Masticatory Muscle Activity in a Group of Thai Children with Skeletal and Dental Malocclusions: A Pilot Study Using Surface Electromyography.

OBJECTIVE

This pilot study aimed to investigate masseter muscle (MM) and anterior temporal muscle activity, symmetry, synergy, and effort in Thai children with skeletal and dental malocclusions.

MATERIALS AND

METHODS

Children aged 9 to 12 years were recruited (N = 38) and classified using lateral cephalometric analysis. Skeletal sagittal (Class I, II, or III), skeletal vertical (normal, deep, or open bite), and dental vertical (normal or deep bite) relationships of each child were examined. Surface electromyography of the MM and anterior temporal muscle was recorded during rest, maximum voluntary clenching (MVC), and chewing. Parameters evaluated included muscle activity amplitude, bilateral symmetry, ipsilateral synergy, and muscle effort.

STATISTICAL ANALYSIS: Data comparisons across dental vertical and skeletal classifications were assessed using an independent t-test or Mann-Whitney U-tests and a one-way ANOVA or Kruskal-Wallis H-test, respectively. Age and body mass index (BMI) were evaluated as covariates using an analysis of covariance. Statistical significance was defined at p < 0.05.

RESULTS

Significant differences in age and BMI, but not in the number of occlusal contact units, were observed among skeletal sagittal and dental vertical malocclusions. No significant intragroup difference in muscle activity, symmetry, synergy, or effort was detected across malocclusions at rest, during MVC, or during chewing. Specific pairwise comparisons with skeletal Class I group revealed significantly lower MM activity during chewing and greater MM symmetry during MVC in skeletal Classes III and II groups, respectively (p < 0.05). No significant difference in muscle parameters was found between normal and deep bite groups. After covariate adjustments, the intergroup findings remained broadly consistent.

CONCLUSION

Masticatory muscle activity in growing subjects with mixed dentition exhibited minimal variation across different skeletal and dental malocclusions. Skeletal Class II subjects without unilateral posterior crossbite had increased symmetry. While they may influence the children's masticatory muscle activity, age and BMI did not account for the notably reduced MM chewing activity in the skeletal Class III group.