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At least 433 records · Page 24Linked to original sources
PubMed1993

Comparison of the adhesive strength of a BIS-GMA cement to tin-plated and non-tin-plated alloys.

This study compared the tensile bond strengths of two base metal alloys and two noble metal alloys, tin-plated and non-tin-plated, with an adhesive resinous cement. Two tin platers were compared for their effectiveness in enhancing the composite resin-to-metal bond. Cylinders of the alloys were bonded end to end with the adhesive cement, thermocycled for 24 hours, stored in distilled water for 27 days, and tested for tensile bond strength. The mean bond strengths and mode of failure were recorded, and scanning electron micrographs were recorded for subjective evaluation. Significant differences were demonstrated between the non-tin-plated and the tin-plated noble alloys and base metal alloys.

Adhesives↗
PubMed1994

Comparison of shear bond strengths of two resin luting systems for a base and a high noble metal alloy bonded to enamel.

Researchers are investigating the use of noble metals for the fabrication of resin-bonded prostheses because of concerns about health hazards of nickel and beryllium in base metal alloys. Tin-plating has been advocated to improve the bond of resin luting agents to noble metal alloys. Some manufacturers have suggested that tin-plating is unnecessary to bond noble metal alloys to etched enamel with their products. In this study, Rexillium base metal and Olympia noble metal alloy specimens were bonded to extracted human teeth with the use of two resin luting agents (F21 and Panavia OP). One third of the noble metal specimens were tin-plated, one third were oxidized, and one third were oxidized and sandblasted. Each of the bonded specimens were thermocycled and subjected to a shear force until bond failure. The base metal specimens bonded with Panavia OP luting agent exhibited the greatest mean shear bond strengths. The tin-plating surface treatment significantly increased the mean shear bond strengths of Olympia noble metal specimens.

Adhesives↗
PubMed1989

Osteocompatibility of platinum-plated titanium assessed in vitro.

Suppression of dissolution is important to increase the biocompatibility of titanium implants. Therefore, the possibility of application of platinum-coated titanium as a biomaterial was explored in in vitro experiments using the MC3T3-E1 osteogenic cell line. The data obtained from long-term cultures indicated that pure platinum or titanium thickly coated with platinum inhibited calcification significantly, suggesting that the platinum ion fails to improve the osteocompatibility of titanium implants.

Alkaline Phosphatase↗
PubMed1987

Electrocoating carbon fiber microelectrodes with Nafion improves selectivity for electroactive neurotransmitters.

A method which improves carbon fiber microelectrode selectivity for cationic amines by electrocoating the fiber with a thin film of the ionic polymer, Nafion, is described. The selectivity and response speed of these electrodes for the detection of electroactive cationic and anionic species found in brain extracellular fluid was evaluated using differential pulse voltammetry and chronoamperometry and compared to uncoated fibers. Carbon fiber microelectrodes electrocoated with Nafion are highly sensitive to cationic amines such as dopamine and serotonin and have minimal sensitivity to anions such as ascorbic acid and uric acid at physiological concentrations.

Carbon↗
PubMed1990

The micronucleus assay in human exfoliated cells of the nose and mouth: application to occupational exposures to chromic acid and ethylene oxide.

We have applied the micronucleus (MN) assay to exfoliated cells of buccal and nasal cavities to monitor the genotoxic risk in a group of workers exposed to chromic acid and in another group exposed to ethylene oxide (EtO). The first group comprised 16 subjects working in a 'hard' type chrome-plating factory showing increased chromium absorption and chromium-induced rhinopathy. The second group comprised 9 subjects working in a sterilization unit, exposed to EtO concentrations lower than 0.38 ppm as timed weighted average (TWA) for a working shift; 3 of them were involved in a acute exposure too. The frequency of MN in buccal mucosa was within the norm for exposure both to chromium and to EtO. The MN frequency in nasal mucosa was not altered in chromium platers, whereas a significant increase (p less than 0.01) in MN was found in 2 out of 3 subjects involved in the accidental EtO leakage and a non-significant increase in MN was found in the group chronically exposed to EtO.

Adult↗
PubMed1991

Tin oxide coating of aluminous porcelain by reactive ion plating.

