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PubMed2004

Characteristics of manganese-coated sand using SEM and EDAX analysis.

"Manganese-coated sand" is a type of silica medium coated with manganese oxides, formed from the sorption of manganese oxides during long-term filtration via the process of rapid sand filtration, followed by aeration in a water treatment plant. Locally available manganese-coated sand, both for packing and as a byproduct of filtration processes for water treatment plants in Taiwan, was found to be a low-cost and promising adsorbent for removal of Mn(2+) from raw water. This study was conducted to build the basic data for coating hydrated manganese oxide on the sand surface to utilize the adsorbent properties of the coating and the filtration properties of the sand. In this study, gas adsorption porosimetry and scanning electron microscopy analyses were used to investigate the surface properties of the coated layer. An energy dispersive X-ray (EDAX) technique of analysis was used to characterize metal adsorption sites on a manganese-coated sand surface. Results indicated that manganese-coated sand had more micropores and higher specific surface area, owing to attachment of manganese sand. Manganese ions penetrated into the micropores and mesopores of manganese oxide on a sandy surface; regeneration of manganese-coated sand could be achieved by soaking with pH < 2.0 acid solution. Results of EDAX analysis showed that the interfacial layer constructed the interface of manganese-coated sand. Acid and alkali resistance tests interpret a wide application range of pH for manganese-coated sand, and general temperature conditions do not affect the performance of this sand. Manganese-coated sand is potentially suitable for application as a packed bed for treatment of heavy metals from water. The results of this study can also benefit plant operational capacity data for engineering design.

Adsorption↗
PubMed2006

Scanning electron microscopic analysis of acrylic intraocular lenses for microincision cataract surgery.

PURPOSE: To analyze the surface quality before and after folding of 2 intraocular lens (IOL) models designed for microincision cataract surgery. SETTING: Eye Clinic and Department of Human Pathology and Oncology, University of Florence, Florence, Italy. METHODS: Two IOL models now available for sub-2.0 mm microincision were studied: UltraChoice 1.0 Rollable ThinLens (ultrathin lens by ThinOptX) and AcriSmart (foldable lens by AcriTec). Eight IOLs of each model were examined. Scanning electron microscopy (SEM) was performed before and after IOL folding with a dedicated injector. Special attention was given to the optic surface and edges, the optic-haptic junction, and the haptic itself. RESULTS: Initially, the surface quality of IOLs was evaluated before folding. On SEM, smooth and homogeneous optic and haptic surfaces were revealed in both IOL models with no surplus material or molding flashes; edge finish of all optics showed no evidence of ridges. The IOL surfaces were evaluated after insertion into their injectors and after ejection at room temperature. After folding, the microincision IOLs showed no sign of surface alteration, probably because of their high water content, which makes these IOLs soft and flexible. CONCLUSIONS: Visual results and long-term biocompatibility of the IOLs are influenced by surface properties. In recent years, there has been a trend toward microincision cataract surgery. Our study shows that the 2 IOL models now available for sub-2.0 mm microincision have acceptable surface properties.

Acrylic Resins↗
PubMed2002

Nanoindentation mapping of the mechanical properties of human molar tooth enamel.

The mechanical behavior of dental enamel has been the subject of many investigations. Initial studies assumed that it was a more or less homogeneous material with uniform mechanical properties. Now it is generally recognized that the mechanical response of enamel depends upon location, chemical composition, and prism orientation. This study used nanoindentation to map out the properties of dental enamel over the axial cross-section of a maxillary second molar (M(2)). Local variations in mechanical characteristics were correlated with changes in chemical content and microstructure across the entire depth and span of a sample. Microprobe techniques were used to examine changes in chemical composition and scanning electron microscopy was used to examine the microstructure. The range of hardness (H) and Young's modulus (E) observed over an individual tooth was found to be far greater than previously reported. At the enamel surface H>6GPa and E>115GPa, while at the enamel-dentine junction H<3GPa and E<70GPa. These variations corresponded to the changes in chemistry, microstructure, and prism alignment but showed the strongest correlations with changes in the average chemistry of enamel. For example, the concentrations of the constituents of hydroxyapatite (P(2)O(5) and CaO) were highest at the hard occlusal surface and decreased on moving toward the softer enamel-dentine junction. Na(2)O and MgO showed the opposite trend. The mechanical properties of the enamel were also found to differ from the lingual to the buccal side of the molar. At the occlusal surface the enamel was harder and stiffer on the lingual side than on the buccal side. The interior enamel, however, was softer and more compliant on the lingual than on the buccal side, a variation that also correlated with differences in average chemistry and might be related to differences in function.

