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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A sample of 165 extracted or exfoliated teeth containing amalgam restorations were categorized as to the degree of marginal integrity of the amalgam. Microstructures of the samples representing the highest (grade 11) and lowest (grades 1 and 2) degrees of marginal deterioration were studied by SEM/EDS. The clinical evaluation and microscopic evaluation indicated that samples showing poor marginal integrity contained large quantities of tin-rich and tin-chlorine-rich corrosion products with little or no gamma-2 phase remaining. Obvious signs of fracture and cracking at the cavosurface were always present. Products containing calcium were extensively associated with corrosion products containing tin, and these were found predominantly at the tooth-amalgam interface. No copper-rich amalgams were found in this grouping. Amalgams with good marginal integrity had no microscopic cracks or fractures and generally little evidence of corrosion was found. However, one of six samples had extensive corrosion products, indicating that corrosion product formation is not the only factor contributing to marginal deterioration. After 6 years of clinical use, the degree of marginal deterioration did not appear to depend unerringly on time of use. Further work is necessary to define the microstructural characteristics of samples showing intermediate amounts of marginal deterioration and to determine if copper-rich amalgams consistently have small to moderate amounts of marginal deterioration.
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PMID:Characteristics of amalgam restorations with variable clinical appearance. 385 63

A migration of plastic particles from haemodialysis circuit to blood has been recognized to be cause of storage inflammation. Its origin from segments of silicone tubing has been demonstrated by in vivo and in vitro experiments. A similar finding with a peculiar histology picture has been observed in patients who used only PVC and PU-PVC tubing. In this case too microprobe analysis revealed the presence of silicon (Si) in fibril inclusions of liver and spleen cells. TEM, SEM and EDS of cuprophane dialyzer perfusates filtered through Nuclepore revealed the presence of particles with an intense Si Ka. The release from the dialyzer of silicon containing contaminants seems to be an additional risk for uremic patients.
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PMID:Electron microscopy and microprobe analysis of dialysis contaminants. 387 Jun 25

A single particle and four blended Cu-rich amalgam systems were immersed in 37 degrees C solutions for 1-20 months in order to determine the characterization and sequence of corrosion product formation. X-ray diffraction and SEM/EDS were used to characterize the products. The same sequence of formation occurred in all systems in Ringer's and 0.1% Ringer's solutions. The times at which each product formed varied with the brand of the amalgam and the concentration of the solution. The initial products were ZnSn(OH)6 in Zn-containing systems and SnO2 in most other systems. Cu2O formed next, followed by CuCl2 X 3Cu(OH)2. Immersion in 1% Na2S yielded only HgS on all brands. A combination of 1% Na2S and Ringer's solution yielded CaSn(OH)6 after 2 months and Cu2O at later periods. Artificial saliva resulted in a retardation of corrosion product formation and only limited amounts of a Sn-rich product could be found after 20 months. Interactions of the various components appear to alter the nature and rate of corrosion product formation on these systems and additional systematic investigations are necessary to understand the influence of these interactions on corrosion.
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PMID:Corrosion product formation sequence on Cu-rich amalgams in various solutions. 665 29

The superior clinical performance of several dental amalgams which contain high Cu concentrations and little or no gamma 2 has stimulated the introduction of a number of new amalgam alloys. This investigation sought to study the nature of the phases present in eight commercial systems after trituration. Samples were powdered for X-ray diffraction phase analysis or were polished for SEM/EDS analysis. These methods were complementary since they permitted positive identification of the phases and their distribution and composition, respectively. The matrix phase of all systems was gamma 1 (Ag-Hg). Cu6Sn5 was found as the major Sn-rich amalgamation product. The Cu6Sn5 phase forms reaction zones around th Cu-rich particles with morphological variations from system to system. All amalgams contained the gamma (Ag3Sn) phase, but it was microstructurally distinct only in two particle systems. Small amounts of the gamma 2 (Sn-Hg) phase were found in three systems. These results suggest that there are important microstructural variations in the new Cu-rich systems which could eventually result in variations in clinical performance.
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PMID:X-ray diffraction and SEM/EDS analyses of phases in new dental amalgams. 693 93

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.
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PMID:Cu2O and CuCl2 . 3Cu(OH)2 corrosion products on copper rich dental amalgams. 705 64

