title: Effects of fixed orthodontic treatment using conventional versus metal-injection molding brackets on salivary nickel and chromium levels: a double-blind randomized clinical trial.
abstract: BACKGROUND
  Despite the importance of nickel and chromium release from orthodontic brackets, there are no in vivo or in vitro studies on this issue in the case of metal-injection molding (MIM) brackets.
  
  
  METHODS
  Saliva samples were collected from 30 orthodontic patients divided randomly into two groups of conventional and MIM brackets, before treatment and 2 months later. Approved attendees with odd and even numbers were, respectively, assigned to the control and treatment groups. For blinding, the patients were not informed of their bracket types, and the saliva samples were coded. Nickel and chromium levels were determined using atomic absorption spectrophotometry. Data were analysed using repeated-measures two-way analysis of covariance, independent-samples t-test, chi-squared, Spearman and point-biserial correlation coefficients, Mann-Whitney, and Wilcoxon tests (α = 0.05).
  
  
  RESULTS
  Mean nickel level increased from 7.87±8.14 (pre-treatment) to 12.57±9.96 (2nd month) in the control group, and from 8.62±9.85 (pre-treatment) to 8.86±6.42 µg/l in the MIM group. Both of these increases were significant (Wilcoxon P < 0.03). Average chromium level changed from 0.25±0.56 (pre-treatment) to 0.35±0.62 and from 0.42±0.48 to 0.26±0.57 µg/l in the MIM group. Only the reduction observed in the MIM group was significant (Wilcoxon P = 0.0438). Age and gender had no significant influence on ion levels (P > 0.1). The differences between both ions' levels measured in the 60th day in both bracket groups were not significant (Mann-Whitney P > 0.05). The extents of changes over time were not significantly different between the bracket types (Mann-Whitney P > 0.05).
  
  
  CONCLUSIONS
  The sample size was not predetermined based on power calculations. The spectrophotometer was limited to detecting chromium concentrations above 0.25 µg/l. Ion discharge from brackets might continuously change. The current in vivo methods are unable to take such fluctuations into account.
  
  
  CONCLUSIONS
  Nickel might increase in patients undergoing treatment with both bracket types, although the rate of increase might be greater in patients under treatment with conventional brackets. Using MIM brackets might reduce salivary chromium for a trivial but generalizable amount. Still, ion levels leached from conventional versus MIM brackets might not show a difference after 2 months. Age and gender might not affect the ion levels in normal people or orthodontic patients.
  
  
  BACKGROUND
  The protocol is registered offline at the university library.
  
  
  METHODS
  The protocol was not published before the trail commencement.
  
  
  BACKGROUND
  Self-funded (S. H.).
  
  
  BACKGROUND
  None to declare.
authors.affiliation: *Department of Orthodontics, Dental Branch, Islamic Azad University, Tehran.
authors.forename: Fariborz
authors.initials: F
authors.lastname: Amini
authors.affiliation: *Department of Orthodontics, Dental Branch, Islamic Azad University, Tehran, saghar.harandi@yahoo.com.
authors.forename: Saghar
authors.initials: S
authors.lastname: Harandi
authors.affiliation: *Department of Orthodontics, Dental Branch, Islamic Azad University, Tehran.
authors.forename: Mobina
authors.initials: M
authors.lastname: Mollaei
authors.affiliation: Iranian Tissue Bank and Research Center, Tehran University of Medical Sciences, Tehran, and Department of Dental Anatomy and Morphology, Dental Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Rakhshan
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002857:Chromium / Q000032:analysis*; D003722:Dental Alloys / Q000737:chemistry*; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009532:Nickel / Q000032:analysis* / Q000737:chemistry; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets / Q000145:classification*; D009969:Orthodontic Wires; D012463:Saliva / Q000737:chemistry*; D013054:Spectrophotometry, Atomic / Q000379:methods; D013193:Stainless Steel / Q000737:chemistry; D014025:Titanium / Q000737:chemistry; D055815:Young Adult
chemical_list: D003722:Dental Alloys; D002857:Chromium; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium