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PubMed1990

A study of mercury redistribution, excretion and renal pathology in guinea-pigs implanted with powdered dental amalgam for between 2 and 4 years.

Ten guinea-pigs were implanted subcutaneously with 2 x 25 mg of powdered amalgam for 2, 2.5, 3, 3.5, and 4 years, two animals at each time period. Five animals served as controls. Their diet contained 0.2 micrograms/g selenium (Se). In control animals no detectable mercury (Hg) was present in the liver, urine and faeces and only 0.11-0.18 micrograms/g was present in the kidneys, which were structurally normal. One control animal (3.5 year) had an epidermal tumour. In the implanted animals mean renal cortical Hg reduced from 116.1 micrograms/g at 2 years to 70.2 micrograms/g at 4 years and mean liver Hg ranged from 0.17 to 0.39 micrograms/g. The mean 24-h Hg excretion reduced to close to the detection limit by 45 moths. Proximal tubular cells contained HgSe deposits in lysosomes and nuclei. Renal pathology was seen in only two animals both of which also had abdominal tumours which almost certainly arose spontaneously and probably influenced the development of renal pathology to a major degree.

Animals↗
PubMed1992

Dental amalgam--environmental aspects.

Increasing knowledge about the risk of toxic effects caused by anthropogenic mercury accumulation in ecosystems has resulted in a growing pressure for reduction of the discharge of mercury waste. Consequently, the mercury waste problems of dental clinics have been given increased attention, and restrictions on handling and discharge of contaminated waste have been established in several countries. Major amalgam particles from trituration surplus of those produced during the carving and burnishing of new amalgam restorations are generally collected in coarse filters and sold for refinement. Minor amalgam particles released by production of new fillings or by removal of old restorations partly sediment in tubes and drains. The remaining particles are carried with the waste water stream to the local purifying plant. In Scandinavia, the industrial discharge of mercury-contaminated waste water has been reduced to a minimum. According to recent investigations, dental clinics appear to be responsible for the major amount of mercury collected in the sludge generated in purifying plants. If threshold values for heavy metal content, including mercury, are exceeded, the sludge is not allowed to be recycled as fertilizer. Installation of an approved amalgam-separating apparatus in dental clinics is now mandatory in several countries--for example, Switzerland, Germany, Sweden, and Denmark. Approval of amalgam separators is based on national testing programs, including clinical or laboratory tests demanding 95-99% separating efficiency.

Biological Availability↗
PubMedDate not supplied

[Urinary and blood markers of internal mercury dose in workers from a chlorakali plant and in subjects not occupationally exposed: relation to dental amalgam and fish consumption].

