Objective: To investigate the relationship between age, sex, length of upper lip and the exposure of maxillary central incisor. Methods: A total of 304 participants in normal occlusion (154 males, 150 females, aged 18-49 years) were recruited in this study from patients, visited the Medical Examination Center, Affiliated People's Hospital, Shanxi Medical University from January 2019 to August 2020. Participants were divided into 18-29 years old group (104, 53 males, 51 females), 30-39 years old group (110, 56 males, 54 females) and 40-49 years old group (90, 45 males, 45 females). Facial photography was used to record the facial state during the mandibular postural position, "che" pronunciation position and posed smile. The upper lip length, upper lip thickness and the exposure of maxillary central incisor were measured by ImageJ. The differences of measurement items in each group and the gender differences of each measurement item were analyzed. The length of upper lip and the exposure of upper central incisor in the mandibular postural position were analyzed by Pearson correlation. Results: In the mandibular postural position, the length of upper lip was (21.9±2.2), (22.5±2.5) and (23.1±2.2) mm in the 18-29 years old, 30-39 years old and 40-49 years old groups, and the length of upper lip in the 40-49 years old group was significantly larger than that in the 18-29 years old group (P<0.05). The exposure of upper central incisor in the 40-49 years old group during the mandibular postural position, "che" pronunciation position and posed smile [(1.4±1.2), (4.7±2.4), (7.7±2.4) mm, respectively] were significantly lower than those in the 18-29 years old group [(2.3±1.4), (5.5±2.2) and (8.8±2.0) mm] (P<0.05). The exposure of upper central incisor in the 30-39 years old group during the mandibular postural position and posed smile [(1.8±1.4), (8.2±2.0) mm, respectively] was significantly lower than those in the 18-29 years old group (P<0.05). With the increase of age, the exposure of upper central incisor decreased gradually. In the same group, the exposure of upper central incisor in the female during the mandibular postural position and "che" pronunciation position (except 40 to 49 years old group) were significantly larger than those in the male (P<0.05), and there was no statistically significant difference between the sexes in the posed smile (P>0.05). There was a significant linear correlation between the exposure of upper central incisor and the length of upper lip at the mandibular postural position in normal occlusion aged 18-49 (r=-0.325, P<0.01). Conclusions: Gender factor should be considered in the esthetic design of anterior teeth. The exposure of anterior teeth in the mandibular postural position and "che" pronunciation position is more valuable than that in the posed smile. The length of upper lip in normal occlusion aged 40-49 was significantly shorter than that aged 18-29, and the exposure of upper central incisors was significantly reduced.
目的： 探讨年龄、性别、上唇长度与上中切牙显露量的关系，为前牙美学设计提供参考。 方法： 从2019年1月至2020年8月于山西医科大学附属人民医院体检中心体检者中选择个别正常牙合者304名（男性154名、女性150名，18~49岁），按照年龄分为18~29岁组（104名，男性53名，女性51名）、30~39岁组（110名，男性56名，女性54名）、40~49岁组（90名，男性45名，女性45名），拍摄记录受试者下颌姿势位、发“che”音和姿势性微笑时的动态视频影像，并从中选择具代表性的3张面部图像，使用ImageJ软件，测量上唇长度和厚度以及上中切牙显露量。分析各测量项目的组间差异和性别差异，对下颌姿势位上唇长度和上中切牙显露量进行Pearson相关分析。 结果： 下颌姿势位时18~29岁组、30~39岁组、40~49岁组上唇长度分别为（21.9±2.2）、（22.5±2.5）、（23.1±2.2） mm，其中40~49岁组显著大于18~29岁组（P<0.05）。下颌姿势位、发“che”音时和姿势性微笑时40~49岁组上中切牙显露量［分别为（1.4±1.2）、（4.7±2.4）、（7.7±2.4） mm］均显著小于18~29岁组相应状态［分别为（2.3±1.4）、（5.5±2.2）、（8.8±2.0） mm］（P<0.05）。下颌姿势位和姿势性微笑时30~39岁组上中切牙显露量［分别为（1.8±1.4）、（8.2±2.0） mm］均显著小于18~29岁组相应状态（P<0.05）。随年龄增长，上中切牙显露量均逐渐减少；下颌姿势位和发“che”音时（除40~49岁组发“che”音时）各组女性上中切牙显露量均显著大于同组男性（P<0.05），而姿势性微笑时同组上中切牙显露量的性别差异无统计学意义（P>0.05）。18~49岁个别正常牙合下颌姿势位上中切牙显露量与上唇长度呈显著线性相关（r=-0.325，P<0.01）。 结论： 前牙美学修复设计时需考虑性别差异，下颌姿势位和发“che”音时上中切牙显露量较姿势性微笑时更有参考价值；40~49岁个别正常牙合上唇长度较18~29岁显著增加，上中切牙显露量显著减小。.