Evaluation of the biocompatibility of current CLEAR aligner materials used in orthodontic treatment

AIM: The purpose of this in vitro study was to evaluate the biocompatibility of eight different thermoplastic materials for clear aligners on L929 mouse fibroblasts with in-vitro cytotoxicity (XTT assay and Annexin V/PI staining) tests. MATERIALS AND METHOD: The clear aligner materials tested in the study were: SmartTrack® (Align Technology, USA); Zendura®A and Zendura FLX (Bay Materials LLC, USA); CA® Pro and CA® Pro+, Duran and Duran+ (ScheuDental GmbH, Germany), Provecta (DingZing Advanced Materials, Taiwan). Materials were prepared according to the manufacturer's instructions and ISO parameters. The prepared specimens were sterilized under ultraviolet light in a laminar flow sterile cabin (Esco Airstream Class II BSC, UK) for 40 minutes before the cytotoxicity tests. Mediums were collected and filtered from each of four samples in 1st, 3rd, 7th and 14th days for each material and tested using the L929 cells. Viability of cells was measured after 48 hours. Cytotoxicity was evaluated using XTT assay and apoptosis was determined by Annexin V/PI. All data were statistically analyzed with Two-way ANOVA, One-way ANOVA and Tukey's multiple range tests at a significance level of p<0.05. RESULTS: The cell viability results of the 1st and 14th day extracts among the clear aligner materials showed statistically significant differences (p<0.05). There were significant differences in all tested materials regarding time periods (p<0.05). At the end of the observation period on the 14th day, CA® Pro material showed higher cell viability values then CA® Pro+, SmartTrack®, Duran, Duran+ and Provecta materials (p<0.05). There were significant differences within the clear aligner materials in different time periods regarding apoptosis rate (p<0.05). CONCLUSION: The thermoplastic clear aligner materials tested in the study presented slight to moderate cytotoxicity. Keywords: Clear Aligners, Thermoplastic Materials, Cytotoxicity, Apoptosis, XTT Assay