Papers by Author: Hiroshi Kawamura

Abstract: Oxyapatite, amorphous calcium phosphate, and double-layered calcium phosphate coating films were fabricated on mirror-polished commercially pure titanium (CP Ti) and blasted Ti-6Al-4V alloy substrates by radiofrequency (RF) magnetron sputtering; the properties of these films were evaluated in vivo and in vitro. The bonding strength between the calcium phosphate films and the Ti substrates was higher than 50 MPa. This value is higher than the bonding strength reported in the case of plasma-sprayed calcium phosphate coating films fabricated on Ti substrates. The removal torque of screw-type blasted Ti-6Al-4V alloy implants in the femurs of Japanese white rabbits increased with the duration of implantation, and the removal torque values of the coated implants was observed to be higher than those of the non-coated implants. In vitro and in vivo studies indicate that coating Ti implants with calcium phosphate films using RF magnetron sputtering is effective in improving the bone compatibility of Ti implants. Finally, the factors that should be considered in fabricating biomedical coating films were discussed.

Abstract: Calcium phosphate coating films were fabricated on Ti-6Al-4V plates and screw-type 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 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 substrate exceeded 60 MPa, independent of film phases except for the film after post-heat-treatment in silica ampoule. When compared with an uncoated substrate, the increase in the ALP activity of osteoblastic SaOS-2 cells on a calcium phosphate coated substrate 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 Japanese white rabbit increased with the duration of implantation and it was statistically improved by coating an ACP film 2 weeks after implantation. The in vitro and in vivo studies suggested that the application of the sputtered ACP film as a coating on titanium implants was effective in improving their biocompatibility with bones.

Abstract: Calcium phosphate coating films were fabricated on mirror-polished or blast-treated titanium substrates using radio-frequency (RF) magnetron sputtering and they were evaluated in vitro. Immersion tests for the films were conducted using phosphate-buffered saline (PBS(-)), and apatite formation and the elution of calcium ions from the films were investigated. The bonding strengths between the calcium phosphate films and titanium substrates before and after the immersion tests were evaluated. After the immersion tests, a decrease in the bonding strength was observed for the coating films on the mirror-polished titanium substrates, while that for the blast-treated titanium substrates was almost the same as that before the immersion tests.

Abstract: Calcium phosphate films were coated on commercially pure titanium substrates by radiofrequency magnetron sputtering using β-tricalcium phosphate targets. The films consisted of amorphous calcium phosphate and oxyapatite phases. Immersion tests of the films were carried out in Hanks’ solution and PBS(-), and apatite formation and calcium ion elution from the films were investigated. The titanium cylinders coated with calcium phosphate films were implanted into the mandibles of beagle dogs. These results suggest that coating with calcium phosphate improves the biocompatibility of titanium implants with bone tissue.