Impact of Common Cleaning Protocols on the Light Transmittance of Polyethylene Terephthalate Glycol (PET-G) Clear Aligners: An In Vitro Study

Background The optical clarity of clear aligners is essential for esthetics, and routine cleaning protocols may alter their light transmittance. This study evaluated the effect of commonly used cleaning methods on the light transmittance of polyethylene terephthalate glycol (PET-G) clear aligners in vitro. Materials and methods Forty PET-G specimens (10 × 10 mm) were divided into four groups (n = 10): Control, Listerine® rinse (Johnson & Johnson, Neuss, Germany), Corega® effervescent tablets (Stafford-Miller, Dungarvan, Ireland), and toothbrush with Colgate® toothpaste (Colgate-Palmolive, Guangzhou, China). The specimens were subjected to the assigned cleaning protocols once daily for 14 days. Light transmittance was measured using a UV-Vis-NIR (Ultraviolet-Visible-Near Infrared) spectrophotometer. Data were analyzed using the Shapiro-Wilk test, Levene’s test, Welch’s ANOVA, and Games-Howell post hoc comparisons at α = 0.05. Measurement reproducibility was assessed using repeated measurements and the intraclass correlation coefficient (ICC). Results Measurement reproducibility was excellent, with no significant systematic difference between repeated measurements (P = 0.515) and an ICC of 0.993. The highest mean light transmittance was observed in the Listerine group (87% ± 2%), followed by the control and Corega groups (85% ± 3% each), whereas the toothbrush group showed the lowest value (64% ± 6%). Levene’s test indicated unequal variances (P = 0.001), and Welch’s ANOVA showed a significant difference among groups (P < 0.001). Games-Howell post hoc analysis revealed that the toothbrush group had significantly lower transmittance than all other groups (P < 0.001), while no significant differences were found between the control, Corega, and Listerine groups. Conclusion Toothbrush-and-toothpaste cleaning markedly reduced the light transmittance of PET-G clear aligners, whereas chemical cleaning methods preserved optical properties. Non-abrasive cleaning approaches may be preferable for maintaining aligner transparency.