The European Journal of Orthodontics Advance Access published January 6, 2011

European Journal of Orthodontics 1 of 6
doi:10.1093/ejo/cjq169© The Author 2011. Published by Oxford University Press on behalf of the European Orthodontic Society.
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Influence of Pre-Orthodontic Trainer treatment on the perioral
and masticatory muscles in patients with Class II division
1 malocclusion
Tancan Uysal*,**, Ahmet Yagci*, Sadik Kara*** and Sukru Okkesim****Department of Orthodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey, **Department ofOrthodontics, College of Dentistry, King Saud University, Riyadh, Saudi Arabia and ***Institute of Biomedical
Engineering, Fatih University, Istanbul, Turkey
Correspondence to: Dr Tancan Uysal, Erciyes Universitesi, Dis Hekimligi Fakultesi, Ortodonti AD, Melikgazi, Kayseri
38039, Turkey. E-mail: tancanuysal@yahoo.com
SUMMARY The

Introduction
The influence of myofunctional habits like abnormal lip andtongue function on craniofacial development andorthodontic problems has been regularly reported inpublications. Various appliances have been used for thetreatment of this problem (Walpole Day et al., 1949;
Massler, 1952; Tallgren et al., 1998; Schievano et al., 1999;
Quadrelli et al., 2001, 2002; Usumez et al., 2004). The
main reason for using myofunctional appliances has been to
establish muscular balance, eliminate oral dysfunction, andcorrect or reduce maxillary incisor protrusion/proclination(Tallgren et al., 1998). The growth and development of
craniofacial structures and the influence of the perioral
muscles on the position of teeth have been discussed very
extensively, but many questions are still unanswered,notably with regard to muscular behaviour during various
orthodontic treatment methods (Stavridi and Ahlgren,1992).
The clinical use of electromyography (EMG) for
orthodontic diagnosis and for treatment planning has beensuggested (Grossman et al., 1961). The EMG was used toevaluate masticatory movements in children, with specialreference to occlusion (Ahlgren, 1966), and the actions ofmasticator muscles and association with facial morphology
were investigated (Möller, 1966). In both research andclinical studies, surface EMG has been utilized to aid in thedetection, diagnosis, and treatment of muscle hyperactivity
and hypoactivity, muscle imbalance, rest position, andspasm and fatigue of the muscles of mastication (Ahlgren
et al., 1985; Dahlström, 1989). Masticatory muscle activity
pattern was found to be different or highly associated withrespect to the age, malocclusion type, and type and stage oforthodontic treatment (Moss, 1975; Freeland, 1979; Leungand Hägg, 2001).
Myofunctional appliances have been used for many years(Tallgren et al., 1998; Schievano et al., 1999; Quadrelli
et al., 2001, 2002; Usumez et al., 2004) and have definite
place in orthodontics today. They are simple and economical,
but the cases need to be carefully selected, and the operator
needs to be well trained in their use (Usumez et al., 2004).
By starting the Class II orthopaedic treatment at earlyages and correcting the functional problems of soft tissues

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aim of this follow-up study was to evaluate the effects of Pre-Orthodontic Trainer(POT) appliance on the anterior temporal, mental, orbicularis oris, and masseter muscles throughelectromyography (EMG) evaluations in subjects with Class II division 1 malocclusion and incompetentlips. Twenty patients (mean age: 9.8 ± 2.2 years) with a Class II division 1 malocclusion were treatedwith POT (Myofunctional Research Co., Queensland, Australia). A group of 15 subjects (mean age: 9.2 ±0.9 years) with untreated Class II division 1 malocclusions was used as a control. EMG recordings oftreatment group were taken at the beginning and at the end of the POT therapy (mean treatment period:
7.43 ± 1.06 months). Follow-up records of the control group were taken after 8 months of the first records.
Recordings were taken during different oral functions: clenching, sucking, and swallowing. Statisticalanalyses were undertaken with Wilcoxon and Mann–Whitney U-tests. During the POT treatment, activityof anterior temporal, mental, and masseter muscles was decreased and orbicularis oris activity wasincreased during clenching and these differences were found statistically significant when compared
to control. Orbicularis oris activity during sucking was increased in the treatment group (P < 0.05). In
the control group, significant changes were determined for anterior temporal (P < 0.05) and masseter(P < 0.01) muscle at clenching and orbicularis oris (P < 0.05) muscle at swallowing during observation
period. Present findings indicated that treatment with POT appliance showed a positive influence on themasticatory and perioral musculature.

