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. 2022 Apr 15;12(1):6246.
doi: 10.1038/s41598-022-09831-4.

Thermo-mechanical properties of 3D printed photocurable shape memory resin for clear aligners

Se Yeon Lee #  1 , Hoon Kim #  2   3 , Hyun-Joong Kim  2   4 , Chooryung J Chung  5 , Yoon Jeong Choi  6 , Su-Jung Kim  7 , Jung-Yul Cha  8
Affiliations

Thermo-mechanical properties of 3D printed photocurable shape memory resin for clear aligners

Se Yeon Lee et al. Sci Rep. .

Abstract

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.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Stress–strain curve of TC-85 and PETG; The small stress–strain curve is an enlargement of the initial range (dash line).
Figure 2
Figure 2
Stress relaxation and creep at 37 °C and 80 °C; The cycle of 1% elongation for 60 min and recovery for 60 min was repeated for13 cycles; (a) 37 °C, TC-85; (b) 37 °C, PETG; (c) 80 °C, TC-85; (d) 80 °C, PETG.
Figure 3
Figure 3
DMA temperature sweep; (a) storage and loss modulus of TC-85; (b) storage and loss modulus of PETG; (c) loss tangent of TC-85; (d) loss tangent of PETG.
Figure 4
Figure 4
Shape memory effect and shape recovery ratio over time of TC-85 (N = 6).
Figure 5
Figure 5
Shape memory property test procedure and shape memory mechanism; Yellow and blue specimens indicate TC-85 and PETG, respectively.
Figure 6
Figure 6
The preparing process and size of specimens; (a) Thermoplastic material (PETG); (b) 3D printed photocurable resin (TC-85); (c) size of specimens.
See this image and copyright information in PMC

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