Surface properties of direct restorations and adjacent dental tissues after saliva exposure

This study assessed the effect of saliva exposure on roughness (Ra) and Vickers hardness (VHN) of two direct restorative materials, enamel, and dentin adjacent to the restorations. Enamel and dentin cavities in molars (n = 10) were restored with a) bulk-fill resin composite (Tetric N-Flow Bulk Fill, BF) with the application of a universal adhesive (Tetric N-Bond Universal) and b) alkasite restorative material (Cention N, CN) with and without the application of a universal adhesive. After 24 h (baseline), surface roughness and hardness of the restorative material and dental tissues were assessed at 100 μm from the tooth/restoration interface. The specimens were subjected to degradation in whole saliva for 7 days (combined with the application of 20% sucrose 10x/day). Ra and VHN were then reassessed. The data were analyzed by ANOVA and Tukey's test (α = 5%). BF exhibited a significantly lower Ra than CN. Ra increased significantly after degradation in saliva when compared to baseline values. Enamel hardness was higher for BF restorations. No differences in enamel hardness were observed for alkasite restorations with and without adhesive application. For dentin hardness, significantly lower values were found in alkasite restorations with previous application of an adhesive system. It can be concluded that BF had a smoother surface than CN before and after degradation. Immersion in saliva reduced the hardness of both restorative materials, enamel, and dentin adjacent to the restoration.