The mechanical and other properties of ionomer cements
Ionomer cements, a novel composite material, are formed at ambient temperatures by mixing an aqueous polyacid with an ion-leachable powder. The glass ionomer cement known as ASPA, a dental restorative material, produces strong and hydrolytically stable cements. Applications of this material outside of dentistry have been restricted by its rapid set, its poor mechanical performance in dry environments and its. highcost. The objective of this research have been to modify the ASPA system and develop other ionomer cements for applications outside of dentistry and to provide a further understanding of the mechanical properties of ionomer cements. The rapid set of ASPA cements was reduced by acid treatment of the ion-leachable glass. Cements prepared from this acid treated glass (ATG) were mechanically superior to the ASPA cements and retained their mechanical properties in environments of low humidity due to a greater extent of aluminium polyacrylate formation than in the ASPA cement. The rapid set of the ASPA system was also reduced by replacing the ionleachable glass with various fillers. The mechanical properties of these filled ASPA cements were dependent upon the physical characteristics of the filler and were poor in low humidity environments. Other zinc-glass ionomer cements and certain treated mineral ionomer cements showed promise as low cost alternatives to the ASPA glass. The mechanical properties of ionomer cements were dependent upon the size and packing properties of the glass particles, the volume fraction of glass in the cement and the interfacial wetting properties between the glass and the polyacid matrix. Ionomer cements were mechanically superior and more resistant to hydrothermal ageing than epoxy and polyester composites. It was proposed that this was due to a more water tolerant matrix and due to stable primary interfacial bonds being formed at the glass-polyacid interface.