Effect of 3D printing settings on the mechanical properties and biocompatibility of polymeric materials used for 3D direct printing of orthodontic aligners

The advent of the biocompatible resin Tera Harz TC-85 DAC (TC-85) introduces the potential for direct 3Dprinted aligners via vat-polymerization, where photosensitive liquids are hardened layer by layer using a light source. This study investigates the influence of tunable printing parameters on the mechanical and biocompatibility properties of the resulting materials. Specimens were fabricated using two different printers with varying Z resolutions (50 mu m and 100 mu m), output thicknesses (2 mm, 1 mm, and 0.5 mm), and feeding resins (TC-85 and Clear A). Mechanical properties were evaluated through tensile and bending tests, and the results demonstrate that printer selection significantly affects mechanical properties such as ductility and rigidity. In contrast, variations in Z resolution did not exhibit a significant impact. Material choice was identified as a critical factor, significantly influencing the elastic modulus (1131 vs 2088 MPa for TC-85 and Clear A resins, respectively), ultimate tensile strength (23 vs 41 MPa), and elongation at break (66 % vs 16 %), thereby affecting the overall mechanical behavior of the samples. Biological assays did not evidence impairment of cell viability or proliferative capacities for the used cell lines in any applied experimental condition. Overall, this study underscores the role of printer type and material selection in optimizing the performance of direct 3D-printed aligners, highlighting key factors for future advancements in the field of dental materials and additive manufacturing technologies.