The safe and effective use of dental amalgam. 
Case reports in the lay press claim that amalgam restorations may cause a number of local and systemic symptoms.  Several recent scientific reports and reviews maintain that dental amalgam is a safe and effective restorative material.  The advantages of dental amalgam as a restorative material include its ease of handling, diversity in application, physical characteristics and the infrequency of local and systemic biological side effects.  The disadvantages of dental amalgam comprise poor aesthetics, local degradation, occasional allergic responses to some of its components or degradation products, and the toxicity of mercury.  The clinical diagnosis of secondary caries constitutes the main reason for the replacement of amalgam restorations in both dentitions.  Great variations prevail with regard to the longevity of amalgam restorations.  Half of the restorations replaced in permanent teeth are about 8-10 year old, but the range is from 0 to about 40 years.  Restorations needing replacement in deciduous teeth are in service for shorter periods of time than those in permanent teeth.  In a longitudinal study of more than 600 class II amalgam restorations in permanent teeth, only about 6 per cent were replaced after a 6-7 year observation period.  The longevity of amalgam restorations depends on a number of factors, including the quality of the material, its use and manipulation by the dentists and dental assistants and possibly also the oral hygiene of the patient.