Detection of Root Canal Isthmuses in Molars by Map-Reading Dynamic using CBCT images

The aim of this study was to detect root isthmuses in maxillary and mandibular molars and evaluate their frequencies using map-reading dynamics in CBCT images. Two hundred extracted human maxillary and mandibular molars were used in ex vivo assay. A consecutive sample of two hundred maxillary and mandibular molars (first and second) was selected from CBCT exams. The isthmuses were detected from the pulp orifice to the apex and were recorded according to their beginning and their end, into categories: 1. begin and end in cervical third; 2. beginning in cervical third and end in middle third; 3. beginning in cervical third and end in apical third; 4. beginning and end in middle third; 5. begin in middle third and end in apical third; 6. beginning and end in apical third; 7. no isthmus. The scans were obtained in different planes with map-reading in axial slices of 0.5 mm/0.5 mm involved the coronal to apical direction. The frequencies of isthmus were analyzed according to the level of root and evaluated by Chi-square test. The level of significance was set at α=0.05. The presence of isthmus detected in maxillary molars was 86% in ex vivo assay and 62% in vivo assay, whereas in mandibular molars was observed 70% in ex vivo assay and 72% in vivo assay. The frequency of isthmus was high in both study models. The map-reading dynamics in CBCT images was found to be precise to detect the localization of isthmus.

本研究旨在通过CBCT（Cone Beam Computed Tomography，锥形束计算机断层扫描）图像的阅片动态分析法，检测上颌与下颌磨牙的牙根峡部（root isthmuses），并评估其检出率。本研究开展两项实验：其一为离体实验（ex vivo assay），共纳入200颗拔除的人类上颌及下颌磨牙；其二为在体实验（in vivo assay），从临床CBCT检查中连续选取200颗上颌、下颌第一及第二磨牙作为研究样本。研究将从髓室口（pulp orifice）至根尖（apex）的牙根峡部按其起止解剖位置划分为7类：1. 起止均位于牙根颈三分之一（cervical third）；2. 起于牙根颈三分之一、止于根中三分之一（middle third）；3. 起于牙根颈三分之一、止于根尖三分之一（apical third）；4. 起止均位于根中三分之一；5. 起于根中三分之一、止于根尖三分之一；6. 起止均位于根尖三分之一；7. 未检出牙根峡部。扫描采用多平面成像模式，以层厚与层间距均为0.5mm的轴位切片进行阅片，扫描范围覆盖从牙冠至根尖的方向。研究人员根据牙根的解剖分区对牙根峡部的检出率进行分析，并采用卡方检验（Chi-square test）进行统计学评估，设定检验水准为α=0.05。结果显示：离体实验中，上颌磨牙的牙根峡部检出率为86%，在体实验中为62%；下颌磨牙的牙根峡部检出率在离体实验中为70%，在体实验中为72%。两种实验模型下的牙根峡部检出率均较高。本研究证实，CBCT图像的阅片动态分析法可精准检测牙根峡部的定位。