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PubMed2006

Microstructures of beta-titanium orthodontic wires joined by infrared brazing.

The microstructures and interdiffusion in brazed beta-titanium orthodontic wires were investigated by scanning electron microscopy and electron probe microanalysis, respectively. Beta-titanium wire (Ti-11Mo-6Zr-4Sn) with cross-section dimensions of 0.032 in. x 0.032 in., titanium-based braze alloy (Ti-30Ni-20Cu), and silver-based braze alloy (Ag-22Cu-17Zn-5Sn) were selected for the study. Brazing was performed using infrared radiation (RS-1) under an argon atmosphere. Specimens were etched with two solutions (2.5% HF + 2.5% HNO(3) + 95% H(2)O; 25% HN(4)OH + 30% H(2)O(2) + 45%H(2)O). It was found that the silver-based braze alloy has a eutectic structure. In the diffusion layer between the beta-titanium wire and this silver-based braze alloy, Cu and Ti were enriched on the wire side, and Sn and Ti were enriched on the braze alloy side. The titanium-based braze alloy has a dendritic structure. Beta-titanium wire specimens brazed with the titanium-based braze alloy had a thicker intermediate area compared to the silver alloy; Ti in the diffusion layer had an irregular concentration gradient, and the braze alloy side had higher Ti concentration. The original microstructure of the beta-titanium wire was not altered with the use of either braze alloy. Infrared brazing of beta-titanium orthodontic wire is acceptable for clinical use, since the wire microstructure did not deteriorate with either the titanium-based or silver-based braze alloy. The differing microstructures of the joint regions for the two braze alloys suggest that the joint strengths may also differ.

Dental Soldering↗
PubMed1997

Bonding of chemically treated titanium implants to bone.

A study was undertaken in rabbit tibiae to determine the effects of chemical treatments and/or surface-induced bonelike apatite on the bone-bonding ability of titanium (Ti) implants. Smooth-surfaced plates (10 x 10 x 2 mm) of pure Ti, alkalil- and heat-treated Ti, and bonelike apatite-formed Ti after the treatments were implanted into the tibial metaphyses of mature rabbits. The tibiae containing the implants were harvested at 4, 8, and 16 weeks after implantation and subjected to a tensile testing and histologic evaluation. Biomechanical results showed that both treated implants exhibited significantly higher failure loads compared with untreated Ti implants at all time periods. Histologic examination by Giemsa surface staining, contact microradiography (CMR), and scanning electron microscopy (SEM) in backscatter mode revealed that both treated Ti implants directly bonded to bone tissue during the early postimplantation period, whereas untreated Ti implants formed direct contact with the bone only at 16 weeks. SEM-electron-probe microanalysis (EPMA) examination showed a Ca-P-rich layer at the interface between the treated implants and bone, although the Ca-P-rich layer was not detected on the surface of untreated implants during observation periods. The results of this study suggest that chemical treatments may accelerate the bone-bonding behavior of titanium implants and enhance the strength of bone-implant bonding by inducing a bioactive surface layer on Ti implants.

Animals↗
PubMed1977

[Chemical analysis of the integument and digestive gland of Crangon crangon (Linné) (Crustacea, Decapoda) by x ray spectography. Quantitative variations in the elements of calcium, phosphorus, sulfur, and magnesium during the intermolt cycle].

Electron probe microanalysis is a very suitable method for qualitative and quantitative analysis of calcium, phosphorus, sulfur and magnesium occurring within integument and digestive gland; variations related to intermolt cycle can be compared.

Animals↗
PubMed1997

Effect of resin-modified glass ionomer cements on secondary caries.

PURPOSE: To evaluate the in vitro secondary caries inhibitory effect of two resin-modified glass ionomer cements (R-GICs). MATERIALS AND METHODS: Class V cavities were prepared at the cementoenamel junction on facial and lingual surfaces of 32 extracted upper premolars. The facial cavities were restored with a conventional glass ionomer cement (GIC) (Fuji II), while the lingual cavities were restored with either one of the R-GICs (Fuji II LC, Photac Fil, Vitremer), or a resin composite (Z-100). The margins of the restorations were subjected to a 20-day in vitro cariogenic challenge and the degree of demineralization was analyzed by microradiography. The amounts of fluoride released into distilled water from disc specimens of the materials tested were also measured for immersion time up to 161 days. RESULTS: The R-GICs and GIC's released similar cumulative amounts of fluoride over 161 days. Photac-Fil showed significantly higher amounts of fluoride release over the same period. The depth of the outer lesion and the thickness of the acid-resistant layer showed no significant difference among the R-GICs and GIC's. Moreover, the residual fluoride and calcium in the dentin adjacent to the R-GICs and GIC's were correlated with the thickness of acid-resistant layers in the dentin adjacent to the R-GICs and GIC's by electron probe microanalysis. However, the inhibitory effect of the R-GICs was not directly related to the fluoride concentrations eluted from them.

