Non surgical management of Class 3 malooclusion /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
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INTRODUCTION
ETIOLOGY
SYMPTOMS OF CLASS III MALOCCLUSION
FUNCTIONAL AND CEPHALOMETRIC
ANALYSIS
CEPHALOMETRIC CLASSIFICATION OF
MALOCCLUSION
TIMING OF CLASS III MALOCCLUSION
TREATMENT OF TYPE A CLASS III
TREATMENT OF TYPE B CLASS III
TREATMENT OF TYPE A AND B CLASS III
BIOMECHANICS AND GENERAL ASPECTS OF
PERMANENT DENTITION TREATMENT
RETENTION OF CLASS III

The true genetic Class III growth pattern is the opposite of
the most common orthodontic problem which is retrusion
of the lower jaw. In the Class III the lower jaw is
protrusive and it may be mistakenly referred to as an
"under bite". In reality, the lower jaw is too long relative
to the rest of the face, and the chin appears to protrude
too far in front of the rest of the face. The true Class III is
a genetically directed problem which may express itself
at an early age, but usually becomes more apparent as the
child approaches the teenage growth spurt. Generally, we
will find a parent or grandparent with the exact same
problem on one side of the family.

The true Class III is not an all or none problem.
There are varying degrees in the amount of
abnormal growth which can occur in the lower
jaw. Once the lower teeth move out in front of the
upper incisors, the muscles influence their
position and the size of the chin comes into play
to determine how "bad" the condition looks.

According to ANGLE class III malocclusion is
defined as class III molar relation with the mesio
– buccal cusp of the maxillary first permanent
molar occluding in the inter dental space
between the mandibular first and second
molars. Or lower permanent molar is ahead of
the upper first molar by a distance of the width
of a premolar or half the width of a molar.


Although it is difficult to know the precise
cause of most malocclusions, we do know in general
what the possibilities are, and these must be considered
during treatment.
1.TERATOGENS:
Cleft lip and palate result in maxillary deficiency in
most occasions a class III malocclusion is established.
Teratogens causing cleft lip and palate are aspirin,
cigarette smoke (hypoxia), Dilantin, 6Mercaptopurine, valium etc Vitamin D excess
causes premature closure of sutures and might lead to
class III malocclusion.

2. ACROMEGALY AND HEMI MANDIBULAR
HYPERTROPHY:
Acromegaly is caused by anterior pituitary
tumour that secretes excessive amount of growth
harmone. Here excessive mandibular growth occurs
creating a skeletal class III malocclusion. Often the
mandibular growth accelerates to levels seen in the adult
growth spurt, years after the adolescent growth spurt is
completed. The reason for hemimandibular hypertrophy
is unknown. Formerly called condylar hypoplasia it is
know called a hemi mandibular hypertrophy as a body of
mandible is affected. This condition leads to a class III
with asymmetry

3. GENETIC INFLUENCES:
Best known examples of genetic influences are the classic
HAPSBURG JAW and the prognathic mandible of
Austrian royal family. The influence of inherited
tendencies is strong for mandibular prognathism in
particular (most inherited condition followed by long
face pattern which is second.
Litton et al (ajo 1970) concluded that one third of a
group of children who presented with a severe class III
malocclusion had a parent with the same problem and
one sixth had an affected sibling.


4.ENVIRONMENTAL INFLUENCES:
Large tongue as in the case of thyroid deficiency can
contribute to a mandibular prognathism by causing the
mandible to be positioned forward all times.
Rakosi and Schilli suggested mouth breathing in
the etiology of class III malocclusions. They
hypothesized that excessive mandibular growth could
arise as a result of abnormal mandibular posture
because constant distraction of the mandibular condyle
from the fossa may be a growth stimulus.


5.The posterior ‘squeezing out’ effect of molar
crowding
There has been discussion of posterior crowding as a
factor in the development of Class III malocclusions.
The theory suggests that a squeezing out effect can
occur because of crowding in the molar regions,
which can contribute to an anterior open-bite
malocclusion in a mandible with poor vertical growth
in the ramus area . Alternatively, good ramus growth
can lead to a Class III malocclusion. This concept is
not well understood, and has not been fully
investigated

The incidence of skeletal Class III malocclusion in the
white population is approximately 5%. The mid face
deficiency is high in Asian population which increases
the frequency of malocclusion. The incidence of this
malocclusion ranges between 4%and 13% among the
Japanese and 4% and 12% among the Chinese. A lesser
incidence of class III malocclusion is seen among
African- Americans. The incidence has been reported
to be significantly higher in the Scandinavian and
Japanese populations.


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Early signs of true progressive mandibular prognathism
occasionally can occur in infancy. In the first months
of life a sequential development of the class III
condition may be observed as:
Eruption of the maxillary central incisors in a lingual
relationship and the mandibular incisors in a forward
position with no overjet.
Development of an incisal crossbite during the eruption
of the lateral incisors into a normal relationship.

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Full incisor cross bites some weeks later.
Flattening of the tongue as it drops away from the
palatal contact and postures forward, pressing against
the lower incisors
Habitual protraction of the mandible by the child into
the protruded functional and morphologic relationship

The configuration and form of the forehead and nose in
relation to the lower face are significant for esthetic
evaluation and prognosis. A well formed Naso labial angle
is important for esthetic improvement. If the angle is acute,
the premaxilla segment can be retracted if the angle is
obtuse; the segment must be protracted to improve facial
esthetics. The soft tissue of the chin can compensate for or
accentuate a skeletal class III relationship depending on its
thickness. Gingival retraction or dehiscence can often be
seen in early class III malocclusion. This damage is
irreversible and is an indication for early treatment


The next step is examination of the dentition,
including the morphology and number of teeth.
Congenital absence in the maxilla (e.g., missing
canine or first premolar teeth) makes treatment more
difficult.
When evaluating tile axial inclination of the
teeth, certain disadvantageous irregularities such as
labial tipping of the upper incisors and lingual
tipping of the lower incisors still in anterior cross
bite should be noted. A concavity of the lingual
alveolar structure in the mandible also is a clue to
future difficulties in the correction of Class III
malocclusion.


Crowding of maxillary teeth also enhances
treatment problems; treatment may require
extraction of the counterpart teeth in the lower
arch, leading to great difficulty in closing spaces
and maintaining proper incisor axial inclination.
To make treatment easier if extractions are
required, the clinician should perform extractions
in the mandible before proceeding to those in the
maxilla. Depending on the state of development,
enucleation or germectomy may be feasible for the
lower first premolars. The molar occlusal
relationship is usually Class III, but the plane of
occlusion also should be evaluated because its
correction may be necessary before surgery

The path of closure is from the postural rest position to
occlusion must be carefully studied. The mandible may
slide anteriorly into a forced protrusion because of
premature contact and tooth guidance when the jaw closes
into full occlusion. Such anterior displacements have more
favorable prognosis. In contrast, patients with problems
caused by an anterior rest position with respect to habitual
occlusion are difficult to treat and usually require
orthognathic surgery.


In addition to this pseudo-forced bite category also
exists. This is a skeletal class III with a dental
compensation arising from labial tipping of the upper
incisors on a deficient maxillary base and lingual
tipping of the lower incisors on an excessively long
mandible. Orthodontic pre surgical treatment must
decompensate these malpositions before surgical
procedures can be performed.


