Torsional fatigue strength of reciprocating and rotary pathfinding instruments manufactured from different NiTi alloys

Abstract To evaluate the torsional properties of engine-driven pathfinding instruments manufactured from different NiTi alloys – R-Pilot (tip size 12.5;.04 taper; M-Wire) and One G (tip size 14;.03 taper; Conventional NiTi). A total of 40 NiTi instruments from engine-driven pathfinding instruments (n = 20) were used. The torsion tests followed ISO 3630-1 (1992). Three millimeters of each instrument tip was fastened to a small load cell by a lever arm linked to the axis of torsion. During the test, the torsion testing machine software measured the maximum torsional strength and angle of rotation (0) before instrument failure. The fractured surface of each instrument was assessed by scanning electron microscopy (SEM). In addition, a supplementary examination was performed to measure the cross-sectional area and the metal mass volume of each instrument 3 mm from the tip. Data were analyzed using a t-test, with significance level set at 5%. R-pilot had significantly higher torsional strength than did One G (p < 0.05). Regarding the angle of rotation to fracture, One G had higher angles than did R-Pilot (p < 0.05). The supplementary examination showed that R-Pilot had the highest cross-sectional area and volume of metal mass at 3 mm from the tip (p < 0.05). R-pilot (M-Wire NiTi alloy) had a significantly higher torsional strength and One-G (superelastic NiTi alloy) had the highest angle of rotation to fracture.

摘要 本研究旨在评估两种不同镍钛（NiTi）合金制成的机用根管探查器械的扭转性能：分别为R-Pilot（尖端尺寸12.5；锥度0.04；采用M-Wire工艺）与One G（尖端尺寸14；锥度0.03；采用传统镍钛合金）。本研究共纳入40件机用根管探查器械，每组各20件。扭转试验严格遵循ISO 3630-1（1992）标准开展。将每根器械尖端3mm区段通过连接扭转轴的杠杆臂固定于小型测力传感器上，试验过程中扭转试验机软件可记录器械断裂前的最大扭转强度与扭转角度（θ，原文笔误为0）。采用扫描电子显微镜（SEM）对每根器械的断裂断面进行形貌分析。此外，本研究补充检测了器械尖端3mm处的横截面积与金属体积。数据采用t检验进行统计学分析，显著性水平设定为5%。研究结果显示，R-Pilot的最大扭转强度显著高于One G（p < 0.05）；在断裂扭转角度方面，One G的扭转角度显著大于R-Pilot（p < 0.05）。补充检测结果表明，R-Pilot在尖端3mm处的横截面积与金属体积均显著更高（p < 0.05）。综上，采用M-Wire镍钛合金的R-Pilot具备更优异的扭转强度，而采用超弹性镍钛合金的One G则拥有更高的断裂扭转角度。