Electromyography study of trunk muscles in patients with temporomandibular disorders

ORIGINAL ARTICLE

STRINI, Paulinne Junqueira Silva Andresen ^[1], STRINI, Polyanne Junqueira Silva Andresen ^[2], SOUSA, Gilmar da Cunha ^[3], JÚNIOR, Roberto Bernardino ^[4], GORRERI, Marília Cavalheri ^[5], MACHADO, Naila Aparecida de Godoy ^[6], NETO, Alfredo Júlio Fernandes ^[7]

STRINI, Paulinne Junqueira Silva Andresen. Et al. Electromyography study of trunk muscles in patients with temporomandibular disorders. Multidisciplinary Scientific Journal Knowledge Nucleus. Year 04, Ed. 08, Vol. 05, pp. 35-49. August 2019. ISSN:2448-0959, Access link in: https://www.nucleodoconhecimento.com.br/health/electromyography-study

ABSTRACT

The human muscular system presents a set of structures acting in association and interacting between itself, reflecting clinically in the stomatognathic disorders and corporal position. Objective: This work aimed to evaluate the electromyography of trunk muscles before and after occlusal splint use, in patients with temporomandibular disorders. Materials and Methods: The electromyographic activity of the trapezius muscles, upper and middle parts, were evaluated at rest and in isometric extension of the scapula and of the head, and of the lumbar part of longissimus and iliocostalis muscles at rest and in isometric extension of the trunk, bilaterally. Electromyographic examinations were performed in 20 patients with temporomandibular disorders, before, one week and one month after occlusal splint installation. The root mean square values were compared by the Wilcoxon test (p<0.05). Results: The data showed statistically significant differences between the right and left sides for the longissimus and upper trapezius muscles, and between the times of treatment for the left iliocostalis, upper trapezius of both sides and right middle trapezius. Conclusions: It can be concluded that an interrelationship exists between occlusion and the cervical region, where any disequilibrium is capable of compromising distant muscle components and impairing the accomplishment of bodily functions.

Key words: Temporomandibular disorders, electromyography, occlusal splint, posture.

INTRODUCTION

The human body with its great complexity of components shows several interconnected structures working together and interacting with each other. Among them, the muscular system shows crucial interaction in maintaining posture and achievement of the many movements necessary for daily life.

The posture of each individual is determined by muscle chains, fascias, ligaments and bone structures that show continuity, are interdependent of each other, and together cover the entire body^3,31. In this context, the spinal column serves to maintain the body upright and acts as a complex system of forces and tension. The trunk muscles, including paraspinal, are important in body stability³⁷. Among them, the erector spinae muscle is responsible for the physical and functional integrity of the spine and a major anti-gravity force, predominantly working in a static or almost static manner during the day²².

Another important muscle for the functional balance of the head and shoulders is the trapezius. This is the most superficial of the back region of the cervical spine, with its fixation from the base of the skull to the shoulders down to the thoracic spine¹⁷, being essential for head stability. The structures of this region have links with the masticatory system and temporomandibular joint (TMJ). The stomatognathic system (SS), whose fundamental constituents include the TMJ, is a physiological functional entity, well defined and integrated by a heterogeneous set of organs and tissues, whose biology and pathophysiology are totally interdependent^26,31,34. An altered function in their components can manifest in the inter-related organs. Functional adjustments are activated throughout the SS and the body in general, which may or may not be compensated by the involved systems³⁴.

Postural changes affecting the column at any level can have an effect throughout its length, and these may interfere with temporomandibular complex function²⁴. Similarly, occlusal changes that can lead to alterations in jaw positioning, muscle hyperactivity or Temporomandibular Disorders (TMD) can influence the neck muscles and body posture. Therefore, the stance of the whole body can be altered by stomatognathic changes¹².

