Electrochemical-induced dissolution of nickel-titanium endodontic instruments with different designs

To compare the active dissolution process of K3, ProTaper and Mtwo NiTi endodontic rotary instruments in chloride and fluoride containing solutions.

Anodic polarization of K3 size 20, 0.06 taper, ProTaper size F1 and MTwo size 20, 0.06 taper instruments was performed, and anova (P < 0.05) was used to compare the weight loss, the time of dissolution and the electrical charge generated by the groups of instruments. Fragments of the instruments were polarized in simulated root canals to evaluate the dissolution process. After the tests, a size 10 K-file was used to verify whether the fragment could be bypassed. Radiographic analysis of the simulated canals was used before and after the tests to verify fragment dissolution.

A progressive consumption of the instruments was observed. K3 and ProTaper instruments had significantly greater weight loss than Mtwo instruments after 30 min of polarization. K3 instruments had the highest values of total electrical charge, and MTwo instruments the lowest (P < 0.05). After 60 min, the anodic polarization of instrument fragments in simulated root canals resulted in their partial dissolution.

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.