Bioactive glasses (BG) which contain strontium have the potential to combine the known bone regenerative properties of BG with the anabolic and anti-catabolic effects of strontium cations. Here we created a BG series (SiO 2 -P 2 O 5 -Na 2 O-CaO) in which 0 to 100% of the calcium was substituted by strontium and tested their effects on osteoblasts and osteoclasts in vitro. We show that ions released from strontiumsubstituted BG enhance metabolic activity in osteoblasts. They also inhibit osteoclast activity by both reducing tartrate resistant acid phosphatase activity and inhibiting resorption of calcium phosphate films in a dose-dependent manner. Additionally, osteoblasts cultured in contact with BG show increased proliferation and alkaline phosphatase activity with increasing strontium substitution, while osteoclasts adopt typical resorption morphologies. These results suggest that similarly to the osteoporosis drug strontium ranelate, strontium-substituted BG may promote an anabolic effect on osteoblasts and an anti-catabolic effect on osteoclasts. These effects, when combined with the advantages of BG such as controlled ion release and delivery versatility, may make strontium-substituted BG an effective biomaterial choice for a range of bone regeneration therapies.

Effect of fluoride content of bioactive glasses on apatite deposition in simulated body fluid 2/15Summary Bioactive glasses are able to bond to bone through formation of carbonated hydroxyapatite in body fluids, and fluoridereleasing bioactive glasses are of interest for both orthopaedic and in particular dental applications for caries inhibition.Melt-derived glasses in the system SiO 2 -P 2 O 5 -CaO-Na 2 O with increasing amounts of CaF 2 were prepared by keeping network connectivity and the ratio of all other components constant.pH change, ion release and apatite formation during immersion of glass powder in simulated body fluid at 37°C over up to two weeks were investigated. Crystal phases formed in SBF were characterised using infra-red spectroscopy, X-ray diffraction with Rietveld analysis and solid-state nuclear magnetic resonance spectroscopy ( 19 F and 31 P MAS-NMR).Results show that incorporation of fluoride resulted in a reduced pH rise in aqueous solutions compared to fluoride-free glasses and in formation of fluorapatite (FAp), which is more chemically stable than hydroxyapatite or carbonated hydroxyapatite and therefore is of interest for dental applications. However, for increasing fluoride content in the glass, fluorite (CaF 2 ) was formed at the expense of FAp. Apatite formation could be favoured by increasing the phosphate content in the glass, as the release of additional phosphate into the SBF would affect supersaturation in the solution and

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SummaryFluoride prevents dental cavities, stimulates bone mineralisation and decreases the melting temperature of glasses and is therefore an interesting component of bioactive glasses for use as dental or orthopaedic biomaterials. However, when designing new glass compositions, the structural role of fluoride in the glass needs to be better understood. We have characterised a glass series in the system SiO 2 -P 2 O 5 -CaO-Na 2 O with increasing concentrations of CaF 2 . Network connectivity was fixed at 2.13 by adding CaF 2 while the ratio of all other components was kept constant. 19