title: Nickel hypersensitivity and orthodontic treatment: a systematic review and meta-analysis.
abstract: Nickel-containing alloys are widely used in orthodontic appliances, even though nickel is by far the most common contact allergen. However, the scientific evidence concerning allergic reactions to nickel in orthodontic patients has not been evaluated systematically. The objective of this study was to investigate whether the prevalence of nickel hypersensitivity is affected by orthodontic treatment. Unrestricted electronic and manual searches were performed until July 2013 for human clinical studies assessing orthodontic treatment and nickel hypersensitivity. Methodological limitations were evaluated with the Downs and Black tool. Crude and adjusted odds ratios (ORs) with their 95% confidence intervals (CIs) were calculated from random-effects meta-analyses, followed by subgroup and sensitivity analyses. Thirty studies were included in the review, and 24 datasets with 10 184 patients in the meta-analyses. Orthodontic treatment had no significant effect on nickel hypersensitivity (n = 11; crude OR 0.99; 95%CI: 0.78-1.25; p = 0.914). However, when confounding from factors such as sex and piercings was taken into account, orthodontic treatment was associated with a lower risk of hypersensitivity (n = 1; adjusted OR 0.60; 95%CI: 0.40-0.80; p < 0.001). This was even more pronounced when orthodontic treatment was performed prior to piercing (n = 7; crude OR 0.35; 95%CI: 0.24-0.50; p < 0.001). Orthodontic treatment seems to have a protective role against nickel hypersensitivity, especially when it precedes piercings.
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Bonn, 53111, Bonn, Germany.
authors.forename: Lina
authors.initials: L
authors.lastname: Gölz
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Bonn, 53111, Bonn, Germany.|Department of Oral Technology, School of Dentistry, University of Bonn, 53111, Bonn, Germany.
authors.forename: Spyridon N
authors.identifier: http://orcid.org/0000-0003-1968-3326
authors.initials: SN
authors.lastname: Papageorgiou
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Bonn, 53111, Bonn, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Jäger
mesh_terms: D015982:Bias; D015986:Confounding Factors, Epidemiologic; D017449:Dermatitis, Allergic Contact / Q000453:epidemiology*; D006801:Humans; D009532:Nickel / Q000009:adverse effects*; D009967:Orthodontic Appliances / Q000009:adverse effects*; D010328:Patch Tests; D015995:Prevalence
chemical_list: D009532:Nickel
keywords: contact dermatitis; meta-analysis; nickel allergy; nickel hypersensitivity; orthodontics; piercing