Evaluating Microplastic and Nanoplastic emissions from orthodontic clear aligners: a study on 3D Printed vs. Thermoformed devices

The introduction of clear aligners transforms orthodontic treatments, offering a less conspicuous alternative to traditional metal braces. Among them, directly printed aligners use advanced 3D printing technology to customize devices with biocompatible resins. Despite their advantages, concerns regarding the potential release of micro (MPs) and nanoplastics (NPs) in oral conditions are increasing, posing unanswered questions about their short- or long-term human safety implications. Based on this, the aim of this study is to examine and compare the release and dispersion of plastic particles from traditional thermoformed aligners (TFA) and 3D printed clear aligners (DPA) under simulated oral conditions, such as chemical interactions with simulated saliva pH and simulated chewing. Using a combination of imaging techniques, including optical microscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM), NPs and MPs were classified and quantified based on their size: microplastics (> 10 μm), sub-microplastics (from 40 nm to 10 μm) and nanoplastics (<40 nm). The results obtained indicate significant differences in the size and distribution of microplastic particles between the types of aligners. The mass of MPs and NPs separated after rubbing was 0.001g/200μl and 0.004g/200μl for TFA and DPA samples, respectively. In particular, TEM analysis demonstrated that DPA samples had larger and more numerous particles (203.08±2651.65mm2) compared to TFA (0.23±27.53mm2) and AFM analysis indicated a bigger root mean square gran size for DPA (159.89±350.72nm) than TFA (5.48±1.88nm).This variations highlight the influence of manufacturing techniques and material choices on the release of micro and/or nano particles, suggesting areas of potential improvement in the manufacturing processes of 3D printed aligners. This preliminary study focused only on particle production, without addressing potential biological effects. Therefore, further research is needed to deepen the implications of exposure to micro- and nanoplastics on human health to optimize new orthodontic technologies and ensure safety and effectiveness. References 1) Panayi, NC.; Efstathiou, S.; Christopoulou, I.; Kotantoula, G.; Tsolakis, IA. Digital orthodontics: Present and future. AJO-DO Clinical Companion. 2024;4(1):14-25. 2) Tartaglia, G.M.; Mapelli, A.; Maspero, C.; Santaniello, T. Serafin, M.; Farronato, M. et al. Direct 3D Printing of Clear Orthodontic Aligners: Current State and Future Possibilities. Materials (Basel). 2021;14(7). 3) Wulff, J.;Schweikl, H.; Rosentritt, M. Cytotoxicity of printed resin-based splint materials. J Dent. 2022;120:104097 4) Fang, C.; Awoyemi, O.S.; Luo, Y.; Naidu, R. Investigating Microplastics and Nanoplastics Released from a Rubber Band Used for Orthodontic Treatment with Improved Raman Imaging Algorithms. Environment & Health. 2023;1(1):63-71.