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PubMed1987

Cell fractions from rat rib growth cartilage. Morphological and X-ray microanalytical investigation.

For in vitro studies of differentiation and proliferation of chondrocytes, a need arose to prepare enriched cell fractions for analysis of the effects of different growth promoting factors. Therefore chondrocytes were isolated from rat rib growth cartilage in young rats by collagenase digestion and subsequently three cell fractions were prepared by centrifugation in a step gradient of Percoll. In a previous paper, matrix molecules synthesized by each fraction were characterized biochemically. In the present study, ultrastructure and elemental content of the fractionated chondrocytes were analyzed by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray microanalysis. DNA-synthetic activity was measured by means of autoradiography of 3H-thymidine incorporating cells. Both morphology and elemental concentrations differed between fractions and were characteristic for each fraction. The cell fraction with the lowest density consisted of large, polygonal cells that became flattened in culture. The reduced synthetic activity and markedly lowered K content of these cells suggest that they originate from the hypertrophic zone of the growth plate. The cells in the fraction with the highest density were rather homogeneous in size and shape, and had a well developed rough endoplasmic reticulum and Golgi complex, characteristic of proliferating and resting chondrocytes. Concentrations of P and K were also significantly higher in this fraction. The fraction with intermediate density contained an admixture of cells with a predominance of proliferating cells with high DNA-synthetic activity.

Animals↗
PubMed1988

Corrosion of dental burs in sterilizing and disinfecting solutions.

Potentiodynamic anodic polarization, SEM, and energy dispersive microanalysis techniques were used to determine electrochemical aggressiveness of disinfecting and sterilizing solutions on carbide and stainless steel burs. The importance of galvanic cell formation in carbide burs caused by mixed metal coupling was examined. The following conclusions were reached. 1. Anodic polarization methods are an effective means for discriminating among the relative corrosiveness of sterilizing and disinfecting agents on dental instruments, particularly dental burs. 2. The relative degree of corrosiveness on stainless steel burs shows Omni II and Omnicide solutions the best, Sterall and Sporicidin solutions the poorest, and Glutarex solution intermediate. Omnicide and Glutarex solutions show the least degree of corrosiveness on the carbide burs. 3. SEM analysis of ground, polished, and treated surfaces shows corrosion deposition over the soldered joint of the carbide burs. The stainless steel shank is a cathodic component of a three-way galvanic cell, whereas the silver soldered joint is an anodic component.

Carbon↗
PubMed2006

Sub-second calcium coupling between outside medium and subplasmalemmal stores during overstimulation/depolarisation-induced ciliary beat reversal in Paramecium cells.

As amply documented by electrophysiology, depolarisation in Paramecium induces a Ca(2+) influx selectively via ciliary voltage-dependent Ca(2+)-channels, thus inducing ciliary beat reversal. Subsequent downregulation of ciliary Ca(2+) has remained enigmatic. We now analysed this aspect, eventually under overstimulation conditions, by quenched-flow/cryofixation, combined with electron microscope X-ray microanalysis which registers total calcium concentrations, [Ca]. This allows to follow Ca-signals within a time period (> or =30ms) smaller than one ciliary beat ( approximately 50ms) and beyond. Particularly under overstimulation conditions ( approximately 10(-5)M Ca(2+) before, 0.5mM Ca(2+) during stimulation) we find in cilia a [Ca] peak at approximately 80ms and its decay to near-basal levels within 110ms (90%) to 170ms (100% decay). This [Ca] wave is followed, with little delay, by a [Ca] wave into subplasmalemmal Ca-stores (alveolar sacs), culminating at approximately 100ms, with a decay to original levels within 170ms. Also with little delay [Ca] slightly increases in the cytoplasm below. This implies rapid dissipation of Ca(2+) through the ciliary basis, paralleled by a rapid, transient uptake by, and release from cortical stores, suggesting fast exchange mechanisms to be analysed as yet. This novel type of coupling may be relevant for some phenomena described for other cells.

Animals↗
PubMed1982

Some considerations regarding the degradational interactions between mouth rinses and silver-soldered joints.

