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PubMed2003

Dental amalgam and human health.

The use of dental amalgam as a restorative material has long been a contentious issue because of its elemental mercury component. While microleakage of mercury from amalgam has been conclusively confirmed over the past 30 years intensive research has failed to identify deleterious health outcomes. Mercury, as with other metals entering the body tissues, appears to be tolerated at low levels. Nevertheless, a contrary opinion is held by some professional and lay groups who advocate a zero tolerance for inhaled or ingested elemental mercury. They identify dental amalgam as an aetiological factor for neurological conditions such as chronic fatigue syndrome, multiple sclerosis and Alzheimer's disease resulting from chronic mercury poisoning. Epidemiological and clinical evidence of widespread chronic mercury toxicity associated with a body burden of amalgam has consistently failed to be established even in populations with a high prevalence of dental amalgam restorations. On current evidence, international consensus heavily supports the statement that amalgam does not constitute a health risk to patients. However, exposure to volatile free mercury in dental clinics should be controlled to eliminate occupational risk. This paper provides a general review of the current situation and issues. It offers a consensus viewpoint for practitioners and lay people in reaching an informed decision on dental amalgam restorations.

Body Burden↗
PubMed1977

Effect of trituration on dimensional changes of dental amalgam.

The dimensional changes of dental amalgams during setting was evaluated using different methods of specimen production, and measurement procedures. Amalgam specimens were prepared from 10 commercially available dental amalgam alloys by mechanical condensation. Dimensional change was measured on microcators with a measuring load of 1 g. The variation in dimensional change with trituration was substantial, and similar to the difference between various brands of alloys at the same trituration time. Porosity seems to vary between 0.1 and 0.6% independent of severity of trituration except for two alloys in which increased trituration time seemed to reduce porosity. It was therefore pointed out that even though trituration in most cases can be altered to make an amalgam expand, such procedures should not be followed since optimal values of other clinically significant properties may not be maintained.

Alloys↗
PubMed1990

The biocompatibility testing of some dental amalgams in vivo.

The biological responses to some dental amalgams were determined in vivo and compared with those of dental porcelain. The technique of implantation employed in the study addressed some of the vagaries of the Recommended Standard Practices for Biological Evaluation of Dental Materials (RSP) and considered both cellular responses (inflammation, infiltration and fibrogenic cell activity) and the organizational status of the resultant encapsulation. The implantation sites for both the experimental and control were biogeometrically similar, unlike those currently recommended in RSP. At the end of the test period, all the dental amalgams tested caused minor responses reflected by the formation of thin capsules with an acceptable matrix organization. The Australian manufactured dental amalgams--Permite C, Lojic, F400, New Ultrafine and GS80 all produced even capsules with quiescent cells. By one hundred days, the capsule around Dispersalloy, although generally well formed, showed some areas of cellular activity and matrix variability. The biological responses to all the dental amalgams examined were mild and considered to be acceptable for clinical usage. The matrix organization of enveloping capsules must be considered in the determination of the biocompatibility of a dental restorative material.

Animals↗
PubMed1991

Ethics and dental amalgam removal.

Recent media attention regarding dental amalgam restorations has generated needless fears among millions of dental patients. This article examines the issue of dental amalgam removal from an ethical perspective and offers some practical advice on how to address this problem in the dental office.

Beneficence↗
PubMed1992

Urinary mercury after administration of 2,3-dimercaptopropane-1-sulfonic acid: correlation with dental amalgam score.

There is considerable controversy as to whether dental amalgams may cause systemic health effects in humans because they liberate elemental mercury. Most such amalgams contain as much as 50% metallic mercury. To determine the influence of dental amalgams on the mercury body burden of humans, we have given volunteers, with and without amalgams in their mouth, the sodium salt of 2,3-dimercaptopropane-1-sulfonic acid (DMPS), a chelating agent safely used in the Soviet Union and West Germany for a number of years. The diameters of dental amalgams of the subjects were determined to obtain the amalgam score. Administration of 300 mg DMPS by mouth increased the mean urinary mercury excretion of the amalgam group from 0.70 to 17.2 micrograms and that of the nonamalgam group from 0.27 to 5.1 micrograms over a 9-h period. Two-thirds of the mercury excreted in the urine of those with dental amalgams appears to be derived originally from the mercury vapor released from their amalgams. Linear regression analysis indicated a highly significant positive correlation between the mercury excreted in the urine 2 h after DMPS administration and the dental amalgam scores. DMPS can be used to increase the urinary excretion of mercury and thus increase the significance and reliability of this measure of mercury exposure or burden, especially in cases of micromercurialism.

