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Brazilian Journal of Oral Sciences
Piracicaba Dental School - UNICAMP
EISSN: 1677-3225
Vol. 3, Num. 10, 2005, pp. 516-521

Brazilian Journal of Oral Sciences,Vol. 3, No. 10, July/September 2004, , pp. 516-521

Electromyographic study of patients with masticatory muscles disorders, physiotherapeutic treatment (massage)

Daniela A. Biasotto-Gonzalez1 Fausto Bérzin2

1PhD, Physical Therapy Course, University of Mogi das Cruzes, São Paulo, Brazil. 2DDS, PhD, Department of Morphology, Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil.

Correspondence to: Daniela A. Biasotto-Gonzalez Rua Caetano de Campos, 96 apto 41A 08717-630 Mogi das Cruzes-SP, Brazil Phone/Fax: 55 11 47265411 email: dani_atm@ig.com.br

Received for publication: March 23, 2004
Accepted: May 26, 2004

Code Number: os04027

Abstract

The temporomandibular joint disorder is characterized by pain and tenderness in the temporomandibular joint and in the masticatory muscles. Muscle hyperactivity can be of significant characteristic in subjects with Temporomandibular Disorders, which can be associated with pain and muscle fatigue. The aim of this study was to compare the electromyographic activity behavior of the major chewing muscles (anterior temporalis and masseter muscles) by using Parafilm material through analysis of the electromyographic signals before and after massage therapy. Sixty young adult female subjects, 17 to 27 years old, formed the total sample group. It was divided into twenty subjects with normal occlusion and no history of temporomandibular disorder, and forty subjects with signs and/or symptoms of TMD from parafunctional habits (excessively hard chewing or repeated forced mandibular opening and bruxism), which were then subdivided into twenty subjects who were submitted to physiotherapeutic treatment (massage), and twenty subjects who were not submitted to treatment. The masticatory activity was performed with the subjects comfortably sat, with the Frankfurt plane parallel to the floor. Electromyographic exams were carried out using bipolar surface differential electrodes positioned on the anterior body of the temporalis muscle and on the masseter muscles. The subjects were then instructed to bite bilaterally and simultaneously on the material. For the study of the masticatory activity the electromyographic signals were processed through rectification, linear envelope, and the coefficient of variation obtained from the procedure was comparatively analyzed. All the data collected was submitted for further analyzes of the variance. The study of the electromyographic signals of the masticatory activity in the isotonic contractions of the muscles in study was registered, stored, and analyzed by the RMS values (Root Mean Square). Moreover, the Analogue Visual Scale was utilized to assess the subject’s pain pre and post treatment. The results of this study indicated that the massage therapy decreased muscle hyperactivity, promoting better relaxation. Also, 87% of the subjects presented significant improvement of the TMD symptoms and sings. In general, this treatment is indicated as a complement of other treatment plans. The electromyographic exams are very important to analyze muscular activity; in addition, many authors agree that the common etiologic factor for TMD is the muscle hyperactivity. There is a substantial relationship between TMD and hyperactivity of the temporal muscle, and the physiotherapeutic treatment (massage) can reduce and eliminate pain and hyperactivity.

Key Words: electromyography (emg), physiotherapy, massage, bruxism, temporomandibular disorders.

Introduction

The temporomandibular disorder (TMD), also denominated Costen Syndrome, is characterize by several signs and symptoms such as temporomandibular joint (TMJ) pain, chronic headache, articular sounds during the condylar movements, restriction of mandible movements, humming, dizziness, and also local chronic pain along with sensibility and pain on the masticatory musculature, cervical region, and shoulder girdle1. The onset and intensity of these signs and symptoms may vary between the subjects.

In 1990 the American Academy of Orofacial Pain (AAOP) published the TMD classification, which is integrated with the International Headache Society medical diagnostic classification. Considering the fact that the majority of TMD classifications are not fully acknowledged as practicable, AAOP had an overall acceptance, and it is utilized nowadays as standard reference. Therefore, according to AAOP, TMD can be etiologically classified as arthrogenic, myogenic and mixed.

The etiology of the TMD is just as varied as its symptoms, considering that several factors can modify the dynamic balance of the masticatory system components. The most common etiologic agent regarding the myogenic TMD is the muscular hyperactivity2-6. This hyperactivity can contribute to internal disarrangements of the TMJ2,4,7-8.

