Types Of Amalgam Research Articles

Spectroscopic properties of merocyanine mixed J-aggregate in wide temperature range

The monolayer assemblies incorporating merocyanine J-aggregates, MC(S), MC(Se), 6-Me-MC(S), and their combinations have been fabricated by the Langmuir–Blodgett (LB) technique. At room temperature, absorption and fluorescence spectra of the monolayer assemblies: MC(S), MC(Se), 6-Me-MC(S), are characterized by a sharp J-band and resonance fluorescence. The monolayer assemblies incorporating two dyes: MC(S)/MC(Se), 6-Me-MC(S)/MC(S), 6-Me-MC(S)/MC(Se), bear a single absorption band and accompanying fluorescence band, which are assigned to the homogeneous aggregate of amalgamation type (HA-aggregate). Detailed spectroscopic measurements: absorption spectra in wide temperature range and the fluorescence decay curves, of the MC(S)/MC(Se) assembly have been carried out as a prototype of the HA-aggregate. The continuous shift of the absorption and fluorescence peak positions with increasing x, from x = 0 (MC(S) assembly) to x = 1 (MC(Se) assembly), would indicate that the doping of MC(Se) molecules into the MC(S) J-aggregate does not induce serious structure change. An observation that the fluorescence lifetime of the MC(S)/MC(Se) assembly lies between those of the MC(S) assembly and the MC(Se) assembly implies that the inclusion of MC(Se) molecules does not result in the formation of defect states which may promote non-radiative decay of molecular excitons. The usefulness of the Urbach–Martienssen (UM) rule for the analysis of the low energy tail of absorption spectra of the MC(S)/MC(Se) assembly has been examined.

Surface Change of Dental Amalgam after Treatment with 10% Carbamide Peroxide

The aim of this study was to explore the effect of bleaching agents on the release of metal ions and change in physical and chemical characteristics of amalgams. Amalgam surface changes resulting from bleaching on amalgam were assessed with inductively coupled plasma atomic emission spectrophotometer, an automatic mercury analyzer, a colorimeter, and atomic force microscopy. Analysis of the release of metal ions indicated that the bleaching agent caused more copper, tin, and mercury ions to be released into the immersion solution. Furthermore, metal ion release increased progressively as immersion time was increased from 42 to 84 hours. Morphological examination revealed no significant effects of the 10% carbamide peroxide bleaching agent on the surface morphology of any of the amalgams tested. These results demonstrated that bleaching using 10% carbamide peroxide did not adversely affect the two types of amalgam tested. In other words, a 10% carbamide peroxide bleaching agent can be safely used on a short-term basis in dentist-monitored bleaching of the dental amalgam.

Flag-transitive c-extensions of the F4(2)-building—the amalgams

We characterize the possible isomorphism types of amalgams of maximal parabolics associated with a flag-transitive action on a c-extended F4(2)-building.

