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PubMed2003

Mercury and selenium in whole blood and serum in relation to fish consumption and amalgam fillings in adolescents.

Mercury and selenium in whole blood and serum of 245 17-year old Swedish adolescents were analysed. The relationships between these elements' concentrations and the consumption of fish as well as the number of dental amalgam fillings were studied. The geometric means (GM) of the mercury concentrations were 1.1 microg/L in blood and 0.43 microg/L in serum. The mean selenium concentration in blood was 110 microg/L and the GM of the serum selenium concentration 110 microg/L. Fish species with dietary restrictions due to elevated mercury Levels (i.e. pike, perch, pikeperch, burbot, eel and halibut) were consumed on average 0.7 times/month and fish species without such restrictions 4.1 times/month. Despite this comparatively low fish consumption, the adolescents' blood mercury concentrations were positively correlated with fish consumption. Of the adolescents, 39% had amalgam fillings (mean 2 +/- 1.5). Serum mercury was influenced by the number of amalgam fillings, by fish consumption, blood and serum levels of selenium and the residential area. Blood and serum selenium concentrations were not influenced by fish consumption, but were positively associated with the serum mercury concentration.

Adolescent↗
PubMedDate not supplied

Mercury exposure in dental practice.

Since elemental mercury is absorbed by dental professionals through direct skin contact or inhalation, the use of mercury in dental amalgam continues to be a controversial issue. In this study, the authors address the possible health risk of occupational exposure to mercury vapor in the dental office. The cytogenetic examination of leukocytes with alkaline comet assay and blood mercury levels with Atomic Absorption Spectrometer of dentists exposed to mercury vapor below 0.1mg/m(3) concentrations failed to find cytogenetic damage and related correlation. However, higher cytogenetic damage and blood mercury levels evaluated in controls from mercury intake by seafood consumption justifies additional study.

Adult↗
PubMed1985

The reaction zone around experimental amalgam alloy particles of Ag-Cu eutectic composition.

An electron microprobe was used to investigate the composition and microstructure of the reaction zone occurring around experimental particles of approximately Ag-Cu eutectic composition in two experimental dental amalgams. This study formed the basis for the examination, described in a subsequent paper, of the reaction zones in several commercially available amalgams. Techniques of phase composition analysis were further developed in order to identify and quantify the component phases in the regions of the reaction zone. The clumped, outer, more darkly shaded region of the zone contained predominantly eta 1 (Cu6Sn5) phase. The inner, more lightly shaded region of the reaction zone was found to contain substantial quantities of eta 1, gamma 1, a Cu-Hg phase and a Ag-Cu component.

Chemical Phenomena↗
PubMed1993

Nordic dentists' opinions on the safety of amalgam and other dental restorative materials.

The safety of amalgam and other restorative materials has caused concern among dental patients in recent years. The aim of this study was to obtain information on dentists' perceived competence in handling different filling materials and their opinions on the safety of these. A random sample of practising dentists in Denmark, Finland, Norway, and Sweden received a mail questionnaire in spring 1990. Answers were received from 1732 dentists (65%). The study showed that the respondents believed that their theoretic knowledge and clinical skills were generally at a high level regarding restorative materials. The risks of the side-effects of gold, ceramic materials, and glass ionomer were considered to be low by about 90% of the respondents. Amalgam was considered to be significantly more hazardous by the Swedish respondents than the others. Interestingly, composite was considered to be associated with a high risk of side-effects by about half of the dentists in all Nordic countries. The dentists' opinions were not found to be greatly influenced by their sex, age, or place of residence but rather by their country and service sector. Against the background of the present lack of scientific evidence on the hazardousness of amalgam or other restorative materials for patients' general health, these findings indicate that dentists are influenced by discussions in the mass media about dental treatment and materials and, of course, by the guidelines given by the health authorities in their own countries. Few dentists were shown to be concerned about occupational risks associated with the use of amalgam, and they had not had their own amalgam fillings replaced.(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude of Health Personnel↗
PubMed2005

High mercury emissions from dental clinics despite amalgam separators.

