DOES AMALGAM AFFECT THE IMMUNE-SYSTEM - A CONTROVERSIAL ISSUE

Although in use for more than 150 years, dental amalgam has been quest ioned more or less vigorously as a dental restoration material due to its alleged health hazard. Humans are exposed to mercury and the other main dental amalgam metals (Ag, Sn, Cu, Zn) via vapour corrosion prod ucts in swallowed saliva, and direct absorption into the blood from th e oral cavity. Dental amalgam fillings are the most important source o f mercury exposure in the general population. Local, and in some insta nces, systemic hypersensitivity reactions to dental amalgam metals, es pecially mercury, occur at a low frequency among amalgam bearers. Expe rimental and clinical data strongly indicate that these and other subc linical systemic adverse immunological reactions to dental amalgam met als in humans will be linked to certain MHC genotypes, and affect only a small number of the exposed individuals. These individuals will be very difficult to detect in a mixed population of susceptible and resi stant individuals, including persons with alleged symptoms due to dent al amalgam fillings, where many of the individuals are likely to suffe r from conditions with no proven immunological background such as mult iple chemical sensitivity syndrome. Intensified studies should be perf ormed to identify such susceptible MHC genotypes, taking advantage of the reported cases of more heavily metal-exposed humans with systemic autoimmune reactions. Further studies will also be needed to ascertain whether the combined exposure to the metals in dental amalgam may low er the threshold for adverse immunological reactions, since recent stu dies have shown that the metals in alloy, especially silver, may induc e autoimmunity in genetically susceptible mice.