Chromium release from new stainless steel, recycled and nickel-free orthodontic brackets

Maria Francesca Sfondrini, Vittorio Cacciafesta, Elena Maffia, Sarah Massironi, Andrea Scribante, Giancarla Alberti, Raffaela Biesuz, Catherine Klersy

Research output: Contribution to journalArticlepeer-review


Objective: To test the hypothesis that there is no difference in the amounts of chromium released from new stainless steel brackets, recycled stainless steel brackets, and nickel-free (Ni-free) orthodontic brackets. Materials and Methods: This in vitro study was performed using a classic batch procedure by immersion of the samples in artificial saliva at various acidities (pH 4.2, 6.5, and 7.6) over an extended time interval (t1 = 0.25 h, t2 = 1 h, t3 = 24 h, t4 = 48 h, t5 = 120 h). The amount of chromium release was determined using an atomic absorption spectrophotometer and an inductively coupled plasma atomic emission spectrometer. Statistical analysis included a linear regression model for repeated measures, with calculation of Huber-White robust standard errors to account for intrabracket correlation of data. For post hoc comparisons the Bonferroni correction was applied. Results: The greatest amount of chromium was released from new stainless steel brackets (0.52 ± 1.083 μg/g), whereas the recycled brackets released 0.27 ± 0.38 μg/g. The smallest release was measured with Ni-free brackets (0.21 ± 0.51 μg/g). The difference between recycled brackets and Ni-free brackets was not statistically significant (P = .13). For all brackets, the greatest release (P = .000) was measured at pH 4.2, and a significant increase was reported between all time intervals (P <.002). Conclusion: The hypothesis is rejected, but the amount of chromium released in all test solutions was well below the daily dietary intake level.

Original languageEnglish
Pages (from-to)361-367
Number of pages7
JournalAngle Orthodontist
Issue number2
Publication statusPublished - Mar 2008


  • Artificial saliva
  • Batch procedure
  • Chromium release
  • Nickel-free brackets
  • Reconditioned brackets

ASJC Scopus subject areas

  • Orthodontics


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