Placental transfer of mercury in pregnant rats which received dental amalgam restorations

Metal component of dental restorations and fixed prostheses in the oral cavity of 43 cases of adults aged 55 years or older in forensic autopsy

Characterization of the metal component of dental restorations and fixed prostheses is useful for the treatment of dental metal allergies and personal identification. This study aimed to describe the composition of metal elements in dental restorations and fixed prostheses in the oral cavity of 43 cadavers of Japanese adults aged 55 years or older in forensic autopsies conducted at a university. In this study, Ag-Pd-Au alloys were most frequently detected, and the percentage of Ni alloys was smaller than that reported in patients with dental metal allergies. Furthermore, alloys containing other elements, such as Fe or Hg, were also detected in some cases.

Contamination of breast milk with lead, mercury, arsenic, and cadmium in Iran: a systematic review and meta-analysis

Breast milk is a complete food for the development of the newborn, but it can also be an important route for environmental pollutants transmission to the infants. This study was aimed to evaluate the status of heavy metals including lead (Pb), mercury (Hg), cadmium (Cd) and arsenic (As) in the breast milk of Iranian mothers. The international databases including Scopus, PubMed, Web of Science and the Persian electronic databases including Scientific Information Database, IranMedex and Magiran were examined to find relevant articles published until July 2021. A total of 23 studies examined the levels of toxic metals in Iranian breast milk samples. According to the findings, the pooled average concentrations (µg/L) of Pb, Cd, Hg and As were 25.61, 2.40, 1.29 and 1.16, respectively. The concentration of Hg and Pb in colostrum milk was more than twice of mature milk. The Hg mean concentration in the breast milk of mothers with at least one amalgam-filled tooth was approximately three times that of mothers without amalgam-filled teeth. Risk assessment analysis indicated that the intake of Pb and Hg by infants through breastfeeding can be considered a health concern in Iran. It seems necessary to reduce the Pb exposure of pregnant and lactating women in Iran. However, more extensive studies are needed to clarify the toxic metals' exposure status of infants through breast milk in other parts of the country.

Mercury speciation in meconium and associated factors

Meconium is formed early in gestation and it is normally not excreted until after birth. Thus it may provide a longer and cumulative record of exposure to mercury (Hg). The present study aims to speciate Hg in meconium samples (N = 488) from Slovenian and Croatian new-borns prenatally exposed to low levels of methyl-Hg (MeHg) from maternal seafood intake and to Hg⁰ from maternal dental amalgam fillings. We had complete data of total Hg (THg) and MeHg in meconium and THg in maternal hair (MH), while THg and MeHg in maternal blood (MB) were available only for Croatian mothers. Personal data namely maternal seafood intake, age, pre-pregnancy BMI, parity, smoking, estimated gestational age at birth, sex, and birth weight were available for the majority of participants, except the number of dental amalgams which was in most cases missing for Croatian mothers. The median THg concentration in meconium was 11.1 (range: 0.41-375.2) ng/g and inorganic Hg (Hg(II)) presented 98.8% (range: 82%-100%, CV: 2%) of THg. We observed significant correlation between meconium and MH Hg levels, with the highest correlation between hair THg and meconium MeHg. Correlation analysis including MB (available only for Croatian population) showed a significant positive correlation between THg in meconium and THg in MB (R_s = 0.642). Additionally, MeHg from MB was correlated with MeHg in meconium (R_s = 0.898), while the correlation between Hg(II) in MB and meconium was positive, but not significant. Maternal seafood intake was significantly correlated with meconium MeHg (R_s = 0.498) and Hg(II) (R_s = 0.201). Multiple linear regression (performed on the Slovenian population, N = 143) confirmed a positive association between meconium MeHg and seafood intake. Furthermore, meconium Hg(II) was positively associated with the number of maternal dental amalgam fillings, but linear regression models did not confirm correlation between seafood intake and meconium Hg(II) levels. We assume that Hg⁰ released from maternal dental amalgam fillings and MeHg from seafood intake were both transported through the placental barrier and portioned between different foetal compartments including meconium. Weak correlation between maternal seafood intake and Hg(II) levels in meconium suggests that there is certain evidence of MeHg demethylation. However, because this correlation was not confirmed by the multiple regression, MeHg demethylation during prenatal life cannot be neither confirmed nor excluded. Further investigations at higher level of exposure are needed to confirm this observations. We can conclude that meconium is a suitable biomarker for MeHg and Hg⁰ exposure during pregnancy. However, comparability of the results reported in meconium in different studies is hindered by a lack of standardized sampling protocols, storage, and analysis.

