POSTIRRADIATION HARDNESS OF RESIN-MODIFIED GLASS-IONOMER CEMENTS AND A POLYACID-MODIFIED COMPOSITE RESIN

This study examined the post-irradiation hardness of resin-modified gl ass ionomer cements and a polyacid-modified composite resin using a di gital microhardness tester. Change in hardness of these materials over a period of 6 months was compared to that of conventional glass ionom er cements and a composite resin. With the exception of the composite resin, all materials showed a significant increase in hardness over 24 h after their initial set. Dual-cure resin-modified glass ionomer cem ents showed decreased hardness with increased storage time in saline a t 37 degrees C. Results suggest that the addition of resins to glass i onomer cements does not improve initial hardness and does not negate t he acid-base reaction of conventional cements. Resin addition may, how ever, lead to increased water sorption and decreased hardness.