Class III Malocclusion Flashcards
What is a class III incisor relationship?
This is where lower incisor edge lies ANTERIOR to cingulum plateau of the upper incisors and the OJ is reduced and can be reversed
What is the aetiology of class III malocclusion?
Skeletal - large mandible, small maxilla, combo of both
Genetic component - often if mum and dad or siblings have class III we see pt with it
As part of a syndrome - pts with CLAP or acromegaly
What AP relationship does pt with class III malocclusion often have?
Usually Class III AP relationship (but can also be class I, rare to be class II)
Small maxilla
LArge mandible
Combo
What is significant about A/P discrepancy?
The greater the skeletal discrepancy the harder the case is to tx (if more teeth are ib corssbite, worse Ap, skeletal problem)
In class III what are indication surgery is likely?
Increased FMPA, AOB, Inc LAFH:TAFH
What do pts in class III often have?
Buccal bilateral corssbite - this is because the mandible is often larger and maxilla often smaller resulting in this crossbite as narrow part of maxilla occludes against wider part of mandible
What are the dental features of class III malocclusion?
Class III incisors
Usually class III molar relationship
AOB in some cases
Usually Class III Skeletal base
Reduced or reverse OJ
Varied OB
Crossbite - buccal bilateral
Crowded maxilla, spaced mandible due to size discrepancy
Often can see dento-akveolar comp - uppers procline, lowers retrocline in attempt to camoflague skeletal discrepancy
tend to displace mandible on closure
What features make class III more difficult to tx?
More than 1/2 teeth in crossbite
Large Ap discrepancy
AOB
What can soft tissues usually do in Class III?
NOt usually involved in cause but can result in dentoalveolar compensation - tongue prolines uppers and lower lip retroclines lowers
Why do we tx class III malocclusions?
Aesthetic reasons - if pt unhappy with profile, psychological effect of this
dental health concerns - traumatic effect of occlusion - upper incisors may be causing gingival stripping of labial mucosa of lower incisors
attrition - when pt displaces mandible
long term TMJ problems due to displacement
function - mastication and speech
What are the aesthetic reasons for tx class iii?
Aesthetic reasons - if pt unhappy with profile, psychological effect of this
What are dental health reasons for tx class iii?
dental health concerns - traumatic effect of occlusion - upper incisors may be causing gingival stripping of labial mucosa of lower incisors
attrition - when pt displaces mandible
long term TMJ problems due to displacement
What are functional reasons for tx class III?
function - mastication and speech
Why is it best to tx class III from young age?
Growth tends to be unfavourable, as pt grows, skeletal discrepancy gets worse, onset of puberty coincides with jaw growth spurt
What is ANB of class III pts?
<2
What is incisor inclination normally?
110
90
but If dente alveolar comp then >110 and <90
What is the tx options for class III?
Accept/Monitor/Do Nothing
Intercept with URA
Growth Modification
Camoflague
Orthognathic + orthodontics
Explain the option of accepting class III
This is done when pt has no concerns and doesn’t want any tx
There are no dental health concerns - ie no traumatic effects such as gingival stripping of libel aspect, no attrition, no displacement
pt is mild class III case
need to warn pt that doing nothing can make tx harder in future
Explain the option of using interceptive orhto for class III
This is where we intercept at an early stage if pt has Class III incisors that can achieve edge to edge occlusion (pt is in anterior crossbite for example)
if we leave it pt will undergo dento-alveoalr compensation whereas if we intercept we can tx the crossbite with URA
When using interceptive URA tx what must we be aware of?
If correcting instancing laterals must be aware of canine root positin
if very high - ok
if lower down then we can’t move laterals as risk of RR
What is growth modification?
This is used on growing pt and can be done to reduce/redirect mandibular growth and encourage maxillary growth
done via:
- headgear
- functional appliances
- TADS
What is traction headgear?
This is when the whole head acts as anchorage in attempt to pull maxilla forward and restrict mandibular growth however compliance must be excellent and needs to be worn 14 hrs a day for effect
evidence that its mainly dente-alveolar compensation but some sekelatl effect
What is RME?
This is where we use appliance to split the palatal suture and attempt to widen the upper arch - maxilla narrow so this helps
12 years
What functional appliances can we use for class III?
Reverse twin block - restricts mandible, pt mandible as far back as possible, prolines upper, retroclines lowers
Frankel III - dente-alveolar effect mainly
What is ortho camouflage for class III?
This is where we accept underlying skeletal discrepancy - usually mild/mod
growth has stopped at this point
we use fixed applianced to get pt to class I incisor and molar relatiobsip
What are favourable features for class III camouflage?
Growth has stopped
ANB>0
Edge to edge able
Mild/mod class III
increased OB
little/no dentoalveolar comp - we have scope to go 120/80
What teeth do we take out for ortho comoflague of class III?
upper 5
lower 4
What is aim of ortho camoflague?
Procline uppers
retrocline lowers
correct OJ
What is the orthographic/ortho approach for class III?
This is where pt has severe skeletal discrepancy
when growth has stopped, function and aesthetic concerns
3 phases:
- pre surgery ortho for 18 motnths - we often make OJ worse
- surgery
- post surgery ortho for 6 months
