Aim: Many factors can affect the cyclic fatigue resistance of nickel-titanium files. Nickel-titanium can exist in a soft martensitic state, which improves its cyclic fatigue resistance. The alloy transforms from the austenite to martensite state at a certain temperature, and various factors can modify this transition temperature. Temperature affects the state of the metal; therefore, the way the file behaves at intracanal temperature is significant. The present review aims to gather evidence to show that martensitic files display increased cyclic fatigue resistance compared to conventional files.
Keywords: blue files, cyclic fatigue, EDM files, gold files, intracanal temperature, martensitic
Materials and methods: A population, intervention, comparison, outcomes and study framework was used to formulate the review question and develop the inclusion and exclusion criteria. The search was conducted using the databases Science Direct, Wiley, PubMed and Google Scholar. A single reviewer screened the results, applying the inclusion and exclusion criteria. The results were analysed. The Joanna Briggs Institute Checklist for Cohort Studies was used to assess the quality of the studies. The primary studies and review process were assessed for bias.
Results: A total of 642 studies were screened and 22 studies were included. The overall quality of the included studies was judged as moderate.
Conclusions: Within the limitations of this study, it was found that the Hyflex EDM file (Coltène/ Whaledent, Altstätten, Switzerland) is martensitic at intracanal temperature and has higher cyclic fatigue resistance than the other martensitic phase files.