The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Toru Okabe - One of the best experts on this subject based on the ideXlab platform.
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mercury release from Dental Amalgams into continuously replenished liquids
Dental Materials, 2003Co-Authors: Toru Okabe, Jack L Ferracane, Russell G Keanini, B Elvebak, L Carrasco, Hiroshi NakajimaAbstract:Abstract Objective : Studies have been performed using high- and low-copper Amalgams to measure the amounts of mercury dissolution from Dental amalgam in liquids such as artificial saliva; however, in most cases, mercury dissolution has been measured under static conditions and as such, may be self-limiting. This study measured the mercury release from low- and high-copper Amalgams into flowing aqueous solutions to determine whether the total amounts of dissolution vary under these conditions when tested at neutral and acidic pH. Methods : High- and low-copper amalgam specimens were prepared and kept for 3 days. They were then longitudinally suspended in dissolution cells with an outlet at the bottom. Deionized water or acidic solution (pH1) was pumped through the cell. Test solutions were collected at several time periods up to 6 days or 1 month and then analyzed with a cold vapor atomic absorption spectrophotometer. After dissolution testing, the specimens were examined using SEM/XEDA for any selective degradation of the phases in the amalgam. Results : Except for the high-copper amalgam in the pH1 solution, the dissolution rates were found to decrease exponentially with time. The rate for the high-copper amalgam in pH1 solution slowly increased for 1 month. The total amounts (μg/cm 2 ) of mercury released over 6 days or 1 month from both types of amalgam in deionized water were not significantly different ( p ≥0.05). The high-copper amalgam released significantly more mercury than the low-copper amalgam in the pH1 solution at both time periods. For both Amalgams, the dissolution in pH1 was significantly higher than in deionized water. Significance : Mercury dissolution from amalgam under dynamic conditions is enhanced in an acidic media, and most prominently for a high-copper formulation.
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theoretical models of mercury dissolution from Dental Amalgams in neutral and acidic flows
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2001Co-Authors: Russell G Keanini, Jack L Ferracane, Toru OkabeAbstract:This article reports an experimental and theoretical investigation of mercury dissolution from Dental Amalgams immersed in neutral (noncorrosive) and acidic (corrosive) flows. Atomic absorption spectrophotometric measurements of Hg loss indicate that in neutral flow, surface oxide films formed in air prior to immersion persist and effectively suppress significant mercury release. In acidic (pH 1) flows, by contrast, oxide films are unstable and dissolve; depending on the amalgam’s material composition, particularly its copper content, two distinct mercury release mechanisms are initiated. In low copper amalgam, high initial mercury release rates are observed and appear to reflect preferential mercury dissolution from unstable Sn8Hg (γ 2) grains within the amalgam matrix. In high copper amalgam, mercury release rates are initially low, but increase with time. Microscopic examination suggests that this feature reflects corrosion of copper from grains of Cu6Sn5 (η′) and consequent exposure of Ag2Hg3 (γ 1) grains; the latter serve as internal mercury release sites and become more numerous as corrosion proceeds. Three theoretical models are proposed in order to explain observed dissolution characteristics. Model I, applicable to high and low copper Amalgams in neutral flow, assumes that mercury dissolution is mediated by solid diffusion within the amalgam, and that a thin oxide film persists on the amalgam’s surface and lumps diffusive in-film transport into an effective convective boundary condition. Model II, applicable to low copper amalgam in acidic flow, assumes that the amalgam’s external oxide film dissolves on a short time scale relative to the experimental observation period; it neglects corrosive suppression of mercury transport. Model III, applicable to high copper amalgam in acidic flow, assumes that internal mercury release sites are created by corrosion of copper in η′ grains and that corrosion proceeds via an oxidation-reduction reaction involving bound copper and diffusing hydrogen ions. The models appear to capture the correct time dependence of each dissolution mechanism and to provide reasonable fits to the experimental data.
