Objective:To analyze the frontal aesthetic index of maxillary anterior teeth among individual normal occlusion in Shanxi province,and to explore the influence of gender,age,tooth form and face shape on the smile characteristics.Methods:A total of 322 participants with normal occlusion were recruited in this study from October 2022 to June 2023 in the Medical Examination Center,Affiliated People's Hospital,Shanxi Medical University.Participants were divided into 4 different age groups according to a class interval width of 10 years.Frontal images during their rest jaw position and standardized photographs of the maxillary anterior tooth were taken.Then the participants'classifications of facial shape and tooth form were recognized and recorded.The perceived size of the maxillary anterior teeth and the incisal steps between central incisors and lateral incisors or canines were measured by Image J software,then the width-length ratio(W/L)of the maxillary central incisor and the width ratio(W/W)of adjacent maxillary anterior teeth were calculated.Then different statistical methods were used to analyze the above issues.Results:W1/L1 was significantly lower in men[0.83(0.10)]than that in women[0.86(0.10)](P＜0.05).There was no statistically significant difference in the composition ratio of tooth form between genders(P＞0.05),and the W/L among tapered,ovoid,and square tooth form was different significantly[0.78(0.07),0.84(0.06),and 0.90(0.08),respectively](P＜0.001).Comparison between age groups showed that LI was significantly higher in the 40-49 years old group[(10.21±0.85)mm]than that in the 20-29 years old group[(9.84±0.76)mm]and the 30-39 years old group[(9.84±0.76)mm](P＜0.05).The incisal steps between maxillary central and lateral incisors or between maxillary central incisors and canines in women[0.92(0.60)and 1.32(1.00)mm,respectively]were significantly higher than those in men[0.80(0.60)and 1.08(1.50)mm,respectively](P＜0.05).The incisal steps between maxillary central and lateral incisors decreased gradually from the tapered face to the ovoid face and from the ovoid face to the square face[1.33(0.38)、0.81(0.23)、0.43(0.95)mm,respectively].For the incisal steps between maxillary central incisors and canines,the tapered face had the maximum incisal steps,followed by the ovoid and square faces[1.81(0.84)、1.17(0.87)、0.56(0.88)mm,respectively].Conclusion:The effect of gender difference needs to be considered in anterior aesthetic design,but the gender difference in the W/L ratio of maxillary anterior incisor are not related to different tooth forms.The perceived length of maxillary central incisor in normal occlusion aged 40-49 was significantly higher than that in aged 20-29 or 30-39.Gender differences and the influence of face shape type should be considered in the design of anterior incisal steps.
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