Fatigue resistance of ProTaper gold exposed to high-concentration sodium hypochlorite in double curvature artificial canal

This study aimed to evaluate and compare the fatigue resistance of ProTaper Gold(PTG)and ProTaper Universal(PTU)in artificial single and double curvature canals in 5%sodium hypochlorite(NaOCl)at body temperature(37℃).PTG and PTU files(size F1)were subjected to fatigue tests in two different artificial ceramic canals.The single curvature model had a 60°curvature angle with a 5mm radius.The double curvature model had a 60°curvature angle with a 5mm radius and a second 30°curvature with a 2mm radius.A file segment was introduced into the artificial canal and immersed in water or 5%NaOCl at 37℃.The total number of cycles to fracture(NCF)was recorded.Data were analyzed using t-test and linear regression analysis.The NCF of all files was significantly influenced by the type of NiTi metal alloy(P<.01),canal curvatures(P<.01),and the environmental conditions(P<.05).PTG had higher fatigue resistance than PTU files in both single and double curvature canals(P<.05).The NCF of PTU files in 5%NaOCl was shorter than that in water(P<.05).The mean length of broken PTG was significantly shorter than those of PTU files in both single and double curvature canals(P<.01).The fatigue performance of PTG is better than that of PTU in both single and double curvature.Environmental conditions may affect the fatigue behavior of PTU files with single curvature.