Formula Ca8H2(PO4)6.5H2O Appearance white powder | Molar mass 446.234 g/mol | |
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Octacalcium phosphate (sometimes referred to as OCP) is a calcium phosphate with a formula Ca8H2(PO4)6.5H2O. OCP may be a precursor to tooth enamel, dentine, and bones.
Contents
OCP is a precursor of hydroxylapatite (HAP), an inorganic biomineral that is important in bone growth. OCP has been suggested as a replacement for HAP in bone grafts.
Octacalcium phosphate monographs in oral science vol 18
Crystal structure
OCP has the lattice constants a = 19.7 A., b = 9.59 A., c =6.87 A., α≅β = 90.7’ and γ = 71.8’. Corresponding hydroxyapatite constants are 2a = 18.84 A., a’ = 9.42 A., c = 6.885 k., α = α’ = 90” and γ = 60”, resemble closely those of OCP in the values of b, c and a, which lie in the plane of the OCP plates. The final pattern was apatitic, intermediate in sharpness between those of tooth enamel and bone. Boiling water decomposed OCP into an apatite approaching hydroxyapatite in composition, along with a variable amount of CaHP04. Both thermal and hydrothermal treatments sometimes yielded apatitic single crystal pseudomorphs after OCP, the c-axes being parallel to the c of the original OCP. Due to the small crystal structure of OCP it is often a twinned crystal structure. The average crystal size of OCP is 13.5 ± 0.2 nm
Synthesis
It can be prepared by treating calcium acetate with sodium acid phosphate solution.
Hydrolysis of OCP creates hydroxyapatite
