Original Article |
Corresponding author: Vladimir Bogdanov ( vladbogdanov@yahoo.com ) © 2023 Vladimir Bogdanov, Miroslava Dinkova, Diana Tsakova.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Bogdanov V, Dinkova M, Tsakova D (2023) Effect of pre-orthodontic trainer treatment on the masticatory and perioral muscles in patients with class II subdivision 1 malocclusion evaluated by surface EMG. Folia Medica 65(5): 816-820. https://doi.org/10.3897/folmed.65.e94741
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Introduction: Myofunctional appliances have been shown to have a positive effect on the muscles in the facial area. Surface electromyography (sEMG) is one of the reliable methods used to investigate these effects.
Aim: The aim of this follow-up study is to evaluate the effect of a myofunctional appliance T4K on the perioral and masticatory muscles in patients with class II subdivision 1 malocclusion by sEMG.
Materials and methods: Sixteen children were treated with a Trainer appliance (T4K) for 9 months. The appliance should be worn every day for 1 hour and overnight. The EMG recordings were performed at the beginning and at the end of the Trainer therapy. The anterior temporal and masseter muscles were examined during maximal clenching. The orbicularis oris and mentalis muscles were examined during swallowing and sucking. Statistical analysis was performed using IBM SPSS Statistics version 23.0.
Results: The EMG values of the anterior temporal and masseter muscles during clenching increased significantly as a result of the treatment (p<0.05). At the end of the observation period, the EMG values of the mentalis muscle did not change during both sucking and swallowing (p>0.05), while the values of the orbicularis oris muscle increased significantly during sucking and swallowing (p<0.05).
Conclusions: As a result of the treatment with Trainer appliance, the EMG activity of the perioral and masticatory muscle significantly increased, while no change was observed in the electrical activity of the mentalis muscle.
facial muscles, myofunctional therapy, masticatory muscles, surface electromyography
Abnormal oral functions and their impact on craniofacial growth and morphology are widely studied. However, their effects on the growth of the mandible are still a subject of interest and controversy.[
Myofunctional appliances have been introduced into the dental practice to treat functional disorders and to reestablish muscle balance. One of the main goals of the interceptive treatment is correction of the abnormal activity of the lips, the mentalis muscle and the tongue. The main reason for using myofunctional appliances is to achieve muscular balance, eliminate oral dysfunction, and to reduce or correct maxillary muscle hyper- and hypoactivity.[
One of the widely used myofunctional appliances is T4K (Pre-Orthodontic Trainer, Myofunctional Research Co., Australia). It is a useful appliance for treating class II/1 malocclusions, which according to Class II/1 malocclusion is one of the most common malocclusions in clinical practice[
The aim of this study was to examine electromyographically the response of the masseter, anterior temporal, orbicularis oris, and mentalis muscles to the treatment with the T4K Pre-Orthodontic Trainer.
Sixteen patients (mean age, 10±1.4 years) were selected for treatment with the T4K Pre-Orthodontic Trainer First Phase (Myofunctional Research Co., Australia). The inclusion criterion was that the children should have class II/1 malocclusion. The main exclusion criteria were that the children had not previously received orthodontic treatment, did not have any temporomandibular disorders (TMD), and did not experience orofacial pain while clenching.
The children were instructed to wear the Т4К Pre-Orthodontic Trainer First Phase, for one hour during the daytime and at night while sleeping (Fig.
Surface EMG recordings were performed during three activities: maximal clenching, swallowing water taken in the mouth in advance, and sucking through a straw while the other end was closed with a finger. Each EMG recording lasted 3 seconds for every contraction except swallowing.
The surface EMG activity of the right and the left masseter and the anterior temporal muscle were recorded during maximal clenching for 3 seconds. The EMG recordings during swallowing and sucking through a straw were performed using bipolar electrodes positioned over the musculus orbicularis oris and musculus mentalis. The intervals between all muscle contractions were one minute. All activities were repeated three times. As these contractions are voluntary, we used the contraction with maximal value for the statistical analysis.
The patient sits in a dental chair with head unsupported and upright back. A two-channel electromyograph (Neuro-EMG-Micro-2) with Neuro-MEP-Ω software was used to perform the recordings. For each contraction, the appliance gives two values: maximal and mean value of the whole separate contraction. Before the recording, the skin above the examined muscles was cleaned with 70% alcohol and after drying up, silver/silver chloride bipolar electrodes were positioned. EMG recordings were performed at the beginning and at the end of the treatment (mean treatment period of 9.5±1.4 months).