The muscular hyperactivity can be triggered by malocclusion, postural changes, and emotional stress9. Furthermore, this hyperactivity can arise from traumas, systemic diseases, and growing disorders.

The electrical activity of the masticatory muscles in myogenic TMD subjects, associated with miofacial pain, was reported in 88% of the cases analyzed by the author, which was associated with the hyperactivity of an isolated muscle or in different types of combinations10.

One of the triggering factors related to pain and/or miofacial disorder are the mandibular parafunctions. Among these parafunctions, bruxism can be exalted6. According to these authors, muscular pain, malocclusion, articular degeneration, TMJ disk disarrangements, chronic headache, masseter hypertrophy, periodontitis and teeth wearing are the most common parafunction signs and symptoms.

Several treatment options are proposed to muscular disorder. Among others11-12, utilize the mouthguard (stabilize plate) as a therapeutic device to treat muscular disorders resulting from bruxism, with the goal of attaining relaxation of the masticatory musculature. However, only the first author utilize the stabilize mouthguard with a relaxation purpose, thus, not accomplishing the treatment. The second author recommended the mouthguard use only with the purpose of capturing EMG signals, disregarding the proposed objective of his study. This line of thinking can be seen in the majority of the researches (for example11,13) where this stabilize mouthguard is used only as an object of study during the gathering of the EMG signals, and not as a therapeutic aid.

Although massage is a technique that has been used for many years14, there are no scientific studies proving its effect, especially in TMDs.

Bell15 describes some techniques used in massotherapy such as sliding and kneading. However, there are no researches about the effects of such techniques in the TMJ, even though they are the most applied techniques in patients with TMJ disorders.

Recently, EMG allows us to measure the efficiency and the changes in muscular activity during a certain type of treatment, becoming a useful tool in the assessment of the treatment development process.

Nevertheless, the intent of this project is to assess the physiotherapeutic approach of massotherapy in miogenic TMD volunteers through the analysis of the electromyographic trace, comparing pre and post therapeutic bilaterally behavior of the masseter muscle and the anterior portion of the temporal muscle during the isotonic bilateral masticatory activity.

Material and Methods
Subjects

Primarily, a questionnaire was submitted to tree hundred and fifty two volunteers (310 women and 42 men) aged 17 to 27 years old. All the volunteers attended the University of Mogi of Cruzes (UMC) physical therapy course. Moreover, a selection was made according to the inclusion and exclusion criteria, which will be further described, and 84 volunteers were selected.

All of them were submitted to the EMG assessment, assembling a standard sample group, which excluded 24 volunteers. The 60 remaining volunteers, all women, were divided in three groups.

Group 1: 20 young women with normo-occlusion (class I Angle) and no history of temporomandibular disorder, regarding the inclusion criterion. They were submitted to the EMG exams, but not to the physiotherapeutic treatment.

Group 2: 20 young women with signs and/or symptoms of myogenic TMD related to bruxism or clenching, also regarded to the inclusion criterion. They were submitted to both EMG exams and massotherapy.

Group 3: 20 young women with signals and/or symptoms of myogenic TMD related to bruxism or clenching, respecting the inclusion criterion. They were submitted to EMG exams, but not to the massage therapy.

Criterion of Inclusion

The sample group was subdivided in 3 groups of 20 volunteers. The first group was made of female volunteers without TMD signs and/or symptoms, with normo-occlusion (class I - Angle), normal eletromiographic pattern of the masticatory muscles, and they were also asked to assume responsibility on the engagement of this research. The second and third group were also composed by women. They presented a diagnosis of TMD, with pain on the masticatory muscles during functional activities (talking and eating, mainly when eating hard food), with pain and/or muscle fatigue when waking up, with articular sounds (clicking), and mainly with bruxism, in a 6 months minimum period. They had also tried a therapeutic intervention in the past with no success regarding the relief of symptoms, which classifies it as a chronic onset of pain by the IASP.

