三维数字化技术测量矫治前后上颌尖牙与后牙轴倾和转矩变化初探

Tip and torque changes in maxillary buccal segment after orthodontic trealment： a three-dimensional study

目的应用三维数字化技术探索正畸治疗中上颌尖牙、前磨牙和磨牙三维位置的变化规律。方法通过随机数字表随机抽取北京大学口腔医学院·口腔医院正畸科资料完整的病例28例（减数组、非减数组各14例）。点激光扫描获得三维数字化牙颌模型，用腭皱重叠方法重叠矫治前后的上颌数字化模型，用三维图像配准技术将矫治后牙齿的临床冠面轴转移至矫治前同名牙上，以矫治后上颌胎平面为共同参考面，分别测量减数和非减数组矫治前后上颌尖牙、前磨牙和磨牙轴倾和转矩的变化。结果非减数组矫治后第二前磨牙轴倾减小1．5°，矫治前后差异有统计学意义（P〈0．05）；矫治后上颌第一、第二前磨牙冠颊向转矩分别增加5．1°和4．2°，与矫治前相比，差异有统计学意义（P〈0．05）。减数组矫治后上颌尖牙冠舌向转矩增加3．8°，矫治前后差异有统计学意义（P〈0．05）。结论三维图像配准技术可将矫治前后的数字化牙颌模型置于同一坐标系中测量矫治前后牙齿轴倾和转矩的变化。非减数矫治具有后倾上颌第二前磨牙，颊倾上颌前磨牙的作用；而减数矫治具有舌倾上颌尖牙的作用。

Objective To investigate three-dimensional imaging registration and superimposition techniques in measuring the tip and torque change of upper canine, premolar and first molar after orthodontic treatment. Methods Twenty-eight subjects （14 extraction cases and 14 non-extraction cases） with full records were randomly selected from the Department of Orthodontics, Peking University School and Hospital of Stomatology. The pre-and post-treatment upper dental casts were digitized with three-dimensional spot laser scanner and superimposed with reverse engineering software. The facial axis of the clinical crown （FACC） was transferred from post-treatment teeth to the pre-treatment teeth using three-dimensional imaging registration. The occlusal plane was constructed on the post-treatment upper digital cast and the tip and torque values were measured. Results In the non-extraction group, the tip of the second premolar decreased by 1.5 ° （P 〈 0. 05 ）. The bueeal crown torque of the first and second premolars increased by 5.1 ° and 4. 2°（ P 〈 0. 05 ）, respectively. In the extraction group, the lingual crown torque of upper canine increased by 3.8°（ P 〈 0. 05 ）. Conclusions Non-extraction orthodontic treatment tended to tip the upper second premolar distally and increased the buccal crown torque of the upper premolars while extraction treatment increased the lingual crown torque of the upper canine.