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Two intraocular lenses (IOLs) from the same manufacturer showed surface particles by scanning electron microscopy. With energy-dispersive X-ray analysis, these were shown to contain Mg-Si, Al-Mg-Si, Ti, Fe, Ca and Cu. A sterile chronic intraocular inflammation may result from implantation of such contaminated IOLs.
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Whole enamel scrapings from teeth of embryonic calves have been separated by density gradient centrifugation in organic solvents into fractions (1.6 less than p less than 2.4 g/cm3) representing progressive stages of mineral phase maturation. Single enamel particles or their small aggregates from such fractions were examined by transmission electron microscopy, electron diffraction, and high-spatial-resolution electron probe micro-analysis. The electron optical methods demonstrated the presence of poorly crystalline hydroxyapatite as the only detectable solid phase in all fractions. Octacalcium phosphate and brushite were not identified in the fractions. Changes in electron diffraction patterns were indicative of a progressive increase in apatite crystallinity with enamel maturation. Molar Ca/P ratios were found to range from 1.48 to 1.70, with a higher mean value obtained for lower-density fractions (p less than 2.0 g/cm3). Lower-density fractions contained some particles with high ratios (approximately equal to 2.0-4.0) and a non-uniform distribution of Ca and P, as revealed by electron probe mapping. These characteristics are suggested as possibly being related to carbonate phases in early enamel.
Most Pd-Cu-Ga alloys on the market have a yield strength of the order of 1000 MPa, which is too high for an adequate adjustment of the margins of a crown and may promote wear of an opposing natural tooth. In the present work, the structure of a commercial Pd-10 wt% Cu-9 wt% Ga alloy has been shown by means of TEM to consist of thin (5-25 nm) laths with two ordered fct phases with the composition Pd3GaxCu1-x. The c/a ratios in these fct phases are, alternatingly, greater than 1 and less than 1. The transformation of an fcc structure by short atomic movements into the fct structures occurs rapidly below 500 degrees C, as judged by thermal expansion measurements. Such fct structures are likely to provide substantial resistance to dislocation movement and thus a high yield stress and hardness. By adding 6 wt% Ag to the Pd-Cu-Ga alloy and reducing the Ga and Cu content correspondingly, a predominantly fcc structure occurred with nearly no fct laths. At the same time, the hardness was reduced to approximately half the value for the initial Pd-Cu-Ga alloy.
A combined HCl-collagenase digestion technique and scanning electron microscopy were used to isolate the enamel organ and to confirm the presence of maturation ameloblasts of both ruffle-ended (RA) and smooth-ended (SA) types on maturing enamel in kitten permanent tooth germs. EDTA perfusion of animals fixed with aldehyde produced two or three belt-like shallow grooves (from 30 to 100 micron wide) running horizontally through the maturing enamel surface, coinciding closely with the SA distribution pattern. In animals that had been perfusion-fixed with unbuffered osmium tetroxide containing 2.5% potassium pyroantimonate, SEM-EDX analysis detected K in a superficial enamel layer overlaid by the SA layer. Potassium concentration decreased gradually toward the deeper layers. Very little K penetrated the enamel under the RA layer. Energy-dispersive x-ray analysis of Ca and P concentrations in the enamel revealed an even distribution of these elements throughout the superficial layer of maturing enamel. These results suggest that the SA layer forms an access route for K and EDTA and that, in spite of the obvious morphological and functional differences between RA and SA, the maturing enamel surfaces overlaid by these two cell types show similar degrees of mineralization.
Resin-bonded bridges may replace missing teeth and act as splints in periodontal treatment. The objective of this study was to investigate the etch pattern after electrolytic etching of selected Co-Cr alloys in hydrochloric acid and to assess the changes in alloy composition after different etching times. The alloys investigated were Vitallium, Wironit, Wironium, Nobilium Hard, and Niranium NN. Alloy specimens were electrolytically etched in a hydrochloric acid solution for 1, 2, 5, and 10 min. The etched specimens were examined in a light microscope and a scanning electron microscope (SEM). Different etching patterns were revealed in the various alloys. Microprobe analyses after the etching of Vitallium showed generally that Co was released and that Cr content increased at the surface.
The objective of this study was to investigate whether water storage causes permanent damage to composites by determining how the tensile strength of nine different composite materials changes with both water storage and water storage followed by dehydration. Eighteen samples (ASTM-D Specification 1708-66) of each of the nine materials were prepared and divided into three groups of six samples each. Group I was stored dry at 60 degrees C, while Groups II and III were stored in distilled water at 60 degrees C. After six months, Groups I and II were subjected to tensile testing, while Group III was transferred to a desiccator and dehydrated for two weeks at 60 degrees C before this group was tested in tension. Mean values, pooled by storage group independent of material, revealed a significant (p less than 0.05) reduction in strength for both Groups II and III relative to Group I. These findings prove that water has an irreversible effect on most dental composites. A comparison of Group II with Group III data revealed that the samples which were aged in water and tested (Group II) were significantly (p less than 0.05) weaker than the dehydrated samples (Group III). However, some products within Group III did not show any tendency to recover their strength after dehydration.
