Comparison of Water Sorption and Solubility of Conventional and Bulk-Fill Composites at Different Depths Over Two Time Intervals

Bulk-fill composites are a class of restorative materials introduced to speed up the restoration process in the posterior area. This study aimed to compare the water sorption and solubility of a bulk-fill resin composite with its conventional counterpart at various depths after one week and one month of water storage. Five cylindrical specimens (15 × 8 mm) of each composite resin, Tetric N Ceram Bulk fill and Tetric N Ceram (Schaan, Liechtenstein: Ivoclar Vivadent), were prepared using a metal split mold. The conventional composite was placed incrementally in 2 mm layers, while the bulk-fill composite was applied in a single layer. Specimens were cured and polished, then cut into disc-shaped samples (1 mm thickness and 15 mm diameter) (n=40, five disks per depth for each composite). Water sorption and solubility were assessed after one week and one month of immersion in distilled water at 37±1 °C. Statistical analysis was performed using repeated measures analysis of variance and t-test (p≤0.05). The bulk-fill composite exhibited significantly higher water sorption and solubility than the conventional composite at all depths measured. Water sorption and solubility increased with depth and were significantly greater after one month compared to one week. The bulk-fill composite demonstrated higher water sorption and solubility compared to the conventional composite, with significant variations observed at different depths over time. A conventional composite may work better in terms of water sorption and solubility, and must be considered in extensive posterior restorations.