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This article provides a view of government reaction in Canada to public concern over the use of dental amalgam. It also addresses the basis of the irrational fears the general public may have regarding the impact of external factors on their health.
Sixty consecutive patients who had undergone replacement of dental amalgam fillings and a protocol of nutritional support and heavy metal detoxification using dimercapto-propanyl-sulfate and neural therapy were surveyed. A questionnaire was mailed to the patients and 42 responded, resulting in a response rate of 70%. The reasons for undergoing treatment were many, ranging from a patient's desire to avoid potential health problems in the future to treatment of serious current disease. Although medical diagnoses were made when possible before treatment, this survey studied only the patients' estimations of their most distressing symptoms and their evaluations of response to treatment. The most common complaints were problems with memory and/or concentration; muscle and/or joint pain; anxiety and insomnia; stomach, bowel, and bladder complaints; depression; food or chemical sensitivities; numbness or tingling; and eye symptoms, in descending order of frequency. The most distressing symptoms were headache and backache, fatigue, and memory and concentration problems. Headache and backache responded best to treatment, but all symptoms showed considerable improvement on average. Of the respondents, 78% reported that they were either satisfied or very satisfied with the results of treatment, and 9.5% reported that they were disappointed.
The literature on the setting mechanisms of dental amalgams made from powders of silver-rich alloys of tin and/or copper has been critically reviewed. In Part 1 of the review, the microstructure and phase content of recently set amalgams are described. The composition, morphology, and location of product phases are emphasized, since these features are clues to the setting reaction. Thus, Part 1 provides the background needed to understand the kinetics of the setting reactions, which is the topic of Part 2 of the review.
The aim of this investigation is the ultrastructural analysis of biopsies of human gingiva pigmented by the metallic deposits from dental amalgam. The size, the nature and the distribution of the particles are studied by light and electron microscopy and by energy dispersive spectrometry (EDS). Fragments and particles of different size and composition are observed. No traces of mercury are detected in any examined samples. In contrast, very fine grains (0.01 to 0.05 microns in diameter) of a silver compound are observed to be preferentially bound to intracellular membranes and to extracellular structural components. Tissue modifications in the gingival epithelium as well as in the connective tissue can accompany the pigmentation phenomenon. The different metabolic pathways of the metals diffusing from the amalgams are discussed.
Divers performing underwater manual metal arc welding/cutting (UMMA) have complained about a metallic taste phenomenon. In several dives with voluntary leakage in their diving suits, potential alterations in dental amalgam were registered when they performed UMMA. Polarization resistance values were obtained for the test amalgam cylinders used and the diver's dental restorations. These values, along with the recorded potential values of the amalgam test cylinders and of the diver's dental restorations, enabled us to calculate the depolarizing current, using the law of Ohm. The current depolarizing the amalgam test cylinder did not differ significantly from the mean intermetallic currents between the dental restorations. The clinical effect of intraoral currents when performing UMMA welding should be regarded as small, whereas considerably higher currents should not be ruled out in an intense cutting situation.
The purpose of the present work was to study the setting of amalgams made from several different commercial alloys by recording the rate of initial mercury consumption, and then to compare the findings with those from other methods of defining the early setting process. The results show that the rate of initial mercury consumption is well correlated with clinicians' classification of the rate of setting of amalgams, but not correlated with mechanical tests like early compressive strength and guillotine setting time used till now in estimating the working time of amalgams. Based on these findings an appropriate method of determining the mercury:alloy proportion and working time of dental amalgams is suggested.