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T. UYSAL ET AL.

Subjects and methods
Subjects
This study was organized as a parallel group design with
one group receiving the experimental protocol and the otherserved as control. The power analysis was established by
G*Power Version 3.0.10 (Franz Faul Universität, Kiel,
Germany) software. Based on 1:1 ratio between groups,
total sample size of 35 patients would give 70 per centpower to detect significant differences with 0.30 effect size
and at a = 0.05 significance level.

Figure 1 Pre-Orthodontic Trainer appliance in situ.

This study was approved by the Ethical Committee on
Research of the Erciyes University Faculty of Dentistry.
The study included 40 subjects with skeletal Class II
division 1 malocclusions and incompetent lips. Lip
incompetence is defined as a resting lip separation of morethan 4 mm. The study included 40 subjects with incompetent
lip and lip separation ranged from 4.2 to 6.4 mm (mean: 5.1 ±1.1 mm).
Ten male and 15 female patients, treated between years
2006 and 2007, were selected as the treatment group.
Subjects in the treatment group were instructed to use the
POT every day for 1 hour and overnight while they slept.
Five non-cooperative patients (5 females) were excluded
from the study and the treatment group was consisted of 20
patients (10 males and 10 females). The ANB angles of all
patients were greater than 4 degrees, and their overjets weregreater than 4.5 mm (mean ANB: 5.62 ± 1.46 degrees andmean overjet: 6.0 ± 1.1 mm). None of the children in thetest or control group had a thumb-sucking habit. All were
Caucasian and their ages ranged from 7.8 to 11.5 years(mean age: 9.8 ± 2.2 years). All were treated exclusively
with the POT appliance (Myofunctional Research Co.,
Queensland, Australia).
The remaining samples formed the untreated control
group to eliminate possible growth and development effects.
This group consisted of six males and nine females thathave similar characteristics of Class II division 1
malocclusions (mean ANB: 5.23 ± 1.02 degrees and mean
overjet: 6.0 ± 1.5 mm). All were Caucasian with ages
ranging from 8.6 to 10.2 years (mean age: 9.2 ± 0.9 years).
The subjects in the control group were informed about twostage Class II orthodontic treatment but refused early
treatment.
Positioning of electrodes
The skin over the muscles was cleaned with alcohol. The
electrodes were filled with an electrode gel and attached tothe skin with adhesive washer to provide same impedance
during all EMG recordings. Therefore, the effect of the
impedance can be ignored because it is nearly same for all
recording section. The common ground electrodes wereadhered onto the forehead of the subject and the active
electrodes are placed on the muscles.
Bipolar silver/silver chloride disk surface electrodes
were placed over the right and left anterior temporal andsuperficial masseter muscles. The site on the anterior
temporal muscle was defined by palpation during clenchingof the mandible (Gay et al., 1994) and the electrodes wereplaced 1–1.5 cm from the anterior border of the muscle(Leung and Hägg, 2001). The electrode site on the superficial
masseter was defined as an area midway along a line
connecting the inferior border of the zygomatic arch at thezygomaticotemporal suture to the gonial angle. The
electrodes were placed centrally, about 1 cm distal to the

Downloaded from ejo.oxfordjournals.org at University of Manitoba on August 2, 2011and muscles, oral respiration and bruxism are need to bepart of the target (Gay et al., 1994). With this objective, ourattention was drawn to the Pre-Orthodontic Trainer (POT;
Figure 1) appliance, a myofunctional device usable inchildren from the age of 4–10 years. The POT is claimed tocorrect a skeletal Class II by an active mandibular force. By
separation of the lower lip from the dental alveolar arch, thePOT is claimed to prevent a malposition of the tongue andlower lip during swallowing, thus solving the associateddental open bite. Usumez et al. (2004) investigated thetreatment effects induced by a POT appliance on Class II
division 1 cases and compared these changes with anuntreated Class II division 1 control group. Those authors
reported that the POT induced basically dentoalveolarchanges that result in significant reduction of overjet andcould be used with appropriate patient selection.
The aim of this follow-up controlled study was to evaluate
the effects of POT on the anterior temporal, mental,
orbicularis oris, and masseter muscles during several oral
activities (swallowing, sucking, and clenching), throughEMG evaluations in Class II division 1 malocclusion
subjects with incompetent lips.

