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Zarina Bali et al
10.5005/jp-journals-10021-1301
CASE REPORT
A Novel Approach to Correction of Class II
Malocclusion with Lower Premolar Extractions
1
Zarina Bali, 2Seema Sharma, 3Sanjay Mittal, 4Vikas Sehgal, 5Rajiv Gupta
ABSTRACT
Class II malocclusion has been the subject of interest because
of diversity in its presentation as well as multiple treatment
strategies available to correct the same. Appropriate diagnosis
of the case is very important to formulate the proper treatment
plan. A 12-year-old girl presented with skeletal Class II
malocclusion with retrognathic mandible and with Class I molar
and canine relations bilaterally. There was sufficient overjet to
advance the mandible but presence of crowding in the lower
arch necessitated reduction of tooth material in the form of
lower first premolar extractions so as to unravel the crowding
and maintain the overjet. After closure of spaces in the lower
arch, mandibular advancement was done by placing mandibular
protraction appliance IV (MPA IV). An Angle Class III molar
relation was achieved with Class I canines and Class I incisor
relations. Treatment time was 21 months.
Keywords: Class II, MPA IV, Growth modification.
How to cite this article: Bali Z, Sharma S, Mittal S, Sehgal
V, Gupta R. A Novel Approach to Correction of Class II
Malocclusion with Lower Premolar Extractions. J Ind Orthod
Soc 2014;48(4):488-492.
Source of support: Nil
Conflict of interest: None
Received on: 5/2/14
Accepted after Revision: 24/2/14
INTRODUCTION
Structural balance, functional efficiency and esthetic
harmony are the major objectives of orthodontic treatment.
Class II malocclusion forms the major bulk of patients in
our orthodontic practice. Class II can be skeletal or dental.
Skeletal malocclusion can be due to maxillary prognathism,
mandibular retrognathism, small sized mandible, large
sized maxilla or a combination of above said. Majority of
Class II cases (approximately 70%) present with underlying
skeletal discrepancy in the form of mandibular retrusion.1
Appropriate diagnosis plays a key role in formulating proper
treatment plan of the case. There are many ways to correct
1
Reader, 2-5Professor
1-5
Department of Orthodontics, DAV Dental College, Yamuna
Nagar, Haryana, India
Corresponding Author: Zarina Bali, Reader, Department of
Orthodontics, DAV Dental College, Yamuna Nagar, Haryana
India, Phone: 9416081304, e-mail: [email protected]
488
Class II malocclusion ranging from growth modification
to camouflage or surgical intervention selection of which
depends upon multiple factors. For obtaining satisfactory
results, it is better to correct underlying skeletal discrepancy
by either restricting maxillary growth or promoting mandi­
bular growth depending upon the etiology of Class II.2 For
this, there are many procedures documented but majority of
them require patient cooperation for them to be successful.
Correction by placing fixed functional appliances (FFA) is a
very good alternative as these do not rely on patient coope­
ration. Again, the choice has to be made among flexible,
rigid and hybrid types of FFA.3
Recently a number of custom made fixed functional
appliances have been introduced which can be fabricated
chairside and thus reduce the cost of the treatment. Mandi­
bular protraction appliance (MPA) designed by Coelho Filho
is one of them.4 MPA IV is the most recent version of this
appliance. The present article describes the case report of a
patient with skeletal class II malocclusion with Class I molar
and canine relations and crowding in the lower arch treated
with extractions in lower arch followed by mandibular
advancement done with MPA IV.
DIAGNOSIS
A 12-year-old girl presented with the chief complaint of
forwardly placed upper front teeth. On examination, patient
was found to have Class I molars and canines on both
sides with crowding in the lower arch, overjet of 6 mm
and overbite of 4.5 mm. Patient had an average nasolabial
angle with convex profile and potentially competent lips
(Figs 1A to F). On cephalometric examination, the patient
was found to be having Class II jaw bases with retrognathic
mandi­ble and an average growth pattern (Table 1).
TREATMENT PLAN
Although patient had Class I molar and canine relations but
the jaw bases were found to be Class II with convex profile.
