Urinary nickel and chromium levels in orthodontic patients: A case-control study

This case-control study aimed to evaluate the levels of nickel (Ni) and chromium (Cr) ions in the urine of patients undergoing fixed orthodontic treatment, specifically comparing patients treated with nickel-titanium (NiTi) and stainless steel (SS) archwires to a control group without appliance.

Fifty-one participants were recruited and divided into two case groups and one control group, with 17 participants in each group. Group 1 consisted of patients treated with NiTi archwires for six to eight months, and Group 2 included patients treated with SS archwires for 12 to 18 months. The control group comprised participants with no history of orthodontic treatment. Urine samples were collected and analyzed for Ni and Cr concentrations using atomic absorption spectrophotometry. Statistical analyses were performed using the one-way analysis of variance (ANOVA) test.

A significant increase in urinary Cr levels was observed in the SS group compared to both the control and the NiTi groups (P < 0.001). No significant difference in Cr levels was found between the NiTi group and the control group (P > 0.05). Regarding Ni concentrations, no statistically significant differences were detected among the three groups (P = 0.109), although higher levels were observed in the SS group.

SS archwires result in a significantly higher release of Cr ions compared to NiTi archwires and untreated controls, raising potential concerns about prolonged Cr exposure during orthodontic treatment. However, both NiTi and SS archwires appear to release relatively low amounts of Ni, with no significant differences among groups.