Effect of heat treatment on the cyclic fatigue resistance of NiTi endodontic openers

Aim: Aim of the present study is to evaluate if a thermal treatment adopted for endodontic NiTi instruments could increase their cyclic fatigue lifespan. Methods: 25 thermally treated One Flare (MM, Besancon, France) and 25 non-thermally treated Endo Flare (MM, Besancon, France) were mechanically rotated in a precurved artificial canal until fracture. Differences between Time to Fracture (TTF) and Fragment Length (FL) were statistically analyzed (Student's t test, (p<0.05). Results: One Flare's time to fracture (47.24 seconds; SD +/- 4.24) was significantly longer when compared to Endo Flare's (21.2 seconds; SD +/- 3.08) at the same operating conditions (p<0.005). Differences between the length of fractured segments showed no statistical significance differences (p>0.005). Conclusions: Heat treated NiTi alloy showed an improved time to fracture when compared to a non-thermally treated one at the same operating conditions. Thermal treatments could enhance the characteristics of NiTi improving the lifespan of rotary endodontic instruments.