Influence of mixing blood with calcium phosphate bone paste on hardening.

Calcium phosphate bone paste (CPP) has been recently introduced as a reconstructive material in craniofacial surgery. However, we observed that mixing of blood and CPP tended to interfere with CPP hardening. In addition, CPP mixed with blood tended to be absorbed postoperatively. Hence, we used a rabbit model and applied CPP mixed with blood over defects in the skull to investigate the influence of blood on CPP. Calcium phosphate bone paste was mixed with blood for 1 minute and applied to the defects in the calvarial bone of rabbits. At 4 and 24 postoperative weeks, we histologically evaluated morphologic changes in the hydroxyapatite (HA). Our study revealed that HA was not absorbed when a small quantity of blood (15%) was mixed with CPP. However, HA was absorbed almost entirely when a large quantity of blood (30%) was mixed with CPP. In addition, we found that the porosity of HA was increased by the mixture of a small quantity of blood into CPP, and this addition stimulated osteogenesis in HA.