Siotou Kalliopi, Chountalas Theofanis, Katsavrias Athanasios, Siotos Charalampos, Mpalias Konstantinos, Semitekolos Dionysios, Charitidis Constantinos, Tsolakis Apostolos I
Department of Orthodontics, National and Kapodistrian University of Athens, Athens, Greece.
Department of Laboratory of Heterogeneous Mixtures & Combustion Systems, Mechanical Engineering School of the National Technical University of Athens, Athens, Greece.
Orthod Craniofac Res. 2025 Apr;28(2):253-260. doi: 10.1111/ocr.12867. Epub 2024 Oct 23.
Although the technique of orthodontic aligners has risen in popularity, their mechanical properties have not been thoroughly investigated. The aim of this study was to evaluate the mechanical properties of the orthodontic aligners Clear Aligner after intraoral use for 7, 10 and 14 days, and to compare them with as-received aligners (0 days). It was also sought to examine the properties of the unprocessed raw material (polyethylene glycol terephthalate) used to manufacture these aligners.
MATERIALS/METHODS: Thirty-two aligners by four patients were evaluated and studied at 0, 7, 10, 14 days of use. Each aligner was divided into three segments (two posterior and one anterior), which resulted in 96 samples. Also, 16 samples of unprocessed material were studied. For all samples, elastic modulus, ultimate tensile stress (UTS) and yield stress were calculated by conducting tensile testing. Additionally, material hardness was tested. The two-tailed Mann-Whitney test was performed, having set the level of significance at p = 0.05.
Analysis of the measurements indicated a statistically significant decrease in elastic modulus between days 0 and 14 of use, of UTS between days 0 and 7, 7 and 10, and of yield stress between days 0 and 7. For hardness, in every period, posterior segments demonstrated significantly higher values than anterior segments. All properties of the unprocessed material were statistically significantly higher than the processed samples.
The unprocessed material presented significant differences in every property tested in comparison to the processed aligners. The processed material showed further deterioration over time during use. The present study provides evidence that thermoforming and ageing affect the mechanical properties of the aligners.
尽管正畸矫治器技术越来越受欢迎，但其力学性能尚未得到充分研究。本研究的目的是评估正畸矫治器Clear Aligner在口腔内使用7、10和14天后的力学性能，并将其与刚收到时（0天）的矫治器进行比较。还试图研究用于制造这些矫治器的未加工原材料（聚对苯二甲酸乙二醇酯）的性能。
材料/方法：对4名患者的32个矫治器在使用0、7、10、14天时进行评估和研究。每个矫治器分为三个部分（两个后部和一个前部），共得到96个样本。此外，还研究了16个未加工材料的样本。对所有样本进行拉伸试验，计算弹性模量、极限拉伸应力（UTS）和屈服应力。此外，还测试了材料硬度。采用双尾曼-惠特尼检验，显著性水平设定为p = 0.05。
测量分析表明，使用第0天和第14天之间弹性模量有统计学显著下降，第0天和第7天、第7天和第10天之间UTS有下降，第0天和第7天之间屈服应力有下降。对于硬度，在每个时间段，后部段的值均显著高于前部段。未加工材料的所有性能在统计学上均显著高于加工后的样本。
与加工后的矫治器相比，未加工材料在每项测试性能上均存在显著差异。加工后的材料在使用过程中随时间进一步劣化。本研究提供了热成型和老化会影响矫治器力学性能的证据。
