Department of Endodontics, The British University in Egypt Faculty of Dentistry, Cairo, Egypt.
Eur Endod J. 2024 Mar 8;9(2):133 - 138. doi: 10.14744/eej.2023.71676. Epub 2024 Jan 24.
To evaluate the impact of different file access angles and root canal curvature's location on the fatigue failure of One Curve (OC) and E3 Azure (EZ) NiTi files using a dynamic model at simulated body temperature.
Eighty new instruments with similar tip sizes and taper (#25/0.06) from two NiTi rotary systems, One Curve and E3 Azure, were tested at simulated body temperatures (37°C) using a custom-made dynamic cyclic fatigue device. Instruments were divided into four subgroups according to the location of root canal curvature (a coronal curve 5 mm from the root canal orifice and an apical curve 10 mm from the root canal orifice) and the angle of file access (0° or 30°). Instruments were operated in simulated stainless-steel canals having a 60° curve and a 3 mm radius. A custom-made device produced controlled vertical pecks during file rotation. Time to failure (sec) was registered, and the length of the fragment segments was measured (mm). Data were analysed statistically with One-Way ANOVA and Tukey post hoc tests. The significance level was set at 5%. All separated instruments were examined by scanning electron microscope.
One-way ANOVA (p<0.05) found a significant difference among the tested instruments. Post Hoc analysis revealed lower cyclic fatigue resistance when the angle of file access was 30º, and the root canal curvature was located coronally for both files (p<0.0001). Three-way ANOVA showed that the angle of file access was the most influential contributor to cyclic fatigue, followed by the location of file curvature and, finally, the file type (p<0.0001). The fractographic examination revealed a predominantly ductile fracture mode for all tested instruments. The lengths of all fractured segments showed no significant difference (p>0.05), indicating an accurate trajectory during testing.
OC files had superior cyclic fatigue resistance than EZ files; coronal curvatures negatively impacted cyclic fatigue resistance compared to apical curvatures, while the angle of file access presented the highest impact on dynamic cyclic fatigue.
在模拟体温条件下，通过动态模型评估不同根管锉的入口角度和根管弯曲位置对 One Curve（OC）和 E3 Azure（EZ）镍钛锉疲劳失效的影响。
从两种镍钛旋转器械（One Curve 和 E3 Azure）中选择具有相似尖端尺寸和锥度（#25/0.06）的 80 个新器械，在模拟体温（37°C）下使用定制的动态循环疲劳装置进行测试。根据根管弯曲位置（距根管口 5mm 的根管冠向弯曲和距根管口 10mm 的根管根尖向弯曲）和根管锉入口角度（0°或 30°）将器械分为 4 个亚组。器械在模拟不锈钢根管中进行操作，根管具有 60°的弯曲度和 3mm 的半径。定制的装置在根管锉旋转时产生受控的垂直敲击。记录失效时间（秒），并测量断片段的长度（mm）。使用单向方差分析和 Tukey 事后检验对数据进行统计学分析。显著性水平设定为 5%。所有分离的器械都用扫描电子显微镜进行了检查。
单因素方差分析（p<0.05）发现测试器械之间存在显著差异。事后分析显示，当根管锉入口角度为 30°且根管弯曲位于冠向时，两种锉的循环疲劳阻力均较低（p<0.0001）。三因素方差分析表明，根管锉入口角度是影响循环疲劳的最主要因素，其次是锉弯曲位置，最后是锉类型（p<0.0001）。断口形貌分析显示，所有测试器械均呈现出延性断裂模式。所有断片段的长度无显著差异（p>0.05），表明在测试过程中具有准确的轨迹。
OC 锉的循环疲劳阻力优于 EZ 锉；与根尖向弯曲相比，冠向弯曲对循环疲劳阻力有负面影响，而根管锉入口角度对动态循环疲劳的影响最大。
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