Abstract text (incl. figure legends and references)
Question and motivation
Bioactive glasses are successfully used for bone regeneration and tooth remineralisation. However, some open questions remain on how phosphate content and silicate network polymerisation ("network connectivity") affect ion release and surface mineralization.
The aim was to systematically investigate ion release and surface changes during immersion of bioactive glasses with and without phosphate in simulated physiological solutions.
Methods
Glasses in the system SiO2-CaO-Na2O-(P2O5) were prepared by a melt-quench route. Ion release and surface changes were analysed during immersion in simulated body fluid. In addition, network connectivity was analysed using Raman and solid-state NMR spectroscopy.
Results
In both phosphate-free and phosphate-containing glasses, network connectivity increased with increasing silica content in the glass. In both series, this increase resulted in a decrease in ion release. By contrast, apatite surface mineralisation decreased in phosphate-free glasses only, while phosphate-containing ones still showed apatite surface layer formation even at high network connectivity values.
Conclusion
While bioactive glass network connectivity is an important parameter, its effect on surface apatite mineralisation is less pronounced if the glass is capable of releasing phosphate ions. This is of interest if we want to prepare glasses which can be processed more easily and show a lower tendency to crystallise at high temperatures: If we introduce enough phosphate into the glass, we can prepare glasses with higher network connectivity that can be processed without crystallisation and still are capable of reacting with physiological solutions.