Long-term disinfection of 3D-printed denture resin: physical and biological in vitro assessments

This study evaluated the effects of prolonged overnight immersion in disinfectant solutions on the physical and biological properties of 3D-printed and heat-polymerized polymethyl methacrylate (PMMA) denture base materials. Four solutions were tested: distilled water (control), 1% sodium hypochlorite, 2% chlorhexidine digluconate, and a disinfectant soap (Lifebuoy (R)). Daily cycles of 8 h in disinfectant solutions and 16 h in distilled water were performed for up to 6 months to represent overnight disinfection and daily use. The evaluated parameters included color change, water contact angle, Vickers hardness, surface roughness and topography, residual antimicrobial activity against Candida albicans biofilm, and cytotoxicity in L-929 cells. Color change remained within clinically acceptable thresholds for all groups, with Lifebuoy (R) showing values comparable to the control. Water contact angles decreased after immersion, while surface roughness was stable up to 3 months and decreased at 6 months, particularly in PMMA. Hardness increased in heat-polymerized specimens, whereas 3D-printed materials showed greater stability over time. 3D-printed resins exhibited higher C. albicans biofilm formation than PMMA. Chlorhexidine digluconate resulted in the greatest reduction in fungal growth and metabolic activity, followed by sodium hypochlorite and Lifebuoy (R). Most groups showed no cytotoxic effects, except for moderate cytotoxicity of chlorhexidine at 3 months. In conclusion, 3D-printed resin showed superior physical performance, while PMMA demonstrated lower Candida colonization. Chlorhexidine was the most effective antibiofilm agent despite time-dependent cytotoxicity, while Lifebuoy (R) served as a non-cytotoxic alternative.