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cyclic voltammetry of Dental Amalgams
Dental Materials, 1996Co-Authors: Noriko Horasawa, Hiroshi Nakajima, Jack L Ferracane, Shigeo Takahashi, Toru OkabeAbstract:Abstract Objectives . This study used cyclic voltammetry to examine the effect of the composition of Dental Amalgams on their electrochemical behavior, including reactions occurring outside of oral conditions. Methods . Amalgams (residual mercury 47.5%) were prepared using two low-copper (3 wt% Cu) powders and five high-copper powders (40–80 wt% Ag, 12–30 wt% Cu) with and without zinc (1.5 wt%). Cyclic voltammograms were obtained at 37°C in 1.0% NaCl scanning at 2 mV/s in the potential range from −1.5 V to +0.8 V vs. Ag/AgCl. Results . During the anodic scans, AgCl and Hg 2 Cl 2 films were formed on all Amalgams except the one with only 40 wt% Ag. In all high-copper Amalgams, a prominent Cu (oxidation) peak was found at −0.1 V, indicating the release of copper during corrosion. Zinc affected the oxidation process for both low- and high-copper Amalgams. When zinc was absent, a peak for Sn 2+ oxidation appeared at −0.4 V. When zinc was present, a Sn 4+ oxidation peak was revealed at −0.6 V. In some Amalgams, there was evidence of the selective corrosion (pitting corrosion) of tin and copper. In the lowest silver-content amalgam, no protective films were formed, which is indicative of its poor corrosion resistance. As expected, in all the low-copper Amalgams, an extreme increase in current density was recorded immediately at 0 V, due to the release of tin from γ 2 . Significance . Cyclic voltammetry is useful for the rapid examination (less than an hour) of the electrochemical behavior of Amalgams, specifically to obtain information on the formation of compounds and the sequences of electrochemical reactions.
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reduced mercury vapor release from Dental Amalgams prepared with binary hg in liquid alloys
Journal of Dental Research, 1994Co-Authors: Toru Okabe, T Yamashita, H Nakajima, A Berglund, L Zhao, Jack L FerracaneAbstract: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'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 ...
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dynamic mechanical properties of Dental Amalgams
Dental Materials, 1990Co-Authors: E H Greener, T Hanawa, Toru OkabeAbstract:Abstract The dynamic mechanical properties of two high-copper Amalgams (Tytin and Dispersalloy) and two traditional Amalgams (Aristalloy and Aristalloy with Zn) were measured over a temperature range of 0–70°C and at frequencies of 0.1, 1, and 10 Hz by means of a DuPont DMA. Values of storage modulus (E′) for the Amalgams were equivalent to the Young's modulus (E) measured from static mechanical test methods, with Dispersalloy demonstrating the highest moduli. Values of E′ decreased with increased temperature. E′ of traditional Amalgams decreased more rapidly than did those of the Cu-rich Amalgams. Values of loss modulus (E″) for Tytin were smaller than those of Dispersalloy and the two types of Aristalloy. High values of E″ for the traditional Amalgams correspond to a greater viscous behavior. Marked differences between the magnitude of tanδ and its temperature coefficients for traditional and high-copper Amalgams were observed, which is indicative of differences in visco-elastic behavior between these two amalgam systems.
Mark R Geier - One of the best experts on this subject based on the ideXlab platform.
