Evaluation of the Genotoxic Effects of Orthodontic NiTi Wires on Oral Mucosal Cells: An In Vivo Study

Introduction: Orthodontic wires are one of the main components of fixed appliance treatment. Bio-degradation of the metals in these wires could be a source of genotoxicity in the oral cavity. Materials and Methods: After the ethical committee approval and obtaining patient consent, the oral buccal mucosal smears were collected from buccal mucosa using a metal spatula from 27 patients before bonding, during NiTi, and during SS wire stage. The MN assay test was performed using Papanicolaou staining procedure. The micronuclei were examined and counted using previously reported criteria under an electron microscope before bonding, during NiTi, and during SS wire stage. Result: The data collected were subjected to analysis of variance test with Greenhouse–Geisser correction for comparison. It determined that mean mucosa cells differed statistically significantly between time points. Post hoc tests using the Bonferroni correction showed that there was an increase in MN cells from before bonding brackets to the tooth (mean value 6.15 ± 2.769) to during NiTi wire stage (mean value 344.85 ± 64.73), and a reduced count from NiTi wire stage (mean value 344.85 ± 64.73) to SS wire stage (mean value 160.52 ± 47.52). Conclusion: The orthodontic wires were observed to be genotoxic. The NiTi wire is considered to have more potential to cause genotoxicity when compared to SS wires. This could be because of the Ni element present in a higher percentage in NiTi wire as compared to SS wire, hence, element Ni can be considered to be genotoxic. Whether the effect of these wires on oral buccal mucosal cells is reversible has to be evaluated further.