Micro-CT Evaluation of Root and Canal Morphology of Mandibular First Premolars with Radicular Grooves

Abstract The aim of this study was to evaluate morphological features of 70 single-rooted mandibular first premolars with radicular grooves (RG) using micro-CT technology. Teeth were scanned and evaluated regarding the morphology of the roots and root canals as well as length, depth and percentage frequency location of the RG. Volume, surface area and Structure Model Index (SMI) of the canals were measured for the full root length. Two-dimensional parameters and frequency of canal orifices were evaluated at 1, 2, and 3 mm levels from the apical foramen. The number of accessory canals, the dentinal thickness, and cross-sectional appearance of the canal at different root levels were also recorded. Expression of deep grooves was observed in 21.42% of the sample. Mean lengths of root and RG were 13.43 mm and 8.5 mm, respectively, while depth of the RG ranged from 0.75 to 1.13 mm. Mean canal volume, surface area and SMI were 10.78 mm3, 58.51 mm2, and 2.84, respectively. Apical delta was present in 4.35% of the sample and accessory canals were observed mostly at the middle and apical thirds. Two-dimensional parameters indicated an oval-shaped cross-sectional appearance of the root canal with a high percentage frequency of canal divisions (87.15%). Canal configuration type V (58.57%) was the most prevalent. C-shaped configuration was observed in 13 premolars (18.57%), whereas dentinal thickness ranged from 1.0 to 1.31 mm. Radicular grooves in mandibular first premolars was associated with the occurrence of several anatomical complexities, including C-shaped canals and divisions of the main root canal.

摘要 本研究旨在利用显微计算机断层扫描（micro-CT）技术，评估70颗伴牙根沟（radicular groove）的下颌单根第一前磨牙的形态学特征。所有受试牙齿经扫描后，针对其牙根与根管形态、牙根沟的长度、深度及发生频率占比展开分析。测量了全根长范围内根管的体积、表面积及结构模型指数（Structure Model Index, SMI）。在距根尖孔1、2、3 mm的水平位置，评估了根管口的二维参数与出现频率。同时记录了副根管的数量、牙本质厚度，以及不同牙根截面的根管形态特征。样本中21.42%存在深牙根沟表现。牙根与牙根沟的平均长度分别为13.43 mm与8.5 mm，牙根沟深度介于0.75~1.13 mm之间。根管的平均体积、表面积及SMI分别为10.78 mm³、58.51 mm²与2.84。4.35%的样本存在根尖三角（apical delta），副根管多分布于根中与根尖三分之一区段。二维参数分析显示，根管截面呈椭圆形，主根管分支的发生频率高达87.15%。根管构型V型最为常见，占比达58.57%。13颗前磨牙（18.57%）呈现C形根管构型，牙本质厚度范围为1.0~1.31 mm。下颌第一前磨牙的牙根沟与多种解剖学复杂性表现相关，包括C形根管与主根管分支。