Nickel hypersensitivity reaction before, during, and after orthodontic therapy.

Nickel is a strong biological sensitizer and consequently may induce a delayed hypersensitivity reaction (type IV immune response). Because nickel is a component of the majority of the orthodontic alloys, the objectives of this cross-sectional study were to determine the prevalence of nickel hypersensitivity reaction before, during, and after orthodontic therapy with conventional stainless steel brackets and wires; to evidence the induction of this reaction by the orthodontic appliances; and to characterize the nickel hypersensitive persons. Nickel patch tests and a questionnaire were used to evaluate the hypersensitivity to this metal. The total sample consisted of 170 patients, 105 females and 65 males, from the orthodontic department at Bauru Dental School, University of São Paulo. They were divided into three groups as follows: A (n = 60), patients before the beginning of orthodontic therapy; B (n = 66), patients currently undergoing orthodontic treatment, and C (n = 44), patients who had undergone orthodontic treatment previously. The chi-square test (chi2) showed an allergic reaction in 28.3% of the total sample with 23% female and 5.3% male. This indicated a gender difference (chi2 = 10.75, p < 0.001). There was a positive association between nickel hypersensitivity and previous personal allergic history to metals (chi2 = 34.88, p < 0.0001) as well as with the daily use of metal objects (chi2 = 11.95, p < 0.0005). There was no statistically significant difference in the prevalence of contact dermatitis among the three groups (chi2 = 0.39, p = 0.848). This suggests that orthodontic therapy with conventional stainless steel appliances does not initiate or aggravate a nickel hypersensitivity reaction.