Osteoconduction of a stoichiometric and bovine hydroxyapatite bilayer-coated implant.

OBJECTIVE To impart rapid and durable osteoconductivity to implants, a commercial titanium screw implant was coated with stoichiometric hydroxyapatite (HA; 50 nm thick), and then with bovine hydroxyapatite (B-HA; 300 nm thick) using the pulsed laser deposition technique. As control specimens, a commercial implant coated with HA (20 μm thick) using the flame spraying method (sprayed implant) and a simple titanium implant (basic implant) was used. METHODS The osteoconductivities of these three types of implant, after implantation for 4-24 weeks, were histologically evaluated. RESULTS Peeling of HA from the sprayed implant was observed by scanning electron microscopic observation. In the fourth postoperative week, the bilayered implant was already closely adhered to bone. On the other hand, the basic implant was surrounded by a gap containing connective tissue. With the sprayed implant, the bone adhered to the thick HA coating. CONCLUSION The bilayer deposition technique supplies quick and long-term fixation of implants to bone, because the B-HA film dissolves to aid osteoconduction right immediately after implantation and the HA thin film maintains osteoconduction without dissolution. Neither of the thin-film fractures easily compared with thick coatings.