Effect of immersion in different media on the color stability, surface roughness, and microhardness of flowable nanohybrid resin composites

To evaluate color stability, surface roughness, and microhardness of flowable nanohybrid resin composites following immersion in different media. Polofil NHT Flow (VOCO GmbH), G-aenial Universal Injectable (GC DENTAL PRODUCTS CORP), and Tetric N-Ceram (Ivoclar Vivadent) were used. From each tested resin composite, 50 disc-shaped specimens (10-mm diameter × 2-mm thickness) were performed. Each group was categorized into five subgroups according to immersion media (n = 10): (1) control (without immersion), (2) artificial saliva, (3) coffee, (4) cola, and (5) energy drink. Color stability, surface roughness, and microhardness were evaluated. Data were analyzed through two-way ANOVA, Tukey’s post-hoc, and Pearson correlation coefficient tests (p < 0.05). For color change, no statistically significant differences were observed among the resin composites regarding artificial saliva (p = 0.78), coffee (p = 0.93), and cola (p = 0.09), while there was a significant difference between them regarding energy drink (p < 0.05). The highest surface roughness mean value was recorded with Polofil NHT Flow, which showed an increase in surface roughness after immersion in energy drink (0.32 ± 0.06 μm) compared to the control subgroup (0.22 ± 0.08 μm). For all resin composites, there were significant reductions in microhardness with all immersion media in comparison to the control subgroups (p < 0.05). For color stability, energy drink and coffee had the most negative effect on all tested resin composites. Energy drink caused the highest discoloration with G-aenial Universal Injectable and the highest roughness with Polofil NHT Flow. All tested resin composites showed a decrease in surface microhardness following immersion in all tested immersion media.