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PubMed1977

In vitro polarization of dental amalgam in human saliva.

Potentiostatic anodic polarization techniques in Ringer's solution are commonly used for the evaluation of the corrosion resistance of dental amalgam. This in vitro method strives to simulate the in vivo electrochemical behaviour of amalgam in an electrolyte of natural saliva. Several types of dental amalgam were anodically polarized in natural saliva solutions and supernatant saliva solutions. The anodic polarization profiles are presented, as well as scanning electron micrographs and x-ray analysis of the corroded amalgam surfaces. These reveal corrosion products consistent with results found with previous artificial salivas as well as deposits possibly related to the organic component of natural saliva.

Copper↗

PubMed2006

Neurobehavioral effects of dental amalgam in children: a randomized clinical trial.

CONTEXT: Dental (silver) amalgam is a widely used restorative material containing 50% elemental mercury that emits small amounts of mercury vapor. No randomized clinical trials have determined whether there are significant health risks associated with this low-level mercury exposure. OBJECTIVE: To assess the safety of dental amalgam restorations in children. DESIGN: A randomized clinical trial in which children requiring dental restorative treatment were randomized to either amalgam for posterior restorations or resin composite instead of amalgam. Enrollment commenced February 1997, with annual follow-up for 7 years concluding in July 2005. SETTING AND PARTICIPANTS: A total of 507 children in Lisbon, Portugal, aged 8 to 10 years with at least 1 carious lesion on a permanent tooth, no previous exposure to amalgam, urinary mercury level <10 microg/L, blood lead level <15 microg/dL, Comprehensive Test of Nonverbal Intelligence IQ > or =67, and with no interfering health conditions. INTERVENTION: Routine, standard-of-care dental treatment, with one group receiving amalgam restorations for posterior lesions (n = 253) and the other group receiving resin composite restorations instead of amalgam (n = 254). MAIN OUTCOME MEASURES: Neurobehavioral assessments of memory, attention/concentration, and motor/visuomotor domains, as well as nerve conduction velocities. RESULTS: During the 7-year trial period, children had a mean of 18.7 tooth surfaces (median, 16) restored in the amalgam group and 21.3 (median, 18) restored in the composite group. Baseline mean creatinine-adjusted urinary mercury levels were 1.8 microg/g in the amalgam group and 1.9 microg/g in the composite group, but during follow-up were 1.0 to 1.5 microg/g higher in the amalgam group than in the composite group (P<.001). There were no statistically significant differences in measures of memory, attention, visuomotor function, or nerve conduction velocities (average z scores were very similar, near zero) for the amalgam and composite groups over all 7 years of follow-up, with no statistically significant differences observed at any time point (P values from .29 to .91). Starting at 5 years after initial treatment, the need for additional restorative treatment was approximately 50% higher in the composite group. CONCLUSIONS: In this study, children who received dental restorative treatment with amalgam did not, on average, have statistically significant differences in neurobehavioral assessments or in nerve conduction velocity when compared with children who received resin composite materials without amalgam. These findings, combined with the trend of higher treatment need later among those receiving composite, suggest that amalgam should remain a viable dental restorative option for children. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00066118.

Child↗

PubMed1991

Dental amalgam. Designs for research in human populations.

Questions have been raised about the safety of dental amalgam. The main point of contention is whether the mercury contained in dental restorations is released in sufficient quantities to pose a public health hazard. Most scientists agree that current evidence is not sufficient to show that amalgam restorations pose a general health threat. But researchers on both sides of this debate agree that much remains to be learned about any potential toxicity of dental amalgam--an issue serious enough to merit additional research.

Cohort Studies↗

PubMed1990

The effect of tin on the corrosion behavior of the Ag-Hg phase of dental amalgam and dissolution of mercury.

The anodic polarization behavior of the Ag-Hg matrix phase of dental amalgam (gamma 1) and the rate of mercury dissolution were examined as a function of the tin content. The objectives were to determine the effect of tin on the electrochemical behavior and dissolution of mercury and to provide evidence on whether tin dissolves in the gamma 1 phase or precipitates as a tin-rich phase. Anodic polarization curves were recorded for specimens of the gamma 1 phase containing 0-1.5% Sn and for the gamma 2 phase and a gamma 2-containing dental amalgam, in synthetic saliva. Mercury dissolved in synthetic saliva in 24 h was determined for the gamma 1 phase containing 0-1.0% Sn, with cold-vapor Atomic Absorption Spectrophotometry used for mercury analysis. Tin induced passive behavior of the gamma 1 phase and suppressed mercury dissolution. The passive gamma 1 phase did not exhibit a breakdown of passivity occurring at the gamma 2 phase. The results were consistent with the tin presence in gamma 1 in a solid solution, rather than in tin-rich precipitates, and indicated that at least 1.5% Sn can be dissolved in gamma 1 at 37 degrees C.

Corrosion↗

PubMed1983

Corrosion of the eta'(Cu-Sn) phase in dental amalgam.

Previous studies have shown preferential corrosion of the eta'(Cu-Sn) phase in high-copper dental amalgam both in vitro and in vivo, while samples of pure eta' have shown high corrosion resistance. To clarify this contradiction, samples of pure eta' crystals mixed with other phases were prepared and tested. Evaluation of the corrosion resistance was based on the results of coulometry at constant potential and potentiodynamic polarization. The corrosion susceptibility of eta' in the matrix of gamma 1(Ag-Hg) was considerably higher than the susceptibility of isolated eta'. The susceptibility of pure eta' also could be increased by plating it will small amounts of Hg. It was concluded that in dental amalgam, the presence of mercury in the phases surrounding eta' reduces its resistance to corrosion. Although eta' is more resistant to corrosion than gamma 2(Sn-Hg) which appears in low-copper amalgams, it is the least corrosion resistant major phase in high-copper amalgams and can suffer deterioration.

Copper↗

PubMed2003

Memory functions in persons with dental amalgam.

Memory and psychophysiological variables in persons with self-reported reactions to dental amalgam (amalgam patients: N=26) and in persons without such symptoms (controls: N=21) were compared. The groups were matched regarding age, education, and amount of amalgam. Wechsler Memory Scale-Revised was obtained for all subjects and compared to amalgam points in a dose-response design. The results demonstrated that amalgam patients function on the same level as the controls regarding memory variables, attention, concentration, and delayed recall. Psychophysiological measures of skin conductance as correlates of attention and basal memory functions, were compared in the two groups. No differences between the two groups were observed and no correlation between memory variables and exposure to amalgam could be detected.

Adult↗

PubMed2000

Mercury release from dental amalgam after treatment with 10% carbamide peroxide in vitro.

OBJECTIVES: The effect of 10% carbamide peroxide on mercury release from dental amalgams was assessed in vitro by using a cold-vapor atomic absorption Mercury Analyzer System. STUDY DESIGN: Samples of 4 commercial brands of dental amalgam, Megaloy (Dentsply/Caulk, Milford, Del), Mega+ (CFPM, Aulnaye, France), Nongama 2 (Silmet, Or Yehuda, Israel), and Valiant Ph.D. (Dentsply/Caulk, Milford, Del), were treated for 48 hours with 10% carbamide peroxide and compared with samples treated with phosphate buffer. RESULTS: Amalgam specimens exposed for 48 hours to 10% carbamide peroxide showed significantly higher concentrations of mercury in solution as compared with specimens treated with phosphate buffer (P <.001). Megaloy and Valiant Ph.D. yielded significantly higher mercury concentrations in solution than Mega+ and Nongama 2 (P <.001). Mega+ yielded significantly higher mercury concentrations in solution than Nongama 2 (P <.05). No significant differences were found in mercury concentrations in solution between Megaloy and Valiant Ph.D. CONCLUSIONS: Treatment with 10% carbamide peroxide bleaching agents caused an increase in mercury release from amalgam restorations, possibly increasing exposure of patients to its adverse effects. Amalgam brands differed in the amounts of mercury release after bleaching with carbamide peroxide.

Carbamide Peroxide↗

PubMedDate not supplied

Removal of dental amalgam and other metal alloys supported by antioxidant therapy alleviates symptoms and improves quality of life in patients with amalgam-associated ill health.

OBJECTIVES: The purpose of this study was to evaluate treatment of patients suffering from chronic ill health with a multitude of symptoms associated with metal exposure from dental amalgam and other metal alloys. SETTING AND DESIGN: We included 796 patients in a retrospective study using a questionnaire about symptom changes, changes in quality of life as a consequence of treatment and assessment of care taking. METHODS: Treatment of the patients by removal of offending dental metals and concomitant antioxidant therapy was implemented according to the Uppsala model based on a close co-operation between physicians and dentists. RESULTS: More than 70% of the responders, remaining after exclusion of those who had not begun or completed removal, reported substantial recovery and increased quality of life. Comparison with similar studies showed accordance of the main results. Plasma concentrations of mercury before and after treatment supported the metal exposure to be causative for the ill health. MAIN FINDINGS: Treatment according to the Uppsala model proved to be adequate for more than 70% of the patients. Patients with a high probability to respond successfully to current therapy might be detected by symptom profiles before treatment. CONCLUSIONS: The hypothesis that metal exposure from dental amalgam can cause ill health in a susceptible part of the exposed population was supported. Further research is warranted to develop laboratory tests to support identification of the group of patients responding to current therapy as well as to find out causes of problems in the group with no or negative results.

