Zinc Interaction with Glass-Ionomer Restorative Materials

The purpose of this study was to evaluate the effect of addition of zinc sulfate to conventional and resin-modified glass ionomer restorative materials. The samples were prepared by addition of zinc sulfate to glass ionomer at different concentrations. The samples were tested for fluoride, zinc and aluminum release at different time intervals. The antibacterial activity of the restorative materials was tested at 24 and 48 hours. The hardness and diametral tensile strength were measured at 24 hours and 2 weeks. All materials showed highest initial fluoride, zinc and aluminum release rates during the first 2 to 3 days, dropping quickly over 2 weeks and becoming largely stabilized near the test period. The conventional materials released more fluoride and aluminum than that of resin-modified material. Zinc addition increased inhibition of S. mutans growth without threatens the diametral tensile strength and hardness of the tested glass-ionomer materials. Conventional glass-ionomer showed inhibition activity against S. mutans greater than that of resin-modified materials did. Resin-modified glass ionomer showed no significant difference in the inhibitory action. There was highly positive correlation between fluoride, zinc and aluminum release. Chemically-activated materials showed positive and highly significant correlation between ionic release and antibacterial action, while light cured materials showed no significant correlation. There were highly negative correlation between fluoride, zinc, aluminum released and mechanical properties, i.e., restorative materials with high fluoride, aluminum release have lower mechanical properties. Storage of specimens in water for 2 weeks leads to increased diametral tensile strength and hardness of all materials