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If the condyle occupies the most posterior position
in the temporal fossa the likelihood of its riding over
the posterior periphery of the articular disk is
increased with concomitant clicking and lateral
crepitus,.
Abnormal tongue function, size and posture must be
considered. The tongue may be postured low in the
mouth and be flat and elongated, especially in cases
of mouth breathing. In cases of Macroglossia the
tongue is not contained within the dentition and the
scalloping effect of the tooth contact may be visible
on the periphery.

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A short hypotonic retrusive upper lip is often seen in
combination with a heavy, redundant, everted lower
lip.
A closed lip position will produce the appearance of a
long lower lip, as the lip elongates to close over the
class III incisor relationship. The closed lip length is
misleading and should not be used for treatment
planning. Relaxed lip appearance is deceiving due to
hypotonicity of lower lip --- this causes elevation and
apparent lengthening.
The lower lip length should be verified with the lower
incisor tip to soft tissue menton which is not
influenced by posture

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Maxillary retrusion is associated with upper lip
retrusion and a straight maxillary sulcus curve.
Upper lip retrusion is treated with labial crown
torque.


1.
2.
3.
4.
5.
6.

An increased gonial angle
Antegonial notching
Backward direction of condylar growth
Thin mandibular symphysis
Compensation in position of upper and lower
incisors in response to disproportionate jaw growth.
Mandibular incisors are retroclined as child
becomes older there roots tend to press against the
labial plate producing a WASH BOARD EFFECT.
Maxillary incisors are usually flared anteriorly.


Several studies have expanded on these findings in an attempt to
compare Class III malocclusion with Class I controls relative to
the morphology of the maxilla, the mandible, and the cranial base.
These differences include the following:

1. The SNA angle is significantly lower in the Class III
samples, indicating a greater degree of maxillary
retrusion.
2. Mandibular protrusion is greater in the Class III samples.
3. The mean ANB angle in the Class III samples is negative.

4. The gonial angle is more obtuse in the Class III samples.
5. The mandibular plane angle is steeper than normal in the
Class III samples.
6. Lower anterior face height is significantly greater in the
Class III samples.
7. The sella angle and articular angle were smaller in class
III samples.
8. Anterior position of the mandible is seen.


CLASS III MALOCCLUSION CAUSED BY A
DENTO ALVEOLAR MALRELATIONSHIP
 No basal sagittal discrepancy is apparent
 The sub spinale -nasion-supra mentale (ANB angle)
is within normal limits.
 Maxillary incisors tipped lingually and mandibular
incisors tipped labially


CLASS III MALOCCLUSION WITH A STRONG
MANDIBULAR BASE
1.
Mandibular base and ascending ramus are large
2.
SNA angle is normal
3.
SNB angle is larger than normal.
4.
ANB angle is negative
5.
Gonial angle is usually large
6.
Articular angle is usually small.
7.
Anteriorly positioned mandible
8.
The tongue is postured forward and lies low in the mouth
9.
The upper incisors are tipped labially
10.
The lower incisors are inclined lingually
11.
Lateral cross bites are often evident
12.
Maxillary arch appears to be narrowed.

CLASS III MALOCCLUSION WITH AN UNDER
DEVELOPED MAXILLA
1.
Maxillary base is small and retrognathic
2.
Smaller SNA angle
3.
Normal SNB angle
4.
Mid face deficiency and some cases of associated cleft
palates are seen


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CLASS III MALOCCLUSION WITH A COMBINED
UNDERDEVELOPED MAXILLA AND A PROMINENT
MANDIBLE
SNA angle is small and maxillary base is short
SNB angle is large and the mandibular base is large

In a patient with short ramus:
1. Growth pattern is vertical and the gonial angle is large.
2. Often open bite is seen
3. Crowding in the upper arch

In a patient with long ramus:
1. Growth pattern is horizontal and gonial angle is small
2. Reversed over bite is apparent


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CLASS III MALOCCLUSION WITH A PSEUDO
FORCED BITE OR ANTERIOR DISPLACEMENT
The condition known as class III skeletal dysplasia is
partially compensated by the labial tipping of the upper
incisors and the lingual inclination of the lower incisors
This tooth mal position results in additional anterior
guidance of the mandible on the path from postural rest
to the habitual occlusion as the lingual aspect of the
lower incisors rides on the maxillary incisor margins
after initial contact


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Moyer’s suggested pseudo–Class III malocclusion as a
positional mal relationship with an acquired neuro-muscular
reflex. Pseudo–Class III malocclusion has been identified
with anterior crossbite as a result of mandibular
displacement.
Premature contact between the maxillary and mandibular
incisors results in forward displacement of the mandible in
pseudo Class III malocclusion so as to disengage the incisors
and permit further closure into the position in which the
posterior teeth occluded. Several reports attributed the
incisor interference to the retroclined upper incisors and
proclined lower incisors in pseudo–Class III malocclusion.
Based on clinical assessment, Turley and Lin reported that
pseudo Class III malocclusion showed some degree of
hereditary tendency

Habitual occlusion

Centric relation

1.
2.

3.
4.

5.
6.

Clinical Examination (RABIE 2000 AJO)
Clinical examination of pseudo–Class III malocclusion
revealed that 75% of the examined cases showed a mesial
step, which corresponds to Angle’s Class I at HO and
showed a normal relationship of the primary molar that is a
flush terminal plane at CR. Diagnostic characteristics of
pseudo–Class III malocclusion could be summarized as:
Majority showed no family history.
Class I molar and canine relationships at HO and Class II or
end to end relationship at CR.
Decreased midface length.
Forward position of the mandible with normal mandibular
length.
Retroclined upper incisors and normal lower incisors.
Retrusive upper lip.

Early correction of mandibular Displacements
These should be identified at dental age 8 or 9, soon after the
permanent incisors erupt. This incisor relationship has the potential
to restrict maxillary development and encourage mandibular growth,
thereby worsening the Class III problem. This is similar to the effect
of a functional appliance in Class II treatment.
Normally, such displacements can be corrected by simple tooth
movements, and it is important for treatment to be provided at an
early age. Subsequently, unrestricted maxillary development can
resume, and if the condyles are centered in the fossae, this will
eliminate the potential ‘functional appliance’ effect of the original
mandibular displacement.

Maxillary retrognathism
Growing patients who present with maxillary
retrognathism should be considered for early expansion
and development of the maxilla. This may involve the
use of rapid maxillary expansion and a reverse
headgear. Subsequently, a palatal bar can be used to
stabilize the skeletal change, and then full fixed
appliance treatment can be commenced at
approximately 12 years of age.
Borderline surgical cases
In some cases with mandibular excess, the diagnosis
will suggest that mandibular surgery may be needed. It
is helpful to delay orthodontic treatment for such cases,
if possible. This will allow assessment of growth
patterns, using regular cephalometric radiographs, so
that a more informed surgical/non-surgical decision

Class III surgical cases
Some cases are clearly Class III surgical cases from
the outset, and should not be treated until all growth
has ceased. Timing will be beyond the age of 20
years in males and a little earlier in females.


The surgical/non-surgical decision in Class III
treatment
As with Class III treatment, it is important to
recognize those Class III cases which have a major
skeletal disproportion, either at the time of
assessment, or where there is a probability of
unfavorable growth. For such individuals, it will be
necessary to consider a surgical/orthodontic
solution. Treatment on the basis of orthodontics
alone should be delayed, or discarded as a :


Situation A – A Surgical/ orthodontic correction to an ideal
result: Determined that mandibular surgery will be required,
then the surgeon will normally wait until all growth has
finished, which may be as late as 22 years of age in males.
The surgeon will then require the orthodontist to
decompensate the incisors. Correction will be achieved by
A/P realignment of the mandible and/or maxilla, with
transverse correction of the maxilla if necessary. This should
lead to an optimal facial and dental result.