Bicuspid↗
PubMed1993

The effect of dietary xylitol on recalcifying and newly formed cortical long bone in rats.

Thirty-six 3-week-old male Wistar rats were labeled with a single intraperitoneal tetracycline injection. Twenty-four of them were then fed a Ca-deficient basal diet for 3 weeks, while the control group received the basal diet supplemented with CaCO3 (12 g/kg). The tetracycline labeling was then repeated and six animals in each group were decapitated. The diet of the remaining formerly Ca-deficient animals was returned to normal, and half the test rats also received xylitol supplementation (50 g/kg). After 4 weeks of rehabilitation the labeling was repeated and the animals were decapitated and their tibias were prepared. The tibias were measured in terms of weight and density and cross sections were prepared for the examination of mineral content. Bone element analysis was performed by scanning electron microscopy with electron-probe microanalysis, examining separately the bone areas formed during the various dietary periods. Areas of the former Ca-deficient and newly formed cortical bone were identified by tetracycline fluorescence under ultraviolet light, and the amount of cortical bone in each group was measured. The mineralization-promoting effect of dietary xylitol as compared with CaCO3 supplementation alone was seen more clearly in the newly formed periosteal bone than in remineralization of the formerly Ca-deficient bone, the concentrations of Ca and P being significantly elevated (P < 0.05), as also was the total mineral content (P < 0.01). The cortical bone volume was similar following the CaCO3 and CaCO3 + xylitol supplementations, suggesting unaltered formation of the organic matrix. The results show that the effect of xylitol on bone during dietary Ca rehabilitation particularly concerns newly formed bone mineral.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Silicone deposition in reconstruction scars of women with silicone breast implants.

BACKGROUND: The possible association of silicone breast implants and disease is a subject of continuous debate and concern. OBJECTIVE: Our purpose was to examine microscopically and ultrastructurally the periprosthetic fibrous capsules and reconstruction scars of women with silicone breast implants. METHODS: Representative samples from the periprosthetic capsules and reconstruction scars from six women with silicone breast implants were examined by a variety of light microscopy techniques, transmission electron microscopy, and electron probe microanalysis. RESULTS: Silicone globules of various sizes were identified in every periprosthetic capsule and reconstruction scar. CONCLUSION: Extrusion and seeding of the incision tract during surgery most likely accounts for the presence of silicone in the reconstruction scar specimens. This observation suggests that the identification of silicone in the reconstruction scars of women with silicone breast implants does not necessarily implicate rupture of the silicone breast implant with systemic dissemination of silicone gel.

Breast Implants↗
PubMed1988

Subcellular electrolyte shifts during in vitro myocardial ischemia and reperfusion.

Isolated perfused rabbit right ventricular wall was studied with electron probe microanalysis (EPMA) under three conditions: 1) control (37 degrees C, 1.2 Hz), 2) 60 min global ischemia, and 3) ischemia plus 5 min of reperfusion. After 60 min of ischemia, only one cell population was evident; the variance of intracellular electrolyte concentrations was the same as in controls. When compared with controls, there was no change in Ca concentration within any region of the cell, but mitochondria were swollen with K-rich fluid. Two cell populations were evident after 5 min of reperfusion. The severely injured cells were markedly swollen, exhibited hypercontraction bands, and had electrolyte profiles similar to extracellular fluid. The moderately injured cells were normal in appearance, still retained electrolyte gradients, but had elevated Na and Cl concentrations in all compartments. Cell Ca did not increase in the moderately injured cells, but the region of the cell containing the sarcoplasmic reticulum (SR) lost 90% of its Ca. Accompanying this loss were large increases in myofibrillar and mitochondrial Ca concentration. It appears that release of SR Ca, loss of SR Ca-accumulating capacity, and increased intracellular Na are the principal electrolyte shifts in functional cells during early reperfusion.

Animals↗
PubMedDate not supplied

Surface analysis of anodic oxide films containing phosphorus on titanium.

