Electron microscopic demonstration of calcium in mitochondria of the frog skeletal muscle in situ.
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Animals↗
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Composition of the cement line and its possible mechanical role as a local interface in human compact bone.
Human compact bone may be viewed as a fiber reinforced composite material in which the secondary osteons act as the fiber reinforcements. The cement line, which is the interface between the 'fibers' (osteons) and extraosteonal bone matrix, may impart important mechanical properties to compact bone. The nature of these properties is not known partly because the composition of the cement line is unknown. This analysis examines the constituents of the osteon cement line using scanning electron microscopy and X-ray microprobe analysis to address its biomechanical functions as a local interface. The analysis suggests that the cement line is a region of reduced mineralization which may contain sulfated mucosubstances. This composition is consistent with the hypothesis that the cement line provides a relatively ductile interface with surrounding bone matrix, and that it provides the point specific stiffness differences, poor 'fiber'-matrix bonding and energy transfer qualities required to promote crack initiation but slow crack growth in compact bone.
Adult↗
SEM and elemental analysis of composite resins.
Twenty-four chemically cured, 21 light-cured anterior, three light-cured anterior/posterior, and 18 light-cured posterior composite resins were examined using scanning electron microscopy, and the elemental composition of their filler particles was analyzed with an energy dispersive electron probe microanalyzer. According to the results obtained, the composite resins were divided into five groups (traditional, microfilled type, submicrofilled type, hybrid type, and semihybrid), with two additional hypothetical categories (microfilled and hybrid). Characteristics of each type were described with clinical indications for selective guidance of respective composite resins for clinical use.
Aluminum↗
Silver accumulations in periapical granulomas: report of five cases using the scanning electron microscope, the electron microprobe, and other complementary methods.
A series of cytologic imprints obtained from periapical granulomas were studied with the conventional light microscope, the scanning electron microscope, and the electron microprobe to analyze the chemical composition of several black deposits that were randomly observed near or in the cytoplasm of macrophages and multinucleated giant cells. These granulomas had been removed from endodontically treated human teeth in which the root canals had been obturated with silver cones and Grossman's sealer 3 to 5 years previously. To investigate whether corrosion had occurred on the silver cones, the cones were also examined with the scanning electron microscope and the electron microprobe. Our observations revealed that all the examined silver cones showed different degrees of corrosion on their surfaces, whereas different concentrations of silver, sulfur, and chlorine were detected at the same sites in the cytologic imprints. However, it is impossible to determine from this study whether the presence of corrosive by-products in the periapical tissues is responsible for the development of a pathologic reaction at these sites.
Adolescent↗
Anodic polarization behavior and microstructure of a gallium-based alloy.
A gallium-based alloy (GA) that was developed as a substitute for dental amalgam was investigated for anodic polarization behavior in deoxygenated Ringers solution, 37 degrees C. The related microstructures were examined and microanalyses were conducted. Four polarization tests were conducted by scanning from -300mV to +1,000 mV (vs. SCE) at 2 mV/s. Polarization of the first sample (GA-1) was stopped after the first anodic dissolution peak (-100 mV, 1.5-2.0 x 10(-3) A/cm2). The fourth sample (GA-4) was interrupted at the secondary peak (+1000 mV, 0.3 A/cm2). It was found that (1) the early stage of the first peak is related to selective dissolution of divalent tin ions, followed by a dissolution of Ga. Transmission electron diffraction (TED) identified the brown corrosion product as Ga2O3; (2) the GA-4 sample was covered with the white corrosion product of mainly Sn+4, identified as SnO2. In addition, the current density of the GA sample when coupled with a high-copper dental amalgam was 0.03 A/cm2 (with +1,000 mV) at the second peak which was about a ten times lower value than for the uncoupled sample; (3) the uncoupled gallium alloy and gallium alloy coupled with a high-copper dental amalgam showed 10(3)-10(4) times higher anodic current density than that of an uncoupled high-copper dental amalgam, suggesting that the gallium alloy is more corrosion prone.
Corrosion↗
Studies of the ocular compatibility of hydrogels. White spot deposits--chemical composition and geological arrangement of components.