Adolescent↗
PubMed1997

Impact of nocturnal bruxism on mercury uptake from dental amalgams.

The mercury (Hg) release from dental amalgam fillings increases by mechanical stimulation. The aim of this study was to investigate the possible impact of nocturnal bruxism on Hg exposure from dental amalgams and to evaluate the effect of an occlusal appliance. 88 female patients from an orofacial pain clinic with a complete maxillary and mandibular dentition, a normal frontal vertical overbite with cuspid guidance, and at least 4 occlusal amalgam fillings in contact with antagonists in intercuspidal position, were examined with the Bruxcore bruxism monitoring device to measure the level of on-going nocturnal bruxism. Based on the degree of abrasion recorded, the subjects were divided into a group defined as bruxists, (n = 29), another group defined as non-bruxists, (n = 32), serving as controls, the intermediate group being discarded. The Hg exposure was assessed from the Hg concentration in plasma and urine, corrected for the creatinine content. In a regression model with bruxism as the only explanatory variable, no significant effect of bruxism was found, but when the number of amalgam fillings, chewing gum use, and other background variables were taken into account, there was a limited impact of bruxism on Hg in plasma. The nocturnal use of an occlusal appliance did not, however, significantly change the Hg levels. This study indicates that mechanical wear on amalgams from nocturnal bruxism may increase the Hg uptake, but the magnitude of this effect seems to be less than from the use of chewing gum.

Absorption↗
PubMed2005

The potential adverse health effects of dental amalgam.

There is significant public concern about the potential health effects of exposure to mercury vapour (Hg(0)) released from dental amalgam restorations. The purpose of this article is to provide information about the toxicokinetics of Hg(0), evaluate the findings from the recent scientific and medical literature, and identify research gaps that when filled may definitively support or refute the hypothesis that dental amalgam causes adverse health effects. Dental amalgam is a widely used restorative dental material that was introduced over 150 years ago. Most standard dental amalgam formulations contain approximately 50% elemental mercury. Experimental evidence consistently demonstrates that Hg(0) is released from dental amalgam restorations and is absorbed by the human body. Numerous studies report positive correlations between the number of dental amalgam restorations or surfaces and urine mercury concentrations in non-occupationally exposed individuals. Although of public concern, it is currently unclear what adverse health effects are caused by the levels of Hg(0) released from this restoration material. Historically, studies of occupationally exposed individuals have provided consistent information about the relationship between exposure to Hg(0) and adverse effects reflecting both nervous system and renal dysfunction. Workers are usually exposed to substantially higher Hg(0) levels than individuals with dental amalgam restorations and are typically exposed 8 hours per day for 20-30 years, whereas persons with dental amalgam restorations are exposed 24 hours per day over some portion of a lifetime. This review has uncovered no convincing evidence pointing to any adverse health effects that are attributable to dental amalgam restorations besides hypersensitivity in some individuals.

Dental Amalgam↗
PubMed2005

Corrosion potential variation of aged dental amalgam restorations over time.

OBJECTIVE: The corrosion potential of a dental amalgam restoration is generally determined using a single measurement, even though environmental factors and abrasion can continuously alter the surface state and reactivity of this alloy. It was, therefore, the purpose of this study to determine the maximum variability of the corrosion potential of aged dental amalgam restorations, for 28 days. METHODS: The corrosion potentials of 148 aged dental amalgam restorations in 12 human subjects were measured at t = 0 and 4 h, and 4, 7, 14, 21 and 28 days. Measurements were made with a high impedance voltmeter and a Ag/AgCl micro-reference electrode. The subjects were instructed not to alter their usual eating and oral hygiene routines. RESULTS: Corrosion potential changes occurred throughout the 28 days. They were both positive and negative for the same restoration, and were sometimes very large. Only 4 h after the initial measurement, the absolute value of the corrosion potential changes ranged between 18 and 287 mV for 50% of the restorations. The largest maximum absolute corrosion potential change for each subject's restorations ranged between 85 and 329 mV. Statistical analysis showed that the overall mean maximum absolute corrosion potential change for the subjects' restorations was 74 mV. SIGNIFICANCE: It was shown that the corrosion potential of aged dental amalgam restorations varies substantially over time, and that a single measurement is not representative of short- or long-term electrochemical behavior. This finding has implications regarding the corrosion rate of dental amalgam restorations, particularly those that are part of a galvanic couple.