Alumina reinforced dental porcelain has been coated directly with tin oxide by reactive ion plating. Samples were prepared at different distances from the tin source in the ion plating rig. Tensile bond strengths of treated and untreated porcelain discs to a commercially available phosphate-methacrylate based dental cement were determined. Bond strengths of certain coated samples were found to be in excess of the cohesive strength of the porcelain substrates (greater than 7.8 MPa), whereas untreated porcelain achieved an average bond strength of only 3.4 MPa. The microstructures of coatings produced under conditions similar to those which yielded the maximum bond strength were examined in a scanning electron microscope and were found to be approximately 0.5 microns thick. It is believed that ion plating has great potential for rendering inert ceramic surfaces capable of direct bonding to dental cements.

Adhesives↗
PubMed1993

A SEM study of denture plaque and oral mucosa of denture-related stomatitis.

The aim of this study was to compare the morphology of denture plaque and adjacent palatal mucosa in five subjects with denture-related stomatitis and a control group of five healthy subjects. Scanning electron microscope examination of copper plate replicas, which preliminary studies established were superior to epoxy resin replicas, showed that there were no consistent differences between the morphology of denture plaque and adjacent mucosa in the denture-related stomatitis group and control group. In each, the surface of the denture plaque was composed predominantly of coccoid- and rod-shaped bacteria with only some yeast cells. The mucosa was largely devoid of microorganisms and individual epithelial cells were shedding from its surface.

Bacteria↗
PubMed1993

Copper plate replica SEM of developing dental plaque in monkeys (Macaca fascicularis).

The aim of the study was to examine the development of dental plaque in macaque monkeys (Macaca fascicularis). Copper plate replicas were constructed from impressions of the labial surface of one of the upper central incisor teeth after tooth cleaning and when plaque had accumulated for 12, 24 and 48 h in each of five animals. Scanning electron microscope examination of the replicas showed that bacteria were present on the tooth surface as scattered individual cells, which after 24 h had formed a continuous layer. Both coccoid and filamentous bacteria were visible in 48-hour-old plaque. Such a rapid accumulation of potentially periodontopathic dental plaque emphasizes the importance of regular and meticulous oral hygiene.

Animals↗
PubMed1986

Production of no-carrier added 67Cu.

Copper-67 has been produced at the BLIP by 68Zn(p, 2p) and 70Zn(p, alpha) reactions with 193 MeV protons and at the HFBR using the 67Zn(n, p) route. The effective cross-sections of natZn(p, 2pxn)61,64,67Cu reactions were measured at 200 MeV and compared with predicted values obtained from semi-empirical formulae given by Silberberg and Tsao. From these cross-sections, the fraction of 64Cu in the final 67Cu preparations was estimated and compared with the experimental values. A procedure has been developed consisting of electrodeposition and ion-exchange for isolation of no-carrier-added radiocopper from a Zn target. The method is adaptable for remote hot cell operation. The overall radiochemical yield of 67Cu and the separation factors from a Zn target and other radionuclides were evaluated. The saturation yield of 67Cu produced by the fast neutron 67Zn(n, p) reaction and the corresponding cross-section were remeasured. Experiments have been initiated to attach 67Cu to monoclonal antibodies for immunotherapy applications.

Antibodies, Monoclonal↗
PubMed2004

A glucose biosensor based on chitosan-glucose oxidase-gold nanoparticles biocomposite formed by one-step electrodeposition.

An amperometric biosensor for the quantitative measurement of glucose is reported. The biosensor is based on a biocomposite that is homogeneous and easily prepared. This biocomposite is made of chitosan hydrogel, glucose oxidase, and gold nanoparticles by a direct and facile electrochemical deposition method under enzyme-friendly conditions. The resulting biocomposite provided a shelter for the enzyme to retain its bioactivity at considerably extreme conditions, and the decorated gold nanoparticles in the biocomposite offer excellent affinity to enzyme. The biosensor exhibited a rapid response (within 7s) and a linear calibration range from 5.0 microM to 2.4 mM with a detection limit of 2.7 microM for the detection of glucose. The combination of gold nanoparticles affinity and the promising feature of the biocomposite with the onestep nonmanual technique favor the sensitive determination of glucose with improved analytical capabilities.

Biocompatible Materials↗
PubMed2005

Interfacing myoglobin to graphite electrode with an electrodeposited nanoporous ZnO film.

A biocompatible, nanoporous ZnO film was prepared on graphite electrode by the simple electrodeposition method. Based on the film's strong adsorption ability and friendly microenvironment, it can be used as a good matrix to immobilize myoglobin (Mb) through simple adsorption. Moreover, the entrapped Mb realized direct electron transfer with the electrode and displayed an elegant catalytic activity toward the reduction of hydrogen peroxide, nitrite, and trichloroacetic acid, by which the mediator-free biosensors could be fabricated. Atomic force microscopy, UV-Vis spectra, electrochemical impedance spectroscopy, and cyclic voltammetry, etc. were used to characterize the nanoporous ZnO film and Mb-modified ZnO film. Compared to other methods, electrodeposition of porous material supplied a more simple and convenient approach to prepare biocompatible materials for biosensors.

Adsorption↗
PubMed2006

Preparation and activity measurement of electrodeposited alpha-emitting sources.

Alpha-emitting 238Pu and 241Am sources on stainless steel substrates have been prepared using a new electrodeposition method based on an ammonium oxalate-ammonium sulfate electrolyte containing diethyl triamino pentaacetic acid. The deposition yield is determined by measuring the activity of the sources using a high-efficiency 2pi alpha proportional counter and a backscattering chamber designed and fabricated for this purpose. Optimal electrodeposition parameters have been determined for 241Am, enabling manufacture of standard alpha-emitting sources with minimal radioactive waste.

Alpha Particles↗
PubMed2006

Determination of 210Po in environmental materials: a review of analytical methodology.

Polonium-210 ((210)Po) is analysed for a variety of purposes, including for radiological impact assessment, as a tracer of environmental processes, and as an indirect measure of its progenitor lead-210 ((210)Pb). Losses of polonium may occur at temperatures above 100 degrees C, depending on conditions, requiring particular care in sample preparation and treatment. In spite of this problem, the analysis of (210)Po is relatively straightforward, due to the ease of source preparation through spontaneous auto-deposition onto metal surfaces and the uncomplicated alpha spectrum. Although several optimisation studies have been carried out, published source preparation methods remain remarkably diverse. Some areas where further study would be useful are identified.

Air Pollutants, Radioactive↗
PubMed2006

Parallel synthesis of libraries of anodic and cathodic functionalized electrodeposition paints as immobilization matrix for amperometric biosensors.

The integration of flexible anchoring groups bearing imidazolyl or pyridyl substituents into the structure of electrodeposition paints (EDP) is the basis for the parallel synthesis of a library containing 107 members of different cathodic and anodic EDPs with a high variation in polymer properties. The obtained EDPs were used as immobilization matrix for biosensor fabrication using glucose oxidase as a model enzyme. Amperometric glucose sensors based on the different EDPs showed a wide variation in their sensor characteristics with respect to the apparent Michaelis-Menten constant (KM(app)) representing the linear measuring range and the maximum current (Imax(app)). Based on these results first assumptions concerning the impact of different side chains in the EDP on the expected biosensor properties could be obtained allowing for an improved rational optimization of EDPs used as immobilization matrix in amperometric biosensors.

Biosensing Techniques↗
PubMed2004

Effects of topography and composition of titanium surface oxides on osteoblast responses.

To investigate the roles of composition and characteristics of titanium surface oxides in cellular behaviour of osteoblasts, the surface oxides of titanium were modified in composition and topography by anodic oxidation in two kinds of electrolytes, (a) 0.2 M H(3)PO(4), and (b) 0.03 M calcium glycerophosphate (Ca-GP) and 0.15 M calcium acetate (CA), respectively. Phosphorus (P: ca.10at%) or both calcium (Ca: 1-6at%) and phosphorus (P: 3-6at%) were incorporated into the anodized surfaces in the form of phosphate and calcium phosphate. Surface roughness was slightly decreased or enhanced (R(a) in the range of 0.1-0.5 microm) on the anodized surfaces. The geometry of the micro-pores in the anodized surfaces varied with diameters up to 0.5 microm in 0.2 M H(3)PO(4) and to 2 microm in 0.03 M Ca-GP and 0.15 M CA, depending on voltages and electrolyte. Contact angles of all the anodic oxides were in the range of 60-90 degrees. Cell culture experiments demonstrated absence of cytotoxicity and an increase of osteoblast adhesion and proliferation by the anodic oxides. Cells on the surfaces with micro-pores showed an irregular and polygonal growth and more lamellipodia, while osteoblasts on the titanium surface used as a control or on anodic oxides formed at low voltages showed many thick stress fibres and intense focal contacts. Alkaline phosphatase (ALP) activity of the cells did not show any correlation with surface characteristics of anodic oxides.

