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, China.
State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
J Endod. 2021 May;47(5):779-786. doi: 10.1016/j.joen.2021.02.006. Epub 2021 Feb 18.
The purpose of this study was to comprehensively assess by micro-computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population.
One hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature.
All DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P < .05) but not for types I and III (P > .05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion.
The novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal.
本研究的目的是通过体视学成像全面评估来自一个人群的下颌第一磨牙的远舌（DL）根和根管的解剖特征。
检查了 102 个标本，以确定 DL 根管的位置和初始方向，以及根尖偏差距离与根管弯曲角度之间的关系。
所有 DL 根均只有 1 个根管。提出了一种新的下颌第一磨牙 DL 根的 7 类分类系统。大多数 DL 根为 IV 型（28 个牙）、III 型（26 个牙）和 V 型（25 个牙）。所有根型的平均根管弯曲度均超过 25°。对于 II 型、IV 型和 V 型，根管和根弯曲角度之间存在正相关（P <.05），但对于 I 型和 III 型则没有（P >.05）。在颊舌向观，大多数 DL 根为直根，而在近远中向观，根弯曲度接近最大值。DL 根管的口部距离将近中颊根管和近中舌根管的口部连线二等分的线比远颊根管远 4 倍。近中颊-近中舌线与牙髓腔冠三分之一在牙釉质下水平投影的夹角在左侧和右侧牙齿上分别为 8.1° ± 10.0°和 6.1° ± 8.2°。插入模拟锉与牙骨质-牙釉质交界的角度为 57.9° ± 6.3°。73%的 DL 根管在根尖区域没有狭窄。DL 根管狭窄，呈锥形截顶体形状，根尖部分的锥度为 0.04。
DL 根的新分类有助于更好地理解根管的临床挑战性解剖结构。
