A Simple and Quantitative Method for Three-Dimensional Measurement of Normal Smiles

Abstract

Smile reconstruction is one of the most challenging fields in plastic surgery. An understanding of the normal smile is essential in planning surgery for facial paralysis. The purpose of this study was to suggest a simple and quantitative method for the 3-dimensional analysis of smiles and to establish a basis for smile reconstruction in facial paralysis patients. The smiles of 50 volunteers (25 men and 25 women) were observed using a 6-mm digital video camera. Each subject had 10 points marked on the lips and nasolabial creases. Video editing programs were used to capture images of the resting and maximum smiles. The opacity of the image of maximum smile was adjusted and was merged with the resting image so that the migration of the points could be observed in 1 image. The migration distance (in millimeters) and the direction (in degrees) between each point were measured in frontal and both lateral views, and thus 3-dimensional vectors (x, y, z scalars) were obtained. The scalar values were converted to the values of a spherical coordinate system (distance, angle alpha and beta). Our work may offer a simple and quantitative method for measuring the smile and accurate guidance for reconstructive surgery.