The labial aging process: a surface analysis-based three-dimensional evaluation

With increasing age, the smile becomes elongated and less appealing. Currently, several methods are proposed for analysis of lip morphology including lateral cephalograms, profile and frontal photographs, video images, and three-dimensional systems. Despite several descriptions of morphologic and histologic age-related changes in the literature, no scientific well-supported model of the labial aging process is reported.

For this study, 33 healthy volunteers were selected and divided into two groups according to age: a youthful group (ages 21-34 years) and an aged group (ages 45-65 years). Their dental and labial stone casts were obtained, digitized, and virtually reproduced using a computerized electromechanical digitizer and applying nonuniform rational B-spline geometry. To obtain a synthetic parameter describing local surface deformation, average curvature and curvature variability indexes were computed and compared.

No significant age- or sex-related differences in the average curvature were detected. In contrast, the curvature variability was significantly greater in the young than in the aged subjects.

The labial arch surface remains macroscopically constant between the third and the sixth decades of life, but with local modifications that influence the standard deviation of its curvature. A high standard deviation described the protruding labial appearance of the young subjects, whereas a reduced one described the flat lips of the aged subjects.

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