Surface Alterations Induced on Endodontic Instruments by Sterilization Processes, Analyzed with Atomic Force Microscopy: A Systematic Review

Endodontic canal disinfection procedures that use sodium hypochlorite, and subsequently, heat sterilization procedures can alter the surface of endodontic instruments, described as corrosion and micropitting. These phenomena can be visualized on the surface of the instruments by SEM and atomic force microscopy analyses. The endodontic instruments used in probing, pre-enlargement, and shaping phases are made of steel alloy or nickel-titanium alloy (NiTi) and are subject to torsional, flexor, and cyclic fatigue; indeed, reuse of these instruments must be done with the knowledge that these instruments are subject to fracture following stress caused during their use. Fracture of the instrument within the canal is an eventuality that can lead to failure of the treatment, and therefore it is important to try to reduce situations that can contribute to the fracture. This review was performed based on the PRISMA protocol. Studies were identified through bibliographic research using electronic databases. A total of 1036 records were identified on the PubMed and Scopus databases. After screening the articles, restricted by year of publication (1979 to 2019), there were 946 records. With the application of the eligibility criteria (all the articles pertaining to the issue of sterilization in endodontics), there were 228 articles. There were 104 articles after eliminating overlaps. There were 50 articles that discussed the influence of sterilization procedures on the surface characteristics of endodontic instruments, and 26 articles that measured parameters on surface alteration. Applying the inclusion and exclusion criteria resulted in a total of eleven articles for quantitative analysis. Four articles were in reference to the primary outcome, eight articles to secondary outcome, and five articles to tertiary outcome. The meta-analysis showed a statistically significant surface alteration effect after five autoclaves and after immersion in the canal irrigants after 10 min