Neste trabalho estudou-se a influência da adsorção da proteína mucina nas propriedades de superfície e na corrosão da amálgama dentária rica em cobre Tytin®. Diferentes concentrações da mucina, numa solução de saliva artificial inorgânica, de alta concentração iónica, foram estudadas para tempos de imersão de 4 horas e tempos de imersão mais longos até 96 horas. As técnicas utilizadas foram de potencial em circuito aberto e a sua variação com o tempo, curvas de polarização e espectroscopia de impedância electroquímica. Verificou-se a adsorção da mucina na superfície da amálgama assim como o seu papel na prevenção da formação de uma camada de óxido passivo.

In this work the influence of adsorption of mucin protein on the surface properties and on the corrosion behaviour of the high-copper dental amalgam Tytin® has been studied. Different concentrations of mucin, in a solution of an inorganic, artificial saliva of high ionic concentration, were studied for immersion times of 4 hours and for longer immersion times up to 96 hours. Techniques used were open circuit potential and its variation with time, polarisation curves and electrochemical impedance spectroscopy. Evidence was found for the adsorption of mucin on the amalgam surface and also for its role in the prevention of the formation of a passive oxide layer.

Neste trabalho avaliou-se a resistência à corrosão em solução salina das fases presentes na microestrutura de amálgamas dentários comerciais: gama1-Ag2Hg3, o eutético Ag-Cu e gama2-Sn7-8Hg, empregando-se técnicas eletroquímicas de potencial a circuito aberto com o tempo, de polarização potenciodinâmica e de espectroscopia de impedância eletroquímica. As ligas metálicas em estudo já foram caracterizadas em um trabalho prévio, por meio de microscopia eletrônica de varredura e difratometria de raios X. A resistência à corrosão se origina da formação de filmes passivos na superfície metálica e parece estar determinada pela natureza rugosa e porosa das superfícies.

In this work, the corrosion resistance behavior of three of their phases presents in dental amalgam has been investigated: gamma1-Ag2Hg3 (the matrix phase in the microstructure), gamma2-Sn7-8Hg (the phase most susceptible to corrosion in the oral cavity, according to the literature) and Ag-Cu eutectic (the component of the more modern powder alloys, the objective being to reduce the quantity of gamma2-Sn7-8Hg formed during the amalgamation and in this way increase its corrosion resistance). Electrochemical measurements were carried out in 0,9% aqueous sodium chloride in order to simulate the aggressivity of the oral cavity, using open circuit potential measurements, polarization curves and electrochemical impedance. The corrosion resistance exhibited by alloys can be associated with formation of a corrosion layer and seems to be dominated by the presence of a porous layer in the surface.

Perfluoro and sulfonated ion-exchange polymers are recognized as a very useful material for various mechanistic studies and applications in electrochemistry. These polymers are characterized by high equivalent weights and by a low number of ion-exchange sites interposed between long organic chains. The solubility enables a preparation of stable polyelectrolyte films on the electrode surface. Examples of the determination of trace metals and organic componds in real environmental samples are presented.