Three silicon-doped calcium phosphates (Si-CaPs) were synthesized by heating precipitated silicon-doped apatite via different thermal treatments. Temperatures of 700 degrees C, 900 degrees C, and 1100 degrees C led to an apatite-glass biphasic material, nanocrystalline Si-doped apatite (SiHA), and Si-doped apatite-alpha tricalcium phosphate biphasic material, respectively. Structure, microstructure, textural properties, and chemical differences were determined for the three bioceramics. Biocompatibility tests were carried out by seeding osteblast-like cells onto the three substrates. Si-CaP treated at 700 degrees C and 900 degrees C led to Ca decrease in the culture media, partially impeding the cell proliferation over them. However, the proliferation capability is restored when additional culture medium is added. Finally, cytotoxicity results indicated that cell damage is much lower in osteblast-like cells seeded onto SiHA and SiHA-alpha tricalcium phosphate samples than in plastic culture control.