Corrosion and irritation tests of a dental aluminium bronze. B.I. ARDLIN*1,2, B. LINDHOLM-SETHSON1 and J.E. DAHL2, 1Umeå University, Sweden, 2NIOM – Nordic Institute of Dental Materials, Haslum, Norway
Objectives: The aims of this investigation were to study the corrosion of a copper-aluminium-nickel alloy for fixed prostheses, and to evaluate possible irritant effects of the corrosion products.
Methods: The alloy NPG+2 with the nominal composition Cu:77.3; Al:7.8; Ni:4.3; Fe:3.0; Zn:2.7; Au:2.0; Mn:1.7, was characterized. Static immersion in saline lactic acid solution was selected to quantify metallic elements released in a milieu simulating the condition of plaque build-up in interproximal areas. Corrosion and surface reactions in artificial saliva and saline solutions were studied by electrochemical techniques including registration of polarization curves and impedance spectra. Irritative effect of the corrosion products was assed by the Hen’s egg test-chorio-allantoic membrane, HET-CAM.
Results: Immersion test. The following metal elements were found in the saline lactic acid solutions after immersion of two specimens for 7 days (specimen 1 / specimen 2 in g cm-2): Cu (769/494); Al (249/172); Ni (164/124), Fe (134/109); Zn (59/37); and Mn (61/43). Electrochemical tests. Higher corrosion rates were found in the saline solution, pH 4 or pH 7, than in the aerated or de-aerated artificial saliva solution. No high-quality passive film was formed on the studied alloy as extensive corrosion was observed on test specimens in both solutions. HET CAM. The saline lactic acid extracts induced coagulation of the blood vessels of the chorio-allantoic membrane after an average time of 1 min and the alloy was rated as a moderate irritant.
Conclusions: The copper-aluminium-nickel alloy investigated in this study showed high corrosion caused by an inability to create a stable passivating surface layer. High levels of the elements Cu, Al, Ni, Fe, Zn and Mn were found by static immersion testing, and the corrosion products had an irritant effect.
The project was supported by grants from the European Union Structure Foundation Objective One.