MINERALIZATION OF CALCIUM PHOSPHATE ON OCTACALCIUM PHOSPHATE IN A SOLUTION MIMICKING IN VIVO CONDITIONS

Abstract

Octacalcium phosphate (OCP) has a biological affinity for living bone. It is worthwhile investigating the behavior of crystal growth, transformation and dissolution of OCP crystals under physiological conditions, with a similar concentration in inorganic composition to that of human blood plasma, to understand the affinity for living bone. We examined the behavior of OCP crystals after exposure to a simulated body fluid (SBF). No crystalline phase changes were exhibited by samples soaked in SBF, but formation of calcium phosphate was assumed to occur because of decreases in concentration of both calcium and phosphate ions in SBF. The molar ratio of the reduction in calcium and phosphate ions concentrations (ΔCa/ΔP) at 1 day was 1.42, eventually converging to a value of 1.33. These results indicated that OCP was formed on OCP crystals through an intermediate amorphous phase and OCP soaked in SBF was transformed into hydroxyapatite to only a negligible extent in the solution. (Received February 25, 2012; Accepted May 18, 2012)