OBJECTIVES: The aim of this paper was both to evaluate the internal dose of Hg in occupationally exposed workers (35 Chloralkali workers) compared to that of non occupationally exposed controls (40 workers of the same plant of Portotorres and 22 residents on the island of Carloforte, usual consumers of local fish, mostly tuna fish with relatively high Hg levels) and to assess the relevance of environmental and individual exposure factors linked to lifestyle, sea fish consumption and amalgam fillings. METHODS: All subjects filled out a questionnaire concerning the working history and lifestyle. The amalgam fillings area was measured by medical inspection using a standardised schedule attached to the questionnaire. Mercury in urine (HgU) was measured in all cases, while in a subgroup of our study total blood mercury (HgB) and its organic and inorganic component were also assessed. Furthermore, for 8 of the Carloforte group mercury in hair was also available. RESULTS: Values of urinary mercury excretion of the Chloralkali workers were significantly higher (median value of 15.4, range 4.8-35.0 micrograms/g creatinine, 94.3% of the cases having values > 5 micrograms/g creatinine) than those observed both among the reference group (median value of 1.9, range 0.4-5.6 micrograms/g creatinine, 12.5% of the cases having values a little greater than 5 micrograms/g creatinine) and among the residents in Carloforte (median value of 6.5, range 1.8-21.5 micrograms/g creatinine, 59.1% of the cases having values > 5 mcg/g creatinine). The HgU values observed in this group were in turn significantly higher than those of the non occupationally exposed workers living near Sassari (p = 0.03). Only in this last group were the HgU concentrations statistically significantly related to the extension of the amalgam fillings area (Pearson r = 0.53, p < 0.01). In the Carloforte group HgU was significantly related to the number of fish meal consumed per week (Pearson r = 0.48, p < 0.02). HgB (median value of 5.9, range 3.4-21.6 micrograms/l) as well as its inorganic component (median value of 2.4, range 1.8-4.6 micrograms/l) were significantly higher in the Chloralkali group compared to the other two groups. In all cases of the Carloforte group the ratio between the organic component and the total HgB was higher than 85%, while this ratio was significantly lower in the other two groups. The relationship between HgU and HgB was statistically significant, considering both total blood mercury and the inorganic and the organic components separately. A statistically significant relationship between the sea fish consumption per week and both total HgB (Pearson r = 0.82) and the organic component in this matrix (Pearson r = 0.84, p < 0.001) was observed among 16 non-occupationally exposed subjects. However, the significant relationship between organic blood mercury and sea fish consumption was almost entirely supported by the data observed in the Carloforte group. Total hair mercury levels analysed in 8 subjects of the Carloforte group were high (median value of 9.6, range 1.4-34.5 micrograms/g) and significantly related to sea fish consumption, and to both the individual Hg urinary excretion (Pearson r = 0.83) and to the organic component of blood mercury (Pearson r = 0.87). CONCLUSIONS: According to several experimental human and animal trials and to some recent studies on methylmercury toxicokinetic models, our results suggest that the organic compounds absorbed by usual sea fish consumption may be partially demethylated, increasing the inorganic Hg concentration in the kidney and consequently its urinary excretion, as was observed in the Carloforte group.

Absorption↗
PubMed2001

Release of mercury from dental amalgam fillings in pregnant rats and distribution of mercury in maternal and fetal tissues.

Mercury vapor released from a single amalgam restoration in pregnant rats and mercury concentrations in maternal and fetal rat tissues were studied. Dental treatment was given on day 2 of pregnancy. Mercury concentration in air sample drawn from the metabolism chamber with the rat was measured serially for 24 h on days 2, 8 and 15 of pregnancy. An average mercury concentration in the air samples from the rats given amalgam restorations was 678.6+/-167.5 ng/day on day 2. The average mercury concentration in the air samples tended to decline as time elapsed but a marked amount (423.2+/-121.5 ng/day) was observed even on day 15. The amount of mercury in the air samples increased 7--20-fold after chewing. The placement of the single amalgam restoration (3.8--5.5 mg in weight) increased the levels of mercury approximately three to 6 times in the maternal brain, liver, lung, placenta and 20 times in the kidneys. The highest mercury concentration among fetal organs was found in the liver, followed by the kidneys and brain. Mercury concentrations in maternal organs and fetal liver were significantly higher than those of the controls, and concentrations in maternal whole blood, erythrocytes and plasma, and in fetal whole blood were also significantly higher. Mercury concentrations in the fetal brain, liver, kidneys and whole blood were lower than those of the maternal tissues.

Air↗
PubMed1996

[Dental care using silver amalgam].

