Effect of Thermomechanical Aging on Force System of 3D-Printed Orthodontic Aligners
Description
This study investigated the effect of thermomechanical aging on force generation by 3D-printed Tera Harz TC-85 and thermoformed Zendura FLX (ZF) aligners and evaluated the thickness homogeneity of both systems. Ten aligners were fabricated from each material and subjected to thermomechanical aging for up to 30 days. Forces delivered to the maxillary right central incisor (Tooth 11) were assessed at baseline and after 2, 7, and 30 days using Fuji pressure-sensitive films to quantify normal contact forces and an orthodontic measurement and simulation system (OMSS) to determine resultant three-dimensional forces. Aligner thickness was measured using a digital caliper and micro-computed tomography (µCT). TC-85 aligners generated significantly greater initial contact forces than ZF aligners (149.7 ± 25.6 N vs. 69.8 ± 9.0 N). Both materials exhibited significant force degradation following aging. OMSS analysis demonstrated comparable baseline resultant forces between groups (0.1–0.5 N), with no significant differences in facial force components. While facial forces remained relatively stable throughout the aging period, lingual resultant forces decreased significantly over time. Thickness analysis revealed marked thinning in ZF aligners (0.5 ± 0.05 mm) and localized thickening in TC-85 aligners (1.0 ± 0.09 mm). Within the limitations of this in vitro study, TC-85 aligners produced higher initial contact forces; however, both materials showed significant force decay over time, potentially affecting the predictability of orthodontic tooth movement.