Abstract Background Clear thermoplastic orthodontic aligners are widely used due to their aesthetic appeal and patient comfort; however, exposure to chemically diverse intraoral environments may compromise their physical, aesthetic, and chemical stability. This study aimed to evaluate the effect of acidic, alkaline, and neutral chemical environments on weight variation, pH interaction, colour stability, and leaching behaviour of thermoplastic orthodontic aligner materials. Methods Thirty maxillary thermoplastic orthodontic aligners representing three commercial materials (Erkodur, Duran, and Zendura) were immersed in acidic (lime juice), alkaline (ENO ® solution), or neutral (artificial saliva) media for 14 days at 37 °C. Assessments were performed at Day 0, Day 7, and Day 14. Weight changes, pH variation, colour stability (ΔE, CIE L a b* using ImageJ and VITA Easyshade), and leaching behaviour (UV-Visible spectrophotometry) were analysed using repeated-measures and one-way ANOVA. Results Aligners in acidic media exhibited the greatest weight reduction (3.410 ± 0.015 g to 3.358 ± 0.025 g; p < 0.001), followed by alkaline media. Colour change was highest in acidic conditions (ΔE = 3.08 ± 0.15), moderate in alkaline (1.92 ± 0.12), and minimal in neutral media (0.77 ± 0.08). Leaching absorbance was significantly higher in acidic media at Day 14 (0.083 ± 0.004 AU; p < 0.001). Conclusion Oral chemical exposures significantly compromise the physicochemical and aesthetic properties of thermoplastic aligners, highlighting the need for careful material selection, patient guidance, and further in vivo studies to confirm clinical impact.
Ahuja et al. (Fri,) studied this question.