Mechanical and Time-Dependent Stability of K18-IBOA-Modified 3D-Printed Denture Base Resins

The incorporation of antimicrobial additives into 3D-printed denture base resins is a promising strategy for reducing denture stomatitis, but the mechanical consequences and temporal stability of such modifications remain poorly characterized. This in vitro pilot study evaluated the effects of incorporating 4% (w/w) K18-a quaternary ammonium methacryloxy silane dissolved in isobornyl acrylate (IBOA)-into three commercially available photopolymer resins printed across four platforms representing stereolithography, digital light processing, and liquid crystal display technologies. Flexural strength, flexural modulus, and flexure at break were measured at three time points: without K18, immediately after mixing, and one-week post-mixing. K18-IBOA incorporation produced significant reductions in all mechanical parameters across most resin-printer combinations. The magnitude and direction of changes were strongly dependent on printer-resin combination interactions, precluding generalization across systems. At one week, visible clumping consistent with phase separation was observed in all formulations, and one resin-printer combination exhibited catastrophic structural failure upon removal from the build platform. These findings suggest that 4% w/w K18-IBOA additions are unlikely to yield clinically acceptable denture bases without further formulation optimization, underscoring the importance of temporal stability assessment in the development of antimicrobial-modified photopolymer resins.