Anatomy, Cross-Sectional↗
PubMed1986

Rabbit alveolar macrophages after inhalation of hexa- and trivalent chromium.

Rabbits inhaled aerosols of hexavalent chromium (Na2CrO4) and trivalent chromium (Cr(NO3)3) at concentrations of 0.9 and 0.6 mg/m3 of the metal, respectively, for 4-6 weeks (5 days/week and 6 hr/day). Significantly more macrophages were obtained from the lungs of rabbits exposed to Cr(VI) but not from rabbits exposed to Cr(III) as compared with the controls. Macrophages from rabbits exposed to Cr(III) showed several conspicuous changes. About one-third of the macrophages contained round dark inclusions, 0.5-1.5 micron diameter, rich in chromium. Most cells had very large lysosomes which contained membranous fragments of different sizes surrounded by a more homogeneous matrix. Laminated inclusions similar to the lamellar bodies in the type II cells increased in number as did the percentage of cells with a smooth cell surface. Also macrophages from rabbits exposed to Cr(VI) showed morphological changes. The most pronounced one was enlarged lysosomes which contained short lamellae and electron-dense patchy inclusions. Only Cr(III) produced functional changes of the macrophages. The metabolic activity measured by reduction of nitroblue tetrazolium was increased and the phagocytic activity reduced.

Animals↗
PubMed1999

Dental diamond burs made with a new technology.

STATEMENT OF PROBLEM: Conventional diamond burs show several limitations such as the heterogeneity of grain shapes, the difficulty of automation during fabrication, the decrease of cutting effectiveness due to repeated sterilization, and short lifetime. An additional shortcoming may be represented by the potential release of Ni+2 ions from the metallic binder into the body fluids. PURPOSE: This study investigated a new diamond rotative instrument made of a continuous diamond film obtained by chemical vapor deposition (CVD). This bur, characterized by a pure diamond cutting surface without metallic binder between crystals, was compared with a conventional diamond bur. MATERIAL AND METHODS: Cutting tests were followed by SEM examination and electron microprobe analysis (EMA) to trace metallic residues both at the surface of the bur and the substrate. RESULTS: EMA demonstrated that the metals Ni, Cr, Si, and Fe were present in the metallic binder matrix of the conventional bur and could be smeared on the surface of the substrate during cutting. SEM showed that significant loss of diamond particles occurred during cutting. On the other hand, no discrete particles sheared off the CVD bur. The smearing of the metallic binder cannot occur using the new bur. CONCLUSION: The new CVD bur not only proves to be more efficient in its cutting ability and longevity, but also excludes the risk of metal contamination. This last aspect concerns both the pollution of the oral environment and the contamination of the ceramic during the laboratory manufacturing of dental restorations.

Dental Instruments↗
PubMed1991

Corrosion pattern of silver points in vivo.

The purpose of this study was to examine the electrochemical behavior of silver points in vivo. The apices of silver points removed from teeth with successful or failed endodontic treatments were subjected to complete surface characterization by small-area ESCA, scanning electron microscopy, and electron probe microanalyzer. Cross-sections of the points near the apex were examined with scanning electron microscopy and electron probe microanalyzer to identify the depth of corrosion involvement. According to the results, all silver points manifested evidence of corrosion attack. Electron probe microanalyzer showed no difference in the elemental distribution found on the points. ESCA analysis of the uppermost 5-nm point layer revealed the presence of N on silver points removed from failed treatments. The examination of cross-sections manifested deep S penetration in the bulk of the points removed from failed treatments. Considering the results of this study, no direct association seems to exist between the extent of the corrosion involvement and the prognosis of the treatment. Handling factors and the presence of bacteria are probably the parameters determining the outcome of a treatment.

Corrosion↗
PubMed2003

A palladium-free gallium-based alloy: analysis of composition and microstructure.

OBJECTIVES: To study the microstructure of a palladium-free gallium-based alloy (Galloy) before and after mixing to identify the metallic phases produced by the setting reaction and assess the quantitative elemental analysis of the phases present. METHODS: The Galloy powder was analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the particle size distribution was determined using a high resolution particle size analyzer. Cylindrical test specimens were mechanically condensed in accordance with ISO 1559: 1986 for XRD, energy dispersive spectroscopy (EDS) and SEM analyses of the set alloy. Disc shaped specimens were prepared by manual condensation to compare the width of the reaction zone with specimens condensed mechanically. RESULTS: The Galloy powder consisted of spherical particles varying between 0.1 and 40 microm in diameter which contained a network of grooves and clefts extending deep within the substance of the particles. The reaction zone appeared 'grainy' and 'fragmented' compared with the well defined reaction zone previously observed for Pd-containing gallium-based alloys. The student t-test indicated the width of reaction zone varied significantly (P<0.001) with method of specimen fabrication.Significance. The significantly larger reaction zone in the manually condensed specimens was possibly due to failure of the condensation technique to force out excessive liquid alloy present in the triturated mass. The surface topography of the Pd-free Galloy powder particles could be responsible for the characteristically fragmented and ill-defined reaction zone observed in the set material compared with the well defined reaction zone previously observed for Pd-containing gallium-based alloys.

