THE INFLUENCE OF WATER SORPTION ON THE DEVELOPMENT OF SETTING SHRINKAGE STRESS IN TRADITIONAL AND RESIN-MODIFIED GLASS-IONOMER CEMENTS

Objectives. The aim of this study was to determine the setting stress development for some traditional and resin-modified glass ionomer ceme nts and to assess the effect of early water exposure to this stress. M ethods. The development of the setting stress of the glass ionomer cem ents was determined in a tensilometer set-up as described earlier by F eilzer ef al. (1987). Results. The results of this study show the infl uence of water sorption on the development of setting shrinkage stress in bonded glass ionomer cements. When curing took place under isolate d conditions (no hydration or dehydration), all the traditional glass ionomer cements investigated fractured spontaneously, either adhesivel y and/or cohesively, due to the developing stress. Early exposure to w ater led to stress relief and prevented spontaneous fracturing. For th e light-cured products, no spontaneous failures were observed under is olated conditions. Stress relief due to water sorption reversed the co ntraction stress into an expansion stress. Significance. Exposure of t raditional glass ionomer cements to water at an appropriate time by th e use of permeable matrix systems is advised. Whether the conversion o f contraction stresses into expansion stresses, as observed for the re sin-modified products, is beneficial for a restoration requires furthe r study.