Mechanical and Viscoelastic Properties of a Temperature-Responsive Photocurable Resin for 3D Printed Orthodontic Clear Aligners

Abstract This study presents a novel technique for the direct 3D printing of TC-85, a biocompatible material specifically designed for orthodontic uses. This method aims to overcome the biomechanical constraints associated with the conventional thermoforming process used in aligner fabrication. The investigation emphasizes analyzing TC-85's mechanical and viscoelastic properties, focusing on how temperature changes impact these characteristics and their relevance to clinical outcomes. Using a Digital Light Processing (DLP) 3D printer, the photoreactive resin TC-85 is printed, and extensive thermo-mechanical testing is conducted, which includes evaluations of tensile modulus, stress relaxation, and creep behavior. Dynamic Mechanical Analysis (DMA) is conducted at temperatures varying from 30 to 45°C to assess the material's adaptive response to thermal fluctuations. TC-85 is distinguished by its unique mechanical properties, which include a temperature-sensitive stiffness, stress relaxation capability, and shape memory feature. The results demonstrate that TC-85 maintains an enhanced level of residual force and a faster recovery of strain through numerous cycles of loading and unloading. At 40°C, TC-85 displays a substantial reduction in its storage modulus, while maintaining consistent strain recovery and volumetric constancy. The study highlights TC-85's potential in orthodontic treatments, providing adaptable mechanical and viscoelastic properties that enable the exertion of consistent, regulated forces on teeth. Its resistance to force decay, stable volume at raised temperatures, and built-in shape memory enhance hygienic upkeep and patient comfort, positioning TC-85 as a pioneering material for the next generation of clear aligners.