BACKGROUND A number of reference patterns such as the interincisal line, curve of the upper lip, width of the smile or shape of the teeth have been studied in different populations. Determining the frequency of different smile aesthetic parameters in a European Caucasian population and exploring possible gender differences is important in order to obtain predictable treatment outcomes. METHODS Photographs were obtained under resting and forced smiling conditions in 140 individuals (70 males and 70 females) with a mean age of 20.1 ± 4.3 years. Different variables were recorded, including the position of the maxillary interincisal midline in relation to the facial midline, the arc and width of the smile, and the shape of the teeth. The data were processed using the SPSS version 15.0 statistical package, with application of the chi-squared test and a confidence level of 95%. The statistical power was 80%, and the level of significance 5% (α = 0.05). RESULTS A total of 94.3% of the sample presented a maxillary interincisal midline coinciding with the facial midline, and 80% had a consonant smile line. The curve of the upper lip was upwards in 47.1% of the cases, followed by a straight curve in 41.4%. Most of the subjects (84.3%) presented a medium smile line with tooth exposure to the second premolar (61.4%). There were no significant differences between males and females. CONCLUSIONS The integration of aesthetic criteria is needed in order to guarantee satisfactory and predictable dental treatment outcomes. There were no statistically significant differences between males and females. The maxillary interincisal midline coincided with the facial midline, with a consonant smile arc and a medium smile line, upward lip curve and oval tooth shape.

中文翻译：

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上颌中线，上唇曲线，微笑线和牙齿形状的评估：对140名白种人患者的前瞻性研究。

背景技术已经在不同人群中研究了许多参考模式，例如门齿间线，上唇曲线，微笑宽度或牙齿形状。为了获得可预测的治疗效果，确定欧洲白种人人群中不同笑容美学参数的频率并探讨可能的性别差异非常重要。方法照片是在140位个体（70位男性和70位女性）的休息和强迫微笑条件下获得的，平均年龄为20.1±4.3岁。记录了不同的变量，包括上颌切齿间中线相对于面部中线的位置，微笑的弧线和宽度以及牙齿的形状。使用SPSS 15.0版统计软件包处理数据，采用卡方检验，置信度为95％。统计功效为80％，显着性水平为5％（α= 0.05）。结果共有94.3％的样本呈上颌切齿中线与面部中线重合，而80％的人则带有辅音微笑线。在47.1％的病例中，上唇的曲线是向上的，接着是41.4％的直线。大多数受试者（84.3％）的笑容中等，牙齿暴露于第二前磨牙（61.4％）。男性和女性之间没有显着差异。结论需要整合美学标准，以确保令人满意和可预测的牙科治疗结果。男性和女性之间没有统计学上的显着差异。