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evidence supporting a link between Dental Amalgams and chronic illness fatigue depression anxiety and suicide
Neuro endocrinology letters, 2014Co-Authors: Janet K Kern, Geir Bjorklund, David A Geier, Paul G King, Kristin G Homme, Boyd E Haley, Lisa K Sykes, Mark R GeierAbstract:The purpose of this review is to examine the evidence for a relationship between mercury (Hg) exposure from Dental Amalgams and certain idiopathic chronic illnesses - chronic fatigue syndrome (CFS), fibromyalgia (FM), depression, anxiety, and suicide. Dental amalgam is a commonly used Dental restorative material that contains approximately 50% elemental mercury (Hg0) by weight and releases Hg0 vapor. Studies have shown that chronic Hg exposure from various sources including Dental Amalgams is associated with numerous health complaints, including fatigue, anxiety, and depression - and these are among the main symptoms that are associated with CFS and FM. In addition, several studies have shown that the removal of Amalgams is associated with improvement in these symptoms. Although the issue of amalgam safety is still under debate, the preponderance of evidence suggests that Hg exposure from Dental Amalgams may cause or contribute to many chronic conditions. Thus, consideration of Hg toxicity may be central to the effective clinical investigation of many chronic illnesses, particularly those involving fatigue and depression. Language: en
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a significant dose dependent relationship between mercury exposure from Dental Amalgams and kidney integrity biomarkers a further assessment of the casa pia children s Dental amalgam trial
Human & Experimental Toxicology, 2013Co-Authors: David A Geier, Paul G King, Thomas J Carmody, J K Kern, Mark R GeierAbstract:Dental Amalgams are a commonly used Dental restorative material. Amalgams are about 50% mercury (Hg), and Hg is known to significantly accumulate in the kidney. It was hypothesized that because Hg accumulates in the proximal tubules (PTs), glutathione-S-transferases (GST)-α (suggestive of kidney damage at the level of PT) would be expected to be more related to Hg exposure than GST-π (suggestive of kidney damage at the level of the distal tubules). Urinary biomarkers of kidney integrity were examined in children of 8–18 years old, with and without Dental amalgam fillings, from a completed clinical trial (parent study). Our study determined whether there was a significant dose-dependent correlation between increasing Hg exposure from Dental Amalgams and GST-α and GST-π as biomarkers of kidney integrity. Overall, the present study, using a different and more sensitive statistical model than the parent study, revealed a statistically significant dose-dependent correlation between cumulative exposure to Hg fr...
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a dose dependent relationship between mercury exposure from Dental Amalgams and urinary mercury levels a further assessment of the casa pia children s Dental amalgam trial
Human & Experimental Toxicology, 2012Co-Authors: David A Geier, Janet K Kern, Paul G King, Thomas J Carmody, Mark R GeierAbstract:Dental Amalgams are a commonly used Dental restorative material, and Amalgams are about 50% mercury (Hg). In our study, urinary Hg levels was examined in children of age 8–18 years, with and without Dental amalgam fillings, from a completed clinical trial (parent study) that was designed to evaluate the potential health consequences of prolonged exposure to Hg from Dental amalgam fillings. Our study was designed to determine whether there was a significant dose-dependent correlation between increasing Hg exposure from Dental Amalgams and urinary Hg levels. Hg exposure depends on the size and number of teeth with Dental Amalgams. Overall, consistent with the results observed in the parent study, there was a statistically significant dose-dependent correlation between cumulative exposure to Hg from Dental Amalgams and urinary Hg levels, after covariate adjustment. Further, it was observed that urinary Hg levels increased by 18% to 52% among 8 to 18 year old individuals, respectively, with an average exposur...
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A significant relationship between mercury exposure from Dental Amalgams and urinary porphyrins: a further assessment of the Casa Pia children’s Dental amalgam trial
BioMetals, 2011Co-Authors: David A Geier, Janet K Kern, Paul G King, Thomas J Carmody, Mark R GeierAbstract:Previous studies noted specific changes in urinary porphyrin excretion patterns associated with exposure to mercury (Hg) in animals and humans. In our study, urinary porphyrin concentrations were examined in normal children 8–18 years-old from a reanalysis of data provided from a randomized, prospective clinical trial that was designed to evaluate the potential health consequences of prolonged exposure to Hg from Dental amalgam fillings (the parent study). Our analysis examined dose-dependent correlations between increasing Hg exposure from Dental Amalgams and urinary porphyrins utilizing statistical models with adjustments for the baseline level (i.e. study year 1) of the following variables: urinary Hg, each urinary porphyrin measure, gender, race, and the level of lead (Pb) in each subject’s blood. Significant dose-dependent correlations between cumulative exposure to Hg from Dental Amalgams and urinary porphyrins associated with Hg body-burden (pentacarboxyporphyrin, precoproporphyrin, and coproporphyrin) were observed. Overall, 5–10% increases in Hg-associated porphyrins for subjects receiving an average number of Dental amalgam fillings in comparison to subjects receiving only composite fillings were observed over the 8-year course of the study. In contrast, no significant correlations were observed between cumulative exposure to Hg from Dental Amalgams and urinary porphyrins not associated with Hg body-burden (uroporphyrin, heptacarboxyporphyrin, and hexacarboxyporphyrin). In conclusion, our study, in contrast to the no-effect results published from the parent study, further establishes the sensitivity and specificity of specific urinary porphyrins as a biomarker for low-level Hg body-burden, and also reveals that Dental Amalgams are a significant chronic contributor to Hg body-burden.