A 6-mm mandibular set-back will
result in measurements to true
vertical line (TVL) which are within
1 SD of the ideal.

Situation B – orthodontic masking of a mild Class III
skeletal case.
As an alternative to ‘A’ above, if the underlying skeletal
discrepancy is mild, it may be decided to follow a treatment
plan based on orthodontics alone. This will allow correction
to be commenced much earlier, and the patient will be
informed of the possibility of late mandibular growth. The
orthodontist will then solve the problem by ‘masking’ the
underlying Class III discrepancy by dental compensation.

In this theoretical representation, the
upper incisors were proclined 2° and
the lowers were retroclined 8°.

This will involve proclination of upper incisors and
retroclination of lower incisors. Good patient
cooperation with Class III elastics and/or a face mask
will normally be needed in this type of treatment. This
should lead to an acceptable dental and facial outcome
without the need for orthognathic surgery.


Situation C – late mandibular growth:
After orthodontic masking of a mild Class III malocclusion, late
mandibular growth can occur, especially in males. This is a
difficult situation to manage. Sometimes the patient will find
the late change in dental and facial outcome acceptable, and
seek no further treatment. However, if mandibular surgery is
deemed necessary, there is limited scope for facial
improvement from the surgery, because of the dentally
compensated teeth.

In some cases, late mandibular growth
occurs after the type of treatment
shown in ‘B’ above. This is difficult
to manage.

The incisors will need to be decompensated by
orthodontics before surgery, if there is to be an optimal
facial benefit from the surgery. The treatment of Class
III malocclusions is relatively easy when the problem is
confined to the alveolar bone, but when the deformity
is in the basal bone such as in a deficient maxilla or
overgrowth of the mandible, and then the malocclusion
does not respond readily to treatment and tends to recur
after treatment.


The “Doctrine of limitations” was in full swing in the 40”s
and 50”s.Early treatment was condemned except for
serial extractions.
The view that prevailed then was that skeletal alteration
was impossible and that the dominance of genetic
morphologic pattern was so great that it included
unaltered muscle patterns.
Further any treatment on the deciduous dentition was held
to be so temporary that it had no effect on the permanent
dentition. But evidence based researches have led to
many favorable conclusions for early treatment. Class III
malocclusion, in particular gets the nod from many
authors in favor of early treatment .Starting with Tweed,
treatment timings can be as early as 4 years of age.

Rickets (AJO 2000) has summarized the main objectives
of early treatment lying in five concepts
1. Obtaining a skeletal change (structural)
2. Providing the opportunity of a functional change in the
environment
3. Utilization of the individual growth towards the
correction.
4. Elimination of the detrimental habits (breathing etc)
5. Taking advantage of the forces of the occlusal
development towards the correction.


1.
2.
3.
4.
5.
6.
7.
8.

Turpin has developed a list of positive and negative
factors to aid in deciding when to interrupt a
developing class III malocclusion
POSITIVE FACTORS:
Good facial esthetics
Mild skeletal disharmony
No familial prognathism
Antero posterior functional shift
Convergent facial type
Symmetric condylar growth
Growing patients with expected good cooperation.
If the above factors are not present in the patient , they
are listed as negative and treatment can be delayed until
growth is completed.

Joondeph, after Turpin’s thesis, also pointed out
the goals of early intervention:
1. Reduce the skeletal discrepancy and provide a
more favorable environment for normal growth.
2. Achieve as much relative maxillary advancement
as possible.
3. Improve occlusal relationships.
4. Improve facial esthetics for more psychosocial
development.
5. Reduce or simplify, phase II or surgical treatment.


Another treatment consideration is that extraction
therapy may have limited applicability in Class III
treatment. For example, we would not want to limit
extractions to the lower arch because many times the
incisors are generally inclined lingually and extraction
treatment tends to increase this inclination, possibly
beyond the limits of the lingual plate of bone. Also,
extractions may be contraindicated when orthodontic
treatment must be combined with surgical treatment.


Another consideration is that many of the forces in conventional
orthodontics carry risks because of the unfavorable growth pattern
in patients with Class III malocclusions. For example, many
patients with Class III malocclusions have an increased vertical
face height, particularly of the lower anterior part of the face, with
an open-bite. In these patients, Class III elastics and second-order
bends in the posterior regions cannot be used conveniently because
the extrusive force components on posterior teeth can open the bite
and increase the vertical dimension further. Particular attention
must be paid to the use of Class III elastics because they can also
extrude the mandibular incisors, and there is frequently excessive
vertical dentoalveolar development in the incisor region.
Since many of the conventional treatment procedures have
limitations, we should consider the use of extra oral traction
because appropriate force systems can be placed with fewer
deleterious side effects.


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There are three important diagnostic principles which
merit attention.
First, it is particularly important to determine whether
the mandible, on closure, is in centric relation or in a
"convenient" anterior position.
The practical implication is that a Class I problem can
appear to be a Class III malocclusion (pseudo-Class III
malocclusion) when the mandible is forced anteriorly .
Even a true Class III malocclusion can appear much
more serious if there is an anterior path of closure of
the mandible


Type

Anterior
Centric relation and centric
position of
mandible
occlusion Significance

Pseudo-Class
III

Present

Not
coincident

Problem is less
difficult than it
appears ( in a
Class I) actually.

True Class III

Present

Not
coincident

Not coincident
Problem is less
difficult than it
appears

True Class III

Absent

Coincident

Problem is as
difficult as it
appears

The second principle is that the nature of the
skeletal discrepancy must be defined because
treatment, to a large extent, is based on this
differential diagnosis.
Class III malocclusions can be classified as
An under developed maxilla---TYPE A
An over developed mandible--TYPE B
A combination of TYPE A and TYPE B


Third, a malocclusion reflects the interplay of many
conditions that may be impossible to evaluate
singularly. One important variable is the potential
growth and development of a patient with a Class III
malocclusion. In this context, at least two factors may
be detrimental and aggravate Class III malocclusions
with time. One is the differential growth of the jaws,
carrying the mandible more anteriorly relative to the
maxilla. Also, local conditions (such as low tongue
posture) may adversely influence the growth pattern.
Since the amount and the timing of growth of the
mandible cannot be assessed accurately, we cannot
consider a Class III malocclusion fully resolved until
facial growth has ended.

Characteristic of this type in which the maxilla appears
retrognathic is a concave profile which represents
underdevelopment of the middle part of the face, rather
than prominence of the mandible. Treatment should be
started early, as early as 4 years of age, for two
fundamental reasons. One is that extraoral traction
which pulls the maxilla anteriorly functions in the same
direction as the direction of development. Second,
unlike posterior movement of the mandibular arch,
anterior movement of the maxillary arch appears to
have a greater chance of remaining stable. With this
kind of treatment, we can expect to achieve:

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An orthopedic protraction of the maxilla with a
strong force (500 to 1,000 Gm per side). This
change appears to be limited especially if treatment
is started after 6 years of age,
An increase in the inclination of the maxillary
incisors to obtain a sufficient overjet, associated
more or less with
Bodily movement of all the teeth in an anterior
direction, advancing point A,
Both an improvement in function and a more
esthetic profile.


