Transition of octacalcium phosphate to hydroxyapatite in solution at pH 7.4 and 37 degrees C

Transition of octacalcium phosphate (OCP) to apatite was studied under the condition where Ca2+ ions were continuously supplied to the reacting solution at pH 7.4 and at 37 degrees C. OCP crystals were grown and subsequently converted into apatite by discontinuing of Ca addition. The rectangular (1 0 0) blades of OCP crystals developed notches on their short edges in the early stage of transition. The depth of the notches increased along the c-axis direction with the progress of the reaction, giving rise to a slit-like texture. The direction of the slit formation seemed to relate to the spatial configuration of H2O molecules in the OCP lattice, which are released during the transition from OCP to apatite.