Effect of Finishing Protocols and Simulated Toothbrushing on the Surface Roughness and Color Stability of Conventionally and Digitally Fabricated Interim Restorative Materials

Background/Objectives: This in vitro study evaluated the effects of manufacturing technologies and finishing protocols on the color stability (ΔE00) and surface roughness (Ra) of five interim restorative materials after simulated toothbrushing. Methods: A total of 180 disk-shaped specimens (10 mm × 2 mm) were fabricated from five interim restorative materials (n = 36 per material): conventional acrylic, bis-acryl composite, light-polymerized composite, 3D-printed resin, and CAD/CAM-milled PMMA. Specimens were assigned to three finishing protocol subgroups (n = 12): control, mechanical polishing, and surface sealant. Baseline surface roughness and color were measured using a profilometer and spectrophotometer. Specimens underwent 10,000 brushing cycles, simulating one year of clinical use. Surface roughness and color were measured before and after brushing, and CIEDE2000 color differences were calculated. Surface topographies were analyzed using SEM and AFM. Data were analyzed using two-way ANOVA (ΔE00), mixed-design ANOVA with material, finishing protocol, and time (Ra), and post hoc tests with Bonferroni adjustment where applicable (p <0.05). Results: Material type, finishing protocol, and their interaction significantly affected color change and surface roughness (p < 0.001). Brushing increased surface roughness across groups, and the increase depended on material, finishing protocol, and their combination (all time interactions p < 0.001), with specimens receiving no additional finishing treatment exceeding the frequently cited 0.20 µm roughness threshold associated with increased plaque accumulation. For conventional and composite materials, surface sealant resulted in the lowest surface roughness and favorable color stability. In contrast, mechanical polishing resulted in the lowest color change for the tested CAD/CAM and 3D-printed materials. For the tested CAD/CAM materials, mechanical polishing provided the lowest color change and surface roughness. Conclusions: Finishing protocols influenced the surface roughness and color stability of interim restorative materials after simulated toothbrushing. Within the materials and laboratory conditions tested, surface sealant application provided favorable outcomes for the conventional and composite-based materials, whereas mechanical polishing resulted in lower color change for the tested CAD/CAM-milled and 3D-printed materials.