Reconsidering dental amalgam.
Explore the source record for details and available documents.
Dental Amalgam↗
SEARCH · PubMed Health
Results for “DENTAL AMALGAM”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Antimicrobial and mercury resistance in aerobic gram-negative bacilli in fecal flora among persons with and without dental amalgam fillings.
Antimicrobial resistance is more widespread than can be accounted for as being a consequence of the selection pressure caused by the use of antibiotics alone. In this study, we tested the hypothesis that a high mercury content in feces might select for mercury-resistant bacteria and thus for antimicrobial resistance linked to mercury resistance. Three subject groups with different exposures to dental amalgam fillings were compared. None of the subjects had taken antimicrobial agents during the three preceding months or longer. The group exposed to dental amalgam (n = 92) had 13 times more mercury in feces than the group that had never been exposed to amalgam (n = 43) and the group whose amalgam fillings had been removed (n = 56). No significant differences in either mercury resistance or antibiotic resistance in the fecal aerobic gram-negative flora of these subject groups were seen. The following antimicrobial resistance frequencies were detected with a replica plating method: > or = 1% resistance was seen in 40% of the subjects for ampicillin, 14% of the subjects for cefuroxime, 6% of the subjects for nalidixic acid, 14% of the subjects for trimethoprim, 19% of the subjects for sulfamethoxazole, and 25% of the subjects for tetracycline. The amount of mercury in feces derived from amalgam was not selective for any resistance factors in aerobic gram-negative bacteria, but antimicrobial resistance was widespread even among healthy subjects with no recent exposure to antibiotics.
Adolescent↗
[Influence of dental amalgams on the concentration of mercury and silver in biological fluids and hair (author's transl)].
The influence of the extraction and fixing of dental amalgams on the metallic concentrations of different biological samples was studied by atomic absorption spectrometry on a subject. The levels of mercury obviously increased in urine, saliva and slightly in blood, with a maximum on the second or third day after the intervention; on the other hand, in the hair, the increase was very low even at the end of 40 days. The urinary and salivary kinetics of silver were practically similar to the ones of mercury. The determination of silver in these fluids could reveal with more specificity the part of dental amalgams on the increase of the metallic biological concentrations. A study with 25 other subjects carrying amalgams permitted to put in evidence some factors facilitating a slight increase of the mercury contents of the saliva, urine and blood.
Dental Amalgam↗
Surface properties of dental amalgam: roughness produced by setting reaction.
During the setting of dental amalgam, silver-mercury (gamma1) and tin mercury (gamma2) intermetallic compounds (phases) are formed. Since these compounds have distinct crystalline forms, they may be discerned on the surface of a setting sample. Visual identification of these phases on polished and etched samples is often difficult and, hence, surface morphology studies have an advantage in following the stages of the setting reaction. The purpose of this investigation was to use high-resolution light microscopy to follow the course of the setting reaction. Amalgam specimens were triturated and condensed against glass plates under pressure. The sample surfaces were then photographed under a high-resolution metallographic microscope using oblique illumination. The roughness of four samples for each alloy type was determined with a surface profile analyzer at times between ten minutes and 23 hours after trituration. An electron microprobe was used to identify the gamma1 and gamma2 phases. The gamma1 phase had a polyhedramorphology, and the gamma2 crystals formed intermeshed smooth areas. During the setting reaction, the average times for the roughness to reach 95% of the final value were 189, 227, 96, 65, and 116 minutes after trituration for the various amalgam types studied. All alloys tested required polishing several hours after trituration.
Crystallography↗
In vitro lymphocyte proliferation test in the diagnosis of oral mucosal hypersensitivity reactions to dental amalgam.
