Class iii malocclusion /certified fixed orthodontic courses by Indian dental academy



CLASSIII MALOCCLUSION

www.indiandentalacademy.com

INDIAN DENTAL ACADEMY
Leader in continuing dental education


CONTENTS














INTRODUCTION
ETIOLOGY OF CLASSIII MALOCCLUSION
COMPONENTS
DIAGNOSIS OF CLASSIII MALOCCLUSION
PSEUDO CLASSIII MALOCCUSION
TREATMENT TIME
GROWTH PREDICTION
TREATMENT STRATERGY
FACEMASK THERAPY
CHINCUP THERAPY
COMBINED ORTHODONTIC AND SURGICAL
CONCLUSION
REFERENCES

Introduction


Class III malocclusion can be defined as
skeletofacial deformity characterized by a forward
mandibular position with respect to the cranial
base and for maxilla.



The facial dysplasia can be classified into
mandibular prognathism, maxillary retrognathism
or combination of both depending variation of the
anteroposterior jaw relation.










Vertically they can be classified as, long
average and short face.
To obtain an accurate diagnosis of class III
malocclusions, a through evaluation of the clinical
data is necessary.
1) Age, Sex, and family history of patients.
2) Molar relationship; careful assessment.
3) Craniofacial morphologic characteristics: i.e.
maxilla and mandible relation to cranial base,
intermaxillary relationship, mandibular plane
angle, gonial angle and vertical dimension.







4) Position of maxillary and mandibular incisor.
5) Soft tissue appearance : frontal and profile
views can identify the skeletal class III problem.
Functional Soft :- Some ant crossbite and skeletal
class III patients shows functional shift, due to
premature contact between maxillary and
mandibular incisors.










Angle published his classification of malocclusion
in 1899 based on the dental arch relation using
study casts.
According to Angle Class III malocclusion
occurred when the lower teeth occluded measial
to their normal relationship by the width of one
premolar or even more in extreme cases.
By cephalomatric radiograph, it is possible to
make out underlying skeletal pattern of class III
malocclusion.
Tweed divided class III malocclusion into two
categories Pseudo class III malocclusion with
normally shaped mandible and under developed
maxilla and skeletal class III malocclusion with
large mandibles.







Moyers further classified class III
malocclusion according to cause of the problem.
Osseous, muscular or dental in origin.
The frequency of Class III malocclusion varies
among different ethnic groups. The incidence of
Caucasians ranges between 1% and 4%. In
Swedish children about 4.2%.
In African American the frequency of Class III
between 5 - 8%.




In Asian society the frequency of Class III
malocclusion is higher because of a large
percentage of patients with maxillary deficiency
The incidence is 4-13% among Japanese and413% among Japanese and 4-14% of Chinese.


Etiology of Class III malocclusion:




The main etiology of Class III malocclusion is
heridity. McGuigan described the most well
known example of inheritance of the Hapsburg
family having the distinct characteristic of
prognathic lower jaw.
In 1970 Litton et al studied the families of 51
individuals with Class III anomalies and
conncluded that the dental Class III were related
to genetic inheritance in offspring and sibling.




In additions Rakosi and Sehilli suggested a role
for environmental influences such as habits and
mouth breathing in the etiology of Class III
malocclusion.



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.


Components of Class III
malocclusion :

Individuals with Class III
malocclusion may have
combination of skeletal and
dentoalveolar components.



Various components are
essential to know the under
lying cause of the
discrepancy.



The position of the maxilla,
mandible, maxillary alveolus,
mandibular alveolus and
vertical development of all
these components give three
possible values i.e. plus, zero
and minus.



Guyer et all conducted a cephalotometric study
to identify the various types of skeletal Class III
pattern between 13-15 year old children. They
found 57% of patients with either a normal or
prognathic mandible.



Masaki reported that maxillary skeletal retrusion
occurred more in Assians.



The Assian patients with Class III malocclusion
typically had a more retrussive facial profile and
a longer lower anterior facial height. A backward
rotation of the mandible with relatively smaller
maxilla.

Differential diagnosis of class III






In evaluating the class IIII relationship during
primary a mixed dentition period, it is important
to consider whether the problem is dento alveolar
or skeletal in origin.
In the diagnosis of class III malocclusion patients
may present with class III symptom such as
multiple teeth in anterior cross bite. Minimal over
jet or lingually inclined lower incisor.
Anterior cross bites may be caused by the
improper inclination of the maxillary and
mandibular incisors, occlusal interferences or
skeletal discrepancy of the maxilla or the
mandible.



