The aim of this study was to investigate the in vivo performance of implants coated with hydroxyapatite (HAp) with different surface morphologies. HAp coatings were formed on commercially pure titanium rods (2 mm in diameter, 5 mm in length) by the thermal substrate method in an aqueous solution that included Ca(H 2 PO 4 ) 2 and CaCl 2 . The coating experiments were conducted at 40-140 C and pH ¼ 8 for 15 or 30 min. All the specimens were covered with HAp, which had different morphologies such as net-like, plate-like, and needle-like. The coated rods were implanted in the tibiae of 10-week-old male rats. Noncoated titanium rods were used as the control in this study. The constructs were retrieved 14, 28, and 56 days postimplantation and examined for new bone formation and tissue response in the cancellous and cortical bone, respectively. After 14 days implantation, new bone formed on both the HAp-coated and noncoated titanium rods in the cancellous and cortical bone. However, the bone-implant contact ratio, which was used for the evaluation of new bone formation, was significantly dependent on the surface morphology of the HAp, and the results demonstrated that the needle-like coating appears to promote rapid bone formation.

Hydroxyapatite (HAp) coated films were obtained using a thermal substrate method, whereby an aqueous solution at pH ¼ 7 or 8 containing Ca 2þ and PO 4 3À ions was used to deposit a coating on porous-surfaces substrates formed by sintering 44-150 mm-sized Ti6Al4V powders on a solid commercially pure titanium (cpTi) base. The HAp coating conditions used were: coating time = $900 s and substrate temperature equal to 373 or 393 K. Coatings formed in a pH ¼ 7 solution at 373 K for 900 s and in a pH ¼ 8 solution at 393 K for 300 s showed that all of the surfaces of the Ti6Al4V sintered particles (both front and back faces) and the base cpTi substrate were covered with HAp, and that they maintained their original open-pored geometry. The precipitated HAp appeared to be denser on porous-surfaced samples compared with plain-surfaced cpTi samples. Use of the thermal substrate method with appropriate pH control, and substrate heating temperature and time was effective for forming HAp coatings on powder-sintered samples with a complex topography.

The aim of this study was to investigate the in vivo performance of implants coated with hydroxyapatite (HAp) with different surface morphologies. HAp coatings were formed on commercially pure titanium rods (2 mm in diameter, 5 mm in length) by the thermal substrate method in an aqueous solution that included Ca(H 2 PO 4 ) 2 and CaCl 2 . The coating experiments were conducted at 40 140°C and pH＝8 for 15 or 30 min. All the specimens were covered with HAp, which had different morphologies such as net like, plate like, and needle like. The coated rods were implanted in the tibiae of 10 week old male rats. Noncoated titanium rods were used as the control in this study. The constructs were retrieved 14, 28, and 56 days postimplantation and examined for new bone formation and tissue response in the cancellous and cortical bone, respectively. After 14 days implantation, new bone formed on both the HAp coated and noncoated titanium rods in the cancellous and cortical bone. However, the bone implant contact ratio, which was used for the evaluation of new bone formation, was significantly dependlnt on the surface morphology of the HAp, and the results demonstrated that the needle like coating appears to promote rapid bone formation.