Comparison between a Novel Nickel-Titanium Alloy and 508 Nitinol on the Cyclic Fatigue Life of ProFile 25/.04 Rotary Instruments

ProFile(R) 25/.04 instruments manufactured from three variants of Nitinol (1A, 1B & 2AS) were compared with stock production ProFile 25/.04 instruments and fatigue tested to failure. Cyclic fatigue testing was performed by rotating instruments at 300 RPM in a simulated steel root canal with 5 mm radius and 90 degrees curve until instrument separation. Time to failure was recorded. Torsion testing was undertaken by clamping 3 mm of each instrument tip between brass plates and rotating it at 2 RPM until failure. Data were recorded for torque and angle at fracture. Statistical differences were found with nickel-titanium variant 1B (M-Wire(TM) NiTi) nearly 400% more resistant to cyclic fatigue than stock ProFile 25/.04 (P<.001). Torsion testing found differences between all 508 Nitinol groups and M-Wire(TM) NiTi (P<.001). ProFile 25/.04 files manufactured from M-Wire(TM) NiTi have significantly greater resistance to cyclic fatigue while maintaining comparable torsional properties. (J Endod 2008;34:1406-1409)