Electrochemical corrosion behavior and mechanical properties of Ti-Ag biomedical alloys obtained by two powder metallurgy processing routes.

Titanium is frequently used as a biomaterial and the importance of Ti-Ag alloys has increased thanks to the antibacterial behavior of silver. In this study, Ti-Ag alloys (5, 10 and 15 wt% Ag) were obtained by two different powder metallurgy routes: blended elemental (BE) and mechanical alloying (MA). The influence of the powder mixture methodology on both microstructure and electrochemical behavior was analyzed. Powders were compacted at 600 and 900 MPa, respectively, and sintered at high vacuum for 3 h at 950 °C. The obtained Ti-Ag alloys were microstructurally characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD), and mechanically tested by hardness and bending tests. Electrochemical tests were run using a three-electrode cell in an artificial Fusayama saliva solution. Open-Circuit Potential (OCP), polarization curves, potentiostatic tests and Electrochemical Impedance Spectroscopy (EIS) techniques were employed to evaluate the corrosion resistance of the studied Ti-Ag alloys. The initial characteristics of powders before sintering and after blend/alloying modified the electrochemical behavior of the Ti-Ag-sintered alloys and were determined. The samples obtained with the BE powders better resisted corrosion than the MA samples, and this behavior was directly related to the quantity and distribution of intermetallic Ti2Ag. A large quantity of intermetallics present on both the edge and inside grains reduced the corrosion resistance of TiAg alloys.

Influence of the fabrication process and fluoride content on the tribocorrosion behaviour of Ti6Al4V biomedical alloy in artificial saliva.

Titanium and its alloys are widely used as dental implants due to their low density, excellent biocompatibility, mechanical properties and corrosion resistance. However, during their lifetime Ti6Al4V biomedical alloys are subjected to different mechanical actions (i.e., sliding or fretting), thus resulting in a tribocorrosion system, which is an irreversible material degradation process due to the combined effect of corrosion and wear. In this study, the tribo-electrochemical behavior of cast and sintered (by powder metallurgy) Ti6Al4V alloy in artificial human saliva solution without and with fluoride additions of 100ppm and 1000ppm and in an average industrial mouth wash solution with a 112ppm fluoride content have been investigated by different electrochemical techniques. The same tribocorrosion mechanisms were found in the cast and sintered titanium alloys, although slightly different wear debris behavior was observed. At low applied passive potentials, wear rates are similar to those obtained under equilibrium conditions (Open Circuit Potential). There exists a critical fluoride concentration above which corrosion and tribocorrosion rates increase.

Response of three types of cast posts and cores to static loading.

OBJECTIVE: An analysis is made of the influence of continuous compression loading on different types of cast posts and cores and its effects on the crowns and teeth. METHOD AND MATERIALS: Thirty extracted maxillary canines were prepared and divided into three groups (n = 10) according to the type of cast posts and cores used for restoration: chrome-nickel alloy, acetalic resin, and IPS-Empress porcelain. Metallic cast crowns were luted onto the cores. The specimens were evaluated with an Instron testing machine at an angulation of 45 degrees and a forward speed of 0.5 mm/min. After testing, the specimens were sectioned along the axis and examined under x40 magnification. RESULTS: Mean load resistance of the restorations until fracture was 2,120 N, 1,491 N, and 2,139 N in the chrome-nickel, IPS-Empress ceramic, and acetalic resin groups, respectively. CONCLUSION: Significant differences in resistance were observed between metal and porcelain and between resin and porcelain. Microscopically, the apical portion was found to be most affected by fracture and compromised the teeth subjected to chrome-nickel restorations. The metal cast posts and cores exhibited different angulations, while the ceramic restorations showed cracks. The acetalic resin cast posts and cores presented no fractures.