3 of 6EMG OF PRE-ORTHODONTIC TRAINER APPLIANCE

EMG recording
The EMG recordings are made at the initial stage of theappliance placement and at the end of the POT therapy(mean treatment period: 7.43 ± 1.06 months). EMG records
from the control sample were taken approximately 7–8
months later from the first records, similar to the treatmentgroup (mean observation period: 8.13 ± 2 months).
The EMG recordings were made of maximal clench incentric occlusion (four clenches), swallowing of saliva (twoswallows), and sucking on an empty straw (six suckings;
Tallgren et al., 1998). Each participant was informed of theresearch protocol prior to the first EMG recording session. They
were instructed to avoid protruding their jaw or tongue during
recordings. No visual feedback was provided to the subjects,
who were closely monitored during the recording procedure.
The swallowing recordings were made when the patient
indicated that a sufficient amount of saliva had accumulated.
To produce the sucking recordings, the patient was
instructed to suck on a plastic straw, keeping it in front of
the teeth and shield with one finger closing the open end of
the straw. During the recording procedure, the patient wasseated in a dental chair in an upright relaxed position withthe head unsupported and in its natural balance.
The EMG signal acquisition was conducted by
Biopac-MP150 unit (BIOPAC Systems Inc., Goleta,
California, USA). The EMG-100C Biopac was used as anamplifier with 2000 gain. Its high-pass filter was set to
1.0 Hz and low-pass filter was set to 500 Hz. The serial
output of EMG recorder device unit was sampled at 5000
samples/second and then sent to a PC via an Ethernet card.
EMG analysis
The power spectral density (PSD) is a function commonlyused for frequency domain analysis of surface EMG.

Analysis of the PSD can provide information about spatial
and temporal recruitment of motor unit (Blinowska et al.,1979). PSD of the surface EMG signals results from asummation of the spectral characteristics of the motor unit
action potentials. Therefore, maximum value of the PSD
was chosen as a parameter in order to evaluate the effects of
the POT. Maximum PSD value expresses amplitude of thelargest spectral line. EMG signals were recorded while themuscular activity was onset and PSD calculation that wasmade using Welch method was done for these signals.
Hanning window of 256 samples with an overlap of 128
samples are used in the Welch method. We made the spectral
estimate with Welch’s Method, which can be derived fromCheng and Lan (2003) and Kara et al. (2006).
Statistical analysis
All statistical analyses were performed using the Statistical
Package for Social Sciences (Windows, version 13.0; SPSS
Inc., Chicago, Illinois, USA). Arithmetic mean and standard
deviation (SD) were calculated for each measurement.
The Shapiro–Wilks normality test and the Levene’s
variance homogeneity test were applied to the EMG data.
The data showed non-normal distribution, and there was nohomogeneity of variances between the groups. Thus, thestatistical evaluation of EMG values between test groups
was performed using non-parametric tests
Wilcoxon test was used to test the significance of themean differences of the EMG variables between theobservation stages. To compare the mean differences of the
EMG variables for four investigated muscles during several
activities of the jaws and lips, Mann–Whitney U-test at the
95 per cent confidence interval (P < 0.05) was used.
Results
The EMG changes and statistically evaluations of thesamples at the pre- and post-treatment and pre- and postobservation periods and statistical comparisons of the meandifference of treatment and control groups are showed inTable 1.
Anterior temporal muscle
During the POT treatment, statistically significant difference
was only found in clenching activity (P < 0.001) for thismuscle (Table 1). EMG activity during clenching at the
beginning of the treatment was significantly higher than the
post-treatment activity. The control group’s EMG activity
during clenching was increased at the sixth month ofobservation (P < 0.05).
Treatment and control group comparisons showed thatstatistically significant differences were observed during
sucking (P < 0.05) and clenching (P < 0.001) activities.
During sucking, EMG activity was decreased in treatmentgroup and not changed in controls. However, during

