Gloss and Surface Roughness of Stained and Polished 3D-Printed Resins Used for the Fabrication of Hybrid Denture Prosthesis: An In Vitro Study

Despite the increasing use of additively manufactured restorative materials, comparative information regarding their surface gloss and roughness after different surface treatments and simulated oral challenges remains limited. This study evaluated the gloss and surface roughness of stained and polished 3D-printed resins subjected to acidic storage followed by simulated tooth brushing. Two 3D-printed resins (ONX and Tough 2 [T2]) were compared with a milled material (Lava Ultimate [LU]), which was used as a control. A total of 120 specimens (40 per material) were fabricated, surface-treated (stained or polished), and randomly categorized into acid or water storage/tooth brushing. A gloss meter and non-contact profilometer were used to measure the gloss and surface roughness of the materials. Data analysis was performed using one-way ANOVA, Welch’s pairwise t-tests with Holm adjustment, and HC3-robust Type III factorial models, with significance set at α = 0.05. Gloss significantly decreased, whereas surface roughness (Ra) significantly increased after storage/brushing across the experimental groups (p < 0.05), except for T2 subjected to acid storage/brushing, which showed no significant change in Ra (p = 0.11). Both gloss and Ra were significantly affected by the material type (p < 0.001). For gloss, significant effects of material and surface treatment were observed (p < 0.001). For Ra, significant effects of material, surface treatment, and storage/brushing were detected (p < 0.001). Material type and surface treatment significantly influenced gloss, whereas storage/brushing effect had no significant effect. In contrast, material type, surface treatment, and storage/brushing significantly influenced surface roughness. The milled LU generally exhibited higher gloss and lower roughness than the 3D-printed ONX and T2 materials, particularly among stained specimens, while ONX generally showed more favorable surface properties than T2.