The use of protraction headgear in the treatment of
Class III malocclusion was described more than 100
years ago, with other descriptions appearing early in
this century.
Early orthopedic intervention provides a non surgical
alternative in the treatment of Class III malocclusion
with maxillary retrusion. Protraction headgear provides
directed, forward growth of the maxilla at an early age.
An extra oral force of 300 gm or more per side, when
applied, can cause significant changes in the circum
maxillary sutures and in the maxillary tuberosity.
Tension produced within the sutures was believed to
cause an increase in vascularity and a concomitant
differentiation of the cellular tissues resulting in
increased osteoblastic activity.

In an animal study with tantalum implants and oxytetracycline
dyes, heavy intermittent maxillary protraction was found to
produce forward displacement of the mid face, anterior
relocation of the inferior border of the orbit, and gross osseous
alterations extending superiorly to the area of the fronto
maxillary suture. The study also found that post treatment
skeletal rebound was minimal and was observed only during the
first month after discontinuation of mechanical forces.
Clinically, the maxilla can be advanced 2 to 4 mm
over a 12 to 15-month period of headgear treatment. The use of
protraction headgear has been shown to be most effective in the
full deciduous or early transitional dentition, with less skeletal
changes after 9 years of age. A recent longitudinal study
suggested that orthopedic effects of protraction headgear on
dentofacial structure was possible in young girls as late as during
the acceleration phase of pubertal growth spurt.


DESIGN:
The orthopedic facial mask consists of three basic
components. The facial mask, a bonded maxillary splint and
elastics. The facial mask is an extra oral device composed of
a fore head pad and a chin pad that are connected with a
heavy steel support rod. To this support rod is connected a
cross bow to which are attached rubber bands to produce a
forward and downward elastic traction of the maxilla. The
position of the pads and the cross bow can be adjusted
simply by loosening and tightening set screws within each
part of the appliance.
The major modification in the appliance is the
addition of facial mask hooks in the upper first deciduous
molar. In patients in whom treatment is started before the
eruption of the upper first molars, the appliance is designed
to incorporate the first and second deciduous molars as well s
deciduous canines.

The splint is activated once per day until the desired
increase in transverse width has been achieved. In
patient in whom no increase in transverse dimension is
desired, the appliance still activated for 8-10 days to
disrupt the maxillary sutural system and to promote
maxillary protraction (HASS 1965)
After the patient has been accustomed to
wearing the maxillary splint, the facial mask treatment
is initiated. The current version of the petit facial mask
is one universal size and can be adjusted to fit the facial
contours of most patients.


SEQUENCE OF ELASTICS:

At the time of delivery
3/8”
8 oz 2 weeks

After 2 weeks
1/2”
14 oz

Increased to a max of
5/16” 14 oz
Young patients (4-9) years should wear the mask on a
full time basis except during meals. Duration is 4-6
months. They can be retained with only night time wear
or with a maintenance plate, chin cup or FR III. In older
patients, it is worn at all times except during school.


SKELETAL EFFECTS OF MAXILLARY
PROTRACTION ( sutures involved):
The maxilla articulates with nine other bones of the
craniofacial complex: frontal, nasal, lacrimal, ethmoid,
palatine, vomer, zygoma, inferior nasal concha,
opposite maxilla, and occasionally sphenoid. Palatal
expansion had been shown to produce a forward and
downward movement of the maxilla by affecting the
intermaxillary and circummaxillary sutures. The
disruption of these sutures may help initiating cellular
response in the sutures, allowing a more positive
reaction to protraction forces.


Kambara found changes at the circummaxillary sutures
and at the maxillary tuberosity attributable to
posteroanterior traction, including the opening of
sutures, stretching of sutural connective-tissue fibers,
new bone deposition along the stretched fibers, and
apparent tissue homeostasis that maintained the sutural
width. Nanda and Hickory showed how the histologic
modifications in the zygomatico maxillary suture after
maxillary protraction varied according to the orientation
of the force system applied.


Biomechanical studies on dry human skulls have
demonstrated further that the application of an anteriorly
directed force results in forward movement of the
maxilla.
These investigations also showed that the direction of the
force is critical in controlling rotation of the upper jaw.
A force generated parallel to the maxilla or above the
palatal plane produces counterclockwise rotation of the
palatal plane.


BIOMECHANICS:
The centre of resistance of the maxilla is located at the
distal contacts of the maxillary first molars, one half
the distance from the functional occlusal plane to the
inferior border of the orbit.( Lee AJO 1997) Protraction
of maxilla below the Centre of resistance produces
counter clock wise rotation of the maxilla. Also Hata
et al (AJO 1987) found using human skulls that
protraction forces at the level of the maxillary arch
produces forward but counter clock wise rotation
unless a heavy downward vector of force was applied.


A heavy force at 300 -450 gms downward to the occlusal
plane is accepted.10 degree of counter clock wise
rotation being acceptable .Force levels of 300-500 gms
on either side in both primary and mixed dentition is
recommended by most authors.
Direction of force being downward, the point of
application is 5 mm above the palatal plane in the
canine region. Hata et al suggested that an effective
forward displacement of the maxilla can be obtained
with this point of application


EFFECTS OF THE FACE MASK:
1.
The maxillary incisors moved in the anterior direction,
whereas the mandibular incisors moved posteriorly.
2.
After maxillary protraction, the maxilla was displaced
anteriorly, whereas the mandible rotated posteriorly.
3.
The mandibular plane angle and anterior lower and
total face heights increased.
4.
There is no change in SN-palatal plane angle during
growth period.
5.
These changes were reflected in the profile, whereby
the skeletal profile convexity increased and soft tissue
facial angle and facial convexity increased; and the
Class III concave profile became more balanced, with
the upper lip area becoming more marked.

6.
7.
8.

9.

10.

Position of the posterior nasal spine remained stable
Over bite was improved by eruption of maxillary and
mandibular molars.
Anchorage loss was observed during maxillary
protraction with mesial movement of the maxillary
molars. An average of 5.68 mm anterior movement of
the upper incisors resulted in a significant amount of
upper lip protraction.
The ratio of upper lip protraction to upper incisor
protraction relative to the vertical reference line was
1:1.26.
A significant decrease in upper lip thickness to
vermilion was caused by the fact that during the
treatment period, total anterior movement of the upper
incisors was approximately 1 mm more than that of the
upper lip.

11.

12.
13.

14.

15.

A significant decrease in the upper lip sulcus depth can be
evaluated as another favorable effect of the appliance on the soft
tissue profile.
The lower lip moved posteriorly to lie behind the Steiner S line,
After the correction of the crossbite in Class III cases, the lower
lip most often contacts both lower and upper incisors and would
therefore be influenced not only by the retraction of the lower
incisors but by protraction of the upper incisors as well.
Backward repositioning of the pogonion soft, and slight
inhibition of anterior migration of the lower lip was seen.
upward and forward rotation of the maxilla occurs when
protraction force on molars is applied parallel to the occlusal
plane. This type of maxillary rotation can be minimized when
the force is applied in the canine area, 20° to 30° below the
occlusal plane.


1.
2.
3.
4.
5.
6.

Maxillary advancement,
Mandibular rotation,
Labial tipping of the maxillary incisors,
Lingual tipping of the mandibular incisors,
Mesial movement of the maxillary molars,
Changes in ANB differences towards a more
positive value


One other aspect of Class III malocclusions is that a
retrognathic maxilla is often associated with a narrow
maxillary arch which is in bilateral cross-bite.
Expansion of the maxillary arch can be done at the
same time as protraction of the maxilla (which brings
it into a narrower portion of the mandible), or it can be
done later. For this purpose, a rapid maxillary
expansion appliance is used.


