Osteoinductivity of HAp Films with Different Surface Morphologies Coated by the Thermal Substrate Method in Aqueous Solutions

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(H2PO4) 2 and CaCl2. 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 dependent on the surface morphology of the HAp, and the results demonstrated that the needle-like coating appears to promote rapid bone formation.