Preparation of Titanium–Calcium Alloy Films and Evaluation of Hydroxyapatite Formation Ability

Ti implants used for the treatment of bones and teeth damaged by diseases and accidents must exhibit excellent bone-bonding ability. To develop novel Ti alloys with bone-bonding ability superior to that of conventional Ti alloys, we prepared alloy films of Ti and Ca, especially Ca is an essential element in the human body and the inorganic components of bones, via radio-frequency magnetron sputtering. Ti–Ca alloy films with various Ca concentrations were fabricated using different arrangements of Ti and Ca sources. The crystal and surface structures as well as in vitro bone-bonding ability of Ti–Ca alloy films with Ca concentrations of 6, 27, and 38 mass% were investigated. X-ray diffraction patterns revealed that the abovementioned Ti–Ca alloy films exhibit an amorphous structure. Results of X-ray photoelectron spectroscopy revealed that oxides and hydroxides of Ti and Ca were present on the surfaces of the Ti–Ca alloy films. In a simulated body fluid (SBF) immersion test, hydroxyapatite precipitated first on the surface of the Ti–27 mass%Ca alloy film, whereas the Ti–38 mass%Ca alloy film peeled off during immersion in the SBF solution.