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PubMed2001

Inhibition of human gelatinases by metals released from dental amalgam.

The interaction between metal ions and the oral environment is a major subject matter in dental research. Matrix metalloproteinases (MMPs) have been implicated in pathologic oral processes such as periodontal tissue destruction, root caries, tumor invasion and temporomandibular joint disorders. The aim of this study was to test the effect of metal ions released from dental amalgam on the major gingival gelatinolytic MMPs. Gingival human explants were cultured overnight in DMEM and the activity of secreted enzymes was analyzed by gelatin zymography in buffers conditioned with dispersed phase or concentional phase dental amalgams. The major enzymes present in conditioned media were characterized as MMP-2 and MMP-9 by immunoprecipitation. The proteolytic activities of MMP-2 and MMP-9 were strongly inhibited by dispersed phase amalgams conditioned buffers. Inhibition of MMP-2 and MMP-9 activities was partly prevented by the addition of 1,10 phenanthroline, a divalent metal chelator, to the amalgam conditioned buffers. Dental amalgam conditioned buffer also inhibited the degradation of denatured type I collagen by purified MMP-2 on liquid phase assays. These findings suggest that the activity of oral tissue MMPs may be modulated by metal ions released from dental amalgam.

Adult↗

PubMed2005

The effect of carbamide peroxide treatment on metal ion release from dental amalgam.

OBJECTIVES: There is concern that hydrogen peroxide generated by tooth bleaching agents may cause enhanced metal ion release (including mercury) from dental amalgam following contact. The aim of this in vitro study was therefore to investigate the effect of a carbamide peroxide (CP) based tooth bleaching gel on metal ion release from dental amalgam. METHODS: Dental amalgam discs were prepared according to the manufacturers' instructions. These were treated with either a 10% carbamide peroxide (CP) gel or a 0% CP gel for 24h. Discs were carefully wiped with cotton wool before immersion in distilled water (20 ml) for 24h at 37 degrees C. Following immersion, water samples were taken for metal ion release determination (Ag, Cu, Hg and Sn) using inductively coupled plasma mass spectrometry methods. The specimens were further evaluated for surface changes using scanning electron microscopy (SEM) and Talysurf surface roughness measurements. RESULTS: The differences in concentration of metal ions released after treatment with the 10% CP gel and a placebo gel treatment were not statistically significant (p>0.05). For example, mercury release following treatment with the 10% CP gel and the 0% CP gel was found to be 1.17(0.5) and 0.57(0.1)microgcm(-2), respectively. Roughness measurements for samples treated with the 10% CP gel and 0% CP gel were 2.23(0.47) and 1.74(0.16)microm, respectively, again showing no significant difference between groups (p>0.05). SEM images of the amalgam surfaces showed no apparent differences between treatments. SIGNIFICANCE: Treatment with a 10% CP gel did not significantly enhance subsequent metal ion release from dental amalgams compared to a control gel, contradicting previously published studies.

Carbamide Peroxide↗

PubMedDate not supplied

Physical and mental problems attributed to dental amalgam fillings: a descriptive study of 99 self-referred patients compared with 272 controls.

OBJECTIVE: The physical and mental symptomatology of 99 self-referred patients complaining of multiple somatic and mental symptoms attributed to dental amalgam fillings were compared with patients with known chronic medical disorders seen in alternative (N = 93) and ordinary (N = 99) medical family practices and patients with dental amalgam fillings (N = 80) seen in an ordinary dental practice. METHOD: The assessments included written self-reports, a 131-item somatic symptom checklist; Eysenck Personality Questionnaire, the General Health Questionnaire, and Toronto Alexithymia Scale. RESULTS: The dental amalgam sample reported significantly more physical symptoms from all body regions. Self-reports suggested that 62% suffered from a chronic anxiety disorder (generalized anxiety disorder or panic). Forty-seven percent suffered from a major depression compared with 14% in the two clinical-comparison samples and none in the dental control sample. Symptoms suggesting somatization disorder were found in 29% of the dental amalgam sample compared with only one subject in the 272 comparison subjects. One third of the dental amalgam patients reported symptoms of chronic fatigue syndrome compared with none in the dental control sample and only 2 and 6%, respectively, in the two clinical comparison samples. The dental amalgam group reported higher mean neuroticism and lower lie scores than the comparison groups. CONCLUSION: Self-referred patients with health complaints attributed to dental amalgam are a heterogeneous group of patients who suffer multiple symptoms and frequently have mental disorders. There is a striking similarity with the multiple chemical sensitivity syndrome.

Adult↗

PubMed1993

Urinary mercury level in Japanese school children: influence of dental amalgam fillings and fish eating habits.

The influence of dental amalgam fillings and fish eating frequency on the urinary mercury (Hg) level was evaluated in 1642 children (ages: 3-18) living in Tokyo. Geometric mean of the urinary Hg level was 1.9 microgram Hg/l and 1.9 micrograms Hg/g creatinine (Cr) for boys and 2.1 micrograms Hg/l and 2.0 micrograms Hg/g Cr for girls. Multiple regression analysis was conducted using: (1) urinary Cr concentration (only in the case of urinary Hg expressed as microgram Hg/l); (2) age; (3) gender; (4) number of dental amalgam fillings; and (5) fish eating frequency as independent variables. As a result, all the variables examined were significant and the explanatory powers (square of multiple correlation coefficient) of these variables were 17 or 7% for urinary Hg expressed as microgram Hg/l or microgram Hg/g Cr, respectively. Number of dental amalgam fillings or fish eating frequency explained only up to 1.5% of the total variance of urinary Hg. Contribution of Cr concentration, age and gender to urinary Hg level is also discussed.

Adolescent↗

PubMed1976

Phase identification of dental amalgam using transmission electron microscopy.

Dental amalgam specimens were polished and afterward etched by an acid iodine solution. The replicas were obtained by the vacuum coating technique. The electron micrographs indicated that it was possible to identify the silver-mercury (gamma1) and tin-mercury (gamma2) intermetallic compounds formed during amalgam setting.

Dental Amalgam↗

PubMed1997

Dissolution of mercury from dental amalgam at different pH values.

Dissolution of mercury from dental amalgam has been shown to be diminished by the formation of a tin oxide film on the surface of the mercury-rich gamma 1 phase (Marek, 1990b). Since tin oxides dissolve at low pH values (Deltombe et al., 1974), acidic conditions in the oral cavity may cause an increase in the mercury release. The purpose of this study was to determine the effect of acidity in the range of pH 1 to pH 8 on the rate of mercury dissolution in synthetic saliva from tin-free and tin-containing gamma 1 phase and two commercial dental amalgams. The tested hypothesis was that pH affects mercury dissolution only when a protective oxide film dissolves in an acidic environment. After exposures of the specimens for 2 hr or 24 hr in sealed glass bottles, the solutions were analyzed by flameless atomic absorption spectrophotometry for mercury and silver. The results have shown pH-independent mercury dissolution in the range of pH 3 to 8, and a much faster dissolution at pH 1. At all pH values, more mercury dissolved from the tin-free phase than from the tin-containing phase, and the rate of dissolution was lowest for the dental amalgams. The results were affected by the length of the test exposure. The pH independence in a wide range of pH values has been attributed to the atomic mechanism of mercury dissolution. The low rate of mercury dissolution from specimens containing tin has been explained by the formation of a barrier tin oxide film, which dissolved only at the lowest pH. Dissolution of silver at low pH values is believed to have accelerated dissolution of mercury from the tin-free gamma 1 phase. Variation of the dissolution rate with concentration of the dissolved species and kinetics of oxide film dissolution caused the effect of the exposure period.

Analysis of Variance↗

PubMed1989

Dental amalgam and mercury.

Mercury concentration in intraoral air and urine of seven females with dental amalgam was measured before and after intake of one hard-boiled egg. A considerable decrease in mercury concentration in intraoral air was found. Twenty women with about equal dental amalgam status, with or without subjective symptoms related to dental amalgam, were also studied. Mercury concentrations in intraoral air and urine were measured. For all the 27 women the basal intraoral air concentration of mercury ranged over 0.6-10.4 micrograms/m3 (median value 4.3 micrograms/m3). This corresponds to a release of 0.02-0.38 ng/s (median value 0.16 ng/s). In urine, the mercury concentration varied from less than 0.8-6.9 micrograms/g creatinine (median value 1.9 microgram/g creatinine). Data from both parameters were significantly correlated to the total number of teeth areas with dental amalgam. Protein values in urine indicated no renal damage. Maximum concentrations of mercury vapour in intraoral air for the 27 women who had chewed chewing gum for 5 min varied between 2-60 micrograms Hg/m3 (median value 19 micrograms Hg/m3). This corresponds to 0.07-2.20 ng Hg/s and a median value of 0.70 ng Hg/s.

Adult↗

PubMed1994

Release of elements due to electrochemical corrosion of dental amalgam.

The corrosion pattern of dental amalgam in aqueous media was interpreted theoretically by means of log(ai/a(ref))-pe diagrams. The definitions on which the diagrams were based were given, and their features were described. All sparingly soluble compounds which were expected to be formed in reactions with the solvents considered were listed. All the corrosion products reported in the current literature were found to be formed, and the conditions for their formation were established. It emerged that it was necessary to exclude other sparingly soluble compounds with theoretically might be formed. Two compounds, CuSCN and AgSCN, which have not been reported previously were found to be possible corrosion products. Corrosion products containing mercury compound cannot be formed on amalgam restorations with no metallic contact with other materials.

Copper↗

PubMed1980

Corrosion test for dental amalgam.

A corrosion test for dental amalgam, based on controlled potential coulometry, provides an index of corrosion susceptibility. A special cell was designed, and optimum test conditions were determined. The test can be used for the rating of amalgams, and in studies of the effect of variables on the corrosion resistance.

Chemical Phenomena↗

PubMed2000

Dental amalgam and mercury in dentistry.

Mercury in dentistry has re-emerged as a contentious issue in public health, predominantly because so many people are inadvertently exposed to mercury in order to obtain the benefits of dental amalgam fillings, and the risks remain difficult to interpret. This commentary aims to examine the issues involved in public policy assessment of the continued use of dental amalgam in dentistry. More than 30 per cent of Australian adults are concerned about mercury from dental amalgam fillings but only a small percentage report having their amalgam fillings removed. The placement of dental fillings nearly halved between 1983 and 1997, but many millions of dental amalgam fillings exist in the Australian community. These fillings release mercury (mercury vapour or inorganic ions) at a low level (about 2-5 micrograms/day in an adult). Evidence on the health effect of dental amalgams comes from studies of the association between their presence and signs or symptoms of adverse effects or health changes after removal of dental amalgam fillings. More formal risk assessment studies focus on occupational exposure to mercury and health effects. Numerous methodological issues make their interpretation difficult but new research will continue to challenge policymakers. Policy will also reflect prudent and cautious approaches, encouraging minimization of exposure to mercury in potentially more sensitive population groups. Wider environmental concerns and decreasing tolerance of exposure to other mercury compounds (for example, methylmercury in seafoods) will ensure the use of mercury in dentistry remains an issue, necessitating dentists keep their patients informed of health risks and respect their choices.

Adult↗

PubMed1998

Equilibrium vapour pressure of mercury from dental amalgam under loading conditions.

Earlier studies have failed to establish a consensus on the amount of mercury vapour released from dental amalgam restorations. The purpose of this study was to accurately and quantitatively measure the equilibrium mercury vapour pressure from dental amalgam. The vapour pressure was measured using a quartz crystal microbalance as a function of the load from 0-5.4 MPa. Auger spectra were collected of the as-formed and argon ion sputter cleaned dental amalgam surface. For the as-formed surface the mercury vapour density is zero with no load and increases to 0.6 microg m(-3) at 5.4 M Pa. Following cleaning the mercury, vapour density increased to a maximum value of 15 microg m(-3). The Auger spectra of the as-formed surfaces were dominated by features associated with carbon and oxygen. These spectral results in concert with the mercury vapour density measurements indicate that the oxide film on the as-formed surfaces inhibited the release of mercury vapour. The results of this experiment provide an upper limit for the amount of mercury vapour released by dental amalgams. Under conditions simulating the oral cavity this value would be reduced by oxides that form on the surface of dental amalgam restorations.

Dental Amalgam↗

PubMed1992

Interactions between dental amalgams and the oral environment.

Dental amalgam fillings interact in a complex way with the environment in the oral cavity as they are subjected to chemical, biological, mechanical, and thermal forces. These forces change the restoration's appearance and properties, while metal ions, amalgam debris, non-metallic corrosion products, and mercury vapor are released into the oral cavity. The phenomena and conditions that affect the amalgam/environment interaction include the chemistry and biochemistry of the environment, formation of biofilms on the amalgam surfaces, existence of localized corrosion cells, galvanic contacts with other metallic restorations, abrasion during mastication, and synergistic effects of the different forces. Corrosion processes result in a degradation of the functional amalgam properties, while tarnishing reactions cause discoloration. Corrosion degradation of amalgam fillings is due mainly to localized corrosion cells in pores and crevices. Corrosion on occlusal surfaces is accelerated by abrasion during mastication, which removes the protective surface films. The average total amounts of metal species, including mercury, released per day in vivo from a restoration have not been determined. Much of the reported indirect evidence for high mercury release rates is either unreliable or controversial. A more detailed investigation is needed and will require the development of more sophisticated techniques of sampling in vivo, as well as both experimental and theoretical modeling in vitro.

Copper↗

PubMed1990

Maternal-fetal distribution of mercury (203Hg) released from dental amalgam fillings.

In humans, the continuous release of Hg vapor from dental amalgam tooth restorations is markedly increased for prolonged periods after chewing. The present study establishes a time-course distribution for amalgam Hg in body tissues of adult and fetal sheep. Under general anesthesia, five pregnant ewes had twelve occlusal amalgam fillings containing radioactive 203Hg placed in teeth at 112 days gestation. Blood, amniotic fluid, feces, and urine specimens were collected at 1- to 3-day intervals for 16 days. From days 16-140 after amalgam placement (16-41 days for fetal lambs), tissue specimens were analyzed for radioactivity, and total Hg concentrations were calculated. Results demonstrate that Hg from dental amalgam will appear in maternal and fetal blood and amniotic fluid within 2 days after placement of amalgam tooth restorations. Excretion of some of this Hg will also commence within 2 days. All tissues examined displayed Hg accumulation. Highest concentrations of Hg from amalgam in the adult occurred in kidney and liver, whereas in the fetus the highest amalgam Hg concentrations appeared in liver and pituitary gland. The placenta progressively concentrated Hg as gestation advanced to term, and milk concentration of amalgam Hg postpartum provides a potential source of Hg exposure to the newborn. It is concluded that accumulation of amalgam Hg progresses in maternal and fetal tissues to a steady state with advancing gestation and is maintained. Dental amalgam usage as a tooth restorative material in pregnant women and children should be reconsidered.

Animals↗

PubMed1978

Stress relaxation of dental amalgam alloys.

Short-term stress relaxation of four dental amalgam alloys was studied. Test materials included two conventional lathe-cut restoratives, a spherical alloy, and a dispersed phase product. Specimens were 24-hr-old 4 X 8-mm cylinders. The specimens were compressed and held at constant strain on development of a stress (So) of 28 MN/m2. Subsequent stress relaxation (Dt) was recorded for 60 sec. Data were obtained at eight nominal temperatures between 0 and 55 degrees C. Over the experimental temperature range, fractional stress losses at 60 sec (Dt/So/60) for specimens made from lathe-cut alloys increased from 10% to 58%. The spherical material and the dispersed phase alloy showed fractional stress losses (Dt/So/60) ranging from 9% to 47% and 9% to 31%, respectively. It would appear that particle morphology and alloy composition affect stress-relaxation behavior of dental amalgam. Stress decay patterns enhance significantly the mechanical characterization of amalgam alloys.

