Roughness and Gloss of 3D-Printed Crowns Following Polishing or Varnish Application

The aim of this study was to evaluate and compare the surface roughness and gloss-both initially and after simulated toothbrushing-of three 3D-printed crown materials subjected to different surface treatments: varnishing, polishing with diamond-impregnated rubber polishers, and polishing with a bristle brush and paste. Disc-shaped specimens (n = 90) were 3D-printed using three commercially available crown resins (Rodin Sculpture, VarseoSmile TriniQ, and OnX Tough 2) and post-processed per manufacturers' instructions. Specimens were divided into three surface treatment groups: application of a light-cured varnish, polishing with a two-step diamond-impregnated rubber polisher, or polishing with a bristle brush and abrasive paste. Surface roughness and gloss were measured after treatment and again following 20,000 cycles of simulated toothbrushing. Additional specimens were prepared for Vickers microhardness testing and determination of filler weight percentage (wt%). Statistical comparisons were performed using two-way ANOVA with significance set at p < 0.05. Results: The varnish provided the statistically lowest roughness of all surface treatments for all materials. The bristle brush and abrasive paste polishing protocol produced the greatest gloss for the softest material (VarseoSmile TriniQ) and lowest gloss for the hardest material (Rodin Sculpture), whereas the two-step diamond-impregnated rubber polisher produced an equivalent gloss on all materials. Following toothbrushing, roughness was minimally affected; however, gloss was considerably reduced. Conclusions: All tested polishing and varnishing methods achieved clinically acceptable surface roughness (Ra < 0.2 µm) that persisted after simulated toothbrushing. Notably, the two-step diamond-impregnated rubber polisher produced consistent gloss across all materials, while the bristle brush and abrasive paste polishing protocol performed better on softer materials, and varnish application resulted in equal or superior gloss and roughness retention compared to polishing.