Improvement of surface bioactivity on titanium by water and hydrogen plasma immersion ion implantation.

We have investigated the surface bioactivity of titanium after water and hydrogen plasma immersion ion implantation. Plasma immersion ion implantation (PIII) excels in the surface treatment of components possessing a complicated shape such as medical implants. In addition, water and hydrogen PIII has been extensively studied as a method to fabricate silicon-on-insulator (SOI) substrates in the semiconductor industry and so it is relatively straightforward to transfer the technology to the biomedical field. In our investigation, water and hydrogen were plasma-implanted into titanium sequentially. Our objective is that water PIII introduces near-surface damages that trap hydrogen implanted in the subsequent step to improve the surface bioactivity while the desirable bulk properties of the materials are not compromised. Ti-OH functional groups can be detected on the (H(2)O+H(2))-implanted titanium surface by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. After incubation in simulated body fluids (SBF) for cytocompatibililty evaluation in vitro, bone-like hydroxyapatite was found to precipitate on the (H(2)O+H(2)) implanted samples while no apatite was found on titanium samples plasma implanted with water or hydrogen alone. Human osteoblast cells were cultured on the (H(2)O+H(2))-implanted titanium surface and they exhibited good adhesion and growth. Our results suggest a practical means to improve the surface bioactivity and cytocompatibility of medical implants made of titanium.