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PubMed1999

Characterization of the interface between prefabricated gold copings and cast dental alloy in implant restorations.

The objective of this study was to analyse the characteristics of the metal interface between the casting of a dental noble alloy and prefabricated gold copings (OCTA-ITI Implant System) after the fabrication procedures of a prosthetic implant-retained superstructure. The microscopical investigation, performed by optical microscopy (OM) and scanning electron microscopy (SEM), of the region around the cylinder after the casting process and the subsequent porcelain firing procedures showed the presence of an ideal interface, including: i) maintenance of coping and casting alloy microstructures up to the interface, and ii) absence of interfacial reaction products. A low content of porosity (less than 3% by volume in average) was observed in the casting alloy bulk as well as at interface. The investigation by energy-dispersive spectroscopy (EDS) of the alloy composition close to the interface showed the presence of a minimal elemental interdiffusion, suggesting that an adequate compatibility between alloy and coping characterized the materials used. A small decrease of the prefabricated coping hardness was also observed after the casting and porcelain firing procedures.

Dental Abutments↗
PubMedDate not supplied

Arc Welders' pneumoconiosis: application of advanced scanning electron microscopy.

Study of lung tissue from necropsy of a 58-year-old arc welder with arc welders' pneumoconiosis, confirmed by history, chest radiography, and pathology, demonstrates the versatility and usefulness of new techniques in scanning electron microscopy (SEM). Secondary electron imaging, the most familiar SEM mode, showed heavy cellular infiltrates in alveoli, the interstitium, and within the interstices of loose whorled fibrotic nodules. Backscattered electron imaging, in which contrast is proportional to elemental atomic number, revealed intracellular metal particles not otherwise visible. Microprobe analysis, energy-dispersive x-ray spectrometry, mapped elemeental iron over the particle image and identified traces of silicon in the whorled nodules. Arc welders' pneumoconiosis appears to be more than a benign siderosis resulting from particulate iron deposition. Simultaneous exposure to other components of welding fumes may alter the pathologic picture, inducing a more complicated fibrotic reaction. The more recently developed advanced techniques of SEM are well suited to the study of pneumoconioses and other problems of heterogenous tissue and mixed chemical systems.

Electron Probe Microanalysis↗
PubMed1995

Bone formation in rabbit cancellous bone defects filled with bioactive glass granules.

We examined new bone formation after filling cancellous bone defects with bioactive glass (BG) in granular form. Cylindrical defects in the trochanter area of 18 rabbit femora were filled with BG granules (diameter 600-830 microns) and compared with similar defects filled with morcellized autogenous bone. New bone formation and surface reaction of BG particles were evaluated by light microscopy, histomorphometry, and scanning electron microscopy. The chemical profile at the bone- material interface was studied by energy dispersive x-ray analysis (EDXA). In the BG group, 41, 32, and 38 percent of the defects were filled with new bone after 3, 6, and 12 weeks, respectively. The corresponding figures for the autogenous bone group were 36, 29, and 34 percent. The thickness of the reaction layer on the glass surface increased from 82 to 163 microns during the observation periods. An intimate contact without intervening soft tissue between new bone lamellae and BG granules was a constant finding. EDXA showed a chemical continuum between the granules and the new bone. No adverse reactions related to BG were observed. BG is a promising material for filling cancellous bone defects.

Animals↗
PubMed2004

A comparative study of white mineral trioxide aggregate and white Portland cements using X-ray microanalysis.

The purpose of this study was to determine and compare the composition of white mineral trioxide aggregate (WMTA) and two different white Portland cements (WPCs). Samples of WMTA and WPCs were prepared and then imaged in a JEOL JSM6400 scanning electron microscope, equipped with an Oxford Instruments light element energy dispersive spectrometer detector for determining the elemental composition. Electron probe microanalysis (EPMA) results indicated that lime (CaO) and silica (SiO2) were the dominant compounds in each case. The results showed that the trace elements are similar in all of the samples but there was no detectable trace of bismuth oxide (Bi2O3) in WPCs. The range of crystal sizes observed in WMTA was found to be distinctly smaller than those observed in the WPCs. It was concluded that there is no significant difference between the dominant compounds in both WMTA and WPCs except the presence of bismuth oxide in WMTA.

