title: Nickel ion concentrations in the saliva of patients treated with self-ligating fixed appliances: a prospective cohort study.
abstract: OBJECTIVE
  Orthodontic appliances are considered to be highly biocompatible although adverse effects attributed to the release of nickel ions (Ni(2+)) have been documented. Self-ligating brackets have grown in popularity for economic reasons and supposed friction reduction. The aim of the present prospective cohort study was therefore to determine salivary Ni(2+) concentrations in patients undergoing orthodontic treatment with self-ligating fixed appliances.
  
  
  METHODS
  A group of 30 patients between 10 and 13 years of age were treated with self-ligating brackets (SmartClip™), molar bands, and nickel-titanium (NiTi) archwires. Unstimulated saliva samples were collected after different time points (before treatment, after self-ligating bracket and band placement, before archwire insertion, after archwire insertion, and finally 4 and 8 weeks afterwards) and analyzed with an ICP mass spectrometer followed by generalized estimating equation modelling with α = 5 %.
  
  
  RESULTS
  The baseline median salivary Ni(2+) concentration was 21.85 µg/l, while the Ni(2+) concentrations at the following visits ranged between 13.73 and 85.34 µg/l. Significant increases in Ni(2+) levels compared to the baseline levels were detected after band/bracket placement [+59.76 µg/l; 95 % confidence interval (CI) 44.88-74.64 µg/l; P < 0.001] and after archwire insertion (+53.55 µg/l; 95 % CI 25.57-81.52 µg/l; P < 0.001). After 4 weeks, Ni(2+) concentrations returned to initial control levels or were lower.
  
  
  CONCLUSIONS
  Self-ligating orthodontic appliances may affect salivary Ni(2+) concentrations in vivo over the short term. However, levels resembled those documented in conjunction with conventional bracket use and remained below the daily dietary Ni intake.
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Lina
authors.initials: L
authors.lastname: Gölz
authors.affiliation: Department of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.
authors.forename: Anna Christine
authors.initials: AC
authors.lastname: Knickenberg
authors.affiliation: Department of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.|Department of Prosthetic Dentistry, Preclinical Education and Materials Science, School of Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Ludger
authors.initials: L
authors.lastname: Keilig
authors.affiliation: Department of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Reimann
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Bonn, Bonn, Germany.|Department of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany.
authors.forename: Spyridon N
authors.initials: SN
authors.lastname: Papageorgiou
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Bonn, Bonn, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Jäger
authors.affiliation: Department of Oral Technology, School of Dentistry, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany. bourauel@uni-bonn.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bourauel
mesh_terms: D000293:Adolescent; D000497:Alloys / Q000032:analysis / Q000737:chemistry*; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007477:Ions / Q000032:analysis; D008297:Male; D009532:Nickel / Q000032:analysis*; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D011446:Prospective Studies; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*; D012680:Sensitivity and Specificity
chemical_list: D000497:Alloys; D007477:Ions; C013616:nitinol; D009532:Nickel
keywords: Biocompatibility; Corrosion; ICP mass spectrometry; Nickel release; Self-ligating fixed appliance