Optimisation Of Bioactive Glass Compositions For Treatment Of Dentine Hypersensitivity

Objectives: Bioactive glasses are used as remineralising additives for toothpaste. The objective of this study is to optimise the composition further by incorporating fluoride in order to form fluorapatite (FAp) and give controlled fluoride release.

Methods: A series of glass was designed based on a commercial bioactive glass, 45S5 with higher phosphate content (≈3.5 mol%) and increasing fluoride content from 1 mol% up to 9 mol%. The fluoride was added whilst maintaining the ratio of remaining components to keep the network connectivity constant at around 2.1 for optimal bioactivity. Bioactive glasses were tested for their ability to form apatite by immersion in Tris buffer solution at different time points varying from 6 hours up to 1 week. Expected apatite formation was characterised by X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), followed by Inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis to detect release of ions. Fluoride release was measured with an ion selective electrode.

Results: FTIR showed significant apatite formation after 24 hours. ICP-OES data showed phosphate levels peaked at the earliest time point of 6 hours and were depleted from solution by 24 hours. Fluoride release was proportional to fluoride content in the glass and reduced with time corresponding to precipitation of FAp and fluorite.

Conclusion: The addition of fluorine to bioactive glasses has the beneficial effects of increasing reactivity of the bioactive glasses, whilst reducing the pH rise from glass dissolution. The use of fluorine allows for the formation of FAp rather than hydroxyapatite, which may be more durable for dental applications. Furthermore, use of fluoride at higher concentrations allows for greater fluoride release which aids in caries inhibition.  However, higher phosphate levels are required for the conversion of fluoride to FAp rather than fluorite.

This project has been co-funded by GSK and the BBSRC.