Comparative evaluation of cytotoxicity of various clear aligners: An in-vitro study

Background: Clear aligners, made from thermoplastics like polyurethane, are popular due to their invisibility and comfort. However, concerns exist over potential cytotoxicity, material interactions, and allergic reactions, prompting research into their safety and effects on oral health.Materials and Methods: Four commercially available clear aligner brands that are widely used in India were included in this study. Three sterile clear aligner samples from each brand were immersed in Dulbecco's Modified Eagle Medium (DMEM, Gibco®, Carlsbad, CA, USA) for 14 days under controlled conditions, filtered, and stored for testing. Commercially available L929 fibroblast cells (NCCS-Pune, India) were cultured and treated with aligner extracts to assess cytotoxicity using MTT assays at days 1, 7, and 14. Cell viability was measured via absorbance at 570 nm with Synergy hybrid Multi-Mode Reader (BioTek, Winooski, VT, US). Data was analyzed using SPSS version 22. Shapiro-Wilk tested normality. ANOVA compared means; p≤0.05 was significant.Results: On day 1, none of the clear aligner systems showed cytotoxicity, with Group C (ClearCorrect) exhibiting the highest cell viability (99.04%±2.90). Day 7 results were similar, with Group C again leading (102.1%±2.19). By day 14, Group C maintained the highest viability (106.5%±1.99). All differences were statistically insignificant (p>0.05).Conclusion: The study concluded that none of the aligner systems showed cytotoxicity at any time point. ClearCorrect had the highest cell viability, followed by SureSmile, Graphy, and Invisalign. Although cell viability increased from day 1 to day 14, differences between aligners and across timelines were not statistically significant.