Fabrication and evaluation of calcium phosphate coating films on blast-treated Ti-6Al-4V alloy substrate

Calcium phosphate coating films were fabricated on Ti-6Al-4V alloy plates and implants with a blast-treated surface using radiofrequency (RF) magnetron sputtering and were evaluated in vitro and in vivo. Amorphous calcium phosphate (ACP) and oxyapatite (OAp) films obtained in this study could cover the blast-treated Ti-6Al-4V substrate very efficiently, maintaining the surface roughness. For the in vitro evaluations of the calcium phosphate coating films, bonding strength and alkaline phosphatase (ALP) activity were examined. The bonding strength of the coating films to a blast-treated Ti-6Al-4V plate exceeded 60 MPa, independent of film phases. When compared with an uncoated Ti-6Al-4V plate, the increase in the ALP activity of osteoblastic SaOS-2 cells on a blast-treated Ti-6Al-4V plate coated with the ACP and OAp films was confirmed by a cell culture test. The removal torque of screw type Ti-6Al-4V implants with a blast-treated surface from the femur of a Japanese white rabbit increased with the duration of implantation and it was statistically improved by coating an ACP film two weeks after implantation. The in vitro and vivo studies suggested that the application of the sputtered ACP film as a coating on titanium implants was effective in improving their biocompatibility with the bones.