The influence of dental amalgam and heavy metal cations on interleukin-1beta (IL-1beta) expression by peripheral blood mononuclear cells from healthy donors was studied. A marked decrease in the production of IL-1beta was caused by freshly prepared amalgam or amalgam-conditioned culture medium, but not by amalgam aged for 6 weeks. When metal cations were added as salts, Cu(2+), Hg(2+), and Ag(+) at high concentrations (33.3 and 333.3 microM) were highly inhibitory. Among other heavy metal cations, Au(3+), Pt(4+), Ni(2+), Pd(2+), but not Ga(3+) or Sn(2+), inhibited IL-1beta production in a concentration-dependent manner. Flow cytometry studies indicated that Hg(2+) and Ag(+) strongly reduced the percentage of CD14(+) cells containing IL-1beta intracellularly. As shown by Northern blot analysis, Hg(2+) inhibited the level of IL-1beta-specific mRNA by 28% at 3.3 microM and completely at 33.3 microM. Only slight inhibitory effects were induced by Cu(2+) at 33.3 microM. Interestingly, Ag(+) at a concentration of 3.3 microM increased twofold the amount of IL-1beta-specific mRNA. Our data show that IL-1beta production is altered at protein and mRNA levels by components released from fresh amalgam and by other heavy metal cations, suggesting a role of these cations in changes in the cell phenotype and IL-1-mediated cell functions.
OBJECTIVE: It was the objective of this study to determine the magnitude of in vivo galvanic currents produced by simulating electrical contact between occluding metallic restorations, and to examine the influence of restoration age, difference in pre-contact corrosion potentials, and surface area. METHODS: A convenience sample of 106 human subjects was studied. A Ag/AgCl micro-reference electrode and a high impedance voltmeter were used to measure the pre-contact corrosion potentials. Galvanic couples (n = 194) were next formed by simultaneously contacting occluding restorations with gold-plated probe tips for 15 s. The resulting current-time transients were measured with a zero-resistance ammeter and recorded with an electronic data acquisition program. The vast majority of couples measured contained at least one dental amalgam restoration. RESULTS: Galvanic current-time transients were typically characterized by an immediate and rapid rise to a peak current, followed by an exponential decay to a much lower value at 15 s. For couples with a restoration < or = 12 mo old, median peak current and median current at 15 s were 2.26 microA (range 0.24-13.06 microA) and 0.57 microA (range 0.03-6.47 microA), respectively. For couples with a restoration >12 mo old, median peak current and median current at 15 s were 1.40 microA (range 0.24-12.09 microA) and 0.37 microA (range 0.00-3.05 microA), respectively. Couples with fresh amalgams (< or = 6 mo) generally had elevated currents (range 2.56-102.54 microA). SIGNIFICANCE: A wide range of galvanic currents resulted from electrical contact of restorations in vivo. These currents were influenced by restoration age and total surface area of the galvanic couple. For amalgam-amalgam couples, the difference in the pre-contact corrosion potentials may be useful in predicting galvanic currents, when the difference is at least 24 mV.
OBJECTIVES: It is important to characterize the surface of dental amalgam in order to understand the process of mercury release from amalgam restorations in the oral cavity. The mercury evaporation occurs not only from the newly made restoration but also from the set material. METHODS: The surfaces of four different types of amalgams, which had been well set, were analyzed with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the relationship between surface compositions and mercury release was studied. Fresh amalgam surfaces as well as aged surfaces, which were stored for 30 days in air, were investigated using XPS and the chemical states of amalgam components and oxygen were studied. The aged surfaces were also characterized with XRD and grazing angle XRD. RESULTS: With increased oxidation, the surface contents of tin and oxygen were increased in all amalgams. In contrast, the surface contents of copper and mercury were decreased. An increase of zinc or indium content were observed in zinc or indium containing amalgams, respectively. A surface layer enriched with indium and oxygen was clearly detected by XPS but not with grazing angle XRD. SIGNIFICANCE: The thickness of the enriched surface layer is estimated to be in the order of few nanometer, which is approximately equal to the analysis depth of XPS. In addition, the presence of metallic elements, like tin and zinc, that readily form a stable oxide layer at the surface suppress the release of mercury.
