title: In vitro and in vivo corrosion evaluation of nickel-chromium- and copper-aluminum-based alloys.
abstract: BACKGROUND
  The low resistance to corrosion is the major problem related to the use of copper-aluminum alloys.
  
  
  OBJECTIVE
  This in vitro and in vivo study evaluated the corrosion of 2 copper-aluminum alloys (Cu-Al and Cu-Al-Zn) compared with a nickel-chromium alloy.
  
  
  METHODS
  For the in vitro test, specimens were immersed in the following 3 corrosion solutions: artificial saliva, 0.9% sodium chloride, and 1.0% sodium sulfide. For the in vivo test, specimens were embedded in complete dentures, so that one surface was left exposed. The 3 testing sites were (1) close to the oral mucosa (partial self-cleaning site), (2) surface exposed to the oral cavity (self-cleaning site), and (3) specimen bottom surface exposed to the saliva by means of a tunnel-shaped perforation (non-self-cleaning site).
  
  
  RESULTS
  Almost no corrosion occurred with the nickel-chromium alloy, for either the in vitro or in vivo test. On the other hand, the 2 copper-aluminum-based alloys exhibited high corrosion in the sulfide solution. These same alloys also underwent high corrosion in non-self-cleaning sites for the in vivo test, although minimal attack was observed in self-cleaning sites.
  
  
  CONCLUSIONS
  The nickel-chromium alloy presented high resistance to corrosion. Both copper-aluminum alloys showed considerable corrosion in the sulfide solution and clinically in the non-self-cleaning site. However, in self-cleaning sites these 2 alloys did not show substantial corrosion.
authors.affiliation: School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: O F
authors.initials: OF
authors.lastname: Benatti
authors.forename: W G
authors.initials: WG
authors.lastname: Miranda
authors.forename: A
authors.initials: A
authors.lastname: Muench
mesh_terms: D000535:Aluminum / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D006801:Humans; D012463:Saliva; D012464:Saliva, Artificial; D013440:Sulfides
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys; D012464:Saliva, Artificial; D013440:Sulfides; D003300:Copper; D000535:Aluminum; C033479:sodium sulfide