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PubMed1993

Dentin as a possible bio-epidemiological measure of exposure to mercury.

The subtle human health effects from prolonged exposure to small amounts of mercury vapor are unknown. It has been difficult to study possible effects of low-dose exposure for lack of a good measure of long-term exposure. Current methods which use blood, urine, hair, and nails reliably measure only recent exposures. Long-term exposure to lead has been measured using levels found in human dentin. The purpose of this study was to determine whether mercury also accumulates in dentin. In this study, dentin from 16 human teeth, all without dental amalgam restorations, was analyzed by thermal neutron activation analysis. The teeth were selected from people with and without dental mercury amalgam restorations elsewhere in their dentitions. Mercury was found in amounts up to 5.9 ppm. While the highest mercury level was from a sample from someone who had dental amalgam restorations elsewhere in their dentition, the second highest was from someone who had no amalgam restorations. Also, a sample which was not used for any statistical comparisons but which was analyzed because the tooth contained an amalgam restoration had one of the lowest levels of mercury. These results, while inconclusive due to a small sample size, suggest that inorganic mercury vapor is a relatively small contributor to the overall body burden of mercury.

Adolescent↗
PubMed1996

[Amalgam allergy--diagnosis and consequences].

Allergy to dental amalgam is rare--in contrast to Press reports and public opinion. Whereas sensitivity to one or more mercury salts is quite frequently detected in the patch test, it is seldom of clinical relevance. In this report we define the limited indications for performing an allergy test, describe the exact test criteria and delineate the consequences of a positive test result. A critical appraisal of the result is essential in order to avoid unnecessary procedures which are expensive and far from being effective, may even be potentially dangerous.

Dental Amalgam↗
PubMed1998

Cytotoxicity of root perforation repair materials.

The cytotoxicity of restorative dental materials must be investigated to ensure a safe biological response. The MTS assay, a valid and reliable measure of cell viability based on the mitochondrial activity of cultured cells, was used to evaluate the affects on human periodontal ligament (PDL) cells of two resin-modified glass ionomer cements (R-M GICs) (Fuji Duet and Fuji II LC, GC America, Chicago, IL) and one dental amalgam (Contour, Caulk, York, PA)-all suggested materials for root perforation repair. Twelve 4 x 6 mm cylinders of each material were fabricated and placed in 5 ml of alpha-minimum essential medium supplemented with 100 micrograms/ml of penicillin, 50 micrograms/ml of gentamicin, and 5% fetal bovine serum for 24, 48, and 72 h (n = 3). One hundred microliters of eluate was transferred to triplicate wells containing PDL cells previously plated at a density of 10,000 cells/well in a 96-well plate, and incubated for 24 h at 37 degrees C with 5% carbon dioxide. alpha-Minimum essential medium with supplements provided baseline data. Optical density at 490 nm, directly proportional to the number of viable cells, was determined according to manufacturer instructions. Analysis of variance was used to detect differences between treatments and Tukey's HSD (p < 0.05) to detect for differences between group means. Results demonstrated that both material and time affected cell viability (p < 0.0001), with amalgam eluate significantly inhibitory on cell viability at 24 h, compared with control and the two other tested materials. At 48 and 72 h, all three materials exhibited a similar slightly inhibitory effect on the cell viability. Use of resin-modified glass ionomer cement as a root perforation repair material initially (< 24 h) may result in a more favorable response by PDL cells than the tested dental amalgam.

Adult↗
PubMedDate not supplied

[Factors influencing the survival of amalgam restoration in Bangkok metropolitan school children].

The purpose of this study was to find out the factors influenced on the survival of amalgam dental restoration. The study population was the amalgam restoration of 726 molar teeth, 3 restoration types, cavity class I, class I other surface and class I compound, of Bangkok Metropolitan school children aged 6-12 years. The data showed how the survival of restoration placed in teeth varied with the restoration aged ranging 6-30 months. The result indicated that there were 48.10% of broken filling and 19.42% of secondary caries. The rate of broken filling was significantly related to the child age at the time of treatment, the restoration age, the surface texture of the restoration and the restoration type (p less than 0.01). As for the rate of secondary caries, there were significant correlation with the surface texture of the filling, the restoration type and the factor "broken filling" (p less than 0.01). By means of the linear multiple regression, it told us explicitly about the magnitude of the relation that the surface texture of the filling was the major influential factor which could predict the variance of broken filling about 18.29% while the broken filling was also the major influential factor which could predict the variance of secondary caries about 7.93%.

Age Factors↗
PubMed1982

Margin adaptation of dispersion and traditional amalgams with reference to plasticity: a clinical comparison.

