 65% a malocclusion
• Class I Incisors (50%)
• Class II Div 1 Incisors (35-40%)
• Class II Div 2 Incisors (10%)
• Class III Incisors (3-5%)

Question 4

Describe 3 reasons for orthodontic diagnosis

Answer 4

1. Description of problems
2. Help with treatment planning
3. Epidemiology and prioritising treatment needs

Question 5

Describe 3 features of malocclusion with regards to malposition of individual teeth

Answer 5

1. Crowding
2. Rotations
3. Unerupted / absent teeth

Question 6

Describe 3 features of malocclusion with regards to malrelationship of the arches

Answer 6

1. Anteroposterior
2. Transverse
3. Vertical

Question 7

Describe the extra-oral orthodontic examination

Answer 7

View jaw relationship in 3 dimensions: Anteroposterior, transverse and vertical

Question 8

Describe the intra-oral orthodontic examination

Answer 8

• Intra-arch alignment

- Arch relationships in anteroposterior, vertical and transverse dimensions

Question 9

Describe an anteroposterior relationship between the arches on an extra-oral examination

Answer 9

Is the mandible more or less protrusive than the maxilla?

Question 10

Describe an vertical relationship between the arches on an extra-oral examination

Answer 10

Is the lower part of the face too long or too short?

Question 11

Describe an transverse relationship between the arches on an extra-oral examination

Answer 11

Is the face symmetrical when viewed from the front?

Question 12

What is an overjet and its normal range?

Answer 12

• Horizontal relationship between the upper incisors and lower incisors (anteroposterior measurement)
• 2 to 4 mm

Question 13

What is an overbite and its normal range?

Answer 13

• Overlap of the upper anterior teeth over the lowers in a vertical plane (vertical measurement)
• 3 to 4 mm

Question 14

Describe how the degree of crowding can be measured

Answer 14

Crowding = Total tooth size - Total arch length

Mild = < 3mm
Moderate = 4-5mm
Severe = > 6mm

Question 15

When does spacing tend to occur?

Answer 15

When teeth are missing

Question 16

Describe 2 components of what an orthodontic diagnosis usually consists of

Answer 16

1. One or more classifications

2. List of other abnormal features with indication of severity

Question 17

What is the function of classifying malocclusion?

Answer 17

Subdivide malocclusions into distinct groups with similar occlusal and facial features

Question 18

What are 4 common classifications of malocclusion?

Answer 18

1. Incisor Classification
2. Skeletal Classification
3. Angle’s Classification
4. Indices (IOTN, PAR)

Question 19

Describe common orthodontic classifications with regards to the 3 dimensions used in an examiantion

Answer 19

• All common classifications based on anteroposterior relationship of teeth and skeletal bases
• Transverse and vertical relationships usually recorded using descriptive methods

Question 20

Describe 4 classifications in Incisor Classification

Answer 20

Class I
Class II Div 1
Class II Div 2
Class III

Question 21

Why is the Incisor Classification most often used?

Answer 21

It is clinically relevant as most patients are concerned about the relationship between their incisors

Question 22

Describe Class I Incisors

Answer 22

• Lower incisor occludes with or lies directly below upper incisor cingulum
• One of the goals of orthodontic treatment

Question 23

Describe Class II Div 1 incisors

Answer 23

• Lower incisor edges palatal to cingulum plateau of upper incisors (increased overjet)
• Upper incisors are proclined or of average inclination

Question 24

Describe Class II Div 2 incisors

Answer 24

• Lower incisor edges are palatal to cingulum plateau of the upper incisors
• Upper incisors are retroclined (long axis of crown is tipped in palatal direction)

Question 25

Describe Class III incisors

Answer 25

- Lower incisor edges lie anteriorly to cingulum plateau of upper incisors - Overjet reduced or reversed

Question 26

Describe 3 categories of Skeletal Classification

Answer 26

Class I Class II Class III

Question 27

What is the Skeletal Classification based on?

Answer 27

Anteroposterior relationship of mandible and maxilla

Question 28

Describe how a Skeletal Classification can be evaluated

Answer 28

Either clinically or cephalometrically but usually done clinically as radiation exposure is not normally necessary

Question 29

Describe Skeletal Class I

Answer 29

- ANB 2-4 degrees - Balanced facial profile - Most common

Question 30

Describe Skeletal Class II

Answer 30

- ANB > 4 degrees - Relative mandibular retrusion - Result of mandibular deficiency or maxillary excess

Question 31

Describe Skeletal Class III

Answer 31

- ANB <2 degrees - Relative mandibular prominence - Result of mandibular excess or maxillary deficiency

Question 32

What is a common cause of a small maxilla?

Answer 32

Cleft lip and palate

Question 33

What is Angle's Classification?

Answer 33

- Based on buccal segment relationship - Relationship of upper and lower first permanent molars - Commonly used in USA but not Europe

Question 34

Describe Angle's Class I

Answer 34

Mesiobuccal cusp of upper first molar occludes with anterior buccal groove of lower first molar

Question 35

Describe Angle's Class II

Answer 35

Lower arch is at least half a cusp's width posterior to Class I

Question 36

Describe Angle's Class III

Answer 36

The lower arch is at least half a cusps width anterior to Class I

Question 37

Describe how units are counted in dentistry

Answer 37

Pre-molar width is one unit and molar width is two units

Question 38

Describe 4 draw backs of Angle's classification

Answer 38

1. Incisor relationship not considered 2. Skeletal pattern not considered 3. First molars may drift or be absent 4. Dividing line between categories is unclear

Question 39

Describe why an orthodontic summary may be useful

Answer 39

- Record summary in notes which builds up picture of malocclusion and main problems - Way of describing patient in logical, sensical, clinical fashion is making referral or describing case

Question 40

Describe 4 components which should be included in an orthodontic diagnosis summary

Answer 40

1. Patient age and gender 2. Incisor classification 3. Skeletal relationship 4. Other features in descending order of importance

Question 41

Name fully 2 main indices of malocclusion used

Answer 41

1. IOTN - Index of Orthodontic Treatment Need | 2. PAR - Peer Assessment Rating

Question 42

Name 4 uses of indices of malocclusion

Answer 42

1. Epidemiology 2. Treatment priority and resource allocation 3. Audit standard of treatment 4. Research

Question 43

Describe 3 criteria which an orthodontic index must fulfil

Answer 43

1. Valid - Measure what they are meant to 2. Reliable - Same result if repeated 3. Easy to use