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PubMed2006

Regional bond strengths of a dual-cure resin core material to translucent quartz fiber post.

PURPOSE: To evaluate the microtensile bond strength (muTBS) of a dual-cure resin core material to different regions of translucent quartz fiber post in a post cavity using different surface treatments. METHODS: 30 translucent quartz fiber posts (Light-Post) were used and divided into six groups according to the surface treatments: (1) no surface treatment (Control); (2) photo-cure bonding agent, Clearfil Liner Bond 2V Bond A (PLB); (3) dual-cure bonding agent, Clearfil Liner Bond 2V Bond A+B (DLB); (4) BdA+B followed by light-cured for 20 seconds (DLB & LC); (5) silane coupling bonding agent, Clearfil Photobond with Porcelain Bond Activator (PB+PBA); (6) PB+PBA followed by light-cure for 20 seconds (PB+PBA&LC). Treated post were cemented into artificial post cavities using a dual-cure composite core material (Clearfil DC Core) and light-cured for 60 seconds from the top of the cavity. After 24-hour storage in water, each specimen was serially sliced into twelve 0.6 x 0.6 mm-thick beams for the muTBS test. The data were divided into three regions (upper/middle/bottom) and analyzed using two-way ANOVA and Dunnet's T3 multiple comparisons (alpha = 0.05). RESULTS: The highest bond strength was present in the silane coupling bonding agent group for all regions (P < 0.05). Application of the bonding agent to the post surface significantly improved the bond strength compared with control (P < 0.05). There were no significant differences in muTBS at all regions between the photo and dual-cure type bonding agents (P < 0.05). The bond strength significantly decreased at the bottom region when the post surface was treated with bonding agents (P < 0.05), whereas no regional differences in bond strength were found in the silane coupling bonding agent group (P > 0.05).

Composite Resins↗
PubMed2006

Translucent quartz-fiber post luted in vivo with self-curing composite cement: case report and microscopic examination at a two-year clinical follow-up.

A maxillary central incisor with mild periodontitis and extensive loss of coronal tooth structure was endodontically treated and restored with a translucent quartz-fiber post and a composite core. Treatment was completed with the cementation of full-ceramic crowns on teeth 11 and 21. Informed consent was obtained from the patient. Due to the extent of the periodontal disease, tooth 11 was extracted two years later. With the patient's consent, the tooth was used for research. The tooth was sectioned at 11 levels perpendicularly to the long axis and investigated by means of optical microscopy and scanning electron microscope (SEM). The visual examination showed perfect adhesion between the various interfaces (restoration-dentin-post) at both the coronal and root levels. The adhesion between the post and dentin appeared to be free of gaps, and even where the composite cement showed a nonhomogeneous thickness, voids were not apparent. The tooth under examination allowed the authors to check the effectiveness of the adhesion and the integrity of the hybrid layer after exposure to the oral cavity for two years. The results of this investigation show that there were no gaps between the adhesive resin and dentin and no hydrolysis of the adhesive bond. This case suggests that it is possible to obtain good results in the short term from the cementation of quartz-fiber posts with composite resin cements.

Cementation↗
PubMed1975

The effect of quartz and other non-coal dusts in coalworkers' pneumoconiosis. Part II. Lung autopsy study.

Preliminary pathological and mineralogical studies are reported on seventy-four sets of lungs from British coal miners who have been employed at the collieries included in the National Coal Boards's Pneumoconiosis Field Research. The degree of lung damage was considered in relation to the lung dust content and to the known dust exposures of the men concerned. Lungs were classified as having soft macules, fibrotic nodules or PMF. Those with soft macules had the lowest dust content but there was no significant difference between the dust contents of the lungs with fibrotic lesions and those with PMF. The percentage of non-coal minerals in the lung dust appeared to increase with the pathological classification from soft macules to PMF, and comparisons with the exposure data indicated a preferential retention of non-coal minerals, and especially of quartz, in the cases with the more severe lesions. Histological examination of the lesions showed the packing of dust was less close and the cellular response more vigorous with the lungs with the highest quartz content.

