Comparison of cyclic fatigue resistance after using the single file system in root canals in extracted teeth in the presence of different irrigation solutions

Nickel-titanium rotary files are the most widely used systems during root canal treatment. Ni-Ti systems allow for faster and easier treatment times and more thorough irrigation of the root canal system. The main drawback of Ni-Ti systems is the fractures that occur for various reasons during use. The aim of this study is to compare the cyclic fatigue resistance and fractured fragment lengths of Reciproc Blue (RB, VDW, Munich, Germany) Ni-Ti single file systems after use in extracted teeth in the presence of different irrigation solutions. A total of 120 extracted lower first or second mabdibular molars were selected. Teeth were randomly divided into two groups depending on the irrigation solution (tooth, n= 60) and root canals were shaped with RB single file systems. Each file group consists of two subgroups according to the number of uses and the solution used: the first use group (file n= 15, tooth n= 15) (NaOCl-1 and EDTA-1) and the third use group (file n= 15, tooth n= 45) (NaOCl-3 and EDTA-3). In the control group, the files were subjected to cyclic fatigue testing without using any files (file n= 10). The cyclic fatigue resistance of the files was evaluated by the groove method. Data were evaluated with one-way analysis of variance, Kruskal Wallis test and Tukey test. While there was no statistically significant difference between the control and NaOCl-1 groups in terms of cycle numbers and break-up times (p >0.05), a significant difference was found between the control group and NaOCl-3, EDTA-1 and EDTA-3 groups (p<0.05). Although there was a decrease in cyclic fatigue between the NaOCl-1 and NaOCl-3 groups, this difference was not statistically significant. When the pairwise comparisons of the NaOCl and EDTA groups are evaluated, the decrease in the number of cycles and breakage times in the third use compared to the first use is not statistically significant. When the fracture length was evaluated, no significant difference was found between the groups. As a result, it was observed that the use of different irrigation solutions did not affect the cyclic fatigue of the files, fracture time and fracture fragment length. Keywords: cyclic fatigue, nickel titanium, single file systems, reciprocation, EDTA, NaOCl