PURPOSE: To examine the effect of phosphoric acid solution on the anodic oxide film of titanium. MATERIALS AND METHODS: Commercially pure grade 2 titanium specimens were prepared and anodized in phosphoric acid solution at a constant current density (70 A/m2). Specimens were evaluated by means of scanning electron microscopy, x-ray diffraction analysis, electron probe microanalysis, energy-dispersive spectroscopy, profilometry, and atomic force microscopy. RESULTS: The anodic oxide film was observed to consist of a porous or non-uniform layer and a dense or uniform layer. X-ray diffraction and energy-dispersive spectroscopic analyses indicated that the film consisted of a mixture of anatase and amorphous oxide, with the incorporation of phosphorus. DISCUSSION: The degree of oxide crystallinity was observed to increase with an increase in voltage but decreased as the electrolyte concentration was increased. In addition, the concentration of phosphorus also increased as the electrolyte concentration and voltage increased. CONCLUSIONS: Electrolyte concentration and voltage play an important role in governing the anodic oxide thickness, composition, and degree of oxide crystallinity.

Biocompatible Materials↗
PubMed2000

In vitro effects of zirconia and alumina particles on human blood monocyte-derived macrophages: X-ray microanalysis and flow cytometric studies.

The cytocompatibility of two particulate bioceramics, zirconia and alumina, was studied using human blood monocytes driven to differentiate into mature macrophages with granulocyte macrophage-colony-stimulating factor. Changes in individual cell elemental composition, particularly sodium and potassium content, were assessed by X-ray microanalysis of ultrathin freeze-dried sections. Phagocytosis and respiratory burst of macrophages exposed to biomaterial for 7 days were analyzed under flow cytometry using uptake of fluorescent latex beads and 2'7'-dichlorofluorescien diacetate oxidation, respectively. Zirconia and alumina particles were found to decrease the intracellular potassium/sodium ratio (an index of cell vitality) significantly (p<.01) in 7-day-cultured macrophages compared to control cells cultured out of material. Phagocytosis of both ceramic particles by macrophages was followed by a concomitant decrease in cell phagocytic ability (27%) and a marked altered oxidative metabolism (>2 times reduced by zirconia and >5 times reduced by alumina). The present study clearly demonstrates that reduction of the phagocytic capacity of macrophages associated with altered oxidative metabolism caused by biomaterial particles is characterized by changes in intracellular elemental content. Thus, investigation of cellular homeostasis by electron probe microanalysis together with analysis of functional changes may improve estimation of biomaterial cytocompatibility.

Aluminum Oxide↗
PubMed1987

Effect of time at 37 degrees C on the creep and metallurgical characteristics of amalgam.

When aged at 37 degrees C for six months, dental amalgam exhibits a marked decrease in the property of creep. The objective of this study was to investigate the relationship between this decrease in creep and selected metallurgical characteristics. The formation of beta 1 (Ag-Hg), the grain size of gamma 1 (Ag-Hg), and the composition of gamma 1 were chosen for investigation. Creep was determined according to ADA Specification test No. 1, beta 1 was measured by x-ray diffraction, and gamma 1 grain size and gamma 1 composition were determined by electron-probe microanalysis. The results showed that the decrease in creep was related to beta 1 formation and not to changes in either gamma 1 grain size or gamma 1 composition.

Chemical Phenomena↗
PubMed1992

[Effect of morphological properties on drug release from biodegradable microspheres].

The morphological properties of poly(beta-hydroxybutyric acid) (PHB) or poly(L-lactic acid) microspheres loading flomoxef sodium (FMOX) were investigated with regard to FMOX release. The release profiles of FMOX from the microspheres could be divided into two types, a sustained release type and a burst one. Two representative PHB microspheres, the release profiles of which were quite different from those of FMOX, were compared in detail from a morphological point of view. The shapes of their surfaces and sections were observed by using scanning electron microscopy (SEM), and FMOX distribution was analyzed by using electron probe microanalysis. The crystallinity of polymers was further measured by powder X-ray diffratometry. There was little difference in the FMOX distribution and their microscopic properties such as sphere size, specific surface area, shape of surface and section. In contrast, water penetration into the inside of the microspheres was found to be clearly different by use of cryogenic SEM. A significant difference was also observed in the crystallinity of polymers forming the microspheres. The release of FMOX from the microspheres was affected by the crystallinity of polymers forming the microspheres, and burst phenomena occurred in case the polymer was highly crystallized. It was speculated that the crystallization of polymer induced micro voids in the microspheres which functioned as channels for water penetration.

Biodegradation, Environmental↗
PubMed1982

Changes in Schwann cells and vessels in lead neuropathy.

Transmission electron microscopy (TEM) of peripheral nerve in rats receiving 6% lead carbonate for 4-10 weeks provided evidence of a specific Schwann cell injury, associated with demyelination. Intranuclear inclusions in Schwann cells appeared within 2 weeks of administration of a lead-containing diet. Swelling of Schwann cells and disintegration of their cytoplasm was evident at 4 weeks. Distinctive electron-dense inclusions appeared in both Schwann and endothelial cells during the period of intoxication and were ultrastructurally identical to pathognomonic inclusions of lead poisoning seen in renal tubular epithelial cells. Scanning microscopy (SEM) with electron-probe microanalysis was used to identify the lead-containing deposits. In addition to Schwann cell changes, vessels revealed endothelial cell injury and alteread permeability to macromolecules. Since morphologic changes of Schwann cells precede the development of altered vascular permeability and endoneurial edema, it appears that lead gains access to the endoneurium prior to the development of altered vascular permeability, suggesting that edema and altered endoneurial fluid pressure are epiphenomena that supervene after demyelination occurs. Remyelination, Schwann cell proliferation and formation of onion bulbs are manifestations of persistent toxic injury to myelin-sustaining cells, resulting in chronic demyelination.

Animals↗
PubMed2006

Preparation and characterization of anodized titanium surfaces and their effect on osteoblast responses.

In this study, titanium (Ti) surface was modified by anodizing with a mixture of beta-glycerophosphate sodium and calcium (Ca) acetate, and the anodized surfaces were characterized by scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. In vitro osteoblast response to anodized oxide was also evaluated. The anodic oxide produced was observed to have interconnected pores (0.5-2 microm in diameter) and intermediate roughness (0.60-1.00 microm). In addition, anodic oxide was observed to have amorphous and anatase oxide. Calcium and phosphorus ions were deposited on the Ti oxide during anodization. Osteoblast differentiation, as indicated by alkaline phosphatase production, was enhanced on anodized surfaces. It was thus concluded from this study that Ca phosphate can be deposited on Ti surfaces by anodization. It was also concluded that the phenotypic expression of osteoblast was enhanced by the presence of Ca phosphate and higher roughness on anodized Ti surfaces.

Acetates↗
PubMed2003

Characterization of as-received, retrieved, and recycled stainless steel brackets.

AIM: The purpose of the present study was to investigate the composition and to assess the microhardness and structure of as received, retrieved, and recycled stainless steel brackets. MATERIALS AND METHODS: New, used, and recycled brand-, slot size-, and prescription-matched appliances were subjected to scanning electron microscopy (SEM), energy dispersive (EDS) electron probe microanalysis, metallographic analysis, and Vickers microhardness testing. Elemental analysis was performed on randomly selected bulk material base and wing areas. Basic metal content and microhardness results were statistically analyzed using a two-way ANOVA and the Tukey test, with treatment (as received, retrieved, and recycled) and bracket region (base, wing) serving as discriminating variables (alpha = 0.05). RESULTS: The results showed that there was no alteration in the bulk composition of the brackets among the three conditions. In contrast, differences were noted between bracket base and wing with respect to elemental composition among all groups, implying that the base and wings were manufactured from different alloys. The metallographic etching identified no difference in grain structure between the bracket base and wing components for all groups, regardless of treatment. Vickers microhardness demonstrated significant differences in hardness between base and wing for all groups and between recycled and retrieved states for the wing component.

Electron Probe Microanalysis↗
PubMed1983

The distribution of intracellular ions in the avian salt gland.

To investigate the mechanism of salt secretion in the avian salt gland, we used quantitative electron probe microanalysis to measure the intracellular elemental concentrations in dry cryosections of unspecialized and partially specialized secretory epithelial cells from fresh water- and salt water-adapted ducklings, respectively. In conjunction with this, human and duckling erythrocytes were also analyzed, since these provided the experimental basis for using in situ erythrocytes as standards for determining the local water content of epithelia from the analysis of dried cryosections. The microprobe results from both types of erythrocytes compared favorably with chemical determinations of elemental concentrations. The nucleated avian erythrocytes, whose wet-weight elemental concentrations were determined by a compartmental analysis that required neither a peripheral standard nor a measure of the local mass, revealed a marked accumulation of P and K in the nucleus (388 and 190 mmol/kg wet wt, respectively) relative to the cytoplasm (67 and 85 mmol/kg wet wt). In both developmental states of the epithelial cells, the nucleus and apical cytoplasm had essentially similar and unremarkable concentrations of Na (76 and 83 mmol/kg dry wt, respectively, in the adapted cells vs. 72 and 81 mmol/kg dry wt in the control cells) and K (602 and 423 mmol/kg dry wt vs. 451 and 442 mmol/kg dry wt). Chloride, however, which was in general rather high, was significantly depressed in the apical cytoplasm of adapted cells only (164 and 124 mmol/kg dry wt in the nucleus and cytoplasm, respectively, of adapted cells (P less than 0.05) vs. 138 and 157 mmol/kg dry wt for control cells (P less than 0.05). Cation concentrations (Na + K) were elevated approximately 15% in the basal regions of adapted cells as compared with apical cytoplasm. When tissue water variations are accounted for, the results suggest that: (a) an active, energy-requiring process is responsible for chloride accumulation in this cell; (b) the apical membrane is a regulatory site for secretion; and (c) there are regional distinctions in the distribution of ions and water, particularly in the salt water-adapted cell. These conclusions are consistent with active chloride transport as the basis for salt secretion in this tissue.