Aged↗
PubMed1990

[Antinuclear antibodies as early diagnostic criteria of developing collagen disease in quartz dust exposure--a case report].

One and a half years antinuclear autoantibodies (ANA) against Scl-70 and U1-RNP were found in the serum of a quartz dust exposed worker before the clinical manifestation of the progressive systemic sclerosis (PSS). Only a discrete lung fibrosis and an enlargement of the heart was seen at the time of the first autoantibody detection. Because workers with an intensive and long-lasting quartz dust exposition take a high risk to develop PSS a sensitive ANA-screening is indicated at minimum suspicion of chronic collagen disease. The detection of a high ANA-titer in a clinical healthy person may give a hint for the possible future development of such a disease and requires the observation of the clinical course and the paraclinical and immunological parameters. A lung fibrosis and/or an enlargement of the heart in X-ray photographs would indicate visceral early manifestations of the PSS before skin symptoms appear.

Antibodies, Antinuclear↗
PubMed1990

[Correlations of quartz dust exposure, scleroderma and lung function].

There are closed relations between progressive systemic sclerosis (PSS) and exposure to quartz dust in the GDR. The recognition of PSS as an occupational disease is regulated by law. By analysis of the dust exposed working places a limit for silica concentrations were fixed. It is unlikely, that silica concentrations below 10% in the respirable dust induce a PSS. There are no significant differences in lung function of PSS-patients with and without quartz exposure.

Adult↗
PubMed1989

Comparative study of the effect of chrysotile, quartz and rutile on the release of lymphocyte-activating factor (interleukin 1) by murine peritoneal macrophages in vitro.

The release of lymphocyte-activating factor (LAF) into the medium of cultured mouse resident peritoneal macrophages was estimated from the effect of this medium on the proliferation of mouse thymocytes in the presence of phytohaemagglutinin. Untriggered macrophages released little LAF into their culture medium. Upon addition of UICC chrysotile A (25-50 micrograms/10(6) macrophages), LAF appeared in the medium, and release continued for at least 20 h. DQ12 quartz was a more potent inducer of LAF production, while rutile was nearly inactive. Although chrysotile and quartz caused cell damage (as estimated by the release of lactate dehydrogenase), it was established that LAF release was not attributable to leakage of preformed intracellular LAF. The lymphoproliferative activity detected in macrophage media was stable at 56 degrees C and nondialysable, which corresponds to the properties of interleukin 1. These biochemical observations are consistent with the non-specific stimulation of the immune system found in asbestotic and silicotic patients.

Animals↗
PubMed1987

[Nature and hygienic importance of industrial dust from the high-temperature processing of quartz].

The study aims at assessing, according to the physiochemical indices for silicosogenicity of the dusts, the risk of industrial aerosols of condensed SiO2, entailing the production of quartz glass in plant "Lenin" - Sliven and of ferrosilicon in plant "Kremikovci". The evaluation is done according to the present norms for quartz in this country (State Gazette No. 61/1977), accepted temporary on the basis of foreign experiment and as norms for condensed SiO2. The quantitative determination of free SiO2 in dusts is performed after infrared spectrophotometric method. In most of the studied processes on both working places pollution above the norm is registered with total and fine dust and condensed SiO2. In order to specify the silicogenicity of the respective dusts a study is to be carried out according to biological indices.

Aerosols↗
PubMed1988

Generation of free oxygen radicals from human polymorphonuclear granulocytes by cytokines from human mononuclear cells, treated with quartz dust DQ12 or coal mine dust TF-1--new aspects in pathogenesis of pneumoconiosis.

