Cryogenic treatment of martensitic shape memory nickel titanium alloy for the enhancement of cyclic fatigue life of rotary endodontic instruments

Abstract

In this study the effect of dry cryogenic treatment on the microstructure and mechanical properties of Ni51Ti49 martensitic shape memory SM nickel titanium NiTi alloy was investigated in vitro Various metallurgical laboratory techniques SEM EDS DSC optical microscope SEM XRD Vickers hardness test and reciprocatory sliding wear test were employed to verify and characterize the Ni51Ti49 martensitic SM alloy Based on the results of the initial characterization experiments the HyflexCM martensitic SM NiTi rotary endodontic instruments were subjected to deep cryogenic treatment DCT and their mechanical behavior was comparatively evaluated and confirmed in artificial and natural root canals. DCT with 24 hours soaking time increases the volume of martensite which in turn increases the shape memory property of Ni51Ti49 alloy The cyclic fatigue life of martensitic SM NiTi rotary instrument is enhanced up to 13 percentage per instrument following DCT for 24 hours and reduces the risk of instrument fracture newline