Patch testing was carried out in 23 patients with oral lichenoid lesions (OLL) topographically related to dental amalgam fillings. Twelve patients displayed positive reactions to several mercury compounds, whereas 11 patients were negative. An in vitro lymphocyte proliferation (LyPro) test was carried out using different mercury compounds and other metal salts. Mercuric chloride and phenyl mercuric acetate caused positive proliferation in 3/12 patch test-positive and in 5/11 negative patients. One out of seven healthy control subjects had a positive LyPro result. The mean stimulation index (SI) values between the patient groups or compared with the control subjects did not differ significantly. Zinc, tin, copper or silver salts caused in vitro lymphocyte stimulation in most of the patients and in healthy control people. Total (14) or partial (4) replacement of amalgam fillings was carried out in 18 patients. Complete healing of lichenoid lesions was seen in 4/6 LyPro test-positive and in 5/10 patch test-positive patients at follow-up examinations 12 months after the replacement of amalgam fillings. The in vitro proliferation assay seems not to be a specific test for identifying the patients who would benefit from amalgam replacement.
Adult↗
An application of impedance techniques to corrosion research on dental amalgam.
AC impedance techniques are finding increasing application in corrosion research. It was our aim to introduce them as a method for the evaluation of the electrochemical behaviour of dental amalgam. The complex plane plots are large depressed semicircles representing the frequency dependence of the impedance and measured at the corrosion potential. Conventional dental amalgams, in a chloride medium, exhibit a current peak in the proximity of -250 mV (vs. SCE). The corresponding impedance spectra are rather complex and difficult to interpret. The high frequency part, however, can be fitted to a semicircle with its centre lying below the real axis. An evaluation of the corresponding 'charge transfer resistance' shows that it is inversely proportional to the corrosion current density.
Corrosion↗
Estimation of the phase distribution in dental amalgam with the electron microprobe.
The phase distributions of several dental amalgams have been determined by two methods: calculation from elemental analysis data obtained with the microprobe, and measurement of phase areas on backscattered electron photographs with the image analyzer. The results of these methods agree, in general, with the distributions predicted by the stoichiometric equations.
Chemical Phenomena↗
Corrosion rates of dental amalgam in Ringer solutions and artificial saliva.
Corrosion currents of dental amalgams in Ringer solution, Ringer lactate solution and an artificial saliva were determined as a function of flow rate using the linear polarization technique. The obtained results show that corrosion is far more intense in Ringer solutions than in saliva. Also, flow rate dependence is evident for Ringer solutions but not for saliva in the range investigated.
Corrosion↗
Shear bond strength of dental amalgam bonded to dentin.
The objective of this study was to determine the shear bond strength of dental amalgam bonded to dentin with adhesives. Four groups of 15 permanent posterior teeth were used in this study. The occlusal enamel of the teeth was removed to produce a flat dentin surface. The teeth were embedded in phenolic rings with acrylic resin. Vinyl polysiloxane ring molds 4 mm thick with 4.5 mm circular openings were attached to the exposed dentin surface. Adhesives applied to the dentin surfaces prior to amalgam placement and condensation included: Amalgambond, a 4-META/TBB-MMA, HEMA based system (A), Panavia EX, a modified phosphate ester of Bis-GMA luting system (P), and Ketac-Cem, a glass ionomer luting cement (K). A dentin bonding agent and composite resin restoration system (Scotchbond 2/Silux Plus) was included for comparison. The specimens were stored in 37 degrees C water for 7 days prior to testing. Shear bond tests were done in an Instron machine at a crosshead speed of 0.02 inches per minute. The data were analyzed by ANOVA at 5% level of significance. The differences in shear bond strengths of the four test groups were not statistically significant (P = 0.115). Fracture patterns of the bonded amalgams, examined by SEM, were adhesive in appearance for Groups A and K and cohesive for Group P.
Adhesives↗
Role of mucin and albumin in saline polarization of dental amalgam.
Studies into the electrochemical nature and corrosion behaviour of dental amalgam have indicated the need for an artificial saliva formula that will accurately simulate the electrochemical properties of natural saliva. Existing formulae have been based on inorganic saliva constituent concentrations, without accurate representation of organic constituents. Albumin and mucin were added to several dilutions of saline solution. The resulting solutions were used as electrolyte at 4 degrees and 37 degrees C for the potentiostatic anodic polarization of conventional amalgam. The presence of albumin and mucin did not appear to alter the major characteristics of corrosion profile. Examination of the current-time transient curves indicated, however, that the kinetics of the electrochemical reactions were delayed. Also, the open circuit potential was observed to shift to more active values with the addition of organic constituents, thereby creating a low current density region in the initial segment of the polarization profile.