Class III malocclusion caused by a dento alveolar
malrelationship.



In the dento alveolar class III malocclusion there
is no apparent skeletal discrepancy. The ANB
angle is normal. The problem is primarily caused
by lingual tipping of maxillary incisors and labial
tipping of mandibular incisors.

Skeletal Class III malocclusion with mandibular
protrusion, maxillary retrusion or a combination
of both:




The ANB angle in patients with skeletal Class III
malocclusion is generally negative & decreased
SNA angle and increased SNB angle. If there is
any variations in cranial base flexure and
anteroposterior displacement of nasion alters the
ANB angle. So alternate measurement include
nasion perpendicular to the point A, wits appraisal
and effective maxillary and mandibular length.



Vertically, patients with a long mandibular base
usually have a large gonial angle. The incisal
inclination in skeletal Class III, upper incisors are
tipped labialy and lower incisors are tipped
lingually.


Pseudo Class III malocclusion :

Kwavang and Lin conducted a cephalometric
study comparing the characteristics of patients
with Class I, pseudo ClassIII and skeletal Class
III malocclusion.



Most of the ceephalometric measurements
suggested that pseudo Class III malocclusion is
an intermediate form between class I & III
malocclusion. The only exception was the gonial
angle, which was more obtuse in skeletal Class
III sample.
measurement of gonial angle in pseudo Class III
was found to be similar to Class I sample. This is
main key point in pseudo and Class III
malocclusion.




Class III skeletal growth pattern


Cranial base :-

Battagel found the linear and angular
measurements of the cranial base
were decreased in patients with
Class III malocclusion. Cranial
base angle is acute and exhibited
a more anteriorly positioned
articulare compared with Class I
malocclusion.
Middle cranial fossa is in Class III
patients has posterior and superior
alignmet. This alignment positions
the nasomaxillary complex in more
retrusive relation and contributes
to a forward rotation of the
mandible.


Maxilla:

Patients with a Class III
malocclusion commonly exhibited
decreased horizontal maxillary
growth when compared with the
patients with a Class I
malocclusion.



Mandible :- The individual with a
Class III malocclusion exhibits an
increased length of the mandible,
where as mandibular articulation
more anteriorly positioned,
resulting in a more prominent
lower jaw. The gonial angle is
obtuse in Class III malocclusion
than in class I malocclusion




The malocclusion prominences along with the
decreased length of the maxillary complex may
accentuate the typical straight to concave profile
in these cases.

Patients with Class III malocclusion display
dento alveolar compensation in the form of
proclination of maxillary incisors accompanied
with retroclination of the mandibular incisors.


Treatment timing of Class III
malocclusion




Class III malocclusion is established early in life
and is not a self correcting disharmony.
Cephalometric and morphometric gives treatment
of Class III malocclusion. It is carried out more
efficiently during early mixed dentition than late
mixed dentition.
At post pubertal observation (Cs5 and Cs6) when
active growth of the skeleton is completed. Class
III subjects treated with rapid maxillary expander
and facial mask well before the growth (CS1)
present and there will be peak mandibular growth
at cs3 stage.


Rationale for early treatment of Class III
malocclusion
1)

To prevent irreversible soft tissue or on bony
changes. Often associated with anterior
crossbite leads to abnormal wear of lower
incisor. Dental decompensation of mandibular
incisors leads to tinning of alveolar place and
gingival recession.

2) To improve skeletal discrepancies. Early
orthopedic treatment using facemask or chin
cup therapy improve skeletal relations which
minimize excessive dental decompensation i.e.
over closure of mandible and retroclination of
mandibular incisor.

3) Early treatment eliminate the functional shift,
CR.Co discrepancies and prevents severe
orthognathic surgeries .
4) Early treatment provides pleasing profile thus
provides psycosocial development of a child.


Class III Growth Predictions
In 1970 Dietrich reported that Class III skeletal
discrepancies with age. Children with a negative
ANB angle were examined in three stages.