Adult↗
PubMed2003

Maternal and neonatal hair mercury concentrations: the effect of dental amalgam.

OBJECTIVE: To evaluate maternal and fetal hair mercury levels in relation to the placement of dental amalgam tooth restorations. DESIGN: Cross sectional study involving women who never had dental amalgam restorations placed, women who had amalgam restorations placed before pregnancy and women who had restorations placed during the index pregnancy. SETTING: North of England Maternity Hospital. SAMPLE: Fifty-three healthy women who delivered healthy babies at term. METHODS: Maternal and fetal hair was collected in a standardised manner in the first few days following delivery. MAIN OUTCOME MEASURES: Maternal and neonatal hair mercury concentrations. RESULTS: When compared with women without restorations, there was a significant increase in the maternal hair mercury concentration in women who had dental amalgam placed outside of the index pregnancy and also in women who had dental amalgam placed during the index pregnancy. The fetal hair mercury concentration was significantly higher in babies when mothers had been exposed to dental amalgam either before pregnancy or during pregnancy compared with unexposed babies. There was no difference in the maternal or fetal hair mercury levels in the groups of patients who had dental amalgam placed before or during pregnancy. CONCLUSIONS: Maternal and fetal hair mercury levels were significantly higher in women who previously had dental amalgam restorations placed. There was no evidence that placement of dental amalgam restorations in pregnant women who had already similar restorations increased the maternal or fetal hair mercury level.

Adult↗
PubMed2004

Stress protein assay for the evaluation of cytotoxicity of dental amalgam.

To evaluate the cytotoxicity of mercury in dental amalgams, a stress protein assay was performed and the results were compared with the cytotoxicity evaluated by a neutral red uptake assay. The induction of a major stress protein, hsp70, was analyzed at levels of mRNA, synthesis and accumulation in human HeLa cells treated with extracts from amalgam, metal mercury and mercuric chloride. Mercuric chloride induced an increase in the synthesis of hsp70 at concentrations of mercury half those used for the neutral red uptake assay. The extracts from dental amalgam and metal mercury induced an increase in hsp70 mRNA at concentrations of mercury half those causing the inhibition of neutral red uptake into cells. Furthermore, the extracts from dental amalgam or metal mercury increased the synthesis of hsp70 and inhibited the uptake of dye at concentrations of mercury 1/10-1/50 lower than those at which mercuric chloride acted. These results suggest that the stress protein assay is more sensitive than the conventional neutral red assay for the evaluation of the cytotoxicity of mercury in dental amalgams and that the methods used in the preparation of metal solutions seem to be critical to the evaluation of cytotoxicity of dental materials.

Biological Transport, Active↗
PubMedDate not supplied

The use of dental amalgam--an art or a science?

Dental amalgam remains the best material for filling teeth when aesthetics are of secondary importance. Over the last 20 years improvements in the composition have reduced marginal failure due to creep and corrosion, and the use of modern adhesives has lead to an early seal between the tooth and the filling. However, the proper handling by the dentists remains as the cornerstone for fillings that are going to last. This article describes the history, classification, structure and handling variables of dental amalgams. It also discusses the effects of extra elements, bonding agents and the possible hazard of mercury.

Copper↗
PubMed1979

Mechanism of chloride corrosion of dental amalgam.

