Microplastic Particle Recovery from Orthodontic Appliances: An In Vitro Pilot Study Using Laser-Directed Infrared Spectroscopy

To quantify and characterize microplastic particles recovered from orthodontic appliances under simulated intraoral conditions using laser-directed infrared spectroscopy (LDIR), five maxillary orthodontic appliances were exposed to artificial saliva at 37 °C under calibrated agitation simulating nighttime (8 h) and full-time (20 h) wear over a 14-day period. A 1 mL aliquot retrieved from a 50 mL exposure volume was analyzed using LDIR to determine particle count, size, eccentricity, and polymer composition, with statistical analyses performed on an exploratory and polymer-stratified basis. Particle recovery ranged from 11–16 particles for nighttime appliances and increased substantially for aligners (SmartTrack: 341; Zendura: 1382). Multiple polymer types were identified, and no statistically significant differences in particle diameter or eccentricity were observed after multiplicity correction. These findings show that orthodontic appliances can generate recoverable microplastic particles under simulated conditions, establish a reproducible framework for automated microplastic characterization, and support future investigation into clinical exposure. Because the effective detection threshold of the LDIR workflow is approximately 20 µm, smaller microplastics and nanoplastics were not evaluated in this study.