Electrochemical action due to short-circuiting of dental alloys. An in vitro and in vivo study.

Metallic materials in the oral cavity cannot be expected to be inert. However, the electrochemical interaction with the environment, may vary considerably. Corrosion of dental metallic materials has been said to cause local, and even general unpleasant effects. Different forms of corrosion and variations in the complex oral milleu make it difficult to estimate and predict the corrosion occurring. Various methods such as the recording of potentials, potential differences and currents have been used to study the corrosion which may occur when metallic restorations or appliances come into contact. However, an improvement should be obtained if data which are more closely related to the ion release due to short-circuiting could be recorded. Calculated currents were related to those directly measured and the knowledge thus obtained was used to design a convenient equipment for clinical registration of the charge transfer between short-circuited restorations or appliances. The equipment was used in a study of patients with disorders/discomfort allegedly caused by corrosion in the oral cavity. Furthermore, the released quantity of tin and the charge transfer between amalgam and gold alloy electrodes were studied both in vitro and clinically. The currents flowing between amalgam and gold alloy electrode couples were compared using different electrolytes. The findings may be summarized as follows: The quantity of tin released in vitro was related to the charge transferred between short-circuited electrodes consisting of a conventional amalgam and a gold alloy and the same tendency could be shown clinically. When electrodes made of a gold alloy and various types of amalgams were short-circuited, the currents recorded were influenced by the composition of the amalgams and of the electrolytes. The equipment constructed admitting measurements of the charge transfer seems to be suitable for an estimation of corrosion due to contacts between metallic restorations/appliances. No differences could be found when a referred group of patients with disorders/discomfort allegedly caused by corrosion of dental metallic materials was compared with a control group of people with roughly the same type and distribution of metallic restorations/appliances when each individual was represented by the highest charge transfer and the total added charge transfers, respectively. Some of the patients' disorders/discomfort can be related to the occurrence of affections and conditions, the treatment of which falls within the scope of the dentist.