Hard and soft-tissue symmetry correlations in different facial aesthetic subunits: A retrospective study on Chinese young adults with normal occlusion

Abstract

Abstract Objectives The aim of this study was to describe facial symmetry based on aesthetic units in normal Chinese young adults. Correlations between symmetries of soft tissue units and underlying bone was also investigated. Materials and methods A retrospective study was conducted on 96 data sets which included spiral CT and facial stereophotogrammetry. A landmark independent symmetry measurement based on original-mirror alignment was performed. The full face was divided into 14 facial aesthetic units. The root mean square (RMS) of each soft and bony unit was compared by the Wilcoxon test. The correlation between RMS of soft tissue and its underlying bone was investigated by spearman correlation analysis. Results The RMS of the soft tissue units and bony units varied from 0.64 ± 0.37 mm to 1.25 ± 0.76 mm and from 0.76 ± 0.37 mm to 1.75 ± 1.04 mm, respectively. The symmetry correlation coefficient of soft and underlying bony structure varied from 0.216 to 0.684. The highest correlation was in the zygomatic region (0.684), while the lowest in the periocular region (from 0.216 to 0.331). Conclusions It was suggested that the normal face is slightly asymmetric, and the symmetry of soft tissue is in correlation with underlying bony structure. Clinical Relevance The traditional principle of aesthetics units was applied in this study which make evaluating the facial symmetry more accurately. Meanwhile, the correlation analysis of the symmetry of facial soft and hard tissue provides a reference data for maxillofacial plastic surgery.