Comparative study of biphasic calcium phosphate ceramics impregnated with rhBMP-2 as bone substitutes

We investigated pellet-shaped implants prepared from biphasic calcium phosphate (BCP) ceramics with five different ratios of hydroxyapatite (HAP) to beta-tricalcium phosphate (beta-TCP) to evaluate these ceramics as bone substitutes. BCP ceramics impregnated with different doses of recombinant human bone morphogenetic protein 2 (rhBMP-2) (1, 5, and 10 microg) were used for experimental purposes and ceramics without rhBMP-2 were used for control. The pellets were implanted under the pericranium in adult Wistar male rats and were harvested 8 weeks after implantation. The retrieved pellets were then examined radiologically, histologically, and histomorphometrically. The results revealed that the pellets treated with rhBMP-2 exhibited new bone and bone marrow, whereas control pellets produced fibrous connective tissues. The formation of new bone induced by rhBMP-2 was dose dependent. The extent of bone and bone marrow formation and the degree of resorption of the ceramic particles were significantly higher in the pellets composed of 25% HAP-75% TCP. In this study, bioresorption of the ceramic produced favorable conditions for rhBMP-2-induced bone formation.