Comparison of dynamic cyclic fatigue resistance of Reciproc(r) Blue and WaveOne(r) Gold after sterilization and/or immersion in sodium hypochlorite

Background: This study aims to compare the cyclic fatigue resistance (CFR) of the Reciproc Blue and WaveOne Gold instruments under a dynamic cyclical fatigue test. Material and Methods: 210 Reciproc Blue “R25” and WaveOne Gold “primary” files were assigned into 7 groups (n =15) for each brand. Groups G: Files were not exposed to NaOCl or sterilization. Groups A and D: files were immersed for 3 minutes in NaOCl 1 and 3 times, respectively. Groups B and E: Files were autoclaved 1 and 3 times, respectively. Groups C and F: files were exposed to both, NaOCl immersion and autoclaving 1 and 3 times, respectively. Subsequently, files underwent a dynamic CFR test. The chemical composition of the files’ surface from Group G was analysed by energy-dispersive X-ray spectroscopy (EDS). Cyclic fatigue resistance time was statistically analysed using 1-way and 2-way analyses of variance (ANOVA) and T-test. A p-value ≤0,05 was set to be statistically significant. Results: There was a significantly higher CFR of RB files than WOG in groups A, B, C, D and G (p<0.05). WOG files were superior to RB in group E (p<0.05). There were no statistically significant differences between files in group F (p˃0.05). RB files from groups B, C, D, E and F had significantly lower resistance than new ones (Group G) (p<0.05). WaveOne Gold files exposed to 5 % NaOCl immersion in combination with sterilization cycles (Groups C and F) had significantly lower CFR than new ones (p<0.05). Reciproc Blue and WaveOne Gold NiTi alloys differed in atomic wt % of carbon, oxygen, nickel and titanium. Conclusions: The Reciproc Blue files outperformed the WaveOne Gold files in terms of CFR. The Reciproc Blue files were more vulnerable to the cycles of NaOCl immersion or autoclave sterilisation. The combined autoclaving and NaOCl cycles had the most significant impact on the mechanical properties of both files.