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a prospective study of prenatal mercury exposure from maternal Dental Amalgams and autism severity
Acta Neurobiologiae Experimentalis, 2009Co-Authors: David A Geier, Janet K Kern, Mark R GeierAbstract:The practice of using Amalgams (which generally contain 50% mercury) in dentistry has existed for over 150 years. As of mid-2008, the US Food and Drug Administration (FDA) has declined to classify the medical-device safety of Amalgams used in dentistry. The American Dental Association maintains that the mercury in amalgam is safe and that the mercury does not leak (Edlich et al. 2007).Yet, the research evidence suggests that there is sig-nificant amount of elemental leaching and mercury vapor release from Amalgams (Cohen and Penugonda 2001) and that this liberated mercury is absorbed by several body tissues (Mutter et al. 2004, Edlich et al. 2007). As a result, Dental Amalgams are a significant source of mercury body burden, as studies in animals and humans show (Mutter et al. 2007). For example, Guzzi and coworkers (2006) found that, on autopsy, total mercury levels were significantly higher in sub-jects with a greater number of amalgam surfaces (>12) compared with those who had fewer (0–3), in all types of tissue. These authors also reported that the greater the number of Amalgams, the greater the likelihood that mercury would be found in the brain. In regard to amalgam bearers, other investigators have reported an approximate 2- to 5-fold increase of the mercury level in blood and urine as well as a 2- to 12-fold increase of the mercury concentration in several body tissues (Mutter et al. 2007). Also, mercury from maternal amalgam fillings leads to a significant increase of mer-cury concentration in the tissues and the hair of fetuses and newborn children. Furthermore, placental, fetal, and infant mercury body burden correlates with the numbers of amalgam fillings of the mothers (Mutter et al. 2007, Palkovicova et al. 2008). Finally, mercury levels in amniotic fluid and breast milk correlate sig-nificantly with the number of maternal Dental amal-gam fillings (Mutter et al. 2007).The overall importance of Dental Amalgams, particu-larly maternal Dental Amalgams, significantly contrib -uting to fetal and early infant mercury body-burden stems from the fact that recent studies have postulated that mercury exposure can cause immune, sensory,
Jack L Ferracane - One of the best experts on this subject based on the ideXlab platform.
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mercury release from Dental Amalgams into continuously replenished liquids
Dental Materials, 2003Co-Authors: Toru Okabe, Jack L Ferracane, Russell G Keanini, B Elvebak, L Carrasco, Hiroshi NakajimaAbstract:Abstract Objective : Studies have been performed using high- and low-copper Amalgams to measure the amounts of mercury dissolution from Dental amalgam in liquids such as artificial saliva; however, in most cases, mercury dissolution has been measured under static conditions and as such, may be self-limiting. This study measured the mercury release from low- and high-copper Amalgams into flowing aqueous solutions to determine whether the total amounts of dissolution vary under these conditions when tested at neutral and acidic pH. Methods : High- and low-copper amalgam specimens were prepared and kept for 3 days. They were then longitudinally suspended in dissolution cells with an outlet at the bottom. Deionized water or acidic solution (pH1) was pumped through the cell. Test solutions were collected at several time periods up to 6 days or 1 month and then analyzed with a cold vapor atomic absorption spectrophotometer. After dissolution testing, the specimens were examined using SEM/XEDA for any selective degradation of the phases in the amalgam. Results : Except for the high-copper amalgam in the pH1 solution, the dissolution rates were found to decrease exponentially with time. The rate for the high-copper amalgam in pH1 solution slowly increased for 1 month. The total amounts (μg/cm 2 ) of mercury released over 6 days or 1 month from both types of amalgam in deionized water were not significantly different ( p ≥0.05). The high-copper amalgam released significantly more mercury than the low-copper amalgam in the pH1 solution at both time periods. For both Amalgams, the dissolution in pH1 was significantly higher than in deionized water. Significance : Mercury dissolution from amalgam under dynamic conditions is enhanced in an acidic media, and most prominently for a high-copper formulation.
