Corrosion Resistance of Dental Alloys in Pseudo-Oral Environment

Abstract

The corrosion resistance of dental alloys was investigated by taking anodic polarization measurements in 1 mass%-lactic acid, artificial saliva, and cell-culture medium solutions. The role of alloying elements in the passive film that formed on the dental alloys hy the anodic polarization was examined using X-ray photoelectron spectroscopy. The quantity of metals released from the denial alloy into the 1% lactic acid solution at each anodic potential was compared. In the anodic polarization curves for the Au and Au-Ag-Pd alloys, the current density tended to decrease with higher Au content. In the Ag alloy, the current density sharply increased in the 1 mass%-lactic acid solution. On the other hand, the passivity zone was slightly seen in the artificial saliva and Eagle's medium solutions. Amalgam had a low open-circuit potential, and a passivation peak was seen. The peaks of the Au4f and Ag3d orbital were high in the surface of the passive film formed on the Au and Au--Ag-Pd alloys by anodic polarization in the artificial saliva solution. SnO 2 and In 2 O 3 peaks were observed in the passive film formed on the Ag alloy. SnO 2 and CuO peaks were seen in the passive film on amalgam surface. In the Au and Au-Ag-Pd alloys, Cu was released most in the low potential region less than 1.0 or 0.5 V vs. SCE, respectively. For the Ag alloys, Zn release was most, and Ag, Sn and In were also released. In amalgam, Sn release increased with higher anodic potentials. Cu release also increased at potentials over 0 V. Ag and Hg release increased from potentials over 0.5 V. Considering that the electrode potential measured in the pseudo-oral environment is a maximum of 0.2 V, it is important to examine the effect of Cu and Ag releases for the Au and the Au-Ag-Pd alloys, Zn release for the Ag alloy, and Sn and Cu releases for amalgam.