Animals↗
PubMed1978

Cytochemistry and x-ray microprobe analysis of the midgut of Tomocerus minor lubbock (insecta, collembola) with special reference to the physiological significance of the mineral concretions.

Histochemical and cytochemical analyses have been made on the mineral concretions within the midgut cells of Tomocerus minor. The classical histochemical methods are not specific and precise enough and have been supplemented with cytochemical techniques on ultrathin sections. The most interesting of these was the K-pyroantimonate technique combined with glutaraldehyde-osmium fixation. This technique shows the distribution of cations such as Ca++, K+, Mg++ and Na+ on the concentric layers of the concretions. Chloride ions can be detected by means of the silver lactate technique. The action of calcium chelators such as E.D.T.A. shows an important distribution of calcium ions in the concretions. The spectra obtained by electron probe microanalysis from areas of fresh, dried and carbon coated midguts as well as from carbon coated semithin or ultrathin sections reveal the presence of Ca, K, Mg, S, Cl and P principally. Other elements such as aluminium, silicon and manganese have also been detected. Iron is not always present. The chemical and X-ray analytical investigations indicate that the midgut concretions are mainly built up of calcium, potassium, magnesium and sodium phosphates, perhaps associated with chlorides and carbonates. An organic matrix formed by polysaccharides seems to join the different mineral layers. These concretions may be formed within the vesicles of rough endoplasmic reticulum. The midgut cells are highly differentiated and very active in transport. Extensive basal infoldings and apical microvilli as well as lateral membranes are a site of small cationic deposits. The possible pathway of ion transport in the cell and the physiological significance of the concretions are discussed. The principal function of these concretions seems to be the maintenance of the mineral balance and to trap foreign and excess ions.

Aluminum↗
PubMed1996

Bonding of a mica-based castable ceramic material with a tri-n-butylborane-initiated adhesive resin.

Adhesive bonding of a mica-based castable ceramic material (Olympus Castable Ceramics, OCC) was evaluated in vitro with the use of a silane primer in conjunction with an adhesive luting material. The primer contained a silane coupler and 4-methacryloxyethyl trimellitate anhydride (4-META), while the methyl methacrylate (MMA)-based luting agent was initiated with a tri-n-butylborane derivative (TBB) and contained 4-META (4-META/MMA-TBB resin). Ceramic specimens were sanded with No. 600 silicon carbide paper followed by blasting with alumina and/or etching with ammonium bifluoride. The specimens were bonded with various combinations and shear bond strengths were determined. Both priming and alumina blasting enhanced the bond between 4-META resin and OCC. Although etching with ammonium bifluoride roughened the ceramic surface, this procedure did not improve the bond strength. Electron probe microanalysis of the ceramic surface revealed a decrease in silicon and aluminium elements after etching with ammonium bifluoride.

Acid Etching, Dental↗
PubMed2005

Age-hardening behaviour and microstructure of a silver alloy with high Cu content for dental application.

Age-hardening behaviour and the related microstructural changes of a silver alloy with relatively high Cu content were elucidated by means of hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and electron probe microanalysis (EPMA). The microstructure of the solution-treated specimen was composed of the Ag-rich matrix, the Cu-rich particle-like structures containing Pd, and the lamellar structure of both phases. By the age-hardening heat-treatment, the Cu element began to precipitate from the Ag-rich matrix by the solubility limit, and the very fine Cu-rich precipitates became coarsened by further aging. The silver alloy with relatively high Cu content showed apparent age-hardenability. The hardness of the solution-treated specimen began to increase and reached a maximum value with increasing aging time, and then the hardness decreased gradually after maintaining the maximum value for short periods of time. The early stage of precipitation of the Cu-rich phase from the Ag-rich matrix seemed to have caused the increase in hardness. The decrease in hardness was attributed to the coarsening of the Cu-rich precipitates in the later stage of the age-hardening process.

Copper↗