Comparative evaluation of sagittal anchorage loss in lingual and labial appliances during space closure: A pilot study

Abstract

Aim: The purpose of this investigation was to assess and compare the anchorage
loss between labial and lingual appliance systems during space closure.
Materials and Methods: Twenty subjects were part of the study among which 10
subjects (mean age 21 ± 3.6 years) were treated using lingual appliance system
(0.018” slot-STb™) and 10 subjects (mean age 19 ± 6.1 years) were treated using
labial preadjusted edgewise appliance system (0.018” slot-MBT™). First premolar
extractions were performed to enable retraction of anterior teeth. Lateral cephalometric
radiographs were taken at two intervals, before starting space closure and after space
closure that were connoted as T0 and T1 and were analyzed using the method described
by Pancherz to measure anchorage loss. Intraclass correlation coefficient (ICC) was
used to evaluate intraexaminer reliability of the measurements. Student’s t-test was
performed to verify any statistical significant correlation between the labial and lingual
appliance systems. Statistical differences were determined at the 95% confidence level
(P < 0.05). Results: The results showed that all ICC for lingual and labial group
were ≥0.90 showing good repeatability of the measurements. Mean anchorage loss of
1.238 ± 0.17 mm in lingual appliance system and an anchorage loss of 2.06 ± 0.39 mm
occurred with the labial appliance system. On the comparison between the two appliance
systems, lingual appliance demonstrated a significantly lesser anchorage loss than did the
labial appliance. Interpretation and Conclusion: This prospective study concludes with
the fact that lingual appliance provided better anchorage control than labial appliance
during space closure. Use of lingual appliance could

Full text

APOS Trends in Orthodontics | January 2015 | Vol 5 | Issue 1
33
Address for Correspondence:
Dr. Shivanand Venkatesh, Department of Orthodontics and Dentofacial Orthopedics, Faculty of Dental Sciences, M S Ramaiah University of
Applied Sciences , MSR Nagar, Bengaluru - 560 054, Karnataka, India. E-mail: shivanand85@gmail.com
Comparative evaluation of sagittal anchorage
loss in lingual and labial appliances during space
closure: A pilot study
Shivanand Venkatesh,
Joe Rozario1,
Sanjay V. Ganeshkar2,
Shreya Ajmera2
Department of Orthodontics and
Dentofacial Orthopedics, Faculty
of Dental Sciences, M S Ramaiah
University of Applied Sciences,
1Department of Orthodontics and
Dentofacial Orthopedics, Shyamala
Reddy Dental College, Bengaluru,
2Department of Orthodontics and
Dentofacial Orthopedics, SDM
College of Dental Sciences, Sattur,
Dharwad, Karnataka, India
Abstract
Aim: The purpose of this investigation was to assess and compare the anchorage
loss between labial and lingual appliance systems during space closure.
Materials and Methods: Twenty subjects were part of the study among which 10
subjects (mean age 21 ± 3.6 years) were treated using lingual appliance system
(0.018” slot-STb™) and 10 subjects (mean age 19 ± 6.1 years) were treated using
labial preadjusted edgewise appliance system (0.018” slot-MBT™). First premolar
extractions were performed to enable retraction of anterior teeth. Lateral cephalometric
radiographs were taken at two intervals, before starting space closure and after space
closure that were connoted as T0 and T1 and were analyzed using the method described
by Pancherz to measure anchorage loss. Intraclass correlation coefficient (ICC) was
used to evaluate intraexaminer reliability of the measurements. Student’s
t
-test was
performed to verify any statistical significant correlation between the labial and lingual
appliance systems. Statistical differences were determined at the 95% confidence level
(
P
< 0.05). Results: The results showed that all ICC for lingual and labial group
were ≥0.90 showing good repeatability of the measurements. Mean anchorage loss of
1.238 ± 0.17 mm in lingual appliance system and an anchorage loss of 2.06 ± 0.39 mm
occurred with the labial appliance system. On the comparison between the two appliance
systems, lingual appliance demonstrated a significantly lesser anchorage loss than did the
labial appliance. Interpretation and Conclusion: This prospective study concludes with
the fact that lingual appliance provided better anchorage control than labial appliance
during space closure. Use of lingual appliance could be considered in critical anchorage
cases when compared with labial appliance.
