Sol-gel bioactive glasses for oral care applications

Dentin hypersensitivity (DH) is a condition where exposure to different stimuli in oral environment results in pain. The presence of open dentin tubules is the attributing cause. Commercial toothpaste, Sensodyne Repair and Protect, treat DH by occluding dentin tubules. The product contains 45S5 melt derived bioactive glass with a certain particle size range, known as NovaMin™. Currently multiple applications are required before effective occlusion is achieved. The focus of present work was to design a fit for purpose composition that deliver more rapid or extensive tubule occlusion and has lower abrasivity than 45S5. Sol-gel bioactive glass has higher surface area and porosity compared with melt derived glass, resulting in faster dissolution and formation of hydroxyl apatite layer (HA). This was the reason for choosing sol-gel process for oral care application. Compositions containing various levels of sodium oxide (4-24 mol%) and sodium free samples with different levels of phosphate (2.5, 5.5 and 8.5 mol% P2O5) were prepared, characterised and assessed for bioactivity in artificial saliva (AS). Bioactivity showed that presence of sodium has no significant effect on rate of HA formation. Increase in Phosphate content resulted in phosphate release, leading to buffering of pH. Composition 64S 2P (2.5mol % P2O5) showed most extensive calcium phosphate precipitation. 64S 8P (8.5 mol % P2O5) led to more rapid transition to crystalline HA. Both were selected as suitable candidates for rapid and/or extensive tubule occlusion. Dentin discs brushed with 64S 2P and 64S 8P toothpastes showed higher deposition and more extensive tubule occlusion compare to specimens treated with control paste and melt derived 45S5. Significant difference in surface roughness of dentin discs treated with 64S 2P,64S 8P vs. 45S5 was found, confirming lower abrasivity of sol-gel glass. Liquid delivery of bioactive glass was explored, calcium phosphate precipitation in AS was achieved offering treatment with no abrasivity.Open Acces