Resin-modified glass-ionomers

This paper reviews the current status of resin-modified glass-ionomers and presents the results of recent findings of research in some key areas. The debate on nomenclature pertaining to these products is perceived as being pointless and the need for application-based ISO standards is raised. Setting characteristics are similar in many respects to those of light-activated composites, although some products have limited working time due to the influence of the acid-base setting reaction and sensitivity to ambient light. Water absorption and swelling are generally very high. The clinical significance of swelling after water exposure is unknown. Mechanical properties of most materials lie between those of the composites and conventional glass-ionomers depending upon the resin content of the matrix phase of the set material. Some products demonstrate an inherent adhesion to enamel, although etching may be required in order to make the bond clinically effective. Bonding to dentine is probably through a more complex mechanism than that involved with conventional glass-ionomers. Conditioning and priming of dentine is often advocated. Fluoride release rates and their clinical significance is an area which requires clarification and standardization. The key factor appears to be the frequency with which the storage water is changed. Equilibration is reached within minutes for some materials and their true fluoride-releasing potential can only be judged under dynamic test conditions.