RESUMO
Objective:To analyze and the smile line of Zhuang-Chinese youths.Methods:1 00 Zhuang volunteers aged 1 8-25 years were recruited for this study.The faces were individually registered by digital videography.The length and thickness of upper lips and mandibular incisor crown height appearance at rest,smile and laugh were recorded.Statistical analysis was performed using Mann-Whitney-U Test and non-parametric analysis.Results:The upper lip in men was longer than that in women at rest(P<0.05 ).The upper lip length increased and thickness decreased at smile and laugh in all subjects,in men was longer and thicker than in women(P<0.05),but there was no significant difference of upper lip thickness at rest between sexes(P<0.05).The mandibular anterior teeth,gingival papilla of all subjects were appeared at smile and laugh,there was no significant difference between sexes(P<0.05). Gingiva appearance at smile was in less than 1 0%of the subjects.39%subjects had high smile line,46%had average smile line and 1 5% had low smile line.Conclusion:Most of the Zhuang youths have moderate smile line,less high smile line and least low smile line.