Effects of immersion in coffee solution and brushing on the surface roughness and color change of 3D-printed resins

The objective of this study was to compare changes in the surface roughness and color of 2 types of resin formulated for 3-dimensional (3D) printing and 1 resin formulated for computer-aided design/computer-aided manufacturing (CAD/CAM) following immersion in coffee solution or distilled water and subsequent brushing. Cylindrical specimens were 3-printed with standard or long-term provi-sional resins or milled from CAD/CAM resin blocks (n = 22 per material). After polishing, baseline surface roughness (R_a) and color parameters (CIE L*a*b* and CIEDE2000) were recorded. For 30 days, half of the specimens of each material (n = 11) were immersed in a fresh coffee solution for 3 hours, while the other half were immersed in distilled water. All specimens were then submitted to 16,200 brushing cycles to simulate aging, and surface roughness and color parameters were remeasured. The data were compared according to restorative material, immersion solution, and measurement time using the Kruskal-Wallis and Dunn, Mann-Whitney U, and Wilcoxon tests, respectively, at a significance level of 5%. The surface roughness of the standard 3D-printed resin and the CAD/ CAM-milled resin increased significantly following immersion in distilled water (P < 0.05), but only the milled resin showed a significant increase in surface roughness after immersion in coffee (P < 0.05). For both 3D-printed resins, coffee immersion resulted in significantly greater color change than water immersion (P < 0.05). No significant color change differences among materials were observed after immersion in distilled water (P > 0.05). However, the CAD/CAM--milled resin showed significantly less color change than both 3D-printed resins following immersion in coffee (P < 0.05). The surface roughness of the long-term 3D-printed resin remained stable after aging. Immersion in coffee caused a more visible color change in the 3D-printed resins than in the CAD/CAM--milled resin.