Evaluation of the Impact of Raw Materials on the Fatigue and Mechanical Properties of ProFile Vortex Rotary Instruments

Introduction: In this in vitro study, raw materials (including stainless steel, conventional superelastic nickel-titanium [NiTi], M-Wire NiTi, and Vortex Blue NiTi) were used to create Profile Vortex designed 25/.06 instruments and subject these instruments to testing for fatigue resistance, torsional properties, flexibility, and Vickers microhardness. The comparative results in this study will enable the clinician's understanding of the performance of these materials for better choices in application during endodontic procedures. Methods: Cyclic fatigue testing was performed by rotating files in an artificially constructed stainless steel canal with a 5-mm radius and a 90 degrees angle of curvature at 500 rpm. Torsional properties and flexibility in bending were assessed according to specification ISO 3630-1. Vickers microhardness was measured on the cross section of instruments with 300-g load and 15-second dwell time. Results: There were significant differences in the average fatigue life and flexibility for instruments made of different materials (P < .05). Vortex Blue was ranked first in both fatigue and flexibility, followed by M-Wire, superelastic wire, and stainless steel. For torsional strength and microhardness, stainless steel and M-Wire were ranked first and second, respectively. There was no statistically significant difference between superelastic wire and Vortex Blue. Vortex Blue showed the greatest distortion angle at break, whereas the other 3 materials showed comparable degree of rotation in the torque test. Conclusions: Under the limitations of this study, NiTi shape memory alloy appeared to be a superior material option compared with stainless steel for its use in the application of endodontic rotary instruments. Vortex Blue and M-Wire offered functional advantages over conventional superelastic NiTi. Vortex Blue showed improved fatigue resistance and flexibility compared with Pro File Vortex M-Wire. (J Endod 2012;38:398-401)