Dental amalgam is the most widely used filling material in dentistry. In our country there are an estimated 40 million amalgam fillings in place. The mercury present in these fillings has caused health concerns over the last 160 years that amalgam has been used in decayed teeth. The fears have always proven to be unjustified and no harmful effects have ever been demonstrated in dental patients. Mercury can be found in several forms. In dentistry, only the metallic form is used, while inorganic and organic compounds are also present in the environment. The metallic form is absorbed in the human body mostly through the lungs. Once mercury reaches toxic levels inside the body, it will interfere with cell metabolism. Most important among the target organs are the brain, the liver and the kidneys. Elimination occur through urine and feces. Mercury is universally found in blood and urine. The concentration depends on absorption by air, water, nutrition, medication (including dental fillings) and occupational hazards. There are four kinds of objectives to dental amalgam: oral galvanism, toxicity, allergenicity and ecological grievances. Disorders from oral galvanism are difficult and delicate to evaluate as the actual currents are very small. Furthermore, no significant difference can be found in current intensity between patients with and without complaints. Finally patients with complaints often present other oral disorders, the treatment of which most often eliminates all complaints that could be attributed to oral galvanism. Toxicity is dose dependent. Industrial safety rules indicate that the amount of mercury absorbed from dental amalgam fillings is far below the safety level. HgB and HgU levels in patients with amalgam fillings are situated well below the acceptable levels. Allergic disorders are observed in patients with amalgam fillings but far less than expected in view of the wide spread use of dental amalgam. The problem of mercury spilling from dental amalgam fillings into the environment will be resolved by strict legislation in the near future. In this context, it can be stated that the use of dental amalgam is safe and justified. Furthermore, it is also advisable as no other material can meet the actual dental needs as efficiently as can dental amalgam.

Corrosion↗
PubMedDate not supplied

Amalgam--Resurrection and redemption. Part 1: the clinical and legal mythology of anti-amalgam.

Dental amalgam has come under attack for its allegedly poor physical properties and clinical performance in addition to its poor appearance. It has been claimed that the American Dental Association has a hidden agenda to protect amalgam and that other countries have banned its use. A literature search revealed that the vast majority of amalgam restorations do not cause fractured cusps or have recurrent caries. Most amalgam restorations have been shown to last longer than resin composite restorations. In addition, the materials and techniques involved in amalgam restorations have vastly improved in recent years. Like resin composite restorations, amalgam restorations can often be repaired. The American Dental Association has no vested interest in protecting amalgam. The use of amalgam has not been banned in any country in the European Union. According to the latest scientific information available, dental amalgam is a remarkably durable and long-lasting restorative material. Although its appearance is unesthetic, its clinical performance and effectiveness are unsurpassed by those of resin composite.

American Dental Association↗
PubMed1999

The failure of amalgam dental restorations due to cyclic fatigue crack growth.

In this study a restored mandibular molar with different Class II amalgam preparations was examined to analyze the potential for restoration failure attributed to cyclic fatigue crack growth. A finite element analysis was used to determine the stress distribution along the cavo-surface margin which results from occlusal loading of each restoration. The cyclic crack growth rate of sub-surface flaws located along the dentinal cavo-surface margin were determined utilizing the Paris law. Based on similarities in material properties and lack of fatigue property data for dental biomaterials, the cyclic fatigue crack growth parameters for engineering ceramics were used to approximate the crack growth behavior. It was found that flaws located within the dentine along the buccal and lingual margins can significantly reduce the fatigue life of restored teeth. Sub-surface cracks as short as 25 microm were found capable of promoting tooth fracture well within 25 years from the time of restoration. Furthermore, cracks longer than 100 microm reduced the fatigue life to less than 5 years. Consequently, sub-surface cracks introduced during cavity preparation with conventional dental burrs may serve as a principal source for premature restoration failure.

Journal Article↗
PubMed1976

Tissue reaction to dispersion alloy amalgam.

Dental amalgam implanted in rat connective tissue is injurious for the first 16 days. At 32 days, the implanted amalgam is tolerated. The increased copper content of Dispersalloy did not evoke a more serious response of the connective tissue than Fine Cut or Spheraloy amalgam.

Animals↗
PubMed1984

Restoration of primary teeth with amalgam.

Dental amalgam used by the dentist as a restorative material should meet the following criteria: (1) a reduced risk of marginal failure with a minimal risk of recurrent caries, (2) resistance to creep and corrosion, and (3) the characteristics for mixing, inserting, and polishing that are optimally duplicated. To achieve these criteria, the optimal amalgam technique includes the use of the following: Rubber dam whenever possible Conservative cavity preparations to offset the amalgam's inherent weak physical properties A high copper alloy combined with the appropriate amount of mercury for optimal plasticity and to reduce susceptibility to creep and corrosion Trituration, precondensation, and condensation methods that are consistently practiced by the dental assistant and dentist A burnishing scheme combined with a subsequent polishing method to complete the final amalgam restoration.

