Electrochemical dissolution of rotary M-Wire instrument fragments of different sizes

Objective: The purpose of this study was to evaluate the ability of a solution containing fluoride to dissolve rotary instrument fragments in a simulated root canal within a maximum of 60 min. Material and methods: Eighteen M-Wire alloy rotary instruments were divided into three experimental groups according to length. An electrochemical cell was prepared in the canals with three electrodes, and file fragments were immersed in fluoride solution. A constant anodic potential of 800 mV was applied. Statistical analysis was performed using the non-parametric Wilcoxon test for paired data. Group means were compared by ANOVA for normally distributed variables, and with the Kruskal-Wallis and Jonckheere-Terpstraen tendency tests for variables that were not normally distributed. The level of statistical significance was set at P 0.005. Results: A significant loss of weight was observed, which increased with initial fragment weight (P 0.001). Complete (n = 3) or almost complete dissolution of 5.0 mm and 10.0 mm file fragments was achieved. The average weight reduction was 36% for 17.0 mm file fragments. The anodic potential was correlated positively with the degree of weight loss (r = 0.85, P 0.001). Conclusion: The electrochemical method enabled significant dissolution of NiTi instrument fragments within a maximum of 60 min. Keywords: active dissolution, endodontic instruments, fracture, nickel-titanium