Welcome to the Glass Age

52 aluminosilicate glass, can dissolve rapidly when in contact with acids. When a fine powder of such a glass is mixed with an acidic polymer, for example poly(acrylic acid), the glass dissolves and releases ions such as aluminium and calcium. These ions then bond to the polymer, and together ions and polymer form a strong cement (Figure 3.8). These cements, called glass ionomer cements [14], have been used in dentistry for several decades now to treat minor cavities, as adhesives (“glue”) or as sealants to prevent new caries forming in the grooves (fissures) on the top of our teeth. As the glass used also contains fluoride Figure 3.9. Schematic of the atomic structure of a set glass ionomer cement: ionic cross-linking between functional groups (e.g. carboxylate groups; blue) attached to polymer chains (black) and metal cations (red). Source: P. Wiemuth, University of Jena.