For the past ten years, the amounts of mercury vapor released from dental amalgams and the possibility of side-effects caused by these amounts have been discussed. Although no adverse health effects have been substantiated from these minute amounts, besides rare cases of allergies, this release should be reduced. The aim of this study was to reduce the mercury evaporation from a high-copper amalgam during setting by triturating the alloy powder with binary Hg-In liquid alloys having various indium concentrations set at 0, 5, 10, 20, 30, 40, and 50 wt%. Specimens (n = 4) were made for each amalgam according to ANSI/ADA Specification #1 and placed into a measuring chamber kept at 36.5 +/- 0.5 degrees C, through which a continuous air flow of 0.75 L/min was pumped. The total mercury release was measured during the setting period, according to the method described by Ferracane et al. (1992). Four additional specimens were prepared from a modified 14% Indisperse amalgam powder for the purpose of comparison. The results showed that the release of mercury vapor decreased with increasing indium concentrations, and that the amalgams made with the Hg-In liquid alloy with 10% In or more released significantly less mercury than the modified 14% Indisperse. The method of mixing indium in mercury prior to trituration appeared to be another effective method for reducing mercury evaporation during setting. The reduced mercury release may be explained by a reduction of mercury concentration in the structure, a reduction of vapor pressure for the mercury in the matrix phases, or more efficient formation of a surface oxide layer.
The authors determined the number and surface area of occlusal dental amalgams in a group of 129 Roman Catholic sisters who were 75 to 102 years of age. Findings from this study of women with relatively homogeneous adult lifestyles and environments suggest that existing amalgams are not associated with lower performance on eight different tests of cognitive function.
The effects of noble metals added as part of a Ag-Cu dispersant on the compressive strength and creep of dental amalgams was determined. The Ag-Cu eutectic used in high copper dispersant alloy L(0), was altered by adding 15 per cent by weight (wt%) of noble metal in place of Ag. In L(1) the noble metal was Pd. In L(2), Au and Pd were combined in equal proportions. In L(3), the noble metal content was Pd and Pt in equal proportions. A low copper lathe-cut amalgam, Aristalloy was used as the matrix. Amalgams S(0) and S(1) had the same composition as L(0) and L(1) except that the the low copper alloy matrix was Spheralloy, a low copper spherical amalgam. The compressive strength and creep were measured according to American Dental Association specification No. 1 and the results analysed by ANOVA. The addition of noble metals to the dispersant significantly lowered the 1-h compressive strength of amalgams. Compared to the control amalgam L(0), the 24-h compressive strength was increased for L(1) and L(2) but lowered for L(3). The ADA creep values were significantly lowered by addition of all combinations of noble metals. Reported microstructural changes such as an increase in unreacted particles, and a slowed setting reaction may account for the findings.
Mercury (Hg) vapor exposure from dental amalgam has been demonstrated to exceed the sum of all other exposure sources. Therefore the effects of inorganic Hg exposure upon cell function in the brain and in the intestinal bacteria have recently been examined. In rats we demonstrate that ADP-ribosylation of tubulin and actin brain proteins is markedly inhibited, and that ionic Hg can thus alter a neurochemical reaction involved with maintaining neuron membrane structure. In monkeys we show that Hg, specifically from amalgam, will enrich the intestinal flora with Hg-resistant bacterial species which in turn also become resistant to antibiotics.
Increase in dimension in relation to mercury content, annealing time at 37 degrees C at 24 and 3500 hours and mercury content of dental amalgam mixed by machine and hand-packed in cylindrical moulds is shown.
The purpose of this study was to investigate the influence of relevant microstructural and compositional factors on the creep of 12 representative dental amalgams by means of stepwise multiple linear regression. The independent variables accepted by the regression were volume percent of the eta' (Cu6Sn5) phase, grain size of the gamma 1 (Ag2Hg3) phase, volume percent of the gamma (Ag3Sn) plus epsilon (Cu3Sn) phases, number of very small eta' crystals (less than 1.5 microns) per mm, and weight percent of Hg. The results of this regression showed an adjusted R2 of 0.949, significant at p = 0.002.
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