Nickel and chromium release in vitro from newly engineered brackets
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Abstract
Orthodontic brackets are susceptible to corrosion in the oral environment. This corrosion manifests itself by releasing ions from its alloy into solution. If these ions are released at sufficient quantities, they have the potential to cause allergic reactions in sensitive patients. The first purpose of this study was to compare the release of chromium and nickel ions into artificial saliva between brackets marketed as highly biocompatible and older brackets which did not attempt to limit corrosion. The second purpose of this study was to determine if electrogalvanic corrosion takes place between a bracket and a wire while ligated. Prior to experimentation, all brackets were examined under SEM with an energy dispersive x-ray microanalyzer to determine composition. Twelve brackets from each brand were immersed in artificial saliva for 24 hours, 7 (1+6) days, and 28 (1+6+21) days at which times they were analyzed by ICP MS for chromium and nickel ions. In addition, Ni-Ti wire, Ni-Ti wire ligated to a Cr- Co bracket, and Cr-Co brackets alone were immersed in artificial saliva for one week and then analyzed by ICP-MS. The results were as follows: (1) The newly engineered brackets tested (with the exception of GAC's Platina bracket) release fewer Cr & Ni ions than the original AISI 303 Diamond bracket by Ormco. (2) GAC's Platina palladium covered brackets exhibit a significant surge of Cr (P=0.01) & Ni (P=0.02) release in the first 24 hours after placement in artificial saliva due to voids discovered in the plating. (3) Maximum release of chromium and nickel ions occurred in the first 24 hours after placement in artificial saliva. (4) On average, the one-piece brackets used in this study, released less nickel ions over time than did two-piece brackets. (5) The Ovation Platina and Diamond brackets released the largest amount of nickel ions over the course of the experiment, while the Sprint, Elite Opti-MIM, Elite Opti-MIM NL and Nu-Edge MBT brackets released less nickel ions. (6) The Ovation Platina released the largest amount of chromium ions over the course of the experiment, while the Diamond, Elite Opti-MIM NL and Nu-Edge MBT brackets released an intermediate amount of chromium ions, while the Sprint and Elite Opti-MIM brackets released the fewest amount of ions. (7) No evidence of galvanic corrosion has been shown between a Cr Co bracket and a Ni-Ti wire while ligated by a plastic ligature.
Description
Thesis (MSD)--Boston University, Goldman School of Dental Medicine, 2005 (Orthodontics).
Includes bibliographical references: leaves 88-91.
Includes bibliographical references: leaves 88-91.
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This work is being made available in OpenBU by permission of its author, and is available for research purposes only. All rights are reserved to the author.