Investigating Microplastics and Nanoplastics Released from a Rubber Band Used for Orthodontic Treatment with Improved Raman Imaging Algorithms.

Most teenagers experience orthodontic treatment, but we do not know the possible adverse effect of the released microplastics and nanoplastics that are recently categorized as emerging contaminants. Herein, we test the rubber band that has been employed to improve the biting of teeth during the orthodontic process to confirm the release of microplastics and nanoplastics. We improve the characterization of microplastics and nanoplastics by (i) Raman imaging, to extract and map the signal from the scanning spectrum matrix or the hyperspectral matrix and to enhance the signal-to-noise ratio statistically. To effectively extract the signal, (ii) chemometrics such as principal component analysis (PCA) are explored to convert the hyperspectral matrix to an image with an increased certainty. The nonsupervised PCA is intentionally corrected, via (iii) the algebra-based algorithm, to further increase the certainty to image the microplastics and nanoplastics. Once the signal is weak, (iv) an additional algorithm of image reconstruction via deconvolution is developed to average the background noise and smooth the image. By doing so, we estimate that millions of microplastics and nanoplastics are released daily in potential from a rubber band applied in a teenager's mouth, which might be a big concern. Overall, our approach provides a suitable option to characterize the microplastics and nanoplastics from a complex background.