Long-term monitoring of microleakage of different amalgams with different liners

Microleakage is a major factor contributing to the occurrence of secondary caries around amalgam restorations. Purpose The purpose of this study was to evaluate the effect of amalgam type, liner type, and storage period on microleakage. Two hundred seventy bovine incisors were divided into 18 groups (n = 15). Two high-copper amalgam alloys (admixed and spherical type) and 3 liner options (no liner, varnish, and adhesive) were used to restore Class V preparations. After placement of restorations, the teeth were stored for 3 different periods (1 day, 1 week, and 12 months) in saline solution, After storage, the specimens were immersed in 0.5% methylene blue for 24 hours, sectioned, and then mean depth of dye penetration was measured separately for the incisal and cervical areas with the use of a binocular microscope (x200). Scores were assigned to a millimeter scale (+/- 0.2 mm). The data were analyzed with a 3-way analysis of variance and the Tukey Honestly Significant Different test (alpha = .05). The 3-way interaction was significant (P < .001 for the cervical and occlusal margins). After short-term storage (1 day and 1 week), the admixed alloy showed significantly lower leakage values than the spherical alloy only in cervical margins (1.45 and 1.56 for the admixed and 1.62 and 1.50 for the spherical alloy at the cervical [P = .034] and incisal margins [P = .702]), respectively. After 12 months, values decreased significantly for both amalgams, which were similar and lower than for the short-term storage period (short-term values of 1.62 and 1.39 for the admixed and 1.69 and 1.46 for the spherical alloy at the cervical and incisal margins, respectively; long-term values of 0.22 and 0.20 for the admixed and 0.33 and 0.36 for the spherical alloy at the cervical and incisal margins, respectively [P < .019]). When the adhesive was used, significantly superior sealing was observed for both amalgams. For the no liner and cavity varnish groups, the admixed alloy showed superior performance compared to the spherical alloy (with no liner, 1.11 and 0.98 for the admixed and 0.83 and 1.08 for the spherical alloy at the cervical and incisal margins, respectively; with varnish, 1.19 and 1.22 for the admixed and 1.63 and 1.34 for the spherical alloy, at the cervical and incisal margins, respectively [P < .037]). In the short-term, the lowest degree of leakage was found when adhesive was used. After 1 year, no differences were detected, regardless of the amalgam type and liner used.

Spectroscopic properties of merocyanine J‐aggregate in LB films

AbstractLangmuir–Blodgett (LB) films incorporating unsymmetrical merocyanine dyes; MC(X) (X = O, S, Se), have been fabricated. The J‐aggregates of MC(S) and MC(Se) are characterized by a sharp J‐band and resonance fluorescence. The MC(O) aggregate has a broad absorption band and is non‐fluorescent. We have examined the formation of mixed J‐aggregates in the MC(X)/MC(Y) assemblies (X, Y = O, S, Se). It has been found that a homogeneous aggregate of amalgamation type (HA‐aggregate) is formed in the MC(S)/ MC(Se) assembly. The mixed J‐aggregate in the MC(O)/MC(S) and the MC(O)/MC(Se) assemblies are classified into a mosaic (M‐)aggregate in a wide sense. Despite of similar molecular structure of MC(O) with both MC(S) and MC(Se), the growth of the MC(O) aggregate with a help of the J‐aggregate of MC(S) or MC(Se) as a template may hinder the homogeneous mixing of dye molecules. (© 2005 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Amalgam type, adhesive system, and storage period as influencing factors on microleakage of amalgam restorations

Statement of problem The penetration of oral fluids and bacteria at the interface between the preparation walls and amalgam restorations, known as marginal microleakage, continues to be a problem in restorative dentistry. Microleakage may result in secondary caries and the irritation of the pulp. Purpose This study evaluated the effect of amalgam type, adhesive system, and storage period on microleakage of amalgam restorations Material and methods Eighty human premolars and molars were divided randomly into 8 equal groups of 10 teeth each. A combination of 2 different types of amalgam alloys (Spherodon and Nogama-2) and 2 bonding agents (Resinomer and High-Q-Bond) were used to restore Class V preparations. After thermocycling for 750 cycles (4°C and 60°C for 1-minute dwell times), the teeth were stored in a corrosive solution (modified Fusayama solution). The mean depth of fuchsin dye penetration was evaluated after an immersion period of 14 days and 180 days. The data were analyzed with a 3-way analysis of variance model and Wilcoxon paired signed rank test (α=.05). Main effects (aging time, amalgam, and adhesive), as well as possible interactions, were included in the model. Results Significant differences were found in all analyzed combinations. The 3-way interaction between time, restoration, and adhesive was significant ( P=.04 and P=.015 for the cervical and occlusal margin, respectively). After long-term storage, dye penetration values decreased in all groups and reached a lower level compared with short-term storage (range of 0.42 mm to 0.83 mm versus 0.61 mm to 3.6 mm for the long and short term, respectively). Conclusion An adhesive bonding agent may affect microleakage in the short term. However, in the long term the effect of the adhesive does not appear to be the dominant factor in reducing microleakage around amalgam restorations.

