| Objective:To analyze the data of upper lip length,upper lip thickness and upper central incisor exposure in normal occlusion in different age groups,at the same time to pose smile former dental esthetics qualitative index analysis.To investigate the relationship between age,gender,upper lip length and the exposure of maxillary central incisors,and to compare the gender differences in smile characteristics.Methods:A total of 304 participants in normal occlusion(154 males,143 females,aged 18-49years)were recruited for this study,who visited the Medical Examination Center.The researchers divided participants divided 18 to 29 years old group(104,53 males,51females),30 to 39 years old group(110,56 males,54 females)and 40 to 49 years old group(90,45 males,45 females).Subjects were placed in the upright position with their heads fixed,both eyes looking forward,and measuring scales fixed on their foreheads.Facial photography was used to record the facial state during the mandibular postural position,"che" position and posed smile.The upper lip length,upper lip thickness and the exposure of the upper central incisor were measured by Image J.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.140 young people(68 males and 72 females,average age 25.6 years)aged from 20 to30 years old ware selectedfrom the Medical Examination Center.The whole process of the posed smile position is recorded by video recording,and the image of the posed smile position is obtained by computer.Qualitative analysis was conducted on smile line,arc of the smile,curve of the upper lip,labiodental relationship of the lower lip and maxillary anterior teeth,and width of smile.We use Pearson chi-square test to analyze the smile index between gender groups.Spearman correlation analysis was used for qualitative index analysis of the esthetic smile.Results:1.The length of upper lip was(21.9±2.2),(22.5±2.5)and(23.1±2.2)mm in aged18～29,30～39 and 40～49 groups during the mandibular postural position.The exposure of upper central incisor in the 40～49 years old group during the mandibular postural position,"che" position and posed smile [(1.4±1.2),(4.7±2.4),(7.7±2.4)mm,respectively] was significantly lower than that in the 18～29 years old group [(2.3±1.4),(5.5±2.2)and(8.8±2.0)mm,respectively](P < 0.05).The exposure of upper central incisor in the 30～39years old group during the mandibular postural position and posed smile [(1.8±1.4)、(8.2±2.0)mm,respectively] was significantly lower than that 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" position(except 40 to 49 years old group)was significantly higher than that in the male(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).2.In the total sample,theaverage smile line(59.3%),consonant smile arc(71.4%),straightlip curvature(51.4%),no contact between the maxillary anterior teeth and the lower lip(72.9%)and tooth exposure the second premolar(54.3%)was relatively common.The verage smile line was associated with the labiodental relationship of the lower lip and maxillary anterior teeth,and the width of smile was associated with the labiodental relationship of the lower lip and maxillary anterior teeth(P<0.05).Conclusion:1.Gender difference should be considered in the aesthetic design of anterior teeth.The exposure of anterior teeth in the mandibular postural position and "che" position is more valuable than that in the posed smile.The length of upper lip in normal occlusion aged40～49 was significantly shorter than that aged 18～29,and the exposure of upper central incisors was significantly reduced.2.The average smile line,consonant smile arc,straight lip curvature,no contact between the maxillary anterior teeth and the lower lip and tooth exposure the second premolar were higher in the subjects.Gender based differences were statistically signifificant for the smile line and the contact relationship between the maxillary anterior teeth and the lower lip.a high smile was more common among females than in males,and females were more likely to have thelabiodental relationship with the maxillary anterior teeth covered by lower lip. |
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