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PubMed1982

Cu2O and CuCl2 . 3Cu(OH)2 corrosion products on copper rich dental amalgams.

In addition to Sn-rich corrosion products found in conventional amalgams, Cu-rich amalgams also form Cu-containing corrosion products. The nature of these Cu-rich products was investigated by immersion of samples of 13 Cu-rich amalgam systems in Ringer's solution for prolonged periods. SEM/EDS and x-ray diffraction studies were used to identify the compounds formed and their morphology. Two products were identified: Cu2O, a red product, and CuCl2 . 3Cu(OH)2, a green product.

Copper↗
PubMed1997

Allergic disease, immunoglobulins, exposure to mercury and dental amalgam in Swedish adolescents.

High-dose exposure to inorganic mercury in man can influence the immune system and in rare cases cause immune-related disease. Some experimental animals also react with autoimmunity after low doses of inorganic mercury. Glomerulonephritis and an increased formation of immunoglobulin type E (IgE) are characteristic of these reactions. A recent study of 15-year-old adolescents demonstrated an association between immunoglobulin type A (IgA) and mercury concentration in plasma (P-Hg). There was also an association between allergic disease and IgA levels. The present study included 54 male and 23 female 19-year-old students who were recruited from a cohort that had been previously defined in a survey of allergic disease. Of the students, 39 (51%) had asthma, allergic rhinoconjunctivitis or eczema. Similar amalgam burden and P-Hg levels were observed in students with (n = 39) and without (n = 38) allergic disease (P = 0.48 and P = 0.98, respectively). As expected, IgE levels were significantly higher in the group with allergic disease (P = 0.006), but there was no association between P-Hg and IgE. The P-Hg levels were very low (median 1.50 nmol/l) and correlated significantly (r = 0.31) with the small number of amalgam surfaces (P = 0.007). Thirty-seven students had no amalgam fillings. P-Hg levels did not associate significantly with IgA, but did so with IgG2 (r = 0.33; P = 0.003). No conclusive correlation was observed between IgG2 and amalgam fillings. The findings of this study in 19-year-old subjects differ from earlier data obtained in a sample 4 years younger. The possibility of chance in the association between P-Hg levels and IgG2 must, however, be considered.

Adolescent↗
PubMed1980

Surface roughness of two dental amalgams after various polishing techniques.

1. In comparison with standard polishing after 24 hours, no advantage is gained by using an abrasive paste after 10 minutes. Polishing after 24 hours produced a significantly smoother surface for both amalgam alloys on both the simulated proximal and occlusal surfaces. 2. The standard polishing procedures after 24 hours produced a smoother surface than any of the immediate finishing procedures tested. 3. The high-copper amalgam was signijficantly rougher with initial carving and immediate finishing, but surfaces of both alloys were equally smooth when polished after 24 hours. 4. Both amalgam alloys, when condensed against a new matrix band lacked smoothness when compared to the surfaces obtained by finishing after 24 hours. 5. There was a high correlation between arithmetic average roughness and average maximum peak height as quantitative measurements of surface texture.

Chemical Phenomena↗
PubMed1984

Dynamic loading of dental amalgam and effects upon electrochemistry and microstructure.

The stress vs. cycles (S-N) behavior for four amalgams is reported. At 10 cycles/min and for 37 degrees C air and artificial saliva environments, linear regression lines fit the data with high correlations between 10(2) and 10(4) cycles. Significance at 50% exists between the environments and with saliva decreasing failure resistance. The open circuit potential (OCP), the OCP-time transients at constant anodic currents, and the cyclic voltammetry all exhibit changes with loading. With static loading the OCP decreases, while with dynamic loading the OCP exhibits a sinusoidal pattern and a pattern with two maxima and two minima after the loading has progressed and which continues up until failure. The maximum anodic current in voltammetry increases with continual potential cycling (or load cycling), while decreases when performed without loading. The application of anodic currents to the amalgams has, however, not significantly reduced the number of cycles to failure, nor has the application of cathodic currents increased the number of cycles. Rearrangement and coalesence of voids takes place with loading and with microcracking forming preferentially between them. Crack propagation occurs predominantly within the gamma-1 matrix.

Air↗
PubMed2003

Placental transfer of mercury in pregnant rats which received dental amalgam restorations.

