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Orthodontic Journal of Nepal, Vol. 8 No. 1, June 2018
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INTRODUCTION
Treatment plan of growing Class II patients should be
directed towards solving the dento-skeletal disharmony
in order to obtain favorable facial aesthetics.1,2
Treatment of Class II malocclusion may involve the
use of orthopedic appliances, extra oral traction and
functional appliances. Functional appliance therapy
is a commonly used treatment protocol for growing
Class II patients with mandibular deciency.3
The selection of functional appliances is dependent
upon several factors which can be categorized into
patient factors e.g. age and compliance, and clinical
factors e.g. preference/familiarity and laboratory
facilities. Different types of functional appliances are
available for the correction of Class II skeletal and
occlusal disharmonies.4 Twin Block (TB) and Herbst (HB)
appliances are among the most popular functional
appliances.5 TB appliance is the most preferred
functional appliance in UK,6 and HB is most commonly
used in USA.7
Dr Khurram Shahzad,1 Dr Javeeria Asif Cheema,2 Dr Muhammad Azeem,3 Dr Waheed Ul Hamid4
1Resident Orthodontics, Children's Hospital & Institute of Child Health, Lahore
2Assoc Prof, 4Professor Orthodontics, de'Montmorency College of Dentistry, Lahore, Pakistan
3Asst Prof Orthodontics, Dental Section-Faisalabad Medical University/Punjab Medical College, Pakistan
Correspondence: Dr Muhammad Azeem; Email: dental.concepts@hotmail.com
Dentoskeletal Changes in Class II Subjects following Treatment
with Twin Block and Herbst Appliance
Research Article Randomized Controlled Trial
ABSTRACT
Objective: To compare the mean changes in dentoskeletal parameters in Class II patients treated by Twin Block versus Herbst
appliance.
Materials & Method: The study was conducted at the Orthodontic Department of Children’s Hospital and Institute of Child
Health and de’Montmorency College of Dentistry, Lahore. The study involved 50 patients those were randomized in equal
numbers according to lottery method to either Group-1 (Twin block) or Group-2 (Herbst). Mean changes in SNA, SNB and IMPA
at the end of treatment was calculated by subtracting Pretreatment measurements (T1) from post treatment measurements
(T2). Student t–test was used to compare the mean changes in dentoskeletal parameters in both groups.
Result: The comparison showed that the mean difference recorded in SNA values was -1.06±0.62 in Group-1 and -1.28±0.61 in
Group-2 (p-Value 0.07), SNB was 2.14±0.70 in Group-1 and 1.22±0.55 in Group-2, (p-Value 0.001) while IMPA was 1.58±0.64 in
Group-1 and 4.8±1.31 in Group-2 (p-Value 0.001).
Conclusion: There was a signicant difference between mean changes in dentoskeletal parameters in Class II patients treated
by twin block when compared to Herbst appliance.
Keywords: Class II malocclusion, dentoskeletal, Twin Block, Herbst
TB was rst introduced by Clark in 1988 and consists of
two separate, upper and lower, removable plates with
acrylic blocks trimmed to an angle of 70 degrees.8 TB is
widely used because of its high patient acceptability
and ability to produce rapid treatment changes.8
The HB appliance was rst introduced in 1900s by
Emil Herbst as a xed bite-jumping device, and later
Pancherz reintroduced it in the 1970’s as a banded
appliance.9 It has been reported that HB appliance
can correct Class II skeletal problems by encouraging
mandibular growth.10
Many studies have been carried out on soft tissue
effects of these appliances,2-5 but only a few studies
have compared the dentoskeletal effects of TB and HB
in Class II patients.11-13 In addition, no single study has
been carried out specically on dentoskeletal effects
of TB and HB in South Asian population. It should be
kept in mind that skeletal effects vary among subjects,
between gender groups, with genetic inuence and
with the time of therapy.
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Orthodontic Journal of Nepal, Vol. 8 No. 1, June 2018
Thus the objective of this study was to compare the
mean changes in dentoskeletal parameters in Class II
patients treated by Twin Block versus Herbst appliance.
Our hypothesis was that there is a difference between
mean changes of dentoskeletal parameters (SNA, SNB
& IMPA) in Class II patients treated by twin block versus
Herbst appliance.
MATERIALS AND METHOD
The randomized controlled trial was conducted after
taking ethical approval and informed consent in
the Orthodontic Department of Children’s Hospital
and Institute of Child Health and de’Montmorency
College of Dentistry, Lahore, Pakistan. Sample size
of 50 cases (25 in each group) was calculated with
95% condence level, 80% power of test, and taking
expected mean ± S.D of mean change in SNA in both
groups, i.e. -1.35±1.11 in Herbst group vs. -0.75±1.03 in
Twin block group in Class II patients.13
Patients were selected according to following
inclusion criteria: Skeletal Class II relationship (ANB >4°,
SNB<78°), patients’ age ranged between 9-13 years,
Overjet ≥ 5mm, SN–MP= 32°±4° and bilateral Class
II molar and canine relation. Patients with previous
history of orthodontic treatment, congenitally missing
or extracted permanent tooth (except third molars)
and syndromes, skeletal dysplasia were excluded.
Study involved 50 patients those were randomized in
equal numbers according to lottery method to either
Group-1 (Twin block) or Group-2 (Herbst). For Group-I,
Twin block group patients were instructed to wear the
appliance full time. For Group II, Acrylic splint design
of Herbst was inserted. When a normal or corrected
overjet in retruded position was recorded, the active
treatment was nished and cephalometric records of
patients were taken in both groups.
