Direct tensile strength of visible light-cured restorative materials containing fluoride

The purpose of this study was to compare the fluoride release and direct tensile strength at 24 h, 1 month, and 3 months of two conventional glass-ionomers, two visible light-cured resin-modified glass-ionomers, a polyacid resin composite and two resin composites. The results were statistically analysed using ANOVA and Fisher's PLSD at alpha=0.05. The data on fluoride release indicated that the immersion period (24 h, 1 month, and 3 months) significantly influenced the cumulative amount of fluoride released (P < 0.001). The direct tensile strengths after 1 month of storage were significantly higher than those after 24 h or 3 months of storage (P < 0.001). Thus, the cements and resins were not weakened by the loss of fluoride. Conventional glass-ionomer cement showed the lowest direct tensile strength. Resin-modified glass-ionomer behaved in between the resin composites and conventional glass-ionomers in terms of all three testing times, however, the polyacid resin composites most closely resembled the resin composites. The polyacid resin composites had greatly enhanced direct tensile strength, however, this material also reduced the fluoride availability.