Surface analysis of dental amalgams by X-ray photoelectron spectroscopy and X-ray diffraction

Objectives. It is important to characterize the surface of dental amalgam in order to understand the process of mercury release from amalgam restorations in the oral cavity. The mercury evaporation occurs not only from the newly made restoration but also from the set material. Methods. The surfaces of four different types of amalgams, which had been well set, were analyzed with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) and the relationship between surface compositions and mercury release was studied. Fresh amalgam surfaces as well as aged surfaces, which were stored for 30 days in air, were investigated using XPS and the chemical states of amalgam components and oxygen were studied. The aged surfaces were also characterized with XRD and grazing angle XRD. Results. With increased oxidation, the surface contents of tin and oxygen were increased in all amalgams. In contrast, the surface contents of copper and mercury were decreased. An increase of zinc or indium content were observed in zinc or indium containing amalgams, respectively. A surface layer enriched with indium and oxygen was clearly detected by XPS but not with grazing angle XRD. Significance. The thickness of the enriched surface layer is estimated to be in the order of few nanometer, which is approximately equal to the analysis depth of XPS. In addition, the presence of metallic elements, like tin and zinc, that readily form a stable oxide layer at the surface suppress the release of mercury.

Structural and optical characterization of polycrystalline CdSe x Te 1-x thin films

Solid solutions of CdSexTe1-x (0.7≤x≤1) were synthesized by vacuum fusion of stoichiometric amounts of CdSe and CdTe constituents in a silica tube. X-ray and electron microscope diffractometry techniques revealed that the CdSexTe1-x thin films were polycrystalline with a hexagonal structure. The variation of lattice constants with composition was found to obey Vegard’s law. The compositional dependence of the optical constants, the refractive index n and the absorption index k, of the films was determined in the spectral range of 400–2000 nm. The dispersion of the refractive index of the films could be described using the Wemple–DiDomenico single oscillator model. Changes of the dispersion parameters were also studied as a function of the mole fraction x. A plot representing α2=f(hν) showed that the CdSexTe1-x thin films of different compositions have two direct transitions corresponding to the energy gaps Eg and Eg+Δ. The variation in either Eg or Eg+Δ with x indicates that this system belongs to the amalgamation type. The variation follows a quadratic dependence and the bowing parameters were found to be 0.4 and 0.5 eV, respectively.

Mercury release from dental amalgams into continuously replenished liquids

Objective: Studies have been performed using high- and low-copper amalgams to measure the amounts of mercury dissolution from dental amalgam in liquids such as artificial saliva; however, in most cases, mercury dissolution has been measured under static conditions and as such, may be self-limiting. This study measured the mercury release from low- and high-copper amalgams into flowing aqueous solutions to determine whether the total amounts of dissolution vary under these conditions when tested at neutral and acidic pH. Methods: High- and low-copper amalgam specimens were prepared and kept for 3 days. They were then longitudinally suspended in dissolution cells with an outlet at the bottom. Deionized water or acidic solution (pH1) was pumped through the cell. Test solutions were collected at several time periods up to 6 days or 1 month and then analyzed with a cold vapor atomic absorption spectrophotometer. After dissolution testing, the specimens were examined using SEM/XEDA for any selective degradation of the phases in the amalgam. Results: Except for the high-copper amalgam in the pH1 solution, the dissolution rates were found to decrease exponentially with time. The rate for the high-copper amalgam in pH1 solution slowly increased for 1 month. The total amounts (μg/cm 2) of mercury released over 6 days or 1 month from both types of amalgam in deionized water were not significantly different ( p≥0.05). The high-copper amalgam released significantly more mercury than the low-copper amalgam in the pH1 solution at both time periods. For both amalgams, the dissolution in pH1 was significantly higher than in deionized water. Significance: Mercury dissolution from amalgam under dynamic conditions is enhanced in an acidic media, and most prominently for a high-copper formulation.