Rapid maxillary expansion is the corner stone of
increasing the transverse dimension in growing
individual.
In general there are three types of expansions are there to
increase the transverse dimension
1.ORTHODONTIC EXPANSION
2.PASSIVE EXPANSION
3.ORTHOPEDIC EXPANSION


RME is an indication of an orthopedic expansion
Indications for RME.







Patients who have lateral discrepancies that result in either
unilateral or bilateral posterior crossbites involving several teeth
are candidates for RME. The constriction may be skeletal (narrow
maxillary base or wide mandible), dental, or a combination of both
skeletal and dental constriction.
Anteroposterior discrepancies. For example, patients with skeletal
Class II, Division 1 malocclusions with or without a posterior
crossbite, patients with Class III malocclusions, and patients with
borderline skeletal and pseudo Class III problems are candidates if
they have maxillary constriction or posterior crossbite.
Cleft lip and palate patients with collapsed maxillae .
Procedure to gain arch length in patients who have moderate
maxillary crowding.

Contraindications for RME.
 Patients who cannot cooperate with the clinician are not
candidates for RME.
 Patients who have a single tooth in crossbite probably
do not need RME.
 Patients who have anterior open bites, steep mandibular
planes, and convex profiles are generally not well
suited to RME.
 Patients who have skeletal asymmetry of the maxilla or
mandible,
 Adults with severe anteroposterior and vertical skeletal
discrepancies are not good candidates for RME








The following factors need to be considered during
treatment planning to determine whether to expand the
dental arches conventionally or with RME:
The magnitude of the discrepancy between the maxillary
and mandibular first molar and premolar widths; if the
discrepancy is 4 mm or more, one should consider RME,
The severity of the crossbite, that is, the number of teeth
involved, and
The initial angulations of the molars and premolars—
when the maxillary molars are buccally inclined,
conventional expansion will tip them further into the
buccal musculature; and if the mandibular molars are
lingually inclined, the buccal movement to upright them
will increase the need to widen the upper arch.







The increase in mandibular plane angle with treatment
may be due to incomplete compensation of the shortterm downward displacement of maxilla by the vertical
growth of the ramus. One year after protraction, the
mandibular plane angle decreased, and this value was
significantly smaller than that of the untreated group of
age 12 . The increase in the mandibular plane angle
with treatment may be due to
The relapse of the treatment that induces vertical
increase of anterior facial height and clockwise
rotation of the mandible, and
Chin cup effects after protraction.












Correction of cross bite
Increase in arch perimeter (approx .7 times the
change in premolar width)
Correct cuspal inclinations
Improves airway function
Encourage more rapid tooth movement in mixed
dentition patients
Broaden the smile
Produces spontaneous correction of class II and
class III malocclusions.

Implant studies in expansion confirmed 50% dental
movement and 50% skeletal movement in children
and in adolescents only 35% movement was skeletal
and 65% was dental. As the patient grows older
tipping becomes greater which puts the teeth at
higher risk of gingival recession (Lindhe 1989). He
stated that “during orthodontic treatment tooth is
moved through the envelope of alveolar process at
sites with thin and inflamed gingiva and there is a
risk that gingival recession may occur.


The labial plate of bone in maxilla is extremely thin on
the facial surface of the teeth. The extensive bodily
movement of the incisors in a labial direction through
the alveolar bone resulted in a small apical
displacement of gingival margin which appeared to thin
by tooth movement and reduction of alveolar bone
height but no loss of connective tissue attachment was
apparent when there were no signs of inflammation .
Gingival graft can be used to prevent this gingival
recession


A modified protraction headgear design and the
biomechanical considerations of its clinical use are
presented by Nanda (1980 AJO). The clinical results
show that a modified protraction headgear with a chin
cup helps in the correction of moderately severe Class
III malocclusions by the anterior displacement of the
maxilla and maxillary dentition, and possibly
restricting or changing the direction of the growth of
the mandible. This headgear can also be used to correct
axial inclinations and or mesial displacement of
posterior teeth

Mc NAMARA AND SARVER ET AL (AJO 2003)
In the cephalometric investigation, authors compared
the long-term effects of an initial phase of rapid
maxillary expansion and facemask (RME/FM) therapy
followed by comprehensive edgewise therapy with the
effects of growth in untreated, matched controls.
During the post treatment period, the treated and
untreated Class III subjects generally grew similarly,
although the skeletal relationship of the maxilla to the
mandible remained unchanged in the RME/FM group,
whereas the controls had an increased skeletal
discrepancy of 3.0 mm. Over the long term, there was a
slightly greater increase in midfacial length (1.6 mm) in
the treatment group than in the controls.

Similarly, the distance from Point A to nasion
perpendicular decreased by 1.2 mm in the treated
group. The overall increase in mandibular length
was 2.4 mm less in the RME/FM group than in the
controls, and mandibular projection relative to
nasion perpendicular was 3.0 mm less in the treated
group. The change in the Wits appraisal was
substantial between groups (6.1 mm), with an
improvement in the inter maxillary relationship in
the treated group (3.4 mm. No clinically significant
differences were observed between the groups in the
vertical dimension.


Overjet increased significantly in the treated group
relative to the controls (4.4 mm), whereas the molar
relationship decreased significantly (–3.9 mm
During the post treatment period that includes the
pubertal growth spurt, craniofacial growth in
RME/FM patients is similar to that of untreated
Class III controls. Aggressive over-correction of the
Class III skeletal malocclusion, even toward a Class
II occlusal relationship, appears to be advisable,
with the establishment of positive overbite and
overjet relationships essential to the long-term
stability of the treatment outcome.

It is an example of passive expansion
INDICATION:
This appliance has been used during the deciduous,
mixed, and early permanent dentition stages to
correct Class III malocclusion characterized by
maxillary skeletal retrusion, and not mandibular
prognathism.


According to Frankel, the vestibular shields and upper
labial pads function to counteract the forces of the
surrounding muscles that restrict forward maxillary
skeletal development and retrude maxillary tooth
position. Frankel has also stated that the vestibular
shields stand away from the alveolar process of the
maxilla but fit closely in the mandible, thus stimulating
maxillary alveolar development and restricting
mandibular alveolar development. Frankel reported a
study of 74 severe Class III cases treated with the FR-3,
comparing these cases to 58 Class II cases treated with
the FR-1 appliance. He noted greater forward movement
of maxillary landmarks in the Class III cases than in the
Class II cases. He also stated that the changes in
maxillary position in the Class II cases were minimal in
comparison to what would normally occur during
growth. He concluded. from this study that the forward
development of the maxilla is stimulated by the FR-3
appliance.

Another use of the FR-3 has been suggested by Petit
in the treatment of severe Class III cases. Petit
advocates the use of heavy orthopedic forces
generated by the facial mask to achieve the initial
correction of the malocclusion. Further, he suggests
that an FR-3 may be used to retrain the maxillary
anteroposterior correction and to retrain the
associated musculature.
Eirew has stated that the FR-3 is an excellent
retraining device and aid to muscular reeducation
following surgical correction of mesiocclusion.


Construction bite
A horseshoe wafer of medium hard wax is used to orient
the upper and lower dental arches in all three planes of
space (horizontal, transverse, and vertical). Any arbitrary
adjustments in work-model orientation during appliance
fabrication can lead to an appliance that does not fit
properly.
The bite registration is taken with the patient's mandible
in the most comfortably retruded position. It is necessary
to allow 1 to 2 mm of inter occlusal space in the molar
region for the construction of the lower and, when
necessary, upper occlusal rests. A wide open-bite
registration should be avoided. In cases with an anterior
open bite, only 1 mm of vertical bite-opening in the
posterior region is necessary.

