目的:研究医师肉眼对无牙颌患者鼻唇角差异侧面观的视觉敏感阈值,明确人眼可有效识别的鼻唇角差异大小,以期为软组织侧貌审美评价相关研究提供人眼可识别的鼻唇角差异的参考值。方法:获取3名无牙颌患者戴入不同唇部支撑诊断义齿的面部三维数据,对患者的面部三维数据进行同比例侧面截图,以口腔修复科医师(主任医师)和患者肉眼观察双重确认的合适唇丰满度时的侧面截图为参照图片,将其他侧面截图分别与之组合成组,由受试者以随机顺序观察。选择15名口腔医师作为受试者观察每组图片的鼻唇角差异情况,测量计算每组两张图片的鼻唇角差值。实验结果绘制成受试者工作特征(ROC)曲线,使用SPSS 20.0统计软件及约登(Youden)指数计算最佳截断值作为医师肉眼对无牙颌患者鼻唇角差异侧面观的视觉敏感阈值。结果:15名受试者数据分别绘制ROC曲线,其中最佳截断值最大者为5.55°,最小者为3.12°。数据汇总后绘制整体受试者工作特征曲线,其最佳截断值为5.36°(AUC=0.84>0.5, P=0.000<0.05)。当图片的鼻唇角差异在5.36°以上时,受试者能够有效识别。结论:人对鼻唇角变化量的视觉感知存在极限,研究得出了5.36°的鼻唇角差异侧面观的视觉敏感阈值。低于此值的鼻唇角差异可能无临床意义,此结果为软组织侧貌审美评价提供了人眼可识别的鼻唇角变化量阈值的参考值,可应用于软组织侧貌的美学评估,以及作为以鼻唇角为指标进行精度评价的相关研究的误差等级。

Objective: To study the visual sensitivity threshold of physician’s naked eye to the difference of nasolabial angle in edentulous jaw patients, and to provide a reference value for the study of aesthetic evaluation of soft tissue profile for the difference of nasolabial angle that can be recognized by human eyes. Methods: Three-dimensional facial images of three edentulous patients with different diagnostic dentures intro-oral were obtained.Lateral screenshots of each patient’s three-dimensional facial image with the same scale were obtained by using reverse engineering software (Geomagic studio 2014).The screenshot of the patient’s three-dimensional facial image with suitable lip support (The suitable lip support was confirmed by both patients and prosthodontists who had clinical experience for more than 20 years) was taken as the reference picture, and the remaining pictures were grouped with it respectively. All the pictures were observed in random order by the subjects. Fifteen dentists were asked to judge the difference of nasolabial angle between the two pictures of each group on the computer screen. The difference of nasolabial angle between the two pictures in each group was measured and calculated. The ROC curve was drawn, and the best cut-off value was calculated as the visual sensitivity threshold. Results: The data of the 15 subjects were used to draw ROC curves separately. The maximum and minimum best cut-off values were 5.55 degrees and 3.12 degrees respectively. The ROC curve of the whole 15 subjects was drawn after data aggregation, and the best cut-off value was 5.36 degrees (AUC=0.84>0.5, P=0.000<0.05).When the difference of nasolabial angle was above 5.36 degrees, the subjects could recognize it effectively. Conclusion: There is a visual limit in the observation of the nasolabial angle with the naked eye. In this study, a visual sensitivity threshold of 5.36 degrees for the difference of the nasolabial angle was obtained. The difference of nasolabial angle below this value can be regarded as no clinical significance. This result provides a reference value for human eyes to recognize the difference of nasolabial angle in soft tissue profile aesthetic evaluation. It can be applied to the aesthetic evaluation of soft tissue profile and can be used as the error level of related research with nasolabial angle as an index for accuracy evaluation.