Effect of cigarette smoke on the optical properties of clear orthodontic aligners: an in-vitro study

This study assessed the optical properties of aligner surfaces post-cigarette smoke exposure.

In-vitro experimental study.

Laboratory analysis of clear aligners subjected to cigarette smoke exposure at Federal University of Rio de Janeiro, Brazil.

A total of 20 plastic pieces from the labial surfaces of upper central incisors of Invisalign^® clear aligners were randomly divided into a control group (CG) and an experimental group (EG). The specimens were divided equally (n = 10): CG, stored in artificial saliva at 37°C ± 1°C for 14 days; and the EG, exposed to cigarette smoke using a sealed acrylic device with 10 cigarettes per cycle for 20 cycles. A spectrophotometer was used to evaluate changes in colour and light transmittance based on CIELab* colour parameters. Measurements were taken before (T0) and after (T1) exposure. The total colour difference (∆E) and National Bureau of Standards (NBS) were calculated. T-tests were used for comparisons at a significance level of 0.05.

Statistically significant colour changes (P < 0.05) were observed at T1 in the EG (luminosity [L*] = 77.20 ± 3.33; difference along green-red axis [a*] = -1.57 ± 0.02; and difference along blue-yellow axis [b*] = 6.74 ± 0.55) compared to the CG. The mean ∆E* value at T1 was significantly higher in the EG (14.27 ± 2.72) compared to the CG (2.39 ± 0.56; P = 0.002). Light transmittance decreased significantly after cigarette smoke exposure (CG = 68.396 ± 8.683; EG = 59.538 ± 5.089; P = 0.012).

Cigarette smoke exposure significantly altered the optical properties of clear orthodontic aligners, affecting both colour and light transmittance.