Dental Alloys↗
PubMedDate not supplied

Coral graft restoration of osteochondral defects.

The quality of osteochondral repair produced by coral grafted into subchondral bone was examined. Osteochondral defects of 4 mm diameter and 4 mm deep in left femoral grooves of 24 rabbits were repaired using plugs of natural coral or left empty to heal naturally as ungrafted controls. The right knees were kept intact for normal controls. The morphology of the repair tissue, at three and six months post operation, was characterised using histology and by scanning electron microscopy. Resorption of coral and its replacement by new bone was demonstrated using Energy Dispersive X-ray Analysis (EDXA) of the scanning electron microscope. The resorbing coral was gradually replaced by bone at subchondral bone level. The surface tissue matured with time and at six months it was anatomically similar to the adjacent hyaline cartilage: it contained cells that were shaped and arranged in columns similar to the normal controls. The ungrafted controls had healed with fibrous tissue which was often markedly thicker than the adjacent hyaline cartilage and was separated from the surrounding by vertical fissures. Coral grafting of the osteochondral defect enhanced repair of surface tissue.

Animals↗
PubMed1995

Leber hereditary optic neuropathy. Electron microscopy and molecular genetic analysis of a case.

BACKGROUND: Leber hereditary optic neuropathy (LHON) is a mitochondrial genetic disorder characterized by bilateral central visual loss typically in early adulthood. Few histopathologic studies, including ultrastructural and molecular genetic analysis, have been reported. METHODS: Ocular tissue was obtained postmortem from an 81-year-old woman with LHON from the Queensland 1 pedigree characterized by mutations at nucleotide positions 4160 and 14484. Routine histopathologic studies, electron microscopy, electron-probe analysis, and molecular genetic analysis were performed. RESULTS: Marked atrophy of the nerve fiber and retinal ganglion cell layers and optic nerves was present. Results of electron microscopic examination demonstrated 1.2 microns electron-dense, double-membrane-bound inclusions, consisting of calcium by electron-probe analysis, in retinal ganglion cells. The optic nerve was homoplasmic for mutations 4160 and 14484. CONCLUSION: Optic nerve and inner retinal atrophy in LHON may be a result of metabolic mitochondrial dysfunction leading to intramitochondrial calcification. Homoplasmy for mitochondrial mutations 4160 and 14484 in the leukocyte/platelet fraction of whole blood may correlate with homoplasmy in the optic nerve.

Aged↗
PubMed1987

Argyria: the intradermal "photograph," a manifestation of passive photosensitivity.

X-ray microprobe and electron microscopic study was made of the remarkable blue-black pigmentation that sunlight elicits in patients with argyria. The patient under study had developed argyria following injection of silver nitrate as a sclerosant into his varicose veins 41 years ago. Similarities are demonstrated between the darkening of the skin and the darkening of a photographic film following light exposure. In both instances, colorless silver salts and compounds present in an inert matrix (collagen versus gelatin) are reduced by incident light to black metallic silver. This passive photosensitivity reaction leads to silver tattooing of the light-exposed skin and to photographic imaging in the film.

Aged↗
PubMed1999

The biaxial flexural strength of two pressable ceramic systems.

