The effect of the number of sterilizations on the fracture resistance of niti canal files fabricated i̇n different qualities

Objective: The aim of this study was to compare the relationship between the number of autoclave sterilisations and fracture resistance of two different generations of NiTi canal instruments, one with and one without CE certification. Materials and Methods: This study was carried out in the research laboratory of Ondokuz Mayıs University, Faculty of Dentistry. A total of 128 nickel-titanium root canal files were used in the study. Two different generations of CE-certified (ProTaper Universal, AF Blue R3 File) and non-CE-certified root canal files (G-Super Gold file, G-One Blue file) were evaluated. The files were divided into four groups of 8 files in each group to measure their fracture resistance. Each subgroup was categorised according to the number of autoclave sterilisations (n=8). The fracture test was performed using a stainless steel artificial canal, and the number of cycles at fracture and the length of the broken fragments were recorded. The data obtained were evaluated by appropriate statistical analysis methods. Results: The fracture resistance of conventional NiTi files was higher than that of M-Wire files. CE certified files were found to have a higher fracture resistance than non-CE certified files. Accordingly, the fracture resistance of the ProTaper file was high. As the number of sterilizations increased, the fracture resistance of all groups of NiTi root canal files decreased. After the 4th sterilization, a significant decrease was seen in all file groups. The AF Blue R3 file had the lowest fracture resistance while the AF Blue R3 file had the highest fracture resistance. In terms of broken file length, Protaper universal was found to be the most abundant. Conclusion: The potential for fracture in canal preparation processes is high due to the higher fracture resistance of conventional files and non-CE certified files. A significant decrease was seen after the fourth sterilization cycle. Keywords: NiTi files, number of Sterilization, Fracture Resistance, CE Certification.