Mercury (Hg) as amalgam has been used as a dental filling material for more than 150 years. Thereby, dentists and their patients have been directly exposed to Hg, and the public and the environment indirectly exposed via Hg emissions from incinerators and Hg in waste water from households and dental clinics. Due to the toxic properties of Hg and bioaccumulation in biota of Hg emitted via dental clinic waste water, amalgam separators were introduced in Sweden in the 1980s. Although these amalgam separators in the certification process are required to remove at least 95% of incoming Hg in a standardized laboratory test, their efficiency in practical use has not been properly investigated. Here we present actual Hg emissions via waste water from 12 dental clinics equipped with the same type of amalgam separator based on sedimentation. All waste water was collected for four consecutive working days, initially at ordinary operating conditions and a second time after a thorough revision and cleaning of the discharge system. The results indicate that mercury emissions from dental clinics can be reduced by an improved design of the discharge system, a sensible use of high pressure water cleaning, and regular maintenance, including replacement of amalgam separators and filters at certain intervals. The study also indicates that banning Hg in dentistry is the one long-term way to stop Hg emissions from dental amalgam.

Dental Amalgam↗
PubMed1988

Determination of the rate of release of intra-oral mercury vapor from amalgam.

The experimental and analytical difficulties associated with the measurement of mercury vapor in the oral cavity are considerable. In the present paper, the objective was to measure the amount of intra-oral mercury vapor in subjects with amalgams, by means of two sets of equipment based on different functional principles. In addition, it was found that the type of mercury source prevalent in the oral cavity had to be evaluated. The measuring technique used to obtain correct results is discussed, and an evaluation of the conditions for the application of the measuring equipment available was made. It was found that the amount of mercury released from the oral cavity was time-dependent. Furthermore, the amount of mercury released with the time kept constant was almost independent of the pumping flow rate up to 8 L/min. It was found that the tissue, saliva, and the amalgam restorations were not depleted of mercury during the measuring time. The results of the Mercollector-Mercometer measurements carried out on seven subjects with nine or more occlusal surfaces restored with dental amalgam and on three subjects without any amalgam restorations revealed that the rate of mercury release was in the range 0.03-0.34 ng/sec in the former group and less than 0.01 ng/sec in the latter. Based on the experimental results and on theoretical considerations, it was concluded that the amount of mercury released per time unit is the only quantity measurable.

Adult↗
PubMed1977

Diffusion of mercury in HgSn8 (gamma2 phase).

The tracer diffusion coefficients of mercury in a Sn-Hg alloy (Sn 82.6 and Hg 17.4 wt.%; HgSn8 (gamma2 phase)2.6 and Hg 17.4 wt.%; HgSn8 [gamma2 phase]) were measured by the residual activity method at temperatures ranging from 35.5 to 95 degrees C. The Arrhenius equation for the mercury tracer was found to be Dv=2.10 X 10(-3) exp (-8.96 X 10(3)/RT) cm2/sec. The diffusivity of mercury in the three phases, the gamma (Ag3Sn), gamma1 (Ag2Hg3) and gamma2 (HgSn8) phase, that coexist in silver-tin dental amalgam have now been determined. Mercury diffuses fastest in gamma2 phase and slowest in gamma phase.

Dental Amalgam↗
PubMed2005

Group sequential testing in dental clinical trials with longitudinal data on multiple outcome variables.

