Download Alessio, Rodrigues, Gregorio - Transverse stability of Class II malocclusion correction with the pendulum appliance

ORIGINAL ARTICLE
Transverse stability of Class II
malocclusion correction with the
pendulum appliance
Grego
rio Pelayo Guerra,
Luiz Eduardo Alessio Junior, Renato Rodrigues de Almeida, Jose
rio Vieira Maranha
~o, and Guilherme Janson
Olga Bena
Bauru, Brazil
Introduction: This study aimed to evaluate the stability of transverse changes after Class II malocclusion correction with the pendulum fixed distalizer, followed by preadjusted edgewise fixed orthodontic appliances.
Methods: This longitudinal study was conducted in the maxillary dental casts of 20 Class II malocclusion subjects (mean age, 12.5 years; 14 females and 6 males). Eighty 3-dimensional maxillary dental casts were
analyzed; 20 at the beginning of treatment, 20 after distalization, 20 after edgewise appliance debonding, and
20 at 5 years posttreatment. Maxillary transverse distances between canines, first premolars, second
premolars, first molars, and second molars were analyzed using Geomagic Studio 5 (3D Systems, Rock Hill,
SC). Results: There were no significant changes in intercanine distance during and after treatment. There
were significant interfirst and intersecond premolar distance increases during treatment. There were significant
interfirst and intersecond molar distance increases during the distalization phase. However, there were significant decreases in these distances at the end of treatment. There were no significant long-term posttreatment
changes. Conclusions: The intercanine distance remains stable during and after treatment. The interfirst
and intersecond premolar distances significantly increase during treatment and remain stable after treatment.
The interfirst and intersecond molar distances increase during the distalization phase, decrease at the end of
treatment, and remain stable after treatment. (Am J Orthod Dentofacial Orthop 2020;158:357-62)
C
lass II malocclusion should be considered not only
a sagittal but also a vertical and transverse problem.1-3 There are several treatments and devices
that have been widely used as alternatives for Class II
malocclusion correction and nonextraction treatment.4-8
The pendulum fixed distalizer (PFD) is indicated for the
nonextraction treatment of dental Class II malocclusions
during the mixed or early permanent dentition.9,10 It provides dental effects in short treatment time, so that in
3-4 months, it is possible to obtain approximately 5 mm
of molar distalization.6 In addition, it does not depend
on patient compliance and is well accepted by them.9
Besides the positive changes produced by the PFD,
there are also premolar and canine mesialization and
Department of Orthodontics, Bauru Dental School, University of S~ao Paulo,
Bauru, Brazil.
All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported.
Address correspondence to: Guilherme Janson, Department of Orthodontics,
Bauru Dental School, University of S~ao Paulo, Alameda Octavio Pinheiro Brisolla
9-75, Bauru, 17012-901, Brazil; e-mail, [email protected].
Submitted, August 2018; revised and accepted, August 2019.
0889-5406/$36.00
Ó 2020 by the American Association of Orthodontists. All rights reserved.
https://doi.org/10.1016/j.ajodo.2019.08.017
incisor protrusion as side effects.10,11 Consequently,
55%-70% of the space obtained is provided by molar distalization, whereas 30%-45% results from anchorage
loss.11
Adequate transverse dimension is a fundamental
component of an adequate and stable occlusion.12 The
PFD has shown to be an effective appliance that promotes sagittal, transverse, and vertical maxillary arch
changes.12-19 The PFD showed relative stability when
evaluated by the peer assessment rating index.6,20,21
Transverse relapse is a usual occurrence, usually
caused by archwire shapes used in conventional edgewise techniques, which decrease the intercanine
width.22-24 Many distalization treatments show that
relapses come from accentuated molar distal crown
angulation, which is shown in lateral headfilms and
panoramic radiographs.20,21
Previous articles investigated the relationship between transverse relapse and patient's age and gender,
malocclusion, growth pattern, and dental intercuspation, during treatment with the pendulum appliance.