Exposure to mercury and human reproductive health: A systematic review

BACKGROUND

Evidences from human and animal studies suggest that reproductive function may be affected by mercury. The aim of this review was to explore the mercury influence on human fertility.

METHODS

A systematic search was made in PubMED for papers published between 1975-2017, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Increased mercury levels were associated with infertility or subfertility status. Further, infertile subjects with unexplained infertility showed higher levels of mercury in hair, blood and urine than fertile ones. Mercury exposure induced sperm DNA damage and abnormal sperm morphology and motility. Additionally, mercury levels were related with higher incidence of menstrual and hormonal disorders and increased rates of adverse reproductive outcomes.

CONCLUSIONS

Our review showed that mercury negatively impacts human reproduction, affecting the reproductive and endocrine systems in both male and female. However, the molecular mechanisms underlying the mercury-associated decline on fertility remains unknown.

Effect of dental amalgam on gene expression profiles in rat cerebrum, cerebellum, liver and kidney

Dental amalgam is a source of exposure to elemental mercury vapor in the general population. The aim of this study was to elucidate the effect of elemental mercury vapor exposure from dental amalgam restorations on gene expression profiles. Out of 26,962 rat genes, mercury vapor was found to increase the expression of 1 gene (Atp1b3) and decrease the expression of 1 gene (Tap1) in the cerebrum, increase the expression of 1 gene (Dnaja2) in the cerebellum, increase the expression of 2 genes (Actb and Timm23) and decrease the expression of 1 gene (Spink3) in the liver, increase the expression of 2 genes (RT1-Bb and Mgat5) and decrease the expression of 6 genes (Tnfaip8, Rara, Slc2a4, Wdr12, Pias4 and Timm13) in the kidney.

The dental amalgam toxicity fear: a myth or actuality

Amalgam has been used in dentistry since about 150 years and is still being used due to its low cost, ease of application, strength, durability, and bacteriostatic effect. When aesthetics is not a concern it can be used in individuals of all ages, in stress bearing areas, foundation for cast-metal and ceramic restorations and poor oral hygiene conditions. Besides all, it has other advantages like if placed under ideal conditions, it is more durable and long lasting and least technique sensitive of all restorative materials, but, concern has been raised that amalgam causes mercury toxicity. Mercury is found in the earth's crust and is ubiquitous in the environment, so even without amalgam restorations everyone is exposed to small but measurable amount of mercury in blood and urine. Dental amalgam restorations may raise these levels slightly, but this has no practical or clinical significance. The main exposure to mercury from dental amalgam occurs during placement or removal of restoration in the tooth. Once the reaction is complete less amount of mercury is released, and that is far below the current health standard. Though amalgam is capable of producing delayed hypersensitivity reactions in some individuals, if the recommended mercury hygiene procedures are followed the risks of adverse health effects could be minimized. For this review the electronic databases and PubMed were used as data sources and have been evaluated to produce the facts regarding amalgam's safety and toxicity.

Endocrine disruptor & nutritional effects of heavy metals in ovarian hyperstimulation

PURPOSE

There is increasing concern that environmental chemicals have a direct effect on fertility. Heavy metals such as mercury have been shown to affect various organ systems in humans including nervous system and skin, however they could also act as endocrine disrupting chemicals adversely affecting fertility. Metals such as zinc and selenium are essential micronutrients with diverse functions that may be important for reproductive outcomes. We measured mercury, zinc and selenium levels in the hair, a reliable reflection of long term environmental exposure and dietary status, to correlate with the outcome of ovarian hyperstimulation for in vitro fertilisation (IVF) treatment.

METHODS

We analysed the hair of 30 subfertile women for mercury, zinc and selenium using inductively coupled mass spectrometry. Each woman underwent one cycle of IVF treatment. Correlation between the levels of these trace metals and treatment outcomes was investigated.

RESULTS

Thirty women were recruited with mean (±SD) age of 32.7(4.4) years and BMI of 25.4(5.0)kg/m(2). Hair mercury concentration showed a negative correlation with oocyte yield (p < 0.05,βcoefficient 0.38) and follicle number (p = 0.03,β coefficient0.19) after ovarian stimulation. Zinc and selenium levels in hair correlated positively with oocyte yield after ovarian stimulation (p < 0.05,β coefficient0.15) and (p = 0.03,β coefficient0.21) respectively. Selenium levels in hair correlated significantly with follicle number following stimulation (p = 0.04, βcoefficient0.22). There was no correlation between mercury, zinc and selenium in hair and their corresponding serum levels.

