Evaluation of color changes in clear aligners exposed to cigarette and electronic cigarette smoke

Objective: The aim of this study was to evaluate the color changes in clear aligners fabricated from a conventional thermoformed multilayer polyurethane material (Invisalign®) and a three-dimensionally direct-printed monolayer polyurethane material (Graphy®) following exposure to conventional cigarette smoke (CS), electronic cigarette aerosol (EC), and heated tobacco product aerosol (HTP), and to determine which type of smoke had the greatest effect. Materials and Methods: Specimens were exposed to (CS), (HTP), and (EC) aerosols for seven consecutive days using a smoking simulation device. During the intervals between smoking cycles, the specimens were stored in artificial saliva to mimic the oral environment, while the saliva(S) group was immersed in artificial saliva for the entire study period. Color measurements were performed with a spectrophotometer device before exposure and every day after the daily exposure cycle. L*, a*, b* values were measured for each sample. The obtained color change values (ΔE00) were comparatively evaluated among different cigarette types and aligner materials. Results: In all aligners, clinically unacceptable match (ΔE00 > 1.8) were reached from the second day onward. The highest discoloration values were observed on day 7. The conventional cigarette group exhibited significantly greater discoloration compared with the other groups, exceeding the extremely unacceptable match (ΔE00 > 5.4) from day 5. No significant difference was found between Invisalign® and Graphy® aligners overall. Conclusion: Cigarette and electronic cigarette exposures adversely affected the esthetic properties of clear aligners. Among them, conventional cigarette smoke caused the greatest degree of discoloration. Keywords: clear aligner, discoloration, conventional cigarette, electronic cigarette, heated tobacco product