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anterior border of the muscle and inter-electrode distancewas 20 mm and they have 4 mm recording diameter.
Electrodes for recording the orbicularis oris muscles
were placed symmetrically above and below the vermilion
border of the lips. The EMG signals for each patient are also
recorded from mentalis muscle. The position of theelectrodes at the first session was marked on each patient’s
chart, and the chart was used as a guide at each subsequent
recording session. Photographs were taken at the firstsession as reference for future electrode placement.
Additionally, EMG records were taken several same-day
repetitions (three times for each person) and used the meanvalues of these records instead of relying on only one
measuring interval.
The silver/silver chloride or Ag/AgCl electrode is manyelectrochemists’ reference electrode of choice. It is stableand quite robust (Watson and Yee, 1969). The electrodes
were filled with an electrode gel thus uniformity forelectrode impedance was provided.

Orbicularis oris muscle

0.195
0.036
0.739
0.910
−0.041
0.429−0.007−0.274−0.101
0.119
0.111
1.396
0.078
0.000
0.330
0.880
0.006
0.009
0.038
−0.155
0.027
0.081
0.002
0.800
0.071
0.001
0.460
0.038
0.056
0.009
0.052
0.052
0.023
0.083
0.008
0.524

Mean
difference

The effect of the treatment with POT during sucking andswallowing on the EMG activity of pre- and post-treatment
values are identical, as seen in Table 1. However, after using
the appliance for approximately 6 months, EMG values
during voluntary clenching was decreased and thisdifference was found statistically significant when compared
to control (P < 0.05). During the observation period, no
significant differences were determined in mental muscle
for all investigated activities in the control group.

NS
NS
*
NS
NS
NS
NS
*
NS
NS
NS
**
0.161
0.002
1.890
0.976
0.240
0.028
0.142
0.207
0.041
0.114
0.017
1.880
0.037
0.001
0.417
0.027
0.056
0.007
0.029
0.070
0.006
0.020
0.007
0.409
NS
NS
***
NS
NS
*
NS
*
**
NS
NS
**

Masseter muscle
All EMG values were decreased in the treatment andincreased in the control groups. However, statisticallysignificant changes were only determined during voluntary
clenching activity for both treatment and control groups (P< 0.01). Treatment and control group comparisons showedthat statistically significant differences were determined
during swallowing (P < 0.01), sucking (P < 0.01), andclenching (P < 0.001) activities.

0.015
0.001
0.099
0.017
0.088
0.133
0.030
0.103
0.013
0.003
0.013
0.079

NS, not significant. *P < 0.05; **P < 0.01; ***P < 0.001.

0.065
0.003
0.444
0.076
0.393
0.593
0.135
0.463
0.060
0.014
0.057
0.353
0.038
0.003
0.201
0.074
0.297
0.538
0.093
0.407
0.144
0.006
0.015
0.185
0.087
0.020
0.144
0.042
0.066
0.052
0.012
0.102
0.005
0.023
0.081
0.193
0.387
0.091
0.645
0.188
0.296
0.232
0.053
0.456
0.215
0.103
0.360
0.863
0.155
0.040
0.610
0.104
0.249
0.958
0.048
0.288
0.016
0.044
0.124
0.781
Anterior
Swallowing
tempoaralis Sucking
Clenching
Mentalis
Swallowing
Sucking
Clenching
Orbicularis Swallowing
oris
Sucking
Clenching
Masseter
Swallowing
Sucking
Clenching

Mean(dB/Hz)SD

SEM Mean(dB/Hz)SD

SEM−0.117−0.037−0.409−0.0300.047−0.420
0.045
0.119
0.128
−0.038−0.109−0.596

Difference(T2−T1)
Post-treatment
Pre-treatment

During the POT treatment, statistically significant
differences were found in sucking (P < 0.05) and clenching(P < 0.01) activities for orbicularis oris muscle. The EMG
values were increased in both sucking and clenchingactivities at the end of the treatment period. The control
group’s EMG activity during sucking was decreased at theend of observation and the difference was found statisticallysignificant (P < 0.05).
Intergroup comparisons showed that statistically significant
difference was observed during sucking (P < 0.05) activity.
The EMG activity was increased in treatment and decreased
in control group during sucking (P < 0.01).

