Class 3

Question 1

What is class 3 defined as

Answer 1

Lower incisor edge occludes anterior to the cingulum plateau of the upper central incisor
Overjet is reduced or reversed
Least common incisor classification

Question 2

What is the aetiology of class 3 split into

Answer 2

genetics
environmental factors
skeletal
dental
soft tissues

Question 3

What is the genetic aetiology for class 3

Answer 3

Strong genetic link but pattern of transmission is controversial

Question 4

What is the environmental aetiology for class 3

Answer 4

Higher incidence in those with cleft lip/palate & acromegaly

Question 5

What is the most common skeletal AP relationship in class 3

Answer 5

Class 3 skeletal relationship most common but can occur on class 1 or class 2 base
The greater the AP discrepancy, the harder it is to treat

Question 6

What can the class 3 ap skeletal base be due to

Answer 6

Small maxilla
Large mandible
Combination of both

Question 7

What is the vertical skeletal features that can contribute to the aetiology

Answer 7

Can present with average, increased or reduced FMPA & facial height proportions
If the patient has increased FMPA angle, increased vertical facial proportions and particularly if they have an anterior open bite then it makes the class III malocclusion much more difficult to manage

Question 8

What are the transverse skeletal features that may be seen with class 3

Answer 8

The AP and transverse relationship are linked
It is common to have a small maxilla and if it is then the narrower part of the maxilla sits against the wider part of the mandible resulting in buccal bilateral crossbites

Question 9

What dental features contribute to the aetiology

Answer 9

class III molar relationship (not always)
tendency for reverse overjet
reduced overbite, anterior open bite may be present
may see anterior or buccal crossbites
alignment - maxilla is often crowded and mandible is often aligned or spaced
dentoalveolar compensation
mandibular displacement is common on closing especially with milder class 3 malocclusion

Question 10

What is the dentoalveolar compensation seen in class 3

Answer 10

Proclined upper incisors
Retroclined lower incisors

Question 11

Do soft tissues have any involvement in aetiology

Answer 11

o Not usually involved in aetiology
o However they do encourage dentoalveolar compensation:
Tongue prolines the upper incisors
Lower lip retroclines lower incisors

Question 12

When is a class 3 case complex

Answer 12

if these features present
 > number of teeth in anterior xbite
 Skeletal element in aetiology
 > the AP discrepancy
 Presence of AOB

Question 13

What are treatment considerations we need to think off

Answer 13

treatment difficulty
facial growth
growth status

Question 14

What should we consider regarding facial growth prior to tx

Answer 14

o Unfavourable
o Mandibular growth continues for longer so potential for it to get worse
o Do not do anything irreversible until growth has stopped as it could effect future tx if surgery is required

Question 15

What should we consider regarding growth status prior to tx

Answer 15

o The onset of pubertal growth spurt coincides with a spurt in the jaw so it is helpful if we can predict when pubertal growth spurt is going to occur
o Most reliable method is using height and weight charts
o If in doubt, watch and wait, as there is individual variation

Question 16

What are the reasons for treating class 3

Answer 16

aesthetics
dental health reasons
function

Question 17

What are the aesthetic concerns

Answer 17

dental
profile

Question 18

What are the dental health reasons for tx

Answer 18

attrition
gingival recession
mandibular displacement

Question 19

Why are class 3 prone to attrition

Answer 19

Can cause wear on labial face of upper incisors and lingual face of lower incisors

Question 20

Why are class 3 prone to gingival recession

Answer 20

If upper incisors occluding heavily on inside of lower incisors as it can push the roots of the lower incisors through the buccal plate

Question 21

Why is mandibular displacement problematic

Answer 21

Long term TMJ problems

Question 22

What are the treatment options for class 3

Answer 22

accept
interceptive
growth modification
camouflage
orthognathic surgery

Question 23

When is it a good idea to accept

Answer 23

no aesthetic concerns
no dental health indications
mild cases

Question 24

When is interceptive treatment suitable

Answer 24

if class III incisors have developed due to early contact on the permanent incisors – edge to edge (i.e mandibular displacement) – can treat early on

Question 25

Why is correction of anterior crossbite early on advantageous

Answer 25

that further forward mandibular growth may be counter balanced by some dentoalveolar compensation

Question 26

What device would be used for treatment of anterior xbite

Answer 26

URA
z spring used

Question 27

What makes a patient suitable for growth modification

Answer 27

must be growing

Question 28

What is the aim of growth modification

Answer 28

to reduce/redirect mandibular growth and encourage maxillary growth

Question 29

What are the different functional appliances

Answer 29

chin cup
frankel 3
reverse twin block
protraction headgear
bollard implants

Question 30

What is frankel 3

Answer 30

Labial shield holds upper lip away from incisors to let them procline
Palatal arch pushes against the upper incisors
Labial bow used to retrocline
Not favoured anymore

Question 31

What is reverse twin block

Answer 31

Blocks slope in opposite direction of the class 2 traditional twin block
Hard to construct
Works best for patients who are edge to edge at the start of tx
Mainly has a dentoalveolar effect on the teeth

Question 32

What is protraction headgear

Answer 32

• Only for the cooperative patient
• Best results in early mixed dentition
• Can be used with or without RME

Question 33

What are bollard implants

Answer 33

• Used in late mixed and permanent dentition
• Infrazygomatic crest and lower canine region
• Mucoperiosteal flaps need to be raised for insertion and removal

Question 34

What is camouflage

Answer 34

o Accepting underlying skeletal base relationship and aiming for class 1 incisors

Question 35

What are the favourable features for camouflage

Answer 35

 Growth stopped
 Mild to moderate class 3 skeletal base (ANB not <0)
 Average/increased overbite
 Able to reach edge to edge incisor relationship
 Little or no dentoalveolar compensation

Question 36

What is the extraction pattern for class 3

Answer 36

Extract further back in upper arch and further forward in lower arch
Classic pattern = upper 5s/lower 4s
However dental health may dictate extractions

Question 37

What are the aims of camouflage in class 3

Answer 37

Procline upper incisors
Retrocline lower incisors
Correct OJ

Question 38

Why should you not do camouflage in a growing patient

Answer 38

Can not predict growth changes, px may require surgery in future and extraction/tooth movements may cause problems and require to be undone
Consider upper arch aligment only
Do not XLA in the lower arch as this could affect future tx options

Question 39

What is orthognathic surgery

Answer 39

Surgical manipulation of the mandible and/or maxilla to produce optimal dentofacial aesthetics and function

Question 40

What are the indications for orthognathic surgery

Answer 40

Px usually has aesthetic or functional concerns
Growth is completed
Moderate/severe skeletal discrepancy often with increased vertical dimension

Question 41

What is done in the presurgical orthodontics

Answer 41

Level, align, coordinate and decompensate (getting rid of curve of spee)
Uppers 109 degrees
Lower 90 degrees