Clinical performance of glass-ionomer cements

Glass-ionomer cements were developed by Wilson and McLean at the Laboratory of the Government Chemist in England in 1965. They were a logical addition to the family of water-based dental cements, comprising silicate cement, zinc phosphate cement and zinc polycarboxylate cement. Since their commercial introduction, they are now available in essentially two types. ‘Conventional’ glass-ionomers consist of a fluoroaluminosilicate glass, usually a strontium or calcium salt, and polyalkenoic acid liquid, for example polyacrylic, maleic, itaconic and tricarbalyllic acids. The conventional materials sent by an acid-base reaction between the acidic liquid and the basic powder. More recently, in order to improve the physical properties and decrease the water sensitivity of the conventional materials, the so-called resinmodified glass-ionomer cements have become available. These contain a polymerisable resin, commonly hydroxyethylmethacrylate (HEMA), and therefore have the additional setting reaction of resin polymerisation, which may be selfcure and/or light-cure. The significant properties of the glassionomers are adhesion to calcified tooth structure, release of fluoride, minimal effect on the pulp, and that they are tooth-coloured. However, they are sensitive to dehydration early in the setting process, particularly the conventional cements, and they are brittle materials and therefore unsuitable for use in load-bearing areas. In view of these properties, they have a wide range of uses, including fissure sealants, anterior approximal Clinical performance of glass-ionomer cements