State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & Department of Cariology and Endodontics West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan Province, China.
Int Endod J. 2020 Feb;53(2):167-175. doi: 10.1111/iej.13220. Epub 2019 Oct 6.
To measure the coronal root canal morphology of permanent mandibular first molars using 3D coordinates for more precise conservative endodontic cavity preparation.
In total, 57 cone beam computed tomography (CBCT) images of sound mandibular molars with fully formed apices without previous endodontic treatment were taken from 33 patients aged 16 to 75 years. The CBCT machine (MCT-1[EX-2F], J. Morita Manufacturing Corp, Kyoto, Japan) provided 14-bit greyscale images with the voxel size of 0.125 mm. All images were taken at 80 kV and 5.0 mA, with a 17-s exposure time, which were then reconstructed in 3D models and viewed by an endodontist. The gender of the patients and the tooth position, and number of root canals, were recorded. The landmarks of coronal root canals were determined, then the distribution of landmarks, maximum curvature in the axial direction and curvature directions in the horizontal direction of coronal root canals were measured. Distributions of landmarks were analysed using a spatial statistics method. Data about curvature were compared using a t test.
Overall, the distribution of root canal orifices and the centre of the canal primary curve were more centralized than other landmarks. The landmarks were located more mesiobuccally to the centre of the occlusal plane of mandibular first molars. Specifically, the measurements of the maximum curvature of coronal root canals in the axial direction were as follows: in 3-canal teeth, the average angles of curvatures were 22°,23°,15° for mesiobuccal (MB), mesiolingual (ML) and distobuccal (DB) canals, respectively; in 4-canal teeth, the average angles of curvatures were 24°,26°,15°,22°for MB, ML, DB and distolingual (DL) canals, respectively. The degrees of coronal root canal curvatures in the horizontal direction were as follows: in 3-canal teeth, the average angles of curvatures were -8°,47°,-2° for MB, ML and DB canals, respectively; in 4-canals teeth, the average angles were -11°,50°,-28°,45° for MB, ML, DB and DL canals, respectively. Statistically, there was no reliable side or sex difference in any of the measurements (P > 0.05).
In permanent two-rooted mandibular first molars, the coronal canals clustered in the direction of the mesiobuccal side of the occlusal surface of the teeth.
通过 3D 坐标测量恒磨牙的根管冠部形态，以便更精确地进行保守性牙髓腔预备。
共采集了 33 名年龄在 16 至 75 岁之间的、具有完全形成的根尖且未经根管治疗的健康下颌磨牙的 57 个锥形束 CT（CBCT）图像。CBCT 机（MCT-1[EX-2F]，J. Morita Manufacturing Corp，日本京都）提供 14 位灰度值图像，体素大小为 0.125mm。所有图像均在 80kV 和 5.0mA 下以 17s 的曝光时间拍摄，然后重建为 3D 模型，并由牙髓病专家进行观察。记录患者的性别、牙齿位置、根管数量。确定根管冠部的标志点，测量标志点的分布、轴向最大曲率和根管冠部的水平曲率方向。使用空间统计学方法分析标志点的分布。使用 t 检验比较曲率数据。
总体而言，根管口和根管主弯曲的中心分布比其他标志点更集中。标志点位于下颌第一磨牙咬合平面的近中颊侧更靠近中心。具体而言，轴向根管冠部最大曲率的测量值如下：在 3 根管牙中，颊侧（MB）、近中舌侧（ML）和远颊侧（DB）根管的平均曲率角分别为 22°、23°、15°；在 4 根管牙中，MB、ML、DB 和远舌侧（DL）根管的平均曲率角分别为 24°、26°、15°、22°。根管冠部水平方向的曲率角度如下：在 3 根管牙中，MB、ML 和 DB 根管的平均曲率角分别为-8°、47°、-2°；在 4 根管牙中，MB、ML、DB 和 DL 根管的平均曲率角分别为-11°、50°、-28°、45°。统计学上，任何测量值均无可靠的侧别或性别差异（P＞0.05）。
在具有双根的恒磨牙中，根管冠部向牙齿咬合面的近中颊侧方向聚集。
