Release of Metal Ions from Orthodontic Appliances: An In Vitro Study

Abstract

In this paper, we report the results of an in vitro experiment on the release of metal ions from orthodontic appliances composed of alloys containing iron, chromium, nickel, silicon, and molybdenum into artificial saliva. The concentrations of magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, titanium, vanadium, manganese, iron, cobalt, copper, zinc, nickel, and chromium were significantly higher in artificial saliva in which metal brackets, bands, and wires used in orthodontics were incubated. In relation to the maximum acceptable concentrations of metal ions in drinking water and to recommended daily doses, two elements of concern were nickel (573 vs. 15 μg/l in the controls) and chromium (101 vs. 8 μg/l in the controls). Three ion release coefficients were defined: α, a dimensionless multiplication factor; β, the difference in concentrations (in micrograms per liter); and γ, the ion release coefficient (in percent). The elevated levels of metals in saliva are thought to occur by corrosion of the chemical elements in the alloys or welding materials. The concentrations of some groups of dissolved elements appear to be interrelated.

Metal ion release from silver soldering and laser welding caused by different types of mouthwash

“…4,16,19 In order to evaluate the net corrosion of the welded or the soldered parts, the whole appliance was not tested in this study.…”

“…In previous studies, 2,4,5,16,19,29 the metal ion release from different types of orthodontic appliances in various solutions was examined for different time periods. In our study, corrosion was evident after the first 24 hours.…”

In vitro Cr(VI) speciation in synthetic saliva after releasing from orthodontic brackets using silica-aptes separation and GF AAS determination

“…[1][2][3][4] The corrosion of the orthodontic brackets in the oral environment has concerned the clinicians for two main reasons: (i) the possibility of the body absorb the corrosion products suffering localized or systemic effects; or (ii) the clinical performance of the orthodontic appliances. 4,5 The former is concerned mainly to the toxic effect of Cr(VI), that can be present in the bracket composition or can be interconvert by Cr(III) oxidation in the saliva environment. In the oral environment, orthodontic appliances are potentially exposed to physical damage and chemical agents.…”

“…1,6 Most metallic devices used during orthodontic treatment is made of stainless steel type austenitic (AISI type 316L stainless steel), which has 18% (m m -1 ) chromium, 8% (m m -1 ) nickel, 2 to 3% (m m -1 ) molybdenum and low carbon content. 4,5 The corrosion process of metallic brackets has been linked to the deterioration of their mechanical properties and as mentioned above, to adverse biological effects. 6 It is well known that the presence of chromium in an alloy can increase its corrosion resistant properties due to the ability to form a protective oxide film over the metallic surface.…”

Infiltration of trace metal ions in the oral mucosa of a rat analyzed using SRXRF, XAFS, and ICP-MS

“…Metal elution from orthodontic devices during treatment is influenced by various factors such as chemical (e.g., salivary pH) and biological (e.g., bacteria and inflammation) environments, morphological changes (e.g., bending stress of devices), and physiological properties (e.g., fluidity of saliva) [5][6][7][8][9][10][11] . Simulating the accurate environment of the oral cavity during orthodontic treatment is difficult because the aforementioned metal elution is influenced by such a variety of factors, and therefore, previous studies primarily focused on the metal-ion release from devices under certain conditions, as described above.…”