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theoretical models of mercury dissolution from Dental Amalgams in neutral and acidic flows
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2001Co-Authors: Russell G Keanini, Jack L Ferracane, Toru OkabeAbstract:This article reports an experimental and theoretical investigation of mercury dissolution from Dental Amalgams immersed in neutral (noncorrosive) and acidic (corrosive) flows. Atomic absorption spectrophotometric measurements of Hg loss indicate that in neutral flow, surface oxide films formed in air prior to immersion persist and effectively suppress significant mercury release. In acidic (pH 1) flows, by contrast, oxide films are unstable and dissolve; depending on the amalgam’s material composition, particularly its copper content, two distinct mercury release mechanisms are initiated. In low copper amalgam, high initial mercury release rates are observed and appear to reflect preferential mercury dissolution from unstable Sn8Hg (γ 2) grains within the amalgam matrix. In high copper amalgam, mercury release rates are initially low, but increase with time. Microscopic examination suggests that this feature reflects corrosion of copper from grains of Cu6Sn5 (η′) and consequent exposure of Ag2Hg3 (γ 1) grains; the latter serve as internal mercury release sites and become more numerous as corrosion proceeds. Three theoretical models are proposed in order to explain observed dissolution characteristics. Model I, applicable to high and low copper Amalgams in neutral flow, assumes that mercury dissolution is mediated by solid diffusion within the amalgam, and that a thin oxide film persists on the amalgam’s surface and lumps diffusive in-film transport into an effective convective boundary condition. Model II, applicable to low copper amalgam in acidic flow, assumes that the amalgam’s external oxide film dissolves on a short time scale relative to the experimental observation period; it neglects corrosive suppression of mercury transport. Model III, applicable to high copper amalgam in acidic flow, assumes that internal mercury release sites are created by corrosion of copper in η′ grains and that corrosion proceeds via an oxidation-reduction reaction involving bound copper and diffusing hydrogen ions. The models appear to capture the correct time dependence of each dissolution mechanism and to provide reasonable fits to the experimental data.
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cyclic voltammetry of Dental Amalgams
Dental Materials, 1996Co-Authors: Noriko Horasawa, Hiroshi Nakajima, Jack L Ferracane, Shigeo Takahashi, Toru OkabeAbstract:Abstract Objectives . This study used cyclic voltammetry to examine the effect of the composition of Dental Amalgams on their electrochemical behavior, including reactions occurring outside of oral conditions. Methods . Amalgams (residual mercury 47.5%) were prepared using two low-copper (3 wt% Cu) powders and five high-copper powders (40–80 wt% Ag, 12–30 wt% Cu) with and without zinc (1.5 wt%). Cyclic voltammograms were obtained at 37°C in 1.0% NaCl scanning at 2 mV/s in the potential range from −1.5 V to +0.8 V vs. Ag/AgCl. Results . During the anodic scans, AgCl and Hg 2 Cl 2 films were formed on all Amalgams except the one with only 40 wt% Ag. In all high-copper Amalgams, a prominent Cu (oxidation) peak was found at −0.1 V, indicating the release of copper during corrosion. Zinc affected the oxidation process for both low- and high-copper Amalgams. When zinc was absent, a peak for Sn 2+ oxidation appeared at −0.4 V. When zinc was present, a Sn 4+ oxidation peak was revealed at −0.6 V. In some Amalgams, there was evidence of the selective corrosion (pitting corrosion) of tin and copper. In the lowest silver-content amalgam, no protective films were formed, which is indicative of its poor corrosion resistance. As expected, in all the low-copper Amalgams, an extreme increase in current density was recorded immediately at 0 V, due to the release of tin from γ 2 . Significance . Cyclic voltammetry is useful for the rapid examination (less than an hour) of the electrochemical behavior of Amalgams, specifically to obtain information on the formation of compounds and the sequences of electrochemical reactions.
