Abstract
The influence of three-dimensional facial contour and dynamic evaluation decoding on factors of smile esthetics is essential for facial beauty improvement. However, the kinematic features of the facial smile contour and the contribution from the soft tissue and underlying skeleton are uncharted. Here, the cheekbone-maxilla contour and nasolabial fold were combined into a “smile contour” delineating the overall facial topography emerges prominently in smiling. We screened out the stable and unstable points on the smile contour using facial motion capture and curve fitting, before analyzing the correlation between soft tissue coordinates and hard tissue counterparts of the screened points. Our finding suggests that the mouth corner region was the most mobile area characterizing smile expression, while the other areas remained relatively stable. Therefore, the perioral area should be evaluated dynamically while the static assessment outcome of other parts of the smile contour contribute partially to their dynamic esthetics. Moreover, different from the end piece, morphologies of the zygomatic area and the superior part of the nasolabial crease were determined largely by the skeleton in rest, implying the latter can be altered by orthopedic or orthodontic correction and the former better improved by cosmetic procedures to improve the beauty of smile.
Highlights
Of deep, firm fibrous tissue that receives terminal muscle fibers from the levator labii superioris muscle and serves as the fibrous origin for the “fold muscles”[13,14]
Due to its social communicative value, facial smile evaluation has become a common concern of esthetic-related disciplines
Dynamic analysis of the smile commonly refers to the Facial Action Coding System (FACS)[23], which is anatomically based and describes minimal units of facial movement called Action Units (AUs) with descriptions of the resulting changes in facial appearance
Summary
Of deep, firm fibrous tissue that receives terminal muscle fibers from the levator labii superioris muscle and serves as the fibrous origin for the “fold muscles”[13,14]. We termed the combination of these two facial lines as “cheekbone-nasolabial contour” or “smile contour” and examined the relationship between this contour in space and the smile esthetics. This smile contour emerges more prominently when smiling, delineating the overall facial topography of different individuals. Stable points on the facial smile contour were identified by kinematic analysis during facial expressions. The aims of this study were to propose a promising indicator in clinic smile analysis, to determine kinematic features of the facial smile contour and to relate the underlying skeletal and soft tissue contributions to the facial smile contour in Chinese youth. This study will provide clues and hints for the treatment planning in clinic of orthodontics, orthopedic or plastic surgery when screening the determination areas and quantifying the modification volumes
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