Effect of silicon content on the sintering and biological behaviour of Ca10(PO4)6-x(SiO4)x(OH)2-x ceramics

Silicated hydroxyapatite powders (Ca10(PO4)6-x(SiO4)x(OH)2-x; SixHA) were synthesized using a wet precipitation method. The sintering of SixHA ceramics with 0 x 1 was investigated. For 0 x 0.5, the sintering rate and grain growth decreased slightly with the amount of silicate. For larger amounts, the sintering behaviour differed with the formation of secondary phases before total densification. Sintering parameters (temperature and time) were adjusted to each composition to produce dense materials having similar microstructure without formation of these secondary phases. Dense ceramics made of pure hydroxyapatite and SixHA containing various amounts of silicate (up to x = 0.6) were biologically tested in vitro with human osteoblast-like cells. The proliferation of cells on the surface of the ceramics increased up to 5 days of culture, indicating that the materials were biocompatible. However, the silicon content did not influence the cell proliferation.