Class 3

Question 1

What is Class 3?

Answer 1

• lower incisors occlude anterior to the cingulum plateau of upper central incisor
• OJ is reduced/ reversed

Question 2

Incidence

Answer 2

• geographical variation
• UK 3-7 %
• higher incidence in Asia

Question 3

Aetiology

Answer 3

• strong genetic link
• Habsburg family
• pattern of transmission

Environment factors
- cleft lip and palate
- acromegaly

1. skeletal
2. dental
3. ST

Question 4

Skeletal A/P

Answer 4

• small maxilla
• large mandible
• combination of both
• usually present with class 3 skeletal base
• can present as class 1/ class 2
• greater A/P discrepancy, more complex the malocclusion is

Question 5

Vertical Sk

Answer 5

• increase FMPA and anterior Openbite is more complex to treat

Question 6

Transverse relationship

Answer 6

• retrusive maxilla sits on wider part of mandible
• bilateral CB

Question 7

Dental features of Class 3

Answer 7

• class 3 incisor relationship
• class 3 molar relationship
• tendency to reverse OJ
• reduced overbite, anterior openbite
• crossbite (anterior/ buccal)
• maxilla often crowded
• mandible often aligned/ spaces
• proclined upper incisors
• retroclined lower incisors
• tendency for displacements on closing

Question 8

Soft tissues

Answer 8

• not usually involved in aetiology
• encourage dentoalveolar compensation
• tongue will procline upper incisors, and lip trap will retrocline lowe incisors

Question 9

Why treat?

Answer 9

1. aesthetics
2. dental health reasons due to attrition and gingival recession, mandibular displacement
3. function, ie: speech and mastication

Question 10

Factors which make tx more difficult?

Answer 10

• number of teeth in anterior crossbite
• sk element in aetiology
• higher the A/P discrepancy
• presence of anterior openbite

Question 11

Facial growth for class 3

Answer 11

• mandibular growth tends to continue longer
• potential for class 3 to get worse
• tends to be unfavourable

Question 12

Class 3 management options

Answer 12

1. accept/ monitor - mild class 3/ unsure how growth and development will progress
2. intercept early with URA- early correction of incisor relationship
3. growth modification - functional appliance/ head gear/ TADs
4. Camouflage - accept underlying sk, correct incisors to class 1
5. combined orthognathic and ortho- functional/ masticatory/ profile concerns

Question 13

Accept and monitor

Answer 13

• no concerns
• no dental health indications
• no displacements
• no attrition
• mild cases

Question 14

Interceptive tx

Answer 14

• suitable if class 3 incisors have developed due to early contact on permanent incisors
• correction of anterior CB in mixed dentition has the advantage that further forward mandibular growth may be counter balanced by dento-alveolar compensation
• only suitable for correcting lateral incisor CB if permanent canine are higher above lateral roots; if drop down to buccal position then risk of RR

Question 15

What to use in interceptive tx?

Answer 15

• URA to procline incisors over bite
• good overbite will maintain stability

Question 16

Growth modification

Answer 16

• growing pt
• aim at reducing/ redirecting mandibular growth and encourage maxillary growth

Question 17

Functional appliances for Class 3

Answer 17

• Chin cup
• Reverse twin block
• Frankel 3
• protraction headgear +/- rapid maxillary expansion

Question 18

Chin cup

Answer 18

• lingual tipping of lower incisors
• rotates mandible down and back

Question 19

Frankel 3

Answer 19

• shields labial to upper incisors to hold lip away
• palatal arch to rpocline upper incisors
• lower labial bow to retrocline lower incisors

Question 20

Reverse twinblock

Answer 20

Question 21

Protraction headgear

Answer 21

• cooperative pt
• 14/day protraction facemask wear
• 400g/side
• used in early mixed dentition (8-10)
• may include rapid maxillary sutures

Question 22

Bollard implants

Answer 22

• used in late mixed and permanent dentition
• infrazygomatic crest and lower canine region
• mucoperiosteal flaps need to be raised for insertion and removal

Question 23

Orthodontic camouflage

Answer 23

• accept underlying skeletal base relationship
• aim for class 1 incisors

Question 24

Favourable features for camouflage

Answer 24

• mild to moderate class 3 ANB not < 0
• growth complete
• average to increased overbite
• able to reach edge to edge incisor relationship
• little or no dentoalveolar compensation

Question 25

Multidisciplinary approach in Orthognathic surgery

Answer 25

• orthodontist
• maxillofacial surgeon
• technician
• psychologist

Question 26

GDP role

Answer 26

• identify class 3 malocclusion
• refer to hospital service/ specialist practitioner
• provide URA for anterior crossbite correction