Influence of monomer structure and mixing ratio on polymerization behavior and mechanical properties of dental 3D printing resins.

OBJECTIVES: To investigate how different combinations of base monomers, including diurethane dimethacrylate (DUDMA) and bisphenol A-glycidyl methacrylate (Bis-GMA), and diluent monomers, including trimethylolpropane trimethacrylate (TMPTMA) and triethylene glycol dimethacrylate (TEGDMA), as well as their mixing ratios, influence light attenuation behavior, degree of conversion (DC), mechanical properties, and cell viability in dental resins fabricated by layer-wise additive manufacturing. METHODS: Binary systems were formulated at 5:5 and 7:3 wt ratios. Their optical behavior was characterized using Jacob's working curve, while the degree of conversion (DC) was quantified via ATR-FTIR. Mechanical properties and biocompatibility were evaluated using three-point bending tests, Vickers hardness and CCK-8 assays with human gingival fibroblasts, respectively. RESULTS: All formulations exhibited linear working curve behavior. TEGDMA-containing systems showed significantly higher DC and flexural strength, whereas TMPTMA-containing systems demonstrated greater flexural modulus and Vickers hardness. Mixing ratio effects were system-dependent, with no direct correlation between curing behavior, DC, or mechanical properties. All formulations showed no cytotoxicity in human gingival fibroblasts. SIGNIFICANCE: This study provides a comprehensive understanding of how the interplay between base monomers (DUDMA, Bis-GMA) and diluents (TMPTMA, TEGDMA) dictates the performance of 3D-printed unfilled dental resins. By integrating Jacob's working curve analysis with mechanical and biological evaluations, we identified optimal formulations that balance high degree of conversion with clinical-level biocompatibility. These findings offer a precise chemical roadmap for developing next-generation additive manufacturing resins with tailored mechanical properties for restorative dentistry.