0.255
0.002
1.660
0.138
0.203
0.033
0.188
0.186
0.083
0.298
0.030
1.890
0.131
0.002
1.500
0.096
0.202
0.027
0.104
0.252
0.209
0.072
0.026
1.480
0.083
0.002
1.560
0.096
0.233
0.019
0.104
0.362
0.014
0.033
0.015
1.080

SEM

SD
Mean
(dB/Hz)SD
Mean(dB/Hz)SEM

Difference(T2−T1)
Post-observation
Pre-observation
Wilcoxon
test

Control group (n = 15)
Trainer group (n = 20)
FunctionsMuscles

Mental muscle

NS
*
***
NS
NS
*
NS
**
NS
**
**
***

Mann–Whitney
U-Testclenching, EMG activity was decreased in treatment andincreased in control group.

Wilcoxon
test

Statistical comparison oftrainer and control group

T. UYSAL ET AL.

Discussion
This follow-up study of a sample of 40 subjects (25 subjects
for treatment and 15 for control group) with Class II division
1 malocclusion was designed to evaluate the EMG activityof treatment with the POT appliance. Five non-cooperative
patients were excluded from the study. The size of thesample may seem small but analysis undertaken to
determine sample size showed adequate power. Moreover, alongitudinal analysis is statistically much more sensitive
than an analysis of changes based on a cross-sectional
sample.
During treatment or observation period, the growthpotential of the masticatory and facial muscles that affectthe EMG should be taken into consideration (Möller, 1966;

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Table 1 The electromyography changes and statistically evaluations of the samples at the pre- and post-treatment and pre- and post-observation periods and statistical comparisonsof the mean difference of treatment and control groups. n, sample size; SD, standard deviation.

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EMG OF PRE-ORTHODONTIC TRAINER APPLIANCE

fat content may all affect the type and magnitude of signals
recorded (Schanne and Chaffin, 1970). Thus, subjects
with similar age, gender, dentoalveolar, and physicalcharacteristics were included to both study and control
groups.
In the current study, the effects of myofunctional
treatment on orofacial muscle activity were studied
from EMG recordings of three different oral functions:swallowing, sucking, and clenching. The reliability of the
EMG measurements of elevator and facial muscle activity
during various oral activities has been evaluated in previous
studies (Möller, 1966; Tallgren et al., 1998; Schievano
et al., 1999).
The marked anterior temporal activity changes during
maximal clenching, which averaged 0.409 mV during theinitial and 6 months stages, showed a significant decrease
after 6 months use of the POT. Tallgren et al. (1998) reported
similar changes during myofunctional appliance treatment
for anterior temporal muscle. Whether the decrease intemporal activity was influenced by the POT treatment or
possibly associated with occlusal changes related to thegrowth in the mixed dentition cannot be determined by thepresent data.
Stavridi and Ahlgren (1992) carried out an EMG study ofthe masseter, buccinator, and mentalis muscles to evaluate
the myofunctional changes that occur during orthodontic
treatment with functional appliances constructed withvestibular screen elements. During swallowing, they foundstatistically significant decrease in mental muscle activity
by EMG. Usumez et al. (2004) showed anterior rotation andsagittal growth of the mandible and increased lower incisor
proclination in patients with treated POT. These changes
may be effects the mentalis muscles position and activities.
In the current study, it was determined after POT treatmentthat lip pads decreased mentalis activity during clenching
but not changed during swallowing and sucking.
In the present research, we determined that POT
treatment increased orbicularis oris activity during
sucking and clenching, but it remained unchanged during
swallowing. Usumez et al. (2004) showed retroclinationof upper incisors and overjet reduction when patientstreated with POT appliance. Upper lip and orbicularis
oris muscles effects because of the retroclination of
upper incisors and these can cause increasing EMG
activity. Schievano et al. (1999) evaluated orbicularis
oris muscle before and after myofunctional therapy
and found that the electrical activity was increased
significantly at the 5 per cent level. This activity waswithin the normal range. They thought that myofunctional
therapy influenced perioral muscles because the muscular
activity requested to hold lips together decreased after
therapy. During the myofunctional appliance treatment,
Tallgren et al. (1998) determined significant decreases insucking activity of the lips observed at the 6 month and1 year stages. This finding indicated a decrease of the