In this article, methods are proposed for design and analysis of clinical trials that gather longitudinal data on multiple outcome variables. A valid test of the null hypothesis of no treatment group differences can be obtained for any choice of a working alternative hypothesis and a working covariance matrix for the outcome variables. Increased power can be achieved by accurate modeling of the true treatment effect and covariance structure. Implementation of the procedure is simple using existing software for generalized estimating equations. The procedure is an extension of the 'derived variable' technique (univariate analysis applied to a linear combination of the outcome variables) and also of O'Brien's generalized least squares test. The procedure is extended to allow sequential testing using an arbitrary division of the total type I error rate among repeated hypothesis tests. The methods are illustrated by the design of a study on the safety of dental amalgam fillings, which served as the motivation for the research.

Clinical Trials as Topic↗
PubMed1991

Biological monitoring of environmental and occupational exposure to mercury.

Biological monitoring was used to assess mercury exposure from occupational and environmental sources in a group of chloralkali workers (n = 89) and in a control group (n = 75). In the control group, the median value for blood mercury (B-Hg) was 15 nmol/l, that for serum mercury (S-Hg) was 4 nmol/l and that for urinary mercury (U-Hg) was 1.1 nmol/mmol creatinine. Corresponding levels in the chloralkali group were 55 nmol/l, 45 nmol/l and 14.3 nmol/mmol creatinine, respectively. In the control group, there were statistically significant relationships between fish consumption and both B-Hg and S-Hg values (P less than 0.001), whereas U-Hg correlated best with the individual amalgam burden (P less than 0.01). In the chloralkali group, the mercury levels in blood and urine were significantly related to the type of work (P less than 0.001) but not to the length of employment, to fish consumption or to the quantity of dental amalgam fillings. In both groups there were poor correlations between smoking or alcohol intake and the mercury levels in blood and urine. The results strongly suggest that fish is an important source of methylmercury exposure and that amalgam fillings are probably the most important source of inorganic mercury exposure among occupationally unexposed individuals. In the chloralkali group, mercury exposure from fish and amalgam was overshadowed by occupational exposure to inorganic mercury.

Adult↗
PubMed1999

Two-body in vitro wear study of some current dental composites and amalgams.

STATEMENT OF PROBLEM: Wear resistance of restorative materials is a major concern in clinical practice for restorations involving occlusion. The relatively poor wear resistance of dental composites in stress-bearing posterior situations has restricted even wider clinical application of this type of restorative material. PURPOSE: This in vitro study compared the relative wear resistance of a selection of current dental composites and amalgams under cyclic loading to explore the wear mechanisms operating on these materials and to assess their relative potential clinical wear resistance under variable masticatory loads. MATERIAL AND METHODS: A 2-body in vitro wear test was undertaken on a selection of 2 Ultrafine Compact-Filled composites, 1 microfilled composite, and 3 dental amalgams. An alternating sine curve load (0.5 to 15 N) was applied to the wear surface through a rotating countersample with a purpose-built system to simulate the variable loading pattern that occurs during mastication. RESULTS: Under conditions simulating the repetitive cyclic loading pattern that may occur intraorally in high stress occlusal contact situations, the Ultrafine Compact-Filled composites exhibited a delamination wear pattern and had a significantly lower wear resistance than the amalgams. By comparison, the microfilled composite (Silux Plus) displayed an improved wear resistance that was superior to some amalgams. Dispersalloy had the best wear resistance among the materials selected. CONCLUSION: The wear of Ultrafine Compact-Filled composite and microfilled composite differed and reflect different operative wear mechanisms. For amalgams, the size, shape, and composition of the particles had an effect on the wear resistance of the materials.

Analysis of Variance↗
PubMed1990

[Effects of amalgam fillings on the mercury concentrations in amniotic fluid and breast milk].