A second method involves the use of removable
appliances which are placed in the deciduous
dentition stage of development or in the mixeddentition stage when certain teeth have exfoliated or
are carious. If retention of the removable appliance
is adequate, we can apply up to 500 Gm. per side.


The orthodontic effect, moving the maxillary teeth
forward, can be achieved at any time. However, there
appear to be ''more optimum'' situations for this
procedure. One is when there is insufficient room for the
canines. In this instance, maxillary incisors can be
moved forward to make space. If orthopedic protraction
of the maxilla is also indicated, it is generally done
immediately after space has been gained for the canines
by moving the incisors anteriorly. In addition, the
maxillary teeth are protracted when the potential for an
orthopedic effect is diminished (age 9 to 10+, that is, at
the end of the mixed-dentition stage of development or
later) and when the basal discrepancy is not severe.

The movement of the maxillary teeth can be associated
with reverse torque to stimulate the most anterior part
of the maxilla to move in an anterior direction (point
A). Since the force requirements for moving the teeth
are modest, the buccal and palatal areas of the teeth are
not united and extraoral traction, pulling in an anterior
direction, can be attached to the labial arch either on
loops mesial to the canines or distal to the first molars.
Another type of appliance is a reverse headgear . This
functions to produce anterior movement to the maxilla
and to redirect the anterior movement of the mandible.
This appliance can be used when strong forces are not
necessary. Under these conditions, however, the
orthopedic effect may be limited.

REVERSE HEAD GEAR

Characteristic of this type of malocclusion is the
overdevelopment of the mandible, especially in relation
to the maxilla. The profile is flat or concave, reflecting
the hyper development of the lower third of the face
rather than the underdevelopment of the middle third of
the face. The treatment of choice would be to inhibit or
redirect the growth of the mandible. For this purpose, a
few appliances are available.
CHIN CUP :
Orthopedic force is used to protract the
maxilla, while the chincap or mental anchorage serves to
redirect mandibular growth

REVIEW OF LITERATURE:
Appliances resembling chin cups have been in use since
the early 1800's. According to Graber, the early attempts
with the chin cup were not successful because of
incomplete knowledge of mandibular and facial growth,
its use on non growing patients, and an inadequate
understanding of the forces generated by the chin cup.
Armstrong applied 500 Gm. of force via chin cups on 100
adolescent patients with mandibular prognathism. He
reported that half of his patients showed improvement in
the Class III profile, whereas none of the control, non
treated patients showed any favorable change.

Thilander treated sixty patients with chin cups for 1 to 6
years. A significant percentage of patients did not
improve. The patients who showed improvement were
comparatively young and showed favorable dental
changes. The force generated by the chin cup in his
study was only 150 to 200 Gm. Graber, Chung, and
Aoba reported results in patients treated with chin cups
for 12 to 14 hours each day with a force of 1.5 to 2
pounds on each side. They showed that mandibular
growth could be redirected with a chin cup. They
asserted that continuous use of the appliance for a long
period or through active growth was necessary to
achieve stable results.
Graber treated 35 Class III malocclusions in children
between the ages of 5 and 8 years with chin cup therapy
for 3 years. He found that the therapy was particularly
effective in patients with increased vertical growth of
the face.

Chin cup therapy primarily works on the hypothesis that
a force directed through the condyles will inhibit as
well as redirect the condylar growth. However, this
therapy alone may not be indicated for a fair percentage
of patients in skeletal Class III who show a small
midfacial bone or a retropositioned maxilla with
relatively normal mandibular dimensions. Jacobson and
associates studied 149 Class III patients and noted that
in approximately one fourth of the sample the problem
was due to maxillary deficiency.
Several clinical studies in the past have noted that
treatment of patients in skeletal Class III should include
protraction of the maxilla with or without chin cups.
Oppenheim suggested a technique for moving the
maxilla forward. He noted that restriction of growth or
distal movement of the mandible was impossible






Kettle and Burhapp reported an appliance for cleft lip
and palate which successfully inhibited forward
growth of the mandible and simultaneously caused
anterior movement of the maxilla.
Chin cup therapy may improve the following
variables of dental and skeletal Class III
morphology:
retrusive maxilla,
moderate to severe protrusive mandible,
anterior crossbite, and
concave profile.

Both animal and clinical studies of chin cap treatment
have reported and confirmed numerous statistically
significant changes in the craniofacial complex as a
result of treatment:
1. A decrease in the mandibular plane angle.
2. A decrease in the gonial angle.
3. A decrease in the SNB angle.
4. A redirection in the downward vertical growth of the
midface.
However, as Mitani and Fukazawa
and other investigators have reported, when the Class
III malocclusion is characterized by maxillary
retrusion, chincap force may have inconsistent results
and may not be the treatment of choice. In these cases,
the use of a protracting appliance, either alone or in
conjunction with a chincap, may be the treatment of
choice.

In dealing with the correction of the Class III
malocclusion with an anterior crossbite, there are two
approaches - (1) correction by adjustment of the skeletal
bones, and (2) correction by adjusting the dentoalveolar
bone. The two approaches are radically different and
diametrically opposite in basic principle. One stimulates
alveolar bone and the other inhibits alveolar bone.
Apparently, when we try to prevent forward growth of
the mandible by applying posterior and superior force
with a chin cap, it has an adverse effect on the gonion
angle - causing the angle to increase instead of decrease.
Apparently, this posterior and upward force from the chin
cap reverses the natural tendency of the gonion angle to
reduce as it grows. This involves basic biologic
phenomena, about which we have no knowledge at the
present time.

However, its application is limited to an extent because part of
the force can be dispersed as it pushes against the soft tissue
and also because there is no control of tooth position, which is
possible with other types of extraoral traction.
If we are trying to depict changes of the maxilla, it would seem
desirable to include the entire maxilla. In the illustrations
shown, only the anterior superior approximately one-half of
the maxilla (the "northeast" one-half) is included in the
maxillary triangle, while the "southwest" approximately onehalf of the maxilla, including the dentoalveolar portion, is not
included in the maxillary triangle.

The growth of the non-included portion of the maxilla
establishes the vertical dimension of the maxilla, and along
with that of the mandible establishes the vertical dimension of
the face. The mandibular triangle includes only the basal
portion of the mandible and dentoalveolar processes. " If the
"relative positions" of the maxilla and the mandible are not
rigidly specified, then vertical growth of the upper and lower
dentoalveolar processes cannot be accounted for. As pointed out
above, there are two gonion angle phenomena, (1) reduction
due to growth and (2) reduction due to Class III treatment. Also
there is a third phenomenon of mandibular change. This
involves the bending of the neck of the condyle. This backward
bending of the condyle is in response to Class II treatment with
removable appliances.

1.
2.
3.
4.

As the neck of the condyle reverts back toward its former position
post treatment, as it usually does (DeVincenzo 1991), one of four
post treatment reactions must occur;
The molar relation must revert back toward Class II occlusion,
The lower molars must move forward on the mandible,
There must be a change in the temporal mandibular
joint, or
There must be a dual bite.
The authors of the Class III study speak of”shrinkage" of the
condylion-pogonion distance, but this is a misnomer. The distance
does not become smaller, it only fails to increase in proportion to
the growth of the condyle, because of the reduction of the gonion
angle. The backward bending of the neck of the condyle followed
by a reversion to its former position must be related in some
unknown way to maintaining the constancy of the axis of the
ramus.