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Ahlgren et al., 1985; Dahlström, 1989). The observed EMGchanges during treatment reflect the combined effects oftreatment and individuals’ growth and development. Ideally,a matched or at least comparable control group should be
included for identifying the changes due to the normal
growth (Usumez et al., 2004). Therefore, to eliminate
possible differences in growth pattern, a control groupconsisting of longitudinal data for untreated Class II division
1 malocclusion subjects was used in this study.
Similar to the therapeutic position used in activator
treatment, the POT appliance is constructed with themandible in a lightly anterior position for Class II patients(Usumez et al., 2004). For oral screen treatment, Graber(1979) reported that the construction bite cannot be as
protrusive as that with an activator and the appliance is ofvalue mainly in cases of mild Class II malocclusions.
A study concerning the POT appliances combined with thestraight wire system was published (Mahony, 2002).
Usumez et al. (2004) evaluated the effects of POT applianceon dentoskeletal structures by lateral cephalometry in agroup of Class II division 1 cases and determined nosignificant morphological changes by use of POT. A reviewof the literature presents no information on whether the
POT appliance can actually improve the EMG activity of apatient with Class II malocclusion or not. Although the useof myofunctional appliances such as the oral/vestibular
screen in the primary and mixed dentitions are mentioned in
the literature (Tallgren et al., 1998; Usumez et al., 2004);
only two studies have been published concerning the EMG
changes induced by these procedures in the early occlusal
developmental stages (Tallgren et al., 1998; Schievano
et al., 1999).
Masticatory muscles and facial soft tissues not only havean impact on bone growth but also influence the process oftreatment and stability of orthodontic treatment. The EMG
is the primary tool for the registration of these functional
processes and for the objective of growth modifyingpressure and traction effects on the skull (Eckardt et al.,1997). Therefore, appropriate application of non-invasive
EMG can provide more information about effect of thetreatment and usage of appliances, such as POT.
The EMG recordings are the measurements of theelectrical activity of muscles and not a measure of bite
force. The use of multiple electrodes permits maximum
voluntary isometric contraction recordings from groups ofmuscles but cannot be used to compare the relative forcesdeveloped by individual muscles nor is the data appropriate
for indicating whether a muscle is contracting isometricallyor isotonically (Leung and Hägg, 2001). The myofunctional
therapy acted on the musculature, posture, and functions.
Therefore, the muscular electrical activity request was
supposed to decrease during closure of the lips, which is thedesired posture during rest (Schievano et al., 1999).
During recordings, factors such as age, gender,
composition and shape of the face, connective tissue, and

5 of 66 of 6

Conclusion
The results from the present EMG follow-up study of asample with Class II division 1 malocclusion withincompetent lips indicated that treatment with POT
appliance showed a positive influence on the masticatory
and perioral musculature when compared to control.
Funding
The Scientific and Technological Research Council ofTurkey (contract number 106E144).
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Usumez S, Uysal T, Sari Z, Basciftci F A, Karaman A I, Guray E 2004 The
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Walpole Day A J, Trotter P A, Norris N 1949 A modified oral screen madeof latex. British Dental Journal 87: 143–147
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marked initial lip activity and may suggest a favourable
effect of the shield treatment.
In the literature, only few data were existing regarding to
the activity of masseter muscle during myofunctional
appliance treatment. Lower and upper incisors inclinations
changes and overjet reduction showed at the end of POT
treatment (Usumez et al., 2004). The number of teeth inocclusal contact influences the muscle activity during
chewing and biting (Ahlgren, 1966). In this study, all EMG
values of masseter muscle were decreased during thetreatment period and significant changes were observed
during clenching. Different from the present findings, nostatistically significant difference in EMG for massetermuscle during clenching by vestibular screen treatment wasdetermined (Stavridi and Ahlgren, 1992).
Ralston (1961) indicated that the recording electrodes
removing and replacing may entirely invalidate the EMG
results. Regional specialization and asynchronous activity
in measured muscles contribute further to the complexity of
EMG analyses. Consequently, we can say that all EMG
studies are flawed in one way or another. Yet EMG can help
quantify complex dynamic relationships and it can provide
a better understanding of muscles changes.

T. UYSAL ET AL.