Does Amalgam Affect the Immune System? A Controversial Issue (Part 1 of 2)

Abstract

Although in use for more than 150 years, dental amalgam has been questioned 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 products in swallowed saliva, and direct absorption into the blood from the oral cavity. Dental amalgam fillings are the most important source of mercury exposure in the general population. Local, and in some instances, systemic hypersensitivity reactions to dental amalgam metals, especially mercury, occur at a low frequency among amalgam bearers. Experimental and clinical data strongly indicate that these and other subclinical systemic adverse immunological reactions to dental amalgam metals 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 resistant individuals, including persons with alleged symptoms due to dental amalgam fillings, where many of the individuals are likely to suffer from conditions with no proven immunological background such as multiple chemical sensitivity syndrome. Intensified studies should be performed 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 lower the threshold for adverse immunological reactions, since recent studies have shown that the metals in alloy, especially silver, may induce autoimmunity in genetically susceptible mice.

Renal Effects of Dental Amalgam in Children: The New England Children’s Amalgam Trial

“…Moreover, high exposure may cause membranous glomerulonephritis with nephrotic syndrome, in industry (Tubbs et al 1982) as well as in the general population (Oliveira et al 1987). Within groups with the same exposure, only some people are affected, and increased susceptibility may be associated with HLA phenotype (Enestrom and Hultman 1995). This is also true for rare mercury hypersensitivity reactions in children (Clarkson and Magos 2006; Counter and Buchanan 2004; Weinstein and Bernstein 2003).…”

“…At lower exposure levels, albumin excretion has generally not been increased (Barregard et al 1997; Buchet et al 1980; Roels et al 1985). In rare cases, high mercury exposure may cause immune-complex mediated glomerulonephritis and nephrotic syndrome (Enestrom and Hultman 1995; Tubbs et al 1982), and animal models have been developed for mercury-induced autoimmunity (Nielsen and Hultman 2002; Pollard et al 2005). In children too, renal effects of mercury exposure occur (Counter and Buchanan 2004).…”

Psychological, Allergic, and Toxicological Aspects of Patients with Amalgam-Related Complaints

“…They interpret their complaints as early symptoms of mercury intoxication or as mercury allergy [1, 2]. …”

Mechanisms of immunosensitization to metals (IUPAC Technical Report)

“…The major source of exposure to inorganic Hg today is probably through its use in dental amalgams [55], although it is still used in preservatives such as thiomersal (e.g., for preservation of protein solutions). Whether the occurrence in amalgams is of any serious toxicological consequence remains very controversial; whether it can lead to sensitization is only somewhat less so [55]. Contact with Hg salts such as the chloride or ammonium chloride commonly causes hypersensitivity [56], though occupational contact dermatitis is considered rare [1].…”