EXTRA ORAL TRACTION:
By means of extraoral traction we hope to obtain
a) A repositioning of the mandible posteriorly so that
the condyle enters the glenoid fossa if there is an
anterior path of closure of the mandible;
b) Orthodontic movement, inclining the teeth
posteriorly;
c) Control of the anterior bite depth;
d) Better control of the vertical dimension; and
e) Influence over the potential growth and development
of the mandible.

There are two types of extra oral traction that can be
applied to the lower arch.
1. Kloehn type of face-bow that is placed against the first
molars.
2. The other consists of facial wires placed against the
incisor segment by means of ''J" hooks or loops on the
arch wire
Practically, the Kloehn type appliance has limited
applicability in open bite cases because tipping can lead
to clockwise rotation of the mandible and it cannot
control the position of the incisor segment. On the other
hand with the use of facial wires there are a number of
beneficial effects that can be obtained. One is that
mandibular incisors can readily be retracted without
straining anchorage since Class I forces are not necessary
for incisor retraction. Second is the control of anterior
bite depth . For example, in open-bite problems, a highwww.indiandentalacademy.com
pull headgear can be used.

A straight-pull headgear can be applied when bite depth
is shallow , whereas in the presence of a deep bite a
low-pull gear is suggested . In addition, it is possible to
place the force directly against the first molars by
incorporating molar stops into the wire. In this manner,
the molars can be held in situ, as when the deciduous
second molar exfoliates and the second premolar is
erupting, or the molars can be moved distally. Also,
with facial wires, mandibular clockwise rotation with
possible increase in vertical dimension can be avoided
in open-bite cases. Further, there is the possible restraint
of forward growth.


This generally requires a combination type of therapy to produce
anterior movement of the maxilla and posterior movement of
the mandible. This is chosen when the malocclusion reflects
underdevelopment of the maxilla associated with hyper
development of the mandible. It can also be done when, during
treatment, to accept a compromise result between relationships
of the mandible and maxilla.
Maxillary protraction and mandibular retraction can be achieved
by using, in successive treatment periods, two types of extraoral
traction. For example, initially, a facial mask may be used to
gain space for the maxillary teeth and to protract the maxillary
arch. In a subsequent treatment period, an extraoral appliance
can be used to move the mandibular arch distally or, at least, to
control the incisor region and possibly influence mandibular
growth and development

Somchai Satravaha, (AJO 1999)
The activator was introduced by Andresen and has been long
served for correction of skeletal Class II malocclusions.
Rakosi suggested modification of the activator for use in
Class III treatment. The appliance consists of wire and
acrylic parts. The wire components are

4 stop-loops located mesial to all first molars to prevent
mesial tipping of the molars and to stabilize the appliance,

lower labial bow to stabilize the appliance,

upper labial pads to remove the force of the upper lip and
create periosteal pull to induce bone formation, and

tongue crib to correct anterior tongue thrusting habit.


The goal of using a Class III activator was to achieve posterior
positioning of the mandible or maxillary protraction. The
construction bite is taken by retruding the lower jaw. The
upper labial pad of the activator is intended to protract the
maxilla
Treatment Changes

Effect on a backward positioning of the mandible.

There were significant increases of the ANB angle and the
Wits values.

The SNB and SNPog became smaller resulting in increasing
facial convexity (NAPog).

The articular angle was significantly enlarged, thus
augmenting the sum of the saddle, articular, and gonial
angles.

The facial axis opened significantly.

There were significant differences in the upper face height
(N-ANS), mandibular length (Co-Gn), and ramus length (ArGo).

Dentoalveolar adaptations included labial tipping of the

Posttreatment Changes





ANB angle as well as the Wits value remained quite stable.
The SNA, SNB, SNPog, and NAPog became larger.
The articular angle was increased
The gonial angle exhibited a compensatory decline resulting in
decreasing of the sum angle

Long-term Results







The Class III activator produced a more posterior position of the
mandible and changed direction of the mandibular growth.
Both alterations remained through the post activator period.
The maxilla and the mandible grew with an increase in maxillo
mandibular differential; the maxilla remained in a more forward
position
There was significant difference in the degree of change of angle
OP/Go-Gn during the treatment but disappeared in the post
activator period due to compensatory reduction of the gonial
angle.

(JCO 1997)
The Two-Piece Corrector was designed by
Gerald.R.Eganhouse to apply biological forces that
will counteract any Class III developmental vectors,
whether skeletal or dentoalveolar, and correct or
minimize their effects on the patient . It is a removable
acrylic appliance that simultaneously applies an anterior
force to the maxilla and an equal posterior force to the
mandible. The flat, sliding surfaces of the two pieces
create almost no friction as the dentition is disoccluded
during movement, but provide both lateral and
anteroposterior stability

Appliance construction:

A construction bite of 4-6 mm thick is taken using an “Exacto
Bite” registration jig. This gives an accurate centric relation, since
the mandibular incisors can be positioned precisely. In the
laboratory, a slide is created on the articulator, with the
male(guide) portion in the maxillary acrylic plate and the female
(groove) potion in the mandibular plate. The male portion is
extended about 15 mm distal to allow for anteroposterior sliding
and to ensure lateral stability as correction progresses. The
anterior portion of the two pieces will flush when the appliance is
inserted, but the maxillary piece will gradually slide forward on
the mandibular piece


Elastics provide the force between two parts of the appliance – one
hook on each side of the maxillary plate on the disto buccal aspect
of the maxillary first molar, two located in the maxillary first
bicuspid – canine area, and the fourth placed between the
mandibular canine and lateral incisor

The shorter elastics (1/8 ” 6oz ) are attached from the
mandibular hook to the most anterior hook on the
maxilla. As treatment progresses, it is moved to the
posterior hook. The longer elastic on each side
stretched from the mandibular hook to the molar hook
can be ¼”, or 3/16” depending on the comfort.
DURATION:
12 hours a day in conjugation with face mask. 11
months of treatment time and 18 -24 months of
retention
INDICATION:
Mild skeletal class III where future surgery would not be
indicated. And used during preadolescent and
adolescent growth www.indiandentalacademy.com
periods

CLASS III BIONATOR (GARATINNI ET AL AJO
1998)
BALTERS BIONATOR III can be used in patients
with skeletal Class III malocclusion. The use of this
appliance causes some skeletal changes through
neuromuscular modifications.
CRITERIA
 Angle Class III molar relationship;
 Edge-to edge incisor position or anterior cross bite;
 Concave profile;
 Head hyperextension posture;
 Static and dynamic Class III neuromuscular
attitude;
 Hypertonic upper lip;
 Low and forward tongue rest position.

CONSTRUCTION BITE:
The construction bite was taken by gently repositioning
the mandible distally in centric relation technique. The
mandible is positioned distally, applying as little force
as possible in order to put the condyle in centric
relation, avoiding compression in the retrodiscal pad.
The vertical thickness of the bite, corresponding to the
interocclusal acrylic between upper and lower first
molar should not exceed 3 to 4 mm, Patients had to
wear this appliance for at least 22 hours a day.


RESULTS:
 Mean increase in the upper jaw length
 Advancement of point A
 Palatal and mandibular plane angles widened
 Increase of the anterior facial height
 Reduced Antero posterior mandibular growth
Therefore, the Bionator III is helpful in Class III
malocclusion treatment in growing patients with
midfacial deficiency, hypo divergent growth pattern,
and reduced facial height.


