Effect of Mg ion implantation on calcium phosphate formation on titanium

Magnesium (Mg) is the fourth abundant cation in the human body. In this work, Mg ions were implanted into titanium using a MEVVA (metal vapor vacuum arc) machine at a dose of 2 - 1017 ions/cm2 and an ion energy of 40 keV. Surface properties of the as-implanted titanium were studied by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). Bioactivity of the Mg-ion-implanted titanium samples was evaluated by immersing in SBF and compared with control (unimplanted) samples. After incubation for predetermined times, specimens were taken out and then analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to determine the presence of calcium–phosphate (Ca–P) deposits on the surface of titanium. The results show that hydroxyapatite (HAp) is found on the surface of the Mg-implanted titanium while no HAp exists on the unimplanted counterpart after incubation in SBF for up to 168 h. Our experimental results demonstrate that Mg ion implantation promotes HAp nucleation and growth on titanium from SBF. This indicates that implantation of Mg into titanium improves its bioactivity. The mechanisms of the improvement of Ca–P precipitation on the Mg-implanted titanium are discussed.