PENGARUH PENAMBAHAN PALADIUM TERHADAP PERILAKU THERMAL AMALGAM TEMBAGA TINGGI TIPE LATHE CUT

Effects of additing 1 percent (w/o) palladium (Pd) on the thermal behavior of a lathe cut type high copper amalgam (13 w/o copper) were studied. The identical alloys, with and without 1% Pd were fabricated. X-ray diffraction studies of the amalgams revealed the elimination of the γ 2 -phase by Pd addition DSC thermogram of non-Pd containing amalgam indicated the existence of two γ 1 -phaseone with the transition temperature (endothermic peak) at 88 ◦ C and the other at 109 ◦ C. The thermogram data of the Pd containing amalgam showed an endothermic peak at 110.7 ◦ C. The transition temperature of the n phase of the palladium containing amalgam is 4.9 ◦ C lower than the transition temperature of the n phase of the non Pd containing amalgam. This result indicates that the n phase of the Pd containing amalgam includes more of Tin (Sn) than the non-Pd containing amalgam. The thermogravimetri diagram showed that the phase decomposition occurred at about 390 ◦ C for the non-Pd containing amalgam and at about 410 ◦ C for the Pd containing amalgam. It is concluded that the addition of 1% Pd into a lathe cut type of high copper amalgam (13%) could eliminate the formation of γ 2 phase as well as an unstable γ 1 phase, promoting strong mercury bonding to Silver.

Electronic Structures of a Quantum Well of A1-xBx Alloy Semiconductor in the Coherent Potential Approximation

We have theoretically studied the electronic and optical properties of a quantum well (QW) in which the well region is constructed from a binary alloy semiconductor A1—xBx in the coherent potential approximation (CPA). A tight binding model is used for a single particle (electron, hole, Frenkel exciton) in the well composed by a rectangular array of Nx × Ny × Nz sites. The effect of the diagonal randomness is reduced to the coherent potential Σ(E), which is assumed to be the same for all sites, and is selfconsistently determined with the average Green's function. For a slab (∞, ∞, Nz) and wire (∞, Ny, Nz), the density of states ϱ(E) is composed of Nz (or Ny × Nz) subbands, each shows the two (one)-dimensional van-Hove singularity. When x (or 1 — x) is small, a B (A) impurity-band always appears at the lower (higher) energy side of the lowest (highest) host-band. As the well width becomes narrower and/or the dimensionality decreases, the boundary for Δ/t decreases which separates the amalgamation type and the persistence type.

Structural, Compositional, Optical, and Electrical Properties of Solution‐Grown ZnxCd1 − x S Films

Thin films of zinc cadmium sulfide have been prepared in the entire range from ZnS to CdS by using a chemical solution growth technique. Structural, compositional, optical, and electrical properties of thin films of have been studied as a function of x. X‐ray studies show that as‐grown films are composed of a hexagonal phase in the range 0 ≤x < 0.5 and a cubic sphalerite phase for x ≥ 0.5. Film optical parameters were evaluated and correlated with the composition ratio, x. These studies show that films of different compositions have two direct transitions with corresponding energy gaps Eg and . The variations in and with x indicate that is an amalgamation type following quadratic equations with bowing parameters 0.3 and 0.5, respectively. The resistivity of solution‐grown films was found to increase with increasing x. The effect of boron doping on electrical properties was also investigated. © 2000 The Electrochemical Society. All rights reserved.

Mercury evaporation from amalgams with varied mercury contents.