However, the measuring methods were not standardized.25-27 Consequently, it is difficult to compare the
results. The use of digital dental casts enables more
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Alessio Junior et al
358
accurate and comparable measurements.28,29 These previous studies also did not consider the possible influence
of fixed orthodontic therapy on the transverse dimension of the maxillary arch.
Therefore, the purpose of this study was to evaluate
the maxillary dental arch transverse changes and longterm stability of Class II malocclusion treatment
with the pendulum, followed by fixed orthodontic
appliances.
MATERIAL AND METHODS
This longitudinal study was approved by the Ethics in
Research Committee at the Department of Orthodontics,
Bauru Dental School, University of S~ao Paulo.
A pilot study was conducted with 5 patients to allow
sample size calculation. The mean intersecond molar
transverse relapse obtained in the pilot study, which
was 2.5 mm, was taken as a parameter. Therefore, to
detect a minimum difference of 2.5 mm in intersecond
molar transverse relapse, with an alpha of 0.05 and
80% of test power, 20 subjects were needed in each
group.
Written informed consent was obtained from all subjects. The inclusion criteria for the dental casts were (1)
initial Class II molar relationship and Class I molar relationship with 2 mm overcorrection at the end of treatment with the PFD, followed by edgewise appliances;
(2) no deciduous teeth present; (3) 5-year follow-up records after the end of treatment; and (4) plaster models
in good condition, with no blisters, fractures, or wear, in
the 4 evaluated stages.
Therefore, all patients previously treated with the
pendulum fixed appliance, followed-up on for more
than 5 years, and with adequate orthodontic records
were selected. As a result, the sample comprised 80
maxillary 3-dimensional dental casts of 20 patients (14
female and 6 male) with a mean age of 12.5 years (range,
11-14 years) selected from the files of the Department of
Orthodontics, Bauru Dental School, University of S~ao
Paulo.
Initially, the patients were treated by the PFD, and its
coils were activated by a 60 distal bend, providing a distal
253 g of force per side, for 5 months (Fig 1).9,10,30
Immediately after distalizer removal, a Nance button
was used as anchorage to avoid mesial movement of the
molars. In addition, a cervical extraoral appliance was inserted with no expansion in the inner bow to maintain the
arch transverse and anteroposterior dimensions and to upright the first molars. It was used during the sleeping
hours, with 400 g of force on each side for an average of
4 months, until the fixed appliances were installed and
leveling and alignment reached a rectangular stainless
September 2020 Vol 158 Issue 3
Fig 1. Pendulum distalizer appliance.
steel archwire. No further distalization was produced by
the extraoral appliances.
After 5 months of distalization, treatment was
continued by the bonding of 0.022 3 0.028-inch preadjusted edgewise fixed orthodontic appliances. Leveling
and alignment were performed with the conventional
wire sequence until a 0.019 3 0.025-inch rectangular
stainless steel archwire was used for maxillary premolar
and canine retraction.
Subsequently, the Nance button was removed to
allow anterior retraction, and the extraoral appliance
was replaced by Class II elastics, recommended to be
used for 20 hours/day. After closing the spaces, finishing
procedures were undertaken.
After the end of treatment, a Hawley retainer was
used in the maxillary arch, and a fixed canine-tocanine retainer was bonded in the mandibular arch.
The Hawley retainer was recommended to be used
full-time for 6 months, followed by nights-only use for
6 months. The mandibular canine-to-canine bonded
fixed retainer was recommended to be used for a mean
period of 3 years.
Four pairs of dental casts of each patient were digitized at the following stages: pretreatment (T1), after
distalization with the PFD (T2), posttreatment (T3),
and at 5-year follow-up (T4). Only the maxillary dental
casts were used in this investigation. The dental casts
were scanned with the Rexcan DS2 scanner (Solutionix,
Seoul, South Korea).
Landmarks were identified on the maxillary dental
cast of each patient, which allowed the measurement
of several transverse variables (Fig 2). These variables
were measured with Geomagic Studio 5 (3D Systems,
Rock Hill, SC) software.