Light, SEM and histochemical techniques were used to determine the architecture and composition of elevated deposits on a variety of commercial lenses of differing bulk and surface chemistries and wear protocols. Spoilt lenses were derived from controlled lens wear trials and additional clinical sources. Elevated deposits display a complex multilayered structure, unaffected by variations in wear protocol or bulk and surface chemistries. These deposits are predominantly composed of tear-derived lipids laid down in a well-defined fashion. The primary layer is composed of unsaturated lipids, whilst the secondary and tertiary layers are dominated by cholesterol and cholesterol esters. The composition and location of deposit components is unaffected by variations in, wear protocol, chemistry of the lens matrix, or tear composition of lens wearers. These findings suggest that unsaturated lipids are responsible for the biological interfacial conversion of hydrogel lenses, reducing their compatibility with the ocular environment.
Biocompatible Materials↗
Oxidation of four palladium-rich ceramic fusing alloys.
Oxidation of four ceramic fusing alloys with varying amounts of palladium (35-79 wt%) and with different oxidizing elements (In, Sn, Ga, Cu, Co) was studied by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The alloy containing cobalt and gallium oxidized mainly externally forming a rather continuous Co-rich oxide layer on the surface and a Ga-rich layer underneath it. The other alloys were oxidized internally. The oxidation behaviour of Pd was found to be strongly dependent on the other oxidizing constituents.
Alloys↗
Four calcium phosphate ceramics as bone substitutes for non-weight-bearing.
Calcium phosphate ceramics, beta-calcium pyrophosphate (Ca2P2O7), beta-tricalcium phosphate (Ca3(PO4)2), hydroxyapatite (Ca10(PO4)6(OH)2) and tetracalcium phosphate (Ca4(PO4)2O), were prepared. The calcium:phosphorus ratios and microporosities were 1 (31.6%), 1.5 (1.6%), 1.66 (1%) and 2 (34.6%) respectively. Samples (15 mm x 10 mm x 2 mm), abraded with No. 2000 alumina powder, were implanted into the tibial metaphysis of mature male rabbits. Failure load, when an implant detached from the bone or the bone itself broke, was measured. At 10 wk after implantation, the failure loads in beta-calcium pyrophosphate, beta-tricalcium phosphate, hydroxyapatite and tetracalcium phosphate were 31.65 +/- 9.90 N, 72.81 +/- 19.01 N, 49.49 +/- 17.25 N and 43.22 +/- 14.99 N respectively. At 25 wk after implantation, the values were 47.04 +/- 14.90 N, 71.34 +/- 19.50 N, 69.09 +/- 16.17 N and 62.03 +/- 18.62 N respectively. Histologically, bone bonding behaviour of calcium phosphate ceramics did not vary with the calcium:phosphorus ratio, as observed by contact microradiogram, Giemsa surface staining and scanning electron micrograph-electron probe micro analysis. There was no intervening soft tissue at the interface of bone and ceramics. Hydroxyapatite or tricalcium phosphate are used as bone substitutes. However, their mechanical strength is insufficient for weight-bearing and they are used as bone filler. This study showed that the apparent insignificance of strict calcium:phosphorus ratio with respect to the biological results greatly simplifies processing of calcium phosphate ceramics for clinical application. In clinical application, calcium phosphate ceramics with different Ca:P can be used as bone fillers for bone defects or bone cavities under non-weight-bearing conditions.
Animals↗
Amalgams made from liquid Hg-In.
The addition of indium to amalgam appears to reduce the mercury vapour above fillings during setting. In the present work the structure and the physical properties of amalgams with In additions to the mercury up to 30 vol.% have been investigated. No new phase or undissolved in could be detected by X-ray diffraction and scanning electron microscopy studies. Energy dispersive spectroscopy measured 4 at.% In in the gamma 1-phase of an amalgam with 20 vol.% In added to the mercury. At the same time, the Ag/Hg ratio was substantially increased compared with amalgam having no In addition. The compression strength decreased with increasing In content, and for amalgam with as much as 30 vol.% In added to the mercury, it fell below the minimum requirement of ISO 1559 (Alloys for dental amalgam, International Organization for Standardization, Geneva, 1986). An abrupt drop of the load at the onset of failure and cracks running through the gamma 1-phase, as well as the eta-phase, indicates embrittlement of these phases with increasing In content.
Alloys↗
New polyurethane compositions able to bond high amounts of both albumin and heparin. Part I.
