Toxicity of Metal Ions Released from a Fixed Orthodontic Appliance to Gastrointestinal Tract Cell Lines

The mechanism of toxicity and cellular response to metal ions present in the environment is still a very current area of research. In this work, which is a continuation of the study of the toxicity of metal ions released by fixed orthodontic appliances, eluates of archwires, brackets, ligatures, and bands are used to test the prooxidant effect, cytotoxicity, and genotoxicity on cell lines of the gastrointestinal tract. Eluates obtained after three immersion periods (3, 7, and 14 days) and with known amounts and types of metal ions were used. Four cell lines-CAL 27 (human tongue), Hep-G2 (liver), AGS (stomach) and CaCo-2 (colon)-were treated with each type of eluate at four concentrations (0.1x, 0.5x, 1.0x, and 2.0x) for 24 h. Most eluates had toxic effects on CAL 27 cells over the entire concentration range regardless of exposure time, while CaCo-2 proved to be the most resistant. In AGS and Hep-G2 cells, all samples tested induced free radical formation, with the highest concentration (2x) causing a decrease in free radicals formed compared to the lowest concentrations. Eluates containing Cr, Mn, and Al showed a slight pro-oxidant effect on DNA (on plasmid & phi;X-174 RF I) and slight genotoxicity (comet assay), but these effects are not so great that the human body could not resist them. Statistical analysis of data on chemical composition, cytotoxicity, ROS, genotoxicity, and prooxidative DNA damage shows the influence of metal ions present in some eluates on the toxicity obtained. Fe and Ni are responsible for the production of ROS, while Mn and Cr have a great influence on hydroxyl radicals, which cause single-strand breaks in supercoiled plasmid DNA in addition to the production of ROS. On the other hand, Fe, Cr, Mn, and Al are responsible for the cytotoxic effect of the studied eluates. The obtained results confirm that this type of research is useful and brings us closer to more accurate in vivo conditions.

Automated summary

This study investigates the toxicity and cellular response to metal ions released by fixed orthodontic appliances on gastrointestinal tract cells. The eluates of archwires, brackets, ligatures, and bands were tested for their prooxidant effect, cytotoxicity, and genotoxicity on four different cell lines. The results show that most eluates were toxic to CAL 27 cells and that CaCo-2 cells were the most resistant. The eluates induced free radical formation in AGS and Hep-G2 cells, and eluates containing Cr, Mn, and Al showed slight prooxidant effect and genotoxicity.