Effect of blood addition on the biocompatibility of calcium phosphate paste

The effect of blood addition on the biocompatibility and mechanical properties of calcium phosphate paste (CPP) has been examined. The addition of blood to the CPP increased the consistency and setting time in the malaxation operation; the specimen with blood addition possessed higher carbonate content and greater solubility into the acid but lower compressive strength, compared to the specimen without blood addition. Moreover, the immersion of CPP specimens with and without blood addition into the simulated body fluid showed no significant difference in conversion time of the chemical components (α-Ca3(PO4)2 and Ca4O(PO4)2) to the hydroxyapatite (Ca10(PO4)6(OH)2). These specimens were implanted into the tibiae of Japanese white rabbits. After the implantation for 12 weeks, the radiograph of CPP specimen with blood addition showed a clear regression of opacity, suggesting that the bioabsorbability and replacement with bone were promoted by the addition of blood; this effect proceeded significantly from surfaces to inside surfaces of CPP specimens as the amount of blood addition increased.