Human amniotic fluid was gained from 95 pregnant women by amniocentesis (group 1) and from 20 women during delivery (group 2). The concentrations of inorganic mercury in amniotic fluid as assessed directly by cold-vapor atomic absorption spectrophotometry (CV-AAS) averaged 0.29 +/- 0.1 microgram/l in group 1 and 0.86 +/- 0.25 microgram/l in group 2. Surface areas of dental amalgam fillings were also estimated in these women and ranged between 0 and 930 mm2. There was no correlation between the surface area of maternal amalgam fillings and the concentrations of inorganic mercury in amniotic fluid (r = -0.122 and -0.069, respectively). Furthermore, no positive correlation existed between amalgam fillings and the concentration of total mercury in maternal blood (4.48 +/- 2.33 micrograms/l) and in neonatal blood (3.28 +/- 1.57 micrograms/l) as measured by CV-AAS in group 2 (r = -0.4 and -0.12, respectively). Concentrations of total mercury were also measured by CV-AAS in the breast milk of 86 women, five to ten days after delivery. These concentrations averaged 1.9 +/- 1.6 micrograms/l and were also not significantly correlated to the maternal amalgam surface areas (r = 0.188). In conclusion, maternal amalgam fillings are of no importance for the mercury load of the fetus and the neonate.

Adolescent↗
PubMed1983

[Levels of lead, cadmium and mercury in the hair of inhabitants of the Nantes and Grenoble areas].

Lead, cadmium and mercury were measured in the air of 398 inhabitants of the Grenoble area and 341 inhabitants of the Nantes area. The hair was washed with hor solution of EDTA, dissolved in nitric acid and analyzed by electrothermal atomic absorption spectrometry. The average concentrations are 6,23 micrograms/g for lead, 0,40 microgram/g for cadmium and 1,06 microgram/g for mercury. There is no difference between found data of the two areas for lead and cadmium. Mercury levels are higher in the Nantes area. Lead content is higher in male hair than in female hair, but the difference is not significant. In the Grenoble area, mercury levels are higher in males than in females; the process is reversed in the Nantes area. We have found no relation between metal levels and age of persons, but lead content is high in the hair of people under ten. Artisans and mechanics have lead content higher than the general people, though exposed people to occupational risks is excluded. We have found to relation between metal in the hair and the size of the town. It seems that the use of tobacco is without influence. Mercury content is related to the eating of fish. It is not increased in the population because of dental amalgams.

Adolescent↗
PubMed1990

Clinical evaluation of occlusal glass ionomer, resin, and amalgam restorations.

The purpose of the study was to evaluate four materials (a glass ionomer (polyalkenoate) silver cermet, two composite resin restoratives and a high copper content dental amalgam) placed in either conventional Class I cavities or in modified odontotomy-enameloplasty-sealant (OES) fissure preparations. One experienced operator inserted 438 occlusal. Class I restorations in the posterior permanent teeth of 124 patients in a private dental practice. Restorations were assessed for bulk loss of material, surface voids and cracking, restoration margin fractures and staining, and surface staining and roughness, by using colour transparencies taken at baseline and at recalls for up to 3 years. The glass ionomer cermet was the most difficult material to handle and also gave the least satisfactory clinical result. Loss of material and surface voids were common in the cermet restorations with surface cracking or crazing being seen in 11.4 per cent of the restorations, especially in the larger, conventional Class I preparations. One posterior resin was more viscous and difficult to handle than the other resin and exhibited more surface voids. The amalgam alloy was used in Class I preparations only and showed more restoration margin fractures and surface staining than did the other three materials. However, there were no unsatisfactory clinical assessments given for either restoration margin fracture and staining, or surface staining and roughness for any of the materials. Patient acceptance of the modified OES fissure preparation was extremely good.

Adult↗
PubMed2003

Methyl mercury and inorganic mercury in Swedish pregnant women and in cord blood: influence of fish consumption.