Criterion of Exclusion

The individuals excluded from this study presented dental flaw, any dental orthotics or prosthetics, or they were participating in another physical therapy or odontological treatment at that moment. The other criterion for exclusion included the consent of not being responsible regarding the research, or the subjects presented a history of systemic disease such as arthritis, arthrosis, or diabetes, once these pathologies can alter the sinovial fluid, compromising the sinovial joints, including the temporomandibular joint. Futhermore, a criterion of exclusion from this research included the individuals who reported facial and TMJ traumas, articular luxation, decreased TMJ range of motion, male subjects older than 30 or younger than 17 years old, individuals using any analgesic or anti-inflammatory medication, and individuals with compromised EMG exam. To be excluded from the control group the subject had only to report a TMD sign and/or dysfunction, or participate in any other physical therapy and/ or odontological treatment at that moment.

It is of great value to highlight the importance of the EMG exam as a tool to include or exclude the volunteers in this research, because the subjects with muscle hyperactivity were classified in the miogenic TMD group, and the subjects with normal, or close to normal, EMG pattern (according12), which consist of less activity of the temporal muscle compared to the masseter muscles, were categorized in the normal group. Materials, Questionnaires, and Assessment Card

To achieve the goals of this research the following equipments were utilized:

  • Signal Conditioner Device, Lynx Eletronics Ltda, 16 channels, portable.
  • Sampler and A/D converter, 12 bites, model CAD 12/32, Lynx Eletronics Ltda.
  • Software Aqdados, version 5.0 - Lynx Electronics Ltda
  • PC Pentium I, with the Printer HP DeskJet, model 692C.
  • Differential active surface electrodes - Lynx Electronics Ltda.
  • Earth electrodes with water based gel.
  • Parafilm. Mâ.16
  • Procedure Latex Gloves - Satari
  • A questionnaire to select the volunteers presenting or not presenting temporoamandibular disorders.
  • Analogue Visual Scale - AVS.
  • Physiotherapeutic assessment chart.
  • Prestige Medical Stethoscope
Procedures

The goal of the study was explained to all the volunteers, and the formal consent of participation was also solicited to be filled. A questionnaire for subjects’ selection, and the AVS pain assessment were distributed in the same place, and they were applied without the examiner interference, so it would not create any expectancy in the volunteers that could lead to a bias result in the physical therapy assessment, which was later applied. The classification, or the clinical diagnostic index, was established just after the complete assessment of the patient. The physical therapy assessment included the subjective assessment, examination, palpation, assessment of the mandible active mobility, and the hearing of articular sounds. At last, the electromyographic exam was performed, which took place at the Electromyograph laboratory of University of Mogi das Cruzes (UMC) premises. At first, the volunteers with no signs of muscular hyperactivity were selected, followed by the volunteers with muscular hyperactivity signs, which were then placed in the second and third groups.

The collection of the electromyographic data started with the cleaning of the subject’s skin with cotton and 70% alcohol, followed by the proper placement of the differential active surface electrodes. The proper placement was made by following the orientation of the muscle fibers, along with the function test in each muscle in study, to avoid errors in the replacement of these active electrodes.

The electrodes were positioned in the body of the masseter muscle, and in the anterior portion of the temporal muscle, parallel to the muscle fibers, with its silver bars perpendicular to the fibers. This was made in order to maximize the caption and minimize the interference of noises, according to the FOP/ UNICAMP Electromyograph Laboratory protocol.

The electromyographic signal was captured in 2 different situations: (1) during the maintenance of mandible relaxed postural position, and (2) in masticatory activity non-habitual (isotonic).

During the non-habitual masticatory activity the subject placed the Parafilm Mâ16 material bilaterally between the premolars, first and second inferior and superior molars.

Therapeutic Protocol

After accomplishing the first steps of the research the group submitted to treatment, which included twenty subjects with muscular dysfunction, underwent 15 physiotherapeutic sessions for 30 minutes each, five times a week, using only the muscular relaxation technique through sliding and kneading massotherapy.

The sliding and kneading massage techniques were applied to the studied muscles with an orthopedic lotion (Ortocream, from Fisio-Line) for better slidings. Before starting each session, the therapist oriented the patient into performing deep thoraco-diaphragmatic breaths for the period of 1 minute. Moreover, the therapist warmed the region by using the sliding technique for 5 minutes, and only then the proposed treatment started.

The muscles to be worked with more intensity in this study were the muscles with higher EMG activity, along with a higher sensibility in the clinical assessment; therefore, each subject had her own individuality respected.