Adult↗

PubMed1991

Dental amalgam--the possible contribution to mercury burden in Greenland Inuit.

The possible contribution to the total mercury burden by dental amalgam among Greenland Eskimos has been studied in Nanortalik Health District. A total of 40 individuals have been tested, and no significant differences in whole blood mercury have been found between individuals with and without experience of dental amalgam. Higher values than previously reported for South-West Greenland have been found, mercury (Hg) concentrations reaching a median of 53 microgram Hg/l in males and 42.5 microgram Hg/l in females. A tendency towards covariation with the relative amount of local food items in the diet did not reach significance at a 5% level.

Body Burden↗

PubMed1983

Cyclic creep and fracture of dental amalgam.

The creep strain rate and fracture of several dental amalgams has been shown to be markedly dependent on the type of loading applied. Cyclic loading typical of the in vivo situation increases creep rates and reduces times to fracture when analysis is based on a Mechanical Equation of State. The cyclic strain rate enhancement over static loading is highest for conventional amalgam while the modern ternary alloys show the smallest increases.

Biomechanical Phenomena↗

PubMed1978

Stress/strain behavior of dental amalgams.

The stress/strain behavior at different strain rates and the creep rate of dental amalgams were evaluated and compared to the microstructure. The results indicate that substantial differences exist both in strength and strain at fracture. The strain at fracture for high strain rates was associated with the nature of the particle-matrix interface, in that amalgams with an interpenetrating interface exhibited some ductility, while amalgams with an abrupt interface exhibited practically no plastic deformation at fracture. The correlation between creep and slow compressive strength was verified and it was suggested that grain boundary sliding was the deformation mechanism in both cases.

Dental Amalgam↗

PubMed1999

Galvanic interaction between titanium and gallium alloy or dental amalgam.

OBJECTIVES: The objective was to examine in vitro the galvanic interaction between titanium and a high-copper dental amalgam or a gallium-based direct filling alloy at different area ratios, and to relate the observed interactions to the electrochemical characteristics of the alloys. METHODS: The tested materials were cast titanium, a single-composition, spherical high-copper amalgam, and a gallium-based direct filling alloy. Polarization curves were recorded. The galvanic couples were prepared at Ti/filling alloy ratios of 1:1, 2:1, 4:1 and 6:1. The couples were exposed to synthetic saliva at 37 degrees C and the galvanic currents and potentials were measured as a function of time. The results were analyzed by ANOVA and Tukey tests (p < or = 0.05). RESULTS: Freshly abraded titanium initially was anodic to both the amalgam and the gallium alloy, but the polarity reversed after a period of exposure. The galvanic potential and current density increased with the increasing Ti/alloy area ratio. The potential increase was smaller and the current increase larger for the Ga alloy than for the amalgam. The difference was consistent with the polarization characteristics. The galvanic current density was of the order of 10(-8) A/cm2 for the Ti/amalgam couple, and 10(-7) to 10(-6) A/cm2 for the Ti/gallium alloy couple. SIGNIFICANCE: The results show that the galvanic interaction between titanium and direct filling alloys is small. High copper dental amalgams should suffer little galvanic corrosion when in contact with Ti. For gallium direct filling alloys, the galvanic interaction may be more detrimental because of the inherently lower corrosion resistance.

Analysis of Variance↗

PubMed1982

In vitro corrosion and in vivo marginal fracture of dental amalgams.

The relationship between in vitro corrosion and in vivo marginal fracture of dental amalgams has been studied. The potentiodynamic cyclic polarization technique has been used to determine the in vitro corrosion index. The marginal fracture data have been obtained from previous clinical studies reported by three independent research groups. A linear regression analysis has been employed to determine the degree of correlation between in vitro and in vivo data. Depending on the method of corrosion index measurement and the source of clinical data, correlation coefficients (r) ranging from 0.82 to 0.94 (p less than .01) have been obtained.