Albumins↗
Mercury inductions in persons with subjective symptoms alleged to dental amalgam fillings.
This study was carried out to determine whether health disturbances alleged to mercury release from dental amalgam fillings, i.e. "amalgam disease", may be caused by an increased sensitivity to mercury (Hg). In the form of a double-blind test, 39 volunteers who themselves suspected "amalgam disease" inhaled small doses of mercury vapour (0.6-10 microg) or pure air in a random sequence. After the induction procedure, the test persons assessed whether they reacted or not, i.e. experienced increased illness or not. The test persons also registered the daily intensity of their various symptoms. Calculated on the whole population, there was no statistically significant difference between the number of reactions after inhalation of mercury vapour compared with after inhalation of air. Two subjects, however, reacted significantly more often to mercury vapour than to air. The results do not support that short-term exposure to low doses of Hg vapour in general promotes clinical illness in subjects who themselves suspect "amalgam disease". The deviating reactions presented by two test persons, however, may support the theory that occasional individuals can be sensitive to very low doses of Hg.
Administration, Inhalation↗
[Dental amalgam: a toxicological evaluation].
During the latest decades the use of dental amalgam has been discussed with respect to potential toxic effects of the mercury component. In order to evaluate potential risks from this practice the recent literature is reviewed. Corrosion of fillings results in liberation of mercury. The absorption from this source in the Danish population can be estimated to be one to five micrograms/24 hrs. This exposure level is far below that accepted in occupational exposure and far below the minimum toxic level. Investigation of placental transfer of mercury has not provided any reason to avoid using amalgam during pregnancy. Micromercurialism or metal syndrome is claimed to be related to amalgam fillings. This syndrome consists mainly of complaints from the central nervous system, but also from muscles, joints and the gastrointestinal tract. The symptoms are non-specific and the documentation of the existence of such a syndrome related to mercury exposure is weak. The symptoms reported can be due to other chemical exposures, but psycho-social conditions may also play an important role. Information on disappearance of symptoms after removal of fillings may be a result of a placebo effect, which may be suggested until controlled experiments are performed. For this reason the use of chelating therapy is not indicated. Allergic contact eczema observed in few individuals is the only problem documented in connection with the use of amalgam fillings.
Brain↗
Dynamic creep of dental amalgam as a function of stress and number of applied stress cycles.
Dynamic creep tests on specimens of dental amalgam gave a relationship between creep (epsilon), applied dynamic stress (sigma), and number of applied stress cycles (N) as epsilon = AN (m sigma + c) where A, m, and c are constants. This equation can be used to predict creep of amalgam at low levels of stress and extended times. The pattern of results produced for different types of amalgam indicates that the creep process is multifactorial in nature.
Chemical Phenomena↗
AC impedance measurements on high copper dental amalgams.
In recent years alloys with a high copper content were developed to improve the corrosion resistance of dental amalgam by elimination of the gamma 2 (Sn-Hg) phase. The purpose of the present investigation was to compare the electrochemical behaviour of high copper amalgams obtained from single composition amalgam alloys (Indiloy; Shofu, Dental Corp., Menlo Park, USA) with those that used the additive mode of copper alloying (Dispersalloy; Johnson & Johnson, East Windsor, USA).
Copper↗
Copper, zinc, and selenium in human blood and urine after injection of sodium 2,3-dimercaptopropane-1-sulfonate: a study on subjects with dental amalgam.