The response of ectomesenchymal cells of dog dental pulp to implantation of Millipore filters supplemented with bovine plasma fibronectin was evaluated after observation periods of one or four weeks. Two concentrations of plasma fibronectin were used (0.2 and 1 mg/mL). Experiments also included implants treated with control solutions (PBS or 1 mg/mL of dog albumin). Formation of a layer of elongated, polarized cells was demonstrated in direct contact with the implants treated with 1 mg/mL of plasma fibronectin solution, after one week post-operatively. Microfilamentous organization and orientation of rough endoplasmic reticulum was observed mainly in the supranuclear zone of the polarized cells. Implants treated with the same solution were consistently surrounded by a thick layer of dentinal matrix after four weeks of their exposure to pulp sites. Implants treated with control solutions or with the low concentration of fibronectin never showed any sign of cell polarization and matrix synthesis. These data provide evidence that the pulp cells can express their odontoblastic phenotype in response to a surface containing concentrated fibronectin (even allogenic), without the need of other molecules as exogenous inductive factors.
In an attempt to compare the morphology of the dentin adhesive interface and the wetting and penetration of the adhesive in relation to the dentin surface, we studied four dentin adhesive systems using scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). 2-Hydroxyethylmethacrylate (HEMA), a monomer common to many commercial dentin adhesive systems, was altered to produce a thiolated analogue (HETMA). Sulfur, traceable by EDS and STEM, was substituted for the oxygen atom in the backbone of the HEMA molecule. The resulting analogue, with solubility parameters and other wetting and physical properties very similar to those of HEMA, was applied to four sets of tooth specimens, each pre-treated with a different primer or etchant. Three separate pre-treatments--nitric acid, maleic acid, and citric acid/ferric chloride--created a demineralized zone approximately 1 to 3 microns thick at the dentin surface. The HETMA was found to permeate freely into this zone when either of the latter two pre-treatments was used. However, the band of dentin that was demineralized by the nitric acid pre-treatment appeared impermeable to the HETMA. The fourth pre-treatment, an alcohol-based solution including the phosphorus acid ester PENTA and HEMA, modified the smear layer of the tooth slightly and did not appear to demineralize the dentin. HETMA applied to the specimens pre-treated with PENTA and HEMA was clearly in intimate contact with the dentin or modified smear layer; however, it did not penetrate or diffuse into these areas. It did flow into the dentinal tubules, as was also evident with each of the other systems. It was concluded that the acid pre-treatment of the dentin greatly influenced the wetting behavior of the dentin adhesive and thus could substantially affect the resultant bond strength of the dentin adhesive systems.
The ultimate success of a dentin adhesive bond is dependent in large part on specific conditions at the interface between the tooth and the adhesive. Most current dentin adhesive systems use some sort of pre-treatment to demineralize the first few microns of the dentin surface, leaving a meshwork of collagen into which the adhesive resin can penetrate, infiltrate, and polymerize. The general hypothesis tested in this experiment was that the penetration and distribution of adhesive resin into the demineralized zone are a function of the conditioner used as a pre-treatment for the adhesive application. Four commercially available adhesive systems were modified to incorporate hydroxyethylthiomethacrylate (HETMA), a sulfur-substituted, traceable analogue of 2-hydroxyethylmethacrylate (HEMA), thereby allowing for a qualitative measurement of the amount and distribution of monomer in the treated dentin substrate by energy-dispersive x-ray spectroscopy (EDS) and a quantitative measurement by Auger electron spectroscopy (AES). The dentin pre-treatments investigated were: (1) 10% citric acid/3% ferric chloride, (2) 10% maleic acid, (3) 2.5% nitric acid, and (4) an alcoholic solution of HEMA with a phosphorus acid ester. These pre-treatments were applied to freshly extracted teeth that had been sectioned to expose the dentin and ground to simulate the smeared layer. After the appropriate pre-treatment was applied, a 10% (v/v) solution of HETMA in acetone was applied to the surface, followed by the corresponding adhesive resin, which was then polymerized. The samples were then processed for observation by scanning transmission electron microscopy (STEM), AES, and STEM/EDS analysis. The results indicated significant differences in the ability of HETMA to penetrate the dentin surface conditioned by the four pretreatments investigated here. This study also demonstrated that AES and STEM/EDS could be used in a correlative fashion to determine the distribution of HETMA within or adjacent to the treated dentin surface.
