The purpose of this study was to compare the fluoride release and direct te
nsile strength at 24 h, 1 month, and 3 months of two conventional glass-ion
omers, two visible light-cured resin-modified glass-ionomers, a polyacid re
sin composite and two resin composites. The results were statistically anal
ysed using ANOVA and Fisher's PLSD at alpha = 0.05. The data on fluoride re
lease indicated that the immersion period (24 h, 1 month, and 3 months) sig
nificantly 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-modi
fied 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, thi
s material also reduced the fluoride availability.