Margin adaptation of dental amalgam restorations made from traditional vs. dispersion-type alloy was compared by clinical evaluation with the reference to plasticity of the mix at insertion. Also, variations in sealing properties were assessed for precondensed and not-precondensed amalgam mixes of both alloys. The data presented confirm the clinical superiority of amalgam made from dispersed type alloy. A higher plasticity tended to result in less margin deterioration for amalgams of the traditional type alloy. In vitro leakage with the dispersion type amalgam far exceeded that of the traditional amalgam.

Chemical Phenomena↗
PubMed1986

Corrosion of dental alloys in vitro by differential oxygen concentration.

The corrosion of a conventional and a high Cu dental amalgam, a Cu-Zn dental alloy, and pure silver (control) were studied in vitro under conditions of differential oxygenation, resembling a partially covered dental filling. The experimental method enabled the simultaneous recording of separate pH changes at anordic and cathodic areas and of the corrosion current generated; the corrosion products formed and the corroded alloys were examined by powder X-ray diffraction, optical and scanning electron microscopy, and EDAX elemental analysis. Marked anodic pH drops and cathodic pH rises were seen which, with the total electric change integrated from the recordings, formed the basis for a qualitative evaluation (electrochemical reaction schemes) and a quantitative evaluation (amounts of metal corroded) of the progress of corrosion. The corrosion products found were SnO2, ZnSn(OH)6, and Cu2O of the amalgams, and Zn5(OH)8Cl2 of the Cu-Zn alloy; twice as much tin corroded from the conventional as from the high Cu amalgam, and zinc corroded selectively from the Cu-Zn alloy. These findings were substantiated by the microscopic and EDAX observations.

Corrosion↗
PubMedDate not supplied

[Immunologic effects of exposure to low levels of inorganic mercury].

OBJECTIVE: The immune system is a target for the toxic effects of inorganic mercury, both in humans and animals. In humans it has been observed that occupational and environmental exposure to inorganic mercury may cause both clinical (autoimmunity, hypersensitivity) and subclinical effects (cellular and humoral immunologic variable modifications). To obtain a better definition of these effects with respect to the exposure levels, a multicentre study was performed on 117 workers exposed to very low doses of inorganic mercury and 172 subjects from the general population of the same geographical area with environmental exposure to mercury from dental amalgams and dietary fish intake. RESULTS: The white blood cell count was included in the normality range for all subjects and there was no difference between exposed and non exposed subjects. The immunologic variables studied showed an increase of the CD4+ and CD8+ number in exposed workers compared to non-exposed subjects, with a statistically significance only for CD4+, while no difference was observed regarding CD4+, CD8+, NK+ percentage and CD4+/CD8+ ratio. A significative decrease of serum IL-8 and an inverse correlation between serum levels of this cytokine and HgU were observed in exposed workers compared to non exposed subjects. No association between immunologic variables and both dental amalgams and dietary fish intake was found in subjects not occupationally exposed to inorganic mercury. DISCUSSION: The decrease in IL-8 serum levels observed in exposed workers might suggest an immunosuppressive effect of occupational exposure to very low doses of inorganic mercury. This result suggests the need to revise of current HgU BEI after further definition of its prognostic significance.

Adult↗
PubMed2002

Assessment of reference values for mercury in urine: the results of an Italian polycentric study.

The results of a polycentric study to assess the reference values of urinary mercury (U-Hg) in four Italian cities are presented. A total of 383 subjects were selected on the basis of standardised criteria by a questionnaire on personal habits, lifestyle, occupational or non-occupational exposure to Hg, medical history, number and area of dental amalgams. U-Hg was determined by hydride generation atomic absorption method (HG-AAS), with a detection limit of 0.5 microg/l and by flow injection (FI) inductively coupled plasma mass spectrometry (ICP-MS), with a detection limit of 0.03 microg/l. The median value of U-Hg, determined by HG-AAS, was 0.78 microg/g creatinine (0.75 for males and 0.83 for females), with 5 degrees and 95 degrees percentiles, respectively, of 0.17 and 3.66 microg/g creatinine. When determined by FI ICP-MS, the median value was 0.79 microg/g creatinine (0.77 for males and 0.79 for females) with 5 degrees and 95 degrees percentiles of, respectively, 0.12 and 5.02 microg/g creatinine. Among the independent variables, city of origin, area of dental amalgams, fish intake and tobacco smoking significantly influenced the U-Hg levels. The U-Hg reference values from this survey are lower than those from other recent investigations, probably due to characteristics and selection of the examined individuals and to the strict control of pre-analytical and analytical factors of variability.

Adult↗
PubMedDate not supplied

[Introduction: scope and purpose of the multicenter project " Assessment of effects due to low doses in inorganic mercury following environmental and occupational exposure: human and in vitro studies on specific toxicity mechanisms"].

