3D Printing of Block Copolymer-Based Fracture Tough Denture Base Materials

The development of 3D printing high-impact denture bases is challenging, as materials exhibiting both high flexural strength/modulus and fracture toughness are required. Nowadays, most of the commercially available 3D printing denture bases contain significant amounts of crosslinking monomers and therefore behave as brittle materials. In this contribution, urethane dimethacrylate DMA1/(octahydro-4,7-methano-1H-indenyl)methyl acrylate (OMIMA) 1/1 (wt/wt) formulations containing a poly(ε-caprolactone)-polydimethylsiloxane-poly(ε-caprolactone) (PCL-PDMS-PCL) triblock copolymer (BCP1) and fumed silica SiO₂-NPs were evaluated for DLP 3D printing of fracture-tough denture bases. The post-curing step was performed at various temperatures (RT, 60 °C, 80 °C, 100 °C and 120 °C). This parameter was shown to strongly influence the T_g and mechanical properties of 3D printed materials. A post-curing temperature of 100 °C was found to be ideal. Under these conditions, 3D printed materials exhibiting excellent mechanical properties were successfully obtained. Furthermore, the amounts of BCP1 and SiO₂-NPs were varied. The formulation containing 8.0 wt% of BCP1 and 10.0 wt% of SiO₂-NPs (FS = 67.5 ± 1.3 MPa, FM = 2450 ± 71 MPa, K_max = 2.11 ± 0.06 MPa m^1/2, W_f = 1109 ± 19 J m^-2) was able to fulfill the ISO 20795-1:2013 requirements in terms of flexural strength (FS)/modulus (FM) and fracture toughness for denture bases with improved impact resistance (FS > 65 MPa, FM > 2000 MPa, K_max > 1.9 MPa m^1/2, W_f > 900 J m^-2). This material showed better performance than the commercially available formulations Printodent^® GR-14.2 denture HI (FS = 69.2 ± 1.8 MPa, FM = 2153 ± 76 MPa, K_max = 0.82 ± 0.04 MPa m^1/2, W_f = 79 ± 10 J m^-2) and Lucitone Digital Print^TM 3D denture base (FS = 56.7 ± 1.9 MPa, FM = 2144 ± 12 MPa, K_max = 1.92 ± 0.09 MPa m^1/2, W_f = 1272 ± 177 J m^-2).