THE FOUR-STAGE TREATMENT PLANNING
PROCESS FOR CLASS III CASES
Stage 1 – setting a PIP for the upper incisors
The first stage in Class III treatment planning concerns upper
incisor position. It is necessary to determine an ideal position
and then decide whether it can be achieved. If not, a modified
position may be appropriate, which is less than ideal, but
acceptable. In this way a ‘planned incisor position’, or PIP, is
determined.

Stage 2 – the lower incisors
The second stage of treatment planning involves
positioning of the lower incisors. This is
frequently a key concern in Class III cases with
mandibular excess

Stage 3 – the remaining upper teeth
It is beneficial to evaluate the remaining upper teeth at stage 3.
If upper premolar extractions are necessary (usually second
premolars) then it is normally logical to extract lower first
premolar, in a Class III case. However, if the upper arch can
be treated without extractions, then a range of lower arch
options needs to be considered.
The third stage therefore involves deciding how to position the
rest of the upper teeth to fit the PIP for the upper incisors. It
normally assists Class III treatment mechanics if upper arch
extractions can be avoided. The dental VTO will confirm the
required movement of molars and canines.

Stage 4 – the remaining lower teeth
Lower premolar extractions assist in the retraction of
lower incisors, and are helpful to Class III treatment
mechanics in many cases. The dental VTO can be used
to reach a correct decision. In some Class III marginal
extractions cases, second molars may be considered

UPPER INCISOR MOVEMENT IN CLASS III
TREATMENT
In mild Class III cases, with a normal maxilla but
mandibular excess, the pre-treatment upper
incisor position may be close to the PIP. In this
situation, the case may require relatively little
movement of the upper incisors. However, in
many Class III cases, there will be a requirement
to move the upper incisors mesially. In some
maxillary deficiency Class III cases, it can be a
challenge to achieve the required mesial
movement without excessive Proclination. If a
Class III case requires mesial movement of upper
incisors, it can be achieved in two ways:

1. By proclination and mesial movement of upper
incisors within the available bone . Many Class III
cases require mesial movement of upper incisors, to
keep pace with the growing mandible. When upper
incisors are proclined forwards, each 2.5° of
proclination creates approximately 1mm of space per
side, or 2mm in total. For this reason upper premolar
extractions are not advisable in many Class III cases. If
upper premolars are extracted it can be difficult or
impossible to procline upper incisors.
2. By mesial movement of the maxillary bone as a result
of normal growth or orthodontic procedures.

Mesial movement of upper incisors within the
bone
During tooth leveling with the opening wires,
there is a tendency for upper incisors to move
mesially due to bracket tip, In Class III cases, this
is normally beneficial, and moves the upper
incisors towards PIP. Likewise, at the rectangular
HANT and the rectangular steel wire stages, the
A/P expansion and torque effects tend to produce
beneficial changes for most Class III cases. This
can be further augmented by the use of Class III
elastics. Because of these spontaneous tooth
movements during tooth leveling and aligning,
the early management of the upper arch in mild
Class III cases is normally straightforward

Limits to mesial movement of upper incisors
1. Excessive proclination. It is necessary to avoid excessive
proclination of the upper incisors, otherwise unesthetic
appearance and inadequate function will result. As a general
rule, proclination of the upper incisors beyond 120° to the
maxillary plane should be avoided, although there is individual
variation . In some cases, less proclination than 120° may be
appropriate. Gingival recession and long clinical crowns can
result from excessive proclination.
2. Failure to fully achieve a positive overjet. This can be due to
the forward position of the lower incisors, or other reasons, and
the resulting bite can be difficult to manage
If this is allowed to persist, then there is a risk of enamel damage
and/or root resorption. Accordingly, it is unwise to attempt to
correct a Class III incisor relationship by orthodontic procedures
alone, unless it is clear from the outset that full correction can be
achieved, and a near normal overjet obtained.

Mesial movement of maxillary bone due to growth
 Maxillary growth cannot be relied on as a useful factor
in correction of Class III malocclusions. Generally in
this type of case, maxillary growth will not be
favorable or helpful in reaching the PIP for the upper
incisor.
Mesial movement of maxillary bone due to
orthodontic treatment
 In growing individuals who have maxillary deficiency,
consideration can be given to treatment procedures
which will encourage orthopedic change within the
maxillary bone
 These can include rapid maxillary expansion, and the
use of reverse headgear

LOWER INCISOR MOVEMENT IN CLASS III
CASES
Distal movement of the lower incisors can be achieved
by distal movement of the teeth within the mandibular
bone, or by distal movement of the mandible itself,
when there is a displacement. Unfavorable mesial
movement of the lower incisors can occur because of
mandibular growth


Inter-maxillary Class III elastics are most helpful in
orthodontic (non-surgical) correction of Class III cases. They
tend to produce lower incisor retroclination, upper incisor
proclination, and A/P correction of the molar relationship. All
components of the Class III elastic force can therefore be
helpful in reaching treatment goals in average or low angle
cases.

Distal movement and retraction of the lower incisors
within the mandibular bone
In most non-surgical Class III treatments, it is helpful to
retract and retrocline the lower incisors . This can
compensate for mild mandibular prognathism or mild
maxillary retrognathism, and hence mask the
underlying skeletal discrepancy. The anatomy of the
mandibular bone in the lower incisor region places
limits on what should be attempted. Retraction and
retroclination beyond a figure of approximately 80° to
the mandibular plane is undesirable, because of the
risk of dehiscence and lack of bone support for the
over-retracted incisors. Also, dental esthetics and
function will be adversely affected

The required retraction and retroclination of the lower
incisors is normally achieved with the assistance of
Class III elastics, and treatment mechanics are easier
in cases where lower teeth have been extracted. Lower
first premolar extractions are most favorable in
assisting lower incisor distal movement, but loss of
lower second molars can also be considered .If the
lower arch is managed on a non-extraction basis, Class
III mechanics can be used to produce some retraction
and retroclination of the lower incisors.


This can produce distal tipping of the lower premolars
and molars, which in turn reduces the available space for
the lower third molars . Early removal of lower third
molars can be considered in some cases. A nonextraction approach to Class III treatment may not
achieve sufficient lower incisor movement for the needs
of the case. Correction of the malocclusion may be
possible, but not over-correction. Thus, there is no
provision in the result for any late growth changes,
which occur relatively frequently in Class III cases,
especially among male patients.


Distal movement of mandibular bone –
distal repositioning
In many Class III cases, there is a mesial displacement of
the mandible at the start of treatment. As treatment
progresses, the mandible repositions distally, to a
position with the condyles centered in the fossae. This
favorable change can be predicted at the treatment
planning stage, and is a useful adjunct to distal
movement of the lower incisors within the facial
complex.


Mesial movement of mandibular bone – Class III
growth
This is a major factor in the treatment and subsequent
retention of Class III patients, especially males. If a
decision is made to treat the malocclusion with
orthodontics alone, every patient should be informed of
the unpredictable nature of Class III growth, and of the
implications of any unfavorable growth which may
occur in the retention period.


Class III malocclusion worsens with the continuing
mandibular growth.
Relapse from continuing mandibular growth is
likely to occur and such growth is extremely
difficult to control.
Applying a restraining force to a mandible as from
chin cap is not effective in controlling growth in a
class III patient. In mild class III problems a
functional appliance or a positioner may be
enough to maintain the occlusal relationship
during post treatment growth.

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