The biaxial flexural strength of Optimal pressable ceramics and IPS Empress pressable ceramics were tested, compared and the micro-structures and compositions explored. The materials evaluated were Optimal shaded (Opcs) and unshaded (Opcus) ceramics and IPS Empress shaded (Ems) and unshaded (Emus) ceramics. Twenty-one disc specimens per material were prepared, heat-treated and tested. The piston on three-ball test ASTM F394-78 (1991) was used to test the specimens in a universal testing machine at a crosshead speed of 0.15 mm/min. Specimens were viewed in a scanning electron microscope and X-ray diffraction used to determine the phases present. Mean strengths (MPa +/- SD) were: Ems 120.1 +/- 20.5, Emus 135.8 +/- 16.0, Opcs 139.1 +/- 14.3 and Opcus 138.0 +/- 11.5. There was no statistically significant difference between Optimal shaded, Optimal unshaded and Empress unshaded strength values (p > 0.05). Empress shaded strength values were significantly lower than the other materials tested (p < 0.05). Weibull analysis provided m values: Ems 6.1, Emus 10.2, Opcs 12.8 and Opcus 13.9 and 1% and 5% probabilities of failure. Secondary electron imaging revealed a dense dispersal of leucite crystals in the glassy matrix of the Optimal ceramics of an average size 5.5 +/- 9.7 micron 2 for the Optimal shaded ceramic and 6.6 +/- 13.3 micron 2 for the Optimal unshaded ceramic. Leucite crystal agglomerates were evident for the Empress shaded material and a uniform distribution of fine leucite crystals (1.9 +/- 1.8 micron 2) for the Empress unshaded ceramic. Crystal and matrix microcracking were present in most of the material microstructures, together with porosity and tabular alumina platelets in the Optimal ceramics. X-ray diffraction revealed the presence of tetragonal leucite and small amounts of cubic leucite. Optimal ceramics and Empress unshaded ceramic provided higher strength and Weibull m values compared with Empress shaded ceramic. Inherent material defects were characterised and cubic leucite was identified.

Aluminum Silicates↗
PubMed1999

Particle-induced X-ray emission and scanning electron microscopic analyses of the effects of CO2 laser irradiation on dentinal structure.

OBJECTIVES: The purpose of this study was to analyze the physico-chemical changes present on the dentinal surface after using CO2 laser irradiation, and to determine whether or not it is possible to seal the dentinal tubules. METHODS: Thirty human-extracted first premolars were obtained for this study. A Class V cavity was prepared on the buccal surface of all the specimens with a carbide pear-shaped bur, using a conventional high speed handpiece. Fifteen premolars (experimental group) were irradiated with a CO2 laser (with a wavelength of 10.6 microm, 2 W, 10 J, 0.2 s, 25 pulses). The remaining 15 premolars were used as the control group. RESULTS: Scanning electron microscopy showed that the effect of laser energy on dentin varied from charring, cratering, poring, fissuring, fracturing and cracking up to melting; also, the dentinal tubules were not sealed, in contrast with the control group in which the dentinal surfaces were more homogeneous. Particle-induced X-ray emission results showed that the irradiated dentinal surface presented a decrease in calcium content and an increase in phosphorous content, possibly due to a vaporization process which occurred during the irradiation. CONCLUSION: The physicochemical changes observed on the irradiated dentinal surface suggest that changes in the hydroxyapatite crystal structure take place, and that these structural changes may be responsible for the observed effects.

Bicuspid↗
PubMed1998

Contact-angle analysis of intraocular lenses.

PURPOSE: To present contact-angle measurements of commercially available intraocular lenses (IOLs) in air and in water to facilitate the understanding of how various IOLs might interact in different environments. SETTING: Laboratory. METHODS: Five commercially available IOLs were studied: AMO DuraLens PS-59NB. AMO PhacoFlex SI-26NB, AMO PhacoFlex II SI-30NB, Chiron ChiroFlex C10UB, and Alcon AcrySof MA60BM. The AMO soft acrylic model AR40, currently under clinical study, was also evaluated. Contact-angle measurements were made in air and in water using sessile drop and captive bubble methods. RESULTS: The sessile drop method indicated that all materials were hydrophobic in air. The captive bubble method differentiated materials based on their polar and dispersive forces. CONCLUSION: Contact-angle measurements differed depending on the test conditions. Proper choice of contact-angle measurement method can generate useful information about a material surface and its potential biomaterial interactions.

Acrylates↗
PubMed2003

Redeposition effects in transmission electron microscope specimens of FeAl-WC composites prepared using a focused ion beam.

Artifacts associated with transmission electron microscope (TEM) specimens prepared using a focused ion beam (FIB) are not well understood, especially those in non-semiconductor materials. In this paper the extent and origins of artifacts associated with redeposition of milled material in TEM specimens of a FeAl--WC metal matrix composite prepared by FIB were investigated. Cross-sections were prepared normal to an initial FIB cut that allowed direct observation of any damage layers, which are believed to be associated with both redeposition of sputtered material and amorphisation of the surface of the specimen by the ion beam. Techniques for the minimisation of redeposition using either final cleaning mills at low accelerating voltages or plasma cleaning were also investigated and found to be ineffective in removing or reducing these damaged layers. TEM cross-sections of specimens treated using low energy mills and plasma cleaning, further confirmed that these techniques did little to reduce any redeposited or amorphous material.

Aluminum Compounds↗