Comparative evaluation of polishing protocols on the surface roughness of additively manufactured resin

Abstract

Aim: To compare the effect of different chairside polishing protocols on the surface roughness of a permanent crown resin fabricated by additive manufacturing. Materials and Methods: Seventy-five square specimens (10 × 10 × 2 mm) were 3D-printed in Saremco print CROWNTEC (A2) using a Masked Stereolithography (MSLA) printer (Phrozen Sonic Mini 4K). After standardized post-processing, specimens were randomly allocated to five polishing groups (n = 15): (a) Eve Diacomp paste polishing paste; (b) Sof-Lex XT polishing discs; (c) Universal polishing paste; (d) Intensive Unigloss paste; and (e) Intensive Unigloss polisher. Protocols were performed per manufacturers recommendations, with a handpiece at 5,000-7,000 rpm, bilateral 15 s, without pressure. Surface roughness (Ra) was measured using a contact profilometer. Representative surfaces were qualitatively imaged with field-emission scanning electron microscopy (FE-SEM). Data were analyzed in SPSS v23. Normality was assessed by Shapiro-Wilk; between group differences in non-normal data were tested with Kruskal-Wallis and Dunn multiple comparisons (α = 0.05). Results: Median Ra differed significantly among polishing protocols (H = 21.86, p < 0.001). The Eve Diacomp paste polishing paste yielded the lowest median Ra (0.310 µm), while the Sof-Lex XT disc group showed the highest (0.840 µm). Post-hoc comparisons indicated Eve paste produced significantly smoother surfaces than each of the other four systems; the other four did not significantly differ from one another. FE-SEM images corroborated profilometric findings, with Eve-polished surfaces displaying more homogenized topography and fewer directional grooves. Conclusions: A one-step diamond polishing paste achieved lower surface roughness than multi-step discs and the tested rubberized polishing alternatives. Given the outcome of smoother finishes and procedural simplicity, one-step diamond polishing pastes may be preferred for rapid finishing of printed resin restorations.