In the name of GOD

Treatment of skeletal class III

in preadolescent children

Presented by:

Dr Somayeh Heidari

Orthodontist

Reference:

Contemporary Orthodontics

Chapter 13

William R. Proffit, Henry W. Fields, David M.Sarver. 2013. Mosby

Class III profile

SNA :

SNB :

ANB

Wit’s :

Dental compensation

U1 to SN :

IMPA :

Anteroposterior and vertical maxillary deficiency

The maxilla is small or positioned posteriorly Direct effect

The maxilla does not growth vertically Indirect effect

Possible approaches to maxillary deficiency:

Frankel’s FR-III functional appliance

Reverse- pull headgear (facemask) to a maxillary splint or skeletal anchors

Class III elastics to skeletal anchors

FR-III Functional Appliance

FR-III is made with the mandible positioned posteriorly and rotated open

with pads to stretch the upper lip forward

in theory, the lip pads stretch the periosteum

stimulates forward growth of the maxilla

Levin et al:

significantly enhanced change in maxillary size and position

improved mandibular position

more lingual lower incisor bodily position

more overjet

Most other studies:

little true forward movement of upper jaw

most of the improvement is from dental changes

the appliance allows the maxillary molars to erupt and move mesially

holding the lower molars in place vertically and anteroposteriorly

tips the maxillary anterior teeth facially

retracts the mandibular anterior teeth

rotation of the occlusal plane

rotates the chin down and back

Class III will improve because of the mandibular rotation , not an effect on the maxilla

Functional appliance treatment:

little or no effect on maxillary deficiency

Should be used only on extremely mild cases

Long treatment and retention periods that require excellent compliance

Reverse – Pull Headgear (Facemask)

Delaire:

a facemask attached to a maxillary splint could move the maxilla forward

inducing growth at the maxillary sutures

only if it was done at an early age

The age of the patient is a critical variable.

it is easier and more effective to move the maxilla forward at younger age

the chance of true skeletal change appears to decline beyond age 8

the chance of clinical success begins to decline at age 10 to 11

the force is applied to the teeth for transmission to the sutures

facemask treatment is most suited for children with mild to moderate skeletal

problems

the treatment is best used in children who have

true maxillary problems

the effects on mandibular growth caused by clockwise rotation of the mandible

It is better to defer maxillary protraction

until the permanent first molars and incisors have erupted.

the molars can be included in the anchorage

the inclination of the incisors can be controlled to affect the overjet

simultaneous palatal expansion makes no difference in the amount of

anteroposterior skeletal changes

if the maxilla is narrow, palatal expansion is quite compatible with maxillary

protraction

there is no reason to expand the maxilla just to improve the protraction

the appliance must have hooks for attachment to the facemask

the hooks are located in the canine – primary molar area above the occlusal plane

in this place the force vector is nearer to the center of resistance of the maxilla

this limits maxillary rotation

*

a facemask is as acceptable as conventional headgear

there are a variety of designs

approximately 350 to 450 gm of force per side

for 12 to 14 hours per day

most children with maxillary deficiency are deficient vertically

in these cases, a slight downward direction of elastic tractions often is desirable

some downward – backward mandibular rotation improves the jaw relationship

a downward pull would be contraindicated if lower face was already large

backward displacement of mandibular teeth and forward displacement of the

maxillary teeth typically occur

closer to adolescence, mandibular rotation and displacement of maxillary teeth

- not forward movement of the maxilla – are the major components of the

treatment

Application of skeletal anchorage

a major negative side effect of maxillary protraction is maxillary dental movement

ankylosed primary canines could be used as “natural implants”

3 mm of maxillary protraction in 1 year

with minimal dental changes (Shapiro and Kokich)

ankylosed primary molars have the same biomechanical advantage

For more routine use in clinical practice:

the facemask can be applied to miniplates at the base of the zygomatic arch

or in the anterior maxilla

anchors above the incisors

400 gm of force per side

16 hours per day

0.45 mm per month of anterior maxillary movement

without rotation of the maxilla

for patients approaching adolescence

bone supported miniplates can be placed bilaterally in the maxilla and the mandible

with interarch force from class III elastic

the force delivered to the jaws rather than the teeth

forward movement of the maxilla at a higher level

displacement or remodeling in the temporomandibular fossae

full-time elastics delivering approximately 150 gm per side

more than 2 mm maxillary protraction in 56% of the patients

This approach has two advantages:

it is clearly more effective than a facemask to a maxillary splint and also appears

to produce more skeletal change than has been reported with facemask to anterior

miniplates

wearing an extraoral appliance is not necessary and nearly full-time application

of the force can be obtained

The disadvantage is:

Requiring surgical application and removal of the miniplates

Alveolar bone screws with class III elastics:

simpler to place and remove than miniplates

But the lower density of the bone in preadolescents and avoiding damage to

unerupted permanent teeth pose substantial problems with their use.

Miniplates attached to basal bone can be used at age 10.6 or 11.

The minimum age for alveolar bone screws for this application appears to

be approximately age 12, probably too late for an optimal skeletal effect.

There is no doubt that maxillary protraction at an early age usually produces clinical

improvement in a class III patient.

The extent of long-term maintenance

The chance of need to orthognathic surgery

recall 8 to 10 years after the initial treatment

25% to 30% of the facemask patients ended up in anterior cross bite after adolescent

growth , that the majority of these would require surgery for correction

would the long-term outcomes be better if facemask or class III elastics

were attached to skeletal anchors?

The more a child’s class III problem is due to maxillary deficiency,

the more likely it is that long-term success will be achieved with

maxillary protraction.

The more the problem is mandibular prognathism, the more likely

that the problem will recur with adolescent growth.

Thanks for your attention