The effectiveness of clear aligners in correcting malocclusions is closely linked to the properties of the materials used to make them. The polymers used in the manufacture of clear aligners have well-established properties. However, the process of manufacturing clear aligners, known as thermoforming, involves thermal and mechanical shocks that may alter these properties. The objective of this study was to evaluate the effects of thermoforming on the mechanical, optical, chemical, and morphological properties of sixty PET-G specimens. The study compared the thickness, weight, absorbance, chemical structure, surface roughness, elastic modulus, yield strength, and breaking load of thirty thermoformed specimens with thirty non-thermoformed specimens. The study introduces a new approach by using standardized samples to analyze both chemical and physical properties. The results showed statistically significant differences in thickness (−15%), weight (−11%), and surface roughness (+1233% in roughness average; +1129% in RMS roughness) of the material. Additionally, a correlation was found between reduction in thickness and increase in opalescence. There was no significant change in the functionality of the aligners after thermoforming, as no significant mechanical changes were found. However, the increase in surface roughness may lead to plaque and fluid accumulation and worsen the fit of the aligners.

Thermoplastic materials, such as glycol-modified polyethylene terephthalate (PET-G) and thermoplastic polyurethane (TPU), undergo alterations due to environmental factors in the oral cavity, which can affect their composition and surface properties over time. While previous studies have explored these changes, a comprehensive characterization of TPU and PET-G properties, particularly after immersion in artificial saliva, remains limited. This study aimed to evaluate the aging process of 24 TPU and 24 PET-G dumbbell-shaped specimens before and after exposure to artificial saliva. The analysis focused on the morphological, chemical, and optical properties of the samples, including thickness, weight, and surface roughness. The study examined 48 thermoplastic samples, equally divided between PET-G and TPU. The samples were thermoformed into standardized shapes and analyzed at three time points: after thermoforming (T0), after 7 days (T1), and after 14 days (T2) of immersion in artificial saliva at 37 °C. Measurements included weight, thickness, surface roughness, absorbance, and Fourier transform infrared spectroscopy (FTIR). Data were analyzed using one-way ANOVA to identify significant changes over time, with a significance level of p < 0.01. Both materials exhibited significant reductions in surface roughness, with TPU showing a decrease in average roughness (Ra) from 99.43 nm at T0 to 76.53 nm at T2 (-23.02%) and PET-G decreasing from 33.25 nm to 20.19 nm (-39.27%). The root mean square roughness (Rq) in TPU declined by 41.67% (from 126.91 nm to 74.02 nm), while PET-G showed a reduction of 28.06% (from 44.98 nm to 32.35 nm). Peak-to-valley roughness (Rt) also decreased by 10.5% in TPU and 27.96% in PET-G. No statistically significant changes were observed in thickness, weight, optical density, or chemical composition (p > 0.01). The roughness disparity between TPU and PET-G persisted even after immersion in saliva. Following the simulated intraoral aging process, significant changes in surface roughness were observed in TPU and PET-G specimens. The reduction in roughness, particularly a 39.27% decline in PET-G and 23.02% in TPU, has been clinically associated with decreased plaque accumulation and reduced friction between the aligner and the teeth.

Patient compliance remains a significant challenge in orthodontic treatment with clear aligners, as adherence to prescribed wear time is often suboptimal. This study investigated the potential of colorimetric analysis as a method to assess compliance with NOXI 3D-printed night-time aligners. Specifically, it evaluated color variations in polyamide aligners due to thermo-oxidation, using the RGB (Red, Green, Blue) color model as a non-invasive indicator. In total, 10 patients participated in this prospective study, wearing aligners for either 7 or 12 h daily over a 14-day period. Colorimetric measurements were collected via a smartphone-based application, and statistical analyses examined correlations between wear duration and color changes. The results revealed a significant association between a longer wear time and increased discoloration (p < 0.001), supporting the feasibility of RGB-based monitoring as a reliable compliance tool. However, individual variability in saliva composition, diet, and oral hygiene may have influenced the results, highlighting the need for further research into potential confounding variables. These findings underscore the promise of integrating digital monitoring technologies to improve adherence tracking and patient management in orthodontics. Future studies should refine the methodology and validate its efficacy in larger, more diverse populations.