In the treatment of TMDs, occlusal appliances have aided in promoting changes in occlusal vertical dimension, eliminating malocclusion^2,8 and contributing to neuromuscular stability⁸. These appliances seem to contribute in muscle relaxation, combined with a relief of pain in most cases²⁹. The occlusal splints are a simple device, reversible and non-invasive²⁵, and are used in the diagnosis and treatment of TMDs^26,30, providing improvement in symptoms reported by patients²⁰. There are a many kinds of this device that can be used for TMD management and the splint that cover occlusal surfaces of tooth is the most common type²⁶.

In view of these muscle relations and postural chain associations, as well as in research related to the hyperactivity muscle disorder, electromyographic evaluations are an important resource, where they can help in the differential diagnosis and provide substantial data for inspection and management of occlusal therapy and the whole rehabilitation necessary for the recovery of physiological functions²¹.

In this work, electromyographic activity was determined for the trapezius muscle, upper (UP) and middle part (MP), and erector spinae, lumbar part of longissimus and iliocostal muscles, bilaterally, in patients with temporomandibular disorders, before and one week and one month after the installation of occlusal splints.

MATERIALS AND METHODS

SUBJECTS

For this study, 20 patients were selected, with clinically normal occlusion when examined in the habitual position and presenting signs and symptoms of temporomandibular disorders. There were 19 females (95%), with ages ranging from 17 to 43 years (28.4 ± 8.4), who were registered in the Program for Reception, Treatment and Monitoring of Patients with Temporomandibular Disorders and Orofacial Pain, Dental School, Federal University of Uberlândia (FOUFU), which was approved by the local ethics committee (number 423/06).

The patients were diagnosed with TMD by clinical examination done for capacity dentistry and with help of Clinical Index of Helkimo (1974)¹⁴. These patients had at least 20 functional teeth in the oral cavity^11,16 and showed signs and symptoms for a minimum period of 6 months with no prior occlusal treatment, how related by patients²³. The patients underwent a verbal interview and anamnesis with questions about their general state of health and the chief complaint that led them to seek specialized care.

OCCLUSAL SPLINT FABRICATION

In order to make the occlusal splint, alginate impressions (Alga Gel, Technew, PE, Brazil) were taken for the upper arch, and the occlusal splint was constructed in this study following the principles of Okeson²⁶ (2007). The upper model of each patient was vacuum-pressed in a clear acetate sheet of 2-mm thickness (Bio-art, SP, Brazil). After cutting the splint, it was rebased with colorless acrylic resin (Vipi Flash, Vipi, Toledo, Spain), first making an anterior stop and then rebasing all the occlusal surface, in centric relation, allowing the occlusal adjustment.

The patients were instructed to use it continuously in the first week and then only at night until completing a month of evaluation. An eletromyography (EMG) was done for understanding the muscular behavior and didn’t for diagnosis of TMD. The EMG was performed before using the occlusal device and in each return of patient, after one week and one month of device use²⁹. The appliances which separate the jaws alter postural positions of the jaws during their usage and in so doing possibly alleviate pain in other areas. They may result in the reduction or equilibration of EMG activity in tested regions of some muscles.

ELECTROMYOGRAPHY RECORDING

The electromyography equipment (EMG System of Brazil Ltda, Sao Jose dos Campos, Brazil), model 800C, for 8 channels, and 2 auxiliary channels, consisted of a signal conditioner with a band-pass filter (20-500Hz), an amplifier gain of 1000x and common mode rejection ratio (CMRR)> 120 dB. All data were processed using specific software for acquisition and analysis (AqData) and a battery-powered, 12-bit A/D signal converter, with an anti-smoothing sampling frequency of 1.0 kHz for each channel and input rate of 05 mV.

The silver chloride bipolar surface electrodes (Data Hominis Technology Ltda., Uberlandia, Brazil) used to record muscle activity have an active diameter of 1.0 cm, and each electrode pair was spaced with an approximate 1-cm inter-electrode distance. After skin preparation, the surface electrodes were placed bilaterally over each muscle studied with adhesive tape²⁸. For the reference electrode, a pair of forceps was placed on the patient’s wrist⁷ along with a layer of conductive gel (Renygel, Renylab, MG, Brazil).

