Clinical Use of Qualitative Electromyography in the Evaluation of Jaw Muscle Function: A Practitioner's Guide

Selected muscle tone and asymmetry of the occlusal plane in case of intracapsular temporomandibular joint disorder

Objective: To discover the extent of the connection between occlusal plane asymmetry and the rest tone of the four muscle groups of the orofacial region with temporomandibular joint pathology.Methods: Eighty-seven subjects were divided into two groups. The following methods were applied: clinical examination, roentgenological examination, and electromyography. Data were evaluated and statistically analyzed.Results: The variability of occlusal plane inclination in relation to the porion plane was 0-4.6º.The tonus of masseter muscle was higher in the experimental group: 1.45 mV more than in the control group: 1.23 mV (p < 0.05).Conclusion: Asymmetry of the occlusal plane inclination was found for nearly all subjects in both groups. It can be compensated for by adaptation mechanisms and does not cause temporomandibular joint disorders. Undertaken research shows the existence of a proven correlation between TMJ disorders and the resting tonus of the masseter muscle.

Effects of Radial Extracorporeal Shock Wave Therapy in Reducing Pain in Patients with Temporomandibular Disorders: A Pilot Randomized Controlled Trial

Temporomandibular disorders (TMD) are primarily characterized by pain as well as issues concerning the proper functioning of individual elements of the stomatognathic system. The aim of the study was to assess the safety and efficacy of physical exercise, with or without radial Extracorporeal Shock Wave Therapy (rESWT), in patients with TMD. Eligible patients were adults (≥18 years) with diagnosed myofascial pain with or without mouth opening limitation (Group Ia, Ib) based on the Diagnostic Criteria for TMD (DC/TMD). Enrolled patients (n = 15) were randomly assigned 1:1 to receive physical exercise combined with rESWT (n = 8) or sham rESWT (n = 7) for four weeks. The primary endpoint was the pain intensity measured by a visual analogue scale (VAS). The secondary endpoints were muscle activity and function assessed through the surface electromyography evaluation of the anterior temporalis and the masseter muscles. The rESWT group (mean age: 28.50 ± 8.85 years) showed a statistically significant pain reduction (VAS Right side: ΔT0-T1 MD = −3.00; p = 0.023, Left side: ΔT0-T1, MD = 3.57, p = 0.021), whereas patients in the sham WBV group (mean age: 30.71 ± 8.98 years), did not reach statistical significance (VAS: Right side: ΔT0-T1 MD = 1.00, p = 0.155; Left side: ΔT0-T1 MD = 1.25 SE = 0.25, p = 0.094). Concurrently, muscle activity and performance significantly improved in the active rESWT group, with an improvement in the percentage of the overlapping coefficient (POC) compared to the control group. No dropouts and no side effects were recorded. Taken together, the findings of this pilot RCT suggested that rESWT combined with physical therapy could be effective in relieving pain and improving function in muscle-related TMD patients.

Kurtosis, a new variable with possible diagnostic value in analysis of jaw muscle surface EMG

BACKGROUND

There is a need for methods to compare differences of voltage levels and distribution anomalies in the study of skeletal muscle function. Calculating the kurtosis values has been found to be of value.

AIM

The aim was to record and analyse voltage and kurtosis levels of SEMG recorded bilaterally in the masseter and anterior temporalis areas during rest and clenching and to compare the kurtosis levels between controls and patients with TMJ disc dysfunction.

MATERIAL AND METHODS

Twenty-three healthy subjects and 21 patients with TMJ disc dysfunction were taken part in this study. Recordings were made with the BioPAK EMG System. Gain was adjusted to record the data within the range of ±2000 µV. SEMG was recorded in four facial areas, the right masseter, left masseter, right anterior temporalis, and left anterior temporalis areas. Kurtosis levels of SEMG, at clenching with maximal force, and mandibular rest, were compared between the control and patient groups.

RESULTS

The kurtosis levels of clenches were significantly higher in patients in all four areas with sensitivity, 38.1% to 61.9%, and specificity, 82.6% to 100.0%. No differences were found in kurtosis levels during mandibular rest.

CONCLUSION

The results support that kurtosis values of SEMG recorded during clenching have a potential diagnostic interest.

Is SEMG recorded "hyperactivity" during mandibular rest a sign of dysfunctional jaw muscle activity and temporomandibular disorders (TMD)?