Mercury vapor released from one, two and four amalgam restorations in pregnant rats and mercury concentrations in maternal and fetal organs were studied. Dental treatment was given on day 2 of pregnancy. Mercury concentration in air samples drawn from each metabolism chamber with a rat were measured serially for 24 h on days 2, 8 and 15 of pregnancy. On each day of pregnancy, the amount of mercury in 24 h air samples was in proportion to the amalgam surface areas. Linear regression analysis showed relatively high correlation coefficients between the mercury content and amalgam surface areas, and the coefficients were statistically significant. A highly significant correlation was also found between the number of amalgam fillings and their surface areas. Mercury concentrations in major maternal organs with one, two and four amalgam fillings tended to increase with the increasing amalgam surface areas. Spearman's rank correlation test revealed significant correlations in the brain, liver, kidneys and placenta but not in the lung. Furthermore, significant correlations were also found between the mercury concentrations in all maternal organs and the amount of mercury in 24 h air samples on day 15 of pregnancy. Mercury concentrations in fetal brain, liver and kidneys were much lower than those of the dams but liver and kidneys showed positive correlations between the mercury content and maternal amalgam surface areas. Similar correlations were observed between the mercury concentrations in fetal organs and the amount of mercury in 24 h air samples on day 15 of pregnancy. In fetal brain, no significant correlations were found between either maternal amalgam surface areas or the amount of mercury in 24 h samples on day 15 of pregnancy but significant uptake of mercury was found in the samples from the dams given four amalgam fillings. The results of the present study demonstrated that mercury vapor released from the amalgam fillings in pregnant rats was distributed to maternal and fetal organs in dose-dependent amounts of the amalgam fillings.

Animals↗
PubMed1987

The microstructural basis of creep of gamma 1 in dental amalgam.

A previous study has shown that the addition of small amounts of tin to gamma 1 leads to the formation of a SnHg intergranular precipitate. The purpose of this study was to determine the effect of this precipitate on the creep of gamma 1. Two groups of samples were investigated. Group I included a series of gamma 1 samples with 0, 1, 2, and 3 wt% Sn fabricated by a sintering technique at 55 degrees C and 125 mN/m2 for 72 h. Group II contained the same samples as in Group I that were further annealed at 60 degrees C for 2000 h. Annealing was carried out to allow gamma 1 grain growth and equilibrium distribution of Sn at grain boundaries. Creep tests were conducted according to the American Dental Association Specification 1. The microstructures of all samples were characterized by scanning electron microscopy. The creep of gamma 1 was found to be controlled by the intergranular precipitate when the Sn concentration was above 1%. For a specific concentration of Sn, i.e. the intergranular precipitate, creep was dependent on the distribution of Sn and not on the gamma 1 grain size. The more nearly continuous precipitates found in annealed samples favoured higher creep.

Chemical Phenomena↗
PubMed2001

Mercury uptake and kinetics after ingestion of dental amalgam.

The aim of the present study was to investigate the G-1 uptake of mercury (Hg) after intake of a single dose of amalgam-Hg, followed by pharmacokinetic analysis of the data. Eleven volunteers without amalgam fillings ingested 1.00 g amalgam powder. Hg in plasma vs. time was analyzed with a two-compartment model by means of mixed-effects modeling. A fraction of the absorption rate of Hg to the central compartment was inversely proportional to the plasma ferritin levels. The population mean half-life of the terminal phase of Hg in plasma was 37 days, with a considerable standard deviation in the population. The absorbed fraction of the administered dose was estimated to be about 0.04%. It is concluded that the G-1 uptake of Hg is of quantitative importance during dental treatment.

Administration, Oral↗
PubMed1995

Bacterial adhesion to dental amalgam and three resin composites.

OBJECTIVES: The ability of three oral bacteria to adhere to hydrophobic amalgam (water contact angle 60 degrees) and hydrophobic resin composites (Prisma-AP.H 56 degrees. Herculite XRV 82 degrees and Z100 89 degrees) was compared using an in vitro assay. METHODS AND RESULTS: Following preincubation of the materials with human saliva, X-ray photoelectron spectroscopy showed the surfaces to adsorb carbon and nitrogen-containing compounds in a conditioning film that appeared to block the detection of Na and others in 2100 resin. Hg and Ag in amalgam, Si and Zn in Prisma AP.H resin and Ag and Na in Herculite resin. The precoating of the substrata by a proteinaceous conditioning film led to decreased binding of viable cells of Streptococcus sanguis CH3, Streptococcus salivarius HB and Actinomyces viscosus WG as compared with the adhesion to bare composites. With and without salivary coating, there was a correlation between increased bacterial hydrophobicity and increased retention on the substrata. However, there was no statistical difference in binding to the amalgam compared with the resin composites. In vitro studies showed that the bacteria autoaggregated in the presence of saliva. CONCLUSION: The results indicate the potential ability of normal oral flora to colonize resin composite.

