Class 3 malocclusion

What is the definition of a class 3 skeletal, incisal and molar relationship

What is the skeletal relationship and what is a and b showing?

• Bimanual palpation in maximum concavity in maxilla a and part part of mandible b

• in skeletal 3 b is ant to a or at the same point

What is a class 3 incisal relationship?

• The lower incisal edges meet anterior to the cingulum plateau of the palatal surface of the upper incisors

• Clinically: reduced overjet and overbite

• Reverse overjet

What is a class 3 molar relationship?

• The mesio-buccal cusp of the upper first molar lies distal to the mesio-buccal groove of the lower molar

Aetiology of class 3? (4)

• Skeletal

• Soft tissue

• Dentoalveolar

• other

Skeletal a-p?

• Maxillary retrusion - hypoplasia

• Mandibular protrusion - prognathism

• Combination of both usually

• AP - discrepancies can also be in the vertical and transverse as well

Soft tissue?

• Do not play a major part in aetiology of class 3

• play a role in the compensation of the dentition to mask the magnitude of the underlying skeletal pattern

Dentoalveolar? (3)

e.g hypodontia where there is a reduced upper arch length

• Fewer teeth in the maxillary arch

• Narrow upper arch and broad lower arch

• pseudo class 3 posturing forwards for a comfortable bite

Other factors? (2)

• Genetics

• Craniofacial anomalies - cleft lip and palate, binders syndrome

• Habits do not play a role

Diagnosis: History, what might be included?

What comes after history taking/

0 Extra-oral - hard and soft tissues

Intra oral examination

Extra-oral assessment?

hard tissues what 3 dimensions are you assessing about the skeletal pattern?

• AP

• Vertical

• Transverse dimension

A-P assessment of the skeletal relationship?

A and B - bimanual palpation

Vertical assessment is carried out how (lateral view)?

Frankfort and mandibular angle

FMPA

Another vertical assessment in the frontal view? (2)

• Facial third and increased scleral show - which is increased with hypoplastic maxilla

Hard tissue - transverse assessment??

Assess symmetry of the patient in supine position

Intra-oral, what is included in intra (2) and inter (7)?

• Intra - crowding and spacing

• Inter-

• incisal, molar relationship

• overjet, overbite, centrelines

• cross bites, displacement

Often cross bites ant and post - displacement or underlying skeletal discrepency

What is seen in this image>?

class three and cross bite on the upper right central incisor

both have incisal edges lying anterior to the cingulum plateau of the central incisors

• looks similar to C2D2 variant

• Class 3 with reverse overjet

What rx are usually carried out for diagnosis?

• OPG

• Lat Ceph

• Occasionally an USO

What are indications for tx? (4)

• Cross bites and associated displacements (causing dental trauma)

• Pt reported functional problems

• Aesthetics

• Expected pattern of growth

Assessment of cases? (5)

• Age - growing - intervening early if there is more growth potential

• Patient concerns - facial (camouflage will not address) or dental

• Difficult in tx - crowding (camouflage requires space to correct ant occlusion, severe crowding there is not enough space to retract lower dentiton)

• Amount of dento-alveolar compensation (potential for further compensation with camouflage limited as camouflage is compensation in itself)

• Stability of OB/OJ correction

further compensation with camouflage may not camouflage requires space in the ant

Tx opinions?

• Accept - do nothing and wait

• Interceptive - URA, functional, head gear

• Camouflage

• Comprehensive orthognathic

Growing - wait until growth ceases

functional concerns or attempting growth compensation - interceptive tx using URA or functional appliance

mild no facial concernes, non growing - camouflage

none growing and mod to severe where camouflage is not sufficient, ortho surgery indnicated

3 timings in age (Dental/chronological) based approach?

• Early - early mixed dentition - pre 10

• Intermediate - adult dentition - still growing 10-16

• Late - Non - growing patient - 16+

When to treat early?

If there is significant risk if no intervention carried out?

Example of case for early interceptive

Traumatic cross bite

soreness of soft tissue

tooth wear

What is this image showing?

what are concerns with dispacement?

Same patient in undisplaced position

TMJ problems and mandibular asymmetry

What is the likely prognosis?

• Good as the overbite will act as retention

What is this?

Early interceptive tx for this patient was carried out using an upper removable appliance

Final results:

Ideally 6 months as compliance can fall after this

Intermediate what 2 treatment categories?

why is case selection important?

• Growth modification and camouflage

• Growth prediction would be ideal

• growth potential - 8-10 growth modification - but outcomes can become undone as pt grows

• if presenting beyond age, camouflage can be used

When does the maxilla stop growing in females and males?

19 - males

15-17 females

What does the case assessment involve?

Growth modification

required what from the patient?

is tx outcomes guaranteed?

Growth modification needs to be continued throughout what?

• cooperation and understanding

• outcome of tx not guaranteed

• needs to be continued throughout growth of maxilla

Whilst the maxilla is still growing, growth can be modified with? (2)

• Functional

• Reverse head gears - attached to appliance in mouth, rmed or URA or forwards downwards directions mimicking normal displacement of the maxilla to advance its a-p position and improve ant occlusion

This mode of tx - growth modification - is only for what?

• Mild and moderate cases

• If severe, tx at this stage is not beneficial to the patient

Dental camouflage

suitable for what cases? (4)

• Mild-mod skeletal 3 pattern

• patient happy with facial profile

• potential for proclining upper teeth and retroclining lower teeth

• good overbite

• dentition is not already being heavily compensated

• 
  

How is camouflage carried out?

what teeth are xla if xla approach?

• Upper and lower fixed appliances

• non-XLA procline uppers and retrocline lower

• or fixed appliances and extraction - to create sufficient space

• Upper 5’s and lower 4’s

What may be required to correct cross bites?

Upper arch expansion

(transverse discrepancies)

Image - born with cleft palate and wearing tri helix appliance

degree of discrepancies of a young person might mean telling them to wait until growth cessation for ortho surgery

what appraoch would you take?

camouflage

sometimes this may not be enough to correct

If facial profile is a concern?

can you start camouflage and then go for surgery?

• decompensate the dentition in pre surgical preparation - wil make a reverse overjet worse before being corrected with surgery

• camouflage is compensating