ABSTRACT
The purpose of this experiment was to look for signals of muscle fatigue in volunteers with Temporomandibular Disorders (TMD) during short period of mastication. Twenty female volunteers selected by Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) participated, 10 with myogenic TMD (experimental) and 10 clinically normal (control). The Masseter and Temporalis muscles were evaluated electromyographically with active differential surface electrodes. The masticatory activity was recorded for 15 seconds and the signals were normalized by 4 seconds of teeth clenching. Three complete masticatory cycles were taken to calculating the median frequency (MF) and electromyographic amplitude (RMS). The data were submitted to statistics analysis and non-parametric tests. The results showed that RMS and median frequency did not change during the mastication period analyzed, indicating the absence of muscle fatigue, for the Masseter and Temporalis muscles in both groups (p>0.05). These results confirm the absence of signals of muscle fatigue in masticatory muscles during short period of mastication even in individuals with TMD, possibly due to increased of blood flow, consequence of dynamic muscle contraction and the individual characteristics of muscle fiber composition and recruitment.
A proposta deste experimento foi procurar sinais de fadiga muscular em voluntarios com disfuncao temporomandibular (DTM) durante curto periodo de mastigacao. Vinte voluntarios do sexo feminino foram selecionados pelo Criterio de Diagnostico de Pesquisa para desordem tempomandibular, 10 com DTM miogenica (experimental) e 10 clinicamente normais (controle). Os musculos Masseter e Temporal foram avaliados eletromiograficamente com eletrodos diferenciais de superficie ativos. A atividade mastigatoria foi registrada por 15 segundos e os sinais foram normalizados por 4 segundos de apertamento dental. A frequencia mediana (FM) e da amplitude eletrmoigrafica (RMS) dos sinais eletromiograficos foram obtidos em 3 diferentes intervalos de tempo. Os valores da FM e RMS foram submetidos a analise estatistica descritiva e a testes nao parametricos. Os resultados demonstraram que o RMS e a FM nao mudaram durante o periodo de mastigacao, indicando ausencia de fatiga muscular para o musculo Masseter e Temporal, em ambos os grupos (p>0.05). Estes resultados confirmam a ausencia de sinais de fatiga muscular durante curto periodo de mastigacao, mesmo em individuos com DTM, possivelmente devido ao aumento do fluxo sanguineo em consequencia da dinamica de contracao muscular e das caracteristicas individuais da composicao das fibras musculares e do recrutamento.