BACKGROUND

Some authors state that above-normal surface electromyography (SEMG) levels during mandibular rest (MR) are a general sign of temporomandibular disorders (TMD).

OBJECTIVE

The aim was to compare SEMG levels in the masseter and anterior temporalis areas during MR between patients with disc displacement (DD) and subjects identified as healthy. The hypothesis was that average SEMG levels would be higher in the patients during MR before and after repeated clenches with maximal effort.

METHODS

Thirty-six healthy subjects, and 42 patients with DD, were included. SEMG levels were recorded bilaterally in the temporalis and masseter areas during MR before clenching and after repeated clenches with maximal effort. Multivariate analysis of variance (MANOVA) was used to compare the means of the log-transformed SEMG-values for the subject groups.

RESULTS

The mean MR levels in the four areas before clenching ranged from -0.19 log (µV) to 1.20 log(µV) in healthy subjects and from -0.22 log(µV) to 0.96 log(µV) in patients. The mean MR levels in the four areas after repeated clenches ranged from -0.19 log (µV) to 1.04 log(µV) in healthy subjects and from -0.27 log(µV) to 0.93 log(µV) in patients. The MANOVA test showed no significant differences in the means for MR for the four areas between the groups at the 5% significance level.

CONCLUSION

The hypothesis that jaw muscle SEMG levels during MR are on average generally higher in TMD patients is not supported. A possible explanation for the previous findings is that activity in other muscles was mislabelled as jaw muscle activity.

Stomatognathic function in Duchenne muscular dystrophy: a case-control study

AIM

This study aimed to analyse electromyographic activity, masticatory efficiency, muscle thickness, and bite force of individuals with Duchenne muscular dystrophy (DMD).

METHOD

Forty males aged 4-15 years, 20 with DMD and 20 healthy age-, height-, and weight-matched controls, underwent electromyography and ultrasonography of temporalis, masseter, and sternocleidomastoid muscles during postural control of the jaw, mastication, and maximal molar bite force.

RESULTS

The normalized electromyography signals showed higher activity in masseter and temporal muscles at rest, during protrusion, left and right laterality, and fatigue condition in the group with DMD than in the comparison group (p≤0.05). For masticatory efficiency of cycles, in analysis of non-habitual chewing of flavourless gum, and habitual chewing of peanuts and raisins, the group with DMD presented lower averages (p≤0.05). For the muscle thickness, the results showed that there was a lower muscle thickness in the group with DMD for all muscles during the rest and maximal voluntary contraction, except for masseter and sternocleidomastoid in the maximal voluntary contraction. In the maximal molar bite force, the group with DMD presented higher values for both sides than the comparison group (p≤0.05).

INTERPRETATION

Patients with DMD show muscle changes related to the stomatognathic system, in their activity, bite force, and muscle thickness.

Retracted: 'The effects of Duchenne muscular dystrophy on the performance of the stomatognathic system: case-control study', by Ferreira B., Da Silva G.P., Gonçalves C.R., et al

The above article, published online on 13 February 2015 in Wiley Online Library Early View (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal editors, Bernard Dan and Peter Rosenbaum, the MacKeith Press and John Wiley & Sons Ltd. The retraction has been made due to concerns relating to the validity of the EMG methodology and its interpretation, which affect the results of the paper. Reference Ferreira B, Da Silva GP, Gonçalves CR, Arnoni VW, Siéssere S, Semprini M, Verri ED, Chaves TC, Regalo SH. The effects of Duchenne muscular dystrophy on the performance of the stomatognathic system: case-control study. Developmental Medicine & Child Neurology 2015. doi:10.1111/dmcn.12707.

Assessment of cross-sectional thickness and activity of masseter, anterior temporalis and orbicularis oris muscles in oral submucous fibrosis patients and healthy controls: an ultrasonography and electromyography study

OBJECTIVES

Oral submucous fibrosis (OSMF) is an insidious chronic disease that is associated with significant functional morbidity and an increased risk for malignancy. It initially affects the lamina propria of the oral mucosa, and, as the disease progresses, it involves the submucosa and deeper tissue, including muscles of the oral cavity, resulting in loss of fibroelasticity. OSMF is a pre-malignant condition mainly caused by areca nut chewing. The aim of this study was to find out the involvement of muscles of mastication and facial expression in patients with OSMF by assessing the cross-sectional thickness and activity of the masseter, anterior temporalis and orbicularis oris muscles by ultrasonography and electromyography and comparing with healthy controls and also to find out any correlation between the ultrasonographic cross-sectional thicknesses of the masseter, anterior temporalis and orbicularis oris muscles with electromyographic activity.