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reduced mercury vapor release from Dental Amalgams prepared with binary hg in liquid alloys
Journal of Dental Research, 1994Co-Authors: Toru Okabe, T Yamashita, H Nakajima, A Berglund, L Zhao, Jack L FerracaneAbstract: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'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 ...
David A Geier - One of the best experts on this subject based on the ideXlab platform.
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evidence supporting a link between Dental Amalgams and chronic illness fatigue depression anxiety and suicide
Neuro endocrinology letters, 2014Co-Authors: Janet K Kern, Geir Bjorklund, David A Geier, Paul G King, Kristin G Homme, Boyd E Haley, Lisa K Sykes, Mark R GeierAbstract:The purpose of this review is to examine the evidence for a relationship between mercury (Hg) exposure from Dental Amalgams and certain idiopathic chronic illnesses - chronic fatigue syndrome (CFS), fibromyalgia (FM), depression, anxiety, and suicide. Dental amalgam is a commonly used Dental restorative material that contains approximately 50% elemental mercury (Hg0) by weight and releases Hg0 vapor. Studies have shown that chronic Hg exposure from various sources including Dental Amalgams is associated with numerous health complaints, including fatigue, anxiety, and depression - and these are among the main symptoms that are associated with CFS and FM. In addition, several studies have shown that the removal of Amalgams is associated with improvement in these symptoms. Although the issue of amalgam safety is still under debate, the preponderance of evidence suggests that Hg exposure from Dental Amalgams may cause or contribute to many chronic conditions. Thus, consideration of Hg toxicity may be central to the effective clinical investigation of many chronic illnesses, particularly those involving fatigue and depression. Language: en
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a significant dose dependent relationship between mercury exposure from Dental Amalgams and kidney integrity biomarkers a further assessment of the casa pia children s Dental amalgam trial
Human & Experimental Toxicology, 2013Co-Authors: David A Geier, Paul G King, Thomas J Carmody, J K Kern, Mark R GeierAbstract:Dental Amalgams are a commonly used Dental restorative material. Amalgams are about 50% mercury (Hg), and Hg is known to significantly accumulate in the kidney. It was hypothesized that because Hg accumulates in the proximal tubules (PTs), glutathione-S-transferases (GST)-α (suggestive of kidney damage at the level of PT) would be expected to be more related to Hg exposure than GST-π (suggestive of kidney damage at the level of the distal tubules). Urinary biomarkers of kidney integrity were examined in children of 8–18 years old, with and without Dental amalgam fillings, from a completed clinical trial (parent study). Our study determined whether there was a significant dose-dependent correlation between increasing Hg exposure from Dental Amalgams and GST-α and GST-π as biomarkers of kidney integrity. Overall, the present study, using a different and more sensitive statistical model than the parent study, revealed a statistically significant dose-dependent correlation between cumulative exposure to Hg fr...
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a dose dependent relationship between mercury exposure from Dental Amalgams and urinary mercury levels a further assessment of the casa pia children s Dental amalgam trial
Human & Experimental Toxicology, 2012Co-Authors: David A Geier, Janet K Kern, Paul G King, Thomas J Carmody, Mark R GeierAbstract:Dental Amalgams are a commonly used Dental restorative material, and Amalgams are about 50% mercury (Hg). In our study, urinary Hg levels was examined in children of age 8–18 years, with and without Dental amalgam fillings, from a completed clinical trial (parent study) that was designed to evaluate the potential health consequences of prolonged exposure to Hg from Dental amalgam fillings. Our study was designed to determine whether there was a significant dose-dependent correlation between increasing Hg exposure from Dental Amalgams and urinary Hg levels. Hg exposure depends on the size and number of teeth with Dental Amalgams. Overall, consistent with the results observed in the parent study, there was a statistically significant dose-dependent correlation between cumulative exposure to Hg from Dental Amalgams and urinary Hg levels, after covariate adjustment. Further, it was observed that urinary Hg levels increased by 18% to 52% among 8 to 18 year old individuals, respectively, with an average exposur...