CONCLUSION

These data suggest that mercury had a deleterious effect whilst there was a positive effect for zinc and selenium in the ovarian response to gonadotrophin therapy for IVF. Hair analysis offers a novel method of investigating the impact of long-term exposure to endocrine disruptors and nutritional status on reproductive outcomes.

Is dental amalgam safe for humans? The opinion of the scientific committee of the European Commission

It was claimed by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR)) in a report to the EU-Commission that "....no risks of adverse systemic effects exist and the current use of dental amalgam does not pose a risk of systemic disease..." [1, available from: http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_016.pdf].SCENIHR disregarded the toxicology of mercury and did not include most important scientific studies in their review. But the real scientific data show that:(a) Dental amalgam is by far the main source of human total mercury body burden. This is proven by autopsy studies which found 2-12 times more mercury in body tissues of individuals with dental amalgam. Autopsy studies are the most valuable and most important studies for examining the amalgam-caused mercury body burden.(b) These autopsy studies have shown consistently that many individuals with amalgam have toxic levels of mercury in their brains or kidneys.(c) There is no correlation between mercury levels in blood or urine, and the levels in body tissues or the severity of clinical symptoms. SCENIHR only relied on levels in urine or blood.(d) The half-life of mercury in the brain can last from several years to decades, thus mercury accumulates over time of amalgam exposure in body tissues to toxic levels. However, SCENIHR state that the half-life of mercury in the body is only "20-90 days".(e) Mercury vapor is about ten times more toxic than lead on human neurons and with synergistic toxicity to other metals.(f) Most studies cited by SCENIHR which conclude that amalgam fillings are safe have severe methodical flaws.

Perinatal lead and mercury exposure in Austria

OBJECTIVE

The heavy metals lead (Pb) and mercury (Hg) are ubiquitous environmental pollutants with high neurotoxic potential. We aimed to compare perinatal Pb and Hg concentrations and to explore the potential association between Pb and Hg exposure and newborn anthropometry.

STUDY DESIGN

Pregnant women were recruited in 2005 at the General Hospital Vienna for participation in this longitudinal study. Pb and Hg concentrations were measured in maternal blood and hair, placenta, cord blood, meconium, and breast milk of 53 mother-child pairs by CV-AAS, GF-AAS, and HPLC-CV-ICPMS. We conducted bivariate analyses and categorical regression analysis (CATREG) to evaluate the determinants of Pb and Hg exposure, and of infant anthropometry.

RESULTS

Median Pb and total Hg contents were low, i.e., 25 μg/L (maternal blood-Pb), 13 μg/L (cord blood-Pb), 0.7 μg/L (maternal blood-Hg), and 1.1 μg/L (cord blood-Hg). Hg levels in maternal and fetal tissues were frequently correlated (r>0.3, P<0.05, respectively). Regarding Pb, only maternal blood and cord blood concentrations correlated (P=0.043). Cord blood levels indicated higher Hg exposure but lower Pb exposure relative to maternal blood contents. Adjusted CATREG models indicated the significant predictors of birth length (placenta-Pb, gestational length, meconium-Pb), birth weight (placenta-Pb, gestational length, maternal blood-Pb), and head circumference (maternal education, maternal height). Besides one significant correlation between maternal hair Hg and birth length, the mercury levels were not associated with newborn anthropometry.

CONCLUSIONS

Our data implicate that different modes of action may exist for placentar transfer of Pb and Hg as well as that low Pb exposure levels can result in lower birth weight. The findings related to newborn anthropometry need to be confirmed by the examination of larger study groups. Further research is needed to clarify the mechanisms of Pb and Hg transfer via the placenta, and to explore how prenatal Pb exposure is related to intrauterine growth.

Methylmercury exposure and health effects from rice and fish consumption: a review

Methylmercury (MeHg) is highly toxic, and its principal target tissue in humans is the nervous system, which has made MeHg intoxication a public health concern for many decades. The general population is primarily exposed to MeHg through consumption of contaminated fish and marine mammals, but recent studies have reported high levels of MeHg in rice and confirmed that in China the main human exposure to MeHg is related to frequent rice consumption in mercury (Hg) polluted areas. This article reviews the progress in the research on MeHg accumulation in rice, human exposure and health effects, and nutrient and co-contaminant interactions. Compared with fish, rice is of poor nutritional quality and lacks specific micronutrients identified as having health benefits (e.g., n-3 long chain polyunsaturated fatty acid, selenium, essential amino acids). The effects of these nutrients on the toxicity of MeHg should be better addressed in future epidemiologic and clinical studies. More emphasis should be given to assessing the health effects of low level MeHg exposure in the long term, with appropriate recommendations, as needed, to reduce MeHg exposure in the rice-eating population.

