Evaluation of surface roughness, microhardness, and color change of 3D-printed resins post-polymerized with glycerin gel

OBJECTIVE: The aim of this study was to investigate the effects of post-polymerization protocols with and without glycerin on surface roughness, microhardness, and color change of permanent restorative resins fabricated using stereolithography (SLA) and digital light processing (DLP) technologies under different storage media. MATERIALS AND METHODS: In this in vitro study, a total of 128 permanent restorative resin specimens fabricated using SLA (Permanent Crown, Formlabs) and DLP (Crowntec, Saremco) technologies were evaluated. The specimens were divided into post-polymerization protocols with and without glycerin. Finishing and polishing procedures were performed using a standardized diamond polishing system. Surface roughness (Ra, Sa) was measured using a confocal microscope, microhardness was assessed by the Vickers hardness test (VHN), and color change was evaluated using the CIEDE2000 (ΔE₀₀) method. The specimens were stored in distilled water, tea, coffee, and cola, and measurements were repeated at baseline and after 7 and 30 days. RESULTS: No statistically significant difference in surface roughness was observed between post-polymerization protocols with and without glycerin. In contrast, specimens post-polymerized with glycerin exhibited significantly higher microhardness values for both fabrication techniques. With respect to color change, lower ΔE₀₀ values were observed in the glycerin-treated groups, particularly in the coffee storage medium. CONCLUSIONS: Post-polymerization with glycerin increased microhardness without adversely affecting surface roughness and supported color stability under specific staining storage media. CLINICAL RELEVANCE: In permanent restorative resins fabricated by 3D printing, post-polymerization with glycerin can be considered a complementary protocol that is easily applicable in clinical practice and may positively support the color stability and microhardness of restorations.