Aluminum Compounds↗
PubMed1989

Bacillus-shaped deposits composed of hexahedrally based crystals in human dental calculus.

In human supra- and subgingival calculus, bacillus-shaped deposits showing various rocky-pile forms composed of hexahedrally based crystals were observed by scanning electron microscopy. The crystal size measured approximately 0.1-1.5 microns. The electron probe microanalysis always detected calcium, phosphorous, and magnesium. Their molar ratios resembled those of magnesium-containing whitlockite and moreover the crystals also gave the electron diffraction pattern of whitlockite. The bacillus-shaped deposits happened to coexist with the intracellular calcifying microorganisms, furthermore, oral microorganisms partially replaced by the hexahedrally based crystals were found. The crystal deposits were never seen in the surface layers of calculus exposed to the oral cavity, but occurred in the innermost layers and intra-spaces of supragingival and ledge-type subgingival calculus and in the outer layers of deep subgingival calculus.

Bacillus↗
PubMed2001

High-resolution constant-height imaging with apertured silicon cantilever probes.

We present high-resolution aperture probes based on non-contact silicon atomic force microscopy (AFM) cantilevers for simultaneous AFM and near-infrared scanning near-field optical microscopy (SNOM). For use in near-field optical microscopy, conventional AFM cantilevers are modified by covering their tip side with an opaque aluminium layer. To fabricate an aperture, this metal layer is opened at the end of the polyhedral probe using focused ion beams (FIB). Here we show that apertures of less than 50 nm can be obtained using this technique, which actually yield a resolution of about 50 nm, corresponding to lambda/20 at the wavelength used. To exclude artefacts induced by distance control, we work in constant-height mode. Our attention is particularly focused on the distance dependence of resolution and to the influence of slight cantilever bending on the optical images when scanning at such low scan heights, where first small attractive forces exerted on the cantilever become detectable.

Journal Article↗
PubMed1989

Dentine hypersensitivity. II. Effects produced by the uptake in vitro of toothpastes onto dentine.

Toothpastes arguably are the most common preparations used in the treatment of dentine hypersensitivity. Evidence for efficacy largely comes from clinical trials, and supports the role of the contained so-called "active" ingredient. How such compounds produce therapeutic benefit has received limited attention. This study measured the availability and uptake onto dentine of fluoride and metal ions contained in commercial and test toothpastes. The effects of exposure of dentine sections to these toothpastes, and abrasive only pastes in particular, was investigated by scanning electron microscopy and X-ray microanalysis. Aqueous extracts of the different toothpastes contained measurable concentrations of the incorporated metal and or fluoride, but usually considerably below that incorporated by the manufacturer. Extraction of dentine sections exposed to toothpaste slurries revealed levels of fluoride and metal ions, although post-treatment washing in water reduced these levels. Surface changes at 1 and 10 h were not consistent with the uptake of fluoride or metals. These changes were almost certainly produced by the contained abrasives, including calcium carbonate, dicalcium phosphate, alumina and silica. In particular fume silica progressively accumulated on the dentine surface to narrow and occlude dentinal tubules. Unlike other abrasives fume silica was resistant to removal by washing. It would appear that insufficient attention has been given to the therapeutic potential of toothpaste ingredients, particularly abrasives, to produce benefit by occlusion of dentinal tubules.

Dentifrices↗
PubMed2000

Elemental changes in skin from patients with basal cell carcinoma.

Intracellular ionic shifts have been described in connection with normal and abnormal cell proliferation. This study was conducted to determine the elemental composition of a cell tumor classified as basal cell carcinoma in skin. The biopsies were taken from 10 patients. Control biopsies were taken from the non-affected skin from the same patients. Cryosections were cut and attached to carbon specimen holders. After freeze drying the sections were analyzed by X-ray microanalysis in a scanning microscope. The X-ray microanalytical results showed that the content of magnesium, phosphorus and potassium was significantly higher in the cancer cells than in the control cells (p < 0.05). The content of sodium, chlorine, calcium and sulfur was similar in both affected and unaffected cells. We conclude from these data that basal cell carcinoma has a characteristic elemental composition. It is possible that increased potassium and magnesium levels have a stimulatory effect on this tumor type, in contrast to other types of cancer cells where elevated sodium and chlorine and lowered potassium levels have frequently been found.

