Preparation and characterization of resorbable calcium phosphate based bioceramics

Abstract

The main objective of this study was to determine the behavior of hydroxyapatite powders in solutions containing major ions found in human blood plasma. Research efforts however were focused on two different fields, chemical analysis and dissolution testing of hydroxyapatite. Arsenazo III-calcium analysis method was selected and modified for the low level calcium analysis whereas malachite green phosphate assay was used for phosphate determinations. Arsenazo III reagents with different dye concentrations and pH values were tested for the analysis of low levels of calcium. The effects of ions at their blood plasma concentration levels on the modified calcium analysis method were further evaluated. Effects of these ions on the accuracy of phosphate analysis by malachite green assay were also investigated. Dissolution behavior of synthesized and commercial hydroxyapatite was investigated by immersing pellets in several solutions. Calcium and phosphate release kinetics in ultrapure water, sodium chloride and sodium bicarbonate solutions were investigated. Commercial hydroxyapatite pellets were also immersed separately in magnesium chloride, and sodium chloride/bicarbonate solutions. Calcium concentrations in solutions were found to decrease in the following order: sodium chloride > ultrapure water > bicarbonate. Phosphate concentrations in solutions were found to follow an order of sodium bicarbonate > sodium chloride > ultrapure water. Bicarbonate-phosphate ion exchange was observed in bicarbonate ion containing solutions. Magnesium-calcium ion exchange and adsorption of phosphates on hydroxyapatite surfaces were found to be effective in magnesium ion containing solution.