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.

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Introduction: A recent study presented the concept of an electrochemical-induced dissolution technique of fractured instruments. The purpose of this study was to test the ability to dissolve embedded fragments of K3 nickel-titanium (NiTi) files. The surface of the fragment exposed to the electrolytic solution was the main parameter evaluated as an interfering factor on the dissolution process. Methods: Three types of K3 NiTi 30.06 file fragments were produced, resulting in different exposed cross-section areas. Anodic current was recorded and used as a reference to evaluate the dissolution process of the fragments. Analysis of variance (P < .05) was used to compare the total electrical charge obtained from current versus time records among the fragments of the 3 groups. Radiographic analysis was carried out before and after the tests to observe the extension of dissolution achieved. Results: The total electrical charge values generated during the tests evidence a statistical difference among the 3 groups of fragments (analysis of variance, P < .05). The larger is the diameter of the exposed surface cross section, the higher is the total value of electrical charge. The radiographic images obtained before and after the tests showed a significant reduction of the fragment length as a result of the polarization imposed. Conclusions: The results presented here showed that it is possible to obtain a significant dissolution of K3 NiTi endodontic instrument fragments. The diameter of the surface of fragment exposed to the medium affects the current levels used to promote the dissolution. (J Endod 2011;37:526-530)

The anodic polarization of K3, ProTaper and MTwo instruments resulted in their progressive consumption with increasing polarization time. Sixty minutes anodic polarization of the various NiTi instrument fragments in simulated root canals resulted in their partial dissolution.

The [NaF 12 g L + NaCl 1 g L ] solution did not alter dentine microhardness or damage the dentine structure. It also demonstrated lower cytotoxicity than NaOCl.

A 60-min anodic polarization of stainless steel K-file fragments in simulated root canals resulted in their partial dissolution. The fragments could be bypassed after the test.

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