Calcium phosphate bone graft substitutes: Failures and hopes

Despite 40 years of efforts, researchers have failed to provide calcium phosphate bone graft substitutes performing well enough to replace bone grafting procedures: their osteogenesis potential is limited, and calcium phosphates are too brittle. However, there is hope to solve the two afore-mentioned problems. First, it is now clear why nacre and bone are very tough despite a high ceramic load. Also, recent studies suggest that calcium and phosphate ions can trigger osteoinduction. The present article aims: (i) to review our current knowledge in the field of synthetic bone graft substitutes, (ii) to explain why ceramics and in particular calcium phosphates are still the most promising materials for bone graft substitution, and (iii) finally to describe the strategy to obtain osteoinductive calcium phosphate bone graft substitutes as strong as cortical bone.