High phosphate content significantly increases apatite formation of fluoride-containing bioactive glasses

Bioactive glass-containing toothpaste for treating dentine hypersensitivity work by precipitating hydroxycarbonate apatite (HCA) onto the tooth surface, but concerns exist over the long-term durability of HCA in the mouth. Fluoride-containing bioactive glasses form fluorapatite (FAp) in physiological solutions, which is more chemically stable against acid attack.

An increase in phosphate or fluoride content allowed for apatite formation at lower pH.

The influence of phosphate content on apatite formation was investigated by producing a low-phosphate (about 1 mol% P2O5) and a high-phosphate (about 6 mol%) series of melt-derived bioactive glasses in the system SiO2AP2O5ACaOANa2O; increasing amounts of CaF2 were added by keeping the ratio of all other components constant. An increase in phosphate or fluoride content allowed for apatite formation at lower pH; fluoride enhanced apatite formation due to lower solubility of FAp compared to hydroxyapatite or HCA.

High phosphate content fluoride-containing glasses are particularly suited for use in remineralizing dentifrices.

Fluoride-containing bioactive glasses form FAp in Tris buffer solution, which is more acid resistant than HCA. Apatite formation occurred more rapidly (within 6h) with increased phosphate content in the glass compared to 3 days for low phosphate content glasses. An increase in phosphate content in the glass also favoured formation of FAp rather than fluorite, and allowed for apatite formation at lower pH, which is favourable for applications in both dentistry and orthopaedics. High phosphate content fluoride-containing glasses are particularly suited for use in remineralizing dentifrices for treating dentine hypersensitivity, as the phosphate ions present in saliva should result in apatite formation within even less than 6 h, i.e. well within a typical overnight sleep period of 8 hours.

Authors :

Mohammed Mneimne, Robert G. Hill, Andrew J. Bushby, Delia S. Brauer,

Journal :

Acta Biomaterialia 7 (2011) 1827–1834