Relationship between the morphologies of the masseter muscle and the ramus and occlusal force in patients with mandibular prognathism

Purpose: The purpose of this study was to examine the relationship between the morphologies of the masseter muscle and the ramus and occlusal force in patients with mandibular prognathism. Patients and Methods: The study group consisted of 71 patients with mandibular prognathism. They were divided into 2 groups, consisting of prognathism with or without symmetry, determined by frontal cephalogram analysis. All patients underwent 3-dimensional (3D) computed tomography (CT) and occlusal force was recorded with pressure-sensitive sheets. Results: in the cross-sectional area of masseter muscle, there were no significant differences between the right and left sides in the symmetry and asymmetry groups. In occlusal force, there was no significant difference between the symmetry and asymmetry groups. Occlusal force was not significantly correlated to the cross-sectional area of the ramus, but it was significantly positively correlated to the cross-sectional area of the masseter muscle (P <.05). Conclusion: occlusal force was associated with the ipsilateral cross-sectional area of masseter muscle in patients with prognathism; however, it was not associated significantly with the degree of mandibular deviation. (C) 2006 American Association of Oral and Maxillofacial Surgeons.