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A significant relationship between mercury exposure from Dental Amalgams and urinary porphyrins: a further assessment of the Casa Pia children’s Dental amalgam trial
BioMetals, 2011Co-Authors: David A Geier, Janet K Kern, Paul G King, Thomas J Carmody, Mark R GeierAbstract:Previous studies noted specific changes in urinary porphyrin excretion patterns associated with exposure to mercury (Hg) in animals and humans. In our study, urinary porphyrin concentrations were examined in normal children 8–18 years-old from a reanalysis of data provided from a randomized, prospective clinical trial that was designed to evaluate the potential health consequences of prolonged exposure to Hg from Dental amalgam fillings (the parent study). Our analysis examined dose-dependent correlations between increasing Hg exposure from Dental Amalgams and urinary porphyrins utilizing statistical models with adjustments for the baseline level (i.e. study year 1) of the following variables: urinary Hg, each urinary porphyrin measure, gender, race, and the level of lead (Pb) in each subject’s blood. Significant dose-dependent correlations between cumulative exposure to Hg from Dental Amalgams and urinary porphyrins associated with Hg body-burden (pentacarboxyporphyrin, precoproporphyrin, and coproporphyrin) were observed. Overall, 5–10% increases in Hg-associated porphyrins for subjects receiving an average number of Dental amalgam fillings in comparison to subjects receiving only composite fillings were observed over the 8-year course of the study. In contrast, no significant correlations were observed between cumulative exposure to Hg from Dental Amalgams and urinary porphyrins not associated with Hg body-burden (uroporphyrin, heptacarboxyporphyrin, and hexacarboxyporphyrin). In conclusion, our study, in contrast to the no-effect results published from the parent study, further establishes the sensitivity and specificity of specific urinary porphyrins as a biomarker for low-level Hg body-burden, and also reveals that Dental Amalgams are a significant chronic contributor to Hg body-burden.
-
a prospective study of prenatal mercury exposure from maternal Dental Amalgams and autism severity
Acta Neurobiologiae Experimentalis, 2009Co-Authors: David A Geier, Janet K Kern, Mark R GeierAbstract:The practice of using Amalgams (which generally contain 50% mercury) in dentistry has existed for over 150 years. As of mid-2008, the US Food and Drug Administration (FDA) has declined to classify the medical-device safety of Amalgams used in dentistry. The American Dental Association maintains that the mercury in amalgam is safe and that the mercury does not leak (Edlich et al. 2007).Yet, the research evidence suggests that there is sig-nificant amount of elemental leaching and mercury vapor release from Amalgams (Cohen and Penugonda 2001) and that this liberated mercury is absorbed by several body tissues (Mutter et al. 2004, Edlich et al. 2007). As a result, Dental Amalgams are a significant source of mercury body burden, as studies in animals and humans show (Mutter et al. 2007). For example, Guzzi and coworkers (2006) found that, on autopsy, total mercury levels were significantly higher in sub-jects with a greater number of amalgam surfaces (>12) compared with those who had fewer (0–3), in all types of tissue. These authors also reported that the greater the number of Amalgams, the greater the likelihood that mercury would be found in the brain. In regard to amalgam bearers, other investigators have reported an approximate 2- to 5-fold increase of the mercury level in blood and urine as well as a 2- to 12-fold increase of the mercury concentration in several body tissues (Mutter et al. 2007). Also, mercury from maternal amalgam fillings leads to a significant increase of mer-cury concentration in the tissues and the hair of fetuses and newborn children. Furthermore, placental, fetal, and infant mercury body burden correlates with the numbers of amalgam fillings of the mothers (Mutter et al. 2007, Palkovicova et al. 2008). Finally, mercury levels in amniotic fluid and breast milk correlate sig-nificantly with the number of maternal Dental amal-gam fillings (Mutter et al. 2007).The overall importance of Dental Amalgams, particu-larly maternal Dental Amalgams, significantly contrib -uting to fetal and early infant mercury body-burden stems from the fact that recent studies have postulated that mercury exposure can cause immune, sensory,
Hiroshi Nakajima - One of the best experts on this subject based on the ideXlab platform.
