Shape Recovery Characteristics of Orthodontic Aligners Fabricated from Shape Memory Polymers: A Typodont Investigation

This study investigated the use of shape memory polymers (SMPs) as a next-generation material for orthodontic aligners to overcome the stepwise limitations of traditional aligner therapy. The ability of SMPs to return to a predefined shape and drive tooth movement under external stimuli was evaluated using a typodont model prior to clinical testing. The experimental setup aimed to achieve a 1.9 mm correction of an upper central incisor through a single aligner subjected to multiple activation phases. A custom typodont with a movable central incisor was digitally scanned, and corresponding resin models were produced via orthodontic software and 3D printing. Seven ClearX SMP aligners were thermoformed over the aligned resin models and sequentially tested for their repositioning effect on the incisor. After each activation step, scans of the model were superimposed to quantify the movement. The overall correction achieved by the SMP aligners was approximately 93% (1.76 mm), with individual contributions of 0.94 ± 0.04 mm from the reforming step, 0.66 ± 0.07 mm after the first activation, and 0.15 ± 0.10 mm following the second activation. These results indicate that SMP-based aligners may offer a viable and effective approach for aesthetic orthodontic treatment in the future.