A Denture Base Resin Developed Using Hyperbranched Polyurethane Acrylate, Tricyclodecane Dimethanol Diacrylate, and Liquid Crystal Display-Based Three-Dimensional Printing

Poly-(methyl methacrylate) (PMMA) is the most widely used denture base material. However, because of PMMA's insufficient mechanical strength, fracture is a frequent problem after long-term denture use for chewing. In this study, hyperbranched polyurethane acrylate (HBPUA) was synthesized using trimethylolpropane, isophorone diisocyanate, and hydroxyethyl acrylate in a molar ratio of 1:3.1:3.2. Gel permeation chromatography revealed that the number- and weight-average weights of the synthesized HBPUA were approximately 1325 and 1797, respectively. For blended resins comprising different HBPUA and tricyclodecane dimethanol diacrylate (TCDDMDA) weight ratios, viscosity increased with increasing HBPUA content. A composition of 10 and 90 wt % HBPUA and TCDDMDA (TC10), respectively, was optimal for developing a denture base resin using liquid crystal display-based three-dimensional (3D) printing. Resins exposed to light for 5, 15, and 30 s and containing photoinitiator concentrations of 1 and 2 mol % were fabricated for comparison with a commercial resin, Denture 3D+. Attenuated total reflectance Fourier-transform infrared spectroscopy revealed that Denture 3D+ possessed a higher double bond conversion rate than those of the TC10 materials. Three-point bending tests revealed that Group 4 (TC10-0.01, 15 s) possessed the highest flexural strengths after both 50 h and 28 d of water immersion and that this group's flexural modulus also exceeded that of Denture 3D+, although the group's toughness and elongation were lower than those of Denture 3D+. In addition, the water sorption and solubility, surface roughness, and volumetric shrinkage of TC10 materials were lower than those of Denture 3D+. Furthermore, the impact strength, microhardness, and biocompatibility of Group 4 were comparable to those of Denture 3D+. These results indicate that Group 4 not only satisfied the ISO 20795-1 requirements but also possessed some properties superior to those of Denture 3D+, implying strong potential for practical application as a denture base material.