Bioactive glass three decades on.

Bioglasses were first introduced in the early 1970s and since have found wide use in dentistry. The original 45S5 bioglass, as described by Hench, is a silica-based melt-derived glass characterized by a Si02 content of less than 60%, a high Na2O and CaO content, and a high CaO:P2O5 ratio. Bioactivity has been defined as the ability of an implant to form a bond with living tissue. These glasses exhibit bone bonding, a phenomenon also observed with other bioactive ceramics. This process is a result of the surface reactive silica, calcium, and phosphate groups that are characteristic of these materials. Silica is believed to play a critical role in bioactivity. Bioactive glass is a very biocompatible material. There is a good deal of experimental data supporting its use in a variety of clinical applications, including ridge preservation, sinus augmentation, and the repair of periodontal bone defects. There are limitations inherent in the bioglass products that are currently available. They are granular in nature and cannot be depended upon to serve reliably as space-making devices. Although they are quite biocompatible and exhibit bone bonding, bioglasses are not osteoinductive and are not capable of forming bone in ectopic sites (although they can be used to deliver osteopromotive growth factors). The range of applications for these products could be extended if the material could be made in various space-making forms. Incorporation or coating with osteogenic agents such as growth factors might be worthwhile. The full potential of bioactive glasses has yet to be fully realized.