Effect of ZrO2 additions on the crystallization, mechanical and biological properties of MgO–CaO–SiO2–P2O5–CaF2 bioactive glass-ceramics

A series of ZrO2 doped MgO–CaO–SiO2–P2O5–CaF2 bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca5(PO4)3F (fluorapatite) and β-CaSiO3 (β-wollastonite). m-ZrO2 (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO2 (tetragonal zirconia) increased the crystallization temperature of Ca5(PO4)3F and declined the crystallization temperature of β-CaSiO3. t-ZrO2 greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell.