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PubMed1995

Silver concentrations in human tissues. their dependence on dental amalgam and other factors.

Human tissue samples (liver, kidney cortex, 5 brain regions: grey matter of cerebrum, white matter of cerebrum, nucleus lentiformis, cerebellum, brain stem) from 173 decreased persons were analysed for silver (Ag) by GF-AAS (Graphite Furnace Atomic Absorption Spectrometry) and the results compared with the number of teeth with amalgam fillings and the concentration of inorganic mercury (Hg), which had been determined in the same tissue samples in a previous study. It was found that the mean Ag concentrations in liver and brain of adult females are approximately twice that of males. Moreover, the Ag concentrations, especially in the brain, depend possibly on age. To exclude these confounding factors as far as possible, the influence of dental amalgam and the correlation of Ag and Hg were evaluated only in a sub-group of 93 males, aged 11-50 years. In this sub-group statistically significant correlations were found between the number of teeth with dental amalgam and the Ag concentrations in the cerebral cortex and the liver. No such correlation was found for the kidney. Ag and inorg. Hg correlate well in this sub-group in the liver, but not in the cerebral cortex or the kidney. Individuals from this sub-group with (i) 0-2 and with (ii) more than 9 teeth with amalgam fillings show mean Ag concentrations (micrograms/kg in tissue wet weight, geom. mean) of 1.59 and 5.41 in the grey matter of cerebrum, 1.42 and 4.25 in the white matter of cerebrum, 1.53 and 4.89 in the nucleus lentiformis, 1.95 and 5.02 in the cerebellum, 1.05 and 3.27 in the brain stem, 3.40 and 8.15 in the liver and 0.42 and 0.44 in the kidney cortex. In contrast, comparing all individuals under investigation with only 0-2 teeth with amalgam no correlation between Ag and inorg. Hg could be found in liver, kidney cortex or cerebral cortex. These results show that amalgam fillings release Ag as well. Considering the different toxicokinetics of Ag and Hg it can be concluded that Ag is a reliable marker for the fact that the elevated concentrations of inorg. Hg found in tissues of individuals with amalgam fillings derive mainly from these fillings and not from other theoretically possible sources.

Adolescent↗

PubMed1980

Biocompatibility of dental amalgams in vitro during 52 week period.

Short term biocompatibility of biomaterials including various dental materials has been elucidated so far. When considering the practical cases of utilization of the biomaterials, it is known that they stay for quite a long period in situ once after brought into the living system. It seems, therefore, essential that long term biocompatibility of the materials should be clarified in order to provide better knowledge on various aspects of biocompatibility. The present paper deals with long term biocompatibility in vitro of common dental materials, dental amalgams.

Biocompatible Materials↗

PubMed2003

[10 years of observation by public health offices in Baden-Württemberg--assessment of human biomonitoring for mercury due to dental amalgam fillings and other sources].

Since 1992, in Baden-Württemberg, ten-year old children have been surveyed in the project "Sentinel Health Departments" to study their exposure to environmental pollutants and possible health effects. In the four study areas 1200 children have been investigated every year initially, since 1996 every second year. The data for mercury in body fluids are reported here. The decrease in the body burden of mercury as a result of the declining usage of dental amalgam fillings, was been verified. In 1992/93, of all the children who had been surveyed, the 95 percentile for the body burden of mercury was 3.1 microg/l and in 2000/01 1.35 microg/l. Also to be discussed is the reason why mercury-based cosmetic ointments seriously exceed the HBM-II-intervention-value. Because of using these ointments, concentrations of mercury in urine up to 1400 microg/l were found. A study within the project "Sentinel Health Departments" compared the concentrations of mercury in the urine of adults with those in blood and salvia. The results support the opinion that mercury in urine is appropriate for estimating the mercury uptake from dental amalgam fillings. It can be assumed that these results reflect the situation in the entire Federal Republic of Germany. The ten years' experience confirms that the concept of the "Sentinel Health Departments" is excellently suited to obtain data relevant for environmental health of children. Environmental health protection and the essential gathering of data for future health observation in Baden-Württemberg.

Adult↗

PubMed1992

Cytotoxicity of corroded gallium and dental amalgam alloys. An in vitro study.

The cytotoxicity of one gallium and three different dental amalgam alloys was assessed in a cell culture system. Two evaluation methods were used, the filter method and an extraction method. Before being tested, set specimens of the alloys were stored in 0.9% NaCl solution for 1 and 10 weeks, to corrode. The alloys showed various degrees of cytotoxicity, ranging from mild to marked. Differences were found between the two testing methods, but in most cases no major differences in cytotoxicity were found between the Ga alloy and the amalgams. The results encourage further study and development of the Ga alloy, which is mercury-free.

Biocompatible Materials↗

PubMed1991

Bonding of a light-curing glass-ionomer cement to dental amalgam.

In the clinical situation, the need may arise for placement of a glass-ionomer cement over an existing amalgam restoration. This study assessed the tensile bond strength of a recently developed light-curing glass ionomer (Vitrabond) to dental amalgam (Dispersalloy), with and without the use of Scotchbond dual cure as an intermediary. Amalgam adherend specimens were prepared, then aged in water at 37 degrees C for seven days. Immediately before being bonded, the amalgam surfaces were finished flat on 600-grit paper. Forty specimens were used for bonding in this condition, and another 40 were covered with a thin layer of Scotchbond, which was light-cured for 10 s. The glass-ionomer was applied to the adherend surface in two increments, each light-cured for 30 s. After being bonded, half the specimens were stored in water at 37 degrees C, while half were stored in an environment of 95 +/- 5% RH at 37 degrees C. The 24-hour tensile bond strengths, in MPa, were: for specimens stored in water, without Scotchbond 8.4 +/- 1.2, with Scotchbond 4.7 +/- 1.3%; and for specimens stored in 95 +/- 5% RH, without Scotchbond 9.2 +/- 2.1, with Scotchbond 4.6 +/- 1.5. The data were further analyzed by the Weibull distribution function. It was concluded that a strong reliable bond can be achieved between Vitrabond and set Dispersalloy, and that the use of Scotchbond as an intermediary is contra-indicated.

Contraindications↗

PubMed1998

[Mercury exposure from dental amalgam. Risk assessment and clinical evaluation].

Inorganic mercury is absorbed in small amounts from dental amalgam fillings. Exposure can be calculated by measuring the level of mercury in the blood or urine (u-Hg). The average u-Hg in Norwegians is approximately 2-3 micrograms/g creatinine (approximately 1-2 nmol/mmol creatinine). Classic signs of mercury poisoning occur in a fraction of long-term exposed subjects with u-Hg > 100 micrograms/g creatinine (56 nmol/mmol creatinine). Subtle effects (e.g. enzymuria, altered selenium metabolism, and changes in tremor spectra) have been reported in humans at average levels of 20-35 micrograms/g creatinine (approximately 11-20 nmol/mmol creatinine). There is widespread concern about possible adverse effects of mercury from amalgam fillings. Data on exposure-response relationships make it less likely that low-level mercury exposure from amalgam fillings should cause symptoms or physical signs. Studies of the association between symptoms and amalgam fillings have been negative. Patients with symptoms allegedly caused by mercury from amalgam should undergo thorough medical examination. Based on the patient's symptoms and physical signs adequate time should be allowed for careful recording of medical history, physical examination and relevant laboratory tests.

Dental Amalgam↗

PubMed2000

Resistance to mercury and antimicrobial agents in Streptococcus mutans isolates from human subjects in relation to exposure to dental amalgam fillings.

Resistance to cefuroxime, penicillin, tetracycline, and mercury is reported for 839 Streptococcus mutans isolates from 209 human study subjects. The MICs of these drugs did not differ for isolates from one dental amalgam group and two nonamalgam subsets: a group with no known exposure to amalgam and a group whose members had their amalgam fillings removed.

Adult↗

PubMed1983

The effect of tensile strain on corrosion of dental amalgam.

In vitro corrosion of two low-copper and three high-copper dental amalgams was examined using stressed and unstressed specimens. Stress was applied in tension; anodic polarization curves and polarization resistance were determined. In stressed condition, the passive current density was higher, and polarization resistance was lower. The changes are attributed mainly to the fracture of passive films by creep strain.

Chemical Phenomena↗

PubMed1997

Potential side effects of dental amalgam restorations. (II). No relation between mercury levels in the body and mental disorders.

A group of 50 consecutive patients, referred for self-reported complaints which they related to dental amalgam restorations, was compared with control patients matched by age, sex and postal zip code. All patients were subjected to a psychiatric examination and a set of rating scales and questionnaires, and the symptoms were related to the mercury levels in blood, urine and hair. A psychiatric diagnosis was established in 70% of the patients in the index group versus 14% in the control group. The prevailing symptoms were anxiety, asthenia and depression. Mercury levels in blood, urine and hair were similar among index cases and controls, and were far below critical levels of mercury intoxication. There was no correlation between mercury levels and the severity of the reported symptoms. Therefore, mercury was not a likely cause of the complaints. Instead, the reported symptoms were part of a broad spectrum of mental disorders.

Affect↗

PubMed1998

Cerebrospinal fluid protein changes in multiple sclerosis after dental amalgam removal.

A relationship between multiple sclerosis (MS) and dental silver-mercury fillings has been suggested by some investigators, but never proven. This study documents objective biochemical changes following the removal of these fillings along with other dental materials, utilizing a new health care model of multidisciplinary planning and treatment. The dramatic changes in photolabeling of cerebrospinal fluid (CSF) proteins following these dental interventions suggest CSF photolabeling may serve as an objective biomarker for monitoring MS. The clear-cut character of these changes should also encourage more research to better define this possible association between dental mercury and MS.

Cerebrospinal Fluid Proteins↗

PubMed1993

The level of mercury in human dental plaque and interaction in vitro between biofilms of Streptococcus mutans and dental amalgam.

Mercury levels (micrograms/mg dry weight) in dental plaque from amalgam and enamel surfaces in human subjects with amalgam restorations were (range, mean, SD) 0.5-1.31, 0.72, 0.34 and 0.01-0.54, 0.2, 0.19, respectively. The levels of mercury in plaque from amalgam surfaces were significantly higher than those from plaque on enamel (p < 0.001). No mercury was detected in plaque from subjects without amalgam restorations. The mean level of mercury in a 24-hour collection of plaque was 2 micrograms (median, 1.8 micrograms), an amount close to those calculated by other workers (1.2-1.7 micrograms) for the amount of mercury liberated in the mouth from amalgam restorations in 24 h. Freshly prepared amalgam liberated relatively large amounts of mercury into culture broth in the first 24 h of exposure; subsequently, the levels declined except in the presence of Streptococcus mutans. In vitro, biofilms of Streptococcus mutans facilitated the release of mercury from freshly prepared amalgam, in what appeared to be a cyclical fashion. Amalgam aged for two years did not release mercury, even when supporting the growth of an S. mutans biofilm. The resistance of aged amalgam was attributed to the presence of a passive tarnish layer. The mercury released by the biofilm had an effect on the composition of the biofilm. The biofilms on fresh amalgam had significantly lower levels of carbohydrate (p < 0.001-p < 0.01) and protein (p < 0.001-p < 0.02) than did biofilms on aged amalgam and on control stainless steel wires.

Adaptation, Physiological↗

PubMed1985

Creep-fatigue as a possible cause of dental amalgam margin failure.

Fracture of the margins is the most common cause of failure of dental amalgam restorations. Both corrosion and creep have been identified as possible contributors to this type of failure. The stresses that induce creep may arise from the continued setting expansion of the amalgam, the formation of corrosion products, mastication, or from the thermal expansion of the amalgam during ingestion of hot foods. The latter two are low-frequency cyclic stresses. The amalgams used in dentistry have fusion temperatures only about 40 degrees C above mouth temperature, and they experience grain boundary sliding during creep deformation. Since grain boundary sliding, low-frequency cyclic stresses, and a temperature near the fusion temperature of the alloy are prerequisites for so-called "creep-fatigue fracture", this type of fracture may contribute to amalgam margin failure. Amalgam made from seven different alloys was condensed into stainless steel dies. After being allowed to set for seven days, the specimens were thermally cycled between 4 degrees C and 50 degrees C for 500 and 1000 cycles. Amalgam margin integrity was evaluated by scanning electron microscopy both before and after each cycling period. The amount of margin fracture was calculated after 1000 cycles. Thermal cycling of amalgam restorations placed in stainless steel dies resulted in predominantly intergranular fracturing of the amalgam margins, indicating that creep-fatigue failure may be a significant contributor to in vivo margin fracturing.

Chemical Phenomena↗

PubMed1996

Cyclic voltammetry of dental amalgams.

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 degrees 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 Hg2Cl2 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 Sn2+ oxidation appeared at -0.4 V. When zinc was present, a Sn4+ 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 gamma 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.

Analysis of Variance↗

PubMed1996

Risk assessment in dentistry: health risks of dental amalgam revisited.

This paper reviews the basic methodology of risk assessment and describes the four steps involved, namely hazard identification, hazard evaluation, exposure evaluation, and risk estimation. The risk posed by the release of mercury vapor from dental amalgam restorations is used as an example to demonstrate the advantages and limitations of this process.

Adolescent↗

PubMed1996

Acute glomerulonephritis, Henoch-Schönlein purpura and dental amalgam in Swedish children: a case-control study.

The issue of adverse health effects from dental amalgam and the concurrent low-dose exposure to inorganic mercury have been scrutinized by several Swedish expert groups during the past years. Only rarely have amalgam fillings in children been related to health effects. Experimental studies in genetically disposed animals have shown that low doses of inorganic mercury can induce autoimmune glomerulonephritis. The present case-control study included 31 children with acute glomerulonephritis and 33 with Henoch-Schönlein purpura retrieved from an in-patient register for the period 1973-1992 at the county hospital in Halmstad, Sweden. The median age was 10 and 9 years, respectively, for the two diagnostic groups. Dental clinics reported amalgam burden of the patients during the year before the date of diagnosis. Corresponding data were obtained for three randomly selected controls for each case, drawn from the case records of the same dental clinics, with matching for age and sex. Odds ratios (95% confidence interval) were 1.42 (0.49, 4.11) for Henoch-Schönlein purpura, 0.59 (0.25, 1.38) for acute glomerulonephritis and 0.84 (0.40, 1.75) for both diseases combined. The results of this study did not indicate increased disease risk in relation to amalgam burden.

Adolescent↗

PubMed1994

Effect of selenium on mercury vapour released from dental amalgams: an in vitro study.

Wet corroded and air oxidized surfaces from different types of dental amalgams were used in this in vitro study. The mercury vapour released before and after standardized brushing with a conventional (ACTA) and an experimental selenium-containing toothpaste was examined. The results showed differences between the wet corroded and the air oxidized surfaces. High copper, non- gamma 2- amalgams, released more mercury vapour than the conventional one throughout the experiment. When the amalgam surfaces were brushed with the conventional toothpaste, an increase of the released vapour was noted. The use of the selenium containing toothpaste resulted in all cases, in significantly lower amounts of mercury vapour.

Analysis of Variance↗

PubMed1980

Time-temperature behavior for creep of dental amalgam.

From 0 to 24 hours at an initial static stress of 34.5 MPa and in the temperature range of 0 to 60 degrees C, the creep behavior of four different one-week-old dental amalgams was monitored in a recently developed mini-specimen creep apparatus. In most instances the behavior could not be described by a linear relationship. Therefore, the usefulness of calculating creep rate based upon only two times, i.e., 1 and 4 hours, must be questioned. On the other hand, the observed creep kinetics were found to follow accepted nonlinear models of dislocation/obstacles interactions which may be thermally activated.

Cold Temperature↗

PubMed2006

Dental amalgam and mercury levels in autopsy tissues: food for thought.

Eighteen cadavers from routine autopsy casework were subject to a study of tissue levels of total mercury in brain, thyroid, and kidney samples by atomic absorption. On these same cadavers, all dental amalgam fillings (the most important source of inorganic mercury exposure in the general population, according to the World Health Organization (WHO) were charted. Total mercury levels were significantly higher in subjects with a greater number of occlusal amalgam surfaces (>12) compared with those with fewer occlusal amalgams (0-3) in all types of tissue (all P < or = 0.04). Mercury levels were significantly higher in brain tissues compared with thyroid and kidney tissues in subjects with more than 12 occlusal amalgam fillings (all P < or = 0.01) but not in subjects with 3 or less occlusal amalgams (all P > or = 0.07).

Brain Chemistry↗