High-Fluoride Bioactive Glass and Tricalcium Phosphate Mixtures for Remineralising Toothpastes

Objectives: The aim of this study was to develop a remineralising active ingredient comprising a high-fluoride containing bioactive glass (F-BAG) and tricalcium phosphate (β-TCP) for a novel toothpaste. The ion release, pH changes and ability to form fluorapatite was assessed to determine the bioactive properties.
Methods: F-BAGs were synthesised using the melt quench technique, dried, milled and sieved to obtain a particle size <45μm. β-TCP (~4μm, Budenheim, Germany) was mixed with the F-BAGs and immersed (75 mg) into 50mL of acetic acid (AA, pH 4.5) and artificial saliva pH7 (AS7) for up to 24 hours. At each timepoint, the solutions were filtered. The supernatant solutions were characterised using inductively coupled plasma-optical emission spectroscopy (ICP-OES), a fluoride ion-selective electrode (ISE) to measure the calcium, phosphorus and fluoride release, and the pH changes were also measured. The active ingredient was characterised using X-ray diffraction (XRD) and solid state ³¹P and ¹⁹F nuclear magnetic resonance (NMR) to detect fluorapatite formation.
Results: XRD demonstrated that the diffraction lines for β-TCP decreased and diffraction lines for apatite appeared and increased in intensity upon immersion into AA and AS7. ³¹P MAS-NMR showed the formation of a peak upon immersion at approximately 3.1ppm which is characteristic of apatite. This peak was sharper upon immersion in AA. ¹⁹F MAS-NMR exhibited a peak at approximately -102.5ppm upon immersion in both AA and AS7, confirming fluorapatite formation. Calcium, phosphorus, and fluoride release was confirmed via ISE and ICP-OES, and the pH in AA increased from 4.5 to 4.7.
Conclusions: The β-TCP dissolved upon immersion, dissociating into calcium and phosphate ions, which combined with the calcium, phosphate and fluoride released from the F-BAG to form an acid-resistant fluorapatite layer. Therefore, incorporating these mixtures into a toothpaste may provide an acid resistant fluorapatite layer, thereby reducing demineralisation, treat dentine hypersensitivity, and promote remineralisation.