title: Osteoconductive property of a mechanical mixture of octacalcium phosphate and amorphous calcium phosphate.
abstract: The present study was designed to investigate the extent of osteoconductive property of a mechanical mixture of octacalcium phosphate (OCP) and amorphous calcium phosphate (ACP). OCP was mixed with ACP in granules that had a diameter of 300 and 500 μm, respectively, and at 25, 50, or 75 wt %. The physicochemical characteristics and the osteoconductive properties of the mixtures were compared with OCP alone or ACP alone through implantation into rat critical-sized calvaria defects for up to 12 weeks and simulated body fluid (SBF) immersion for 2 weeks. The mixtures of OCP and ACP, in particular the OCP 25 wt % and ACP 75 wt % (O25A75), had higher radiopacity compared to ACP and OCP alone. O25A75 induced greater enhancement of bone regeneration than ACP alone at 8 weeks and that than OCP alone at 12 weeks. X-ray diffraction and Fourier transform infrared (FTIR) analyses of the retrieved mixtures showed that ACP, OCP, and O25A75 tended to convert to hydroxyapatite (HA) after the implantation, while the structure of OCP remains without complete conversion after SBF immersion. Analyses by FTIR curve fitting of the solids and the degree of supersaturation of the SBF supported the observation that the existence of ACP enhances the kinetics of the conversion. Scanning electron microscopy found that the surface of O25A75 had distinct characteristics with OCP and ACP after SBF immersion. The results suggest that the extent of the osteoconduction of OCP could be controlled by the copresence of ACP most probably through the prevailing dissolution-precipitation of the surface of ACP crystals to form HA.
authors.affiliation: Division of Oral and Maxillofacial Surgery and ‡Division of Craniofacial Function Engineering, Tohoku University Graduate School of Dentistry , Sendai, Miyagi 980-8575, Japan.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Takahisa
authors.initials: T
authors.lastname: Anada
authors.forename: Takuto
authors.initials: T
authors.lastname: Handa
authors.forename: Naofumi
authors.initials: N
authors.lastname: Kanda
authors.forename: Mariko
authors.initials: M
authors.lastname: Yoshinari
authors.forename: Tetsu
authors.initials: T
authors.lastname: Takahashi
authors.forename: Osamu
authors.initials: O
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D001861:Bone Regeneration / Q000187:drug effects / Q000502:physiology*; D018786:Bone Substitutes / Q000138:chemical synthesis / Q000627:therapeutic use*; D002130:Calcium Phosphates / Q000008:administration & dosage* / Q000737:chemistry; D010012:Osteogenesis / Q000502:physiology*; D051381:Rats; D012887:Skull Fractures / Q000473:pathology / Q000628:therapy*; D016896:Treatment Outcome
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; C022045:octacalcium phosphate; C020243:calcium phosphate
keywords: amorphous calcium phosphate (ACP); bone regeneration; conversion; hydoroxyapatite (HA); octacalcium phosphate (OCP)