Effect of nitriding surface treatment on the corrosion resistance of dental nickel-titanium files in 5.25% sodium hypochlorite solution

This study investigated the effect of nitriding surface treatment on the corrosion resistance of commercial dental alloy, in the form of helical nickel-titanium (Ni-Ti) files, when treated with 5.25% sodium hypochlorite (NaOCl) solution. The surface of dental helical Ni-Ti files was modified using nitriding treatment at 200 degrees C, 250 degrees C and 300 degrees C in an NH3-containing environment. The surface morphology and chemical composition of the Ni-Ti files were analyzed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The corrosion resistance of the Ni-Ti files when treated with a clinical solution of 5.25% NaOCl was evaluated using the linear polarization method and by potentio-dynamic polarization curve measurement. The nitriding treatments at different temperatures created titanium nitride (TiN) on the surface of the helical Ni-Ti files. The Ni-Ti files nitrided at 200 degrees C and 250 degrees C showed higher polarization resistance and higher passive film breakdown potential together with a lower passive current than untreated files. The presence of TiN on dental Ni-Ti files significantly increased the corrosion resistance of the files in the presence of 5.25% NaOCl solution. (C) 2008 Elsevier B.V. All rights reserved.