Coating Agents for Resin Composites: Effect on Color Stability, Roughness, and Surface Micromorphology Subjected to Brushing Wear

This study evaluated the influence of six resin composite coating agents on color stability and surface roughness after toothbrushing abrasion. Discs (Ø6 mm x 2 mm) of nanofilled resin composite (Filtek Z350XT) were prepared for application of coating agents (n=10): control (absence), two surface sealants (PermaSeal and BisCover LV), two adhesive systems (Scotchbond Multi-Purpose Adhesive/3M Oral Care and Single Bond Universal), and two modeling liquids (Modeling Resin and Composite Wetting Resin). CIELab*, WID, and color change (ΔEab, ΔE00, and ΔWID) were analyzed at baseline, after finishing and polishing, after application of coating agents, after coffee staining (simulating 30 days and one year of staining), and after toothbrushing abrasion. Roughness evaluations (Ra) were performed at the initial time point, after finishing and polishing, after application of coating agents, and after toothbrushing abrasion. Surface micromorphology was evaluated (2,000×) before and after toothbrushing abrasion. Generalized linear mixed models or Kruskal-Wallis and Dunn tests (α=0.05) showed that L* decreased significantly (p<0.0001) and a* increased significantly in all the groups after staining (p<0.0001). After toothbrushing, Modeling Resin showed higher ΔEab and ΔE00 than the control, Scotchbond Multi-Purpose Adhesive, Composite Wetting Resin, PermaSeal, or BisCover LV (p<0.0001). There was a significant increase in roughness for Composite Wetting Resin, Modeling Resin, and PermaSeal after application of the agents (p<0.05), but a significant decrease for BisCover LV (p<0.05), which achieved high surface smoothness. After abrasive wear, BisCover LV showed the lowest roughness values among all agents. Composite Wetting Resin and Modeling Resin showed higher roughness than the other groups (p<0.05), and surface irregularities. In conclusion, the coating agents did not prevent coffee staining, and they also led to increased surface roughness, with only BisCover LV providing greater surface smoothness after toothbrush abrasion.