The principal aims of the project financed by the Italian Ministry of University and Scientific and Technological Research were: to verify if at the current limit values early biological effects can be demonstrated; to identify the levels of internal dose that can cause early effects; to evaluate the non-occupational factors that can contribute to the levels of internal dose. In particular, the mercury intake derived from dental amalgams and fish consumption was considered. The internal dose was measured with the traditional biological indicators (urinary and blood mercury) and with the speciation of a large percentage of biological samples by ICP-MS. The central nervous system, neuroendocrine function, kidney and the immune system were considered as target organs and were examined using previously standardized indicators of effects. Two groups of subjects were included in the study: workers with occupational exposure to inorganic mercury in different industrial settings and control subjects identified from the general population. The first group was characterized by an exposure level to inorganic mercury clearly below the current limit values; whereas the HgU levels of a relevant number of control subjects were similar to those measured in the exposed subjects. The in vitro studies covered several issues: the percutaneous absorption of mercury using skin derived from human post-mortem samples in a standardized model; the release of the metal from dental amalgams in different physiological conditions of the oral cavity; the effects of increasing doses of mercury chloride on tubular renal cells. The project was realized with the cooperation of seven Research Units from six Italian Universities. Researchers belonging to Departments of Occupational Medicine, Industrial Hygiene, General Pathology, Biochemistry, Odontology, and Biostatistics were involved to achieve a multidisciplinary approach. The results of this research project are described and discussed in the following papers.

Absorption↗
PubMed2001

Metallothionein in human gingival amalgam tattoos.

Amalgam tattoos occur when small particles of dental amalgam, composed largely of silver (Ag) and mercury (Hg), are inadvertently implanted into oral soft tissues during dental procedures. Metallothioneins (MTs) are ubiquitous, low molecular weight, cysteine-rich, metal-binding proteins that are inducible by many agents including metals and may be involved in the detoxification of toxic metals such as Hg. In this study, the correlation between MT expression and amalgam tattoos in human gingiva was investigated using energy-dispersive X-ray microanalysis (EDX) and immunohistochemical techniques. Light microscopically, amalgam tattoos presented as either fine granular particles or larger discrete opaque globular particles in connective tissues. EDX revealed the smaller particles to be silver sulphide (Ag(2)S), while the larger particles exhibited a shell of Ag(2)S that contained irregularly distributed masses of Ag and Hg. Particles of tin (Sn) were also found. No MT staining was observed in collagen, fibroblasts or blood vessels in areas exhibiting abundant amounts of embedded fine granular Ag(2)S particles. Blood vessels exhibiting relatively few amalgam particles stained positively for MT. Cells with the morphological features of histiocytes located directly adjacent to larger pieces of amalgam showed intense MT staining. These results indicate that amalgam tattoos contain no Hg or free Ag except in large globular pieces of amalgam, which still contain Hg and which induce MT expression in adjacent histiocytes. This suggests that Hg leaching from impacted dental amalgam particles induces MT, while residual Ag(2)S and Sn particles do not. MT may therefore act to reduce Hg exposure in patients with amalgam tattoos.

Blood Vessels↗
PubMedDate not supplied

In vitro corrosion behavior and microstructure examination of a gallium-based restorative.

Concerns of mercury toxicity have led to the development of gallium-based restorative materials to replace dental amalgam. A new gallium-based dental restorative, Galloy, was compared with a high-copper amalgam, Permite, for anodic polarization behavior in deoxygenated Ringer's solution and by immersion testing in normal Ringer's solution at 37 degrees C. Corrosion products were analyzed using energy dispersive X-ray spectrometry and transmission electron diffraction. The data from both sources were consistent with the presence of alpha-Ga2O3 and SnO2 as the primary corrosion products of Galloy. Anodic polarization behavior of Galloy- and Permite-coupled specimens suggests that coupling Galloy with the more noble Permite amalgam may cause accelerated electrochemical corrosion and that Galloy is more corrosion prone than Permite.

Corrosion↗
PubMed2004

Understanding the mercury reduction issue: the impact of mercury on the environment and human health.