In order to prepare polymers provided with better haemocompatibility with respect both to the coagulative cascade and to platelet aggregation and activation, we have synthesized new polyurethanes containing in the chain-extender [di(2-hydroxyethyl)hexadecylamine] both a long chain alkyl group (able to bond albumin) and a tertiary ammonium group able, after suitable quaternization reaction, to bind ionically significant amounts of heparin. The amounts of heparin and albumin bonded to the polymer films were determined spectrophotometrically. A biological in vitro evaluation of the heparinized and albuminized films was also carried out with respect to blood coagulation factors (by activated partial thromboplastin time measurements) and to platelet adhesion and activation (by platelet count and scanning electron microscopy examination). It was seen that the type of adsorption sequence for albumin and heparin, respectively, onto the various homo- and copolymer films, plays an important role on their biological properties; the possible mechanisms involved are also discussed on the basis of X-ray photoelectron spectroscopy and attenuated transmission reflectance evaluation of the polymer surfaces.
Albumins↗
Microwave fixation and localization of calcium in synaptic vesicles.
The distribution of Ca2+ ions is demonstrated in the synaptic terminals by means of a 2-step chemical precipitation of Ca2+ ions in nervous tissue. K-oxalate/K-antimonate chemical replacement with simultaneous computerized microwave irradiation is used. This precipitate in cell structures was investigated by computerized electron probe X-ray micro-analysis. The calculated values (from the theoretical, standards and sections), elemental binding ratios and elemental molecular weight ratios were compared. Each calculated value coincided with the theoretical value. This method can reliably detect Ca2+ ions at the micromolar level. Ca2+ ions were distributed in the synaptic vesicles and surrounding membranes. Further progress is expected in freeze-substitution and in the application and propagation of the EELS-Imaging system in calcium determinations.
Animals↗
Physical metallurgy of dental amalgams. 2. Microstructure.
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Chemical Phenomena↗
Effects of sandblasting and silica-coating procedures on pure titanium.
Silica coating titanium improves chemomechanical bonding. Sandblasting is recommended as a pretreatment to thermal silica coating (Silicoater MD) or as part of a tribochemical silica coating process (Rocatec). This study evaluated the effects of sandblasting and coating techniques on volume loss, surface morphology and composition changes in pure titanium. Volume loss of titanium was similar to values reported for base alloys and does not seem to be critical for the clinical fit of restorations. Embedded alumina particles were found in the titanium after sandblasting and the alumina content increased to a range of 27.5-39.3 wt% as measured by EDS. Following tribochemical silica coating, a layer of small silica particles remained on the surface, increasing the silica content to a range of 17.9-19.5 wt%. Ultrasonic cleaning removed loose alumina or silica particles from the surface, resulting in only slight decreases in alumina or silica contents, suggesting firm attachment of most of the alumina and silica to the titanium surface. Silica content following thermal silica coating treatment increased only slightly from the sandblasted specimen to 1.4 wt%. The silica layer employed by these silica coating methods differs widely in both morphology and thickness. These results provide a basis for explanation of adhesive failure modes in bond strength tests and for developing methods to optimize resin bonding. Clinically, ultrasonic cleaning of sandblasted and tribochemically silica coated titanium should improve resin bonding as loose surface particles are removed without relevant changes in composition.
Aluminum Oxide↗
Effects of hexafluorosilicate on the precipitate composition and dentine tubule occlusion by calcium phosphate.
OBJECTIVES: To improve the calcium phosphate precipitation (CPP) method for the occlusion of dentine tubules with calcium phosphate, the addition of calcium hexafluorosilicate (CaSiF6) to CPP solution was evaluated in vitro with respect to its occluding capacity and the composition of the precipitate. METHODS: The occlusion of dentine tubules was evaluated by SEM observations and by measurements of dentine permeability. The composition of the precipitate was determined by measuring the calcium to phosphorus (Ca/P) ratio of the precipitate in dentine tubules by energy dispersive X-ray spectroscopy (EDS). RESULTS: The addition of CaSiF6 to the CPP solution resulted in an increase of the Ca/P ratio in the precipitate not only on the dentine surface but also inside the dentine tubules; indicating that the precipitate became more apatitic in nature. The addition of CaSiF6 had no effect on occluding capacity in terms of measurements of dentine permeability or SEM observations. Dentine permeability decreased to approximately 4% of pretreatment values and the dentine tubules were occluded for approximately 10-15 microns from the dentine surface. CONCLUSION: It is concluded that the addition of CaSiF6 to CPP solution was desirable, since it provided a more apatitic precipitate in the dentine tubules, not only on the dentine surface but also inside the tubules, and there were no drawbacks with respect to its occluding capacity.