Adult↗
PubMed1982

Application of phi (rho z) curves and a windowless detector to the quantitative x-ray microanalysis of frozen-hydrated bulk biological specimens.

Preliminary experiments aimed at establishing the validity of applying phi (rho z) curves to the analysis of elements from carbon to calcium in frozen-hydrated bulk biological specimens are described. Computer generated phi (rho z) curves permit simultaneous absorption and atomic number corrections to be made for quantitative analysis. The results so far obtained, whilst not conclusive, indicate that the method is valid for frozen-hydrated samples. The method allows non-ideal standards of inorganic salts to be used for quantitative light element analysis. Simultaneous oxygen analysis at 15kV with a windowless detector is possible using ice as a standard. With further refinements in spectrum processing, carbon analysis may also be possible using pure carbon as a standard. phi (rho z) curves are used to predict that absorption of x-rays from elements P to Ca will be low and that topographic changes in the specimen surface will have little effect on analyses, particularly with detectors using high take-off angles. Line-scan analyses support this prediction and in addition show that analyses of carbon and oxygen are strongly influenced by topography. The depth resolution of analysis is also predicted by phi (rho z) curves. For elements Na to Ca resolution at 15kV is approximately 2.0 micron and 1.0 micron at 10kV. These predictions are supported by experiments on frozen-hydrated sections. phi (rho z) curve analysis indicates that Na x-rays will be strongly absorbed in a frozen-hydrated specimen. It is shown experimentally that with a windowless detector the practical limit of Na detection in a frozen-hydrated bulk sample is between 10 and 25mM per kg wet wt at 15kV.

Animals↗
PubMed1993

The absence of correlations between a clinical classification and ultrastructural findings in amelogenesis imperfecta.

This study was performed to examine whether a clinical classification of different phenotypes of amelogenesis imperfecta could be discernible at the ultrastructural level. Seventeen primary teeth from 16 children with hypomineralization, hypomaturation, or hypoplastic variants of the disease were collected for histologic studies of the enamel by means of polarized light microscopy, scanning electron microscopy (SEM), and secondary ion mass spectrometry (SIMS). Polarization microscopy showed that the enamel was hypomineralized; in six teeth a wavy configuration of the enamel prisms also appeared. Three histomorphologic main types could be discerned. In 10 of the teeth extensive hypomineralization of the bulk of the enamel was found. One tooth had an unusually thick enamel with only a thin normally mineralized surface layer. SIMS images showed less pronounced signals from Ca2+ and Na+ but with stronger signals from Cl- and CN-, representing the organic component of enamel. The SEM images showed an irregular prism pattern with marked interprismatic areas. Irrespective of the clinical appearance or the hereditary pattern the main findings were hypomineralized enamel with or without wavy bands. Neither of the analytical methods used in this paper distinguishes between the clinical phenotypes of amelogenesis imperfecta.

Amelogenesis Imperfecta↗
PubMed1980

Biomedical microanalysis--putting it to work now in diagnostic pathology.

Based on a review of seven years' experience with microanalysis in human pathology, the emphasis of this keynote paper is that currently available microanalytic instrumentation and methodology are of great use diagnostically. The appropriate diagnostic questions which must be posed for microanalysis center around those seeking the cause of the disease (etiologic diagnosis). The preventive and forensic aspects of etiologic diagnosis are stressed. Pathologists analyse not only tissues but also material samples. The backscattered electron (BSE) image with compositional contrast has been essential in making efficient diagnostic use of microanalysis in the scanning electron microscope (SEM). From the 454 specimens seen in the four years 1976-1979, examples are presented to illustrate several aspects of microanalysis: e.g., documentation of the identity and source of toxic dust in lungs; identification of particulate materials in liver, kidney, salivary glands, lymph nodes, etc.; problems of contamination of specimens; use of high vs low magnification analysis; relative volume of tissue sampled using thick (5 micrometer) vs thin (100nm) sections; time required for analysis; and use of fresh frozen, cryo-sectioned tissue for analysis of soluble materials. For practical diagnostic microanalysis, SEM with BSE and x-ray microanalysis of 5 micrometer thick tissue sections at present seems to be the most efficient procedure.