Key words: Anchorage loss, labial appliance, lingual appliance
INTRODUCTION
In orthodontic treatment, anchorage loss is a potential
side-effect of orthodontic mechanotherapy and one of
the major causes of unsuccessful results. The cause for
anchorage loss has been described as a multifactorial
response in relation to the appliance type, the extraction
site, age, crowding and overjet.[1] With the extraction site,
there has been a wide belief that anchorage loss is more with
second premolars than rst premolars due to faster mesial
movement of the molar. In labial appliance, various studies
have quoted better anchorage control with rst premolar
extraction than second premolar extractions.[2-4] However,
Geron et al. reported that the amount of anchorage loss
with second premolar extraction in lingual technique is
comparable to rst premolar extraction situations (only
a difference of 0.5 mm between the techniques was
observed) and concluded that location of the premolar
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DOI:
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Original Article
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Venkatesh, et al.: Evaluaon of sagial anchorage loss in lingual and labial appliances
APOS Trends in Orthodontics | January 2015 | Vol 5 | Issue 1
34
extraction site could not be considered as signicant
anchorage loss factor.[1]
Takemoto suggested that the anchorage value of posterior
teeth is higher in lingual appliance and the direction of
forces applied during space closure brings about buccal
root torque and hence enhances anchorage.[5] Geron also
reported several factors responsible for better anchorage
control in lingual appliances and proposed six anchorage
keys to enhancing the anchorage further.[6] Although it has
been postulated that the lingual appliance has theoretically
lesser anchorage loss compared with the labial appliance,
there are very few studies evaluating the same. To the best
of our knowledge, only one study compared the anchorage
loss between labial and lingual appliances, but it was
retrospective in nature.[1] Since it has been widely believed
that lingual appliance provides better anchorage control,
it was decided to perform a prospective evaluation to best
test the hypothesis. Therefore, a pilot study to compare
the anchorage loss between labial and lingual orthodontics
would provide a better knowledge on the controversy.
Hence, this pilot study was designed to assess and compare
the anchorage loss between labial and lingual appliance
systems during space closure.
MATERIALS AND METHODS
The study was conducted on 20 subjects chosen
from Department of Orthodontics and Dentofacial
Orthopaedics, after getting an approval from the
Institutional Review Board, Ethical Committee and
an informed patients’ consent. They were selected for
the study based on the following criteria: Bimaxillary
dentoalveolar protrusion where extraction of upper rst
premolars were involved, full complement of teeth from
right rst molar to left rst molar and moderate to critical
anchorage cases requiring 75-100% retraction of anterior
teeth. All lingual cases had shallow bite, and bite blocks
need not had to be placed for vertical disocclusion since
they are known to affect the anchorage. For the purpose
of enhancing anchorage, second molars were bonded,
and archwire was passed. Patients with moderate to severe
crowding, deep bite, systemic diseases, mutilated dentition,
craniofacial or skeletal anomalies affecting the craniofacial
region, skeletal and dental Angle’s Class III and Class
II malocclusions, high angle and low angle cases were
excluded from the study.
Ten subjects between the age group 17 and 25 years (mean
age 21 ± 3.6 years) were treated using lingual appliance
system (0.018” slot Scuzzo Takemoto brackets-STb™
marketed by Ormco) and 10 subjects between the age
group 14 and 23 years (mean age 19 ± 6.1 years) were
treated using labial preadjusted edgewise appliance system
(0.018” slot McLaughlin Bennett Trevisi brackets-MBT™
Victory series™ marketed by 3M Unitek). The lingual set
up was performed on a Torque Angulation Device and
Bracket Positioning Device (Precise Indirect Bodning
SystemTM, Thailand) to set the torque and angulation
values for all the teeth. MBT prescription was followed
for the lingual setup for the purpose of standardization
with labial appliance. In the lingual appliance system,
0.012-inch Nitinol superelastic wire was the initial
archwire used followed by 0.014-inch or 0.016-inch
Nitinol superelastic wires. Leveling and alignment were
completed using 0.016-inch or 0.018-inch stainless steel
wires. 0.017 × 0.025-inch titanium molybdenum alloy or
stainless steel wires were placed for torque expression
for 3 months. Space closure by en masse retraction
was carried out on a 0.017 × 0.025-inch stainless steel
wires using sliding mechanics.[7] In the labial appliance,
leveling and alignment were completed using 0.016-inch
or 0.018-inch stainless steel archwires, followed by
placement 0.017 × 0.025-inch stainless steel archwires
placed for torque expression and space closure.[8] En
masse retraction was carried using nickel titanium (NiTi)
closed coil springs in the upper arch and E-chains in the
lower arch with a force of approximately 150 g on each
side. NiTi coil springs were not used in the upper arch in
order to prevent any injury to the tongue.
