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目的:研究上颌前磨牙的颊面形态及冠根成角关系对转矩的影响。方法:选自2006年1-12月中山大学光华口腔医院、暨南大学附属第一医院口腔科、深圳龙华人民医院口腔科收集的123颗正畸拔除的上颌前磨牙,其中第1前磨牙66颗、第2前磨牙57颗。利用锥形线束计算机断层扫描(CBCT)机将全部牙齿进行扫描,在CT工具软件下进行影像的三维重建并提取全部牙的正中矢状切面图像,利用自动计算机辅助设计(AutoCAD)软件对图像分别测量牙冠颊面4个不同高度的切线与牙冠长轴所成的角度;牙冠长轴与牙根长轴所成的角度。结果:不同高度间的角度变化上颌第2前磨牙变化较大,高度从3.0～4.5 mm,角度平均变化为9.17°。上颌第1、2前磨牙冠根角值分别为(4.84±4.06)°、(1.9,±3.55)°。结论:上颌前磨牙托槽粘结高度在牙合龈方不同的范围内变化相同距离对转矩的影响不同,越靠牙龈方对转矩的影响越大。上颌前磨牙存在一定的冠根角、且冠根角存在较大的个体差异。
OBJECTIVE: To study the effect of the relationship between buccal shape and crown angle on the torque of maxillary premolars. Methods: selected from the 2006 January-December Zhongshan University Guanghua School of Stomatology Hospital of Stomatology, First Affiliated Hospital of Jinan University, Shenzhen Longhua People’s Hospital of Stomatology before the collection of 123 orthodontic removal of maxillary molars, where the former first molars 66 , The first two premolar 57. Using a cone beam computed tomography (the CBCT) scanning machine all the teeth, in the three-dimensional reconstruction of CT images of tools and extracted sagittal section image of all the teeth, using an automated computer-aided design (the AutoCAD) software on each image The angle formed by the tangent of four different heights of the buccal surface of the crown and the major axis of the crown was measured. The angle between the major axis of the crown and the major axis of the root. Results: The angle changes between different height of the maxillary second premolar changes larger, the height from 3.0 to 4.5 mm, the average angle of change of 9.17 °. The maxillary root angles of the maxillary first and second premolars were (4.84 ± 4.06) ° and (1.9 ± 3.55) °, respectively. CONCLUSION: The effect of the same distance between the maxillary premolar molar height on different ranges of the occlusal gingiva varies with the torque, and the more the gingiva affects the torque. There is a certain crown root angle in the maxillary premolars, and there is a large individual difference in the crown root angle.