Electrochemical study of endodontic silver cones used in root canal therapy.

In previous studies it was observed that endodontic silver cones placed in fine canals became dislodged as a result of corrosion. To investigate the corrosion of high purity silver, potentiostatic and potentiodynamic electrochemical techniques were used. Triangular potential sweeps made in physiological solutions and human plasma showed similar potential-current relationships. However, in human plasma, peak currents were lower and peak potentials were more anodic than those observed in the physiological solutions. The electron microprobe analysis and the EDAX of the film formed in the biological fluids revealed the presence of silver and chloride and a certain amount of carbon. The addition of small quantities of Na2S to the physiological solutions favoured metal dissolution and promoted the formation of a mixed film of AgCL and Ag2S. According to these results chloride and sulphide anions seem to be particularly aggressive towards the metal surface in implanted silver cones. Precautions to avoid direct contact of the cones with saliva and tissue fluids must be taken. Fractures and discontinuities present in the cement considerably increase the corrosion risks.

Spontaneous adsorption of silver nanoparticles on Ti/TiO2 surfaces. Antibacterial effect on Pseudomonas aeruginosa.

Titanium is a corrosion-resistant and biocompatible material widely used in medical and dental implants. Titanium surfaces, however, are prone to bacterial colonization that could lead to infection, inflammation, and finally to implant failure. Silver nanoparticles (AgNPs) have demonstrated an excellent performance as biocides, and thus their integration to titanium surfaces is an attractive strategy to decrease the risk of implant failure. In this work a simple and efficient method is described to modify Ti/TiO(2) surfaces with citrate-capped AgNPs. These nanoparticles spontaneously adsorb on Ti/TiO(2), forming nanometer-sized aggregates consisting of individual AgNPs that homogeneously cover the surface. The modified AgNP-Ti/TiO(2) surface exhibits a good resistance to colonization by Pseudomonas aeruginosa, a model system for biofilm formation.