Differences in the Size and Morphology of Masseter Muscle and Mandible Assessed Using Three-Dimensional Computed Tomography.

Abstract

Background: Mandibular angular hypertrophy and hemifacial microsomia involve deformities in the mandibular region, resulting in facial asymmetry that severely affects patients' appearance. This study evaluated the masseter muscle-mandibular correlation in patients with hemifacial microsomia and those with mandibular angular hypertrophy using three-dimensional CT and compared them with normal individuals.

Methods: This study included 310 participants. Craniofacial scans were performed using three-dimensional CT in all participants to obtain masseter muscle and mandibular size and morphology data.

Results: In the normal population, there are sex differences in the shape and size of the masseter muscle and mandible, and the size of masseter muscle correlates with the mandible. In all three groups, there were differences in morphology and size of masseter muscle and mandible between the right and left sides (healthy and affected sides). Compared with the normal population, patients with hemifacial microsomia have a smaller masseter muscle and mandible on the affected side, while the healthy side is similar to the normal population. The measurement results significantly differed among patients with different severities of hemifacial microsomia and tended to worsen with increasing severity. In addition, the masseter muscle and mandibles on the left and right sides of patients with mandibular hypertrophy were larger than those of the normal population.

Conclusions: Three-dimensional CT proved reliable and accurate for measuring the masseter muscle and mandible size and morphology. We report masseter muscle and mandible characteristics in different populations. These findings can guide medical personnel in determining the diagnosis, treatment, and prognosis of these diseases.

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