Class 3 Malocclusion

Question 1

what is the BSI definition of class 3 malocclusion

Answer 1

lower incisor edge occludes anterior to the cingulum plateau of the upper central incisor and the overjet is reduced or reversed

Question 2

what is the incidence of class 3 malocclusion in the UK

Answer 2

3-7%

Question 3

what environmental factors affect class 3 malocclusion

Answer 3

cleft lip and palate
acromegaly

Question 4

what is the AP skeletal relationship which correlates with class 3 malocclusion

Answer 4

class 3 skeletal base - mandible less than 2-3mm behind maxilla

Question 5

what needs to be assessed for the vertical skeletal relationship

Answer 5

FMPA
face height proportions
lateral cephalometry

Question 6

what skeletal features make a class 3 more difficult to treat

Answer 6

greater AP discrepancy
increased FMPA
AOB

Question 7

what transverse skeletal features are seen

Answer 7

retrusive maxilla sits on the wider part of the mandible causing bilateral crossbites

Question 8

what are the dental features of class 3

Answer 8

class 3 incisor relationships
class 3 molar relationship
reverse overjet
reduced overbite, AOB
anterior and buccal crossbites
narrow upper arch can be common
dentoalveolar compensation
displacement on closing

Question 9

what is seen with alignment in class 3

Answer 9

maxilla often crowded
mandible often aligned or spaced

Question 10

what dentoalveolar compensation occurs in class 3

Answer 10

procline upper incisors
retrocline lower incisors

Question 11

what is the soft tissue involvement in class 3

Answer 11

tongue proclines upper incisors
lower lip retroclines lower incisors

Question 12

what are the reasons for treating class 3

Answer 12

aesthetics
dental health
function

Question 13

what dental health reasons would make you want to treat a class 3

Answer 13

attrition
gingival recession
mandibular displacement

Question 14

which factors make treating class 3 difficult

Answer 14

greater number of teeth in anterior crossbite
skeletal element in aetiology
greater AP discrepancy
presence of AOB
facial growth
growth status

Question 15

what is the facial growth like with class 3

Answer 15

mandibular growth continues for a long time and can get worse

Question 16

how can you predict growth

Answer 16

usually coincides with puberty
use height and weight charts
watch and wait

Question 17

what are the management options for class 3

Answer 17

accept/monitor
intercept early with URA
growth modification
camouflage
combined orthognathic surgery and orthodontics

Question 18

when would you accept and monitor a class 3

Answer 18

no concerns
no dental health implications
mild cases

Question 19

when would interceptive treatment be considered for class 3

Answer 19

if class 3 incisors have developed due to early contact on permanent incisors
correction of anterior crossbite
correcting lateral incisor crossbite

Question 20

what is used in interceptive treatment for class 3

Answer 20

URA to procline incisors

Question 21

when is growth modification used

Answer 21

growing patient

Question 22

what is the aim of growth modification

Answer 22

reducing and redirecting mandibular growth and encourage maxillary growth

Question 23

what is used for growth modification

Answer 23

chin cup
reverse twin block
frankel III
protraction headgear

Question 24

what does a chin cup do

Answer 24

lingually tip lower incisors
rotates mandible down and back

Question 25

what is Frankel III

Answer 25

appliance which holds lip away, proclines upper incisors with palatal arch and retroclines lower incisors with labial bow

Question 26

what is a reverse twin block

Answer 26

a twin block which is cut at a different angle than a class block

Question 27

when does a reverse twin block work

Answer 27

in mild class 3
patients who can achieve edge to edge already

Question 28

how is protraction headgear used

Answer 28

14hrs per day
400g force on each side of face
in patients 8-10yrs old

Question 29

what result can protraction headgear achieve

Answer 29

rapid maxillary expansion

Question 30

where are bollard implants placed

Answer 30

infrazygomatic crest and lower canine region

Question 31

what is orthodontic camouflage

Answer 31

accept the skeletal base and aim for class 1 incisor relationship

Question 32

what features are favourable when opting for camouflage

Answer 32

growth has stopped
mild to moderate class 3 AP but ANB not less than 0
average or increased overbite
able to reach edge to edge incisor relationship
little or no dentoalveolar compensation

Question 33

what is the extraction pattern for camouflage

Answer 33

upper 5s and lower 4s

Question 34

what is the aim of orthodontic camouflage

Answer 34

procline uppers
retrocline lowers
correct overjet

Question 35

what is orthognathic surgery

Answer 35

surgical manipulation of mandible/maxilla to produce optimal dentofacial aesthetics and function

Question 36

when is orthognathic surgery undertaken

Answer 36

when growth is completed

Question 37

what is used to plan orthognathic surgery

Answer 37

prediction planning software

Question 38

what is the process for orthognathic surgery

Answer 38

presurgical orthodontics (18months) - level align and decompensate
orthognathic surgery to reposition jaws
post surgical orthodontics (6months)

Question 39

what is the GDP role in class 3 malocclusions

Answer 39

identify and refer to hospital or specialist practitioner