treatment of class iii malocclusion #orthodontics

DR. SARANG SURESH HOTCHANDANI

Treatment of Class III Problems A class III malocclusion on a skeletal class 1 base with

a significant forward mandibular displacement is

sometimes referred to as a ‘pseudo class III

malocclusion’, because the incisor relationship does

not reflect the underlying skeletal relationship.

Class 3 incisor relationship includes, malocclusion

where lower incisor edge occludes anterior to

cingulum plateau of upper incisors.

Etiology of Class III Malocclusion Skeletal Class III is most common cause with resulting

following features

o Increased mandibular length

o Forward positioning of glenoid fossa

o Reduced maxillary length

o Short cranial base

o Reduced cranial base angle

Skeletal class III often have increased vertical

dimension.

They are also associated with unilateral or bilateral

cross bite, which is due to following reasons;

o Narrow maxilla

o Broad mandible

o Antero posterior skeletal discrepancy

o Vertical maxillary deficiency

o Transverse deficiency

Other Rare Causes include;

o Cleft Palate


o Craniofacial syndromes

Crouzon syndrome

Sometimes patients have large tongue which can

broad the lower arch resulting increase in cross bites &

Proclination of lower incisors worsening the class III.

OCCLUSAL FEATURES of SKELETAL Class III Anterior cross bite

Buccal cross bite

Maxillary arch crowding (common)

With favourable soft tissues environment, this skeletal class III exhibit dento alveolar compensation in which soft tissues cause tilting of upper & lower incisors towards each other, so that the incisor relationship is less severe than underlying skeletal

class III.

Factors to be Considered during Treatment of Skeletal Class III patient

Patient Concerns Dental problem alone can be managed with orthodontic treatment alone.

Facial/functional problems will require orthognathic surgery.

Motivation for treatment

o Good dental health and motivation are required for complex treatment.

Severity of skeletal discrepancy

o A mild/moderate skeletal discrepancy may be treated with orthodontic camouflage if the patient can achieve edge to edge occlusion.

o A severe skeletal discrepancy can be treated comprehensively with orthodontics & orthognathic surgery.

Remaining growth o If correction is done before end of pubertal growth, it will relapse due to differential growth of mandible. That’s why it should be continued after the stoppage of pubertal growth.

Degree of dento alveolar compensation

o In preexisting dento alveolar compensation we cannot perform camouflage

Ability to achieve edge to edge

o An ability to achieve edge-to-edge favors orthodontic camouflage as it indicates that less incisor movement is required for correction than suggested by the size of reverse overjet in centric occlusion

Depth of overbite o A deep overbite offers scope for camouflage by downwards and backwards rotation of the mandible (e.g. facemask) and improves stability of anterior cross bite correction.

Figure 1 Dento Alveolar Compensation


Anteroposterior & Vertical Maxillary Deficiency Effect of antero posterior deficiency in contribution to skeletal class III is direct on mandible

While, effect of vertical deficiency in class III is indirect on mandible

o Cause rotation of mandible upward & forward, produce appearance of mandibular prognathism.

Methods to treat both these maxillary deficiencies; Frankel’s FR – III Functional appliance

Reverse pull headgear (facemask)

Class III elastics.

FR – III Functional Appliance Should be only used in extremely mild conditions.

Theoretically this appliance; stretches the soft tissue at the base of upper lip via lips pads, attempting to stimulate

forward growth of the maxilla by stretching the maxillary periosteum while

maintaining the mandible in its most posterior or retruded position.

However, following changes occur for correction of skeletal class III with

this appliance.

o Eruption of maxillary molars mesially

Blocking the eruption of lower molars vertically & antero

posteriorly.

o Facial tipping of maxillary anterior teeth & retraction of

mandibular anterior teeth.

o Rotation of occlusal (shown in pic)

due to more eruption of upper molars than lower molars.

o Downward & backward rotation of mandible.

Decreasing the chin prominence

Increase facial height

This appliance has long treatment & retention periods that require excellent compliance.

Reverse – Pull Headgear (Facemask) Face mask or the reverse-pull headgear is an extra oral traction appliance used for correction of skeletal class III

malocclusion.