Polarization of conventional dental amalgam in Ringer's solution produces a dissolution of the gamma 2 phase at--250 mV (SCE) and formation of Sn-Cl and Sn-O-Cl. This study was undertaken to determine the electrochemical nature of these reactions. Potentiostatic polarization scans were run at 4, 37 and 50 degrees C in several dilutions of aerated Ringer's solution. Manipulation of reactant concentrations and electrolyte temperature produced shifts in the potentiostatic profiles. At 50 degrees C, a gamma 2 dissolution peak shift to -300 mV was observed, and at 4 degrees C the peak shifted to -200 mV. Dilution of Ringer's solution with respect to [Cl-] over three orders of magnitude produced a linear shift in the noble direction of 500 mV. Cathodic polarization appears to be limited by the oxygen half cell reaction. Changes of [Cl] affect the shape of the peak, round out its approach to the current maximum. Shifts in peak potential due to temperature and concentration changes agreed with calculations based on critical pitting potential for gamma2 dissolution due to a chloride reaction. Polarization profiles in pooled saliva agreed with calculated potentials based on known saliva [Cl-].

Chemical Phenomena↗
PubMed1997

Adhesive liner incorporation in dental amalgam restorations.

Previous studies have indicated that adhesive liners can affect the mechanical properties of set amalgam and, therefore, may become incorporated within the amalgam. The purpose of this in vitro study was to determine the distribution of two adhesive liners within standardized Class I amalgam restorations. Cavity preparations were restored with dental amalgam or with dental amalgam and either of two adhesive liners. Thin sections were cut from the restored teeth in various planes and examined radiographically and with a reflecting microscope. Radiographs were digitized and computer enhanced for improved observation. Amalgam restorations placed with adhesive liner had greater amounts of nonamalgam substance than did the nonadhesive liner restorations. Both Amalgambond Plus and Resinomer used with All-Bond II were capable of becoming incorporated within the body of a Class I restoration placed with a standard restorative amalgam bonding technique.

Composite Resins↗
PubMed1992

Release of mercury vapor from dental amalgam.

Because of its long-term clinical use there is more information and research data available about dental amalgam than about any other dental restorative material. However, on and off the safety of dental amalgam has been called in question and during the 80's the mercury controversy came to the fore, not only within the profession but also among the general public. Sources of mercury vapor contamination within dentistry were identified and attempts made to evaluate the contributions to the daily mercury uptake which can be attributed to dental amalgam. Mercury can be released from dental amalgam by evaporation and electrochemical corrosion as well as from amalgam particles which have been swallowed. A major route for mercury uptake from amalgam restorations is through inhalation of mercury vapor. The present study focused on experimental and analytical difficulties associated with the measurement of mercury vapor released in the oral cavity. A careful methodological study of the kind of source of mercury vapor that is prevalent and on the methods for measuring the intra-oral release of mercury vapor was carried out. With this as a basis quantitative determinations of the release rate of mercury vapor from amalgam restorations were made on healthy human subjects not occupationally exposed to mercury. The daily uptake of mercury from inhaled mercury vapor was calculated and salivary and urinary mercury levels were determined. In addition the release rate of mercury vapor from different types of amalgam was studied in vitro and in vivo. The findings may be summarized as follows: The only relevant measurable quantity when determining the mercury vapor released from amalgam restorations is the amount released per time unit, i.e. the amount of mercury vapor collected during intra-oral sampling is proportional to the sampling time. The diffusion of mercury atoms inside an amalgam restoration results in the formation of a concentration gradient in the surface of the amalgam. This mercury diffusion is the rate-determining step for mercury vapor release in the long run. In the short run the mercury concentration gradient prevalent on the amalgam surface on the measuring occasion is the apparent rate-determining step. The daily uptake of mercury from inhaled mercury vapor released from dental amalgam seems to make a very small contribution to the total body burden of mercury, in comparison with what can be tolerated in the work environment. The in vitro results revealed obvious differences regarding the release rate of mercury vapor from dissimilar amalgam types.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1981

Experimental microleakage around ageing dental amalgam restorations: a review.

In vitro and in vivo experimental microleakage around ageing dental amalgam restorations has been reviewed. The methodologies, materials and results were examined and discussed. The initial experimental microleakage which occurred around unlined/unvarnished dental amalgam restorations and the development of leakage around lined/varnished dental amalgam restorations underlines the problem of attaining a permanent effective seal around dental amalgam restorations. The limitations of microleakage studies have been outlined and the importance of an understanding of the chemical changes which occur in the microcrevices stressed. This understanding may facilitate the production of a lifelong successful dental amalgam restoration and perhaps the development of an anticariogenic amalgam type fissure sealant.

Dental Amalgam↗