Comparative Evaluation of Polishing Protocols on the Surface Roughness and Gloss of Additively Manufactured Permanent Resins

Abstract

Objective:This in vitro study aims to evaluate the effect of different polishing protocols on the surface roughness and gloss of two additively manufactured permanent resin materials used for definitive restorations.Materials and Method: Sixty disk-shaped specimens (12 × 2 mm) were fabricated from two 3D-printed permanent resins, Bego VarseoSmile Crown Plus and Saremco CrownTec, and post-cured using a xenon flash light-curing unit. Each material was divided into three subgroups (n = 10): (1) unpolished control; (2) Diaprint 3D Twist multi-step rubber polishers; and (3) OptiDisc aluminum oxide discs. The surface roughness (Ra, µm) was measured with a contact profilometer, and the gloss (GU) was recorded with a glossmeter at 20°, 60°, and 85° incident angles, according to ISO 2813. The data were analyzed using a two-way ANOVA and Tukey’s post hoc test (α = 0.05).Results:The polishing protocol significantly influenced the surface roughness (p < 0.001), whereas the material type did not (p > 0.05). The Diaprint 3D Twist system produced the smoothest surfaces (Ra = 0.22 ± 0.04 µm), which were significantly lower than those achieved with OptiDisc or the control group (p < 0.05). Both the polishing protocol (p = 0.001) and the material type (p < 0.001) significantly affected the gloss. The highest gloss was observed in the Saremco-Diaprint 3D Twist group (79.0 ± 4.6 GU). No significant interaction was found between the factors.Conclusion:The choice of polishing protocol plays a critical role in optimizing the surface quality of the 3D-printed permanent resins. The Diaprint 3D Twist multi-step rubber system provided the smoothest and most glossy surfaces for both materials, achieving roughness values below the clinical threshold for bacterial adhesion. Saremco CrownTec exhibited a higher gloss than Bego VarseoSmile Crown Plus, which was likely due to its filler characteristics.