After finishing 15 sessions, the EMG data gathering protocol was repeated with all the patients participating in the research, which consisted in the 20 subjects who reported TMD and were not submitted to treatment, 20 subjects of the control group who were not submitted to therapeutic intervention as well, and the other 20 subjects who underwent treatment.

Visual Analogue Scales (VAS)

The Analogue Visual Scale17-18 was used and the sample group was divided according to the classification of the pre-selected groups.

In this research, the Analogue Visual Scale (AVS) was composed of a 10 centimeter horizontal line (without marks), presenting in its left end a painless information, and in its right end, the information regarding the worst pain ever. The volunteers were instructed to trace a vertical line above the horizontal scale line (without tracing over it), indicating in which point of the straight line the pain was. This procedure was performed with the same pen for all the volunteers. This assessment was taken after the first electromyographic exam, and immediately after the second exam for both groups, so the subjects would not see their first trace, and consequently be influenced by it.

Placement of the Electrodes

The skin above the muscles in study was cleaned with a cotton soaked in alcohol to reduce the electrical resistance of the skin. The electrodes were placed following the longitudinal lining and parallel to the direction of the muscle fibers, after a maximum intercuspation.

Electromyograph

To register the electromyographic signals, the channel was calibrated allowing a gain of 2000, with a cut frequency of 10Hz in the high passing filter, and 500Hz in the low passing filter attained through an analogical filter, Butterworth, with two terminals (poles) which presented an acquiring frequency of 1000Hz.

All the analogical signals were amplified and prepared to be digitized in conditioned modules of signals (MCS 1000V2. Lynx) with 16 analogical entries.

The volunteers were placed comfortably on a chair, with their back supported in the Frankfurt plane, parallel to the floor.

Their eyes were oriented forward (as looking to the infinite), feet on the floor, and arms supported on the inferior limbs. Following the data collection of each volunteer, they were guided and trained to masticate bilaterally and simultaneously. Practice section involved 10 masticatory cycles with 30 seconds rest in between each set.

The verbal command aimed to guide the volunteers to follow the rhythm registered by the metronome (60bpm).

The electromyographic traces of the masticatory activity were selected into parts, corresponding to the starting and end point of each isotonic contraction period, completing 10 masticatory cycles. After the selection of each trace in the masticatory period presented by the volunteer, they were submitted to two different procedures:

a) Processing of the trace signals referring to the masticatory activity using Matlab software (version 6.0).
b) Statistical analysis of univaried and multivaried variation of coefficients.

The periods of the electromyographic traces were collected aiming a further comparison and analysis, according19, which considers the study of the masticatory activity.

Results

Considering the data obtained and the statistical analysis performed in each studied group, we noticed that with the massage therapy technique applied on the Group 2, a significant result of decreased EMG activity of all the muscles in study was collected, as seen in Graphic 1 and 2, and in Figure 1.

Analogical Visual Sacale (VAS)

The results (Graphic 2) point out the difference (p=0,0026) between the AVS scores, which was taken before and after the treatment (analyzed by the ANOVA statistical test). There was a significant decrease in pain on the miogenic TMD subjects after they were submitted to the massage therapy treatment.

Discussion

The data collected in this study demonstrated that the massage therapy (sliding and kneading techniques) was efficient in decreasing the electrical activity of the hyperactive studied muscles, due to the bruxism.

Even though it is not possible to draw a comparison with the literature that deals with the effect of massage therapy in patients with bruxism due to the fact that there is no literature registers of this protocol, the results collected are in agreement with the classic literature concerning the massotherapy14-15,20, which supports the theory of promotion of increased blood and lynphatic circulation, favoring a muscular relaxation.

Most of the studies done in the past regarding this treatment tended to use the mouthguards as a therapeutic aid11-12,18. For this reason, the goals of this research done in volunteers presenting bruxism was to verify the effect of the physiotherapeutic treatment, utilizing the massage technique, considering the possible variation of the electromyographic signal during bilateral isotonic mastication.

The results showed that the massage technique (sliding and kneading) was useful to decrease the electric activity of the studied muscles, which were hyperactive because of the onset of bruxism presented by the subjects.

