Avaliação da proporcionalidade da atividade elétrica dos músculos masseter e temporal em homens com bruxismo

Abstract

As an active part of the stomatognathic system, the muscles receive a great deal of attention and prominence, especially the temporal and masseter muscles, when it comes to chewing and the physiological repositioning of the jaw. Commonly, these functions cause fatigue and/or myalgia. As both muscles have the function of raising the jaw, the masseter is considered an agonist, while the temporalis in its anterior fibers is a synergist, acting with different work intensities. Bruxism is a relevant factor for the excessive work of the masseter and temporalis muscles. Thus, the objective of this study is to evaluate the proportionality of electrical activity, through electromyographic examination, of the masseter and temporal muscles in their anterior portion in men with already diagnosed bruxism. Ten male volunteers participated in this study, divided into two groups: G1 with non-bruxist volunteers (n=5) and G2 with bruxist volunteers (n=5). For both groups, muscle activity was recorded in three situations: 1) maximum habitual intercuspation (MIH), 2) chewing, and 3) rest. Electromyographic signals were collected using surface electrodes, recorded on a computerized electromyograph, and processed using specific software. All data were analyzed in relation to root mean square (RMS) values and subjected to statistical analysis using the Mann-Whitney test with p<0.05. The results indicated that, in situations of MIH and chewing, the anterior temporal muscle presented mean RMS values higher than those of the masseter in both groups, contrary to the initial hypothesis of masseter predominance as an agonist muscle. At rest, bruxist volunteers had mean masseter values approximately twice those recorded in the non-bruxist group, suggesting muscle hyperactivity associated with parafunctional behavior. Statistical analysis using the Mann-Whitney test revealed no statistically significant difference in any of the crossings evaluated (p>0.05). It is concluded that the electromyographic activity of the masseter was not proportionally higher than that of the anterior temporalis in the functional conditions evaluated, and that the small sample size, the use of self-reporting for bruxism classification, and the absence of distinction between centric and eccentric bruxism may have influenced the results, reinforcing the need for studies with larger samples and more precise diagnostic criteria.