Electrochemical induced dissolution of fragments of nickel–titanium endodontic files and their removal from simulated root canals

AIM: To improve the dissolution process of NiTi endodontic rotary files aiming at fragment removal and the recovery of the original path of the root canal during a clinically acceptable period of time. METHODOLOGY: Anodic polarization curves and redox curves were obtained to determine the conditions necessary for the dissolution of endodontic files. Anodic polarization of K3 files was performed, and analysis of variance (P < 0.05) was used to compare different test times in relation to weight loss, length loss and electrical charge generated in each solution. The polarization of fragments in simulated root canals was undertaken to evaluate the dissolution process. After the tests, a size 10 K-file was used to verify the possibility to bypass the fragment. The total electrical charge of each test was obtained from the corresponding graph area. Radiographic analysis of the simulated canals was used before and after the tests to verify fragment dissolution. RESULTS: The weight loss values, the length loss values and the total values of electrical charge in each period of time were significantly higher (P < 0.05) in the tests using the selected solution compared with the solution previously proposed. A progressive consumption of the K3 file tip was observed up to 30 min. The anodic polarization of file fragments in simulated root canals for 60 min resulted in their partial dissolution and enabled the recovery of the original canal pathway with size 10 K-files. CONCLUSIONS: Increasing fluoride concentration resulted in greater active dissolution of NiTi files. The dissolution of fractured files in simulated root canals enabled the recovery of its original path during a clinically acceptable period of time.