Nitrogen plasma immersion ion implantation treatment to enhance corrosion resistance, bone cell growth, and antibacterial adhesion of Ti-6Al-4V alloy in dental applications

Ti-6Al-4V is a biocompatible alloy widely used for dental prostheses. Unfortunately, the oxide film that forms spontaneously on the surface is bioinert and sometimes prone to the release of metal ions. In this study, we applied nitrogen plasma immersion ion implantation (N-PIII) treatment to Ti-6Al-4V in order to improve corrosion resistance and biological responses, including cell growth and antibacterial adhesion, for dental applications. We then analyzed the surface characteristics, such as topography, chemical composition, hardness, and hydrophilicity. Resistance to corrosion was examined using potentiodynamic polarization curves obtained in artificial saliva, simulated body fluid, and simulated blood plasma solutions. Human bone marrow mesenchymal stem cells were used to test cell responses, including adhesion, proliferation, and mineralization. The oral bacteria, Streptococcus salivarius, was used to evaluate antibacterial adhesion, including bacterial attachment and morphology. Our results demonstrate that N-PIII treatment did not significantly affect surface roughness at the macroscopic (micrometer) scale or hydrophilicity. During N-PIII treatment, a thin film of TiN (