Influence of design on bioactivity of novel CaSiO3–CaMg(SiO3)2 bioceramics: In vitro simulated body fluid test and thermodynamic simulation

A new type of bioactive ceramic has been designed and obtained from high-temperature phase information from the wollastonite (CaSiO3)–diopside (CaMg(SiO3)2) phase equilibrium diagram. The selected composition was that corresponding to the eutectic point of the pseudobinary CaSiO3–CaMg(SiO3)2 system. The sintering behaviour, phase evolution, microstructural changes and in vitro bioactivity of CaSiO3–CaMg(SiO3)2 eutectic bioceramics were analysed by differential thermal analysis, X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and image analysis. A simulation of the dissolution properties of the different materials studied, in water as well as in simulated body fluid (SBF), was also carried out by thermodynamic calculations, with the purpose of understanding the in vitro results obtained. The results demonstrate that the CaMg(SiO3)2 is significantly less soluble than CaSiO3, developing an in situ porous structure (biomimetic porous bone material) with adequate biodegradation rate and stability strength when immersed in SBF. The influence of the microstructure (porosity, grain size and phase composition) on the in vitro bioactivity of the obtained bioceramics was also examined.