While several materials and techniques have been used to assess the quality of root canal fillings in micro-CT images, the lack of standardization in scanning protocols has produced conflicting results. Hence, the aim of this study was to determine a cutoff voxel size value for the assessment of root canal filling voids in micro-CT and nano-CT images. Twenty freshly extracted mandibular central incisors were used. Root canals were prepared with nickel titanium files to an ISO size 40/0.06 taper and then filled with a single cone (40/0.06 taper) and AH Plus sealer. The teeth were scanned with different voxel sizes with either micro-CT (5.2, 8.1, 11.2, and 16.73 μm) or nano-CT (1.5 and 5.0 μm) equipment. Images were reconstructed and analyzed with the NRecon and CTAn software. Void proportion and void volume were calculated for each tooth in the apical, middle, and coronal thirds of the root canal. Kruskal-Wallis and post hoc Mann–Whitney U tests were performed with a significance level of 5%. In micro-CT images, significantly different results were detected among the tested voxel sizes for void proportion and void volume, whereas no such differences were found in nano-CT images (p > 0.05). Micro-CT images showed higher void numbers over the entire root length, with statistically significant differences between the voxel size of 16.73 μm and the other sizes (p < 0.05). The values of the different nano-CT voxel sizes did not significantly differ from those of the micro-CT (5.2, 8.1, and 11.2 μm), except for the voxel size of 16.73 μm (p < 0.05). All tested voxel sizes enabled the detection of root canal filling voids except for the voxel size of 16.73 μm. Bearing in mind the limitations of this study, it seems that a voxel size of 11.2 μm can be used as a reliable cutoff value for the assessment of root canal filling voids in micro-CT imaging.

中文翻译：

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Micro-CT 和 Nano-CT 图像中根管充填空隙阈值的评估

虽然已经使用了多种材料和技术来评估显微 CT 图像中根管充填的质量，但扫描协议缺乏标准化产生了相互矛盾的结果。因此，本研究的目的是确定用于评估显微 CT 和纳米 CT 图像中根管充填空隙的截止体素大小值。使用了 20 颗新鲜拔出的下颌中切牙。根管用镍钛锉准备成 ISO 尺寸 40/0.06 锥度，然后用单锥（40/0.06 锥度）和 AH Plus 封闭剂填充。使用微 CT（5.2、8.1、11.2 和 16.73 μm）或纳米 CT（1.5 和 5.0 μm）设备以不同的体素尺寸扫描牙齿。使用 NRecon 和 CTAn 软件重建和分析图像。计算每颗牙根管根尖、中、冠三分之一处的空隙率和空隙体积。Kruskal-Wallis 和 post hoc Mann-Whitney U 检验的显着性水平为 5%。在显微 CT 图像中，检测到的测试体素大小之间空隙率和空隙体积的结果显着不同，而在纳米 CT 图像中没有发现这种差异（p > 0.05）。显微 CT 图像显示整个牙根长度上的空隙数更高，体素大小为 16.73 μm，与其他大小之间存在统计学显着差异 (p < 0.05)。除了体素尺寸为 16.73 μm（p < 0.05）外，不同纳米 CT 体素尺寸的值与微 CT（5.2、8.1 和 11.2 μm）的值没有显着差异。除了 16.73 μm 的体素尺寸外，所有测试的体素尺寸都能够检测到根管充填空隙。考虑到本研究的局限性，11.2 μm 的体素尺寸似乎可以用作评估显微 CT 成像中根管充填空隙的可靠截止值。