Abstract: Hydroxyapatite (HAP), bioactive glass, wollastonite and composites of hydroxyapatite and wollastonite were
prepared. These different bioactive ceramics were soaked in the simulated body fluid (SBF) under the same condition and characterized by Fourier
Transform Infrared Spectrometry (FTIR) and Field Emission Scanning Electron Microscope (FESEM). The results showed that the surfaces of these bioactive
ceramics were covered with a layer of carbonate hydroxyapatite (HCA) when soaked in SBF. The speed of HCA deposition and the microstructure of the
HCA were different between different materials. HCA formed on the surfaces of the above bioactive ceramics was spherical, and the HCA layer formed on
the surfaces of HAP and wollastonite was slightly loose as compared with that on bioactive glass. When wollastonite was added into HAP, both the speed of
HCA deposition and the microstructure of HCA formed on the surfaces of the composites were clearly affected. The results show that the speed of the HCA
deposition and the microstructure of HCA in SBF can be used to estimate the in vitro bioactivity of inorganic biomaterials, and the bioactivity
of the composites can be regulated by the ratio of the wollastonite/hydroxyapatite.

Key words: HAP, bioactive glass, wollastonite, composite, HCA, SBF