CHANGES IN COMPRESSIVE STRENGTH ON AGING IN GLASS POLYALKENOATE (GLASS-IONOMER) CEMENTS PREPARED FROM ACRYLIC MALEIC ACID COPOLYMERS/

Previous studies have shown that glass-ionomers made from acrylic/male ic acid copolymers stored in water reach a maximum strength at about 1 week, and after 4 months have become significantly weaker. This findi ng, which contrasts with the behaviour of glass-ionomers based on poly (acrylic acid), was originally attributed to hydrolytic instability. T his interpretation has been tested in the current work. Specimens of g lass-ionomer prepared from acrylic/maleic acid copolymer have been sto red for up to 4 months in different media, namely deionized water, dry air and vegetable oil, then tested for compressive strength. Specimen s were in the form of cylinders of dimensions 6 mm high x 4 mm diamete r, and storage temperature was 37 degrees C. Data were analysed using two-way analysis of variance (ANOVA) and in all three media specimens became weaker at 4 months than they had been at 1 week (P < 0.05). How ever, for the specimens stored in dry air and in water, the 1-week val ues were not the maximum. The fact that there was a loss of strength u nder all conditions led to the conclusion that it is not, after all, d ue to hydrolysis. (C) 1996 Elsevier Science Limited