Dentoskeletal measurements (SNA, SNB & IMPA) were
measured on lateral cephalometric radiographs
before start of the treatment and at the time of
removal of appliance and these measurements were
taken by the researcher himself to address bias. Mean
of dentoskeletal changes was measured at the end of
treatment by calculating the difference between post-
treatment and pre-treatment values taken on lateral
cephalogram. In dental part; only one value of Lower
incisor to mandibular plane angle (IMPA) was taken by
measuring the angle between body of mandible and
long axis of most proclined lower mandibular incisor.
In skeletal part; two measurements were taken: SNA
angle (SNA): inward angle between NA line and Sella–
nasion (SN) plane with normal value 80-84°, SNB angle
(SNB): inward angle between NB line and SN plane
with normal value 78-82°.
All statistical analysis was done using SPSS 20.0.
Pre-treatment and Post treatment dentoskeletal
measurements and age were presented as means
and standard deviation. Gender was presented by
frequency and percentage. Mean changes in SNA,
SNB and IMPA at the end of treatment was calculated
by subtracting Pretreatment measurements (T1) from
post treatment measurements (T2). Student t –test was
used to compare the mean changes in dentoskeletal
parameters in both groups. p≤0.05 was considered as
signicant. The data was stratied for age and gender,
to address the effect modiers. Post stratication
student t–test was applied to check the signicance,
with p≤0.05 as signicant.
RESULT
Age and gender distribution of the patients is shown in
Table 1. Comparison of mean changes in dentoskeletal
parameters in Class II patients treated by Twin block
versus Herbst appliance is given in Table 2. The data
were stratied for age and gender to control the effect
modiers, which showed insignicant ndings with
regards to age and gender.
Table 1: Distribution of sample according to age and gender
Sample
Group-1 (Twin block) n=25 Group-2 (Herbst) n=25
No. % No. %
Age
(in years)
9-11 18 72 16 64
12-13 728 936
Mean 10.66±1.32 10.86±1.41
Gender Male 10 40 936
Female 15 60 16 64
Total 25 100 25 100
Shahzad K, Cheema JA, Azeem M, Hamid WU : Dentoskeletal Changes in Class II Subjects following Treatment with Twin Block and Herbst Appliance
Orthodontic Journal of Nepal, Vol. 8 No. 1, June 2018
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The differences in mean pre-treatment SNA values were
not statistically signicant. Mean post-treatment SNA
values were 81.18 in Group-1 and 80.8 in Group-2, SNB
was 84.38 in Group-1 and 76.34 in Group-2, IMPA was
97.2 in Group-1 and 100.62 in Group-2. The differences
were signicant. The ndings for post-treatment mean
difference in SNA values was -1.06 in Group-1 and
-1.28 in Group-2, SNB was 2.14 in Group-1 and 1.22 in
Group-2, IMPA was 1.58 in Group-1 and 4.8 in Group-2.
The differences were signicant, except for SNA values.
DISCUSSION
Results of the current study showed that there was
a signicant difference between mean changes in
dentoskeletal parameters (SNA, SNB, IMPA) in Class
II patients treated by twin block when compared to
Herbst appliance. In comparison of results of Baysal
and Uysal,13 SNB angle was increased in Twin block
group than in Herbst group. The change in SNA angle
was greater for Herbst group than that in Twin block
group. The increase in lower incisor proclination (IMPA)
was also found greater in Herbst group than that in
Twin Block group. Similar ndings were recorded in our
study.
Schaefer et al14 compared the effects of Twin-block vs.
Herbst for correcting Class II disharmony, they were of
the view that treatment effects of both protocols led
to a normalization of dentoskeletal parameters at the
end of the overall treatment period. However, only
minor differences were detected in the treatment and
Table 2: Comparison of mean change in dentoskeletal parameters
Parameter
Group-1 (Twin block) Group-2 (Herbst)
p-Value
Mean SD Mean SD
Pre-treatment
SNA 82.24 0.82 82.08 0.97 0.37
SNB 75.26 1.29 75.12 1.32 0.59
IMPA 95.62 2.27 95.82 2.32 0.66
Post-treatment
SNA 81.18 0.77 80.80 1.16 0.05*
SNB 84.38 1.07 76.34 1.44 0.001*
IMPA 97.20 2.33 100.62 2.83 0.001*
Mean difference
SNA -1.06 0.62 -1.28 0.61 0.07
SNB 2.14 0.70 1.22 0.55 0.001*
IMPA 1.58 0.64 4.80 1.31 0.001*
*Statistically signicant at p≤0.05
post-treatment effects of crown herbst and twin-block
appliance.
It is well known that a point in disfavor of HB treatment
is a proclination of lower incisors due to the forces
exerted on the lower teeth by the same telescope
device. Various modications of original HB have been
proposed to counter the proclination of mandibular
incisors.15 It has been proved in the literature that
functional appliances do not produce long term
skeletal changes and most of their effects are dento-
alveloar.16 In a prospective controlled trial with twin
blocks and controls to investigate the skeletal and
dental effects showed that the ANB angle reduced by
2° which was almost entirely due to mandibular length
increase which was 2.4 mm compared to the controls
and there was no evidence of a restriction in maxillary
growth.17
Limitations of this study are sample size and single
centre approach. Further studies are required to
validate results of current study.
CONCLUSION
There was a signicant difference between mean
changes in dentoskeletal parameters in Class II
patients treated by twin block when compared to
Herbst appliance.
OJN
Shahzad K, Cheema JA, Azeem M, Hamid WU : Dentoskeletal Changes in Class II Subjects following Treatment with Twin Block and Herbst Appliance
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Orthodontic Journal of Nepal, Vol. 8 No. 1, June 2018
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Shahzad K, Cheema JA, Azeem M, Hamid WU : Dentoskeletal Changes in Class II Subjects following Treatment with Twin Block and Herbst Appliance