For immersion tests with mouth rinses of Lavoris, Green Mint, and Cepacol, silver solders and silver-soldered stainless steel joints exhibited corrosive degradational reactions. Exposures to Lavoris resulted in the severest surface attack as followed by optical microscopy, scanning electron microscopy, and energy-dispersive x-ray microanalysis. This was confirmed by measurements of electrochemical potential and polarization. The cyclic voltammograms in Lavoris indicated a highly active corrosion potential of -0.94 v. sce, while potentials in Mint and Cepacol were only about -0.25 v. This activity is attributed to the presence of zinc chloride as the active agent in Lavoris, as well as the high zinc content (up to about 20 percent) and even higher zinc concentrations contained in copper-zinc microstructural phases of the silver solders and the ease for dezincification corrosive attack. Large increases in current above about -0.2 v. are observed with all rinse solutions as well as a prepared saliva substitute solution. The importance of toxicologic considerations of the agents released from silver solders and the interactions of corrosion with stress as factors in causing delayed failures of soldered joints are discussed. The presently available commercial solders without cadmium and zinc contents, but with higher fusion temperatures and decreased flow characteristics, are recommended for dental applications to increase the resistance to corrosion.

Chemical Phenomena↗
PubMed1984

Mineralization of short term pericardial cardiac patch grafts.

Glutaraldehyde fixed patch grafts of bovine pericardium were implanted in myocardial windows in young (3-4 months old) sheep. The samples were retrieved after one to three weeks for study with scanning electron microscopy (SEM) and energy dispersive x-ray microanalysis (EDX). A layer of porous material (pseudoneointima, PNI), consisting mostly of a dense mesh of fibers interspersed with blood cells, was noted to form on the blood contacting surface of the graft. Four distinct sets of mineralization were noted in the retrieved grafts: (1) at the blood contacting surface of the PNI; (2) within the PNI at the junction between layers of PNI with differing densities; (3) near the junction of PNI and pericardium (but in the PNI); and (4) within the pericardium. In both the PNI and pericardium the mineral was shown by EDX analysis to contain both calcium and phosphorous indicating the mineral to be a calcium phosphate. Mineralization in the PNI differed from that in the pericardium; in the PNI it was deposited in discrete regions and apparently in association with thrombi while in the pericardium it was distributed diffusely within the collagen matrix, which may influence its formation.

Animals↗
PubMed2006

Experimental studies on the effect of osteotomy technique on the bone regeneration in distraction osteogenesis.

The objective of the experiment was to study the effect of osteotomy technique on the course of bone regeneration in distraction osteogenesis in sheep. Thirty five merino sheep were divided into 5 groups of 7 sheep each, depending on the osteotomy technique: subcutaneous corticotomy, open corticotomy, Cattaneo corticotomy, open osteotomy and osteoclasia. Formation of regenerate and its remodeling was assessed, based on roentgenograms and morphological examination (bone sections, histological evaluation, SEM, superficial X-ray analysis). Irrespective from the osteotomy technique applied, in all experimental groups, regenerates filling the distraction gap were obtained. Analysis of bone sections and histological slides indicated the most advanced osteogenesis processes in the osteoclasia group. SEM examination and X-ray microanalysis confirmed not only the presence of mature bone tissue structures in this group, but also showed a mineralization close to that of a healthy bone. Osteogenesis was the slowest in the group of subcutaneous corticotomy. The observed histological picture and analysis of elemental composition indicate a normal course of distraction osteogenesis in this group, but its consecutive phases proceed with a certain delay, compared to the remaining groups. With a good deal of caution, it can be assumed that the delay of osteogenesis in the group of subcutaneous corticotomy in the 14th post-operative week was ca. 3 weeks compared to the osteoclasia group. In all experimental groups, few cartilaginous nodules were observed in regenerates 5 weeks and, in few cases, 9 weeks old. Ossification in such places was indirect, cartilage-based. In the remaining regions direct, membrane-based ossification prevailed. Direct apposition bone lamellae on islands of fibrous bone tissue was observed in regenerates aged 9 and 14 weeks, especially in periosteal regions. The intensity and rate of formation of new bone tissue varied between the experimental groups, based on roentgenological analysis and histological evaluation. Complex morphological studies on the course of regeneration in sheep showed the most advanced remodeling and mineralization of bone tissue in animals subject to osteoclasia.

Animals↗
PubMed1989

Microscopy analysis of dental titanium casting investment materials.

