Evaluation of surface alterations in two nickel-titanium files following repeated use: A scanning electron microscopy study

This study aimed to assess surface alterations of two nickel-titanium files with different cross-sections, before and after multiple uses, using Scanning Electron Microscopy (SEM). A total of 120 S-shaped artificial canals were used to examine the surface alterations of X-Never Break X2 (EasyInSmile International Corp., Changsha, China) (<i>n</i> = 10) and JIZAI I (Mani, Tochigi, Japan) (<i>n</i> = 10) files. These changes were analyzed using SEM before use and after the first, third, and sixth use. The files underwent sterilization and cleaning after each use, and surface alterations such as microcracks, tip deformation, surface pitting, and debris were observed. SEM images were captured at different magnifications (×100, ×250, ×500, and ×1000) before and after use. These images were examined by two independent observers to assess the presence of deformations and debris on their surfaces. Both files showed a proportional increase in surface alterations with the number of uses. While microcracks and tip deformation were more prominent in the X-Never Break X2 files with continued use compared to the JIZAI I files, surface pitting was more frequently observed in the JIZAI I files. The significant increase in surface alterations after the third use suggests that continuing to use the files beyond this point could potentially lead to fractures. These surface alterations were more pronounced in the X-Never Break X2 group compared to the JIZAI I group.