Bioactivity potential of calcium alumino-silicate glasses and glass-ceramics containing nitrogen and fluorine

Calcium alumino-silicate glasses of general composition (in eq.%) 28Ca:57Si:15Al:[100 - (x + y)]O:xN:yF (x = 0 or 20 and y = 0, 3 or 5) and their glass-ceramic counterparts were immersed in simulated body fluid (SBF) at 37 ± 0.5 °C for 28 days to assess their potential bioactivity. The glasses showed no Ca release or surface calcium phosphate deposition due to their high network connectivities (>2.55). The glass-ceramics all showed potential bioactivity, as the SBF became enriched in Ca and calcium phosphate deposits formed on their surfaces. This was a result of Ca release from crystalline phases (predominantly wollastonite in the case of CaSiAlOF glass-ceramics and gehlenite in the case of CaSiAlONF glass-ceramics). No aluminium was leached from the glass-ceramics into the SBF, due to its pH always exceeding 7.0.