Mercury

“BACKGROUND:

Dental assistants help the dentist in preparing material for filling teeth. Amalgam was the filling material mostly commonly used in Norway before 1980, and declined to about 5% of all fillings in 2005. Amalgam is usually an alloy of silver, copper, tin and mercury. Copper amalgam, giving particularly high exposure to mercury was used in Norway until 1994. Metallic mercury is neurotoxic. Few studies of the health of dental assistants exist, despite their exposure to mercury. There are questions about the existence of possible chronic neurological symptoms today within this working group, due to this exposure. The aim of this study was to compare the occurrence of neurological symptoms among dental assistants likely to be exposed to mercury from work with dental filling material, compared to similar health personnel with no such exposure.

METHODS:

All dental assistants still at work and born before 1970 registered in the archives of a trade union in Hordaland county of Norway were invited to participate (response rate 68%, n = 41), as well as a similar number of randomly selected assistant nurses (response rate 87%, n = 64) in the same age group. The participants completed a self-administered, mailed questionnaire, with questions about demographic variables, life-style factors, musculoskeletal, neurological and psychosomatic symptoms (Euroquest).

RESULTS:

The dental assistants reported significant higher occurrence of neurological symptoms; psychosomatic symptoms, problems with memory, concentration, fatigue and sleep disturbance, but not for mood. This was found by analyses of variance, adjusting for age, education, alcohol consumption, smoking and personality traits. For each specific neurological symptom, adjusted logistic regression analyses were performed, showing that these symptoms were mainly from arms, hands, legs and balance organs.

CONCLUSION:

There is a possibility that the higher occurrence of neurological symptoms among the dental assistants may be related to their previous work exposure to mercury amalgam fillings. This should be studied further to assess the clinical importance of the reported symptoms.”

It’s becoming increasing clear that the recent improvements in technology for the nonmercury filling—most commonly the “composite”—have rendered the mercury tooth filling— aka “amalgam”—obsolete. One only has to look at the recent bans on new amalgam placement in Norwegian or Swedish dental patients or elimination of insurance coverage for amalgam restorations in Danish patients to document mercury-free tooth restoratives as a viable substitute. Practically speaking, the age of amalgam is over. “So why do over 60 million mercury tooth fillings still get placed into Americans’ mouths every year? Is it because it is simply cheaper and quicker for your dentists to place an amalgam and they make more money doing so? Is it because, as the expression goes, “you can’t teach an old dog new tricks,” and in some cases dentists are reluctant to change or take the time to master the new techniques for placement of composites? Or is it because the US dental sector, led by the American Dental Association and its state associations, remains in denial that mercury is a neurotoxin — a hazardous material before it is placed in the mouth, and a hazard that releases toxic vapors after it is in the mouth? And could concerns about potential legal liability reinforce this denial? Or finally, is it because dentists are not aware or held accountable to the fact—undisputed by the US EPA since it was presented to the US House subcommittee last fall– that the continued use of amalgam is resulting in the release of upwards of 10 tons—and growing— of mercury into the air and water each year in the U.S. And that at least some of that mercury gets taken up in the fish Americans eat and, in particular, poses the most acute risk to pregnant women and their developing fetus and young children?”

“OBJECTIVE:

To investigate the suitability of measurements of mercury (Hg) concentration as a means of identifying patients with health complaints attributed to dental amalgam.

METHODS:

Hg in erythrocytes, plasma, urine, and saliva was determined in 27 patients complaining about health problems attributed to amalgam, 27 healthy volunteers with amalgam fillings, and 27 healthy amalgam-free volunteers.

RESULTS:

Concentrations of inorganic mercury in blood and of total mercury in urine and saliva differed significantly between individuals with amalgam fillings and amalgam-free volunteers, but not between symptomatic patients and healthy volunteers with amalgam fillings. Urine Hg levels tended to be better correlated with blood than with saliva data. Levels of organic Hg were equal in all groups.

CONCLUSION:

Concentrations of total and inorganic mercury in body fluids do not distinguish between asymptomatic amalgam bearers and those who suffer from a poorly defined syndrome of multiple nonspecific symptoms.”

“Thimerosal is an antiseptic containing 49.5% of ethyl mercury that has been used for years as a preservative in many infant vaccines and in flu vaccines. Thimerosal is an organic mercurial compound used as a preservative in biomedical preparations. In this study, we evaluated the genotoxic effect of thimerosal in cultured human peripheral blood lymphocytes using sister chromatid exchange analysis in culture conditions with and without S9 metabolic activation. This study is the first report investigating the genotoxic effects of thimerosal in cultured human peripheral blood lymphocyte cells using sister chromatid exchange analysis. An analysis of variance test (ANOVA) was performed to evaluate the results. Significant induction of sister chromatid exchanges was seen at concentrations between 0.2 and 0.6 microg/ml of thimerosal compared with negative control. A significant decrease (p<0.001) in mitotic index (MI) and proliferation index (PRI) as well as an increase in SCE frequency (p<0.001) was observed compared with control cultures. Our results indicate the genotoxic and cytotoxic effect of TH in cultured human peripheral blood lymphocytes at tested doses in cultures with/without S9 fraction.”

