The influence of recombinant human BMP-2 on bone-implant osseointegration: biomechanical testing and histomorphometric analysis

The healing period for bone-implant osseointegration lasts 3-6 months or even longer. The aim of this study was to investigate whether osseointegration can be enhanced by the use of bone morphogenetic protein-2 (BMP-2). In the femurs of 8 Japanese white rabbits, 16 implants were applied with 1.0 mg recombinant human BMP-2 (rhBMP-2) as group A, and the other 16 implants without rhBMP-2 as group B. Calcein green 20 mg/kg and alizarin red 20 mg/kg were injected 4 and 8 weeks after implantation, respectively. At 12 weeks, the animals were killed. In 16 implant-bone blocks, binding strength was measured by pull-out test, and the extracted implants were observed under a scanning electronic microscope. The other blocks were analysed for percentage of marked bone adjacent to the implant surface by confocal laser scanning microscope. The pull-out strengths of group A were greater than that of group B (P<0.05). Scanning electronic microscopy (SEM) showed more calcified substances on the surface of the implants of group A than B. There was more marked bone around group A than B implants at 4 weeks (P<0.05) and 8 weeks (P<0.05). rhBMP-2 improves the quantity and quality of implant-bone osseointegration. Biomechanical testing and histomorphometric analysis are reliable methods to use in researching the implant-bone interface.