2. According to British standards Incisor classification, in class III
malocclusion the lower incisor edges lie anterior to the cingulum
plateau of the upper incisors. The overjet is reduced or reversed.
According to Angle’s classification, in class III the mesiobuccal cusp
of the lower first molar occludes mesial to the class I position.
4. Skeletal Pattern
Most important aetiological factor
Skeletal pattern can be any of the
following:
1. Mandibular prognathism
2. Maxillary retrognathism
3. Combination of both
5.
6. Features of class III
malocclusion
A concave facial profile
A retrusive nasomaxillary area
Prominent lower third of the face
Narrow upper arch
Reduced or reversed overjet
8. Diagnosis
A successful treatment plan depends on
an accurate diagnosis
For treating class III malocclusion a
direct cause must be identified, that is,
true class III should be differentiated
from pseudo class III malocclusion.
9. Pseudo Class III
Malocclusion
Pseudo class III malocclusion is a
habitual established cross bite of all
anterior teeth, without any skeletal
discrepancy, resulting from functional
forward positioning/shift of the mandible
on closure.
Causes include:
occlusal prematurity
Enlarged adenoids
10.
11. How to differentiate between a true class
III and pseudo class III malocclusion?
Mandible should be guided in a centric relationship, this will reveal a
normal overjet or edge to edge incisor relation in pseudo class III
On cephalometric analysis, pseudo class III malocclusion shows a
normal SNA if diagnosed early, whereas SNB could be slightly
increased because of forward positioning of the mandible.
In contrast, in true class III cases, a large SNB angle or a small SNA
angle may be found, depending on whether the result is due to an
underdeveloped maxilla or a long mandibular base, or both.
Most true class III cases have a strong hereditary component
12. The final diagnosis of the type of class III malocclusion
relies heavily on:
(i) clinically establishing the dual closure pattern by asking and
guiding the patient to bite in normal centric and habitual positions,
(ii) observing any familial tendency,
(iii) cephalometric parameters
(iv) incisor relationships.
13. Treatment objectives
To achieve growth modulation in skeletal case
To relieve crowding and produce alignment of teeth
To correct incisor relationship to obtain normal overjet and
overbite
To achieve stable molar relationship
14. Factors considered while treatment
planning
Patient’s opinion
Severity of skeletal pattern
Amount and expected pattern of future
growth
Degree of crowding
If an edge to edge incisor contact can be
achieved or not
Amount of dento-alveolar compensation
present
16. Growth Modification
In young patients who are still in their
growing phase orthopedic and myo-
functional appliances can be used in
cases of skeletal class III malocclusion.
Either there is deficient growth of maxilla
or excess growth of mandible.
17. FRANKEL III FUNCTIONAL
APPLIANCE
Used in mild skeletal
problems
Causes downward
and backward
rotation of the
mandible
Has little or no effect
on maxilla
18. Reverse pull headgear
(facemask)
Indicated in patients with retrusive maxilla
Obtains anchorage from forehead and chin
Exerts force on maxilla via elastics that attach to
maxillary splints
Effects include:
1. Forward and downward movement of maxilla
2. Downward and backward rotation of mandible
3. Lingual tipping of lower incisors
19. Treatment given at the
mixed dentition is advocated
by most researchers.
Requires great patient
cooperation.
20. Chin Cup Therapy
An effort to restrain mandibular growth
Redirects mandibular growth in a more vertical direction
Ideal in patients with
mild skeletal problem
reduced lower anterior facial height
normal or proclined lower incisors
Most of the reported studies recommended an orthopedic
force of 300 to 500 g per side
Patients are instructed to wear the appliance 14 hours per
day.
22. Orthodontic Camouflage
Proclination of the upper labial segment
Retroclination of the lower labial
segment
Combination of both
Extraction pattern may vary from
extraction of lower first bicuspids only to
extraction of upper second premolar and
lower first premolar and sometimes even
lower incisor
23. Proclination of upper labial segment
Correction of incisor relationship by proclination of the upper
incisors can only be considered with the following features:
a class I or mild class III skeletal pattern
The upper incisors are not already significantly proclined
Adequate overbite will be present at the end of treatment to
retain the corrected position of the upper incisors
24. Retroclination of lower labial
segment
In cases with mild to moderate class III skeletal pattern
or in case of reduced over bite
Space is required in the lower arch for retroclination of
lower labial segment and extractions are required
25.
26. Orthognathic Surgery
In some cases the severity of skeletal pattern and/or the
presence of a reduced overbite or an anterior open bite
precludes orthodontics alone.
Orthognathic surgery is almost always indicated if:
Value of ANB is -4 Inclination of lower incisors to
mandibular plane is 83
27. Common Surgical
Procedures
Lefort I maxillary advancement
For retrognathic maxilla
bilateral saggital split (BSSO) mandibular
setback
For prognathic mandible
Surgically assisted RPE
30. SUMMARY: Treatment of Class
III Malocclusion
Non-growing patients
1. Acceptance
2. Orthodontic Camouflage
3. Orthognathic Surgery
Growing patients
1. Acceptance
2. Functional orthopedic appliances
3. Orthodontic Camouflage
Notes de l'éditeur
SNA- 82 +- 2SNB 80 +- 2
Splints minimize dental movement and promotes orthopedic movement
Extractions allow orthodontist to reduce the amount of negative overjet and camouflage the skeletal discrepancy
A female patient, 21 year old with concave facial profile complaining for the difficulty of occlusion due to anterior crossbite and openbite. Case Management : Extraction of the poor conditioned mandibular first molars to gain space for anterior segment retraction, placement of lingual arch bar to prevent anchorage loss and class III intermaxillary elastics for dentoalveolar compensation by proclining maxillary incisor and retroclining mandibular incisors (orthodontic camouflage).