This study examined the relationship between mercury content and mercury evaporation from amalgams during setting. Two different types of commercial high-copper amalgams (single composition and admixed types) were used. Cylindrical specimens of each amalgam were prepared with five different mercury contents according to ADA Specification No.1. Specimens were also prepared by hand condensation. Mercury evaporation from amalgam specimens maintained at 37 degrees C was measured using a gold film mercury analyzer from 10 min after the end of trituration until the mercury concentration in air reached an undetectable level. The mercury content more clearly influenced the mercury evaporation from the admixed type amalgam specimens when the mercury content decreased below the manufacturers' recommended trituration conditions. Triturating with less mercury than the manufacturers' recommended amount cannot lower the evaporation of mercury from freshly made amalgam. Proper condensing procedures can minimize the mercury evaporation from the amalgam surface.

A Study of the Microstructural Characteristics of Dental Amalgams

Metallographic studies by scanning electron microscopy and energy dispersive spectroscopy carried out for two types of dental amalgam showing a porous multiphase material. Surface analysis shows that the structure of the Dispersalloy amalgam consists of γ-Ag 3 Sn, γ 1 -Ag 2 Hg 3 , η'-Cu 6 Sn 5 , e-Cu 3 Sn and eutectic Ag-Cu phases, while Velvalloy amalgam consists mainly of γ, γ 1 and γ 2 -Sn 7-8 Hg phases. The latter phase presents an uniform distribution often associated with voids.

Effects of palladium on the thermal behavior of the γ1-phase of the Ag-Sn-Cu dental amalgam

Abstract Effects of the addition of 1 weight percent (w/o) palladium on the thermal behavior of a lathe-cut type of high copper amalgam (13 w/o copper) were studied. Two identical alloys, with and without 1 w/o palladium were fabricated. X-ray diffraction studies of these amalgams have revealed the elimination of the γ 2 -phase by palladium addition. DSC thermograms of non-palladium-containing alloy indicated the existence of two γ 1 -phases, one with the transition temperature at 88 °C and the other at 109 °C. Aging for 18 months at 37 °C cannot eliminate the presence of the γ 1 -phase which has a low transition temperature. The addition of 1 w/o palladium into amalgam produced a more thermally stable amalgam.

Luminescence properties of the mixed J-aggregate consisting of two kinds of thiacarbocyanine dyes or naphthothiacarbocyanine dyes having meso-substituent

The J-aggregates of thiacarbocyanine dyes and naphthothiacarbocyanine dyes having bulky meso-substituent; 5,5′-dichloro-3,3′-diethyl-9-methyl-thiacarbocyanine chloride (dye I), 5,5′-dichloro-3,3′,9-triethyl-thiacarbocyanine chloride(dye II), 5,5′-dichloro-3,3′-diethyl-9-phenyl-thiacarbocyanine chloride(dye III), 3,3′-diethyl-9-methyl-4,5,4′,5′-naphthothiacarbocyanine bromide(dye IV), 3,3′,9-triethyl-4,5,4′,5′-naphthothiacarbocyanine chloride(dye V), 3,3′-dimethyl-9-phenyl-4,5,4′,5′-naphthothiacarbocyanine chloride(dye VI), in monolayer assemblies have been fabricated. From the viewpoints of steric requirement and electronic requirement proposed by us, it has been expected that mixed assemblies, donor/acceptor/arachidic acid(C 20), which incorporate two kinds of thiacarbocyanine dyes or naphthothiacarbocyanine dyes in the same layer plane, could form the homogeneous aggregate of amalgamation type (HA-aggregate), which is characterized by a single J-band and accompanying resonance fluorescence distinct from corresponding peaks of each dye. We have really observed the HA-aggregate in the combinations of dye II dye III , dye IV dye VI and dye V dye VI . On the other hand, in spite of similar molecular structure, the dye I/dye III/C 20 assembly does not form the HA-aggregate, but produces the separate aggregate or mosaic aggregate.

