Mechanical Properties of Anatomic Finishing Files: XP-Endo Finisher and XP-Clean

Abstract The aim of the present study was to evaluate the cyclic fatigue of two anatomic finishing files: XP-Endo Finisher and XP-Clean. Roughness pattern and the micro-hardness of the files were also assessed. Instruments were subjected to cyclic fatigue resistance measuring the time to fracture in an artificial stainless-steel canal with a 60° angle and a 5-mm radius of curvature. The fracture surface of all fragments was examined with a scanning electron microscope. The roughness of the working parts was quantified by using a profilometer and the micro-hardness test was carried out using a Vickers hardness tester. Results were statistically analyzed using a student´s t-test at a significance level of P < 0.05. Weibull analysis was also performed. XP-Endo Finisher presented significantly longer cyclic fatigue life than XP-Clean instruments (P<0.05). XP-Endo Finisher was able to withstand 1000% more cycles to fracture when compared to XP-Clean instruments. SEM visual inspection of the fracture surfaces revealed fractographic characteristics of ductile fracture in all tested instruments; wide-ranging forms of dimples were identified and no plastic deformation in the helical shaft of the fractured instruments was observed. When mean life was compared XP-Endo Finisher lasted longer than XP-Clean with a probability of 99.9%. XP-Endo Finisher instruments also exhibited significantly lower roughness than XP-Clean instruments (P<0.05). No differences in the micro-hardness was observed between the files (P>0.05). It can be concluded that XP-Endo Finisher instruments showed improved performance when compared with XP-Clean instruments, demonstrating higher cyclic fatigue resistance and lower roughness.

摘要 本研究旨在评估两款解剖型精修锉——XP-Endo Finisher与XP-Clean的循环疲劳性能，并同步检测两种锉的表面粗糙度形貌与显微硬度。实验将受试器械置于曲率半径5mm、弯曲角度60°的人工不锈钢根管模型中，通过记录断裂时间以评估其抗循环疲劳性能；采用扫描电子显微镜（Scanning Electron Microscope, SEM）观察所有断裂碎片的断面形貌；使用轮廓仪（profilometer）量化器械工作段的表面粗糙度，并采用维氏硬度计（Vickers hardness tester）开展显微硬度测试。统计学分析采用学生t（Student's t）检验，显著性水平设定为P<0.05，同时辅以威布尔（Weibull）分析。
结果显示，XP-Endo Finisher的循环疲劳寿命显著长于XP-Clean锉（P<0.05）；相较于XP-Clean锉，XP-Endo Finisher的抗断裂循环次数提升1000%。扫描电子显微镜对断裂面的观测结果表明，所有受试器械的断裂形貌均呈现延性断裂特征，可观察到多种形态的韧窝，且断裂器械的螺旋轴部未出现塑性变形。对比平均寿命时，XP-Endo Finisher的使用寿命长于XP-Clean的概率达99.9%。XP-Endo Finisher的表面粗糙度亦显著低于XP-Clean锉（P<0.05）；两款锉的显微硬度无显著统计学差异（P>0.05）。
综上可知，相较于XP-Clean锉，XP-Endo Finisher的性能更优，表现出更高的循环疲劳抗性与更低的表面粗糙度。