The EMG recordings were made during maximal clench in centric occlusion, during swallowing water and during sucking through a straw. The patients made three attempts of every task. The activity of masseter and anterior temporalis muscles bilaterally were detected during maximal clench while the muscular activity of m. orbicularis oris and m. mentalis were tested during swallowing and sucking.
The statistical analysis was performed using IBM SPSS Statistics version 23.0. The nonparametric test of Kolmogorov-Smirnov was used to check the normality of distribution. The statistical evaluation of EMG values between the groups was performed by Mann-Whitney U-test with 95% confidence interval (p<0.05).
The EMG values of the pre- and post-treatment muscle activity are shown in Tables
Both the maximal and mean values of the muscle activity of m. temporalis and m. masseter showed statistically significant increase during clenching at the end of the observation period compared with the pretreatment values (p<0.05, p<0.02, respectively).
Table
The results showed that statistically significant differences during swallowing and sucking at the end of the treatment period were observed only in the orbicularis oris muscle. Both maximal and mean EMG values were increased (p<0.05). The EMG activity of the mental muscle did not change after Trainer application and the difference between the pre- and post-treatment values was insignificant.
EMG activity of masseter muscle and anterior temporalis muscle at maximal clenching. Maximal and mean values in µV before and after treatment
Muscle | Maximal values in µV | Mean values in µV | ||||
Before | After | p | Before | After | p | |
Masseter right | 929.56±451.6 | 1089.25±452.7 | <0.05 | 282.68±82.9 | 309.25±89.5 | <0.05 |
Masseter left | 1021.19±481.9 | 1303.75±570.6 | <0.05 | 303.75±101.9 | 359.68±107.52 | <0.05 |
Temporalis right | 1080.5±414.9 | 1358.31±380.8 | <0.05 | 314.06±72.56 | 362.0±62.5 | <0.05 |
Temporalis left | 1134.06±289.9 | 1415.56±325.30 | <0.02 | 317.43±60.2 | 360.43±69.6 | <0.02 |
EMG activity of orbicularis oris (OOM) and mentalis muscles (MM) during swallowing and during sucking through a straw. Maximal and mean values in µV before and after treatment
Muscle | Maximal values in µV | Mean values in µV | ||||
Before | After | p | Before | After | p | |
OOM swallowing | 714.93±335.9 | 965.31±525.3 | <0.05 | 225.61±56.9 | 266.25±81.1 | <0.05 |
OOM sucking | 786.93±353.3 | 965.18±490.6 | <0.05 | 262±62.5 | 294.18±80.4 | <0.05 |
MM swallowing | 739±224.9 | 883.9±363.7 | NS | 251.06±45.3 | 263.75±62.6 | NS |
MM sucking | 748.5±306.5 | 861±374.4 | NS | 251.06±62.9 | 272.88±83.8 | NS |
The aim of the study was to investigate the activity of the masticatory and perioral muscles as a result of a Trainer treatment.
The soft tissues, the masticatory and other facial muscles influence not only the bone growth, but also have an impact on the treatment results and stability after orthodontic treatment. The basic method to evaluate the changes of the muscle activity/function is electromyography[
In our study, we found that the activity of the anterior temporal and masseter muscles during voluntary maximal clenching significantly increased at the end of the observation period compared with the pre-treatment values. This is valid both for the maximal and mean values of the EMG activity. Early studies by Pancherz et al. reported that in patients with distal occlusion, the reduced activity of the masseter and temporal muscles after treatment with the activator and Herbst appliance gradually increased, approaching the values obtained with normal occlusion, which is compatible with the results of our study.[
During sucking through a straw with a closed opposite end, the results of the EMG recording showed a statistically significant increase in the muscular activity of the orbicularis oris muscle. During sucking, Uysal et al.[
We did not observe significant changes during sucking and swallowing in pre-and post-treatment values of the EMG activity of the mentalis muscle. Similar results reported Uysal et al.[
The results of the prospective study of T4K-treated patients showed significant changes of the muscle activity as detected via surface electromyography. No changes after treatment were observed in the mentalis muscle. The temporalis and masseter muscles, which keep the appliance in the mouth, and the orbicularis oris muscle, which is responsible for touching the lips together with the Trainer, increased their activity.