Scanning electron microscopy (SEM) analysis and qualitative energy dispersive x-ray microanalysis (EDS) of investment materials for dental titanium casting were performed. Two commercial investment materials, Ohara and Castmatic, and an experimental zirconia material were analyzed. The microstructural constituents and the unfired and fired structures were included. Larger refractory particles and matrix embedding smaller particles were observed with each material. Detection of aluminum, silicon, magnesium, zirconium and oxygen provided a basis to reason the presence of alumina (Al2O3), silica (SiO2), magnesia (MgO), and zirconia (ZrO2). Hence, Ohara contained quartz and an alumino-silicate, Castmatic contained magnesia and quartz and experimental zirconia contained zirconia and an alumino-silicate, taken to be kyanite, as components providing refractoriness and expansion. Even though unequivocal detection of phosphorous in the spectra for Ohara was not obtained (P K alpha = 2.013 keV; Zr L alpha = 2.042 keV), an emission peak at 2.0 keV was taken to be due to P and related, along with MgO, to bonding by magnesium phosphate. For Castmatic, unfired strength was thought to be due to calcium chloride and calcium silicate and fired strength to forsterite, (2MgO.SiO2). Detection of calcium and chlorine also suggested bonding of experimental zirconia via calcium chloride. Extensive microcracking occurred around refractory particles and through matrix in experimental zirconia which is likely to have resulted from the firing of kyanite to 1400 degrees C, to the monoclinic to tetragonal transformation of any unstabilized ZrO2, or to the thermal expansion mismatch between kyanite and matrix.

Dental Casting Investment↗
PubMed1998

Effects of microstructure on the corrosion behavior of CoCr porous coatings on orthopedic implants.

Cobalt-chromium alloy porous coatings have become increasingly popular as a means of achieving a stable, longer lasting fixation on orthopedic implants. However, sintering heat treatments cause changes in the microstructure that result in changes in the corrosion behavior of the porous coatings. Experiments were conducted to examine the effects of microstructure on the corrosion of CoCr porous coatings. Four distinct microstructures were characterized. Light microscopy revealed microstructures A and B had relatively fewer carbides and a large-grain structure, microstructures C and D displayed a finer grain size with significant carbide formation, predominantly within grains and fusion zones. Accelerated anodic corrosion experiments were conducted to study the localized attack of each microstructure. Experiments were conducted using metallographically polished porous-coated disks for durations of 1, 4, 16, 24, and 72 h. The disks were examined with SEM and EDS to observe preferential attack and element depletion. Results showed a progressive dissolution of the matrix, with preferential attack of the grain boundaries and regions adjacent to the carbides due to sensitization. A precipitation layer was found to be Cr-rich and possibly composed of chromium hydroxide or a chromium orthophosphate. In addition, the solution became yellow in color with longer exposure times, possibly due to the presence of chromate ions, as indicated by an increased chromium level detected by AAS.

Alloys↗
PubMed2001

The formulation of powder inhalation systems containing a high mass of nedocromil sodium trihydrate.

Nedocromil sodium trihydrate is not amenable to conventional methods of dry powder inhaler formulation, including the preparation of coarse carrier systems and aggregation of the pure drug powder. It is considered that the in vitro aerosol performance of such systems is governed by the cohesive drug-drug interactions. Therefore, alternative powder formulation strategies (novel to nedocromil sodium) were developed. By decreasing the particle size of the lactose carrier, the deaggregation and subsequent fine particle drug deposition were significantly improved. Further improvements were made by selecting and then optimizing high-shear mixing procedures. It was concluded, based on these findings and supportive microscopic studies (low-temperature and environmental scanning electron microscopy together with energy-dispersive X-ray analysis), that the FPL are producing their functional effects by intercalating within the drug self-agglomerates and physically disrupting the cohesive drug-drug interactions. The use of a smaller-sized lactose fraction in conjunction with a blending procedure capable of optimally disrupting the drug self-agglomerates allowed maximal intercalation of the excipient material within the drug self-agglomerates. The adhesive drug-FPL interactions are considered to be weak compared with the cohesive drug-drug particle interactions, cohesive interactions that would normally govern the aerosol performance of powder systems containing a high mass of nedocromil sodium trihydrate.

Aerosols↗
PubMed1984

In vivo metal-ion release from porous titanium-fiber material.

Dense and porous Ti, Ti-alloy, and stainless steel specimens were implanted in canine trabecular bone. After 6 and 12 months the specimens were retrieved together with bone tissue immediately adjacent. The trace metal content in the tissue samples was determined using neutron activation analysis, differential pulse polarography, graphite furnace atomic-absorption spectrophotometry, electron microprobe analysis, and laser microprobe analysis. The results are discussed in view of (i) the release of Ti ions, which is larger for porous than for bulk specimens, (ii) the various artifacts arising in electron microprobe (EMP) and laser microprobe mass analysis (LAMMA) determination of compositional gradients of trace metal-ion content in bone tissue, (iii) the absence of measurable quantities of V in bone tissue, and (iv) the difference in local tissue accumulation between Ti, released from Ti specimens, and Ni, released from stainless steel specimens.

Alloys↗
PubMedDate not supplied

Bone bonding behavior of three kinds of apatite containing glass ceramics.

We have produced three kinds of apatite-containing glass ceramics of the same chemical composition: MgO (4.6), CaO (44.9), SiO2 (34.2), P2O5 (16.3), CaF2 (0.5) (in weight ratio). They contain different crystal combinations and have different mechanical properties. The first glass ceramic (A-GC) was prepared by heating a glass plate to 870 degrees C. It contains only oxy- and fluoroapatite (35 wt%). The second glass ceramic (A-W-GC), and the third (A-W-CP-GC), were prepared by heating glass powder compacts to 1050 degrees C and 1200 degrees C, respectively. A-W-GC contains oxyapatite and fluoroapatite (Ca10(PO4)6(O,F2] (35 wt%) and beta-wollastonite (40 wt%). A-W-CP-GC contains oxyapatite and fluoroapatite (20 wt%), beta-wollastonite (CaO X SiO2) (55 wt%), and beta-whitlockite (3CaO X P2O5) (15 wt%). The bending strengths of A-GC, A-W-GC, and A-W-CP-GC were 88MPa, 178MPa, and 213MPa, respectively, in air. Rectangular ceramic plates (15mm X 10mm X 2mm) were implanted into a rabbit tibia. Ten and 25 weeks after implantation, the segment of tibia with implant was excised for examination. The segment was held by a special jig and the traction breaking load (failure load) was measured by an autograph. A-GC showed a lower load than A-W-GC and A-W-CP-GC. The loads for A-W-GC and A-W-CP-GC were almost equal. The failure loads did not change significantly between 10 and 25 weeks for any of the materials. The interface was examined by Giemsa surface staining, contact micro-radiography, and SEM-EPMA. Giemsa surface staining and CMR revealed direct bonding between the materials and the bone for all the three materials. SEM-EPMA showed that Si and Mg content decreased, Ca content did not change, and P content increased at the reaction zone between all three glass ceramics and bone. This was observed at 10 weeks, as well as at 25 weeks, after implantation. The reaction zone was narrowest with A-GC, wider with A-W-GC, and widest with A-W-CP-GC.

Animals↗
PubMed1989

Transformation of biphasic calcium phosphate ceramics in vivo: ultrastructural and physicochemical characterization.

Specially prepared biphasic calcium phosphate (BCP) macroporous ceramics consisting of an intimate association of beta tricalcium phosphate (beta-TCP) and hydroxyapatite (HA) with beta-TCP/HA weight ratios of 15/85, 35/65, and 85/15 were implanted in surgically created periodontal osseous defects in dogs and recovered after 6 months. A decrease in average size of crystals in BCP ceramics and an increase in the size of microporosities in the surface and at the core of the ceramic after implantation were observed, indicating that in vivo dissolution has taken place. The resorbability (reflecting in vivo dissolution) of BCP ceramics depended on their beta-TCP/HA ratios, the higher the ratio, the greater the resorbability. The formation of microcrystals with crystallographic properties and Ca/P ratio similar to those of bone apatite crystals were also observed. The abundance of these crystals were directly related to the beta-TCP/HA ratio of the BCP ceramic before implantation. The formation of the bone apatite-like crystals may be due to the precipitation of calcium and phosphate ions released from the dissolving ceramic crystals (the beta-TCP component dissolving preferentially to the HA component). Results from this study suggested that one of the means of controlling resorbability (in vivo dissolution) of BCP ceramic is by varying its beta-TCP/HA ratio.

