Effect of sodium hypochlorite on the cyclic fatigue resistance: A scanning electron microscopy evaluation

The main purpose of this study was to compare the cyclic fatigue resistances of the three different nickel–titanium files in 2.5% sodium hypochlorite solution and distilled water at physiologic intracanal temperature (35°C). Three NiTi files such as One Curve (OC) (Micro-Mega, Besancon, France), OneShape (OS) (Micro-Mega), and Protaper Next (PTN) X2 (Dentsply Sirona, Ballaigues, Switzerland) were tested for cyclic fatigue resistance inside artificial stainless steel canal block with curvature 60° and 5 mm radius. The block was fixed inside a hot water bath of distilled water or 2.5% sodium hypochlorite and the temperature was set at 35 ± 1°C. The number of cycles to fracture data were recorded and all the fracture surfaces of files were evaluated by using scanning electron microscopy. The number of cyclic to fracture data were analyzed statistically via Kruskal–Wallis and Mann–Whitney U tests. OC showed the highest cyclic fatigue resistance at distilled water while PTN X2 showed the lowest cyclic fatigue resistance at 2.5% sodium hypochlorite. When cycling fatigue test medium were changed from distilled water to sodium hypochlorite solution, the resistance of the files to cyclic fatigue were decreased. SEM analysis confirmed that all scanned samples were fractured due to cyclic fatigue. The OC rotary instruments have more cyclic resistance than OS and PTN X2. The sodium hypochlorite solution reduces the resistance of the rotary instruments. © 2019 Wiley Periodicals, Inc

Cyclic fatigue and energy-dispersive X-ray spectroscopy examination of the novel ROTATE instrument

To investigate the cyclic fatigue resistance of novel ROTATE instruments and to compare with the same size of One Curve, TF adaptive, and Mtwo instruments using a root canal simulation model. Four-type of 25/0.06 instruments were used: ROTATE, Mtwo, One Curve, TF adaptive. Instruments were divided into two subgroups: Distilled water and 2.5% sodium hypochlorite (n = 20). Instruments were operated at 35°C. The time to fracture and the length of the fractured fragments were compared One-way analysis of variance (ANOVA) followed by Tukey's multiple comparison tests (p <.05). Descriptive analysis was performed for the elemental composition of instruments by Energy-dispersive X-ray spectroscopy. ROTATE demonstrated the lowest Ni content and SD values. ROTATE had significantly higher NCF values than other groups (p <.0001). Sodium hypochlorite was decreased the mean NCF values. This is the first study in the literature on the cyclic fatigue of ROTATE. ROTATE presented higher cyclic fatigue life than One Curve, TF Adaptive, and Mtwo. © 2019 Wiley Periodicals, Inc