Effects of fixed orthodontic treatment on hair nickel and chromium levels: a 6-month prospective preliminary study.

Although nickel and chromium are known as allergen and cytotoxic orthodontic metals, very few and controversial studies have assessed the effect of orthodontic treatment on their systemic levels reflected by their best biomarker of exposure, hair. This prospective preliminary study was conducted to evaluate hair nickel and chromium levels in fixed orthodontic patients. Scalp hair nickel/chromium concentrations of 12 female and 12 male fixed orthodontic patients were measured before treatment and 6 months later, using atomic absorption spectrophotometry. The effects of treatment, gender, and age on hair ions were analyzed statistically (α = 0.05). The patients' mean age was 18.38 ± 3.98 years. The mean nickel levels were 0.1380 ± 0.0570 and 0.6715 ± 0.1785 μg/g dry hair mass, respectively, in the baseline and sixth month of treatment. Chromium concentrations were 0.1455 ± 0.0769 and 0.1683 ± 0.0707 μg/g dry hair mass, respectively. After 6 months, nickel increased for 387 % (paired t test P = 0.0000) and chromium increased for 16 % (P = 0.0002). No significant correlations were observed between any ion levels with age or gender (Spearman P > 0.2). Within the limitations of this preliminary study, it seems that 6 months of fixed orthodontic treatment might increase levels of hair nickel and chromium. Future larger studies are necessary to validate these results.