Stage I





-

Primary

-

23%

Stage II -

Mixed

-

30%

Stage III -

Permanent dentition - 34%









Maxillary anteroposterior deficiency problem 26%
- 44% -37%. These all results indicates that the
abnormal skeletal characteristical can become
move pronounced with time.
Growth prediction can be used to differentiate
Class III tendency and identify specific skeletal
morphologic pattern.
Certain cerphalometric measurements such as
cranial flexura. Porion location and ramus position
have been used predict normal or abnormal
growth.
Mito and Cowarkers suggested that accuracy of
prediction is around 70-80% is by use of cervical
vertebral bone age to predicted mandibular
growth-potential.

Growth treatment Response vector
(GTRV) Analysis:


GTRV analysis is performed in early
permanent dentition. This gives clinicians
to decide whether the malocclusion can be
camouflaged by orthodontic or by surgical
intervention once the growth is completed.



The GTRV ratio was calculated by using
formula

GIRV =Horizontal growth changes of maxilla
Horizontal growth changes of mandible
GRTV ratio normal indivisual 0.77 mm at age
8-16 year.


In case of Class III patient have GTRV Ratio 0.330.88 maxillary deficiency and can be successfully
treated by camouflaged with orthodontic Rx.
Class III patient with excessive mandibular growth
with GTRV<0.38 then it indicated orthrognathic
surgery.


Growth in patients with Class III
malocclusions


The craniofacial skeletal pattern of children with
Class III malocclusion is evident in the early
deciduous dentition.



A sample of 69 Class III subjects was compared
with 60 subjects exhibiting normal occlusion.
They showed both maxillary retrusion and
mandibular protrusion with additional other
skeletal characteristics are short anterior cranial
base length, larger mandibular ramus height and
corpus length.






The mean annual growth increment for the
maxilla was 0.8mm in Class III subjects and1.1
mm in normal subjects during early mixed
dentition and late mixed dentition 1.1 mm in
Class III and 1.4 mm normal subjects.



The mean annual growth of mandible is 4.5mm
vs 2.6 mm in early mixed dentition and 4.4 vs
2.8 mm in late mixed dentition.



Class III skeletal imbalance shows either edge to
edge incisor relationship or an anterior crossbite
in deciduous dentition.



The skeletal components of the class III
malocclusion tend to worsen along with
subsequent growth.

The selection of treatment stratergies:

When a patient is diagnosed as a Class III
malocclusion in the permanent dentition and if
there is a strong skeletal component to the Class
III malocclusion then treatment options are lesss.



Such treatment usually includes comprehensive
orthodontic therapy, either combined with
extraction or orthognathic surgery.




The orthognathic surgical procedure is designed to
address the imbalance of the skeletal component
(eg: mandibular set back in patient with
mandibular prognataism and lefort I advancement
in maxillary skeletal retrusion.)



In patients who are expected to have excessive
skeletal growth in the future, the surgical procedure
is usually deferred until the end of active growth
period.



In the diagnosis and treatment planning of patients
who present with a Class III malocclusion in the
late deciduous or in the mixed dentition, several
treatment options are available.

The Orthopedic facial Mask


Though the facial mask was developed over 100
yrs ago it was reintroduced by Delair in 1960 for
the treatment of cleft patients again it is modified
by Petit.



The most young Class III patients were
candidates for facial mask treatment. Thus this
treatment protocol can be applied to most
developing Class III patients regardless of the
specific etiology.




Modified maxillary protraction


Treatment timing for Orthopedic facial
Mask Therapy:


Recent studies showed first treatment of Class III
malocclusion with facial mask in early mixed
dentition results in more favorable for craniofacial
changes than in late mixed dentition.



This is mainly due to changes in maxillary suture
which leads to forward displacement of maxilla in
early mixed dentition.



All these observation suggest that the early
mixed dentition phase of dental development is most
appropriate period to perform treatment of Class III
malocclusion with the orthopedic facial mask.

Chincup therapy


Skeletal Class III
malocclusion with relatively
normal maxilla and
moderately protrusive
mandible can be treated with
the use of a chin cup.



Early treatment with
chincup provides better
grown inhibition or
redirection and post
positioning of the mandible.

Effects on mandibular growth:

The orthopedic effects of a chin cap
on mandible includes

1)

redirection of mandibular growth
vertically.
backward rotation of mandible.
Remodeling of mandible with
closure of the gonial angle.

2)
3)


Effects on Maxillary growth:

Some studied have indicated that a chincap
appliance has no effect on antero posterior
growth of the maxilla. But early correction of an
anterior crossbite with chincap prevents
retardation of A-P maxillary growth.

Force magnitude and duration:Chin caps are divided into two types
1) occipital chincap that is used for patients with
mandibular protrusion.


2) vertical pad chincap used in patient with steep
mandibular plane angle and excessive anterior
facial height.
Orthopedic force is about 300-500 gm / side.
Patient is in instructed to wear 14 hr/day. The
orthopedic force is usually dilevered either
through the condyle or below the condyle.


Treatment timing and duration:

Patient with mandibular excess usually
recognized in the primary dentition because most
of children will have retrusive mandible.



To reduce the mandibular protrusion is more
successful when treatment is started in primary
or early mixed dentition. The treatment time
varies from 1 year to as long as 4 year depending
on the severity of the original malocclusion.


Stability of treatment:


The stability of chincap treatment is still unclear.
Some studies showed mandible has tendency to
retain to original growth pattern after chincap is
discontinued.



When treatment is started at an early age
mandible is displaced farward and downward
direction before the growth is completed. So they
concluded that chincap therapy should be
extended over the growth period for best skeletal
results.

Effects on TMJ:

There is some adverse effect of chincap therapy
on the TMJ. Some studies showed temporary
soreness of the TMJ during retention period. They
have some degree of difficult in opening mouth
after the end of active treatment.


Treatment of Class III malocclusion


Reverse twin Blocks:-


Frankel III appliance


Activator and bionator


Two piece corrector for classIII skeletal and
dental malocclusion


Functional orthopedic magnetic appliance
(FOMAIII)


EARLY ORTHOPEDIC CLASSIII TREATMENT
WITH MODIFIED TANDEM APPLIANCE


Mini maxillary protractor for classIII CORRECTION


Non surgical treatment of an adult
skeletal classIII patient.


Tooth borne orthopedic maxillary protraction
in class III patients


Combined orthodontics and orthognathic
surgery.


Early surgery is possible in maxillary defecient
but surgical intervention in young child may
further adversely affect the growth of maxilla.



Patients with true mandibular prognatism may
continue to grow for several years beyond the
puberty so that two lateral cepholograms are
taken at least 1 year alpart demonstrate no
significant growth occurring over that period.




The current surgical methods for correcting
skeletal Clalss III problems include names
osteotomy to set back a prognathic mandible.



Mandibular inferior border osteotomy to reduce
chin height or prominence.



Lefort I osteotomy to advance a deficient
maxilla.


Treatment to camouflage the Class III skeletal
discrepancy.


Skeletal discrepancies can not be resolved during
mixed dentition by growth modification may
require comprehensive appliance therapy or
surgical correction.



Some patients treated in early childhood may
recur malocclusion during adolescence.
Treatment in adolescence is indicated to alleviate
the potential psychosocial problems and reduce
the need for surgery. Malocclusion with mild
mandibular prognathism and moderate overbite
can be corrected by dento alveolar movements.



Class III elastics with or without extraction of
teeth are used to camouflaged the skeletal
discrepancy, resulting in acceptable facial profile.



As early as 1907 Edward Angle suggested that the
only way to correct severe Class III malocclusion
in adult was to combine surgery and orthodontic
treatment.



Before 1970s must thought that Class III
malocclusion were primarily caused by excessive
anteroposterior growth of the mandible and most
were corrected by mandibular setbacks
procedures.



However later studies indicated 20-25% of
mandibular protrusion,but also around 75% of
maxilla deficient cases also leads to Class III
malocclusion so that clinician should analyse
where the fault,whether in maxilla or mandible or
combination.



Maxillary growth may be completed at age 15 or
14 years were as mandibular growth may
continue until early 20 ears. After this surgical
procedure can be carried out.


Pre surgical orthodontics:for mandibular prognathism


Eliminate anterior and posterior dental
compensation with guideline from orthodontic
visual treatment objectives.



Establish appriate anteroposterior and vertical
incisor position.



Achieve compatible arch forms and inter canine
widths, which are essential to make dental
midlines compatible at surgery.



Correct tooth size discrepancy


Orthodontic mechanics:
Mandibular arch:

Class III mechanics, molar tie backs are not
used when leveling and teeth are allowed to
level forward. The orthodontic VTO should be
referred to confirm the extent of incisor
decompensation required.


On the completion of leveling, ClassII elestics
may be used to advance the mandibular buccal
segment and further to procline the mandibular
incisors.




