Evaluation of the effect of different irrigation solutions on the microhardness of heat-treated nickel-titanium files: An in vitro study

The aim of this study was to evaluate the effect of different irrigation solutions used during root canal irrigation in root canal treatment on the microhardness of nickel-titanium (NiTi) files subjected to different heat treated. The pre-preparation microhardness levels of EndoArt Smart Blue and EndoArt Smart Gold (İnci Dental Productions Co, Istanbul, Turkey) file systems were measured at five different points using a microhardness testing device (HMV-2000; Shimadzu, Tokyo, Japan). Microhardness evaluation was performed on thirty-two 30.04 files from each file system. A total of 64 single-rooted and single-canaled mandibular incisor teeth were prepared up to size 30.04 using file systems. The preparation was completed with the irrigation solutions (5.25% NaOCl, 17% EDTA, ozonated water, and distilled water) for an average of 3 min with a 30.04 file. After preparation, the microhardness levels of the 30.04 files were again measured. The differences between the microhardness values were statistically compared. According to the obtained data, the pre-preparation measurement values were higher than the post-preparation values (p < 0.05). No statistically significant differences were found between the microhardness measurement values (p > 0.05). The highest and lowest microhardness changes were observed in the EndoArt Smart Blue file system, in the ozonated water (195.63 ± 71.04 VHN (Vickers Hardness Number)) and distilled water (152.88 ± 51.10 VHN) groups, respectively. In this study, different irrigation solutions did not have a statistically significant effect on the microhardness of heat-treated NiTi files.