A Review of Conventional DSC Investigations of Phase Transformations in New and Used Nickel-Titanium Rotary Endodontic Instruments

摘要

Nickel-titanium rotary instruments are highly important for clinical endodontics becausernof their much greater flexibility compared to instruments manufactured from stainless steel. Thernclinical use and manufacturing process for these instruments is described. The merit of havingrnthe nickel-titanium rotary instruments in the superelastic condition is discussed in terms of thernphase transformation process under stresses encountered during the instrumentation of rootrncanals. Conventional DSC has been performed from –125℃ to 100℃ and back to–125℃ onrnnickel-titanium rotary instruments from two major manufacturers in both the as-receivedrncondition and after simulated clinical use. These studies have shown that the as-receivedrninstruments are in the superelastic condition and that they remain in the superelastic conditionrnafter clinical use, although remarkable changes occur in the phase transformation processes.rnComplementary Vickers hardness measurements have failed to detect evidence of workrnhardening in the tip regions of similar rotary instruments after clinical use.