Dissolution on the Surface of Calcium Phosphate Ceramics in Water

Abstract

Four types of commercial calcium phosphate ceramics, i.e. tricalcium phosphate, biphasic calcium phosphate, hydroxyapatite and near stoichiometric hydroxyapatite, were prepared by sintering at 1200°C for 2 h in air with moisture protection. Their dissolution characteristics were investigated by microstructural observations after immersion in distilled water at 37°C for 3 or 7 days. For all samples, no significant damage was observed after 3 days of exposure. However, after immersion for 7 days, grain boundary dissolution, even in pure hydroxyapatite, followed by grain separation occurred on the surfaces. The dissolution extended to interior region of the ceramics following along the grain boundaries. In the severely dissolved area, pitting similar to that normally attributed to osteoclast resorption lacunae was observed. In case of the material having a high percentage of porosity, dissolution was concentrated on those grains adjacent to pores rather than those in the dense region.