Class III Malocclusion

Question 1

What is a class III incisor relationship?

Answer 1

This is where lower incisor edge lies ANTERIOR to cingulum plateau of the upper incisors and the OJ is reduced and can be reversed

Question 2

What is the aetiology of class III malocclusion?

Answer 2

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

Question 3

What AP relationship does pt with class III malocclusion often have?

Answer 3

Usually Class III AP relationship (but can also be class I, rare to be class II)

Small maxilla
LArge mandible
Combo

Question 4

What is significant about A/P discrepancy?

Answer 4

The greater the skeletal discrepancy the harder the case is to tx (if more teeth are ib corssbite, worse Ap, skeletal problem)

Question 5

In class III what are indication surgery is likely?

Answer 5

Increased FMPA, AOB, Inc LAFH:TAFH

Question 6

What do pts in class III often have?

Answer 6

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

Question 7

What are the dental features of class III malocclusion?

Answer 7

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

Question 8

What features make class III more difficult to tx?

Answer 8

More than 1/2 teeth in crossbite
Large Ap discrepancy
AOB

Question 9

What can soft tissues usually do in Class III?

Answer 9

NOt usually involved in cause but can result in dentoalveolar compensation - tongue prolines uppers and lower lip retroclines lowers

Question 10

Why do we tx class III malocclusions?

Answer 10

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

Question 11

What are the aesthetic reasons for tx class iii?

Answer 11

Aesthetic reasons - if pt unhappy with profile, psychological effect of this

Question 12

What are dental health reasons for tx class iii?

Answer 12

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

Question 13

What are functional reasons for tx class III?

Answer 13

function - mastication and speech

Question 14

Why is it best to tx class III from young age?

Answer 14

Growth tends to be unfavourable, as pt grows, skeletal discrepancy gets worse, onset of puberty coincides with jaw growth spurt

Question 15

What is ANB of class III pts?

Answer 15

<2

Question 16

What is incisor inclination normally?

Answer 16

110
90

but If dente alveolar comp then >110 and <90

Question 17

What is the tx options for class III?

Answer 17

Accept/Monitor/Do Nothing

Intercept with URA

Growth Modification

Camoflague

Orthognathic + orthodontics

Question 18

Explain the option of accepting class III

Answer 18

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

Question 19

Explain the option of using interceptive orhto for class III

Answer 19

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

Question 20

When using interceptive URA tx what must we be aware of?

Answer 20

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

Question 21

What is growth modification?

Answer 21

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

Question 22

What is traction headgear?

Answer 22

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

Question 23

What is RME?

Answer 23

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

Question 24

What functional appliances can we use for class III?

Answer 24

Reverse twin block - restricts mandible, pt mandible as far back as possible, prolines upper, retroclines lowers

Frankel III - dente-alveolar effect mainly

Question 25

What is ortho camouflage for class III?

Answer 25

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

Question 26

What are favourable features for class III camouflage?

Answer 26

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

Question 27

What teeth do we take out for ortho comoflague of class III?

Answer 27

upper 5

lower 4

Question 28

What is aim of ortho camoflague?

Answer 28

Procline uppers
retrocline lowers
correct OJ

Question 29

What is the orthographic/ortho approach for class III?

Answer 29

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