Class 3 Malocclusion Flashcards
what is the BSI definition of class 3 malocclusion
lower incisor edge occludes anterior to the cingulum plateau of the upper central incisor and the overjet is reduced or reversed
what is the incidence of class 3 malocclusion in the UK
3-7%
what environmental factors affect class 3 malocclusion
cleft lip and palate
acromegaly
what is the AP skeletal relationship which correlates with class 3 malocclusion
class 3 skeletal base - mandible less than 2-3mm behind maxilla
what needs to be assessed for the vertical skeletal relationship
FMPA
face height proportions
lateral cephalometry
what skeletal features make a class 3 more difficult to treat
greater AP discrepancy
increased FMPA
AOB
what transverse skeletal features are seen
retrusive maxilla sits on the wider part of the mandible causing bilateral crossbites
what are the dental features of class 3
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
what is seen with alignment in class 3
maxilla often crowded
mandible often aligned or spaced
what dentoalveolar compensation occurs in class 3
procline upper incisors
retrocline lower incisors
what is the soft tissue involvement in class 3
tongue proclines upper incisors
lower lip retroclines lower incisors
what are the reasons for treating class 3
aesthetics
dental health
function
what dental health reasons would make you want to treat a class 3
attrition
gingival recession
mandibular displacement
which factors make treating class 3 difficult
greater number of teeth in anterior crossbite
skeletal element in aetiology
greater AP discrepancy
presence of AOB
facial growth
growth status
what is the facial growth like with class 3
mandibular growth continues for a long time and can get worse
how can you predict growth
usually coincides with puberty
use height and weight charts
watch and wait
what are the management options for class 3
accept/monitor
intercept early with URA
growth modification
camouflage
combined orthognathic surgery and orthodontics
when would you accept and monitor a class 3
no concerns
no dental health implications
mild cases
when would interceptive treatment be considered for class 3
if class 3 incisors have developed due to early contact on permanent incisors
correction of anterior crossbite
correcting lateral incisor crossbite
what is used in interceptive treatment for class 3
URA to procline incisors
when is growth modification used
growing patient
what is the aim of growth modification
reducing and redirecting mandibular growth and encourage maxillary growth
what is used for growth modification
chin cup
reverse twin block
frankel III
protraction headgear
what does a chin cup do
lingually tip lower incisors
rotates mandible down and back
