The effect of storage in aqueous solutions on glass-ionomer and zinc polycarboxylate dental cements

Cylindrical specimens (dimensions 6 mm diameterx12 mm height) of glass-iono mer and of zinc polycarboxylate dental cement have been stored in aqueous s olutions for periods of 24 h, 1 week and 1 month. The solutions were of var ying composition and affinity for water, and storage in them resulted in fl uctuations in mass of the cements, an effect which was attributed to differ ences in the partitioning of water between the solutions and the cement spe cimens. Unlike the zinc polycarboxylate, the glass-ionomer gained mass in m ost of the solutions examined (except Na2SO4), showing it to have a much gr eater affinity for water than the zinc polycarboxylate. Despite the fluctua tions in water uptake by the glass-ionomer, and loss of water by the zinc p olycarboxylate, no statistically significant differences in compressive str ength were recorded in any solution at any storage time. This contrasts wit h results reported previously for zinc polycarboxylates using smaller speci mens, showing that specimen size has an influence on the interaction of cem ents with storage solutions. (C) 2000 Kluwer Academic Publishers.