Biodegradable magnesium-calcium (MgCa) alloy is a very attractive biomaterial. Two MgCa alloys below the solid solubility of Ca were considered, as to solely investigate the effect of Ca content on the behavior of magnesium and the pH changes associated to metal dissolution. X-ray diffraction analysis and optical microscopy showed that both Mg-0.63Ca and Mg-0.89Ca alloys were solely composed of α(Mg) phase. Degradation characteristics and electrochemical characterization of MgCa alloys were investigated during exposure to Ringer's solution at 37 °C by electrochemical impedance spectroscopy and scanning electrochemical microscopy. The impedance behavior showed both capacitive and inductive features that are related to the alloy charge transfer reaction and the relaxation of the absorbed corrosion compounds, and can be described in terms of an equivalent circuit. Scanning electron microscopy (SEM) was employed to view the surface morphology of the MgCa samples after 1 week immersion in Ringer's solution showing extensive precipitation of corrosion products, whereas the substrate shows evidence of a non-uniform corrosion process. Energy dispersive analysis showed that the precipitates contained oxygen, calcium, magnesium and chlorine, and the Mg:Ca ratios were smaller than in the alloys. Scanning electrochemical microscopy (SECM) was used to visualize local pH changes associated to these physicochemical processes with high spatial resolution. The occurrence of pH variations in excess of 3 units between anodic and cathodic half-cell reactions was monitored in situ.

Biodegradable magnesium-calcium (MgCa) alloy is a very attractive biomaterial. Binary Mg0.8Ca alloy was fabricated. X-ray diffraction (XRD) analysis and optical microscopy observed showed that Mg0.8Ca alloy was composed of a(Mg) phase. The electrochemical impedance spectroscopy (EIS) technique was used for the study on the degradation characteristics of Mg0.8Ca alloy. Because the proteins have a role on the passivation of metals, the effect of albumin protein addition in NaCl solution on the electrochemical behaviour of Mg0.8Ca alloy was studied. It has been shown that in 0.9 wt% NaCl solution the impedance was mainly characterised by one capacitive and one inductive effect, which related to the alloy charge transfer reaction and the relaxation of the absorbed corrosion compounds. The addition of 37.5 mg/mL albumin protein to 0.9 wt% NaCl solution increased the impedance compared to that without albumin protein. The equivalent circuits simulating the electrochemical behaviour of Mg0.8Ca alloy in 0.9 wt% NaCl solution with and without albumin protein were proposed. The surface morphology of the Mg0.8Ca samples after 1-week immersion in Mg0.8Ca alloy in 0.9 wt% NaCl solution with albumin protein was studied using scanning electron microscopy (SEM). The electrochemical mechanism for degradation of Mg0.8Ca alloy in 0.9 wt% NaCl solution is related to the albumin protein addition.

Titanium alloys are widely used in medical applications, due to their good mechanical properties, high corrosion resistance and biocompatibility. The aim of this paper was to investigate the cytotoxicity of novel titanium alloys: Ti21Nb6Zr15Ta, Ti25Nb10Zr8Ta, Ti17Nb5Zr5Al, Ti7Nb7Zr2Al with fibroblast-like cells derived from human osteosarcoma cell line (HOS). The results were compared with that of conventional biomedical alloys, like Ti6Al7Nb and Ti6Al4V. In vitro citotoxicity of titanium alloys was evaluated by fluorescence microscopy and MTT colorimetric assay. The results showed that the materials analyzed had no cytotoxic effects on HOS fibroblast-like cells, permitting their attachment and proliferation. Also the new titanium alloys present a higher cell viability than that of the conventional alloys. As a consequence, the TiNbZrTa and TiNbZrAl alloys can be considered as potential candidates for biomedical applications.

The need for structural materials in temporary implant applications has grown in the recent years; materials that provide short – term structural support and which can be reabsorbed into the body after healing are being sought. These are materials that are biocompatible and biodegradable. These constitute a novel class of bioactive biomaterials which are expected to support the healing process of a diseased tissue and to degrade thereafter. Magnesium alloys attracted great attention as a new kind of degradable biomaterial. Mg shows great promise as a potential biocompat ible and biodegradable material in biomedical applications where it has gained the interest of researchers in the field. Biodegradable and bioabsorbable magnesium – based alloys provide a number of benefits over traditional permanent implants. There are however some disadvantages to the use of Mg alloys, one of the most critical being the release of hydrogen and alkalinization resulted from the corrosion of Mg. In connection to these drawbacks, a possible solution could be finding alloying elements which would contribute to the reduction of the corrosion rate in the human body. Studies show that a promising alloy for Mg, could be Calcium - a major component of the human bone and also an essential element in the chemical composition of cells. The present paper shall focus on the elaboration of Mg-Ca alloys, respectively Mg0,63Ca to Mg0,8 5 Ca, in the form of bars. These bars were obtained by cast in an inert atmosphere in the presence of argon, in order to be analyzed as biodegradable orthopedic implants. The structure of the alloy has been studied through SEM analyses, X-Ray diffraction, and EDAX to determine the chemical composition, as well as the distribution of elements in the structure. The main desiderate is finding an alloy which would have a minimum healing period postsurgery, pathophysiology and toxicology and a promising degradation behavior.

Stainless steels, titanium and titanium alloys are the most widely used artificial surgical biomaterials for a long time. These alloys with non-degradability properties present long-term adverse effects or stress shielding and require a second surgery for a complete healing. The ongoing scientific research to avoid this problem found a new kind of biocompatible alloys for implants made of biodegradable materials witch should be used as alternative. Among the various biodegradable materials, magnesium alloys have unique biodegradability properties in the physiological environment, have stimulatory effects on new bone formation and have an elastic modulus similar to that of human bone. Roentgen structural analysis was used to detail the global chemical composition analysis, especially the analysis to determine the phase-pick sites characteristic diffraction and crystallographic orientation parameters Miller constituent phases. On studied alloys Mg and Mg2Ca type compounds with different crystallographic orientations were identified. The results obtained on the Mg-Ca and Mg-Ca-Si systems will be correlated with results from previous tests and analyses, to finally obtain an alloy with biodegradability that may be controlled.