Chemical Phenomena↗
PubMed1994

Mechanical performance of dental amalgam--composite interfaces.

Composite veneering of amalgam is the most aesthetical solution to extensive direct tooth restoration and is applied with success in specific clinical situations. An in-vitro technique has been used to evaluate the mechanical performance of one amalgam bonded to four different composites. The amalgam-composite interfaces were subjected to tensile stress and shear stress at break tests, using dumb-bell and sandwich specimens in a PC-controlled electronic dynamometer equipped with innovative grips. Mean values were higher for tensile stress than for shear stress. Further studies and clinical experimentation will be necessary to explore the question of long-term reliability.

Acrylic Resins↗
PubMed1998

Structure and strength of low-mercury dental amalgams prepared with liquid Hg-47.4% In alloy.

Two low-mercury amalgams: (1) low-copper lathe-cut and (2) high-copper (Tytin) were prepared by amalgamation with liquid Hg-47.4% In alloy. The strength-structure relationship of these amalgams was investigated and compared with standard amalgams (i.e. amalgams prepared with the same powders and pure mercury). The matrix phase of the low-mercury amalgam was found to be depleted of mercury and may be thought of as In4Ag9 compound with some mercury dissolved, indicating that less mercury (compared with standard amalgam) combines with silver, thus producing a strong amalgam matrix. On the other hand, an increase was observed in the consumption of the initial gamma (Ag3Sn)-phase, leading to an increase of the tin released. As a result, the potential of [HgSn]-phase formation in low-mercury amalgams increases. The observed increase in the quantity of gamma2(Sn7-8Hg)-phase in low-copper amalgam, or its appearance in high-copper amalgam (where it is normally absent), contributes to a deterioration in the strength of the investigated amalgam. The conclusion drawn was that low-mercury amalgam may be prepared with liquid Hg-47.4%In alloy but, in order to eliminate gamma2-phase formation, novel and possibly tin-free amalgamable alloys should be developed.

Journal Article↗
PubMed1990

Exercise-induced anaphylaxis: improvement after removal of amalgam in dental caries.

We present a case of exercise-induced anaphylaxis with improvement following the removal of dental amalgam. Although her symptoms were unresponsive to various kinds of therapy until removal of the amalgam, her symptoms related to exercise improved remarkably after the removal. The increase in plasma histamine levels for exercise provocation test also improved. This suggests that sensitivity to metals might cause exercise-induced asthma in some patients.

Anaphylaxis↗
PubMed2001

Activation of oral keratinocytes by mercuric chloride: relevance to dental amalgam-induced oral lichenoid reactions.

BACKGROUND: Despite the benefits of mercury-containing amalgam dental fillings there are growing concerns regarding the potential adverse health effects arising from exposure to mercury released from fillings. In some individuals this process may result in a local lichenoid reaction of the oral mucosa. OBJECTIVES: The aim of this study was to investigate the possibility that mercury salts released from amalgam fillings might act directly on oral keratinocytes to induce changes that could promote the development of such lesions. METHODS: In vitro experiments were performed in which normal oral and cutaneous keratinocytes were cultured in the presence of mercuric chloride (HgCl2). ICAM-1 expression and the release of cytokines was determined by enzyme-linked immunosorbent assay techniques. T-cell binding to HgCl2-pretreated keratinocytes was assessed using a colorimetric method. RESULTS: Subcytotoxic concentrations of HgCl2 induced a concentration-related increase in ICAM-1 expression and consequent T-cell binding on oral, but not cutaneous, keratinocytes. HgCl2 also stimulated the release of low levels of tumour necrosis factor-alpha and interleukin-8 (but not RANTES), and inhibited the release of interleukin-1alpha by oral keratinocytes. CONCLUSIONS: This study provides evidence that oral keratinocytes may play an integral part in initiating the pathogenesis of amalgam-induced lichenoid reactions.

Cell Adhesion↗