Nickel allergy in relation to piercing and orthodontic appliances--a population study.

BACKGROUND Studies have shown conflicting results on the association between nickel exposure from orthodontic appliances and nickel sensitization. OBJECTIVES & METHOD: In a cross-sectional study, we investigated the association between nickel sensitization and exposure to orthodontic appliances and piercings. 4376 adolescents were patch tested following a questionnaire asking for earlier piercing and orthodontic treatment. Exposure to orthodontic appliances was verified in dental records. RESULTS Questionnaire data demonstrated a reduced risk of nickel sensitization when orthodontic treatment preceded piercing (OR 0.46; CI 0.27-0.78). Data from dental records demonstrated similar results (OR 0.61, CI 0.36-1.02), but statistical significance was lost when adjusting for background factors. Exposure to full, fixed appliances with NiTi-containing alloys (OR 0.31, CI 0.10-0.98) as well as a pooled 'high nickel-releasing' appliance group (OR 0.56, CI 0.32-0.97) prior to piercing was associated with a significantly reduced risk of nickel sensitization. CONCLUSION High nickel-containing orthodontic appliances preceding piercing reduces the risk of nickel sensitization by a factor 1.5-2. The risk reduction is associated with estimated nickel release of the appliance and length of treatment. Sex, age at piercing and number of piercings are also important risk indicators. Research on the role of dental materials in the development of immunological tolerance is needed.