Peng H, Wang X, Chen K
Orthodontic Department, College of Stomatology, West China University of Medical Sciences.
Hua Xi Kou Qiang Yi Xue Za Zhi. 2000 Feb;18(1):55-7.
It is important to predict mesiodistal crown diameter of the permanent canines and premolars in the mixed dentition, which helps to determine malocclusion and its further development. But there is still no article about this equation of Chinese used to predict mesiodistal crown diameter of cuspids and premolars. This research is to measure mesiodistal crown diameters, to study relationship between lower incisors and canines and premolars, and to provide the most accurate and easy basis in orthodontic diagnosis and treatment for Chinese people.
140 Chinese students (60 male, 80 female) who were from eighteen to twenty-five years old without orthodontic history Chengdu were randomly collected in. All teeth must be free of visible malform, aberration, and fully erupted. Impressions were taken, and measurements were made, parallel to the occlusal plane at the greatest mesiodistal width of each tooth on dental cast with electronic caliper (0.01 mm). Each tooth was measured twice and the average of the two readings was taken as the dimension for that individual tooth. Mesiodistal crown diameters were statistically analyzed with t-test and linear regression, using the SAS (Statistic Analyses System) computer package.
It was found that mesiodistal crown diameters had significantly statistical difference in gender. Hence the mesiodistal crown diameters were assessed and investigated separately for the male and the female. It was also found that the total mesiodistal crown diameter of lower incisors was closely correlated with the total mesiodistal crown diameter of canines and premolars. The correlation coefficients between the independent variable and dependent variables were 0.599 for upper canines and premolars and 0.654 for lower canines and premolars in the males and 0.586 and 0.635, respectively, in the females. The P were found to be less than 0.001 for both arches. The correlation coefficients had significantly statistical difference.
The equations predicting overall mesiodistal crown diameters of upper and lower unerupted canines and premolars for male and female Chinese people were established respectively: Maxillary (y = 10.87 + 0.51 x (male)), y = 11.88 + 0.46 x (female), Mandibular (y = 10.36 + 0.50 x (male), y = 10.03 + 0.49 x (female)), y (total mesiodistal crown diameter of canines and premolars), and x (total mesiodistal crown diameter of lower incisors).
预测混合牙列期恒牙尖牙和前磨牙的近远中牙冠直径很重要，这有助于确定错牙合畸形及其进一步发展。但目前尚无关于中国人预测尖牙和前磨牙近远中牙冠直径的公式的文章。本研究旨在测量近远中牙冠直径，研究下颌切牙与尖牙及前磨牙之间的关系，为中国人的正畸诊断和治疗提供最准确、简便的依据。
随机选取140名年龄在18至25岁之间、无正畸治疗史的成都中国学生（男60名，女80名）。所有牙齿必须无明显畸形、变异且完全萌出。制取印模，并用电子卡尺（精度0.01mm）在石膏模型上与牙合平面平行测量每颗牙齿最大近远中宽度。每颗牙齿测量两次，取两次读数的平均值作为该颗牙齿的尺寸。使用SAS（统计分析系统）计算机软件包对近远中牙冠直径进行t检验和线性回归统计分析。
发现近远中牙冠直径在性别上有显著统计学差异。因此分别对男性和女性的近远中牙冠直径进行评估和研究。还发现下颌切牙的近远中牙冠直径总和与尖牙及前磨牙的近远中牙冠直径总和密切相关。男性中，自变量与因变量之间的相关系数，上颌尖牙和前磨牙为0.599，下颌尖牙和前磨牙为0.654；女性中分别为0.586和0.635。两个牙弓的P值均小于0.001。相关系数有显著统计学差异。
分别建立了中国男性和女性上下未萌出尖牙和前磨牙近远中牙冠直径总和的预测公式：上颌（y = 10.87 + 0.51x（男性）），y = 11.88 + 0.46x（女性）；下颌（y = 10.36 + 0.50x（男性），y = 10.03 + 0.49x（女性）），y（尖牙和前磨牙近远中牙冠直径总和），x（下颌切牙近远中牙冠直径总和）。
