Nickel allergy in a Swedish adolescent population and its relation to orthodontic treatment and lifestyle factors

Nickel stands out as the main cause of contact allergy in both children and adults, which has given rise to concern and the introduction of regulations by official bodies. Today´s youths are frequently exposed to body piercing and orthodontic treatment. Changes in youth lifestyle practices are also likely to influence nickel exposure and thus, the occurrence of nickel allergy. However, against patient and parental concern regarding nickel exposure to orthodontic appliances, often evoked by allergies following piercing, stand results from studies indicating that early orthodontic appliance treatment may reduce, rather than increase, prevalence of nickel allergy; a finding that has been suggested to result from tolerance induction by early exposure to nickel via the oral route. The objective of the present thesis was to investigate the association between nickel allergy and exposure to different orthodontic appliances and lifestyle, in particular piercing, as well as to study nickel release from orthodontic appliances into the oral cavity. Furthermore, one objective was to establish baseline prevalence data of nickel allergy in a Swedish adolescent population. Data was generated from a cross-sectional survey, in which about 6000 youths completed a questionnaire and almost 4500 of these were patch-tested for contact allergy. Information on exposure to orthodontic appliances was verified by dental records, whilst nickel content in saliva and dental biofilm was measured in a clinical study. Questionnaire data demonstrated a reduced risk of nickel allergy when orthodontic treatment preceded piercing (OR 0.5; 95 % CI 0.3-0.8) and similar results were found for data verified from dental records, however statistical significance was lost when adjusting for background factors (OR 0.6, 95 % CI 0.4-1.0). Exposure to full fixed appliances with NiTi-containing alloys, as well as a pooled ‘high nickel-releasing’ appliance group prior to piercing correlated with a significantly red