Hypersensitivity to conventional and to nickel-free orthodontic brackets.

The aim of this study was to evaluate the allergenic potential of orthodontic brackets, comparing the cutaneous sensitivity provoked by metals present in conventional metallic brackets to that provoked by brackets with a low concentration of nickel, known as "nickel-free". A sample was selected from 400 patients undergoing treatment in the orthodontic clinic of the Pontifical Catholic University of Minas Gerais (Belo Horizonte, MG, Brazil), in the period from the beginning of 2002 to the end of 2003. A cutaneous sensitivity patch test containing 5% nickel sulphate was used in 58 patients (30 males and 28 females), aged between 11 and 30, which were using fixed appliances with Morelli brackets in both arches. In a second phase, 30 days later, a comparative test of cutaneous sensitivity was applied to the whole sample with two types of test specimens, in the form of a disc. Two alloys were tested: discs composed of the alloy used in the construction of conventional brackets and discs composed of a nickel-free alloy. The internal part of the forearm was chosen for testing, and 20 test specimens of each experiment (corresponding to the twenty brackets of a complete fixed appliance) were applied. Of the 58 patients evaluated, 16 patients were sensitive to the patch test with 5% nickel sulphate. Out of these 16 patients, 12 developed an allergic reaction to experiment 1 (test specimen with nickel), while in experiment 2, only 5 patients showed sensitivity to that sample. The McNemar test revealed that the nickel-free test specimens provoked less allergic reaction when compared with the conventional alloy (p=0.016).