Effects on adjacent enamel and dentin of restorations using bioactive materials under laboratory caries condition

This study evaluated the cross-sectional Knoop microhardness (KHN) of enamel and dentin adjacent to restorations made with bioactive materials, and their surface degradation after pH cycling.

Molar blocks (n=10) were restored with conventional resin composite (RC; Z350XT), resin-modified glass-ionomer cement (R-GIC; Vitremer), flowable compomer (FC; Twinky), resin composite with S-PRG filler (RC-S-PRG; Beautifil II), or self-curing bioactive composite (RC-SP; Cention N). After pH cycling, KHN was measured at 100, 200, and 300 µm from the restoration margins and at depths of 20, 40, and 60 µm from the surface. Surfaces were evaluated using scanning electron microscopy (SEM). Data were analyzed via split-plot ANOVA and Tukey's test (α=0.05).

Regardless of material, enamel KHN was lower at 20 µm than at 60 µm depth (100 µm distance), at 40 µm than at 60 µm depth (300 µm distance), and dentin KHN was also lower at 20 µm. RC and R-GIC showed reduced dentin KHN at 20 µm compared to 60 µm. SEM analysis revealed surface degradation in all materials (RC

The ion-releasing bioactive materials did not provide superior protection of microhardness compared with the conventional composite. Moreover, bioactive materials exhibited greater surface degradation after acidic challenge, which may compromise their long-term stability in the oral environment.