The development of novel mechanical and chemical surface modification treatments to improve the osteointegration properties of osseointegrated dental implants is nowadays a topic of great applicative interest. The aim of the present study was to analyse the role of surface topography and chemistry of four different surface treatments on titanium by an in vitro human osteosarcoma immortalised cell line model (MG63). The surface treatments considered were (a) machined titanium, (b) chemical etched on machined titanium, (c) sandblasted titanium and (d) chemical etching on sandblasted titanium. Chemical and physical surface properties were investigated by Scanning Electron Microscopy, Thin Film-X ray Diffraction and by Laser Profilometry. The in vitro biological response was characterised using the MG63 cell line by elution cytotoxicity tests, cell morphology, adhesion, proliferation activity, alkaline phosphatase activity and total DNA content in order to show a relationship between osteoblast response and surface features. Chemical and physical characterisation showed that the considered treatments differently modify the surface morphology in the micro and sub-micrometric scale. Although some differences in alkaline phosphatase activity were observed in the biological characterisation, depending on the specific material's surface finishing, the results showed that cells were well responsive on all the tested materials and grew and differentiated with similar proliferation rate.
Three-dimensional environments have been shown to enhance cell aggregation and osteoblast differentiation. Thus, we hypothesized that three-dimensional (3D) growth environments would enhance the mineralization rate of human embryonic palatal mesenchymal (HEPM) pre-osteoblasts. The objective of this study was to investigate the potential use of rotary cell culture systems (RCCS) as a means to enhance the osteogenic potential of pre-osteoblast cells. HEPM cells were cultured in a RCCS to create 3D enviroments. Tissue culture plastic (2D) cultures served as our control. 3D environments promoted three-dimensional aggregate formations. Increased calcium and phosphorus deposition was significantly enhanced three- to 18-fold (P < 0.001) in 3D cultures as compared with 2D environments. 3D cultures mineralized in 1 wk as compared with the 2D cultures, which took 4 wks, a decrease in time of nearly 75%. In conclusion, our studies demonstrated that 3D environments enhanced osteoblast cell aggregation and mineralization.
Tracheal endocrine cells (TECs) that contain serotonin have been characterized previously by staining with ferric ferricyanide. In the present article, the ferric ferricyanide staining reaction has been used to locate the TECs in deplasticized thick sections of Epon-embedded rabbit tracheas. Adjacent thin sections of the same cell were subsequently observed by electron microscopy. The TECs were filled with dense-core vesicles (DCVs) located in the cytoplasm between the nucleus and the lumen and also lateral to the nucleus. In a separate experiment, pieces of rabbit trachea were treated with a solution of glutaraldehyde-dichromate to demonstrate the presence of amines. High levels of chromium were detected in the DCVs by energy-dispersive X-ray analysis. The results from these studies have correlated the ultrastructure of a serotonin-containing endocrine cell present in rabbit tracheal epithelium with a cell type previously characterized only by light and fluorescence histochemical methods. The results also indicate that serotonin in these cells is stored in the DCVs.
Details are given of the techniques used in the analysis of asbestiform fibers in the water systems of Duluth, Minnesota and other cities. Photographic electron diffraction and electron microprobe analyses indicated that the concentration of verified amphibole mineral fibers ranged from 20 x 10(6) to 75 x 10(6) fibers/l. Approximately 50-60% of the fibers were in the cummingtonite-grunerite series and 20% were in the actinolite-tremolite series. About 5% were chemically identical with amosite. A wide variety of analytical techniques must be employed for unique identification of the mineral species present in water systems.
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The internalized speciation of lead in roots and leaves of Sesbania drummondii, a lead hyperaccumulator, grown in lead nitrate solution was studied using x-ray absorption near-edge structure and extended x-ray absorption fine structure. Lead was predominantly present as lead acetate in both plant tissues. The other dominant forms of accumulation were lead-sulfur compounds. Whereas lead sulfate and sulfide were found in leaves, only lead sulfide was detected in root samples. These observations indicate that S. drummondii is able to biotransform lead nitrate in the nutrient solution to lead acetate and sulfate in its tissues. Complexation with acetate and sulfate may be a lead detoxification strategy in this plant. Transmission-electron microscopy revealed the pattern of lead distribution in and around the cells. Dense distributions of lead grains were detected in root cell walls and plasma membranes, whereas evidence for vacuolar transport of lead was noticed in the stem cells.
A scanning electron microscope and electron probe study was carried out to compare root structure from deep within periodontal pockets with roots exhibiting no periodontal disease. To eliminate the possibility of extraneous ion introduction or deletion, no attempt was made to subject the roots to fixation, embedding, or dehydration prior to sectioning and viewing in the electron microscope. Mineral content and concentration were determined with an electron probe on two specimens per tooth. On one specimen, only the external cemental surface was analyzed. On an adjacent cross section, readings were taken from the surface and at incremental depths into the root. A nonparametric statistical analysis compared diseased with nondiseased roots. The following conclusions can be drawn from the study: (1) Consistent and repeatable qualitative electron probe analyses can be performed on human teeth with minimal specimen preparation. This gives a more accurate assessment, since the integrity of the crystalline structure is not disrupted. (2) Minerals consistently found were P, Ca, Cu, Zn, Mg and Na. They were in similar concentrations throughout the area analyzed. (3) Mg and Cu showed higher values in the nondiseased teeth. (4) There were no differences in concentrations for Ca, P, Zn, and Na between roots exposed to a periodontal pocket and nondiseased roots.
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