Apatites↗
The influence of objective lens aberrations in energy-loss spectrometry.
The conditions under which the energy resolution and collection efficiency in electron energy-loss spectrometry are limited by the spherical and chromatic aberrations of the objective lens have been studied. It is shown that, for the optimum settings of the pre-spectrometer optics, the energy resolution will be of the same order in diffraction mode as it is in magnification mode. The influence of the aberrations on the practice of energy-loss spectroscopy is discussed, and it is demonstrated that the chromatic aberration can act as a broadband filter for energy-loss electrons.
Electron Probe Microanalysis↗
Structure and location of tellurium deposited in Escherichia coli cells harbouring tellurite resistance plasmids.
The plasmids RP4Ter and pHH1508a, which belong to the P and HII incompatibility groups, respectively, confer resistance to potassium tellurite (K2TeO3) on Escherichia coli. The genes for tellurite resistance were cloned from each plasmid onto the vector pUC8 to create pDT1366 and pD1364, respectively. Unstained, unfixed bacteria carrying these plasmids contained black intracellular deposits when grown on media containing tellurite. Thin sections of these bacteria fixed with glutaraldehyde were prepared and examined by electron microscopy. The black deposits were located inside the cell and were frequently associated with the inner membrane of the bacterium. Bacteria containing pDT1366 or pDT1364, and therefore a higher gene dosage of the Ter determinant, contained more black deposits, but had a decreased resistance, as measured by the minimum inhibitory concentration using the agar dilution method. Using the technique of electron spectroscopic imaging, the black intracellular deposits were shown to contain predominantly reduced metallic tellurium, and significant amounts of oxygen or carbon, thereby confirming earlier results using X-ray diffraction analysis of whole cells.
Cell Membrane↗
In vivo evaluation of resorbable bone graft substitutes in a rabbit tibial defect model.
Calcium sulfate as a bone graft substitute is rapidly resorbed in vivo releasing calcium ions but fails to provide long-term three-dimensional framework to support osteoconduction. The setting properties of calcium sulfate however allow it to be applied in a slurry form making it easier to handle and apply in different situations. This study examines the in vivo response of calcium sulfate alone and as a carrier for a coralline hydroxyapatite in an established bilateral corticocancellous defect model in rabbits. Defects were filled flush to the anterior cortex with a resorbable porous ceramic alone and in combination with calcium sulfate slurry, calcium sulfate slurry alone or calcium sulfate pellets and examined at time points up to 52 weeks. Specimens where assessed using Faxitron X-ray, light and electron microscopy. Calcium sulfate in either slurry or pellet form does indeed support new bone formation alone however, complete filling of the bone defect is not observed. Calcium sulfate in slurry form does however improve the surgical handling of particulate bone graft substitutes such as Pro Osteon 200 R, which remained as an osteoconductive scaffold for up to 52 weeks and may have played an important role in the ultimate closure of the cortical windows.
Absorbable Implants↗
A microprobe analysis of inorganic elements in Halobacterium salinarum.
Halobacterium salinarum were grown on peptone agar containing 4.28 M NaCl, 0.036 M K and other salts. Stationary phase organisms were lifted onto carbon planchets, freeze-dried, carbon coated and examined in a scanning electron microscope equipped with an X-ray spectrometer. Intracellular element concentrations (mol/kg H(2)O) were determined using a bulk analysis program with appropriate standards. The cell K concentration was 110 times that of the medium. For Na this value was 0.3 and for Cl, 1.1. When Rb was present in the medium, its intracellular concentration was 77 times higher than the external value. The cation minus anion value suggests a high fixed negative charge, 0.72 equivalents. Intracellular apparent dielectric constants were calculated using cellular EMFs derived from the literature, and sodium concentration. The determined values ranged from 22-28 (vs 80 for normal water) suggesting phases of structured cell water. Ionic distributions in these extremophiles are treated according to the classical principles elucidated by Willard Gibbs and represents a heterogeneous system in thermodynamic equilibrium with the hypersaline environment. Factors to be considered are: (1) composition of Halobacterium and its immobile negative charge; (2) the physicochemical properties of the individual ions (charge, ionic radius, hydration energy, standard chemical potential); (3) the dielectric constant of the dispersion medium (water); and (4) the binding of ions, particularly potassium.
Chlorides↗