Dental Amalgam↗

PubMed2000

Protective effect of Copalite surface coating on mercury release from dental amalgam following treatment with carbamide peroxide.

The effect of Copalite coating on mercury release from dental amalgam following treatment with 10%, 20%, 30% and 40% carbamide peroxide was assessed in vitro, using a cold-vapour atomic absorption Mercury Analyzer System. Eighty samples of dental amalgam were automatically mixed in a dental amalgamator and condensed into silicon embedding molds. Forty amalgam samples were coated with three uniform layers of Copalite intermediary varnish and the other 40 samples were left uncoated. The coated and non-coated amalgam samples were exposed for 24 h to 10%, 20%, 30% or 40% carbamide peroxide preparations and compared with samples exposed to phosphate buffer. In the non-coated samples a significant increase of mercury concentration in solution was found following exposure to all carbamide peroxide preparations tested. Mercury concentration was directly related to carbamide peroxide concentration. In the Copalite-coated samples, significantly lower concentrations of mercury in solution were found as compared to the non-coated samples (P < 0.01). In conclusion, exposure of amalgam restorations to 10%-40% carbamide peroxide-based bleaching agents increased the mercury release. Pre-coating of the external amalgam surfaces with Copalite significantly reduced the release of mercury.

Analysis of Variance↗

PubMed1991

Thermal effect on the dissolution of mercury from two dental amalgams.

Various factors affect dissolution of mercury from dental amalgams. In this study we examined the effect of temperature on the release of mercury from two dental amalgams, namely an admixed high-copper amalgam (Contour) and a new tin- and copper-free amalgam (Composil). Ten cylindrically-shaped specimens of each type of amalgam were used in this investigation, and were divided into two equal groups. The five specimens in each group were each incubated in 10 ml purified water at either 37 degrees C or 60 degrees C, with a change of water every 24 h over an 8-day period. The quantity of mercury released from each amalgam specimen during each incubation period was expressed as micrograms cm-2 24 h-1. The amount of mercury released was estimated by cold-vapour atomic spectrometry. The results demonstrate that specimens incubated at 60 degrees C released significantly larger amounts of mercury than specimens incubated at 37 degrees C for both types of amalgam. The release of mercury by Composil was significantly greater than that by Contour (P less than or equal to 0.0001) for both temperatures studied. Raising the incubation temperature caused a disproportionate increase in mercury release from Composil compared to Contour.

Copper↗

PubMed1991

Significance of hydrogen ion concentration on the dissolution of mercury from dental amalgam.

The potential risks of mercury dissolution from dental amalgam have long been recognized. This study examined the effect of hydrogen ion concentration on the release of mercury from two dental amalgams: an admixed high-copper amalgam and a new tin- and copper-free amalgam. Specimens of each type of amalgam were incubated citric acid buffer of pH 2.5 or pH 7.0. Results showed that, for both types of amalgam, specimens incubated at pH 2.5 released statistically significantly greater (P less than .0001) quantities of mercury than did specimens incubated at pH 7.0. Release of mercury from the tin- and copper-free amalgam was also statistically significantly greater (P less than .0001) than that of the higher-copper amalgam at both pH levels.

Citrates↗

PubMed1980

Colorimetric determination of gamma 2 phase in dental amalgam.

A new quantitative colorimetric test for the gamma 2 phase of dental amalgam, developed by Kropp, has been used to examine a number of the newer "low gamma 2" dental amalgam alloys. The original method has been modified in that the wavelength at which the color was read was changed from 578 nm to 700 nm. Of the dental amalgams tested, Tytin and Caulk Ease had the lowest gamma 2 phase content after 24 hours. Kropp's colorimetric method for gamma 2 phase determination is simple, quick, and convenient and requires relatively simple equipment, namely a colorimeter. However, for general use, a more convenient quantitative reference standard needs to be developed.

Chemical Phenomena↗