Cephalometric radiographs were taken at two intervals
during the study period: Before starting space closure
and after space closure that were connoted as T0
and T1. The lateral cephalometric radiographs of all
the selected subjects were taken in the Natural Head
Position using Rotograph 230/Eur-4 X-ray machine
(Villa system Medicali, Italy), exposed at 80 kV/8 mA
for 0.8 s. The patients were positioned for taking lateral
cephalograms as recommended by American standard
cephalometric arrangement.[9] K-separators were placed
between rst permanent molar and second molar and in
the second quadrant to differentiate between the right
(mesial aspect) and left molars (distal aspect) on the
lateral cephalogram.
All the tracings were made on 75 μm lacquered polyester
acetate tracing papers (Garware Polyester Ltd., Mumbai,
Maharashtra, India) using a 0.03 mm Staedtler™ lead
pencil. All lateral cephalograms were traced, and linear
measurements were performed to the nearest 0.001
mm using Mitutoyo Digital Caliper (Mitutoyo American
Corporation™). All tracings were done by a single
individual to eliminate the possibility of inter-operator
error. Intra operator error was evaluated by randomly
selecting 20 radiographs and repeating all the tracings
after 3 weeks by the same operator.[10] The procedure for
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Venkatesh, et al.: Evaluaon of sagial anchorage loss in lingual and labial appliances
APOS Trends in Orthodontics | January 2015 | Vol 5 | Issue 1
35
measuring the sagittal anchorage loss was performed as
described by Pancherz.[1,11] The linear distance from distal
contact point of the maxillary rst molar (M1) to a line
perpendicular to the occlusal plane through Sella (OLp)
was measured in millimetres on all the tracings [Figure 1].
The positive value obtained from the difference between
the readings corresponded to the amount of mesial
movement of the maxillary rst molar in the sagittal
plane. Anchorage loss for all the subjects was determined
in the same fashion.
Statistical analysis
The statistics were performed using Statistical Package
for Social Sciences software (SPSS 15.0, Chicago, IL,
USA). The means, standard deviations, and minimum
and maximum values were calculated. All the tracings
were repeated after 3 weeks to evaluate the intraexaminer
reliability using intraclass correlation coefficient
(ICC). ICC values equal to 0 represented agreements,
which are equivalent to that expected by chance, while
1 represented perfect agreement. An inter group
comparison between the labial and lingual appliance
group was done for determining anchorage loss during
the time (T0 and T1) periods with paired-samples t-test.
The level of statistical signicance was established at
P < 0.05.
RESULTS
The results showed that all ICC for lingual and labial
group were >0.90 showing good repeatability of the
measurements [Table 1]. Anchorage loss during space
closure was 1.2380 ± 0.1705 mm for lingual appliance
group and 2.0620 ± 0.3916 mm for the labial appliance
group [Table 2]. Thus, the results suggested more
anchorage loss with labial appliance compared with
lingual appliance.
DISCUSSION
One of the major concerns of the specialty of orthodontics
has been the development of techniques that could
adequately control anchorage units in the selective
movement of individual teeth or groups of teeth. In the
light of this, orthodontists have developed a variety of
strategies and techniques to maintain the anchorage by
applying many methods to inhibit or prevent movement of
the anchor teeth. Some of them are headgear by Kingsley,[12]
second molar inclusion, Class II elastics, anchor bends
by Begg, transpalatal arch by Goshgarian,[13] alpha-beta
bends by Kuhlberg and Burstone[14] or the recent era of
mini-implants.
Lingual appliance has been proven to have better anchorage
control than labial appliance.[1,5] Hence, this study was
performed in order to evaluate and compare the anchorage
loss between the labial appliance and lingual appliance. For
the present study, bimaxillary dentoalveolar protrusion
cases were selected with minimal crowding and hence
that good amount of space is available for retraction of
the anterior teeth and to evaluate anchorage loss. With
moderate to severe crowding cases most of the spaces
will be utilized in leveling and aligning with little space
available for retraction. Also, all the patients had shallow
bite and hence did not require the use of bite raisers, so
the negative effect of disocclusion on anchorage was
potentially eliminated.[15]
Scuzzo Takemoto (STbTM) brackets were used because
they are low prole and hence it increases the interbracket
distance when compared to the other lingual brackets. Also
since reduced interbracket distance is known to affect the
anchorage in lingual appliance and hence can induce bias in
the study.[16] In order to standardize the mechanics between
both the appliances, the slot was selected as 0.018-inch
slot size. Indirect lingual bonding setup was performed
using Torque Angulation and Bracket Positioning Device.
