Comparative study of the osteoinductive properties of bioceramic, coral and processed bone graft substitutes.

This study compared the osteoinductive properties of six different bone graft substitutes: Pyrost, natural coral, Callopat, Surgibone, demineralized Surgibone and demineralized rat bone. The materials were implanted heterotopically, in the abdominal musculature of rats, and the results evaluated histologically at 3 and 6 wk post-implantation. Surprisingly, the results showed that both the demineralized rat bone and demineralized Surgibone were less osteoinductive than might be believed from the literature. Mineralized grafts showed no sign of new bone formation and exhibited variable resorption patterns. A layer of what appeared as dense calcification was seen around the coral implant. The most intense inflammatory reactions were exhibited with the xenografts Surgibone and demineralized Surgibone, indicating persistent immune responses. Coral and Pyrost elicited no marked inflammatory response, and this was attributed to the negligible amounts of protein present in these materials.