Endodontic Department, Hamdan Bin Mohammed College of Dental Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai, United Arab Emirates.
Department of Conservative Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan, Korea.
J Endod. 2022 Nov;48(11):1428-1433. doi: 10.1016/j.joen.2022.08.004. Epub 2022 Aug 18.
This study aimed to evaluate the dynamic cyclic fatigue resistance of heat-treated nickel-titanium (NiTi) files after usage and autoclaving.
Two heat-treated NiTi file systems with tip sizes of #25 (ie, ProTaper Gold F2 [Dentsply Sirona, Charlotte, NC] and TruNatomy Prime [Dentsply Sirona]) were selected. Files of each system were divided into 3 experimental subgroups (n = 10). For subgroup 1, new files were tested to establish the baseline number of cycles to failure (NCF). For subgroup 2, files underwent canal instrumentation in a simulated J-shaped canal block with 35° of curvature and a 16.5-mm length. The simulated canals were pre-enlarged using stainless steel files #10K and #15K. After instrumentation, the files were tested. For subgroup 3, files underwent canal instrumentation as in subgroup 2 followed by autoclave sterilization and then were tested for cyclic failure. The cyclic fatigue test was performed in dynamic pecking motion under body temperature. The time to fracture was recorded and calculated into NCF. Fracture fragment lengths were measured using a digital microcaliper. Statistical analysis was conducted using the independent t test and multifactorial analysis of variance with 95% significance. Scanning electron microscopy was used to examine the topographic characteristics after cyclic fatigue tests.
There were no significant differences between file systems in subgroup 1 using new files (P < .05). Although PG reduced the NCF after use, TN showed a significantly increased NCF (P < .05). However, after sterilization, TN showed a reduced NCF compared with the used one (P < .05).
Cyclic loading by usage and heat treatment during sterilization may result in different cyclic fatigue resistance according to the geometry and alloy characteristics.
本研究旨在评估使用和高压蒸汽灭菌后热处理镍钛（NiTi）锉的动态循环疲劳阻力。
选择尖端尺寸为 #25 的两种热处理 NiTi 文件系统（即 Protaper Gold F2[登士柏西诺德，夏洛特，NC]和 TruNatomy Prime[登士柏西诺德]）。每个系统的文件分为 3 个实验组（n=10）。对于第 1 组亚组，测试新文件以建立失效循环数（NCF）的基线。对于第 2 组亚组，文件在模拟 J 形根管块中进行根管预备，曲率为 35°，长度为 16.5mm。模拟根管用不锈钢文件#10K 和#15K 预先扩大。器械预备后，测试文件。对于第 3 组亚组，文件按照第 2 组亚组进行根管预备，然后进行高压蒸汽灭菌，然后进行循环疲劳测试。循环疲劳试验在体温下以动态啄动方式进行。记录断裂时间并计算 NCF。使用数字测微卡尺测量断裂碎片长度。使用独立 t 检验和多因素方差分析进行统计分析，显著性水平为 95%。使用扫描电子显微镜检查循环疲劳试验后的形貌特征。
在第 1 组使用新文件的亚组中，文件系统之间没有显著差异（P<.05）。虽然 PG 在使用后降低了 NCF，但 TN 显示出明显增加的 NCF（P<.05）。然而，在消毒后，TN 与使用过的相比显示出降低的 NCF（P<.05）。
根据几何形状和合金特性，使用中的循环加载和消毒过程中的热处理可能导致不同的循环疲劳阻力。