Twenty percent of the sample was randomly selected,
and the landmarks were again identified and the
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Table I. Results of the random and systematic errors
evaluation (n 5 20)
1a Measurement,
Variables
mm
3-3
34.89 (1.33)
4-4
41.84 (2.62)
5-5
46.12 (3.29)
6-6
51.07 (3.67)
7-7
56.86 (2.89)
2a Measurement,
mm
Dahlberg P
35.08 (1.59)
0.184 0.448
41.87 (2.81)
0.079 0.755
46.34 (3.34)
0.077 0.951
51.16 (3.83)
0.054 0.859
57.06 (2.95)
0.111 0.935
3-3, intercanine distance; 4-4, interfirst premolar distance; 5-5, intersecond premolar distance; 6-6, intermolar distance; 7-7, intersecond molar distance.
Note. Values are mean (standard deviation).
Fig 2. Scanned maxillary dental cast showing the
measured transverse variables. A, intercanine distance—measured from right to left maxillary canine
cusp tips; B, interfirst premolar distance—measured
from right to left maxillary first premolar cusp tips; C, intersecond premolar distance—measured from right to left
maxillary cusp tips; D, interfirst molar distance measured
from right to left maxillary mesiobuccal cusp tips; E, intersecond molar distance measured from right to left maxillary mesiobuccal cusp tips.
variables were remeasured by the same examiner
1 month after the first evaluation. The random errors
were calculated according to the Dahlberg31 formula,
S2 5 Sd2/2n, in which S2 is the error variance d is the difference between 2 determinations of the same variable,
and the systematic errors were estimated with dependent
t tests, at P \0.05.32
Statistical analysis
Kolmogorov-Smirnov tests were used to evaluate
normal distribution. All variables presented normal distributions. The changes between the 4 stages were evaluated with repeated measures ANOVA, followed by
Tukey tests. All statistical procedures were performed
with Statistica (version 7.0; Statsoft, Tulsa, Okla) at
P \0.05.
RESULTS
The random errors ranged from 0.054 (intermolar
distance) to 0.184 (intercanine distance) and were within
acceptable limits33,34 (Table I). There were no significant
systematic errors.
The intercanine distance did not show significant
treatment and posttreatment changes (Table II; Fig 3).
The interfirst premolar distance increased significantly
from T2 to T3 and did not show significant posttreatment changes. The intersecond premolar distance significantly increased from T1 to T3 and did not show
significant posttreatment changes. The interfirst and intersecond molar distances significantly increased from
T1 to T2, then significantly decreased from T2 to T3,
and did not show significant posttreatment changes.
DISCUSSION
There was no significant treatment and posttreatment intercanine distance changes as has been previously shown (Table II; Fig 3).6,14,15,17,35
Maxillary intercanine width usually does not show
significant treatment and posttreatment changes with
the pendulum appliance.36-39 Therefore, maintenance
of the initial intercanine distance may have contributed
to its stability.
There were no significant interfirst and intersecond
premolar distance increases after the distalization period
with the PFD (Table II; Fig 3). In contrast, other studies
reported increases of the interfirst and intersecond premolar distances because of side effects related to PFD
treatment, including buccal tipping of the maxillary premolars.4,6,14,15 The palatal button was effective in preventing these transverse increases, in this study, which
probably did not happen in the other studies.
However, there were significant increases in these
distances, from the beginning to the end of treatment
(Table II; Fig 3). Because the palatal button was removed
after distalization, there was less transverse control of
the premolars, which may have buccally moved during
retraction, which corroborates other studies.14,22,38,40-44
After that, these distances remained stable in the longterm posttreatment stage.
This increase in premolar transverse distance from
the beginning to the end of treatment is clinically relevant because as the premolars are distalized to a broader
section of the dental arch to correct the Class II
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Alessio Junior et al
360
Table II. Treatment and posttreatment changes
Region
3-3
4-4
5-5
6-6
7-7
T1, mm
34.10 (1.93)
40.41 (2.07)a
46.38 (2.41)a
50.74 (2.89)a
57.05 (2.64)a
T2, mm
34.20 (1.95)
40.89 (2.13)a
46.79 (2.38)ab
54.88 (2.89)b
60.71 (3.49)b
T3, mm
34.67 (1.83)
42.63 (1.72)b
47.56 (1.88)b
50.56 (2.11)a
58.83 (2.71)c
T4, mm
34.23 (1.91)
42.62 (1.96)b
47.36 (2.17)b
51.06 (2.44)a
58.61 (3.02)c
P
0.699
\0.001*
\0.001*
\0.001*
\0.001*
3-3, intercanine distance; 4-4, interfirst premolar distance; 5-5, intersecond premolar distance; 6-6, intermolar distance; 7-7, intersecond molar
distance.
