Salivary levels of nickel, chromium, iron, and copper in patients treated with metal or esthetic fixed orthodontic appliances: A retrospective cohort study.

The purpose of this retrospective cohort study was to measure the salivary levels of nickel (Ni), chromium (Cr), iron (Fe) and copper (Cu) released from metal and esthetic fixed orthodontic appliances. Ninety patients were divided into three groups (n=30): control (those who had never undergone orthodontic treatment), metal appliance (stainless steel brackets and bands, and nitinol archwires) and esthetic appliance (polycarbonate brackets and tubes, and rhodium-coated nitinol archwires). Patients undergoing orthodontic treatment had used their appliances for periods between one and six months.