In vitro cytotoxicity of different thermoplastic materials for clear aligners

OBJECTIVES: To investigate the in vitro cytotoxicity of different thermoplastic materials for clear aligners on human primary gingival fibroblasts (HGFs). MATERIALS AND METHODS: Four materials for clear aligners were considered in this study: Duran (Scheu-Dental GmbH, Iserlohn, Germany), Biolon (Dreve Dentamid GmbH, Unna, Germany), Zendura (Bay Materials LLC, Fremont, CA, USA), and SmartTrack (Align Technology, San Jose, CA, USA). Three out of four materials (Duran, Biolon, Zendura) were assessed as thermoformed and nonthermoformed, whereas the SmartTrack was assessed only as thermoformed. The samples were placed at 37°C in airtight test tubes containing Dulbecco's Modified Eagle's Medium (DMEM; 0.1 mg/mL) for 14 days. The cell viability of HGFs cultured with this medium was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Data were analyzed by means of one-way and two-way analysis of variance and post hoc tests (α = 0.05). RESULTS: Each material exhibited a slight cytotoxic effect after 14 days. The highest cytotoxicity level on HGFs was achieved by Biolon (64.6% ± 3.3 of cell viability), followed by Zendura (74.4% ± 2.3 of cell viability), SmartTrack (78.8% ± 6.3 of cell viability), and finally Duran (84.6% ± 4 of cell viability), which was the least cytotoxic. In the comparison between nonthermoformed and thermoformed materials for Duran, Biolon, and Zendura, the thermoformed materials showed the highest level of cytotoxicity (P < .001). CONCLUSIONS: Under the experimental conditions of this study, all the materials for clear aligners presented a slight cytotoxicity. Biolon was the most cytotoxic and the thermoforming process increased the cytotoxicity of the materials.