Effect of Water Storage on Microleakage of Class II MOD Bulk-fill Resin Composite Restorations: In Vitro Evaluation

Abstract To evaluate and compare the effect of 6-month water storage on the marginal microleakage of class II MOD cavities restored with two different bulk-fill resin composites (sculptable and no-cap flowable) and a conventional resin composite. A total of 60 sound freshly extracted mandibular molars, each with a standardized class II MOD cavity, were assigned into three main groups according to the restorative material used as follows: bulk-fill resin composite (SimpliShade, Kerr), no-cap flowable bulk-fill resin composite (G-aenial Bulk Injectable, GC), and conventional resin composite (Neo Spectra ST LV, Dentsply Sirona). Each group was further divided into two subgroups (n = 10) based on the water-storage time: 24 hours (immediate) and 6-month water storage (aged). All specimens were thermocycled 5,000 times between 5°C ± 2°C and 55°C ± 2°C, then immersed in 2% basic fuchsin dye for 24 hours. The specimens were longitudinally sectioned, and the amount of dye penetration was evaluated using stereomicroscope under 25× magnification. The results were analyzed by non-parametric Kruskal-Wallis, Mann-Whitney, and Wilcoxon signed-rank tests. The level of significance was set at p