In vitro biocompatibility of resorbable experimental glass ceramics for bone substitutes

Tricalcium phosphate ceramics (TCPs) are increasingly used as bone substitutes. They demonstrate good biocompatibility and degrade relatively slowly. New glass ceramics based on calcium alkali orthophosphates (Ca2KNa(PO4)(2)) were developed that degrade faster than TCP but could have reduced biocompatibility due to their high solubility. Therefore, they were modified by a neutralizing surface treatment. The aim of this study was to evaluate the biocompatibility of some of these ceramics, GB1a, GB9, and GB14, which differ in the amount of added Na, K, Mg, or Si ions, with standard and modified surfaces. The in vitro cytotoxicity of the ceramics GB1a, GB9, and GB14 was determined by the agar diffusion and filter test and the microculture tetrazolium (MTT) assay. In order to investigate the influence of surface modification, these three ceramics were compared to their surface-treated counterparts, GB1aN, GB9N, and GB14N. GB1a, the ceramic with the highest in vitro solubility, showed the strongest toxic influence in all cell culture tests. GB9 and GB14 produced better results. In contrast, the counterparts with modified surfaces exhibited no (GB9N, GB14N) or weak (GB1aN) signs of cytotoxicity. It is concluded that the toxicity of the ceramics GB1a, GB9, and GB14 depends on their solubility. A positive influence of the surface treatment on in vitro biocompatibility was demonstrated. Therefore, the surface-treated glass ceramics could be promising materials for bone replacement. (C) 2001 John Wiley & Sons. Inc.