Conventional glass-ionomer materials: A review of the developments in glass powder, polyacid liquid and the strategies of reinforcement

The development of glass-ionomers (GIs)from the earliest experimental GI formulations to the modern day commercially available GIs was reviewed. The aim of the review was to identify the developments in the glass powder and polyacid liquid consti-tuents of GIs since their inception in the late 1960s. Data: The glass powder has undergone major changes from the earliest GI powder formu- lation (G200)in an effort to enhance the reactivity with the polyacid liquid. The GI liquids have also been optimised by the manufacturers in terms of polyacid composition, molecular weight and concentration to improve the handling characteristics. Despite these develop-ments in the glass powder and polyacid liquid constituents, GIs cannot 'truly' be advocated for the restoration of posterior dentition due to the poor mechanical properties when compared with dental amalgam and resin-based composites (RBCs). Sources: Various attempts to improve the mechanical properties of GIs through substitution of reinforcing fillers to the GI powder or modification of the GI liquid were identified in the dental literature. Despite the claimed improvements in mechanical properties of the modified GIs, a wide variation in mixing and testing conditions was identified which prevented a valid assessment of the reported reinforcement strategies. When investigating a GI reinforcement strategy it is crucial that the mixing and testing conditions are stan-dardised to allow a valid comparison between studies. Conclusion: Nevertheless, major improvements in GI formulations through a reinforcement strategy have yet Q2 to be made to enable clinical usage of GIs for the restoration of posterior dentition.