Cyclic fatigue of Profile rotary instruments after simulated clinical use

Aim The purpose of this study was to evaluate cyclic fatigue of Profile Ni- Ti rotary instruments (PRIs) after dry heat sterilization and up to 10 time s simulated clinical use, Methodology Instruments of size 40-15 were used in a crown-down technique. Three groups were included in this study, In groups 1 and 2, each set of in struments was used in five and 10 canals, respectively, Group 3 was the con trol group. NaOCl at a concentration of 2.5% was used as an irrigant. Each set of instruments was sterilized before each use. Results The PRI size 40 demonstrated the lowest incidence of rotations to b reakage. One-way analysis of variance and Tukey's HSD test showed statistic ally significant differences among different file sizes within each group. Conclusions The results showed that dry heat sterilization and simulated cl inical use in the presence of NaOCl did not lead to a decrease in the numbe r of rotations to breakage of the files.