Dynamic smile analysis: changes with age.

INTRODUCTION The objective of this study was to define age-related changes in the smile. The areas of interest were upper lip length at smile and repose, upper lip thickness at smile and repose, maxillary incisal display at smile, interlabial gap height at smile, smile index, percentage of buccal corridors, intercommissural width at rest, smile height, and smile arc. A secondary objective was to study the perioral changes from rest to smile and compare them on the basis of age. METHODS Video equipment was used to capture images of 261 subjects, who were divided into 5 groups by age. Two frames for each subject were selected, 1 frame representing the lips at rest and the other representing the widest smile. After 40 subjects were excluded, the data for the remaining 221 were analyzed by using 1-way analysis of variance (ANOVA) with the Fisher LSD post-hoc test. RESULTS There was a decrease of 1.5 to 2 mm in maxillary incisor display during smile with increasing age, but the smile index showed a significant increase. In accordance with some other studies, most subjects (78%) had average smile height. No subject in the 50 and over age group had a high smile, and no subject in the 15-to-19 year group had a low smile. All dynamic measurements indicated a pattern of decreasing change from rest to smile, especially evident after ages 30 to 39 years. CONCLUSIONS This study helps to establish age-related dynamic norms. As a person ages, the smile gets narrower vertically and wider transversely. The dynamic measures indicate that the muscles' ability to create a smile decreases with increasing age.