Photo-curing and storage time influences on volumetric change of resin-modified-glass-ionomer-cement

Objectives: This study evaluated the effect of photo-ativation and storage on the hygroscopic expansion of resin-modified glass-ionomer-cements (RMGIC).Methods: RMGIC (Vitremer (VT) - 3M/ESPE and Fuji II LC (FJ)- GC Int.) were manipulated according to the manufacturer's instructions and inserted into a PTFE mold, 5mm in diameter and 2mm in thickness, under two glass microscope slides and kept in darkness for 15 minutes. The samples were distributed into four groups (n=5): light-cured for 20s, light-cured for 40s, light-cured for 60s and no light-cured (control groups).Each sample was storage in distilled water at 37ºC. The measurements of volumetric changes were made in three different times of storage: 24 hours, 7 days and 30 days. Volumetric changes were determined using Archimedes principle, which change in buoyancy of a material in a fluid depends on the volume changes of the material. Measurements were done using an analytic balance with density apparatus (AT 261 Delta Range/Mettler Toledo). Mean values(%) were analyzed by three-way ANOVA and Tukey's test(p=0.05). Results: after 24hours, 7 days and 30 days of storage, respectively: VT no light-cured: 0.91(1.62), 0.30(1.73) and 0.42(1.51) ; VT 20s: 5.35(0.84),5.44(0.69)and 5.72(0.69);VT 40s: 4.25(0.52),4.87(0.61)and 4.76(0.66);VT 60s:4.01(1.27), 5.17(0.77)and 5.02(0.77); FJ no light-cured: 5.24(1.01), 5.78(0.78)and 5.19(1.01); FJ 20s:5.81(1.11),6.22(0.91)and 6.10(1.22); FJ 40s: 5.44(1.22),6.08(1.09)and 6.14(1.26);FJ 60s: 5.83(0.26),6.69(0.76)and 6.72(0.89).Conclusions: All materials showed volumetric expansion with time, except for the specimens not light-cured. The absence of light-cure influenced volumetric change of Vitremer. The time of light-curing influenced the volumetric change of Fuji II LC, that showed more expansion when activated for 60s.