Abstract: Objective: To investigate the changes of the perioral soft tissue in subjects at rest position and posed smile. Methods: 240 subjects with normal occlusion at the age of 15-49 were selected. The images were recorded and the perioral soft tissue were measured with the software of Smile Measure. Results: The analysis of pairwise comparison showed there were significant differences in the upper lip length at rest, upper lip length at smile, upper lip thickness at rest, upper lip thickness at smile, intercommissural width at rest, change in intercommissural width, maxillary incisal display, interlabial gap, smile index, and buccal corridors between each two groups. The analysis of two-sample t test showed there were significant differences in upper lip length at rest, upper lip length at smile, change in upper lip length, intercommissural width at rest between the male and female in the same group. The analysis of chisquare test showed there were significant differences between the smile height of male and female in G1,G2,G3,G4. Conclusion: With age increasing, upper lip length increased, the lip became more thinner, intercommissural became more wider and buccal corridors became more larger, and smile tended to be low smile. There were gender differences in lips and teeth relationship of subjects at the same age.

Key words: The perioral soft tissue , Smile, Age , Gender