Effect of Different Polishing Systems on the Surface Roughness of 3D-Printed Resins

Background: This in vitro study evaluated the effect of different finishing and polishing systems on the surface roughness of two 3D-printed crown resins. Methods: Eighty disc-shaped specimens were produced from two 3D-printed crown resins, Saremco Print Crowntec and VarseoSmile Crown Plus. Specimens were divided into four groups according to the finishing and polishing protocol: Lucida, TwistDia, OptiShine, and OptiGlaze. Surface roughness (Ra) was measured before and after finishing and polishing using a non-contact optical profilometer. Data were analyzed using ART ANOVA (p < 0.05). Results: All polishing protocols significantly reduced surface roughness, with the overall median Ra decreasing from 0.198 µm before polishing to 0.101 µm after polishing (p < 0.001). Among the tested protocols, OptiGlaze showed the lowest post-polishing median Ra values for both resin materials, whereas Lucida showed the lowest overall median Ra value across measurement times. Resin type had no significant effect on Ra, whereas the polishing system significantly influenced surface roughness. Pairwise comparisons revealed significant differences between OptiGlaze and OptiShine, OptiGlaze and TwistDia, and Lucida and TwistDia (p < 0.05). All post-polishing Ra values remained below the clinically relevant threshold of 0.2 µm. Conclusions: The surface quality of the tested 3D-printed crown resins was determined primarily by the polishing protocol rather than the resin type. Although all protocols provided clinically acceptable surfaces, the optimal polishing approach may depend on the resin–polishing system combination.