Abstract: Objective The purpose of this study was to quantitatively evaluate urinary nickel levels, compare with normal physiological nickel index and summarize the dynamic metabolic regularity of systemic nickel for adolescents in the initial period of orthodontic fixed treatment. Methods The subjects were consisted of 15 boys and 16 girls (age range: 10-14 years). Urinary samples were collected before treatment (T0) and at three time points (1 month, 3 months, 6 months, respectively T1, T2, T3) after initial treatment, and stored in a low-temperature freezer until the atomic absorption spectrophotometry was carried on. Results The urinary nickel levels of adolescents could be affected significantly by orthodontic fixed appliances. Genders may be associated with different time points. Urinary nickel levels of T1, T2 and T3 were higher than T0. Though the levels of boys are higher that those of girls, the curve depicted of boys and girls might have a similar dynamic changing trend. Conclusion The urinary nickel levels of adolescents could be affected significantly by orthodontic fixed appliances, and may be associated with sampling time periods and genders, which materials without nickel was suggested for clinical treatment.

Key words: fixed appliances, Urinary Nickel Levels, Graphite Furnace Atomic absorption spectrophotometry