“Dental mercury-silver amalgam must not be classified in Class II, which would effectively confer “generally regarded as safe” status. It is not safe. The IAOMT position is that amalgam should be banned, removed from the market just as every other mercurial medical device and substance has been. At the very least, it should be placed in Class III, and let the advocates prove that it is safe. We are confident that such proof is not available. Mercurial wound disinfectants are gone, mercurial diuretics are gone, mercury thermometers are gone, and so are all mercurial veterinary substances. There is no magic that makes dental mercury safer than those obsolete products of the past. In this era when the public worries about the mercury they are ingesting through fish consumption, the FDA should do the right thing and ban amalgam dental fillings as the time-release mercury exposure devices they are. ”

“FOREWORD: This document summarizes public health concerns related to a gymnasium floor at a school in Minnesota. It is based on a formal site evaluation prepared by the Minnesota Department of Health (MDH). For a formal site evaluation, a number of steps are necessary:”

“Dental amalgam is a mercury-based filling containing approximately 50% of metallic mercury (Hg(0)). Human placenta does not represent a real barrier to the transport of Hg(0); hence, fetal exposure occurs as a result of maternal exposure to Hg, with possible subsequent neurodevelopmental disabilities in infants. This study represents a substudy of the international NIH-funded project ‘Early Childhood Development and polychlorinated biphenyls Exposure in Slovakia’. The main aim of this analysis was to assess the relationship between maternal dental amalgam fillings and exposure of the developing fetus to Hg. The study subjects were mother-child pairs (N=99). Questionnaires were administered after delivery, and chemical analyses of Hg were performed in the samples of maternal and cord blood using atomic absorption spectrometry with amalgamation technique. The median values of Hg concentrations were 0.63 microg/l (range 0.14-2.9 microg/l) and 0.80 microg/l (range 0.15-2.54 microg/l) for maternal and cord blood, respectively. None of the cord blood Hg concentrations reached the level considered to be hazardous for neurodevelopmental effects in children exposed to Hg in utero (EPA reference dose for Hg of 5.8 microg/l in cord blood). A strong positive correlation between maternal and cord blood Hg levels was found (rho=0.79; P<0.001). Levels of Hg in the cord blood were significantly associated with the number of maternal amalgam fillings (rho=0.46, P<0.001) and with the number of years since the last filling (rho=-0.37, P<0.001); these associations remained significant after adjustment for maternal age and education. Dental amalgam fillings in girls and women of reproductive age should be used with caution, to avoid increased prenatal Hg exposure.”

“Individual risk of developmental neurotoxicity with exposure to environmentally relevant levels of lead and mercury is likely to be determined by genetic susceptibility factors as well as additive interactions with other environmental pollutants, cumulative dose, and the developmental stage of exposure. The apparent increase in autism diagnosis over the last 15 years has enhanced interest in the possibility that an environmental trigger may be required to uncover the genetic liability in some cases of autism. The exquisite sensitivity of the developing brain and immune system to very low levels of lead and mercury give this hypothesis biologic plausibility. Delta aminolevulinic acid dehydratase (ALAD) and coproporphyin oxidase (CPOX) are two enzymes inhibited by low levels of lead and mercury, respectively. Common polymorphisms in these genes have been associated with elevated blood levels of lead and mercury and could potentially increase vulnerability to prenatal and/or postnatal developmental neurotoxicity. To explore this possibility, the frequency of the ALAD2 variant and variants in CPOX-4 and CPOX-5 were evaluated in 450 autistic children and 251 unaffected controls. A significant increase in the frequency of the ALAD2 allele was observed; however, contrary to our hypothesis, the frequency of both CPOX variants was significantly lower among the autistic children. Both lead and mercury induce oxidative stress by depleting the major intracellular antioxidant, glutathione. Among 242 autistic children with the variant ALAD2 allele, significant decreases in plasma glutathione and in the glutathione redox ratio were observed. These results suggest that children with autism who inherit the ALAD2 allele with lower glutathione levels may be at increased risk for lead toxicity during prenatal and postnatal neurodevelopment.”

“This paper provides an overview of the use of dental amalgam, available non-mercury alternative restorative materials, information on amalgam separators, common components of some dental mercury amalgam separator programs, a summary of lessons learned from some existing state and local government programs from around the United States, and recommendations for future action.”

“Any science teacher encouraging students to put mercury in their mouths would be fired for gross negligence and likely prosecuted for endangering the health of a child. Yet dentists do it every day.”