Diagnosis and Surgical Outcomes of Facial Asymmetry According to the Occlusal Cant and Menton Deviation

Abstract

PURPOSE: Morphologic differences and surgical outcomes were compared between the ipsilateral type of facial asymmetry, in which the menton deviates to the side of the upward frontal occlusal plane (FOP) cant (FOPUP), and the contralateral type, in which the menton deviates to the side of the downward FOP cant (FOPDOWN), by using cone beam computed tomography (CBCT) images.

MATERIALS AND METHODS: This retrospective study included consecutive patients with skeletal Class III malocclusion and facial asymmetry who had undergone bimaxillary orthognathic surgery and serial CBCT before, 1 month after, and 1 year after surgery. CBCT images were reconstructed and analyzed for predictor (group and timing) and outcome (CBCT measurements over time) variables. The data were analyzed using independent t tests and paired t tests.

RESULTS: The contralateral group (n = 12) was selected first; the ipsilateral group (n = 12) was selected by matching age, gender, and degree of FOP cant with those of the contralateral group. Before surgery, in the ipsilateral group, the ramal length was longer on the nondeviated (N-Dev) side than on the deviated (Dev) side (P < .05) whereas the mandibular body length showed no significant difference (P > .05). In the contralateral group, the ramal length was longer on the Dev side (P < .05) whereas the mandibular body length was longer on the N-Dev side (P < .01). One year after surgery, most measurements were corrected symmetrically in both groups (P > .05); however, the hemi-lower facial area remained asymmetrical in the contralateral group (P < .05).

CONCLUSIONS: Differences in ramal lengths in the ipsilateral group and mandibular body lengths in the contralateral group between the Dev and N-Dev sides seemed to be the main cause of facial asymmetry. Although facial asymmetry improved after surgery in both groups, asymmetry in the soft tissue remained in the contralateral group 1 year after surgery.