Clear aligners have transformed orthodontic care by providing an aesthetic, removable alternative to traditional braces. However, their significant environmental footprint, contributing to approximately 15,000 tons of plastic waste annually, poses a critical challenge. To address this issue, advancements in 4D printing have introduced “smart” aligners with shape memory properties, enabling reshaping and reducing the number of aligners required per treatment. This study focuses on ClearX aligners, an innovative 4D-printed solution aimed at extending usage duration and minimizing environmental impact. Using a comprehensive suite of tests, including morphological, optical, and mechanical evaluations conducted via scanning electron microscopy, UV-Vis spectroscopy, infrared spectroscopy, and bending and strain assessments, we evaluated the optical and mechanical stability of the ClearX material before and after thermal activation. Our results demonstrate that ClearX aligners retain their structural and functional properties after reshaping. Temporary changes in transparency, observed only under prolonged treatment durations exceeding manufacturer recommendations, are fully reversible within 12 h and do not compromise the aligner’s usability. These findings support the potential of ClearX aligners to effectively combine patient-centered, high-quality orthodontic care with sustainable practices.

Background: Relationships between reflectivity, hardness and chemical composition of the dispersed phase, included in orthodontic composites Transbond XT^TM (Trans), Light-Cure Orthodontic Paste (Leone) and Bisco Ortho Bracket Paste LC (Bisco), were investigated in vitro to evaluate whether reflectivity results can be useful in internal material composition interpretation, thus obtaining information on mechanical behaviours. Methods: Light transmission through 36 resin discs was measured with a UV/Vis spectrophotometer, evaluating the spectral range from 190–1100 nm. To have a benchmark of material hardness and internal composition, Vickers measurements and Cross-Sectional Focus Ion Beam Scanning Electron Microscopy (FIB/SEM) analysis were provided. Results: Bisco has the highest reflectivity, Leone shows an absorption pattern in the UV region similar to Bisco and Transbond has the lowest reflectivity compared to the others. This trend is confirmed by FIB/SEM imaging, showing a more similar induced roughness and internal composition for Bisco and Leone, with respect to Transbond. Higher filler presence in the composition of Bisco and Leone justifies a higher hardness of these two materials, with respect to Transbond, as confirmed by Vickers measurements. Conclusions: Bisco and Leone show similar optical responses and similarities in mechanical performance. This statement is explained by the lower and similar filler content as confirmed also by FIB/SEM analysis. The inner composition of Bisco and Leone provides a higher value of microhardness, as demonstrated by Vickers measurements. Therefore, this study confirms that the UV-Vis analysis can also offer a significant overview on the internal material composition, thus indirectly providing information on the mechanical properties of orthodontic composites.