Dental amalgam mercury

Because the two major sources of mercury body burden include dietary intake and intake from dental amalgams, mercury is present at low concentrations in a variety of human tissues. Mercury has been detected in blood, urine, human milk, and hair in individuals in the general population. Inhalation of... 

Mackert JR. 1987. Factors affecting estimation of dental amalgam mercury exposure from measurements of mercury vapour levels in intra-oral and expired air. J Dent Res 66 1775-1780. 

Dental amalgam Mercury, silver, tin, copper, zinc Dental fillings... 

Occupational allergic contact dermatitis to metallic mercury is rare and is mainly seen among dental personnel (Goh and Ng 1988 Ancona et al. 1982 Kanerva et al. 1993). The majority of positive patch-test reactions to mercury and to mercury compounds are related to non-occupational exposure, e.g., dental amalgam, mercury from broken thermometers, thio-mersal in vaccines, and contact lens cleaning solutions. 

Dentistry. Mercury is used in dental amalgams for fillings in teeth (see Dental materials). Dental uses have accounted for 2—4% of total U.S. mercury consumption since 1980 and generally 3—6% before that time (3). Dental amalgams used to fill cavities in teeth are approximately 50% mercury by weight. Dental use of mercury can be expected to continue to decrease, in part because of more effective cavity prevention as well as development and increasing use of alternative dental materials such as plastics and ceramics, and increasing awareness of the environmental and health effects of mercury. 

Dental amalgams, mainly silver—tin—mercury alloys, have been used as fillings for many years (see Dental MATERIALS). The most common alloy contains 12 wt % tin. 

There have been numerous reports of possible allergic reactions to mercury and mercury salts and to the mercury, silver and copper in dental amalgam as well as to amalgam corrosion products Studies of the release of mercury by amalgams into distilled water, saline and artificial saliva tend to be conflicting and contradictory but, overall, the data indicate that mercury release drops with time due to film formation and is less than the acceptable daily intake for mercury in food . Further, while metallic mercury can sensitise, sensitisation of patients to mercury by dental amalgam appears to be a rare occurrence. Nevertheless, there is a growing trend to develop polymer-based posterior restorative materials in order to eliminate the use of mercury in dentistry. 

Okabe, T. Mercury in the Structure of Dental Amalgam , Dental Materials, 3, 1-8 (1987)... 

Dental amalgam, a solid solution of silver and tin in mercury, is used for filling tooth cavities. Two of the reduction half-reactions that the filling can undergo are... 

Human intake of total mercury from the diet normally ranges between 7 and 16 pg daily (Schumacher et al. 1994 Richardson et al. 1995). Fish consumption accounts for much of this exposure in the form of methylmercury 27% of the intake, and 40% of the absorbed dose. Intake of inorganic mercury arises primarily from foods other than fish, and is estimated at 1.8 pg daily with 0.18 pg absorbed daily (Richardson etal. 1995). In certain areas of India, blood mercury concentrations of people who ate fish were three to four times higher than non-fish eaters (Srinivasen and Mahajan 1989). In some countries, mercury in dental amalgams accounts for 2.8 pg daily, equivalent to as much as 36% of the total mercury intake and 42% of the absorbed dose (USPHS... 

Elemental mercury is used industrially in electric lamps and switches, gauges and controls (e.g. thermometers, barometers, thermostats), battery production, nuclear weapons production, and the specialty chemical industry, including the production of caustic soda. Because elemental mercury has a high affinity for gold and silver, it has been, and continues to be, used in precious metal extraction from ore. Elemental mercury has been used for over one hundred years in mercury-silver amalgam preparations to repair dental caries. Mercury continues to be used in folk remedies and in certain cultural practices, with unknown public health implications. 

Mercury was used to cure the felt used in hats, and workers developed the characteristic signs of mercury vapor toxicity. Acute exposure to high concentrations of mercury vapor causes respiratory distress, which can be fatal. The symptoms of chronic exposure to mercury vapor include personality changes such as excitability, depression, memory loss, fine motor tremor that can become progressively worse, gingivitis, and hallucination. There is some mercury inhalation exposure from dental amalgam, but for most people there are no health-related effects. Metallic mercury is very poorly absorbed from the intestine, thus it is much better to swallow the mercury from a thermometer than inhale it (see chapter on mercury). 

With more than 200 million dental restorations performed each year, the importance of using a restorative material which is both safe and durable should not be underestimated. Currently, dental amalgam is used in the vast majority of these restorations however, recent scrutiny of mercury levels in dental amalgam and the desire for tooth colored restorations have led to increasing demand for polymeric dental composites. Polymeric composites, generally composed of a multimethacrylate and a ceramic glass filler, have primarily been used for anterior tooth restorations in which color matching is imperative for aesthetic purposes. 

Mercury is mined predominantly as HgS in cinnabar ore and is then converted commercially to a variety of chemical forms. Key industrial and commercial applications of mercury are found in the electrolytic production of chlorine and caustic soda the manufacture of electrical equipment, thermometers, and other instruments fluorescent lamps dental amalgam and artisanal gold production. Use in pharmaceuticals and in biocides has declined substantially in recent years, but occasional use in antiseptics and folk medicines is still encountered. Thimerosal, an organomercurial preservative that is metabolized in part to ethylmercury, has been removed from almost all the vaccines in which it was formerly present. Environmental exposure to mercury from the burning of fossil fuels, or the bioaccumulation of methylmercury in fish, remains a concern in some regions of the world. Low-level exposure to mercury released from dental amalgam fillings occurs, but systemic toxicity from this source has not been established. 

Parsons et al.66 reported on the determination of total mercury as a toxic element in urine at the trace level using ICP-MS. The main sources of exposure in the human body are inhalation of Hg vapour released from dental amalgams and the consumption of fish species that accumulate, for example, methyl mercury (MeHg). 

Today we no longer tinker with alchemy, and mercury has long been abandoned by hat manufacturers. But this doesn t mean that we don t still have to contend with mercury exposure. The chemical industry employs the metal as a catalyst, and mercury is an integral part of the process used to produce chlorine and lye (sodium hydroxide) from salt. It is also found in electrical switches, dental amalgams, batteries, detonators, and, of course, thermometers. 

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