Glass-ionomers: bioactive implant materials

Glass-ionomer cements (GICs) originally designed for use as dental materials have a number of advantages over acrylic bone cements. These include lack of exotherm during setting, absence of monomer and improved release of incorporated therapeutic agents; this has resulted in the development of GICs for biomedical applications. Major landmarks in this history are the formulation of defined-composition ionomer glasses and an improved understanding of the biological and material properties of GICs. Following implantation, GICs can form a stable integration with bone, and affect the growth and development of bone, both adjacent to their surface and systemically, through an ion release mechanism. The ‘non-inert’ nature of this group of materials is also demonstrated by their adverse effects on neural tissue. Successful clinical use of GICs, both as bone cements and as preformed implants for hard tissue replacement, have been reported in the fields of otologic surgery (Cochlear implant fixation, repair of the tympanic chain, eustation tube obliteration and as ear ossicles), and oral and reconstructive surgery. The use of GICs in situations where they will come into contact with nerves or neural tissue is contraindicated.