Fluoride-containing bioactive glass-ceramics

Fluorapatite glass-ceramics are osteoconductive, and glass-ceramics containing fluorapatite crystals in a bioactive silicate glass matrix can combine the benefits of fluorapatite with the bone-regenerative properties of bioactive glasses. High phosphate content (around 6 mol% P2O5) bioactive glasses (SiO2–P2O5–CaO–Na2O–CaF2) were prepared by a melt-quench route. Structural investigation using density measurements and calculations confirmed the presence of phosphorus as orthophosphate. Upon heat treatment, the glasses crystallised to mixed sodium calcium fluoride orthophosphates (sodium-containing compositions) and fluorapatite (sodium-free composition). Fluoride suppressed spontaneous crystallisation, allowing formation of glass-ceramics by controlled crystallisation. A notable feature is that silicate network polymerisation and network connectivity did not change during crystallisation, resulting in orthophosphate and fluorapatite crystals embedded within a bioactive glass matrix. By keeping the phosphate content high and the sodium content low, fluorapatite glass-ceramics can be obtained, while not affecting the structure of the bioactive silicate glass phase.

► High phosphate content bioactive glasses crystallise to orthophosphates.
► Sodium-free versions crystallise to fluorapatite.
► Glass network connectivity remains unchanged during fluorapatite crystallisation.
► Glass-ceramics have fluorapatite crystals embedded in a bioactive glass matrix.