TRANSITORY NATURE OF OCTACALCIUM PHOSPHATE IN PHYSIOLOGICAL MILIEU AND ITS OSTEOCONDUCTIVE PROPERTY

Abstract

Octacalcium phosphate (OCP) is a metastable salt in physiological pH which tends to convert to hydroxyapatite (HA). Conversion from OCP to HA is also observed if OCP is implanted in various bony sites. From a quantitative viewpoint, the implantation of OCP granules enhances bone regeneration more than that of non-sintered HA or sintered HA granules in rabbit bone marrow spaces or the subperiosteal area of mouse calvaria; in addition, OCP is biodegraded by osteoclast-like cells. OCP promotes differentiation of bone marrow stromal cells to osteoblastic cells. These osteoconductive characteristics may be acquired by the dissolution process associated with the progressive OCP-HA conversion. The biodegradability and osteoconductive characteristics are summarized in relation to the solubility of OCP.