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mercury release from Dental Amalgams into continuously replenished liquids
Dental Materials, 2003Co-Authors: Toru Okabe, Jack L Ferracane, Russell G Keanini, B Elvebak, L Carrasco, Hiroshi NakajimaAbstract:Abstract Objective : Studies have been performed using high- and low-copper Amalgams to measure the amounts of mercury dissolution from Dental amalgam in liquids such as artificial saliva; however, in most cases, mercury dissolution has been measured under static conditions and as such, may be self-limiting. This study measured the mercury release from low- and high-copper Amalgams into flowing aqueous solutions to determine whether the total amounts of dissolution vary under these conditions when tested at neutral and acidic pH. Methods : High- and low-copper amalgam specimens were prepared and kept for 3 days. They were then longitudinally suspended in dissolution cells with an outlet at the bottom. Deionized water or acidic solution (pH1) was pumped through the cell. Test solutions were collected at several time periods up to 6 days or 1 month and then analyzed with a cold vapor atomic absorption spectrophotometer. After dissolution testing, the specimens were examined using SEM/XEDA for any selective degradation of the phases in the amalgam. Results : Except for the high-copper amalgam in the pH1 solution, the dissolution rates were found to decrease exponentially with time. The rate for the high-copper amalgam in pH1 solution slowly increased for 1 month. The total amounts (μg/cm 2 ) of mercury released over 6 days or 1 month from both types of amalgam in deionized water were not significantly different ( p ≥0.05). The high-copper amalgam released significantly more mercury than the low-copper amalgam in the pH1 solution at both time periods. For both Amalgams, the dissolution in pH1 was significantly higher than in deionized water. Significance : Mercury dissolution from amalgam under dynamic conditions is enhanced in an acidic media, and most prominently for a high-copper formulation.
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cyclic voltammetry of Dental Amalgams
Dental Materials, 1996Co-Authors: Noriko Horasawa, Hiroshi Nakajima, Jack L Ferracane, Shigeo Takahashi, Toru OkabeAbstract:Abstract Objectives . This study used cyclic voltammetry to examine the effect of the composition of Dental Amalgams on their electrochemical behavior, including reactions occurring outside of oral conditions. Methods . Amalgams (residual mercury 47.5%) were prepared using two low-copper (3 wt% Cu) powders and five high-copper powders (40–80 wt% Ag, 12–30 wt% Cu) with and without zinc (1.5 wt%). Cyclic voltammograms were obtained at 37°C in 1.0% NaCl scanning at 2 mV/s in the potential range from −1.5 V to +0.8 V vs. Ag/AgCl. Results . During the anodic scans, AgCl and Hg 2 Cl 2 films were formed on all Amalgams except the one with only 40 wt% Ag. In all high-copper Amalgams, a prominent Cu (oxidation) peak was found at −0.1 V, indicating the release of copper during corrosion. Zinc affected the oxidation process for both low- and high-copper Amalgams. When zinc was absent, a peak for Sn 2+ oxidation appeared at −0.4 V. When zinc was present, a Sn 4+ oxidation peak was revealed at −0.6 V. In some Amalgams, there was evidence of the selective corrosion (pitting corrosion) of tin and copper. In the lowest silver-content amalgam, no protective films were formed, which is indicative of its poor corrosion resistance. As expected, in all the low-copper Amalgams, an extreme increase in current density was recorded immediately at 0 V, due to the release of tin from γ 2 . Significance . Cyclic voltammetry is useful for the rapid examination (less than an hour) of the electrochemical behavior of Amalgams, specifically to obtain information on the formation of compounds and the sequences of electrochemical reactions.