Department of Endodontics, University of Iowa College of Dentistry, Iowa City, Iowa, USA.
J Endod. 2011 Aug;37(8):1162-5. doi: 10.1016/j.joen.2011.05.012. Epub 2011 Jun 25.
The apical constriction (AC) has been a traditional landmark as an end point of canal preparation and obturation. However, the morphology and incidence of this structure have not been definitively determined. The purpose of this study was to determine these factors by using a noninvasive technology, micro-computed tomography.
Forty extracted maxillary molar palatal roots were separated and mounted. Each root was scanned with micro-computed tomography. Slices from the scan were computer reconstructed by using special software. This rendered each root three-dimensionally "transparent." Roots were rotated, and the apical canal region was selected. In 2 sessions, trained evaluators identified the AC as to (1) presence (single and tapered) or (2) absence (flaring, parallel, and delta). Evaluator agreement was assessed by Cohen's kappa. Descriptive frequencies were determined for apical constriction presence and morphology.
Interagreement and intra-agreement of evaluators were good. In regard to frequency of occurrence, most (65%) canals did not demonstrate an AC. The morphology, in order of most to least, was parallel 35%, single 19%, flaring 18%, tapering 15%, and delta 12%.
From the noninvasive evaluation of our sample it was concluded that an AC was usually not present and that this apical canal region was variable. If this is true with other tooth groups, the AC should not be used as an anatomical marker for preparation and obturation.
根尖缩窄（AC）一直是作为根管预备和充填终点的传统标志。然而，这个结构的形态和发生率尚未明确确定。本研究旨在通过使用非侵入性技术——微计算机断层扫描来确定这些因素。
将 40 颗上颌磨牙腭根分离并安装。对每个牙根进行微计算机断层扫描。通过特殊软件对扫描切片进行计算机重建，使每个牙根三维“透明”。旋转牙根，并选择根尖管区域。在 2 个会话中，经过培训的评估者根据（1）存在（单一和锥形）或（2）不存在（喇叭口状、平行和 delta 形）来识别 AC。通过 Cohen's kappa 评估评估者的一致性。确定根尖缩窄存在和形态的描述性频率。
评估者的组间和组内一致性良好。就出现频率而言，大多数（65%）根管没有显示出 AC。形态上，最常见到最不常见的依次为平行 35%、单一 19%、喇叭口状 18%、锥形 15%和 delta 形 12%。
从我们样本的非侵入性评估中得出结论，通常不存在根尖缩窄，并且这个根尖管区域是可变的。如果这适用于其他牙组，那么根尖缩窄不应作为预备和充填的解剖标志。