Electron Probe Microanalysis↗
PubMed2003

In vitro calcium phosphate growth over surface modified PMMA film.

In vitro nucleation of calcium phosphate phase was studied over functionalized polymethyl methacrylate (PMMA) films using Fourier transform infrared spectroscopy, electron spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. PMMA films were prepared by dissolving commercial grade pellets in chloroform and cast into thin sheets. The films were immersed in a methanol solution of sodium hydroxide before treating with 1.5% solution of adenosine triphosphate (ATP) at a pH of 5.2 for 24 h. ATP treated films were then soaked in saturated lime solution for 4 days to initiate formation of calcium phosphate precursor phase over their surface. The above films immersed in simulated body fluid solution (1.5 x SBF) for more than 5 days led to the nucleation of apatitic calcium phosphate phase all over the film surface. The ATP coupled film not subjected to lime treatment did not show calcium phosphate nucleation behaviour upon immersion in SBF solution. The Ca/P ratio of the calcium phosphate phase increase with increase in soaking time in SBF solution.

Calcium Phosphates↗
PubMed1993

Surface analysis of four dental implant systems.

Dental implants obtained from four suppliers were analyzed by electron spectroscopy for chemical analysis and scanning electron microscopy. Three of the implants were delivered in a sterilized condition, while the fourth implant was delivered in a plasma-sprayed condition. The covering oxide layer consisted mainly of TiO2. Divalent and trivalent states of titanium were also detected, showing that TiO and Ti2O3 layers occurred. The thickness of the oxide formed on the plasma-sprayed implant was 3.4 nm. The oxide thicknesses of the sterilized implants were 4.6 +/- 0.4 nm. The surfaces of all samples were covered with organic contaminants. A strong fluorine signal was obtained from one sample, indicating that the supplier etches the implants in hydrofluoric acid. Calcium and zinc were found on the surfaces of all samples from one supplier, while calcium and silicon were found on the surfaces of the implants from another supplier. It is suggested that inorganic contaminants should be avoided because these species can possibly provoke the dissolution of titanium.

Calcium↗
PubMed1994

Heterogeneity in ultrastructure and elemental composition of perinuclear lens retrodots.

PURPOSE: To unravel the cataractogenic process(es) leading to the birefringent lenticular bodies known as perinuclear retrodots. METHODS: Ten human lenses containing biomicroscopically verified perinuclear retrodots were systematically screened and analyzed using scanning electron microscopy and energy dispersive x-ray microanalysis to verify their ultrastructure and elemental composition. RESULTS: Three types of retrodots were distinguished, different in size, ultrastructure, and origin. Two of them contained calcium phosphate, the third probably contained calcium oxalate. All three types were separated from surrounding normal fibers and the crystalline inclusions were sequestered within membrane-lined bodies. CONCLUSIONS: Because of these observations and data found in the literature it is postulated that elevated free calcium is the initiating factor in the formation of retrodots, trapped by either oxalate or phosphate and sequestered in the retrodots. It is suggested that the oxalate is derived from ascorbate because of impaired protection against oxidative stress in the older lens. Phosphoric acid is believed to be released by calcium-induced hydrolysis of membrane phospholipids.

Calcium Oxalate↗
PubMed1995

Structure of artificial enamel lesions after topical applications of high-concentration sodium fluoride solution in vitro.