Comments on the Article “The Toxicology of Mercury and Its Chemical Compounds” by Clarkson and Magos (2006)

Clarkson and Magos (2006) provide their perspectives on the toxicology of mercury vapor and dental amalgam. As scientists who are involved in preparing a German federal guideline regarding dental amalgam, we welcome additional scientific data on this issue. However, Clarkson and Magos do not present all the relevant studies in their review. The additional data provided here show that: (a) Dental amalgam is the main source of human total mercury body burden, because individuals with amalgam have 2-12 times more mercury in their body tissues compared to individuals without amalgam; (b) there is not necessarily a correlation between mercury levels in blood, urine, or hair and in body tissues, and none of the parameters correlate with severity of symptoms; (c) the half-life of mercury deposits in brain and bone tissues could last from several years to decades, and thus mercury accumulates over time of exposure; (d) mercury, in particular mercury vapor, is known to be the most toxic nonradioactive element, and is toxic even in very low doses, and (e) some studies which conclude that amalgam fillings are safe for human beings have important methodogical flaws. Therefore, they have no value for assessing the safety of amalgam.

Maternal amalgam dental fillings as the source of mercury exposure in developing fetus and newborn

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.

Maternal dental history, child's birth outcome and early cognitive development

Prenatal exposure to high levels of mercury, radiation and inflammation have been associated with adverse reproductive outcomes such as increases in preterm delivery, low birthweight and delayed neurodevelopment. Few data are available to evaluate the potential effects of prenatal low-level exposure to these factors as may occur during dental care. We evaluated maternal dental history prior to and during pregnancy in relation to birth outcomes and early communicative development among offspring in a large cohort (n = 7375) of British children born in 1991-92. Dental history was assessed by questionnaire. The child's communicative development was assessed using the MacArthur Communicative Development Inventory at 15 months of age. Total mercury was measured in umbilical cord tissue for a subset of the children. Overall, dental care, including amalgam fillings, was not associated with birth outcomes or language development. Having X-rays taken during pregnancy was not associated with birthweight measured continuously (b = 14.7, P = 0.4), but was associated with slightly increased odds of having a term, low-birthweight baby (OR 1.9, [95% confidence interval 1.0, 3.4]). More detailed evaluation of the potential adverse effects of elective dental treatment during pregnancy, particularly dental X-rays, may be warranted.

Mercury exposure and public health

Mercury is a metal that is a liquid at room temperature. Mercury has a long and interesting history deriving from its use in medicine and industry, with the resultant toxicity produced. In high enough doses, all forms of mercury can produce toxicity. The most devastating tragedies related to mercury toxicity in recent history include Minamata Bay and Niagata, Japan in the 1950s, and Iraq in the 1970s. More recent mercury toxicity issues include the extreme toxicity of the dimethylmercury compound noted in 1998, the possible toxicity related to dental amalgams, and the disproved relationship between vaccines and autism related to the presence of the mercury-containing preservative, thimerosal.

Methylmercury exposure and health effects in humans: a worldwide concern

The paper builds on existing literature, highlighting current understanding and identifying unresolved issues about MeHg exposure, health effects, and risk assessment, and concludes with a consensus statement. Methylmercury is a potent toxin, bioaccumulated and concentrated through the aquatic food chain, placing at risk people, throughout the globe and across the socioeconomic spectrum, who consume predatory fish or for whom fish is a dietary mainstay. Methylmercury developmental neurotoxicity has constituted the basis for risk assessments and public health policies. Despite gaps in our knowledge on new bioindicators of exposure, factors that influence MeHg uptake and toxicity, toxicokinetics, neurologic and cardiovascular effects in adult populations, and the nutritional benefits and risks from the large number of marine and freshwater fish and fish-eating species, the panel concluded that to preserve human health, all efforts need to be made to reduce and eliminate sources of exposure.

