Exploring the degradation behavior of MgXAg alloys by in vitro electrochemical methods

Magnesium as biodegradable biomaterial could serve as bone augmentation material in implant dentistry. The knowledge about the predictability of the biodegradation process is essential as this process needs to go hand in hand with the formation of new bone to gradually replace the augmentation material. Therefore, this work aimed to assess if the electrochemistry (EC) measurements of the corrosion process correlate with the surface features at various time points during the surface degradation, in order to describe the degradation process of Mg and Mg alloys more reliably, under the assumption that differences in EC behavior can be detected and related to specific patterns on the surface. In this test setup, a special optical chamber was used for electrochemical measurements on Mg and Mg-alloys (Mg2Ag, Mg4Ag, and Mg6Ag). Specimens were investigated using different circulating cell culture solutions as electrolytes, these were minimum essential medium (MEM), Hank's Balanced Salt Solution (HBSS), and MEM+ (MEM with added sodium hydrogen carbonate) at 37 °C. Open circuit potential measurements (OCP) over 30 min followed by cyclic polarization were performed. The electrochemistry data, including OCP, exchange current density and corrosion potential, were compared with visible changes at the surface during these treatments over time. The results show that the addition of silver (Ag) leads to a "standardization" of the degradation regardless of the selected test medium. It is currently difficult to correlate the visible microscopic changes with the data taken from the measurements. Therefore, further investigations are necessary.