Evaluation of variations in composition, corrosion behavior and surface hardness on reusing a Co-Cr-Mo denture alloy

Abstract

We evaluated the variations in the surface composition, corrosion resistance and surface hardness of cobalt-chromium-molybdenum (Co-Cr-Mo) removable partial denture alloy on repeated usage until six generations by adding 50% of weight of fresh alloy pellets to the left-over button and sprue in the previous generation. Corrosion testing was performed with WenkingLB81M potentiostat to evaluate the anodic polarization behavior of the specimens from artificial saliva at room temperature. The breakdown potential for each generation was determined. Scanning electron microscope (SEM) evaluation of the corroded and uncorroded specimens was performed. Vickers hardness number (VHN) was evaluated using Zwick3212 micro hardness indenter with values ranging from 317 to 329 VHN. Surface composition of the corroded and uncorroded specimens was analyzed using X-ray energy dispersive analysis. The Mann Whitney U-test was used to analyze the numerical findings. The breakdown potential values for all six generations were recorded in between + 480 mV and + 500 mV. The hardness and composition showed variations among generations but were statistically insignificant. On the corroded surface, an increase in the Cr and Mo content and decrease in the Co content was observed. SEM photographs show a definite alteration in the surface topography at the corroded site. Within limitations, it was concluded that this alloy could be reused by adding 50% (by weight) of new alloy pellets without significant variation in the abovementioned properties.