Influence of amalgam fillings on Hg levels and total antioxidant activity in plasma of healthy donors

Evaluation of amalgam-related retinal neurotoxicity with optical coherence tomography findings

PURPOSE

To evaluate the neurotoxic effect of amalgam dental fillings on plasma mercury (Hg) levels and retino-choroidal layers measured by spectral domain optical coherence tomography (SD-OCT).

MATERIALS/METHODS

Study participants included 56 cases with amalgam dental fillings and 44 healthy controls. All participants were examined in terms of detailed ophthalmic examination, oral examination, and body mass index (BMI). The measurement of retinal layers and choroid was performed using SD-OCT. Venous blood samples were collected and blood Hg levels were measured using cold vapor atomic absorption spectrometric analysis. Correlations between SD-OCT measurement results and blood Hg levels were analyzed.

RESULTS

There were no differences between groups in terms of age, sex, or BMI. The mean blood Hg level was 2.76 ± 1.21 µg/L in the amalgam group and 2.06 ± 1.15 µg/L in the control group ( p = 0.04). The Hg/BMI ratio was 0.12 ± 0.06 kg/m² in the amalgam group and 0.09 ± 0.05 kg/m² in the control group ( p = 0.01). Reduced volumes of ganglion cell layer and inner plexiform layer were observed in the amalgam group when compared with the control group ( p < 0.05).

CONCLUSION

Amalgam dental fillings can cause retinal neurotoxicity. SD-OCT can be useful for evaluating amalgam-related retinal neurotoxicity.

Mercury exposure and risks from dental amalgam in the US population, post-2000

Dental amalgam is 50% metallic mercury (Hg) by weight and Hg vapour continuously evolves from in-place dental amalgam, causing increased Hg content with increasing amalgam load in urine, faeces, exhaled breath, saliva, blood, and various organs and tissues including the kidney, pituitary gland, liver, and brain. The Hg content also increases with maternal amalgam load in amniotic fluid, placenta, cord blood, meconium, various foetal tissues including liver, kidney and brain, in colostrum and breast milk. Based on 2001 to 2004 population statistics, 181.1 million Americans carry a grand total of 1.46 billion restored teeth. Children as young as 26 months were recorded as having restored teeth. Past dental practice and recently available data indicate that the majority of these restorations are composed of dental amalgam. Employing recent US population-based statistics on body weight and the frequency of dentally restored tooth surfaces, and recent research on the incremental increase in urinary Hg concentration per amalgam-filled tooth surface, estimates of Hg exposure from amalgam fillings were determined for 5 age groups of the US population. Three specific exposure scenarios were considered, each scenario incrementally reducing the number of tooth surfaces assumed to be restored with amalgam. Based on the least conservative of the scenarios evaluated, it was estimated that some 67.2 million Americans would exceed the Hg dose associated with the reference exposure level (REL) of 0.3 μg/m(3) established by the US Environmental Protection Agency; and 122.3 million Americans would exceed the dose associated with the REL of 0.03 μg/m(3) established by the California Environmental Protection Agency. Exposure estimates are consistent with previous estimates presented by Health Canada in 1995, and amount to 0.2 to 0.4 μg/day per amalgam-filled tooth surface, or 0.5 to 1 μg/day/amalgam-filled tooth, depending on age and other factors.

A dental look at the autistic patient through orofacial pain

Abstract Autism is a neurodevelopmental disorder characterized by impaired social interaction and restricted interests, compromised communication skills, and repetitive patterns of behavior. Both social and behavioral problems, which may include hyperactivity and quick frustration, may hinder the detection of other important pathologies such as orofacial pain. This is aggravated by the invasive nature of oral exploration, which may trigger violent and self-injurious responses, such as temper tantrums and/or head banging, which make the work of professionals extremely difficult during diagnoses, follow-up examinations, and dental treatments. In addition, mercury-containing amalgams used to treat dental caries (the most common form of acute orofacial pain) have been associated with higher rates of severe autism in children. The purpose of this review is to describe the current state of the art regarding the co-occurrence of orofacial pain and autism spectrum disorder, and how these conditions may interrelate clinically and neurobiologically.

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.

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.

The effects of amalgam restorations on plasma mercury levels and total antioxidant activity

OBJECTIVE

This study evaluated the effects of amalgam restorations on plasma mercury levels and total antioxidant activities (TAA).

