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Objective: The aim of this study is to compare the short- and long-term reproducibility of verbal and nonverbal facial expressions of normal people using dynamic 3-dimensional (3-D) imaging. Design: Prospective, cross-sectional, controlled study. Setting: Peking University School and Hospital of Stomatology, Beijing, China. Patients and Participants: Twenty-seven participants, 12 males and 15 females, were recruited for this study. Methods: A 3-D dynamic system was applied to capture the process of 4 nonverbal facial expressions (smile lips closed, smile lips open, lip purse, cheek puff) and 2 verbal facial expressions (/i:/, /u:/) at an initial time point, 15 minutes later, and 1 week later. Key frames were selected from each expression recording sequence. Main Outcome Measures: The root mean square (RMS) between each key frame and its corresponding frame at rest was calculated. ΔRMS reflected the difference of the same key frames between the different sessions of the same expression of the same participant. The reproducibility of different facial expressions at different time intervals were analyzed. Results: There was no significant difference in verbal and nonverbal expression repeatability during a 15-minute interval, except for cheek puff motion. Following a 1-week interval, verbal expression repeatability was superior to that of nonverbal expressions ( P < .01). Compared with nonverbal expressions, the repeatability of verbal expressions did not obviously decrease with the increase in recording interval. Conclusions: Dynamic 3-D imaging is a useful technique for facial expression analysis. Verbal expressions showed greater reproducibility than nonverbal expressions.

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.

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