Corrosion↗

PubMed1986

Accelerated corrosion analysis of dental amalgams.

The corrosion of powdered conventional and high Cu dental amalgam was studied in vitro under fixed conditions (100% oxygen, pH 4, and constant weak mechanical action). Results were retrieved from X-ray diffraction of samples of amalgam and solid corrosion products formed, in combination with recording of the HCl consumed to maintain the fixed pH. In the conventional amalgam no corrosion of gamma 1 occurred until all gamma 2 had corroded, whereas in the high Cu amalgam corrosion of gamma 1 occurred from the beginning, concurrent with corrosion of epsilon and eta'. Corrosion products found were AgCl, Hg2Cl2, CuCl2 X 3Cu(OH)2, and SnO2. The results may be interpreted as follows: in the conventional amalgam the matrix phase gamma 1 is anodically protected against corrosion as long as any gamma 2 remains; in the high Cu amalgam the least noble phases epsilon and eta' do not protect gamma 1 in a similar way.

Copper↗

PubMed1998

Effects of dental amalgam and its components of histamine release from human basophils and tissue mast cells.

Recent studies have shown that metal ions can be released from dental amalgam or other dental materials, and can cause toxic effects on various cells. In this study, the effects of amalgam-conditioned culture medium (ACCM), components of amalgam (Ag+, Cu2+, Sn2+, Hg2+) and dental composite-conditioned culture medium (CCCM) on histamine release from human blood basophils (healthy subjects, n = 3) and tissue mast cells (n = 3) were analyzed. ACCM and CCCM were prepared using either fresh or 6-weeks-aged specimens. Of the metal ions tested, Ag+, and Hg2+ were found to induce histamine release from basophils (Ag+, 0.33 mM: 83 +/- 11% vs Hg2+, 0.33 mM: 100% vs control medium: 5 +/- 5%) and mast cells (Ag+, 0.33 mM: 91 +/- 16% vs Hg2+, 0.33 mM: 99 +/- 1% vs control: 2 +/- 1%), whereas no effects were seen with Cu2+ and Sn2+. Neither ACCM from freshly prepared amalgam nor ACCM from 6-weeks aged amalgam, produced histamine release in basophils or mast cells. Inductively coupled plasma atomic emission spectrometry (ICP) revealed that the Ag(+)- and Hg(2+)-concentrations in ACCM were below the range in which histamine release occurred. Similar to ACCM, no effects on basophils or mast cells were observed with CCCM. In summary, our data show that distinct metal ions present in dental amalgam, can induce (toxic) histamine liberation from basophils and mast cells. However, the amounts of metal ions released from amalgam apparently were too low, to cause histamine release.

Basophils↗

PubMed1984

In vitro plaque formation on dental amalgam.

A previously described method for the study of in vitro microbial plaque formation on dental materials has been utilized to assess microbial adhesion and growth on five commercially available dental amalgams. Variations in both the amount and viability of the microbial plaques was found between the various types of amalgams.

Adenosine Triphosphate↗

PubMed1978

A study of the corrosion of dental amalgam using the ring-disk electrode.

The rotating ring-disk electrode technique has been applied to the study of anodic dissolution of dental amalgam in a simulated saline solution. The electroactive domains of the silver, tin, and mercury couples (the main constituents of the amalgam) were determined from current-potential curves obtained at a rotating gold-disk electrode in solutions containing salts of the respective metals. Subsequently, anodic currents were applied to a rotating amalgam-disk electrode and the soluble products produced were identified using a concentric gold ring electrode, i.e., using the rotating gold-ring, amalgam-disk electrode. Species generated at the amalgam disk are transferred to the gold ring by convective diffusion. Tin ions were found to be the only soluble species generated at the amalgam disk. No evidence for dissolution of other components was found. The selective dissolution of tin from the amalgam is also consistant with potential shifts observed in reptititve current-potential curves of an amalgam disk. This study provides a direct proof for the selective dissolution of tin during corrosion of dental amalgam in an in vitro environment.

Corrosion↗

PubMed1982

Surface roughness and porosity of dental amalgam.

The surface roughness of seven different products of dental amalgam was determined and the contribution of their porosity content and alloy particle size to that surface property was assessed. A significant correlation between roughness and porosity was found. In all amalgams the small voids were the most frequent. It was also found that the amalgam products which exhibited the highest frequency of big voids presented significantly higher surface roughness values. No significant correlation was found between roughness and alloy particle size.

Dental Alloys↗