Relationship of the thickness and electric activity of the masseter muscle with bite force: a morphological and electrophysiological study

ABSTRACT Purpose: to study the relationship between masseter muscle thickness and its electrical activity with the bite force. Methods: the study included 17 young adults (21.3 ( 1.4 years), 7 female and 10 male. All of them were healthy and clinically asymptomatic regarding temporomandibular disorders. The measurement of masseter muscle thickness was performed unilaterally during resting and maximal voluntary contraction. It was also quantified the bite force for each side with a force transducer positioned in the first molar region. Simultaneously, it was assessed the electrical activity of the masseter muscle during unilateral bite. The analysis was based on the comparison of samples, and used the Student's t-test, Wilcoxon, Mann-Whitney, and multivariate linear regression. Results: the masseter muscle thickness was greater in men than in women in both, resting and contraction state. We found symmetry between the sides of the muscles during resting and contraction. We couldn't find a statistically significant difference on the median frequency of the electromyographic signal in neither intra-individuals nor between genders, when masseter muscle is in maximal voluntary contraction state. We found higher bite force in males. It was not found a multivariate linear regression model between variables. Conclusion: results showed that we can't obtain a linear model with the studied variables, under the studied conditions.