Relation between facial morphology on lateral skull radiographs and sEMG activity of head, neck, and trunk muscles in Caucasian adult females.

This study aimed to evaluate whether there is an association between facial morphology on cephalometrics and surface electromyographic (sEMG) recordings of the head, neck, and trunk muscles. Forty-seven Caucasian adult females, 18-29years of age (average: 24), underwent lateral skull radiographs in "natural head position", obtained by having the subject look at a small mirror at eye level, and sEMG recordings for the following muscles: masseter, anterior temporal, digastric, posterior cervicals, sternocleidomastoid, and upper and lower trapezius. All muscles were monitored bilaterally at mandibular rest position and during maximal voluntary clenching (MVC). The maximal bite force was also measured to check MVC. Pearson's correlation coefficient revealed significant correlations (p<0.01): (i) between the variables concerning mandibular position and size and the sEMG activity of upper trapezius at mandibular rest position; (ii) between the topographic correlation between the maxillary and mandibular bases (called skeletal class) and the sEMG activity of upper trapezius at MVC; (iii) between the sEMG activity of sternocleidomastoid and the Frankfort to mandibular plane angle; and (iv) between the sEMG activity of masseter and the anterior cranial base to mandibular plane angle. Some associations between the cephalometric variables and the sEMG activity of the head, neck, and trunk muscles were observed. No certain conclusion, however, was possible on the mechanism concerning these results. Future longitudinal studies are required.