We studied exposure to methyl mercury (MeHg) in Swedish pregnant women (total mercury [T-Hg] in hair) and their fetuses (MeHg in cord blood) in relation to fish intake. The women were recruited at antenatal care clinics in late pregnancy to participate in an exposure study of environmental pollutants. Fish consumption was evaluated using food frequency questionnaires including detailed questions on fish consumption. In addition, we determined inorganic mercury (I-Hg) and selenium (Se) in cord blood. On average, the women consumed fish (all types) 6.7 times/month (range 0-25 times/month) during the year they became pregnant. They reported less consumption of freshwater fish--species that might contain high concentrations of MeHg--during than before pregnancy. T-Hg in maternal hair (median 0.35 mg/kg; range 0.07-1.5 mg/kg) was significantly associated (R2 = 0.53; p < 0.001) with MeHg in cord blood (median 1.3 microg/L; range 0.10-5.7 microg/L). Both hair T-Hg and cord blood MeHg increased with increasing consumption of seafood (r = 0.41; p < 0.001 and r = 0.46; p < 0.001, respectively). Segmental hair analysis revealed that T-Hg closer to the scalp was lower and more closely correlated with MeHg in cord blood than T-Hg levels in segments corresponding to earlier in pregnancy. We found a weak association between Se (median 86 microg/L; range 43-233 microg/L) and MeHg in cord blood (r = 0.26; p = 0.003), but no association with fish consumption. I-Hg in cord blood (median 0.15 microg/L; range 0.03-0.53 microg/L) increased significantly with increasing number of maternal dental amalgam fillings.

Adult↗
PubMed1986

Hypersensitivity to mercury, nickel and chromium in relation to dental materials.

Three metals which are used in dental materials are recognized as causing sensitization sufficiently frequently to consider whether problems might arise from their use in dentistry. These metals are, mercury, nickel and chromium. Nickel is by far the commonest sensitizer, 10 per cent of women are allergic to nickel; sensitization usually occurs through jewellery or fasteners on articles of clothing. Chromium (as chromate) is a much less common sensitizer for several reasons. Sensitization only occurs through hexavalent salts of chromate and the degree of exposure of humans to these salts is much less than to either nickel or mercury. The true incidence of mercury sensitization is difficult to ascertain because many of the materials which were used for patch testing previously and on which statistics were based, contained unnecessarily high concentrations of mercury, and the pattern of mercury allergy is changing because many substances which contain mercury and were used frequently are not now employed. Although metallic mercury can sensitize the evidence would suggest that if dental amalgams ever cause people to become allergic to mercury, it is an extremely rare occurrence. Problems with mercury-containing amalgams in those sensitized are also rare, only 28 cases have been recorded in the literature. Thus, it is likely that at the present time sensitization to mercury is uncommon and decreasing. There is even less evidence that nickel or chromate in dental materials actively sensitize and it is exceptionally rare to have problems with these metals in a prosthesis in someone who is already sensitized.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromium↗
PubMed1993

The interval nature of an ordinal scale for measuring the marginal fracture of amalgam.

The clinical performance of amalgam alloys over time has been assessed by measuring the extent of marginal fracture of restorations made from these alloys. Scales of photographs of restorations exhibiting varying degrees of marginal fracture have been used to make these assessments. The purpose of this study was to determine the relationship between the ordinal scale numbers of five photographs composing a commonly used scale (Mahler and Marantz, 1979) and the average width in micrometers of marginal fracture of the restorations in the photographs of this scale. In addition, a comparison was made between parametric and non-parametric statistical methods when applied to marginal fracture data. The results showed that four of the five photographs of this scale demonstrated a significant linear regression with marginal fracture width (R2 = 0.997; p = 0.002). The last photograph of the scale, which proved to be an outlier, was not used in the regression and was accommodated by an extrapolation procedure. Using previously gathered clinical data on the marginal fracture behavior of five amalgam alloys, the use of parametric statistical procedures (ANOVA and Scheffé's multiple comparison test) proved to be more discriminatory than the use of nonparametric procedures (Kruskal-Wallis and Dunn's Multiple comparison test) when tested at the same overall confidence level. Thus, having a photographic scale of an interval nature removes any doubt about using the more powerful technique of parametric statistics to evaluate the marginal fracture behavior of dental amalgams.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