Microleakage of a 4-methacryloxyethyl trimellitate anhydride bonding agent with amalgams

Microleakage contributes to deterioration of materials, recurrent decay, growth of microorganisms at the interface, and postoperative tooth sensitivity. This study examined the microleakage between amalgams and tooth surfaces with a cavity liner, a 4-methacryloxyethyl trimellitate anhydride bonding agent (Amalgambond) and six different types of amalgams. Class 1 cavity preparations in extracted human molars were filled with different combinations of liners and amalgams and were stored at 37° C in physiologic saline solution. After 1 week half of each amalgam restoration was removed. Within the same group the same cavity treatment was performed and the same type of amalgam was packed as before. Microleakage was determined after 2000 thermal cycles. Statistical analysis indicated that Amalgambond significantly reduced microleakage of different amalgams compared with the Copalite-lined and unlined controls. No microleakage was detected at the interface between the existing and replacement amalgams.

Antibacterial effects of some root end filling materials

In addition to having good sealing ability, root end filling materials should "ideally" have some antibacterial activity to prevent bacterial growth. This investigation compared the antibacterial effects of amalgam, zinc oxide-eugenol, Super EBA and a mineral trioxide aggregate on nine facultative bacteria Streptococcus fecalis, Streptococcus mitis, Streptococcus mutans, Streptococcus salivarius, Lactobacillus species, Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, and Escherichia coli B and seven strict anaerobic bacteria, Prevotella (Bacteroides) buccae, Bacteroides fragilis, Prevotella (Bacteroides) intermedia, Prevotella (Bacteroides) melaninogenica, Fusobacterium necrophorum, Fusobacterium nucleatum, and Peptostreptococcus anaerobius. After growing these bacteria on solid media, freshly mixed and 24-h set test materials were placed on the surface of these inoculated media and incubated in the appropriate atmosphere for 24 to 48 h at 37 degrees C. Impregnated discs with the Super EBA liquid were used as positive controls. The antibacterial effects of each material were measured in millimeters and the data were analyzed using one-way and two-way analysis of variance and Scheffé tests to determine the statistical differences between the antibacterial effects of the test materials. Impregnated discs with Super EBA liquid caused varying degrees of growth inhibition for both facultative and strict anaerobic bacteria. Both types of amalgam had no antibacterial effect against any of the bacteria tested in this study. Mineral trioxide aggregate had an antibacterial effect on some of the facultative bacteria and no effect on any of the strict anaerobic bacteria. Zinc oxide-eugenol and Super EBA pastes had some antibacterial effects on both types of bacteria tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Mercury Release from Dental Amalgams: An in vitro Study Under Controlled Chewing and Brushing in an Artificial Mouth

The release of mercury vapor from class I amalgam restorations prepared in human molar teeth was studied during chewing simulations in an artificial mouth of a bi-axial servo-hydraulic mechanical test system. So that the total mercury released from the restoration over a fixed time could be determined, a closed chamber surrounded the envelope of chewing motion. In addition, the influence of sampling frequency on mercury release was corrected by the use of different sampling frequencies over a fixed time interval of mercury release measurement and extrapolation to zero sampling time. Thus, a combination of a closed environment and an extrapolation method to determine the mercury release under continuous sampling was used to determine the mercury released under normal breathing conditions. The measured mercury release rate data were used to calculate the potential daily mercury dose in a patient due to a single amalgam restoration, following the method previously outlined by Berglund. The mercury release from both a conventional and a high-copper amalgam was evaluated at different age intervals after the restoration was placed in the teeth. The results show that while the age of the amalgam and the amalgam type influence the extent of mercury release during the initial non-steady-state conditions, the steady-state value of mercury daily dose due to a single amalgam filling is 0.03 micrograms/day, which is well below the calculated threshold-limiting value (TLV) of 82.29 micrograms/day considered dangerous for occupational exposure in the United States.

A comparative electrochemical in vitro evaluation of the corrosion behaviour of dental amalgams

The electrochemical corrosion behaviour of 16 currently marketed amalgams for dental fillings was studied in vitro. Depending upon the type of amalgam and the treatment of the filling the electrochemical corrosion currents derived from cyclic voltammograms varied over several orders of magnitude. Their change as a function of time was also very different. Suggestions are made for a stability rating of the products based on the results obtained.