We performed three sets of exercise for each movement³², with an interval of 30 s between each repetition and 1 min between each exchange of movement, to avoid muscle fatigue and allow recovery of muscle energy^27,36. For all tests, voice commands were used to signal the patient to begin muscle contraction.

For the upper part (UP) of the trapezius muscle, electrodes were placed 2 cm lateral to the spinous processes of the fourth cervical vertebra (C4)³³, bilaterally. The other electrodes were then applied on the middle part (MP) of trapezius in the center of the line between C7 vertebra and the acromion, on both sides^4,28,35. The C4 to C7 vertebrae have relatively prominent spinal processes, making them easily palpable. With the patient sitting and his head tilted slightly down, each vertebral process is easily identified¹⁸.

At this initial moment of electromyographic examination, the patient remained seated in a chair with no head support²⁸, without shoes and in a neutral position. The electromyographic recordings of the UP and MP muscles were made in rest position for 10 s and in the maximum voluntary isometric contraction (MVIC) for 5 s.

For lumbar part of the longissimus (L) and iliocostalis (I) muscles, both components of the erector spinae group, it is necessary to locate the lumbar vertebrae. The electrodes were positioned, bilaterally at the L1 level (first lumbar vertebrae), 2 cm lateral to the vertebra for the L muscle^7,35. For the I muscle, the electrodes were placed on both sides, 1 cm medial to an imaginary vertical line that links the posterior superior iliac spine to the 12th rib, at the L2 level³⁵.

The patient was instructed to lie down on a stretcher in a prone position, and the test was performed at rest for 10s, with arms hanging loose lateral to the body and for the MVIC, the test was carried out³⁵ for 5 s. The pelvis and legs were strapped to the examination table with 3 10-cm wide velcro belts around the ankles, knees and hips. In each EMG were used reference anatomical points for replacement of electrodes, minimizing the wrongs during data collection.

The electromyographic results were obtained by calculating the root mean square (RMS), expressed in microvolts, being that the first and last seconds of each test were discarded, allowing the time needed between the verbal command and the beginning of the activity. Thus, the RMS analysis was computed in a period of 8 s for the rest position and for 3 s for the MVIC. After obtained the RMS for each test, the average of the three repetitions was calculated and the data submitted a statistical analyses by wilcoxon test^1,36.

RESULTS

The main complaint reported by all (100%) patients, during the anamnesis, that which led them to seek specialized care was the presence of pain, showing an improvement in 55% of cases at the end of the study, how related by patients in anamnesis. In this research, also can be demonstrated the higher prevalence in women.

For electromyographic data evaluation involved the average of three repetitions of the longissimus and iliocostalis muscles at rest and with trunk extension, and the average of three repetitions for the trapezius muscles (UP and MP) at rest, scapula adduction and head extension. Electromyography was performed at the beginning, after one week and after one month of splint installation, comparing the right side with left side of each muscle between the stages of this research (Table 1) and comparing each side between the phases of the study (Table 2). Statistically significant differences were found in RMS values like indicated in tables 1 and 2.

Table 1. Comparison of mean RMS values for electromyographic data obtained for the left and right sides, considering all movements of all muscles.

p < 0.05

(*) statistically significant differences.

Table 2. Two-by-two comparison of mean RMS values using for electromyographic data obtained at the beginning, after one week and one month time points, considering the side of each muscle and movement done.

p < 0.05

(*) statistically significant differences.

DISCUSSION

The occlusal appliance used in this study contributed to improving the pain picture in most individuals by the end of the monitoring period, a finding that is consistent with Kovaleski & De Boever (1975)¹ and Okeson & Moody (1983)²⁵. A total elimination of these symptoms did not occur perhaps due to several factors, including the relatively short time of evaluation and the patient’s expectation and psychosomatic characteristics. In this way, the limitation of this work was the short time of evaluation. Another factor was the patient’s lack of awareness of the disorder during the entire period of the study, because no explanation was given about the involvement of dysfunction, guidelines, relaxation techniques, or any other form of intervention that could interfere in the evaluation of effect of the occlusal splint provided. Such information was supplied after the end of the study, and when necessary the patient was referred for other therapies. This precaution proved to be important in order to verify that only the occlusal appliance’s action on the muscles was studied.

