Bone regenerative efficacy of biphasic calcium phosphate collagen composite as a carrier of rhBMP-2

Objectives This study compared the bone regenerative effects of a recombinant human bone morphogenetic protein 2 (rhBMP‐2)‐loaded collagen‐based biphasic calcium phosphate composite (BCPC) and rhBMP‐2‐loaded biphasic calcium phosphate (BCP). Material and methods The in vitro release profiles of rhBMP‐2‐loaded BCP and BCPC were measured. The animal surgery was performed on ten rabbits. Four 8‐mm‐diameter circular calvarial defects were made and filled with BCP, BCPC, rhBMP‐2‐loaded BCP (BMP + BCP) and rhBMP‐2‐loaded BCPC (BMP + BCPC). The animals were euthanized either 2 or 8 weeks after surgery. Results The initial burst release of rhBMP‐2 was greater for BCP than for BCPC, and both presented a slow release pattern thereafter. In rabbit calvarial defects, the space maintaining capability and graft resorption of all experimental groups did not show statistical differences at 2 and 8 weeks. New bone formation in the rhBMP‐2‐loaded groups was greater than in the non‐loaded groups at both weeks, but the amount of new bone was comparable between both rhBMP‐2‐loaded groups at both weeks. There was a distinct histologic difference between the BMP + BCP and BMP + BCPC groups at 2 weeks; the new bone formation occurred more in the intergranular spaces and the BCP‐to‐bone contact was greater in the BMP + BCPC group, but these differences were no longer discernible at 8 weeks. Conclusions BCP‐ and BCPC‐loaded rhBMP‐2 significantly improved bone regeneration and BCPC led to a dense network of new bone and bone particles during the early healing period. BCPC can therefore be considered as a promising candidate for carrying rhBMP‐2.