Comparative Evaluation of Initial Horizontal and Occlusal Forces Generated by Orthodontic Aligners Fabricated with Different Materials

UNIQ (Scheu Dental GmbH, Hilden, Germany) is a recently introduced monolayer copolyester aligner material whose initial biomechanical behavior has not yet been compared with that of established multilayer aligner materials. This in vitro study compared the initial orthodontic forces generated by UNIQ and Zendura FLX during buccolingual and occlusogingival displacement of a maxillary central incisor. Aligners made from Zendura FLX 0.76 mm and UNIQ 0.625 mm were thermoformed over identical 3D-printed maxillary arch models and tested with the Orthodontic Simulator (OSIM) at the Craniofacial Biomechanics and Biomaterials Research Group, University of Alberta. Displacements were applied in 0.05 mm increments up to 2 mm, with repeated load-cell measurements performed at each step. Both materials showed progressive force increases with displacement. Zendura FLX generated slightly higher buccolingual forces at most displacement levels, but the differences were not statistically significant; occlusogingival forces were similar across most displacement levels, although a larger between-material difference was observed at 2 mm of displacement. Within the limitations of this in vitro model, no statistically significant differences in overall force–displacement response were detected between UNIQ and Zendura FLX under the experimental conditions evaluated. These findings support further investigation of this monolayer material under additional laboratory and clinical conditions.