The toxicology of mercury and its chemical compounds

This review covers the toxicology of mercury and its compounds. Special attention is paid to those forms of mercury of current public health concern. Human exposure to the vapor of metallic mercury dates back to antiquity but continues today in occupational settings and from dental amalgam. Health risks from methylmercury in edible tissues of fish have been the subject of several large epidemiological investigations and continue to be the subject of intense debate. Ethylmercury in the form of a preservative, thimerosal, added to certain vaccines, is the most recent form of mercury that has become a public health concern. The review leads to general discussion of evolutionary aspects of mercury, protective and toxic mechanisms, and ends on a note that mercury is still an "element of mystery."

The Potential Adverse Health Effects of Dental Amalgam

There is significant public concern about the potential health effects of exposure to mercury vapour (Hg(0)) released from dental amalgam restorations. The purpose of this article is to provide information about the toxicokinetics of Hg(0), evaluate the findings from the recent scientific and medical literature, and identify research gaps that when filled may definitively support or refute the hypothesis that dental amalgam causes adverse health effects. Dental amalgam is a widely used restorative dental material that was introduced over 150 years ago. Most standard dental amalgam formulations contain approximately 50% elemental mercury. Experimental evidence consistently demonstrates that Hg(0) is released from dental amalgam restorations and is absorbed by the human body. Numerous studies report positive correlations between the number of dental amalgam restorations or surfaces and urine mercury concentrations in non-occupationally exposed individuals. Although of public concern, it is currently unclear what adverse health effects are caused by the levels of Hg(0) released from this restoration material. Historically, studies of occupationally exposed individuals have provided consistent information about the relationship between exposure to Hg(0) and adverse effects reflecting both nervous system and renal dysfunction. Workers are usually exposed to substantially higher Hg(0) levels than individuals with dental amalgam restorations and are typically exposed 8 hours per day for 20-30 years, whereas persons with dental amalgam restorations are exposed 24 hours per day over some portion of a lifetime. This review has uncovered no convincing evidence pointing to any adverse health effects that are attributable to dental amalgam restorations besides hypersensitivity in some individuals.

Mercury in the environment: effect on health and reproduction

Mercury is a heavy metal that is found naturally in the environment in various forms. Human activity can release mercury into the air, water, and soil. Mercury is also released into the environment after its conversion to methylmercury by bacteria. Mercury was once used in medicine, but the medicinal aspect changed because of its devastating poisoning effect on humans and animals. Today, mercury is one of the most potent neurotoxins known, having a number of adverse health effects in animals and humans. As the sources of mercury are many, the general population is exposed to mercury in day-to-day life, in occupational settings, and in cases of accidental exposure. In addition, ignorance about the use of mercury in cosmetics and religious materials has opened an additional source of exposure. Therefore, making people aware of mercury's effects on health, its sources of entry into the environment, and its chelating remedies becomes a necessity so that strategies can be adopted to minimize use and exposure.

Mercury exposure in children: a review

Exposure to toxic mercury (Hg) is a growing health hazard throughout the world today. Recent studies show that mercury exposure may occur in the environment, and increasingly in occupational and domestic settings. Children are particularly vulnerable to Hg intoxication, which may lead to impairment of the developing central nervous system, as well as pulmonary and nephrotic damage. Several sources of toxic Hg exposure in children have been reported in biomedical literature: (1) methylmercury, the most widespread source of Hg exposure, is most commonly the result of consumption of contaminated foods, primarily fish; (2) ethylmercury, which has been the subject of recent scientific inquiry in relation to the controversial pediatric vaccine preservative thimerosal; (3) elemental Hg vapor exposure through accidents and occupational and ritualistic practices; (4) inorganic Hg through the use of topical Hg-based skin creams and in infant teething powders; (5) metallic Hg in dental amalgams, which release Hg vapors, and Hg2+ in tissues. This review examines recent epidemiological studies of methylmercury exposure in children. Reports of elemental Hg vapor exposure in children through accidents and occupational practices, and the more recent observations of the increasing use of elemental Hg for magico-religious purposes in urban communities are also discussed. Studies of inorganic Hg exposure from the widespread use of topical beauty creams and teething powders, and fetal/neonatal Hg exposure from maternal dental amalgam fillings are reviewed. Considerable attention was given in this review to pediatric methylmercury exposure and neurodevelopment because it is the most thoroughly investigated Hg species. Each source of Hg exposure is reviewed in relation to specific pediatric health effects, particularly subtle neurodevelopmental disorders.

