Denture-associated biofilms remain a significant cause of oral infections such as denture stomatitis. This study evaluated the antibiofilm efficacy of a newly developed silver-based antimicrobial denture material fabricated via stereolithography and compared its performance with that of three-dimensional printed (3DP) methacrylate dentures without an antimicrobial additive (Control). Rectangular test specimens (7.5 cm × 2.5 cm) were printed using stereolithography. The experimental denture material incorporated sodium silver zirconia hydrogen phosphate (SSZHP) as an antimicrobial additive (GL3D), while the control group comprised non-antimicrobial dentures. Both materials were tested in a mouth-simulated drip-flow biofilm reactor inoculated with pooled human saliva and enriched with clinically relevant oral microorganisms, including Candida albicans, Staphylococcus aureus, Streptococcus spp., methicillin-resistant S. aureus (MRSA), and vancomycin-resistant enterococci (VRE). The biofilm's growth and testing were carried out in accordance with a modified version of ASTM E2647-24 protocol. Microbial attachment was quantified on agar media by colony-forming unit (CFU) enumeration. Biofilm architectures were analyzed by confocal laser scanning microscopy (CLSM). Two-way ANOVA was performed using Minitab 2. The log CFU counts in GL3D were consistently lower than those in control (p < 0.05) across all microbial groups tested. CLSM analysis showed a 75.37% decrease in biofilm volume, a 49.02% reduction in mean biovolume, a 93.78% decrease in biomass, a 79.03% drop in substratum coverage, and a 92.37% decline in average thickness compared to controls. The incorporation of SSZHP into a 3D-printed denture material markedly reduced microbial viability and disrupted biofilm formation and structure. These findings demonstrate the potential of silver-based 3D-printed denture materials to improve oral health by minimizing biofilm-associated infections and enhancing the hygiene and longevity of prosthetic devices.