Octacalcium phosphate (OCP)-based bone substitute materials

The present article summarizes the characteristics of a synthetic octacalcium phosphate (OCP) and OCP-based materials. We previously established a method for a relatively large scale synthesis of OCP and showed that OCP enhances bone regeneration more than hydroxyapatite (HA) materials, including HA obtained through hydrolysis of OCP, coupled with material biodegradation if implanted in various bone defects. One of the OCP-based materials consisting of OCP and natural polymers, such as gelatin, induced a bone regeneration rate over 70% in critical sized rat calvaria defects, which approached the rate seen with autologous bone implantation. The bone regenerative properties observed for OCP-based materials could be due to the biological activity of OCP crystals that enhance in vitro osteoblast differentiation and osteoclast formation from precursor cells. OCP controls the environment around its own crystals, where osteoblastic cells encounter OCP during the progressive conversion to HA under physiological conditions. This process contributes to an increase in the biological activity of OCP, resulting in enhancing bone regeneration. Although the positive effect of OCP depends on the crystal stoichiometry and morphology, determined by the conditions used preparing OCP, it is probable that OCP-based materials could be good candidates for an advanced material compatible to autologous bone.