Standard MBT™ torque and tip values were incorporated
for standardization and also to prevent any effects of the
same on the results.
Leveling and aligning for labial appliance was achieved
in 3-6 months whereas for the lingual appliance it was
achieved in 5-9 months. Once levelling and aligning
were completed, rigid 0.017 × 0.025-inch stainless
Table 1: Intra examiner repeatability for tracings
between lingual and labial orthodontics
Group Difference (mean ± SD) Corelation coefcient
Lingual −0.09±1.1 0.92
Labial −0.21±0.85 0.97
SD – Standard deviation
Figure 1: Lateral cephalometric tracing showing measurement of
anchorage loss using Pancherz method
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Venkatesh, et al.: Evaluaon of sagial anchorage loss in lingual and labial appliances
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36
steel archwires were placed in both labial and lingual
appliances. In the labial appliance, 0.017 × 0.025-inch
stainless steel archwire was left for 1 month for torque
expression, whereas in the lingual appliance, the wire was
tied to the brackets with double over ties for effective
torqueing and was left for 2-3 months for complete
torque expression before starting space closure. Before
starting space closure compensating curves of 5-10°
were placed in the archwires to prevent bite deepening
and maintenance of torque during space closure.
Retraction hooks were placed on the same archwires,
and space closure was started with sliding mechanics
using NiTi coil springs applying a force of 150 g of each
side. Space closure for labial appliance was achieved in
8-10 months whereas for the lingual appliance it was
achieved in 9-13 months.
Although cephalometric radiographs have several
limitations it is still a valuable time tested tool in
evaluating anchorage loss and also since it is routinely
taken as a part of the treatment hence no additional
exposure to radiation to the patient.[1,17-19] With the
availability of cone beam computed tomography,
anchorage loss could be evaluated with better accuracy
but with increased radiation exposure to the patient.
Several studies have utilised dental models for evaluating
anchorage loss, but the difculty in locating stable
landmarks and its reliability precludes its use from
evaluating anchorage loss.[20,21] The Pancherz method of
assessing anchorage loss is one of the most followed and
accepted methods and hence it was used for the study.
This was the rst prospective study conducted to compare
the anchorage loss between labial and lingual appliances.
The results of the present study suggested that anchorage
loss was more in labial appliance when compared to lingual
appliance [Table 2]. This goes in accordance with studies
done by Geron et al.[1] and Takemoto.[5] The anchorage loss
difference of 0.83 mm between lingual and labial appliances
showed statistical signicance in the present study. In a
study performed by Geron, the anchorage loss difference
was slightly more (1.16 mm) when compared to our study.
This can be attributed to the use of bidimensional slot in
their study hence enhancing anchorage in lingual appliance.
Also, their study was retrospective in nature. Takemoto’s
unpublished data showed similar ndings compared to
the present study, but retraction in lingual appliance was
carried out with Loop mechanics in his study hence better
anchorage control was obtained in their study.[5]
As Scuzzo and Takemoto suggest, the lingual brackets
are closer to the centre of resistance of the posterior
teeth, hence the anchorage provided by them might
be better when compared to labial appliance. Further,
they quote that the lingual appliance has vectors of
orthodontic forces that are applied to the anterior teeth
and are directed lingually to the centre of rotation of
each tooth in the horizontal plane. Hence, it provides the
anterior teeth with a lingual crown torque. As a result,
distally uprighting forces are applied to the posterior
teeth through the archwire that makes the posterior
teeth more resistant to anchorage loss.[22] Also, the use
of 0.018” slot lingual brackets in the present study
greatly increased the rigidity of the archwires, therefore,
enhancing anchorage.
Since the present study supports the widespread belief
about lingual appliance being better in anchorage control,
it could be used in cases of moderate to critical anchorage
cases. Also, rst premolars may be preferred because
of esthetic reasons since it has a long and sharp buccal
cusp.[23]
CONCLUSION
This prospective pilot study concludes with the fact that
lingual appliance provided better anchorage control than
labial appliance during space closure. Use of lingual
appliance could be considered in critical anchorage cases
when compared with labial appliance.
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How to cite this article: Venkatesh S, Rozario J, Ganeshkar SV, Ajmera
S. Comparative evaluation of sagittal anchorage loss in lingual and labial
appliances during space closure: A pilot study. APOS Trends Orthod
2015;5:33-7.
Source of Support: Nil. Conict of Interest: None declared.
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