Corrosion of dental nickel-aluminum bronze with a minor gold content-mechanism and biological impact.
OBJECTIVE
To study corrosion and to evaluate biological effects in vitro of corrosion products of a copper-aluminum-nickel alloy with 2% gold.


METHODS
The alloy NPGtrade mark+2 with the nominal composition Cu:77.3; Al:7.8; Ni:4.3; Fe:3.0; Zn:2.7; Au:2.0; and Mn:1.7 was characterized. Static immersion in acidic saline, pH 2.2-2.4, was used to determine release of metallic elements in a milieu simulating the condition of plaque build-up in interproximal areas of the tooth. Corrosion and surface reactions in saline and artificial saliva were studied by electrochemical techniques including registration of open-circuit-potentials, polarization curves and impedance spectra. Extracts were made in cell culture media and acidic saline and used for MTT test for cytotoxicity and HET-CAM method for irritation.


RESULTS
The mean amount of elements released in the acidic saline were in microg cm(-2) : Cu:632; Al:210; Ni:144; Fe:122; Zn:48; Mn:52. No protective film was formed on the surface of the alloy, as extensive corrosion was observed in both saline and artificial saliva. The corrosion rate was higher in saline than in artificial saliva. Acidic extracts of the alloy diluted up to 64 times reduced cell viability with 80% or more. The extract induced coagulation of the blood vessels of the CAM and was rated as moderate irritant solution.


CONCLUSIONS
The nickel-aluminum bronze showed high corrosion rate caused by an inability to create a protective surface layer. High levels of toxic elements were found after static immersion testing, and the corrosion products had a distinct adverse effect on the biological activity.
Ardlin
Berit I
BI
Department of Odontology/Dental Materials Science, Dental Technician Programme, Umeå University, Umeå, Sweden. berit.ardlin@odont.umu.se
Lindholm-Sethson
Britta
B
Dahl
Jon E
JE
D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003300:Copper / Q000737:chemistry* / Q000494:pharmacology*; D003343:Corrosion; D003764:Dental Materials / Q000737:chemistry*; D004563:Electrochemistry; D006046:Gold / Q000737:chemistry*; D007101:Immersion; D051379:Mice; D009532:Nickel / Q000737:chemistry* / Q000494:pharmacology*; D013057:Spectrum Analysis; D013314:Stress, Mechanical
D003764:Dental Materials; C062136:nickel copper alloy; D006046:Gold; D003300:Copper; D009532:Nickel