Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany.
Oral Technology Department, Dental School, University Hospital Bonn, Bonn, Germany.
J Mech Behav Biomed Mater. 2023 Jul;143:105911. doi: 10.1016/j.jmbbm.2023.105911. Epub 2023 May 15.
The aim of the study is to investigate the effects of artificial aging by thermocycling and mechanical loading on force/torque delivery by thermoplastic orthodontic aligners. Ten thermoformed aligners, made of Zendura™ thermoplastic polyurethane sheets, were aged over two weeks in deionized water by thermocycling alone (n = 5) and by both thermocycling and mechanical loading (n = 5). The force/torque generated on upper second premolar (Tooth 25) of a plastic model was measured before aging (as control), and after 2, 4, 6, 10, and 14 days of aging, using a biomechanical set-up. Before aging, the extrusion-intrusion forces were in the range of 2.4-3.0 N, the oro-vestibular forces were 1.8-2.0 N, and the torques on mesio-distal rotation were 13.6-40.0 Nmm. Pure thermocycling had no significant effect on the force decay of the aligners. However, there was a significant decrease in force/torque after 2 days of aging for both thermocycling and mechanical loading aging group, which is no longer significant over 14 days of aging. In conclusion, artificial aging of aligners in deionized water with both thermocycling and mechanical loading results in a significant decrease in force/torque generation. However, mechanical loading of aligners has a greater impact than pure thermocycling.
本研究旨在探讨热循环和机械加载对热塑性正畸保持器的力/扭矩传递的人工老化影响。10 个热成型的保持器由 Zendura™热塑性聚氨酯片制成，在去离子水中通过单独的热循环（n=5）和热循环和机械加载（n=5）进行为期两周的老化。使用生物力学设置在上颌第二前磨牙（牙 25）上测量老化前（作为对照）和老化后 2、4、6、10 和 14 天的力/扭矩。老化前，挤出-侵入力在 2.4-3.0 N 范围内，近远中旋转的扭矩在 13.6-40.0 Nmm。纯热循环对保持器的力衰减没有显著影响。然而，在热循环和机械加载老化组中，老化 2 天后力/扭矩显著下降，超过 14 天后不再显著。综上所述，在去离子水中对保持器进行热循环和机械加载的人工老化会导致力/扭矩产生显著下降。然而，机械加载对保持器的影响大于纯热循环。
