Cyclic Fatigue Resistance of Biorace Nickel-titanium File with Variable Taper after Immersion in Sodium Hypochloride

Abstract

Objective: This study aimed to evaluate the effect of sodium hypochlorite on the cyclic fatigue resistance of BioRace (BR) files according to taper. Methods: BR 25.04 and 25.06 files woe divided into the following groups: group 1, 20 BR 25.04 with no immersion in NaOCl; group 2, 20 BR 25.04 with immersion in 5.25% NaOCl at 37 degrees C +/- 1 degrees C for 5 min; group 3, 20 BR 25.06 with no immersion; and group 4, 20 BR 25.06 with immersion in 5.25% NaOCl at 37 degrees C +/- 1 degrees C for 5 min. The instruments were applied to a stainless-steel artificial root canal of 60 degrees curvature and 5-mm radius. The time to failure (TTF) in seconds and number of cycles to failure (NCF) were recorded. Results: The cyclic fatigue resistance of BR 25.04 was significantly higher than that of BR 25.06. The TTF and NCF values were significantly higher in group 1 than in groups 2 and 3 and in group 2 than in group 4. However, neither value differed significantly between groups 3 and 4 (p>0.05). Conclusion: Taper and sodium hypochlorite affected the cyclic fatigue resistance of BR.