Validity of Mid-facial Reference Planes for Evaluating Asymmetry of the Face

Abstract

Appropriate mid-facial reference planes for evaluating the facial asymmetry of patients with maxillofacial defects have not been established, although several methods for setting mid-facial planes have been reported. The aim of this study was to examine the validity of mid-facial planes for evaluating facial asymmetry by three-dimensional （3D） angular and linear measurement in six normal subjects' faces with a non-contact 3D-digitizer and 3D scanning software. Four mid-facial planes were defined based on medial angles of the eye （MAE）, lateral angles of the eye （LAE）, dorsum of the nose （DN）, and superimposed image of original and mirror image （SI）. Distances between 10 measurement points including three bilateral pairs and mid-facial planes, angles between three measurement lines and mid-facial planes, and asymmetry indices of three pairs of measurement points were calculated. The asymmetry index of the corner of the mouth to MAE was significantly higher than that to SI. There was no significant difference among the parameters to LAE, DN and SI. The results suggested that the LAE, DN and SI can be used as reliable reference mid-facial planes for evaluating facial asymmetry. Furthermore, it would be necessary to select an appropriate mid-facial reference plane depending on the available reference points and therapeutic purpose of individual clinical cases.