The results of this research, considering the experimental conditions in which it was conducted, lead us to these conclusions:

  1. There was an improvement in the volunteer’s symptoms.

  2. The decrease of the electromyographic activity in the studied muscles was significant in the sample groups submitted to treatment.

  3. There was evidence of efficiency in the use of massage therapy in the Myogenic Temporomandibular Disorder. The 15 sessions used for treatment attained the proposed objectives.

Based on the results, we can consider that the therapeutic protocol presented in this research can be added to other treatment plans, where they can achieve certain treatment goals as complements of each other, considering its own unique importance.

References

  1. 1. Dahlström L. Electromyographic studies of craniomandibular disorders: a review of the literature. J Oral Rehabil. 1989; 16: 1 20.
  2. Yemm R. A neurophysiological approach to the pathology and etiology of temporomandibular dysfunction. J Oral Rehabil. 1985; 12: 343-53.
  3. Ash MM. Current concepts in the etiology, diagnosis and treatment of TMJ and muscle dysfunction. J Oral Rehabil. 1986; 13: 1-20.
  4. Phillips RW, Hamilton AI, Jendresen MD, McHorris WH, Schallhorn RG. Report of the committee on scientific investigation of the American Academy of Restorative Dentistry. J Prosthet Dent. 1986; 55: 736-72.
  5. Okeson JP. Fundamentos de oclusão e desordens temporomandibulares. 2.ed. São Paulo: Artes Médicas; 1992.
  6. Steenks MH, De Wijer A. Disfunções da articulação temporomandibular do ponto de vista da fisioterapia e da odontologia. São Paulo: Santos; 1996. Moss RA, Garret JC. Temporomandibular joint dysfunction syndrome and myofascial pain syndrome: a critical review. J Oral Rehabil. 1984; 11: 3-28.
  7. Eversole LR, Machado L. Temporomandibular joint internal derangement and associated neuromuscular disorders. J Am Dent Assoc. 1985; 110: 69-79.
  8. Okeson JP. Dores odontogênicas. In: Okeson JP. Dores bucofaciais de Bell. 5.ed. São Paulo: Quintessense; 1998. Cap.11, p.235-58.
  9. Bérzin F. Estudo eletromiográfico da hiperatividade de músculos mastigatórios, em pacientes portadores de desordem crâniomandibular (DCM) com dor miofascial. In: Anais do 4º Simpósio Brasileiro e Encontro Internacional Sobre Dor. São Paulo; 1999.p.405.
  10. Abekura H, Kotani H, Tokuyama H, Hamada T. Effects of oclusal splints on the asymmetry of masticatory muscle activity during maximal clenching. J Oral Rehabil. 1995; 22: 747-52.
  11. Ferreira JAND. Efeito da placa estabilizadora do tipo Michigan sobre a atividade elétrica dos músculos temporal anterior e masseter de pacientes com hábito de bruxismo [dissertation]. Piracicaba: FOP/UNICAMP; 2001.
  12. Naeji M, Hansson TL. Short-term effect of the stabilization appliance on mastigatory muscle activity in mtogenous craniomandibular disorder patients. J Craniomandib Disord. 1991;5: 245-50.
  13. Beard G. History of massage technique. Phys Ther. 1952; 32: 613-24.
  14. Bell AJ. Massage and the physiotherapist. Phys Ther. 1964;50: 406-8.
  15. Biasotto DA. Estudo eletromiográfico dos músculos do sistema estomatognático durante a mastigação de diferentes materiais [dissertation]. Piracicaba: FOP/UNICAMP; 2000.Huskisson EC. Measurement of pain. Lancet. 1974; 2: 112
  16. Joyce CRB, Zutshi DW, Hrubes V, Mason RM. Comparison of fixed interval and visual analogue scales for rating chronic pain. Eur J Clin Pharmacol. 1975; 8: 415-20.
  17. Amadio AC, Duarte M. Fundamentos biomecânicos para análise do movimento. São Paulo: Editora Laboratório de Biomecânica EEFUSP; 1996. 162p.
  18. Nordschow M, Bierman W. Influence of manual massage on muscle relaxation: Effect on trunk flexion. Phys Ther. 1962; 42:653-6.

Copyright 2004 - Piracicaba Dental School - UNICAMP São Paulo - Brazil

 


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