Ionic Liquid-Based 3D Printed Resin Suppresses Bacterial and Candida Infections

Objectives: This study aimed to evaluate the antibacterial and antifungal properties of ionic liquids and assess their mechanical performance when incorporated into 3D-printed resin materials intended for dentures.
Methods: Five ionic liquids were tested for antibacterial and antifungal activity against Streptococcus mutans (UA159) and Candida albicans (SC5314) using Minimum Inhibitory Concentration (MIC), Minimum Bactericidal/Fungicidal Concentration (MBC/MFC), and Disc Diffusion assays. The ionic liquids tested were: 1)1-Octyl-3-methylimidazolium tetrafluoroborate (OMIT), 2) 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIT), 3)Trioctylmethylphosphonium docusate (TMPD), 4)1-Ethyl-3-methylimidazolium acrylate (EMIA), and 5) 1-Ethyl-3-methylimidazolium vinyl acetate (EMIV). Among the five ionic liquids tested in this study, two are particularly suitable for polymerization with dental resins. Next, EMIA and EMIV were incorporated into 3D-printed resins at 0%, 2.5%, 5%, 7.5%, 10%, and 15% concentrations. The mechanical properties of these resins were evaluated using Degree of conversion percentage (DC%) and flexural strength tests, and statistical analysis was performed using two-way ANOVA with α= 5%.
Results: MIC tests showed that TMPD had the lowest MIC against Candida albicans (3.53 µg/mL) and Streptococcus mutans (1 µg/mL). EMIA also demonstrated strong inhibition against Streptococcus mutans (MIC: 5.1 µg/mL). Disc diffusion assays revealed that EMIA produced the largest inhibition zone for Streptococcus mutans (41.38 mm), while the control group had the largest zone for Candida albicans (22.01 mm). Degree of conversion (DC) tests showed EMIA peaked at 7.5% (62.11%) and EMIV at 5% (61.46%), with both decreasing at higher concentrations. Flexural strength testing indicated that EMIA reached its maximum strength at 10% (159.75 MPa) and EMIV at 5% (144.72 MPa), followed by declines in strength at higher concentrations.
Conclusions: Ionic liquid-based 3D-printed resins are promising for antimicrobial and antifungal applications while maintaining strong mechanical properties. EMIA showed superior mechanical strength and antibacterial activity, making it a suitable candidate for dentures that require both antimicrobial effectiveness and structural stability.