Calcium phosphate films with/without heat treatments fabricated using RF magnetron sputtering

Calcium phosphate coating films were fabricated on blast-treated titanium plates and screw-type titanium implants using RF magnetron sputtering. A uniform and dense coating film with a thickness of 0.5 μm could cover the blast-treated titanium plate efficiently, maintaining the surface roughness of the substrates. The as-sputtered coating films consisted of amorphous calcium phosphate (ACP) or oxyapatite (Ca₁₀(PO₄)₆O, OAp). Heat treatments of the OAp coating films were conducted in a silica ampoule or in air, and it was observed that the crystallinity of the coating films increased after the heat treatment. The bonding strength between the as-sputtered coating films, subjected to heat treatment in air, and the blast-treated titanium plates exceeded 60 MPa. An immersion test was conducted and alkaline phosphatase (ALP) activity of osteoblasts was investigated in vitro. The dissolution rate of the coating films in the 0.9% NaCl solution decreased with an increase in their crystallinity. The ACP coating film exhibited high ALP activity. As the in vivo evaluation, the coated and non-coated titanium implants were implanted into the femur of Japanese white rabbits. The percentage of bone-implant contact and the removal torque value of the coated titanium implants were greater than those of the non-coated titanium implants.