Biocompatible Materials↗
PubMed2005

Bioactivity of titanium following sodium plasma immersion ion implantation and deposition.

Bio-activation of titanium surface by Na plasma immersion ion implantation and deposition (PIII and D) is illustrated by precipitation of calcium phosphate and cell culture. The bioactivity of the plasma-implanted titanium is compared to that of the untreated, Na beam-line implanted and NaOH-treated titanium samples. Our data show that the samples can be classified into two groups: non-bioactive (untreated titanium and beam-line Na implanted titanium) and bioactive (Na-PIII and D and NaOH-treated titanium). None of the four types of surfaces exhibited major cell toxicity as determined by lactate dehydrogenase (LDH) release. However, the LDH release was higher on the more bioactive PIII and NaOH-treated surfaces. From a morphological point of view, cell adherence on the NaOH-treated titanium is the best. On the other hand, the cell activity and protein production were higher on the non-bioactive surfaces. The high alkaline phosphatase activity per cell suggests that the active surfaces support an osteogenic differentiation of the bone marrow cells at the expense of lower proliferation. The use of Na-PIII and D provides an environmentally cleaner technology to improve the bioactivity of Ti compared to conventional wet chemical processes. The technique is also particularly useful for the uniform and conforming treatment of medical implants that typically possess an irregular shape and are difficult to treat by conventional ion beam techniques.

Animals↗
PubMed2006

Bioactivity and cytocompatibility of zirconia (ZrO(2)) films fabricated by cathodic arc deposition.

Zirconium oxide thin films were fabricated on silicon wafers using a filtered cathodic arc system in concert with oxygen plasma. The structure and phase composition of the zirconium oxide thin films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). The bioactivity was assessed by investigating the formation of apatite on the film surface after soaking in simulated body fluids. Bone marrow mesenchymal stem cells (BMMSC) were used to further evaluate the cytocompatibility of the materials. The results indicate that the films are composed of stoichiometric ZrO(2) and the composition is quite uniform throughout the thickness. Bone-like apatite can be formed on the surface of the ZrO(2) thin film in our SBF immersion experiments, suggesting that the surface is bioactive. The outermost layer of the ZrO(2) thin film comprises nano-sized particles that can be identified by AFM images taken on the thin film surface and TEM micrographs obtained from the interface between the ZrO(2) thin film and apatite layer. The nanostructured surface is believed to be the key factor that apatite is induced to precipitate on the surface. Bone marrow mesenchymal stem cells are observed to grow and proliferate in good states on the film surface. Our results show that ZrO(2) thin films fabricated by cathodic arc deposition exhibit favorable bioactivity and cytocompatibility.

Animals↗
PubMed2006

Electrodeposition of anchored polypyrrole film on microelectrodes and stimulation of cultured cardiac myocytes.

The electrically conducting polymer polypyrrole (PPy) was electrochemically deposited onto Pt microelectrodes on a polyimide (PI) substrate. Pre-modification of the PI surface with a self-assembled monolayer of octadecyltrichlorosilane-induced anisotropic lateral growth of PPy along the PI surface and enhanced adhesive strength of the PPy film. The lateral growth of PPy film around the electrode anchored the whole film to the substrate. External stimulation of cultured cardiac myocytes was carried out using the PPy-coated microelectrode. The myocytes on the microelectrode substrate were electrically conjugated to form a sheet, and showed synchronized beating upon stimulation. The threshold charge for effective stimulation of a 0.8 cm(2) sheet of myocytes was around 0.2 microC, roughly corresponding to a membrane depolarization of 250 mV.

Animals↗