Color stability, roughness and topography of 3D printed, subtractive, and conventional acrylic resins.

The aim of the study was to evaluate the color stability, translucency, roughness, and topography of acrylic resins fabricated through different methods. Discs (Ø=10 × 1.0 mm) of acrylic resins fabricated through different methods: 3D printing (PRINT), subtractive manufacturing (SUB), conventional pressing (PRESS Base and Tooth), and manual application against a mold (MOLD Base and Tooth). Acrylic resin disks (Ø= 10 mm × 1 mm thickness) were divided into six groups, corresponding to the different fabrication methods. Following preparation, the specimens were subjected to staining protocols using coffee (n= 6) and red wine (n= 6) solutions. Color coordinates (L*, a*, and b*) were recorded using a spectrophotometer (SP60; X-Rite) at baseline and after staining. Statistical analysis included color differences (∆E00) and translucency parameter differences (∆TP00), considering CIEDE2000 and acceptability (AT) and perceptibility thresholds (PT). Surface roughness was evaluated through Ra and Rz parameters. MOLD showed the most significant color alteration, particularly after red wine, indicating higher susceptibility to staining (p< 0.05). In contrast, SUB demonstrated superior color stability, while PRINT exhibited similar behavior to SUB and PRESS (p> 0.05), with potential for further improvements. In conclusion, processing techniques significantly affected the optical stability of acrylic resins. Manual application against a mold showed the most significant color change, especially with red wine, while the subtractive method achieved the best stability. 3D printing performed similarly to subtractive and pressing techniques, but still requires structural improvements. Smoother surfaces, as in pressing, enhanced resistance to staining, whereas rougher surfaces, as in manual application, increased susceptibility.