Actinomyces viscosus↗
PubMed2003

[Corrosion of titanium in presence of dental amalgams and fluorides].

AIM: The aim of this study was to evaluate the behaviour of titanium (Ti) in precipitant condition, and more precisely the resistance against corrosion of Ti in presence of fluorides and the electrochemical interaction between Ti- amalgam couples in fluorinated solution. METHODS: The experimental test was made with the use of an electrochemical cell. The following materials were tested: commercially pure Ti and 2 types of amalgams, the Persistalloy (Prs) and the IQC. Palladium (IQC.P). The free corrosion potential of Ti and the amalgams, the polarization curves of both amalgams and the corrosion current of the Ti-amalgam couples in the measurements were performed in 3 different electrolytic solutions: Ringer solution, fluorinated neutral Ringer solution and acid fluorinated solution. The three corrosive media are described. RESULTS: The results showed that Ti could be damaged by the presence of fluorides with an acid pH: Ti potential becomes more negative in acid fluorinated solution. The corrosion currents between Ti and amalgam couples were considered: the amalgams underwent anodic oxidation in neutral Ringer, but a reversal phenomenon occurred in the fluorinated acid solution: Ti was damaged and the amalgams both Prs and IQC.P became the cathodic partner of the couple. In neutral fluorinated solution the IQC.P amalgam induced a significantly higher corrosion of Ti, when compared to the Prs one. CONCLUSION: Results clearly show the dependence of the Ti corrosion behaviour on the pH and composition of the solution and that the outcome of the damage is affected by the composition of other metals.

Chemical Phenomena↗
PubMed1986

Solid solubility of tin in silver-mercury gamma 1 in dental amalgams.

The solid solubility of Sn in gamma 1 has been studied by examining a series of gamma 1 samples containing 0.25-2.0 wt% Sn by scanning electron microscopy and energy-dispersive X-ray analysis. It has been observed that the addition of Sn to gamma 1 leads to the formation of mainly an intergranular Sn-Hg compound. On the basis of this observation it has been concluded that the solubility of Sn in gamma 1 is virtually nil.

Chemical Phenomena↗
PubMed1984

The effect of zinc on the biocompatibility of dental amalgams in vitro.

When freshly triturated, two zinc-containing amalgams, Velvalloy and Dispersalloy, were more cytotoxic in vitro than two zinc-free amalgams Amalcap and Sybraloy. The high copper amalgam, Sybraloy, was only slightly irritant: similarly the presence of copper in Dispersalloy did not increase its toxicity over Velvalloy. All four amalgams retained some degree of toxicity up to one month after setting which is in marked contrast to most other dental materials investigated previously. This was greatest with the zinc-containing amalgams and was accompanied by the continued release of zinc over this period.

Animals↗
PubMed1987

Further investigations of the soft tissue reaction to the gamma 1 phase (Ag2Hg3) of dental amalgam, including measurements of mercury release and redistribution.

The subcutaneous implantation in guinea pigs of powdered gamma 1 phase induced a severe initial tissue response and the majority of the material was extruded from the healing wounds. This process was accompanied by the release of significant amounts of mercury which appeared in the body organs and excreta. The small numbers of particles which remained in the tissues were handled quite differently, undergoing slow degradation in macrophages and giant cells in chronic granulomata. Minute secondary particles containing silver and sulphur were deposited in the tissues and gave rise to macroscopic tattooing of the skin above the implants.

Animals↗
PubMed1995

Early compressive strength and phase-formation of dental amalgam.

The compressive strength of five different amalgams was measured at one hour, six hours, 24 hours, and seven days, and X-ray diffraction analysis was carried out for each amalgam at the same times in order to investigate the early strength characteristics of the amalgams in relation to the formation of different phases. At 24 hours all tested amalgams reached about 90% or more of their seven-day compressive strength, but the increase in the early compressive strength from one hour to 24 hours varied between different amalgams. Two of the five amalgams tested reached about 90% of their seven-day compressive strength at six hours. A significant correlation was found between the ratio of early compressive strength to seven-day compressive strength, and the X-ray diffraction intensity ratio (ratios of one-, six- and 24 hour intensity to seven-day intensity) for the gamma 1 phase, indicating that the increases in early compressive strength are mainly dependent upon the formation of gamma 1.

