Electrochemical Behavior of Alloys for Fixed Partial Denture
The electrochemical behaviors of eight parent alloys and four post-solder alloys used in dental prostheses were specified in a (pH=7.4; (NaCl)=9g/L)-aqueous solution at 37°C. For each alloy, the free potential was followed during two hours, and a cyclic polarization between the cathodic domain and the solvent's oxidation was performed. The gal- vanic corrosion between each parent alloy and its usual post-solder was also studied. The free potentials stay in the immu- nity domain of the alloy's base-elements (precious metals) or in their passivation domain (nickel, chromium). A relatively strong oxidation of the alloys is possible only for high values of applied potential. Corrosion of the noblest alloys is al- most inexistent. It occurs for the nickel-base alloys but it is very slow. Most of the elements present can be oxidized, but only for high potentials which cannot be really achieved by dissolved oxygen. Galvanic corrosion can occur between the parent alloy and the post-solder alloy in some cases. The realization of frameworks for fixed partial denture (FPD) often involves the use of more or less noble metallic alloys and their assemblage by soldering. The latter is called pre-ceramic soldering or post-ceramic soldering, this de- pending on the step of the fabrication of the prostheses at which this soldering is realized. Soldering is well used to correct distortion of the framework which occurs during the casting process (1), to improve the seating accuracy (2) and to correct a possible movement of teeth before prosthesis cementation (3). The solder joint is often the weakest part of a fixed partial denture (4, 5). While some defects can be due to the process of fabrication (6), others can appear during the use of the prosthesis in the mouth, because of corrosion by saliva which can generate additional cavities on alloy sur- face. Indeed, the metallic framework may partly remain exposed to the buccal milieu, notably a part of the parent alloy and the post-ceramic solder which is not covered by ceramic. These are the reasons why the individual behaviors of main alloy of the framework and of the post-solder alloys in contact with saliva need to be better known, as well as the behavior of this parent alloy coupled with its usual post- solder. The purpose of this article is first to specify the separate behaviors of the parent alloy and of the post-ceramic solder, and second to study the possible galvanic corrosion which could be due to the association of the two materials, by using electrochemical techniques. The electrolyte used in this study, is characterized by a NaCl concentration of 9 g/L and
Electrochemical characterisation of dental alloys: its possibilities and limitations
Dental alloys are metallic biomaterials which have a broad variation of composition compared to technical alloys. It is therefore in the interest of patients and technicians to conduct a good assessment of the electrochemical behaviour of dental alloys in order to collect information about their corrosion resistance. The purpose of this work was to demonstrate possibilities and limitations of two electrochemical techniques: the voltammetry of immobilised microparticles (ViMP) onto lead, and cyclic voltammetry measurements with the help of the mini-cell system (MCS). Based on fingerprints obtained from ViMP it was possible to analyse and differentiate the dental alloys. The results obtained by MCS were comparable with ViMP, but give a better understanding of the corrosion behaviour of the materials.
The mark of sexual preference in the interpretation of texts: preface to a homosexual reading.
Since reading is an interaction or confrontation between the reader and the text-an interaction that depends upon the background and perspectives of the reader as well as on the text being read-we can assume that the dynamics of sexuality and sexual object choice will influence how readers ascribe meaning to literary texts. In fact, although other aspects of our identities come into play when we read, sexual identity is unique and central because of the role that it plays in the creation of subjectivity. Specifically, male homosexuality informs and structures the reading of texts. But what does it be a homosexual reader or to effectuate a homosexual reading of a particular text?