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.
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