In vivo bone formation on apatite-coated titanium incorporating BMP-2/heparin

Objectives: Many materials, with different surfaces, have been developed for clinical implant therapy in dentistry and orthopedics. To shorten the healing period after implantation, titanium is coated with apatite. Bone morphogenetic protein-2 (BMP-2) strongly induces osteogenesis and heparin enhances its action. In this study, we developed an osteoinductive material by coating the surface of titanium implants with apatite incorporating BMP-2 and heparin.

Methods: The titanium implants were alkaline-treated, heat-activated, and soaked in stimulated body fluid with or without a BMP-2/heparin coating. To analyze the quantity of new bone formed in vivo around the implants, treated implant bars (ö1 mm, 2 mm in length) were implanted in rat tibia. After 1 and 3 weeks, new bone formation was visualized using fluorescent labeling. After 3 weeks, undecalcified sections were prepared, and new bone formation around the implants was examined by morphometry using fluorescence microscopy.

Results: Three weeks after implantation, there was more bone around the implants coated with apatite containing BMP-2/heparin than around those coated with apatite containing only BMP-2 or around uncoated implants. The BMP-2/heparin apatite coating significantly enhanced new endosteal bone formation, increasing both the vertical (134%) and horizontal (251%) thickness of new bone compared with pure titanium implants.

Conclusions: When BMP-2 and heparin were incorporated into the apatite coating on titanium implants, bone formation around the implants increased significantly. These findings demonstrate that heparin enhances the bone-formation activity of BMP-2 around implants, which might contribute to the success of implant therapy.