Estimated masticatory forces in patients before orthognathic surgery.

There has been relatively little study of masticatory forces in dentofacial deformity patients before orthognathic surgery. This study used a mathematical equation based on electromyographic activity (EMG) during mastication and forces obtained during isometric bites to estimate masticatory forces in 55 control subjects and 48 patients. Subjects chewed on a constant bolus while EMG recordings were made bilaterally from the superficial masseter, anterior temporalis, and posterior temporalis muscles. Unilateral isometric bite forces in the first molar position and simultaneous EMGs were recorded in these same subjects. Superficial masseter muscle activity and isometric bite forces were strongly correlated. The slope of masseter EMG versus isometric force was used to estimate the masticatory forces. Males were found to have significantly higher estimated masticatory forces than females.