Materials and Methods: A total of 350 bar-shaped specimens (25mm x 2 mm x 2 mm) were prepared for testing in a 3-point-bending test at a cross-head speed of 1 mm/min. Before testing, specimens were subjected to 5 different storage conditions (10 min dry incubator storage at 37°C, 10 min incubator storage to be followed by 2h or 24h or 7d in distilled water at 37°C or 7d thermocycling (5000x,5-55°C). All data were tested for normal distribution (Kolmogorov Smirnov) and afterwards subjected to a 2-way ANOVA to analyze the parameters ‘material type' and ‘storage condition'.
Results: Conventional GI cements showed the lowest and the compomer the highest FS and FM values. After 10 min dry storage all materials showed lower properties. Values after 7d storage at a) 37°C or b) thermocycling at 5-55°C were almost similar for all materials; except for a conventional GI showing significantly lower FM after thermocycling.
Conclusions: Resin-modification improved flexural properties of GIC. The compomer showed better properties compared to the SC CR. Within the limits of this study, it can be concluded, that due to the early sensitivity and brittleness of GI-based core-buildup materials, patients should be advised to be careful for the first 24h.