The occlusal appliance used in this study is consistent with the technique advocated by Okeson²⁶ (2007) which has shown satisfactory results^5,6,9,15. The improvement in SS can also makes possible a reorganization at the cervical level with modify of the balance between the right and left muscles, with alteration of muscle hyperactivity, where the results were similar to those obtained by Pereira & Conti²⁹ (2000).

In the electromyographic data analysis in this study, there were statistically significant differences for the UP on the left side (UPL), UP on right side (UPR), when compared each side separated at rest and between the right and left side on the three movements performed, in each stage of this research. The alteration in electromyographic data in a cervical level can demonstrate an attempt of muscle reequilibration^13,15,21. This may be due to the clinical manifestation of TMD, which leads to modify activity of the masticatory muscles^8,10,27, and consequently, of the neck muscles.

The results of this work showed significant differences in the electromyographic activity of the MP on the right side, mostly when compared the data of the end of this work with another phases, for three movements done. This result after the period of device use may probably due to a lesser occlusal interference in the scapular and waist movements after inserting the appliance. As shown, occlusal changes promoted by the splint insertion can produce adjustments throughout all the masticatory system and adjacent structures. This fact is in line with Schinestsck & Schinestsck³⁴ (1998).

The left longissimus muscle showed statistically significant differences in electromyographic activities when compared with the right longissimus throughout the monitoring period. Also, significantly different electromyographic values were observed for the left iliocostalis, between the beginning and after one month of treatment at trunk extension. These observations may also be the result of the downward effect of the association of muscle chains³⁷, such that muscles have to alter their electrical activity during movements of effort to ensure body support. Thus, TMD patients promote a cascade reaction in the rest of the body with changes in different muscle groups²⁴.

Given that the changes studied and the effects caused by the change in occlusal condition and the elimination of occlusal interference can affect various components and body structures interconnected, it is essential that other research be addressed in order to seek a better understanding of the interaction between the TMD condition and adjacent organs associated with tissues located at a distance. Together, a multidisciplinary team working with different types of treatment can contribute to muscle restoration and posture in these patients.

CONCLUSIONS

In this work, can be concluded that an interrelationship may exist between occlusion and cervical region. According to the methodology and analysis of the results, it is possible to infer that body muscles suffer influence of occlusal modifications and may work together and harmoniously in performing life functions and any imbalance at some level, either in the stomatognathic system or tonic posture, can affect muscle components at a distance, highlighting the link between them. Changes in these muscle systems can cause clinically visible interferences and modify the performance of the structures involved.

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ACKNOWLEDGEMENT

Thanks for FAPEMIG to financial support (CDS 1359/05).

^[1] Professora Doutora de Anatomia Humana do Instituto de Ciências Biomédicas – ICBIM, da Universidade Federal de Uberlândia- UFU.

^[2] Professora Doutora de Anatomia Humana, da Unidade Acadêmica Especial de Ciências da Saúde – CISAU, Curso de Medicina, da Universidade Federal de Goiás – UFG.

^[3] Professor Doutor do Instituto de Ciências Biomédicas – ICBIM, da Universidade Federal de Uberlândia – UFU.

^[4] Professor Doutor do Instituto de Ciências Biomédicas – ICBIM, da Universidade Federal de Uberlândia – UFU.

^[5] Professora Mestre do Centro Universitário de Patos de Minas.

^[6] Professora Doutora da Faculdade de Odontologia, da Universidade Federal de Uberlândia – UFU.

^[7] Professor Doutor da Faculdade de Odontologia, da Universidade Federal de Uberlândia – UFU.

Enviado: Abril, 2019.

Aprovado: Agosto, 2019.