Thermo-mechanical properties of 3D printed photocurable shape memory resin for clear aligners
Se Yeon Lee, Hoon Kim, Hyun‐Joong Kim, Chooryung J. Chung, Yoon Jeong Choi, Su-Jung Kim et al. · 2022 · 155 citationsRead the paper
To overcome the limitations of the conventional vacuum thermoforming manufacturing method, direct 3D printing of clear aligners has been developed. The present study investigated the thermo-mechanical and viscoelastic properties of a photocurable resin TC-85, which is a new material for the direct 3D printed clear aligners, comparing to a conventional thermoplastic material polyethylene terephthalate glycol. Dynamic mechanical analysis was performed to analyse the mechanical behaviours of the two materials at 37 °C and 80 °C, respectively. Furthermore, the shape memory property of the two materials was evaluated using a U-shape bending test, and the shape recovery ratio for 60 min at 37 °C was calculated. The results indicate that TC-85 can constantly apply a light force to the teeth when used for the 3D printed clear aligners, owing to its flexibility and viscoelastic properties. In addition, it is expected that the force decay induced by repeated insertion of the clear aligners will be reduced and a constant orthodontic force will be maintained. Furthermore, its geometric stability at high temperatures and the shape memory properties provide advantages for the clinical application.
What the full text shows
Working prototype- TC-85 exhibits shape memory recovery at 37 °C after being deformed at 80 °C. — 96% recovery ratio after 60 min (Bent at 80 °C, cooled to 24 °C, then immersed in 37 °C water bath)
- TC-85 has a lower glass transition temperature (Tg) than PETG. — 69.45 °C vs 101.8 °C (DMA temperature sweep)
- TC-85 shows a more viscous response at oral temperature than PETG. — Loss tangent of 0.16 vs 0.004 (At 37 °C)
- TC-85 has lower yield stress and stiffness compared to PETG. — Yield stress: 32.31 MPa vs 44.20 MPa; Elastic modulus: 1186.40 MPa vs 1479.54 MPa (Static tensile test at 25 °C)
- TC-85 demonstrates significant stress relaxation at 37 °C, reducing initial force. — 18 N reduced to 1.0 N (1% elongation at 37 °C)
- 3D printing TC-85 results in overbuilding compared to the set design thickness. — 0.56 mm actual vs 0.5 mm set (12% increase) (DLP-type 3D printer with 100 μm layer thickness)
- Setup
- DLP-type 3D printer (Uniz 4K) for TC-85; vacuum thermoforming (Ministar S) for PETG on standardized maxillary incisor models.
- How
- The study compared a 3D printed photocurable resin (TC-85) with vacuum-thermoformed PETG using static tensile tests, Dynamic Mechanical Analysis (DMA), and U-shape bending tests for shape memory. TC-85 was printed via DLP, post-cured under N2 with UV light, and tested for stress relaxation and creep at 37 °C and 80 °C.
- Limitations
- Overbuilding in DLP printing (12% thickness increase) can prevent full seating on teeth. · SLA printing is suggested for higher accuracy but is too slow for clinical multi-stage production. · The study used a standardized model rather than diverse patient-specific anatomical structures.
Summarized by Gemma 4 from the open-access full text · 3 Oct 2026. Read it