Analysis of Variance↗
PubMed1987

Further investigations of the soft tissue reaction to the gamma 2 phase (Sn7-8Hg) of dental amalgam, including measurements of mercury release and redistribution.

Following the subcutaneous implantation in guinea pigs of powdered gamma 2 phase with a mercury content only slightly greater than that indicated by the stoichiometric formula Sn7Hg, there was a limited initial release of mercury from extracellular material. Thereafter, chronic granulomata developed around the implants and particles degraded slowly in macrophages and giant cells. Vast numbers of fine secondary particles containing tin were produced and these were associated with macroscopic staining. Mercury seemed to be lost as the result of intracellular particle breakdown but it did not accumulate in the body organs or appear to any great extent in the excreta.

Animals↗
PubMed1994

Mercury deposits in neurons of the trigeminal ganglia after insertion of dental amalgam in rats.

An amalgam filling was inserted into the first upper molar of 12 rats and the animals were killed after 3-9 months. Tissue sections from the trigeminal ganglia and the brain stem were then investigated with a sensitive histochemical technique to trace mercury deposits. Within the trigeminal ganglia, nerve cells with mercury deposits were observed in seven out of 12 rats, whereas no mercury was detected in sections from the brain stem. The mechanism responsible for the accumulation of mercury in neurons of the trigeminal ganglia is discussed.

Animals↗
PubMed1983

Tissue reactions to the separate implantation of individual constituent phases of dental amalgam, including assessment by energy dispersive X-ray microanalysis.

Soft tissue degradation of the 3 principal amalgam phases have been investigated in relation to their role in the formation of the amalgam tattoo. Each phase, finely powdered, was implanted subcutaneously into the submandibular region of guinea-pigs for periods ranging from 1 week to 1 year. The rates of breakdown were assessed radiographically and the final lesions were examined by light and electron microscopy and X-ray microanalysis. gamma 2 (Sn7Hg) phase degraded rapidly, mainly extracellularly, and did not produce a tattoo. Both mercury and tin disappeared from the lesion. gamma 1 (Ag2Hg3) phase degraded less rapidly, both extra and intracellularly, and produced a small tattoo. Mercury was lost from the lesion. gamma (Ag3Sn) phase degraded slowly, intracellularly, and produced a large tattoo. Tattoos always resulted from persistence of minute particles of silver and sulphur associated with basal lamina and connective tissue.

Animals↗
PubMed1985

Influence of variations in preparation of dental amalgam on dimensional stability and porosities.

The susceptibility of amalgam to deviations in the preparation procedure produced an overall trend for both the setting dimensional stability and the number of porosities. The dimensional stability of ANA 2000 was the least affected by the deviations, while ANA 68 exhibited low susceptibility to the deviations when porosities are concerned. Lowered condensation pressure usually increased both the setting expansion and the number of porosities, and vice versa. Dispersalloy exhibited an increased number of porosities with both higher and lower condensation pressure. Except for ANA 2000, undertrituration caused increased expansion and porosities, while overtrituration resulted in increased contraction but minor effects on porosities. Lower mercury/alloy ratio increased the setting expansion and the number of porosities, while the response to a higher ratio was relatively small with the exception of a markedly increased setting expansion for ANA 68.

Chemical Phenomena↗
PubMed1991

Microstructures of Pd-containing dispersants for admixed dental amalgams.

Blended Pd-containing dispersants were developed by the utilization of a Ag-Cu eutectic into which Pd was substituted for Ag or Cu in concentrations of up to 20 wt%. Compositions were melted either in argon-filled sealed vycor tubes or in a graphite-linked carbon crucible of an induction furnace with an argon blanket. Ingots of approximately 1.5 cm in diameter were sectioned to 0.2 cm in thickness and polished through standard metallographic polishing procedures. The possible compounds were identified by XRD. The microstructures of the alloys were examined by SEM/EDS. XRD analysis of the alloys revealed the preferential dissolution of Pd in Cu when the Pd concentration was less than or equal to 10 wt%. When the Pd concentration exceeded 20 wt%, Pd was found to be dissolved in both Ag and Pd. No Cu3Pd x-ray diffraction peaks were found for alloys with Pd concentration of up to 20 wt%. SEM/EDS analysis confirmed XRD results; lamellae of Ag and Cu-Pd were found in alloys with Pd concentration less than or equal to 10 wt%.

Copper↗