Localized Toxicity in Patients with Fixed Orthodontic Appliance:A Case Control Study

Fixed orthodontic appliances made of metal alloys are routinely used in dental practise to correct malocclusion. Oral environment favours the biodegradation of metal alloys. The discharged metal ions accumulate cumulatively on the adjacent tissues and results in toxic effects on cellular metabolism and DNA stability. The study was designed to evaluate localized genetic and cytokinetic toxicity due to fixed orthodontic appliance by measuring micronuclei frequency and other nuclear abnormalities in the buccal mucosal cells. Subjects with orthodontic appliance were selected as exposure cohort (n=20) and subjects without orthodontic appliance were selected as comparative cohort (n=20). Buccal smears were collected and DNA specific feulgen stain was used. Micronuclei, nuclear bud and binucleate cells frequency were recorded and compared between the study groups. We found a significant increase in the frequency of cells with micronuclei (p<0.001) and binucleate cells(p=0.002) in the exposure cohort compared to controls. The increase in the indicators of genotoxicity and cytokinetic toxicity in the exposed cohort compared to controls could be attributed to the exposure to the metal ions released from long term orthodontic appliance treatment. Increase in binucleate cells in subjects with fixed orthodontic appliance was demonstrated for the first time in our study. The cellular changes due to toxicity could be the predisposing factor for the occurrence of immune mediated oral mucosal lesions in orthodontic patients.