Analyses of rampant corrosion in stainless‐steel retainers of orthodontic patients

Abstract

Retainers were collected from private, university, and dental labs. After viewing these corroded and control appliances using scanning electron microscopy, corroded maxillary and mandibular retainers were selected along with a control stainless-steel retainer for in-depth chemical analysis. Using electron spectroscopy for chemical analysis, monochromated Al x-rays were rastered over areas 1.5 x 0.3 mm. After survey spectra were acquired, high-resolution multiplex scans were obtained and binding energy shifts were noted. Using Auger electron spectroscopy, a spot size of approximately 30 nm was analyzed. Photos, survey scans, and depth profiles were acquired using a 3.5kV Ar(+) ion beam that was calibrated using a SiO2 standard. Via electron spectroscopy for chemical analysis, the brown stains contained Fe and Cr decomposition products in which three carbon species were present. Proteinaceous N was found as amines or amides. No Ni was present because it had solubilized. The Cr:Fe ratio indicated severe Cr depletion in the stained regions (0.2) versus the control regions (1.3). The stained regions appeared mottled, having both dark and light areas. Via AES, the dark versus light areas of the stained regions indicated that there was an absence versus a presence of both Cr and Ni. In the dark areas corrosion penetrated 700 nm; in the light areas the depth equaled 30 nm. By comparison, the passivated layer of the control retainer was 10-nm thick. After sputtering away the affected areas, all specimens had similar spectra as the control regions. The bacterial environment created the mottled appearance and induced electrochemical potential differences so that, upon reducing the passivated layer, an otherwise corrosion-resistant alloy became susceptible to rampant corrosion. An integrated biological-biomaterial model is presented for the classic case of an orthodontic acrylic-based stainless steel retainer subject to crevice corrosion.

Biocorrosion of AISI 304 Stainless Steel by Desulfovibrio desulfuricans in Seawater

“…This indicates the adsorption of organic substances from the solution to the surface. For the SS304 surface exposed to the medium with SRB, the (O)C−N bond may also account for the presence of the peptide linkages of protein compounds in bacteria; the increase in the intensity of C−C bonds indicates the accumulation of the long aliphatic chains in bacterial cells to the stainless steel surface; the CO bond may be assigned to an intracellular storage lipid; the C−O bond may be from the extracellular polymers . The C 1s spectra of the surface in EASW + SRB revealed two additional peaks: carboxylate groups (OC−O) at 289.2 eV and aromatic saturated bonds at 292.6 eV .…”

“…For the SS304 surface exposed to the medium with SRB, the (Od)C-N bond may also account for the presence of the peptide linkages of protein compounds in bacteria; the increase in the intensity of C-C bonds indicates the accumulation of the long aliphatic chains in bacterial cells 12 to the stainless steel surface; the CdO bond may be assigned to an intracellular storage lipid; the C-O bond may be from the extracellular polymers. 22 The C 1s spectra of the surface in EASW + SRB revealed two additional peaks: carboxylate groups (OdC-O) at 289.2 eV and aromatic saturated bonds at 292.6 eV. 23 It is evidence of the accumulation of organic acids (OdC-O), the common bacterial metabolites entrapped within the biofilm, and the appearance of the aromatic saturated bonds, which may be from EPS.…”

Corrosion in Haas expanders with and without use of an antimicrobial agent: an in situ study

“…Under ideal conditions, Fe and Cr peaks in the soldered joint should be high and similar. Graphs with high Fe peaks and medium Cr peaks and presence of O suggest the occurrence of corrosion due to formation of Fe 2 O 3 or hydrated ferric oxide (Fe 2 O 3 x H2O), indicating rust 5,22 . The presence of P with high Fe peaks and medium Cr peaks suggests the occurrence of a process corrosive by formation of iron phosphate (FePO 4 ) 29 .…”

Formação de biofilme e corrosão em aparelhos disjuntores de Haas, com e sem utilização de agente antimicrobiano: estudo in situ

“…Em condições ideais, os picos de Fe e Cr na área de solda devem ser altos e equivalentes. Gráficos com altos picos de Fe e médios picos de Cr e presença de O sugerem a ocorrência de processo corrosivo pela formação de óxido férrico (Fe 2 O 3 ) ou óxido de ferro hidratado (Fe 2 O 3 x H2O), indicando ferrugem (Kuzy et al, 2002;Darabara et al, 2007). A presença de P com altos picos de Fe e médios picos de Cr sugere a ocorrência de processo corrosivo, pela formação de fosfato de ferro (FePO 4 ) (Vinnichenko et al, 2003).…”