Conventional glass ionomers as posterior restorations. A status report for the American Journal of Dentistry

Abstract

The search for a material to replace amalgam continues as a major quest in materials science. Resin composites may offer one solution but an alternative class of material, the glass ionomer cements (GICs) may have some potential for fulfilling this role. GICs were first introduced to the dental profession in 1976, and have now become an accepted part of the dental armamentarium, especially for use in low load bearing situations. They possess a low coefficient of thermal expansion similar to that of tooth structure, physicochemical bonding to both enamel and dentin, and the release of fluoride ions into the adjacent tooth tissue. These properties help to reduce marginal leakage and may contribute to a reduced incidence of recurrent decay in the restored tooth. Fluoride released into the ambient fluids has a caries-preventive effect in neighboring teeth by enhancing remineralization and inhibiting demineralization of the dental hard tissues. The main criticisms of the GICs are their brittleness, poor surface polish, porosity and surface wear. To overcome some of these deficiencies, considerable attention has been directed at improving their physical properties, especially with the addition of metal powders, the metal-modified GICs. Different metal powders have been tried, including alloys of silver and tin, pure silver, gold, titanium, palladium and stainless steel. There is conflicting data as to whether or not these materials are sufficiently strong for use in high stress restorations, especially their potential use as replacement materials for amalgam fillings.