DESIGN

The study was comprised of 48 subjects ranging in age from 20 to 32 years. Of these, 33 had dental amalgam restorations and 15 had no dental amalgam restorations. In those patients with amalgams, the total number of amalgam restorations and surfaces were counted, and the total and occlusal areas (mm(2)) of restorations were measured using a Counting Measurement Machine. Blood samples were collected from all participants. Plasma mercury levels were measured using an Atomic Absorption Spectrometer and Hydride System, and plasma TAA levels were measured using an Antioxidant Assay Kit. Statistical analysis was performed using the SPSS 10.01 software program. Data was evaluated by t test and correlation analysis.

RESULTS

Plasma mercury (P-Hg) levels were found to be significantly higher in subjects with amalgam restorations when compared to subjects without amalgams (p<0.01); the differences in P-TAA levels between subjects with and without amalgams were not found to be statistically significant (p>0.05). No significant correlations were found between P-Hg concentrations and P-TAA levels (p>0.05). Significant positive correlations were found between P-Hg concentrations and the number of amalgam restorations (p<0.01), number of amalgam surfaces (p<0.05), total amalgam surface area (p<0.05) and amalgam occlusal surface area (p<0.01). However, no significant correlations were found between these parameters and P-TAA (p>0.05).

CONCLUSIONS

The results of our study showed that dental amalgams are a major source of plasma mercury; however, amalgam restorations were not found to have a significant effect on plasma-total antioxidant activities.

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.

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.

Amalgam studies: disregarding basic principles of mercury toxicity

Dental amalgam, which has been used for over 150 years in dental practice, consists of about 50% metallic mercury. Studies on animal and humans show that mercury is continuously released from dental amalgam and absorbed by several body tissues. It is widely accepted that the main source of mercury vapor is dental amalgam and it contributes substantially to mercury load in human body tissues. There is still a controversy about the consequences of this additional mercury exposure from amalgam to human health. Many studies were performed to evaluate possible adverse effects. In this comment, these studies were analyzed with regard to their methodical quality by considering the newest findings on mercury toxicity and metabolism. In sum, a number of studies are methodically flawed drawing inaccurate conclusions as to the safety of dental amalgam.

Temporal variation of blood and hair mercury levels in pregnancy in relation to fish consumption history in a population living along the St. Lawrence River

Fish consumption from the Great Lakes and the St. Lawrence River has been decreasing over the last years due to advisories and increased awareness of the presence of several contaminants. Methylmercury (MeHg), a well-established neurotoxicant even at low levels of exposure, bioaccumulates to differing degrees in various fish species and can have serious adverse effects on the development and functioning of the human central nervous system, especially during prenatal exposure. Most studies on MeHg exposure have focussed on high-level consumers from local fish sources, although mercury (Hg) is also present in fresh, frozen, and canned market fish. Moreover, little information exists on the temporal variation of blood and hair Hg in pregnant women, particularly in populations with low levels of Hg. The aim of the present study was to characterize the temporal variation of Hg during pregnancy and to investigate the relation between fish consumption from various sources prior to and during pregnancy and maternal cord blood and mother's hair Hg levels. We recruited 159 pregnant women from Southwest Quebec through two prenatal clinics of the Quebec Public Health System. All women completed two detailed questionnaires concerning their fish consumption (species and frequency) prior to and during pregnancy. The women also provided blood samples for all three trimesters of pregnancy and hair samples after delivery of up to 9 cm in length. Blood and hair Hg levels were analyzed by cold-vapor atomic-absorption and -fluorescence spectrometry methods, respectively. Results showed that maternal blood and hair Hg levels decreased significantly between the second and third trimesters of pregnancy. However, cord blood Hg was significantly higher than maternal blood at birth. Maternal hair was correlated with Hg blood concentration and was highly predictive of the organic fraction in cord blood. A strong dose relation was observed between the frequency of fish consumption before and during pregnancy and Hg exposure in mothers and newborns. Fish consumption prior to and during pregnancy explained 26% and 20% of cord blood Hg variance, respectively. For this population, detailed multivariate analyses showed that during pregnancy market fish (fresh, canned, and frozen) were more important sources of Hg exposure than were fish from the St. Lawrence River. These results should be taken into account for future advisories and intervention strategies, which should consider Hg levels in different species from all sources in order to maximize the nutritional input from fish and minimize the toxic risk.

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.