METHODS

40 patients with OSMF were included in the study group, and the patients were divided into four groups on the basis of interincisal mouth opening, i.e. Group I (mouth opening >35 mm), Group II (mouth opening between 30 and 35 mm), Group III (mouth opening between 20 and 30 mm) and Group IV (mouth opening <20 mm). Ultrasonographic cross-sectional thickness and electromyographic activity (amplitude and duration) of the masseter, anterior temporalis and orbicualris oris muscles were recorded in patients with OSMF and 20 controls. Intergroup comparison of ultrasonographic cross-sectional thickness and activity (amplitude and duration) was done, and Pearson's correlation coefficient was applied to find out any relation between ultrasonographic and electromyographic findings.

RESULTS

Thickness and activity of the masseter muscle was significantly reduced in Group IV (mouth opening <20 mm) when compared with the control group. The anterior temporalis and orbicularis oris muscles remained unaffected. A positive correlation was observed between the thicknesses of the masseter muscle and the amplitude in Groups I, II and III; the anterior temporalis muscle in Group II and the control group; and the orbicularis oris muscle in Groups II, III and IV.

CONCLUSIONS

It was concluded that, among the muscles studied, there was an early involvement of the masseter muscle in patients with OSMF compared with that of other muscles.

Alterações no controle motor mandibular e cervical de crianças com paralisia cerebral

Objetivo: analisar a atividade elétrica dos músculos Temporal e Masseter e o padrão de postura e movimento de cabeça e mandíbula de crianças com Paralisia Cerebral (PC).Métodos: a amostra deste estudo compreendeu 32 voluntários com PC espástica e com Desenvolvimento Típico, com a faixa etária de 7 a 13 anos de idade, caracterizados com base na Classificação de Angle e Critério de Diagnóstico para Pesquisa das Disfunções Temporomandibulares (RDC/TMD). De forma simultânea, foram avaliadas a postura e movimentação da cabeça e mandíbula e a atividade elétrica dos músculos Temporal e Masseter por meio da cinemática e eletromiografia.Resultados: a PC não foi associada a presença de DTM ou com a alteração da oclusão dentária. No grupo PC, foi observada maior assimetria do músculo temporal (p<0.05), maior extensão da cabeça na máxima abertura da boca (p<0.05), maior amplitude de extensão da cabeça (p<0.01) e maior amplitude de projeção anterior da cabeça (p<0.05).Conclusão: a maior assimetria na atividade muscular, a maior extensão e projeção anterior da cabeça durante o ciclo mastigatório podem ser causas das desordens da função motora oral das crianças com PC.

Associação da atividade mastigatória com a função motora ampla, espasticidade e classificação topográfica na paralisia cerebral

OBJETIVO: verificar a existência de associação entre o grau de espasticidade, o nível de função motora ampla e a classificação topográfica de voluntários com PC com parâmetros de amplitude e tempo da ativação eletromiográfica dos músculos temporal (TA) e masseter (MA). MÉTODOS: a atividade muscular durante a tarefa de mastigação foi avaliada em quinze voluntários com PC. Os instrumentos clínicos utilizados foram: a Escala Modificada de Ashworth para espasticidade, o Sistema de Classificação de Função Motora Ampla (GMFCS) para função motora ampla. Foram analisados os parâmetros de simetria muscular e tempo do período ativo e inativo do ciclo mastigatório. RESULTADOS: durante o ciclo mastigatório observou-se associação entre o nível de função motora ampla e a simetria do MA, entre o maior grau de espasticidade e a diminuição do período inativo e aumento do período ativo e entre a classificação topográfica e a simetria do MA e do TA. CONCLUSÃO: a simetria e o tempo da atividade dos músculos TA e MA devem ser considerados durante a terapia da função motora oral na PC.

The neuromuscular approach towards interdisciplinary cooperation in medicine

BACKGROUND

The contemporary approach of dentistry towards interdisciplinary cooperation is based on the neuromuscular concept. In recent years many authors have pointed out a correlation between orthopaedic and dental findings. Furthermore, there is an intimate biomechanical interrelationship of occlusion with cerebral fluid circulation, left and right equilibrium, gaze stabilisation and headache. The influence of a dental occlusion and temporomandibular joint (TMJ) status on general health has been widely analysed in the current scientific literature.

