Assessment of surface topographic changes of nickel–titanium rotary endodontic file at repeated usage: An in vitro study

Abstract

Aim: The current in vitro study aimed to assess the surface topography of Protaper gold NiTi files and compare changes in surface topography before and after root canal preparation in straight, moderately, and severely curved root canals. Methods: In this study, thirty Protaper gold S1 files were selected. These were divided into three groups of 10 each and were used to prepare 440 straight, moderately, and severely curved root canals. Optical profilometry was used to perform qualitative evaluations of file surfaces before and after root canal preparation at specified intervals. The statistical analysis was performed using the Mann–Whitney U-test for comparing two groups, the Friedman test for comparing within groups, the Kruskal–Wallis analysis of variance for multigroup comparisons, and the Bonferroni test for multiple pairwise comparisons. Results: The surface irregularities in the form of cracks and microcavities were higher in the used files when compared to the unused files. Similarly, the files used in severely curved canals exhibited more surface alterations at less no of uses when compared to the files used in straight and moderately curved canals. The difference obtained was statistically significant, that is, P = 0.000. Conclusion: From the findings, it was concluded that the file separation has been preceded with surface deterioration as a result of repeated cycles of cyclic fatigue.