A three-layer structure, including a columnar layer (CL), a buffer layer, and unaffected intact enamel, was successively formed from the outer to the inner part of artificial enamel lesions (AEL) by topical applications of a high-concentration acidic sodium fluoride solution (10,000 ppm, pH 5.6) in vitro. The AEL was produced in bovine enamel that was decalcified for 5 days in a lactic acid gel system. The morphological observations by using scanning electron microscopy showed that the CL was made of columnar deposits of small globules about 0.5 microns in diameter. It was observed for the first time that small globules filled the demineralized interprismatic regions in the buffer layer. The unaffected intact enamel was protected from further demineralization under the acidic condition. Structure and composition of the CL were investigated by using X-ray diffraction and X-ray photoelectron spectroscopy. In the CL the atomic ratio was Ca:P = 12.6 and Ca:F = 0.75, and the small globules were mainly a mixture of polycrystalline calcium fluoride and hydroxyapatite. For comparison, the sound enamel and the AEL attained by applications of 0 and 100 ppm acidic sodium fluoride solutions (pH 5.6) were also investigated. The formation mechanism of the three-layer structure and the related cariostatic effects are discussed.

Animals↗
PubMed2002

Surface modification of poly (D,L-lactic acid) with chitosan and its effects on the culture of osteoblasts in vitro.

Chitosan is a good biodegradable natural polymer, widely used in biomedical fields. In this study, chitosan was used to modify the surface of poly (D,L-lactic acid) (PDLLA) in order to enhance its cell affinity. The properties of a modified PDLLA surface and control were investigated by contact angle and electron spectroscopy for chemical analysis (ESCA), which indicated the changes in surface energy and chemical structure. Scanning electron microscopy (SEM) observation displayed differences in surface morphology between the chitosan-modified film and the control. These data reflected that PDLLA films could be modified with chitosan and in turn may affect the biocompatibility of the modified films. Therefore, adhesion and growth of osteoblasts on modified PDLLA films as well as control were studied. Cell morphologies on the films were examined by SEM and cell viability was evaluated using an MTT assay; the differentiated cell function was assessed by measuring alkaline phosphatase (ALP) activity. The ALP activity of modified PDLLA films was significantly higher than that found on the control (p < 0.01). The proliferation of osteoblasts on modified films was also found to be higher than that on the control (p < 0.05), suggesting that chitosan could be used to modify PDLLA and then enhance its cell biocompatibility.

Alkaline Phosphatase↗
PubMed2002

Surface analysis of ProFile instruments by scanning electron microscopy and X-ray energy-dispersive spectroscopy: a preliminary study.

AIM: The purpose of this preliminary study was to analyze surface irregularities on ProFile nickel-titanium (NiTi) rotary instruments before use, after sterilization by two different methods and after instrumentation of molar root canals. METHODOLOGY: Five new ProFile NiTi rotary instruments with 0.04 taper, size 20, five instruments with 0.04 taper, size 25 and five with 0.06 taper, size 20 were analyzed by scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS). The instruments were then divided into two groups: three of each taper and size were sterilized in a dry heat sterilizer, whilst two of each taper and size were sterilized in an autoclave. After inspection by the same techniques, the files were used to instrument six molar root canals, and again analyzed by SEM/EDS. RESULTS: Together with the usual machining defects, a variable amount of material containing mainly carbon and sulphur was found on the surface of new instruments. This material was not removed by standard cleaning and sterilization procedures. The use of the files for instrumentation of root canals eliminated a considerable amount of the adhered substance, but deposits rich in calcium and phosphorus accumulated on the remaining impurities. CONCLUSIONS: The adherence of dentine on surface deposits found on new ProFile instruments requires special cleaning, prior to sterilization.

Calcium↗
PubMed1993

Imaging fluid/solid interactions in hydrocarbon reservoir rocks.

The environmental scanning electron microscope (ESEM) has been used to image liquid hydrocarbons in sandstones and oil shales. Additionally, the fluid sensitivity of selected clay minerals in hydrocarbon reservoirs was assessed via three case studies: HCl acid sensitivity of authigenic chlorite in sandstone reservoirs, freshwater sensitivity of authigenic illite/smectite in sandstone reservoirs, and bleach sensitivity of a volcanic reservoir containing abundant secondary chlorite/corrensite. The results showed the suitability of using ESEM for imaging liquid hydrocarbon films in hydrocarbon reservoirs and the importance of simulating in situ fluid-rock interactions for hydrocarbon production programmes. In each case, results of the ESEM studies greatly enhanced prediction of reservoir/borehole reactions and, in some cases, contradicted conventional wisdom regarding the outcome of potential engineering solutions.

Aluminum Silicates↗