Animals↗
PubMed1991

The bonding behavior of calcite to bone.

Plates of calcite (CaCO3) were implanted in rabbit tibiae, and their biocompatibility and bonding ability to bone were studied. The plates were also implanted subfascially in rabbit muscle for 8 weeks, and changes on their surfaces in the body were examined. Contact microradiography and Giemsa surface stain demonstrated direct bonding between calcite and bone without interpositions. The average failure load of the interface between calcite and bone was 4.11 kg, indicating an adequate strength of bonding. However, a Ca-P-rich layer, which formed on the surfaces of other bioactive ceramics in vivo, was not detected by a scanning electron microscope-electron probe x-ray microanalyzer. Scanning electron micrographs of the surface of calcite implanted subfascially for 8 weeks showed marked degradation and a rough surface. However, the surface apatite layer was not detected by thin-film x-ray diffraction analysis and Fourier transform infrared reflection spectroscopy. Calcite is a biodegradable material that bonds to bone without a surface apatite layer. The mechanical bonding provided by the anchoring effect of the newly formed bone into the surface roughness of calcite is considered to be a major factor in calcite-bone bonding.

Animals↗
PubMed1995

Nitric acid passivation of Ti6Al4V reduces thickness of surface oxide layer and increases trace element release.

Passivation of Ti6Al4V and cpTi implants using methods based on the ASTM-F86 nitric acid protocol are used with the intention of reducing their surface reactivity, and consequently the corrosion potential, in the highly corrosive biologic milieu. The ASTM-F86 passivation protocol was originally developed for surgical implants made of stainless steel and chrome cobalt alloy. Using X-ray photoelectron spectroscopy (XPS) to examine the effect of nitric acid passivation on the surface oxide layer of mill-annealed Ti6Al4V and cpTi, we have found that such treatment actually reduced the oxide thickness on the alloy while having no significant effect on the pure metal. These results correlated with observations obtained using graphite furnace atomic absorption spectrophotometry (GFAAS) to detect trace element release from solid, mill-annealed, Ti6Al4V and cpTi into serum-containing culture medium. We detected significantly greater levels of Ti, Al, and V in the presence of passivated compared to nonpassivated Ti6Al4V. In contrast, nitric acid passivation did not influence Ti release from mill-annealed cpTi. These results, derived from two mill-annealed Ti-based metals, would indicate that re-examination of ASTM-F86-based passivation protocols with respect to Ti6Al4V should be considered in view of the widespread use of this alloy for biomedical devices.

Alloys↗
PubMed2004

Surface modification of titanium implant by microarc oxidation and hydrothermal treatment.

Surface modification of titanium implant is processed by microarc oxidation and hydrothermal treatment. A porous surface with a biologically active bone-like apatite layer was formed. The apatite layer consists of very fine crystals and high crystallinity and is integrated with the titanium alloy substrate with a graded structure without a distinct interface. Such a bioactive layer is expected not only to enhance the bony ingrowth into the porous structure, but also to improve the interlocking between implant and bone.

Alloys↗
PubMed1987

Quasicrystals and noncrystallographic symmetry.

New findings on quasicrystals with icosahedral, octagonal, decagonal, and dodecagonal symmetries obtained recently in the Beijing Laboratory of Electron Microscopy, Chinese Academy of Sciences, are presented. Special emphasis is put on the relation between quasicrystalline and crystalline structures. The important role played by electron diffraction and high-resolution electron microscopy in revealing these quasiperiodic structures is pointed out.

Crystallography↗
PubMed1987

Microdiffraction and analysis.

The intensity distribution in the microdiffraction pattern depends strongly on the coherence of the illuminated source. The coherence width at the specimen level is considered as a parameter to check the coherence of an electron microscope. Two application examples are illustrated. A small interphase precipitate of MgNi2 in an Ni superalloy has been identified by a combination of microdiffraction and energy dispersive spectrum (EDS) techniques, though it can not be found by conventional transmission electron microscopy (TEM) and selected area diffraction (SAD). By means of microdiffraction as well as high-resolution electron microscopy (HREM) imaging a defect structure has been determined. Such a defect makes the lattice extinction spots appear with various intensities in the selected area diffraction and microdiffraction patterns.

Electron Probe Microanalysis↗