Abstract
Bioactive glasses (BG) are used to regenerate bone, as they degrade and release therapeutic ions. Glass ionomer cements (GIC) are used in dentistry, can be delivered by injection and set in situ by a reaction between an acid-degradable glass and a polymeric acid. Our aim was to combine the advantages of BG and GIC, and we investigated the use of alkali-free BG (SiO2-CaO-CaF2-MgO) with 0 to 50% of calcium replaced by strontium, as the beneficial effects of strontium on bone formation are well documented. When mixing BG and poly(vinyl phosphonic-co-acrylic acid), ions were released fast (up to 90% within 15 minutes at pH 1), which resulted in GIC setting, as followed by infrared spectroscopy. GIC mixed well and set to hard cements (compressive strength up to 35 MPa), staying hard when in contact with aqueous solution. This is in contrast to GIC prepared with poly(acrylic acid), which were shown previously to become soft in contact with water. Strontium release from GIC increased linearly with strontium for calcium substitution, allowing for tailoring of strontium release depending on clinical requirements. Furthermore, strontium substitution increased GIC radiopacity. GIC passed ISO10993 cytotoxicity test, making them promising candidates for use as injectable bone cements.
Highlights
In 2010, about 5.5% of the EU population were diagnosed with osteoporosis, with 22% of women aged 50 and above (Hernlund et al, 2013)
Therapeutic ion-releasing bioactive glass ionomer cements between a polymeric acid [such as poly(acrylic acid), PAA] and a degradable glass (Wilson, 1996)
This was accompanied by a release of ions (Figure 2B), where a very fast release was observed within the first minutes of the experiments, FIGURE 1 | (A) X-ray diffraction (XRD) patterns of the glasses, showing the typical amorphous halo. (B) differential thermal analysis (DTA) traces of the glasses, showing glass transition temperatures (Tg) highlighted by arrows and crystallization exotherms
Summary
In 2010, about 5.5% of the EU population were diagnosed with osteoporosis, with 22% of women aged 50 and above (Hernlund et al, 2013). Bone mass and density are reduced, owing to osteoclasts resorbing too much bone and osteoblasts not forming enough new bone, resulting in an increased risk of fractures. Vertebroplasty and kyphoplasty are common procedures which restore fractured vertebrae by injecting a bone cement such as poly(methyl methacrylate) (PMMA) (Lewis, 2006), and the aim is to relieve pain while restoring dimensions and strength of the vertebrae. Therapeutic ion-releasing bioactive glass ionomer cements between a polymeric acid [such as poly(acrylic acid), PAA] and a degradable glass (Wilson, 1996). GIC form a chemical bond to bone (Wilson et al, 1983), which is in contrast to acrylic cements, where mechanical stability is achieved by mechanical interlocking only
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