目的：研究在数字化牙颌模型上确定平面的两种方法的可重复性并比较其差异。方法：从北京大学口腔医院正畸科2004年7月至2008年8月治疗完成并具有完整临床资料的806例病例中，以Angle分类为分层因素，随机抽取48个病例，扫描其治疗后石膏模型生成数字化模型。在自行开发的软件中，由1名测量者以至少1周的间隔、重复5次在模型上确定标志点，拟合出1组解剖平面和1组功能平面；并由6名测量者分别定点，拟合出2组平面。计算每个模型各组平面夹角的标准差，比较4组平面的可重复性并分析出现极端值的模型。结果：功能平面和解剖平面的可重复性在同一测量者差异无统计学意义（P＞0.1），在6名测量者间差异有统计学意义（P＜0.001）， 功能平面的合并样本标准差小于解剖平面，相差0.2°。同一测量者和6名测量者确定的功能平面的可重复性差异没有统计学意义（P＞0.1），解剖平面的可重复性差异有统计学意义（P＜0.001），同一测量者的合并样本标准差小于6名测量者，相差0.12°。结论：由一名测量者进行一批模型的测量时，功能平面与解剖平面的可重复性相同，均适合作为参考平面；由不同测量者进行大批量的测量时，功能平面的可重复性好于解剖平面，但差距较小。

Objective：To assess the repeatability（intraobserver comparison）and reproducibility（interobserver comparison）of two different methods for establishing the occlusal plane on digital dental models．Methods:With Angle’s classification as a stratification factor，48 cases were randomly extracted from 806 ones which had integrated clinical data and had their orthodontic treatment from July 2004 to August 2008 in Department of Orthodontics，Peking University School and Hospital of Stomatology．Post-treatment plaster casts of 48 cases were scanned by Roland LPX-1200 3D laser scanner to generate geometry data as research subjects．In a locally developed software package，one observer repeated 5 times at intervals of at least one week to localize prescriptive landmarks on each digital model to establish a group of functional occlusal planes and a group of anatomic occlusal planes, while 6 observers established two other groups of functional and anatomic occlusal planes independently．Standard deviations of dihedral angles of each group on each model were calculated and compared between the related groups．The models with the five largest standard deviations of each group were studied to explore possible factors that might influence the identification of the landmarks on the digital models．Results: Significant difference of intraobserver variability was not detected between the functional occlusal plane and the anatomic occlusal plane （P＞0.1），while that of interobserver variability was detected （P＜0.001）．The pooled experimental standard deviation the 6 observers established for the functional occlusal plane was 0.2° smaller than that of the anatomic occlusal plane．The functional occlusal plane’s variability of intraobserver and interobsever did not differ significantly （P＞0.1），while the anatomic occlusal plane’s variability of the intraobserver was significantly smaller than that of the interobserver （P＜0.001），with a 0.12° difference value of the pooled experimental standard deviation．Conclusion: When one observer measures a number of digital models，both the functional and the anatomic occlusal planes are suitable as a conference plane with equal repeatability. When several observers measure a large number of digital models，the functional occlusal plane is more reproducible than the anatomic occlusal plane，but the difference is small．