The nasolabial angle as well as maxillary dental angulations
did not permit extractions in the upper arch as it could lead to
worsening of soft-tissue profile. The overjet was 6 mm and
patient had a convex profile and visual treatment objective
(VTO) was positive (Fig. 2). It was decided to advance the
mandible by a some fixed functional appliance. The growth
JIOS
A Novel Approach to Correction of Class II Malocclusion with Lower Premolar Extractions
A
D
B
C
E
F
Figs 1A to F: (A to C) Pretreatment extraoral and (D to F) intraoral photographs
status as assessed from the lateral cephalometric radiograph
depicted that 5 to 10% of adolescent growth was expected
(cervical vertebrae maturation indicator — CVMI 5).5
There was crowding in the lower arch which necessitated
reduction of tooth material in order to unravel the same and
to maintain the overjet. So, it was decided to extract the
first premolars in the lower arch, level and align both the
arches and then to go for the placement of MPA IV appliance
for attainment of normal overjet, overbite as well as for
improvement in patient’s profile.6
TREATMENT SEQUENCE
Fig. 2: Visual treatment objective photograph
A
Thirty four and 44 were extracted and strap up was done
using preadjusted edgewise appliance system (0.022 slot
B
Figs 3A and B: Molar and canine relations at the end of phase I
The Journal of Indian Orthodontic Society, October-December 2014;48(4):488-492
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Zarina Bali et al
A
B
Figs 4A and B: MPA IV in place
Table 1: Pretreatment and post-treatment cephalometric variables
Mean
Pretreatment
Posttreatment
SNA
82 ± 2°
83°
82°
N perp-pt. A
1 mm
2
1
Effective length
—
93 mm
92 mm
SNB
80 ± 2°
77°
78°
N perp. to pog
–4 – 0 mm
–6 mm
–4 mm
Effective length
—
109.5 mm
109 mm
Asc. ramus:
mand. base
0.71
0.63
0.70
Maxilla to cranium
Mandible to cranium
Maxilla to mandible (skeletal)
ANB
2 ± 2°
6°
4°
Wit’s appraisal
0 mm
3 mm
0 mm
Beta angle
27-35°
23°
23°
Vertical skeletal relation
SN-Go Gn Angle
32°
31°
31°
FMA
25°
23°
23°
Y axis (N-S-Gn)
66°
66°
65°
Dental analysis
U1-SN
102 ± 2°
113°
104°
U1-NA (angular)
22°
30°
23°
U1-NA (linear)
4 mm
6 mm
4 mm
IMPA
90°
102°
99°
L1-NB (angular)
25°
29°
32°
L1-NB (linear)
4 mm
6 mm
7 mm
MBT prescription brackets) including second molars in
both arches. As there was bolton’s excess in the upper arch,
proximal stripping was done between the premolars and
the space was consolidated distal to lateral incisors which
was subsequently closed on 0.019 × 0.025 stainless steel
490
wire with sliding mechanics. In the lower arch, canines
were retracted in the extraction space till the crowding was
unravelled in the incisor region. Later on, en masse retraction
was done using sliding mechanics.
After the closure of all spaces, the overjet was
6.5 mm. This phase took 11 months to complete. At the end
of this phase, molar relation was Class I and canines were in
Class II relation bilaterally (Figs 3A and B). At this stage,
MPA IV appliance was placed for mandibular advancement
(Figs 4A and B). After 8 months of the appliance wear,
occlusal settling was done, upper and lower bonded lingual
retainers were placed and patient was debonded after
21 months of treatment. The molar relation was settled
to Class III and canines were settled to Class I relation
(Figs 5A to F). Removable retainers (upper wrap around and
lower Hawley’s) were also given postdebonding.
The comparison of the pre and post-treatment
cephalometric variables (Table 1) derived from the pre
and post-treatment cephalograms (Figs 6A and B) and the
superimpositions (Figs 7A to C) depict the skeletal, dental
and soft-tissue changes brought about by the treatment.
DISCUSSION
Skeletal Class II malocclusion need not present itself
with Class II dental relationships always as in the present
case. Whether to treat such cases by growth modification,
camouflage or surgical intervention depends upon many
factors. Severity of underlying discrepancy, effect of
treatment on soft-tissue profile, patient’s growth status and
perception about the treatment results are few of them. In
the present case, camouflage treatment with all first premolar
extractions could deteriorate patient’s soft-tissue profile
as nasolabial angle and maxillary dental angulations did
not permit the same. So, the emphasis was placed on to
advance the mandible with fixed functional appliance. For
cases presenting at the stage when they have passed peak
height velocity and with moderate skeletal discrepancy as
JIOS
A Novel Approach to Correction of Class II Malocclusion with Lower Premolar Extractions
A
B
D
E
C
F
Figs 5A to F: (A to C) Post-treatment extraoral and (D to F) intraoral photographs
A
A
A
B
Figs 6A and B: (A) Pretreatment and
(B) post-treatment cephalograms
in the present case, growth modification cannot be ruled
out. There is data supporting the efficacy of functional
appliances during or after the onset of peak in mandibular
growth to induce favorable skeletal correction.7,8 In the
present case, there was significant crowding in the lower
arch which was corrected by lower premolar extractions in
the first phase and later on MPA IV was placed to advance
the mandible.
The overall effect of placing the functional appliance
is combination of skeletal effects and dentoalveolar
compensations. The dental compensations occurring due
to the appliance are a rule rather than exception. It has
been stated in the literature (Caridi V, Galluccio G) that
Class II molar correction averaging 6.1 mm amounts to
37% skeletal and 63% dental changes and corrections
averaging 8.4 mm amounts to 27% skeletal and 73% dental
changes.9 Functional appliances in the process of advancing
B
C
Figs 7A to C: (A) Craniofacial superimposition, (B) maxillary
superimposition and (C) mandibular superimposition
The Journal of Indian Orthodontic Society, October-December 2014;48(4):488-492
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Zarina Bali et al
the mandible have a headgear effect on the maxilla which
is responsible for decrease in maxillary dental angulations
and some of the reactionary force from forward posturing
of mandible is transmitted to lower dentition which causes
mandibular dental protrusion.10,11 In the present case,
the dentoalveolar compensations played a major role in
the correction of the malocclusion. The maxillary dental
angulations decreased owing to the headgear effect of the
appliance. Similarly, in the mandibular arch, the extraction
space was utilized for correction of crowding and later on,
the MPA IV was placed which led to the dental effects in
the form of lower dental proclinations. At the end, normal
overjet and overbite were achieved with Class I canines and
Class III molar relations with acceptable facial esthetics.
CONCLUSION
Class II correction is the amalgamation of many changes
in the skeletal and the dentoalveolar complex. Selection of
the appropriate treatment plan combined with choosing the
right appliance and the patient’s compliance are the keys to
the successful treatment of such malocclusions.
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