Abstract
AimThe present study evaluated the temporal release of Co Cr, Mn, and Ni from the components of a typical orthodontic appliance during simulated orthodontic treatment.Materials and methodsSeveral commercially available types of bands, brackets, and wires were exposed to an artificial saliva solution for at least 44 days and the metals released were quantified in regular intervals using inductively coupled plasma quadrupole mass spectrometry (ICP-MS, Elan DRC+, Perkin Elmer, USA). Corrosion products encountered on some products were investigated by a scanning electron microscope equipped with an energy dispersive X-ray microanalyzer (EDX).ResultsBands released the largest quantities of Co, Cr, Mn, and Ni, followed by brackets and wires. Three different temporal metal release profiles were observed: (1) constant, though not necessarily linear release, (2) saturation (metal release stopped after a certain time), and (3) an intermediate release profile that showed signs of saturation without reaching saturation. These temporal metal liberation profiles were found to be strongly dependent on the individual test pieces. The corrosion products which developed on some of the bands after a 6-month immersion in artificial saliva and the different metal release profiles of the investigated bands were traced back to different attachments welded onto the bands.ConclusionThe use of constant release rates will clearly underestimate metal intake by the patient during the first couple of days and overestimate exposure during the remainder of the treatment which is usually several months long. While our data are consistent with heavy metal release by orthodontic materials at levels well below typical dietary intake, we nevertheless recommend the use of titanium brackets and replacement of the band with a tube in cases of severe Ni or Cr allergy.
Highlights
Materials and methodsThe metallic components presently used in orthodontic treatment differ substantially with respect to their composition and characteristics, reflecting the different physical and mechanical properties required
Aim The present study evaluated the temporal release of Co Cr, Mn, and Ni from the components of a typical orthodontic appliance during simulated orthodontic treatment
While our data are consistent with heavy metal release by orthodontic materials at levels well below typical dietary intake, we recommend the use of titanium brackets and replacement of the band with a tube in cases of severe Ni or Cr allergy
Summary
Materials and methodsThe metallic components presently used in orthodontic treatment differ substantially with respect to their composition and characteristics, reflecting the different physical and mechanical properties required. The introduction of nickel–titanium alloys in 1971 for instance brought important progress for orthodontic treatment [2].Continuous long-term contact of orthodontic materials with teeth, gingivae, and the oral environment in general results in biodegradation of metals. Thereby, the patient is exposed to increased levels of metals and metal ions [13, 23] beyond those resulting from dietary intake and other forms of exposure. The average daily intakes of nickel and chromium in food are, for instance, estimated to be 200–300 lg nickel/day [8] and 30–100 lg chromium/day [21]. Nickel–titanium alloys generally have a nickel content of more than 50% compared to approximately 8% in steel wires [23].
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