Class III malocclusion

Question 1

Class 3 incisor relationship BSI definition

Answer 1

lower incisors edges occlude anterior to the cingulum plateau of the upper central incisors
overjet is reduced or reversed

Question 2

Class 3 incisor relationship - incidence

Answer 2

uk 3-7%
higher incidence in Asia

Question 3

Class iii aetiology

Answer 3

strong genetic link
- Habsburg family
environmental factors
- cleft lip and palate
acromegaly

Question 4

Class 3 incisor relationship - skeletal features

Answer 4

usually present with a class 3 skeletal base
can present with a class 1 and rarely a class 2 skeletal base
the greater the a-p discrepancy the more difficult treatment is

Question 5

Class 3 dental features

Answer 5

tendency to reverse overjet
class 3 molar relationship (not always)
reduced overbite
- anterior open bite may be present
crossbites
- anterior
- buccal
alignment
- mandible often aligned or spaced
- maxilla often crowded
dentoalveolar compensation
- proclined upper incisors
- retroclined lower incisors
tendency for displacement on closing

Question 6

Reasons for treating a class 3

Answer 6

aesthetics
- dental
- profile concerns
dental health reasons
- attrition
- gingival recession
- mandibular displacement
function
- speech
- mastication

Question 7

Factors which affect the difficulty of treating a class 3 malocclusion

Answer 7

number of teeth in anterior cross bite
skeletal element in aetiology
the degree of ap discrepancy
presence of an anterior open bite

Question 8

Why does facial growth make treating a class 3 malocclusion more difficult?

Answer 8

tends to be unfavourable
- mandibular growth continues for longer
- potential for class 3 to become worse

Question 9

When would you accept and monitor a class 3 occlusion

Answer 9

no patient concerns
no dental health indications
- no displacements
- no attrition
mild cases

Question 10

When would interceptive treatment be suitable for treatment of a developing class 3 malocclusion and why?

Answer 10

suitable if class 3 incisors have developed due to early contact on permanent incisors (i.e mandibular displacement)
- correction of anterior crossbite in mixed dentition has the advantage that further forward mandibular growth may be counter balanced by some dento-alveolar compensation
- only suitable for correcting a lateral incisor crossbiet if permanent canines are high above lateral roots

Question 11

interceptive treatment for class 3

Answer 11

URA to procline incisors over the bite

Question 12

Class 3 growth modification indications and aims

Answer 12

indications = growing patient
aims
- reducing and/or redirecting mandibular growth
- encouraging maxillary growth

Question 13

class 3 growth modification appliances - give examples

Answer 13

functional appliances
- chin cup
- reverse twin block
- Frankel III
protraction headgear +/- rapid maxillary expansion
bollard implants (late mixed and permanent dentition)

Question 14

Chin cup features

Answer 14

mainly historic treatment form
lingual tipping of lower incisors
rotates mandible down and backwards

Question 15

Frankel III features

Answer 15

pellotes (shields) placed labial to upper incisors to hold lip away
palatal arch to proline upper incisor
Lower labial bow to retrocline lower incisors

Question 16

protraction headgear indications, use and features

Answer 16

co-operative patient
worn for 14 hours a day
400g force per side
best results in early mixed dentition (8-10 years)
+/- rapid maxillary expansion
- disrups circus-maxillary sutures

Question 17

orthodontic camouflage aims

Answer 17

accept underlying skeletal base relationship
- aim for class 1 incisor relationship by:
- procline upper incisors
- retrocline lower incisors
- correct overjet

Question 18

Orthodontic camouflage for class 3 - indications

Answer 18

growth stopped
mild to moderate class 3
- ANB >0 degrees
average or increased overbite
able to reach edge to edge incisor relationship
little or no dentoalveolar compensation

Question 19

class 3 orthodontic camouflage extraction pattern

Answer 19

extract further back in upper arch
extract further forward in lower arch
classic pattern
upper 5s, lower 4s
not always possible as dental health may dictate extraction pattern

Question 20

orthognathic treatment indications

Answer 20

patient has aesthetic or functional concerns
growth completed
moderate to severe skeletal discrepancy

Question 21

orthognathic surgical treatment requirements

Answer 21

careful planning
multidisciplinary team approach
- orthodontist
- maxilofacial surgeon
- technician
- psychologist
prediction planning software

Question 22

orthognathic treatments steps

Answer 22

pre surgical orthodontics to level, align, co-ordinate and decompensate (18 months)
- uppers 109 degrees
- lower incisors 90 degree inclination
orthognathic surgery to reposition the jaws
- mandible
- mandible and maxilla
post surgical

Question 23

GDP role in treatment for class 3

Answer 23

identify class iii malocclusion
refer to hospital service or specialist practitioner
URA treatment
- anterior crossbite correction