This study investigated the effects of a single dose of intravenously administered sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) on the essential elements copper, zinc, and selenium in human blood and urine. The possible role of dental amalgam was also addressed. Eighty individuals, divided in four groups according to the presence or absence of dental amalgam fillings and symptoms self-related to such fillings, were given DMPS (2 mg/kg body wt) and 500 mL Ringer's acetate intravenously. Urine and blood were collected prior to the injection, and thereafter at intervals over a 24-h period. Cu, Zn, and Se concentrations were determined by atomic absorption spectrometry methods. A statistically significant increase in the concentrations of Cu and Zn in urine was observed 30 and 120 min after the DMPS injection compared to the preinjection concentrations. The concentrations of Se were not affected. The cumulated excretion over 24 h after DMPS injection constitutes only from 0.1% to 0.7% of the body content of these elements. There was no effect of different amalgam statuses on Cu and Zn excretion. We found a temporary decrease (4-7%) in the concentrations of Cu, Zn, and Se in blood 15 and 30 min after DMPS, but this seems to be the result of dilution factors. Administration of a single dose of DMPS does not affect the body stores of the essential elements Cu, Zn, and Se.
Adult↗
Corrosion behaviour of high copper dental amalgams.
This study evaluated the corrosion behaviour of two high copper dental amalgam alloys [Dispersalloy (Dentsply-Caulk) and Tytin (Kerr)] in different electrolytes. Amalgam specimens were prepared, coupled to a copper wire, cemented into glass tubes and polished to a 600-grit finish. A corrosion cell was prepared using a carbon counter-electrode, a standard calomel electrode as the reference and amalgam as the working electrode. The alloys were tested in the following mediums at 37 degrees C: (i) artificial saliva based on Fusayama's solution (FS), (ii) artificial saliva with citric acid adjusted to pH 4.0 (FC) and (iii) 1% sodium chloride solution (SC). Corrosion potentials (E(corr)) and corrosion rates (I(corr)) were determined using potentiostatic and impedance spectroscopy methods. Data was subjected to anova/Scheffe's post hoc test at 0.05 significance level. For both alloys, the corrosion potential in FS was significantly greater than in SC. Corrosion potential of Tytin in FS and SC was also significantly greater than in FC. The corrosion rate of Dispersalloy in FC was significantly greater than in FS and SC. For Tytin, corrosion rate in SC was significantly greater than in FS and FC. Although no significant difference in corrosion potential/rate was observed between the alloys when tested in FS, significant differences were observed when electrochemical testing was carried out in FC and SC. The corrosion behaviour of high copper amalgam alloys are both material and environment dependent. Certain food substances may increase the corrosion of high copper amalgams.
Citric Acid↗
[Dental amalgam--filling material with future?].
On the basis of a literature survey there is a discussion about advantage and disadvantage of dental amalgam, possible alternatives and at least eventual dangers by intoxication of mercury. As result the amalgam were found without hesitation and classified as clinical suitable.
Dental Amalgam↗
Compressive strength of some polyalkenoates with or without dental amalgam alloy incorporation.
The present study compares the compressive strength after one week of some conventional glass-ionomer restorative materials with that of glass ionomers reinforced by the addition of ceramic-coated silver or dental amalgam alloy particles to the aluminosilicate glass powder. Apart from the commercially available Ketac Silver and Miracle Mix, experimental mixtures of Fuji II glass-ionomer powder, the old as well as the new version, with various amounts of either a spherical or lathe-cut amalgam alloy were investigated. For the conventional glass ionomers, the mean compressive strength based on all measurements amounts to 159.9 +/- 4.5 MPa. Both formulations of Fuji II have a comparable strength after one-week maturation. The compressive strength of Ketac Silver does not differ significantly from that of Ketac Fill or from that of the conventional glass ionomers investigated. The effect of admixing amalgam alloy on the compressive strength is found to be determined by the shape and the amount of the alloy particles. Moreover, both parameters are interactive with the formulation of the Fuji glass ionomer used for preparation of the mixture. The results indicate that when dental amalgam alloy is added to the glass ionomer, lathe-cut particles are to be preferred but only in an amount up to 20% by weight.
Analysis of Variance↗