It was popularized by Delaire in the 1960s.

Indications;

o CLASS III

Figure 2 FR - III


Facemask moves maxilla forward by inducing growth at the maxillary sutures.

A. This Delaire-type facemask offers good stability when used for maxillary

protraction. It is rather bulky and can cause problems with sleeping and wearing

eyeglasses. With even modest facial asymmetry, it can appear to be ill-fitted on

the face. Note the downward and forward direction of the pull of the elastics.

B. This rail-style facemask provides more comfort during sleeping and is less

difficult to adjust. It also can be adjusted to accommodate some vertical

mandibular movement. Both types can lead to skin irritation caused by the plastic

forehead and chin pads. These occasionally require relining with an adhesive-

backed fabric lining for an ideal fit or to reduce soft tissue irritation. Clinical experience indicates that some children will prefer one type

over the other, and changing to the other type of facemask can improve cooperation if the child complains.

Protraction of maxilla should be performed at the early age, because age of patient is critical variable in forward

movement of maxilla with orthodontic appliance.

True skeletal change decline beyond age 8, while, the chances of clinical success begins to decline at age 10 – 11.

Facemask treatment is most suited for children with minor – moderate skeletal

problems. This device is to be used in children who have true maxillary problems in Class

III.

Defer facemask treatment until permanent 1st molar & incisors have erupted.

o Molar give anchorage

o Incisors will provide inclination for correction of overjet.

Facemask is attached intra orally with maxillary removable splint or with banded expander.

o These both appliances contain hooks in premolar – canine region for attachment of elastics as shown in

figure above.

Facemask provide 350 – 450 grams of force per side when worn for 12 – 14 hours per day.

Elastic are placed in a slight downward direction b/w intra oral attachment and facemask to correct vertical

maxillary deficiency along with antero posterior deficiency.

A maxillary removable splint is sometimes used to make the

upper arch a single unit for maxillary protraction.

A. The splint incorporates hooks in the canine-premolar

region for attachment of elastics and should cover the

anterior and posterior teeth and occlusal surfaces for

best retention.

B. Note that the hooks extend gingivally, so that the line

of force comes closer to the center of resistance of the

maxilla. Multiple clasps also aid in retention. If

Figure 3 A. Delaire-type facemask B. rail-style facemask


necessary, the splint can be bonded in place, but this causes hygiene problems and should be avoided if possible

for long-term use.

C. and D, a banded expander or wire splint also can be used for delivery of protraction force. It consists of bands on

primary and permanent molars or just permanent molars connected by a palatal wire for expansion and hooks on

the facial for facemask attachments.

If the maxilla is narrow, palatal expansion is anticipated, then expansion device will act as splint for the attachment of

facemask

EFFECTS of FACEMASK Clockwise rotation of mandible – downward & backward rotation.

o increase lower facial height (long face).

o That’s why facemask is contraindicated in long face patients.

Downward rotation of posterior maxilla and anterior open bite (see diagram below)

Forward movement of maxilla and Proclination of maxillary teeth.

Correction of cross bite— both posterior as well as anterior.

With the splint over the maxillary teeth and forward pull from the facemask, the hooks on the splint should be elevated. Even so, the line of force is likely to be below the center of resistance of the maxilla, so some downward rotation of the posterior maxilla and opening of the bite anteriorly is anticipated

Skeletal Anchorage With the appliances mentioned above for maxillary protraction, there is a major side effect

as mentioned; although we want to cause maxillary protraction but there is more dental

protraction than maxilla.

So, before advent of bone screws or miniplates, primary canines were deliberately

ankylosed so that they can act as “natural implants” to which facemask or Class III elastics

can be attached & support can be taken be taken from these teeth for Proclining the

maxilla in class III patients without changes occurring in teeth.

if a child with maxillary retrusion has spontaneous ankyloses of primary molars, the splint of facemask can be attached

to that tooth for above mentioned biomechanical advantage.

This dental change can be prevented & maxillary Proclination can be magnified in one of two ways in which face mask

is attached with;

01) Miniplates at the base of zygomatic arch or in anterior maxilla.

