Study of novel oxyfluoronitride bioglasses

Bioglasses are used as bone substitutes and prosthetic coatings. Following implantation, they are predisposed to generate a series of physicochemical reactions at the glass-bone interface. Bioglasses with molar composition: 55SiO₂–8.5CaO–31.5Na₂O–5CaF₂ have been synthesized and characterized. However, because of their poor strength, doping with nitrogen was performed on these glasses to increase their mechanical properties. The Young s elastic moduli, Vicker s microhardnesses, and the fracture toughnesses were measured and observed to increase linearly with nitrogen content in each of these systems. These results are consistent with the incorporation of nitrogen into the glass structure in three-fold coordination with silicon. Fluorine addition significantly decreases the thermal property values but the mechanical properties of these glasses remain unchanged with fluorine. The characterization of these N and F substituted bioglasses using ²⁹Si MAS NMR have shown that the increase in rigidity of the glass network can be explained by the formation of SiO₃N, SiO₂N₂ tetrahedra and Q⁴ units with extra bridging anions at the expense of Q³ units. The bioactivity of the glasses has been evaluated by soaking them in simulated body fluid (SBF) and showed that all oxyfluonitrides glasses are bioactives. Cytotoxicity tests based on different concentrations of bioglass powders in a cell growth environment have been also showed that they are not cytotoxic