Evaluation of Bis-GMA/UDMA/TEGDMA Resin Systems for 3D-Printed Clear Orthodontic Aligners

This study developed a photosensitive resin system for 3D-printed clear orthodontic aligners, using bisphenol A glycidyl dimethacrylate (Bis-GMA) and urethane dimethacrylate (UDMA) as primary monomers, triethylene glycol dimethacrylate (TEGDMA) as a diluent, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO-L) as the photoinitiator. The effects of Bis-GMA content (0–70 parts per hundred resin) on the resin’s rheological properties, dimensional stability and mechanical performance were systematically investigated. Results showed that increasing Bis-GMA content significantly increased viscosity (from 311 to 2858 mPa·s) and Shore D hardness (from 68.9 to 80.9), while reducing volumetric polymerization shrinkage (from 7.49% to 5.24%). The resin achieved optimal mechanical properties at 15 parts per hundred resin of Bis-GMA, with the maximum tensile strength and flexural strength at 52.1 MPa and 131.1 MPa, respectively. The results of water sorption (13.74–20.78 µg/mm³) and solubility (1.56–3.09 µg/mm³) met ISO 20795-2:2013 standards. 3D printing experiments demonstrated excellent formability, with dimensional accuracy (root mean square values: 0.2258–0.3652 mm) suitable for orthodontic applications. This resin system balances processability and performance, providing a promising material for 3D-printed clear aligners.