When decompensating the mandibular
incisors, clinician should keep in mind,
patient with mandibular antero posterior
excess often have a very thin bony
symphysis and a small area of attached
gingiva in the incisor region.


Surgical treatment:



Bilateral sagittal split osteoteomcy is the
procedure of choice, although transoral vertical
ramus osteotomy may be indicated in large
setback procedures.
Correct positioning of condyle is important. The
surgeon should carefully free the medial
pterygoid an a stylo mandibular ligament from
the medial side of the ramus. Otherwise
proximal segment will be pushed back by distal
segment with return of mascle function, the
patient will tend to position mandible forward
again.




The incidence of neurosensary morbidity with
transoral Vertical ramus osteotomy is less
associated with bilateral sagittal split ramus
osteo-tomy.



A genioplasty is often indicated to place the
chin in most esthetic antero posterior, vertical
and midsagittal position.


Post surgical orthodontic:

If f tendency to relapse is noticed, light (2.5-3.5
oz) Class III elastics should be placed
immediately.



A rectangular arch wire should be placed in
maxilla to prevent the molar extrusion.



The clinician should design the retention plan
according to original malocclusion and its
possible relapse tendency.


Maxillary Anteroposterior deficiency:

Maxillary anteroposterior deficiency often
misdiagnosed as mandibular anteroposterior
excess. So therefore clinician must carefully
distinguish between the two deformities.

Pre surgical orthodontics:
Same as done previous mandibular prognathism.
i.e. 1) Eliminate compoensation
2) Establish ideal incisor position
3) establish arch compatibility
4)level and align the arches.



Cases of maxillary deficiency often involve
crowding in the maxilla and retraction of incisor
is indicated.

This will require extraction of teeth.
1.If maximum retraction is necessary or significant
crowding patient present then extn of 1st
premolar is indicated
2.If little retractionis necessary and crowding is
slight then second premolar is indicated.
3. Advancement of mandibular incisors from an
upright or lingualy tipped position may be
limited by lack of attached gingiva or thiin
alveolar bone and symphasis mandibular
second premolar is necessary to provide require
space to manage crowding.





The most common retraction of Class III case
maxillary first premolar and mandibular second
premolar (Reverse in Class II)
Orthodontic Mechanics:Pre surgically, the maxillary incisors should be
placed in good angulation in the central trough
of bone. To achieve best esthetic results.
Surgical treatment:-The maxilla is advanced by
means of Lefort I Ostevtomy. So surgeon
can correct discrepancies in the vertical
transverse and occlusal planes.



Undesirable soft tissue changes may occur,
including widening of, tipping up of the nose and
increasing nasolabial angle. So that patient
should be informed about expected soft tissue
changes.



Post surgical orthodonties:Similar to treat of mandibular set back
surgical splint is given only in multipiece Lefort I
maxillary osteotomy is performed or bijaw
surgeries. Once the splint is removed
immediately the orthodontist should place
orthodontic palatal bar and continuous arch wire
to maintain achieved results.

Conclusion






To improve skeletal discrepancy and provide a
more favorable environment for future growth.
Early orthopedic treatment using face mask or
chin cup therapy improve skeletal relations which
in turn minimizes excessive dental
decompensation.
Early treatment provides more pleasing facial
profile, thus improves psyco-social development
of child.
It eliminates orthognathic surgery maximizing
growth potential of maxilla may minimize the
extent of surgical procedures in cases of severe
Class III malocclusion.

References









Contemporary orthodontics; william R. profit
Early orthodontic treatment, J daniel subtenly
Orthodontics current priciplesand techniques, T.M
Graberand vanarsdal
Biomechanics and esthetic statergies
In clinical orthodontics, Ravindra nanda
Text of orthodontics, samier bishara
Graber petrovic rakosi
Seminar in orthodontics 2005


THANK YOU
Leader in continuing dental education


Class iii malocclusion /certified fixed orthodontic courses by Indian dental academy

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (20)

En vedette

En vedette (20)

Similaire à Class iii malocclusion /certified fixed orthodontic courses by Indian dental academy

Similaire à Class iii malocclusion /certified fixed orthodontic courses by Indian dental academy (20)

Plus de Indian dental academy

Plus de Indian dental academy (20)

Dernier

Dernier (20)

Class iii malocclusion /certified fixed orthodontic courses by Indian dental academy