Corrosion of dental alloys in vitro by differential oxygen concentration

Abstract

— The corrosion of a conventional and a high Cu dental amalgam, a Cu‐Zn dental alloy, and pure silver (control) were studied in vitro under conditions of differential oxygenation, resembling a partially covered dental filling. The experimental method enabled the simultaneous recording of separate pH changes at anordic and cathodic areas and of the corrosion current generated; the corrosion products formed and the corroded alloys were examined by powder X‐ray diffraction, optical and scanning electron microscopy, and EDAX elemental analysis. Marled anodic pH drops and cathodic pH rises were seen which, with the total electric change integrated from the recordings, formed the basis for a qualitative evaluation (electrochemical reaction schemes) and a quantitative evaluation (amounts of metal corroded) of the progress of corrosion. The corrosion products found were SnG2, ZnSn(OH)6, and Cu2O of the amalgams, and Zn5(OH)8Cl2 of the Cu‐Zn alloy; twice as much tin corroded from the conventional as from the high Cu amalgam, and zinc corroded selectively from the Cu‐Zn alloy. These findings were substantiated by the microscopic and EDAX observations.

Corrosion investigation of two materials for implant supraconstructions coupled to a titanium implant

“…As opposed to comparable investigations (3,13), the corrosion current observed was not accompanied by any noteworthy pH change in either corrosion cell. But, since the total electric charge transferred by the corrosion process here is two orders of magnitude lower than in those investigations, the expected, smaller pH rise in the titanium cell may be masked by the freely available carbon dioxide dissolving in the electrolyte, forming a carbonic acid/hydrogen carbonate bufler with a weak acid reaction, pK = 6.35 (14).…”

Corrosion current and pH rise around titanium coupled to dental alloys

“…In the anodic side, the combined result of the tin corrosion and the oxygen equilibrium can be written as Sn-H 4OH--»SnOjw-1-2H2O-1-4e- (7) This reaction is driven toward the right by the removal of electrons and by the precipitation of SnO2(s) (which has a verj' low solubility), tbus consuming hydroxide ions and causing the observed pH drop at the anode. Owing to the freshly polished metal surfaces, the initial corrosion current is high.…”

Effects of titanium-dental restorative alloy galvanic couples on cultured cells

“…7,8 The corrosion currents of the amalgams coupled to In investigations of the potential of metals and alloys to titanium were reported to increase to a maximum and then form galvanic cells, the in vitro electrochemical corrosion decrease slowly over time. The maximum currents measured were within the ranges of currents identified by electrogustometric methods for eliciting an oral sensation in healthy individuals.…”

“…To coupled to titanium may increase the release of metallic corrosion products, cause local tissue damage, and comproelectrically connect the samples, the free end of the wire from a test sample was manually twisted to the free end mise the longevity of the restorations. 7,8,10 Therefore, in this investigation it is hypothesized that coupling titanium of the wire attached to a titanium sample. An electrical connection was verified by a portable multimeter on obto amalgams or gallium alloys increases the release of metallic ion corrosion products and decreases cellular activity taining a 0-V reading.…”