Treatment of class III malocclusions

Question 1

Class III malocclusion aetiology (definition)

Answer 1

The edge of the lower incisor lies anterior to the cingulum plateau of the upper incisor

Question 2

Prognosis for treatment depends on

Answer 2

Skeletal pattern
-dento-alveolar compensation
-can pt achieve edge-to edge incisors?
Amount of overbite
Growth
-can be unfavourable, particularly in boys

Question 3

Class III skeletal pattern - aetiology

Answer 3

1. Mandibular protrusion?
   - 40%
2. Maxillary retrusion?
   - 34%
3. Both
   - 26%

Question 4

Dento-alveolar compensation

Answer 4

Upper incisors proclined
Lower incisors upright or retroclined
-so you can contact on more teeth
-makes treatment harder

Question 5

Overbite in class III

Answer 5

Loss of overbite as tooth preoclined

Must retain tooth at end of treatment???

Question 6

Class III treatment

Answer 6

Normal overbite & reduced overbite –> skeletal pattern (mild, moderate or severe)

Question 7

Normal overbite: mild skeletal III

Answer 7

Can be treated
No lower arch extractions
Do not extract in upper arch if there is no crowding in the lower arch

Question 8

Moderate skeletal III: normal overbite

Answer 8

Needs U and L fixed appliances
Loss of overbite
Poor prognosis for stability
Consider extractions in lower arch

Question 9

Rectangular upper arch wires

Answer 9

Helping us with torque

Round will not introduce torque

Question 10

Severe skeletal III: normal overbite

Answer 10

Pre-surgical orthdontics

Orthognathic surgery

Question 11

Mild skeletal III: reduced overbite

Answer 11

May accept class III incisal relationship and align teeth only

Question 12

Moderate to severe skeletal III: reduced overbite

Answer 12

Poor prognosis for stable treatment

Can align teeth and accept incisor relationship or perform orthognathic surgery when pt is older

Question 13

Timing of treatment for class III malocclusion

Answer 13

Early interception
-growth moedification
Later treatment
-tooth over the bite

Question 14

Skeletal problem treatment

Answer 14

Bring maxilla forwards most of the time

Question 15

Mandible back

Answer 15

Chin-cup
Doesn't really work
-no evidence that mandible affected
-retroclines lower incisors
-possible TMD problems

Question 16

Maxilla forward

Answer 16

Face mask (reverse headgear)
9-11 yo
-worn full-time (20 hours per day) for 4-6 months

Question 17

Both mandible and maxilla movement

Answer 17

Functional appliance
Logic?
-blocks slope in opposite direction
-reverse twin block design
Frankel 3 appliance
-proclines uppers, retroclines lowers

Question 18

Class III problems with functional appliances

Answer 18

Only small amount activation possible
Maxillary retrusion common
Continued growth

Question 19

Interceptive treatment

Answer 19

Incisor over the bite

• central
• laterals

Question 20

Potential problems: check list

Answer 20

Class III skeletal pattern
Overbite
-need enough to retain correction
Space
-extract Cs?
Interference from primary canines
Position of permanent canine?
-prevents movement of lateral incisor
Growth

Question 21

Overbite

Answer 21

Need enough overbite to retain correction

Do not overly procline upper incisors

Question 22

Position of permanent canine

Answer 22

May prevent movement
Resorb lateral if moved
Wait for canine eruption before correction

Question 23

Effect of growth

Answer 23

Complicating factor with class III malocclusions
Mandible may continue to grow throughout teens this worsening class III
Prediction of growth uncertain

Question 24

Extractions in class III cases

Answer 24

Space is gained as upper anterior teeth are moved forward
-requires careful assessment of upper space requirements
No extractions in upper arch if you have not extracted in lower teeth

Question 25

Removable appliances: class III cases
-patient selection

Answer 25

Only select cases with class I or very mild class III skeletal pattern, and normal OB
If pt can achieve edge-to-edge bite on posturing forward, may be suitable (if mild skeletal pattern)
-not always the case as upper teeth may already be proclined and cannot be moved labially any more MOST COMMON SITUATIONS:
Moving incisor over bite
Correcting anterior X-bite of incisors

Question 26

Moving incisor over bite: check list

Answer 26

Often considered simple procedure well suited by GDP but there are several potential pitfalls

• 1. skeletal class III
• 2. sufficient OB to retain correction
• 3. Enough space between Cs to allow forward movement of incisors (if not, XLA Cs)
• 4. Deciduous canine relationship?
• 5. Position of unerupted 3s (when moving 2s over the bite)

Question 27

Moving incisor over bite: skeletal class III?

Answer 27

If this is severe, the upper incisor will be overproclined. Test that the patient can achieve an
edge-to-edge bite without producing a large
vertical space between the posterior teeth

Question 28

Moving incisor over bite: deciduous canine relationship

Answer 28

An abnormal relationship of the deciduous canines may maintain a forward displacement after incisor correction. Grind or extract the deciduous canines in this case

Question 29

Moving incisor over bite: position of unerupted permanent canine? When moving lateral incisors over the bite

Answer 29

Check by palpation and radiographs. If it is close
to the root of the lateral incisor, it may cause
resorption. This is a particular danger in narrow
arches where the canine often develops in a forward position buccal to the lateral. It is better to wait for the eruption of the permanent canine in these case