Note. Values are mean (standard deviation). Comparisons were made using repeated measures ANOVA, followed by Tukey tests. Different letters in a
row represent statistically significant differences among time points.
*Statistically significant at P \0.05.
malocclusion, there has to be an increase in interpremolar distances.12,45 Because this increase was not produced by the PFD, it was most likely produced by the
coordinated leveling archwires.
The transverse interfirst and intersecond molar distances increased significantly after the distalization
period with the PFD, as a side-effect of the distalization
springs that have a buccal component of force (Table II;
Fig 3). The same behavior was reported previously by
Hilgers,6 and Gosh and Nanda,46 who also observed significant increases in interfirst and intersecond molar distances.
After treatment, the transverse distance between the
first molars significantly decreased to a value similar to
the pretreatment stage (Table II; Fig 3). The intersecond
molar distance also significantly decreased after treatment; nevertheless, it remained significantly greater
than in the pretreatment stage. This decrease in transverse interfirst and intersecond molar distances was
probably caused by the correction of the buccal movement by the fixed appliances. To correct Class II malocclusion by distalization, there is usually a significant
increase in the interfirst molar distance, which did not
occur from the beginning to the end of treatment in
this sample. Because the transverse interarch relationship
Fig 3. Overlapping of canines, premolars, and molars
transversal changes in the phases. T1 (blue), T2 (red),
T3 (green), and T4 (yellow).
September 2020 Vol 158 Issue 3
was good at the end of treatment, there may be some narrowing of the mandibular arch during treatment. This
possibility should be further investigated.
As mentioned previously, there were statistically and
clinically significant increases in interfirst and intersecond molar distances produced as side effects of the
PFD. In Class II malocclusion correction, these increases
are desirable because the teeth will move to a broader
section of the dental arch. However, at the end of treatment, these distances significantly decreased. This
finding did not produce any transverse problems
because it is likely that some narrowing of the mandibular arch also occurred, as described. Greater attention
has to be given to the transverse dimension to prevent
this.
The transverse interfirst and intersecond molar distances remained stable in the long-term posttreatment stage, as described in the literature.38,47,48
These transverse changes corroborate with other
studies (Table II; Fig 3).14,24,38,40,42,44,45,49
Overall, treatment with the pendulum, followed by
with fixed appliances, does not change the maxillary intercanine distance and causes significant and permanent
increases in only the first and second premolar transverse
distances. Interfirst and intersecond molar transverse
distances increase immediately after the distalization
phase but return to similar original dimensions at the
end of treatment. After that, there is long-term stability
of the transverse dimensions. Therefore, changes in
transverse dimensions of the first molars are only clinically relevant during the distalization phase. The subsequent use of multibracket appliances will restore the
initial transverse dimensions. This knowledge may help
the clinician during treatment planning.
However, because of the reduced number of observations and the lack of evaluation of the mandibular arch,
these results must be regarded with caution. Besides,
there is also the limitation of a retrospective sample
and the potential bias of a convenience sample. Future
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Alessio Junior et al
studies with a greater number of patients and with
simultaneous analysis of the mandibular arch should
provide more reliable data.
CONCLUSIONS
1.
2.
The transverse changes observed during Class II
treatment with the pendulum appliance in conjunction with headgear and fixed appliances were temporary and not clinically significant.
After treatment, the transverse distances remained
stable in the long-term.
ACKNOWLEDGMENTS
The authors thank CAPES (Coordenaç~ao de Aperfeiçoamento de Pessoal de Nıvel Superior), financial code
001.
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