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
what is Frankel III
appliance which holds lip away, proclines upper incisors with palatal arch and retroclines lower incisors with labial bow
what is a reverse twin block
a twin block which is cut at a different angle than a class block
when does a reverse twin block work
in mild class 3
patients who can achieve edge to edge already
how is protraction headgear used
14hrs per day
400g force on each side of face
in patients 8-10yrs old
what result can protraction headgear achieve
rapid maxillary expansion
where are bollard implants placed
infrazygomatic crest and lower canine region
what is orthodontic camouflage
accept the skeletal base and aim for class 1 incisor relationship
what features are favourable when opting for camouflage
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
what is the extraction pattern for camouflage
upper 5s and lower 4s
what is the aim of orthodontic camouflage
procline uppers
retrocline lowers
correct overjet
what is orthognathic surgery
surgical manipulation of mandible/maxilla to produce optimal dentofacial aesthetics and function
when is orthognathic surgery undertaken
when growth is completed
what is used to plan orthognathic surgery
prediction planning software
what is the process for orthognathic surgery
presurgical orthodontics (18months) - level align and decompensate
orthognathic surgery to reposition jaws
post surgical orthodontics (6months)
what is the GDP role in class 3 malocclusions
identify and refer to hospital or specialist practitioner
