Cui Xinyu, Li Fengru, Jiang Jiuhui
Department of Orthodontics, Peking University School and Hospital of Stomatology, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, People's Republic of China.
National Center for Stomatology& National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices, No.22, Zhongguancun South Avenue, Haidian District, Beijing, 100081, People's Republic of China.
Head Face Med. 2025 Mar 31;21(1):23. doi: 10.1186/s13005-025-00497-7.
Thermoplastic aligner materials are made from copolymers, and in the oral environment, their mechanical properties change over time. The effects of intraoral temperatures and the wet environments on the stress relaxation properties of these materials remain poorly understood. The aim of this study is to investigate the separate effects of the temperature and wet environment on the stress relaxation behavior of five available commercial orthodontic thermoplastic materials consisting of three chemical compositions.
A modified temperature-controlled water bath system was used to eliminate the confounding effect of water. The residual stresses of five commercial orthodontic thermoplastic materials with different chemical compositions (Biolon, Duran, and Erkodur (PETG), Essix ACE (copolyester), and Essix C + (PP/PE)) were examined at room temperature (22 °C), 37 °C, and 55 °C. After the materials were immersed in deionized water and artificial saliva for two weeks (37 °C), the 30 min stress relaxation curves of the five materials were measured.
Compared with those at room temperature (22 °C), the stress relaxation rates of the five materials increased and ranged from 0.7% to 18.11% at 37 °C and from 20.54% to 88.31% at 55 °C, and Ekodur and Essix ACEs exhibited relatively smaller increases. After two weeks of immersion in deionized water and artificial saliva, the stress relaxation rate of Essix ACE significantly decreased (p < 0.05), whereas that of the other four materials did not significantly change.
Elevated intraoral temperature accelerated the stress relaxation of thermoplastic aligner materials. The intraoral liquid immersion had no accelerating effect on the stress relaxation of any of the tested materials and even had a significant decelerating effect on that of Essix ACE.
热塑性矫治器材料由共聚物制成，在口腔环境中，其机械性能会随时间变化。口腔温度和潮湿环境对这些材料应力松弛性能的影响仍知之甚少。本研究旨在探讨温度和潮湿环境对五种市售正畸热塑性材料（由三种化学成分组成）应力松弛行为的单独影响。
使用改良的温控水浴系统消除水的混杂效应。在室温（22°C）、37°C和55°C下，检测了五种不同化学成分的市售正畸热塑性材料（Biolon、Duran和Erkodur（PETG）、Essix ACE（共聚酯）和Essix C +（PP/PE））的残余应力。将材料在去离子水和人工唾液中浸泡两周（37°C）后，测量了这五种材料的30分钟应力松弛曲线。
与室温（22°C）相比，五种材料的应力松弛率均有所增加，在37°C时为0.7%至18.11%，在55°C时为20.54%至88.31%，且Erkodur和Essix ACE的增加幅度相对较小。在去离子水和人工唾液中浸泡两周后，Essix ACE的应力松弛率显著降低（p < 0.05），而其他四种材料的应力松弛率没有显著变化。
口腔内温度升高加速了热塑性矫治器材料的应力松弛。口腔内液体浸泡对任何测试材料的应力松弛均无加速作用，甚至对Essix ACE有显著的减速作用。