AIM

The aim of this analytic study was to display the deep relationship between dentistry and other fields of medicine, and to show the necessity of wide cooperation between dentists and physicians.

CONCLUSIONS

This study was based on a review of 41 sources, including specialised articles and books. The significance of different anatomical and physiological preconditions (occlusion, muscles and TMJ status) was considered and evaluated separately. However, as a result of modern concepts of general body health, extending cooperation between different fields of medicine is essential. The practical application of the principles of neuromuscular dentistry enables one to increase greatly the treatment efficiency of aches in muscles, headaches, postural dysfunctions as well as of many other diseases. However, the dentist's contribution to the development of an interdisciplinary approach is underestimated. Many theoretical aspects of the interdisciplinary relationship have not been sufficiently examined, hence the practical consequences remain unclear. Further research in the field is urgently needed.

Electromyographic standardized indices in healthy Brazilian young adults and data reproducibility

The determination of normal parameters is an important procedure in the evaluation of the stomatognathic system. We used the surface electromyography standardization protocol described by Ferrario et al. (J Oral Rehabil. 2000;27:33-40, 2006;33:341) to determine reference values of the electromyographic standardized indices for the assessment of muscular symmetry (left and right side, percentage overlapping coefficient, POC), potential lateral displacing components (unbalanced contractile activities of contralateral masseter and temporalis muscles, TC), relative activity (most prevalent pair of masticatory muscles, ATTIV) and total activity (integrated areas of the electromyographic potentials over time, IMPACT) in healthy Brazilian young adults, and the relevant data reproducibility. Electromyography of the right and left masseter and temporalis muscles was performed during maximum teeth clenching in 20 healthy subjects (10 women and 10 men, mean age 23 years, s.d. 3), free from periodontal problems, temporomandibular disorders, oro-facial myofunctional disorder, and with full permanent dentition (28 teeth at least). Data reproducibility was computed for 75% of the sample. The values obtained were POC Temporal (88.11 +/- 1.45%), POC masseter (87.11 +/- 1.60%), TC (8.79 +/- 1.20%), ATTIV (-0.33 +/- 9.65%) and IMPACT (110.40 +/- 23.69 microV/microV.s %). There were no statistical differences between test and retest values (P > 0.05). The Technical Errors of Measurement (TEM) for 50% of subjects assessed during the same session were 1.5, 1.39, 1.06, 3.83 and 10.04. For 25% of the subjects assessed after a 6-month interval, the TEM were 0.80, 1.03, 0.73, 12.70 and 19.10. For all indices, there was good reproducibility. These electromyographic indices could be used in the assessment of patients with stomatognathic dysfunction.

Surface electromyography pattern of human swallowing

Background

The physiology of swallowing is characterized by a complex and coordinated activation of many stomatognathic, pharyngeal, and laryngeal muscles. Kinetics and electromyographic studies have widely investigated the pharyngeal and laryngeal pattern of deglutition in order to point out the differences between normal and dysphagic people. In the dental field, muscular activation during swallowing is believed to be the cause of malocclusion.

Despite the clinical importance given to spontaneous swallowing, few physiologic works have studied stomatognathic muscular activation and mandibular movement during spontaneous saliva swallowing.

The aim of our study was to investigate the activity patterns of the mandibular elevator muscles (masseter and anterior temporalis muscles), the submental muscles, and the neck muscles (sternocleidomastoid muscles) in healthy people during spontaneous swallowing of saliva and to relate the muscular activities to mandibular movement.

Methods

The spontaneous swallowing of saliva of 111 healthy individuals was analyzed using surface electromyography (SEMG) and a computerized kinesiography of mandibular movement.

Results

Fifty-seven of 111 patients swallowed without occlusal contact (SNOC) and 54 individuals had occlusal contact (SOC). The sternocleidomastoid muscles showed a slight, but constant activation during swallowing. The SEMG of the submental and sternocleidomastoid muscles showed no differences between the two groups. The SEMG of the anterior temporalis and masseter muscles showed significant differences (p < 0.0001). The duration of swallowing was significantly higher in the SNOC subjects. Gender and age were not related to electromyographic activation. Healthy SOC and SNOC behaved in different ways.

Conclusion

The data suggest that there is not a single "normal" or "typical" pattern for spontaneous saliva swallowing. The polygraph seemed a valuable, simple, non-invasive and reliable tool to study the physiology of swallowing.