Mercury has been used in both medicine and dentistry for centuries. Recent media attention regarding the increased levels of mercury in dietary fish, high levels of mercury in air emissions, and conjecture that certain diseases may be caused by mercury exposure has increased public awareness of the potential adverse health effects of high doses of mercury. Dentistry has been criticized for its continued use of mercury in dental amalgam for both public health and environmental reasons. To address these concerns, dental professionals should understand the impact of the various levels and types of mercury on the environment and human health. Mercury is unique in its ability to form amalgams with other metals. Dental amalgam--consisting of silver, copper, tin, and mercury--has been used as a safe, stable, and cost-effective restorative material for more than 150 years. As a result of this use, the dental profession has been confronted by the public on two separate health issues concerning the mercury content in amalgam. The first issue is whether the mercury amalgamated with the various metals to create dental restorations poses a health issue for patients. The second is whether the scraps associated with amalgam placement and the removal of amalgam restorations poses environmental hazards which may eventually have an impact on human health. Despite the lack of scientific evidence for such hazards, there is growing pressure for the dental profession to address these health issues. In this article, the toxicology of mercury will be reviewed and the impact of amalgam on health and the environment will be examined.

Animals↗
PubMed1986

The release, tissue distribution and excretion of mercury from experimental amalgam tattoos.

Following the subcutaneous implantation of powdered dental amalgam in guinea pigs, there was an initial extrusion of material from the healing implantation wounds. Longer-term release of mercury from the lesions was demonstrated by linear regression analysis of the mercury contents of implant sites removed after time periods of up to 2 years. Raised mercury levels were detected in the blood, bile, kidneys, liver, spleen and lungs of implanted animals; by far the highest concentrations were found in the renal cortex. Mercury was excreted with the urine and, to a lesser extent, the faeces. The pattern of mercury redistribution resembled that seen following chronic exposure to mercuric compounds.

Animals↗
PubMed1995

Oral lichenoid lesions, mercury hypersensitivity and combined hypersensitivity to mercury and other metals: histologically-proven reproduction of the reaction by patch testing with metal salts.

We report 11 patients seen between 1991 and 1994 with oral lichenoid lesions (OLL). In 10 cases, there was contact with dental amalgam fillings, and in patient no. 10 with both amalgam restorations and a gold crown. The last patient had, in addition to her OLL, lichen planus of the skin and genital mucosa. In 5 cases, combined sensitization to mercury and other metal salts, particularly gold sodium thiosulfate (GST) and palladium chloride (PDC), was observed. In 10 patients, the lesions considerably improved or totally cleared within 1 to 9 months of replacement of restoration materials. Histological examination of biopsies from the test sites of amalgam, mercuric chloride, GST and PDC, taken 10 or 17 days after application of patch tests, showed lichenoid changes in 7 patients with at least 1 of the allergens. As at least 2 patients had inflammatory lesions of the oral mucosa related to both amalgam and gold restorations, combined sensitization to inorganic and organic mercury derivatives, GST and, in 1 case, PDC, a "dental restoration metal intolerance syndrome" is proposed.

Adult↗
PubMedDate not supplied

Mercury resistance among clinical isolates of Escherichia coli.

The use of organomercurials in liquid detergents and disinfectants promoted resistance to mercury among bacteria. Dental amalgam and industries using mercury are the main source of human exposure to mercury vapor. Release of mercury from dental amalgam contributes to the enrichment of the intestinal flora with mercury resistance plasmids which may be associated with antibiotic resistance. The aim of our study was to evaluate the frequency of E. coli strains resistant to mercury and other antimicrobial agents currently used in therapy. The bacterial mercury and ampicillin, cephalexin, cefotaxime, gentamicin, tetracycline and chloramphenicol resistance was tested against 363 E. coli strains obtained from faeces and urine between 1999-2000. According to the guidelines suggested by NCCLS (1998), minimum inhibitory concentrations (MICs) were determined on Mueller-Hinton agar, using the dilution technique with an inoculum of about 10(5) CFU. The MICs were read after 18 h incubation at 37 degrees C as the lowest concentration that inhibited the development of visible growth. Plasmids in enterobacteria may carry genes encoding resistance to both mercury and antibiotics. Among the tested E. coli strains, mercury resistance rose to 29.2%. Mercury resistance in E. coli is significantly linked to multiresistance to antimicrobial agents. Between 91.5-23.6 of mercury chloride resistant isolates were also resistant to the tested antibiotics. The increased use of non antibiotic antimicrobial agents is a possible selection factor for antibiotic-resistant strains in clinical and domestic environments.

Anti-Bacterial Agents↗
PubMed1999

[Effect of manifacturing technology on the resistance to corrosion of amalgam fillings and speed of mercury emission].

The study investigates the influence of the various manufacturing technological alternatives of a given alloy on the corrosion properties, as well as it evaluates the quantity of mercury release from the amalgam filling having the same alloy. The resistance of dental amalgams to corrosion is the function of their precious metal (mercury and silver) content. The release speed of the mercury depends on the original condition of the alloy. The highest values were given for filing amalgam. When investigating the composition of amalgam mainly in spherical form, a significant decrease could be here determined.

Corrosion↗