Abstract
OBJECTIVE: To evaluate the effects of deionised water, blood, phosphate-buffered saline (PBS) and a new anti-corrosive solution based on methoxy propyl amine (MOPA) on the cyclic fatigue resistance of endodontic NiTi rotary instruments under in vitro conditions. METHODS: Forty ProTaper F1 files were provided and divided to four groups (n=10). Samples were first autoclaved and then stored in deionised water, blood, PBS or MOPA for 24 hours. Cyclic fatigue was tested with a custom-made stainless-steel block including artificial canals (curvature angle=30 degree, radius of curvature=5 mm). After immersion in test solutions, samples were rotated 300 rpm until fracture occurred. The number of cycles to failure (NCF) was calculated using recorded fracture time. RESULTS: Data were analysed by the Kolmogorov-Smirnov, Levene, ANOVA and Scheffe statistical tests. Samples in blood group showed the lowest and samples in MOPA group showed the highest NCF values. Significant difference was observed between groups (P=0.001). NCF value of PBS group was significantly more than the NCF values of samples in blood and deionised water groups (P<0.05). CONCLUSION: The tested novel anti-corrosive solution significantly increased the fracture resistance of the endodontic NiTi rotary instruments by reducing the cyclic fatigue. In contrast, blood and deionised water caused more corrosion and resulted in earlier file fracture.