02) Bone anchors/screws above the incisors

For patients approaching adolescence i.e., about age 11 and old are better treated with bone screws for attachment of

facemask for Proclining the maxilla.

Another method of correcting the Class III problems is placement of bone supported miniplates bilaterally in maxilla

and mandible, to which class III elastics are attached.


A maxillary-deficient child wearing Class III elastics to miniplates at the base of the zygomatic arch and mesial to the mandibular canines. Note that the patient is wearing a biteplate to open the bite until the anterior cross bite is corrected, and that and that point of attachment for the lower left miniplates has been repositioned with a piece of 21 × 25 steel wire in the miniplates tube. Being able to move the point to which force is applied, of course, is one of the advantages of miniplates.

Advantages of these Skeletal Anchorage & Class III Elastics over the Extra Oral Appliances mentioned above; o Produce more skeletal change than dental change.

o Wearing extra oral appliances is not necessary.

o Full time application of force can be obtained.

Disadvantage is surgical placement & removal of miniplates or bone screws.

The minimum age for placement of placement of these bone screws is approx. 12 years

of age. Placement before this age weakens the bone because of low density of alveolar

bone at that age, and effect the eruption of permanent teeth placed under the bone.

There is relapse of class III treatment, remember it is because of excessive mandibular

growth.

Class III due to Mandibular EXCESS They are difficult to treat because we cannot determine when the mandibular growth will stop.

Class III Functional Appliances in Tx. Of Excess, Mandibular Growth Functional appliances for patients with excessive growth does not restrain mandible growth but instead they cause

following effects;

o Rotate mandible downward & backward

o Guide the eruption of teeth (Camouflage)

Upper posterior teeth erupt downward & forward

Eruption of lower posterior teeth is restricted.

Lingual tipping of lower incisors.

Facial tipping of upper incisors.

Functional appliances used in mandibular excess are like those which are used in maxillary deficiency mentioned

above, except that they don’t contain lip bumper.

Class III Functional AppliancesClass III Functional Appliances

Chin Cup with High Pull HeadgearChin Cup with High Pull Headgear

Class III elastics to Skeletal AnchorsClass III elastics to Skeletal Anchors


Chin Cup Appliance Chin cap or chin cup is an extra oral orthopedic device, which exerts upward and backward force on mandible by

applying pressure to chin and thereby preventing its forward growth.

Chin Cup therapy changes the direction of mandibular growth by rotating the chin

downward & backward, making the chin less prominent by increasing anterior facial

height.

Chin cup temporarily restrict the growth which will be overwhelmed by subsequent growth.

o Means thore time lae gowth khe stop karayeendo aa ta jeeyan future me growth the ta ooha excessive growth nazar na ache aen thori der

lae jeka growth stop karaeendas chin cup san ooha future je growth me dhakji wendi.

In real meaning, chin cup causes following changes;

o Decrease the anteroposterior prominence of chin

o Increase the facial height.

o Lingual tipping of lower incisors due to pressure of the appliance on lower lip.

This effect is undesirable.

There are 2 Types of Chin Cup;

o Occipital pull chin cup

o Vertical pull chin cup

Occipital pull chin cup

o Most commonly used type and derives anchorage from occipital region of head.

o Used in cases of class III malocclusion with mild-to-moderate prognathism.

Vertical pull chin cup

o It is used to correct anterior open bite cases.

o Force magnitude and duration of wear (biomechanics)

o Force at the start of treatment: 150–300 g/side.

o After 2 months, force is increased to: 450–700 g/side.

o Duration to wear appliance to achieve desired results: 14 hours a day with a range of 10–16 hours.

Class III Elastics to Skeletal Anchors class III elastics as mentioned in above topic of skeletal anchorage cause protraction of maxilla, but it was seen that

some effects of mandible also occur during elastics treatment as mentioned below.

Posterior displacement of mandible at the condyle & posterior ramus.

For a child with sever prognathism orthognathic surgery at the end of growth period is

the best treatment.

THE END

treatment of class iii malocclusion #orthodontics

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