In vitro effect of simulated brushing on color stability, surface roughness, and microbial adhesion of characterizing resin composites for 3D-printed denture bases.

This in vitro study evaluated the effect of simulated brushing on color stability, surface roughness, and microbial adhesion of resin composites with different viscosities applied to denture base materials. Disc-shaped specimens (10 × 3.0 mm) were fabricated using a 3D-printed denture base resin and heat-polymerized resin. Three extrinsic characterizations (2 mm thick) were applied to the 3D-printed resin specimens: one regular-viscosity (RV) and two low-viscosity (LV49, LV30), and light-cured. The heat-polymerized resin group (STG) was fabricated and characterized using a compression-molding technique. Color coordinates and color stability (ΔE00) were measured using a colorimeter; surface roughness (Ra) was assessed using an optical profilometer; and microbial adhesion (Candida albicans, log CFU/mL) was evaluated before and after 20,000 brushing cycles. Color and roughness data were analyzed using the Kruskal-Wallis test and the Wilcoxon signed-rank test, while microbial adhesion was analyzed using one-way ANOVA followed by Tukey's post hoc test (α = 0.05). STG and LV49 exhibited greater color changes than did LV30 (p < 0.05), but all groups remained within clinically acceptable limits (ΔE00 ≤ 2.25). Brushing increased surface roughness in all groups except STG (p < 0.05). Microbial adhesion increased after simulated brushing (p < 0.05); however, no significant differences were observed between the groups (p > 0.05). Simulated brushing affected color stability, with some groups exhibiting clinically noticeable changes. It increased surface roughness in characterizing resin composites and enhanced Candida albicans adhesion in all groups, with no significant differences between materials.