A 7-year prospective quasi-experimental study of the effects of removing dental amalgam in 76 self-referred patients compared with 146 controls

BACKGROUND

Dental amalgam has been suggested to cause long-term physical and mental problems. Claims that removal of the amalgam may lead to dramatic improvements in health have not been tested empirically in controlled studies with a long follow-up period.

PURPOSE

To investigate the long-term effects of removal of dental amalgam on physical and mental symptoms in self-referred patients who complained of multiple somatic and mental symptoms attributed to dental amalgam fillings.

METHODS

In a quasi experimental study, changes in the mental and physical symptoms in 76 patients who had their dental amalgam removed 7 years ago were compared with changes in symptoms among patients with known chronic medical disorders seen in alternative (n=51) and ordinary (n=51) medical family practices and noncomplaining patients with similar amounts of dental amalgam fillings (n=44) seen in an ordinary dental practice. The assessments included written self-reports, a 131-item somatic symptom checklist, Eysenck Personality Questionnaire (EPQ), the General Health Questionnaire (GHQ) and Toronto Alexithymia Scale (TAS).

RESULTS

Subjects who removed their dental amalgam reported reduced physical and mental symptom load compared to status prior to removal, but only to a level comparable with that reported by the other groups with chronic medical disorders. The dental control group consistently reported lower symptom load during the whole period. In a hierarchical three-step regression model, pretreatment physical symptom load (P<.01), age (P<.10) and removal of dental amalgam (ns) predicted 26% of the variance in posttreatment physical symptom load.

CONCLUSION

In a self-referred group of subjects with health complaints attributed to dental amalgam who remove their dental amalgam, the symptom load at follow-up corresponds to the level seen in chronic medical disorders despite the strong implicit placebo effect of the present quasi-experimental design. The finding does not support the hypothesis that removal of dental amalgam will reduce health complaints to normal levels and seriously questions the hypothesis that dental amalgam is an important cause of distress and health complaints.

Effect of amalgam fillings on the mercury concentration in human amniotic fluid

BACKGROUND

Methyl mercury (MeHg) and metallic Hg are well known as neurotoxic agents. Dental amalgam contributes significantly to elemental Hg vapour exposure in the general population. There is little information about Hg concentration in human amniotic fluid (AF) of pregnant women and its potential toxic effect on the fetuses.

OBJECTIVE

Primary to assess the relationship between the presence of detectable mercury (Hg) concentration in human AF, number and surface areas of amalgam fillings of pregnant women; secondary to analyse their obstetric history and perinatal complications.

METHODS

Seventy-two pregnant women took part in this prospective study. One dentist recorded the dental status, presence, number and surface areas of amalgam fillings. Total Hg concentration in AF was determined in digested samples using automatic cold vapour atomic absorption equipment. The detection limit of Hg in AF, determined from blank readings, was 0.08 ng/ml. To estimate the dependence of the explanatory variables (such as number and surface areas of amalgam fillings, fish consumption, presence of liver or neurological diseases and smoking habits) on mercury concentration several linear regression models were built up. Stepwise logistic regression procedures were running on total sample and on patients with at least one amalgam filling (Positive Filling group = PF). Principal component analysis (PCA) provided two factors, which explained for more the 60% of the variance among the variables.

RESULTS

The overall mean Hg concentration in AF among all patients was 0.37+/-0.49 ng/ml. Nineteen (26.4%) women had a Hg concentration <0.08 ng/ml (Hg negative group). In 53 (73.6%) patients, with a concentration > or = 0.08 ng/ml (Hg positive group), the mean value of Hg was 0.49+/-0.52 ng/ml. The average number of amalgam fillings was 2.26 +/- 3.19 in the Hg negative group and 5.32+/-3.03 in the Hg positive group (ANOVA one-way p=0.04). A dependence of mercury concentration on number of amalgam fillings (p=0.03), surface area of the amalgam fillings (p=0.04) and fish consumption (p=0.04) was observed but not at a significant level. In stepwise logistic procedure the number of amalgam fillings gave a contribution to the model (p=0.04), although null value was included in the confidence intervals. We observed no statistically significant differences (chi2 test) among the patients with a Hg concentration <0.08 ng/ml (n=19) and those with a concentration > or = 0.08 (n=53) with regard to obstetric history and perinatal complications.

CONCLUSIONS

Number and surface areas of amalgam fillings influenced positively Hg concentration in AF but not at a significant level. Moreover Hg levels detected in AF were low and no adverse outcomes were observed through pregnancies and in the newborns.