Objective This study is aimed at determining (1) the effect of root-end resection, ultrasonic root-end preparation, and root-end filling on the incidence of crack formation and propagation by using a digital microscope (DM) and optical coherence tomography (OCT) and (2) the performance of OCT on the detection of cracks by comparing with microcomputed tomography (micro-CT) as a reference standard. Methodology Thirty extracted lower incisors were endodontically treated and subjected to root-end resection and ultrasonic root-end cavity preparation. Then, the teeth were divided into three groups (n = 10, each), and the root-end cavity was either left unfilled or filled with mineral trioxide aggregate (MTA) or super-EBA. The resected surface was observed with OCT and DM after the root-end resection, ultrasonic root-end preparation, and root-end filling, and the frequency of incomplete and complete cracks were recorded. The observation was repeated after two weeks, one month, and two months, and micro-CT scans after two months were taken as the gold standard. Results The DM results show dentinal crack formation in 47% of the samples following root-end resection and in 87% following ultrasonic preparation. After the ultrasonic preparation, no existing crack propagated to a complete crack, but new cracks were formed. MTA and super-EBA had no effect on crack formation. The Spearman correlation coefficient between OCT and DM was 0.186 (very weak correlation; p = 0.015). Sensitivity and specificity in comparison to micro-CT were 0.50 and 0.55 in OCT and 1.00 and 0.35 in DM, respectively. McNemar's test showed a significant difference between OCT and DM (p < 0.05). Conclusion Apical resection and ultrasonic preparation could form dentinal cracks. OCT and DM showed different detection frequencies of cracks with very weak correlation. DM showed superior sensitivity compared with OCT.

中文翻译：

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使用数码显微镜和光学相干断层扫描的超声波根端制备和填充评估裂纹的形成和扩展

目的本研究旨在通过数字显微镜（DM）和光学相干断层扫描确定（1）根端切除、超声根端准备和根端填充对裂纹形成和扩展发生率的影响（ OCT）和（2）通过与作为参考标准的微型计算机断层扫描（micro-CT）进行比较，OCT 对裂纹检测的性能。方法 对30颗拔除的下切牙进行牙髓治疗，并进行根端切除和超声根端腔制备。然后，将牙齿分为三组（每组 n = 10），根端腔要么未填充，要么填充有矿物三氧化物聚集体 (MTA) 或超级 EBA。根端切除、超声根端预备、根端充填后用OCT和DM观察切除面，并记录不完全和完全裂纹的频率。两周、一个月、两个月后重复观察，以两个月后的显微CT扫描为金标准。结果 DM 结果显示，47% 的样本在根端切除后和 87% 的样本在超声制备后形成牙本质裂纹。超声制备后，现有裂纹没有扩展为完整的裂纹，而是形成了新的裂纹。MTA 和super-EBA 对裂纹的形成没有影响。OCT 和 DM 之间的 Spearman 相关系数为 0.186（相关性非常弱；p = 0.015）。与 micro-CT 相比，OCT 的敏感性和特异性分别为 0.50 和 0.55，DM 分别为 1.00 和 0.35。McNemar 的检验显示 OCT 和 DM 之间存在显着差异 (p < 0.05)。结论根尖切除及超声预备可形成牙本质裂隙。OCT和DM表现出不同的裂纹检测频率，相关性非常弱。与 OCT 相比，DM 显示出更高的灵敏度。