Characterization of calcium phosphates precipitated from simulated body fluid of different buffering capacities.

The purpose of this experiment was to study the properties of calcium phosphate precipitated from simulated body fluids (SBFs) with different buffering capacities. The Ca/P molar ratios of the precipitates were determined and the microstructure of a sintered precipitate was studied. The results indicate that the pH of the SBF increases during calcium phosphate precipitations, which affects the Ca/P molar ratios and chemical compositions of these precipitates. A precipitate with a Ca/P molar ratio close to the stoichiometric molar ratio of hydroxyapatite was obtained when the pH of the SBF was continuously adjusted to 7.26 during precipitation. This precipitate has a fine-grained and laminated microstructure after sintering at 1000 degrees C in air. It seems that SBF can be used as a tool to study apatite-like precipitation in vitro when the pH of the solution is carefully controlled.