Color and Relative Translucency of Three-Dimensionally Printed Restorative Resin Systems: Effects of Build Orientation, Thickness and Staining Conditions

This study assessed the effects of material system, build orientation, thickness, and immersion time on optical properties. A total of 224 discs (n = 7 per subgroup) were fabricated from Permanent Crown Resin (system F) and Saremco Print CROWNTEC (system S) at 0° and 90° orientations and 1- and 2-mm thicknesses. Specimens were immersed in distilled water, coffee, tea, or red wine and measured at baseline and days 1, 7, and 30. Baseline CIELAB coordinates and changes in color (ΔE00) and relative translucency parameter (ΔRTP00) were analyzed by three-way and medium-specific four-factor mixed analyses of variance, respectively (α = 0.05). Material system dominated baseline variation (ηp2 = 0.70–0.94); system S was lighter with lower a* and b* values. Time affected ΔE00 in all media and ΔRTP00 in staining media (p < 0.001). All between-specimen factors affected both outcomes in staining media, with medium-specific interactions. Descriptively, red wine produced the greatest changes; all red-wine groups exceeded the color acceptability threshold at day 30. System F at 90° and 1 mm showed the largest changes (ΔE00 = 41.46 ± 9.48; ΔRTP00 = 5.57 ± 0.85). No 2-mm group exceeded the translucency acceptability threshold. Optical behavior depended on configuration and exposure. System S showed greater color stability, mainly at 0°, whereas 90° orientation and reduced thickness generally increased optical change. Material, printing and post-polymerization effects could not be separated.