Apatite formation on novel Boron and Fluoride-containing bioactive glasses

With the expanding use of bioactive glasses (BAGs) in dentistry and medicine, there is a need for greater control over the degradation behavior and durability of these materials.

Objective: We examined the effect of frequently used modifiers of melt-derived

glasses (boron, and fluoride) on mineralization capability and hence bioactivity of sol gel-derived BAGs.

Methods: BAGs were prepared by sol-gel methods with the following compositions: 65%SiO₂-31%CaO-4%P₂O₅ (BAG-1); 75%SiO₂-21%CaO-4%P₂O₅ (BAG-2); and 85%SiO₂-11%CaO-4%P₂O₅ (BAG-3); 84%SiO₂-31%CaO-4%P₂O₅-1%B₂F₃ (BAG-4); 64%SiO₂-31%CaO-4%P₂O₅-1% B₂F₃ (BAG-5); 80%SiO₂-11%CaO-4%P₂O₅-1%B₂O₃ (BAG-6). The BAGs were ground and micronized to obtain powders. They were immersed in SBF for 1, 3, and 7 days with continuous agitation at 37 „aC. Apatite formation at each time point was assessed using powder KBr pellet methods and FT-IR spectroscopy. Peaks near 565 and 603 cm^-1 were considered to be characteristic for hydroxylapatite (HA). Commercially available melt-derived BAGs were used as a reference.

Results: All BAGs, including the controls, formed apatite within 24 hours, and the relative amount of HA slightly increased over 7 days, indicating that the presence of B and F^- in our formulations did not adversely affect the ability to form HAP. On all samples, there was an initial small carbonate apatite (CA) layer formed, with BAG-4 (containing both B and F^-) unique in forming a substantial CA layer after 24 hours. After prolonged exposure, BAG-5, also containing B and F^-, also formed a large CA fingerprint. These results were unique for these glasses.

Conclusion: All of the BAGs formed HA on their surfaces. The addition of B and F^- to the composition did not inhibit this formation, but rather may additionally help to foster the development of substantial CA on the surface.