Zhao D, Shen Y, Peng B, Haapasalo M
Department of Operative Dentistry and Endodontics, School and Hospital of Stomatology, Wuhan University, Wuhan, China.
Division of Endodontics, Department of Oral Biological & Medical Sciences, Faculty of Dentistry, The University of British Columbia, Vancouver, BC, Canada.
Int Endod J. 2016 Oct;49(10):990-5. doi: 10.1111/iej.12550. Epub 2015 Oct 12.
To compare the cyclic fatigue resistance of HyFlex CM, Twisted Files (TF), K3XF, Race, and K3, and evaluate the effect of autoclave sterilization on the cyclic fatigue resistance of these instruments both before and after the files were cycled.
Five types of NiTi instruments with similar size 30, .06 taper were selected: HyFlex CM, TF, K3XF, Race and K3. Files were tested in a simulated canal with a curvature of 60° and a radius of 3 mm. The number of cycles to failure of each instrument was determined to evaluate cyclic fatigue resistance. Each type of instruments was randomly divided into four experimental groups: group 1 (n = 20), unsterilized instruments; group 2 (n = 20), pre-sterilized instruments subjected to 10 cycles of autoclave sterilization; group 3 (n = 20), instruments tested were sterilized at 25%, 50% and 75% of the mean cycles to failure as determined in group 1, and then cycled to failure; group 4 (n = 20), instruments cycled in the same manner as group 3 but without sterilization. The fracture surfaces of instruments were examined by scanning electron microscopy (SEM).
HyFlex CM, TF and K3XF had significantly higher cyclic fatigue resistance than Race and K3 in the unsterilized group 1 (P < 0.05). Autoclave sterilization significantly increased the MCF of HyFlex CM and K3XF (P < 0.05) both before and after the files were cycled. SEM examination revealed a typical pattern of cyclic fatigue fracture in all instruments.
HyFlex CM, TF and K3XF instruments composed of new thermal-treated alloy were more resistant to fatigue failure than Race and K3. Autoclaving extended the cyclic fatigue life of HyFlex CM and K3XF.
比较HyFlex CM、Twisted Files（TF）、K3XF、Race和K3的抗循环疲劳性能，并评估高压蒸汽灭菌对这些器械在循环前后抗循环疲劳性能的影响。
选择五种尺寸为30、锥度为0.06的镍钛器械：HyFlex CM、TF、K3XF、Race和K3。器械在曲率为60°、半径为3毫米的模拟根管中进行测试。确定每种器械的失效循环次数以评估抗循环疲劳性能。每种器械随机分为四个实验组：第1组（n = 20），未灭菌器械；第2组（n = 20），经过10次高压蒸汽灭菌的预灭菌器械；第3组（n = 20），测试的器械在第1组确定的平均失效循环次数的25%、50%和75%时进行灭菌，然后循环至失效；第4组（n = 20），器械以与第3组相同的方式循环但不进行灭菌。通过扫描电子显微镜（SEM）检查器械的断裂表面。
在未灭菌的第1组中，HyFlex CM、TF和K3XF的抗循环疲劳性能明显高于Race和K3（P < 0.05）。高压蒸汽灭菌在器械循环前后均显著提高了HyFlex CM和K3XF的平均失效循环次数（P < 0.05）。SEM检查显示所有器械均有典型的循环疲劳断裂模式。
由新型热处理合金制成的HyFlex CM、TF和K3XF器械比Race和K3更抗疲劳失效。高压蒸汽灭菌延长了HyFlex CM和K3XF的循环疲劳寿命。