Rats were given strontium chloride (SrCl2) intraperitoneally at a dose of 500 mg/kg. The upper incisors were removed after injection of strontium. These incisors were studied by scanning electron microscopy-energy dispersive spectroscopy analysis (SEM-EDS) and light microscopy to examine the calciotraumatic lines of strontium in the rat incisor labial dentin. At 24 hours after injection of strontium, the calciotraumatic response was observed in the predentin using hematoxylin and eosin (H-E) staining. At 5 days, three layers of calciotraumatic lines were present in the labial dentin using an H-E staining and backscattered electron imaging in the SEM. The external layer consisted of unmineralized dentin, the intermediate layer of relatively unmineralized dentin, ane the internal layer of unmineralized dentin. By SEM-EDS analysis, strontium was detected in these layers. The elemental dot map showed that the external and internal unmineralized layers had a low calcium content. The magnesium concentration was higher in the internal unmineralized layer than the external unmineralized layer.
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PMID:Scanning electron microscopy and energy dispersive spectroscopy analysis of calciotraumatic lines in rat labial dentin after acute exposure to strontium chloride. 750 92

Although the current trend in dentin bonding favors the development of a hybrid layer interdiffusion zone for micromechanical bonding, the exact nature of the dentin-composite bond is still unclear. The objective of this study was to characterize the fracture surfaces of specimens used to measure interfacial fracture toughness. Morphological (SEM) and chemical (EDS and XPS) surface analyses were used for characterization. Fracture toughness specimens generally failed along the dentin-bonded interface in agreement with observed clinical failure modes. Four sites of bond failure were identified within the dentin-composite interfaces when All-Bond 2, Scotchbond Multi-Purpose, and Scotchbond 2 were used as the dentinal adhesives. These were located within (1) the smear layer, (2) a resin-modified layer between the interdiffusion zone and the adhesive resin, (3) a well-infiltrated hybrid interdiffusion zone, and (4) a non-infiltrated unsupported collagen layer. The interfacial region had a complex architecture which varied with the nature of the dentin, the dentin surface treatment, and the dentin bonding system. The sites of bond failure appeared to correlate with the interfacial fracture toughness and the extent to which polymerized resin infiltrated and acted to support the organic dentinal structures.
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PMID:Fracture surface characterization of dentin-bonded interfacial fracture toughness specimens. 816 31

The adherence of porcelain to four representative high-palladium alloys of the first generation (Pd-Cu-Ga) and second generation (Pd-Ga) was measured by use of a gold-palladium alloy as a control. The area fraction of adherent porcelain after metal-ceramic specimens were debonded in biaxial flexure at constant strain was calculated from the characteristic Si x-ray intensity with a standardized scanning electron microscope/energy-dispersive spectroscopy technique (SEM/EDS). The gold-palladium alloy exhibited the highest percentage of cohesive fracture through the porcelain, the two first-generation alloys were intermediate, and the two second-generation alloys exhibited the lowest area fractions. This study demonstrated that conventional visual (naked eye) or microscopic examination of the fractured metal-ceramic specimens at moderate magnification and the use of standard quantitative metallographic techniques were inadequate to provide accurate measurements of the area fraction covered with porcelain.
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PMID:Porcelain adherence to high-palladium alloys. 825 38

Physical, chemical, and mineralogical investigations of mineral concretions found in the human pineal gland were performed by means of optical microscopy and modern techniques of analytical electron microscopy and x-ray powder diffraction (OM,SEM + EDS,TEM + EDS,XRD). The mineral concretions were found to be nano-crystalline carbonate-hydroxyapatite with a mean Ca/P molar ratio equal to 1.65, very close to the theoretical value of 1.67. TEM and XRD showed that this is the only inorganic phase present in the concretions without the presence of amorphous phosphate as precursor. SEM and EDS, performed on cross-sectioned samples, showed a concentric layered distribution of the inorganic phase permeated by organic matter, within the concretions, with a slight increasing of the Ca/P molar ratio in their internal part.
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PMID:Physical, chemical, and mineralogical characterization of carbonate-hydroxyapatite concretions of the human pineal gland. 838 51

Titanium alloy has been proposed as a suitable alternative to noble metal alloys in premanufactured metal cylinders for fabricating implant prosthesis frameworks. The interfaces produced by standard lost wax procedures that use titanium and conventional noble metal implant cylinders with both high-fusing (high-palladium) and low-fusing (high-gold) noble metal casting alloys were compared. Elemental analysis by scanning electron microscopy and energy-dispersive spectroscopy (SEM/EDS) of the two titanium cylinders revealed that one commercial product had a composition similar to that for commercially pure titanium and the other had a composition consistent with that for Ti-6Al-4V alloy. The SEM observations and complementary elemental line scans indicated that the interfaces between the titanium cylinders and the two noble metal casting alloys did not meet proposed criteria for acceptable metal-to-metal unions. The interfaces between the noble metal cylinders and noble metal casting alloys did exhibit acceptable unions. The SEM observations and elemental analyses were supported by push-shear test results that showed that the resistance to failure was appreciably greater for interface specimens produced with alloy cast to noble metal cylinders compared with titanium cylinders.
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PMID:Titanium alloy cylinders in implant framework fabrication: a study of the cylinder-alloy interface. 846 69


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