We report about the release of a soluble mediator(s) from cultured human monocytes/macrophages after exposure to quartz dust DQ12 or coal mine dust TF-1. This mediator(s) activates isolated human polymorphonuclear granulocytes (PMN) to generation of free oxygen radicals. The strong and long-lasting production of reactive oxygen species (ROS), especially of superoxide anion, was measured as lucigenin dependent chemiluminescence (CL). Studies of mediator exposed PMN with the NBT-test (nitroblue-tetrazolium test) also demonstrated the strong activation of PMN. Electromicroscopical studies of mediator exposed PMN showed strong chemotactic changes in a time dependent manner and suggested the release of lysosomal products. According to these properties we called the mediator(s) "granulocyte activating mediator(s)" (GRAM). Biochemical characterisation indicated a protein nature of GRAM. High pressure liquid chromatography (HPLC) gel-filtration suggested that two molecules or two fragments of one molecule with a m.w. of about 20 kda and just below 10 kda resp. were responsible for the observed effects. PMN are potent inflammatory cells, which are known to immigrate in the lung tissue, especially in the early phases of silicosis. ROS released by activated PMN can act tissue destroying, mutagenic and are probably involved in collagene synthesis by regulation of activity of prolylhydroxylase. Mediator induced release of ROS seems to be an important event in development of lung fibrosis and presents a new mechanism of quartz dust and coal mine dust fibrogenicity.

Biological Factors↗
PubMed1984

Early cellular and biochemical alveolar responses following intra-tracheal inoculation with low dose of asbestos and quartz.

The study of broncho-alveolar lavage harvested from rats intratracheally dusted with chrysotile (0.5 mg), leached chrysotile (0.5 mg), crocidolite (0.5 mg) and quartz (0.5 and 5 mg) indicated: 1. A cytotoxic lysis of alveolar macrophages in relation to phagocytosis of dust particles in the following decreasing order: quartz, crocidolite, chrysotile. 2. Regarding cell intensity and duration while asbestos, even leached chrysotile, gave merely an early and transient response. This cell recruitment concerned mostly PMN leukocytes and at a less extent alveolar macrophage. 3. Cell recruitment was associated with an increased protein and phospholipids alveolar content. The increase of proteins came probably mostly from an inflammatory serum exudation. However, an increase synthesis of complement C3 and phospholipids is not excluded.

Animals↗
PubMed1981

Evaluation of quartz crystals in rat lungs by X-ray diffractometry.

The NIOSH (National Institute of Occupational Safety and Health)-recommended procedure of determining quartz through X-ray diffractometry was applied to rat lungs. Using a compressed air nebulizer inside a closed chamber, 150 male Sprague-Dawley rats were exposed to monodisperse particles of quartz for varying time intervals. The rats were subsequently sacrifice by cervical dislocation and their lungs were removed for ashing inside a muffle furnace at 600 degrees C for 4 hr. The ashed materials were then filtered onto silver membranes and scanned by an /-ray diffractometer. The results, expressed in MG SiO2 were compared to standard values derived from PVC filters. The values suggested that the NIOSH method could be used by biochemists to quantify minerals and crystalline structures in organic materials.

Animals↗
PubMed1982

Experimental silicosis. I. Acute effects of intratracheally instilled quartz on collagen metabolism and morphologic characteristics of rat lungs.

Rats were intratracheally instilled with 50 mg of silica as quartz (0.5-mu particles) at day 0. One and 2 weeks later, lungs were evaluated histologically and by a variety of biochemical measurements. Protein, proline, and hydroxyproline content (as an index of total lung collagen) were quantitated, as were the lung collagen synthesis rate and the total lung protein biosynthesis rate (evaluated with lung minces in vitro). The ratio of newly synthesized Type I/Type III collagen was determined, as was the same ratio for total lung collagen. These experiments were performed in parallel on chronic respiratory disease-free rats and in a strain of conventional animals. The authors conclude that 1) changes in lung structure and composition can be appreciated as early as 1 week, the earliest time point studied, after intratracheal instillation of 50 mg of quartz; 2) observed morphologic changes during the first 2 weeks are consistent with biochemical changes; 3) there are essentially no differences in the response of chronic respiratory disease-free Sprague-Dawley and conventional Wistar rats to intratracheally instilled silica. Both strains of rats developed silica-containing granulomas, which ultimately developed into silicotic nodules, as well as areas of alveolar lipoproteinosis associated with interstitial pneumonitis.

Animals↗
PubMed1996

Effect of bulk insertion, prepolymerized resin composite balls, and beta-quartz inserts on microleakage of Class V resin composite restorations.

Polymerization shrinkage of resin composite at the margin can seriously decrease the longevity of the restoration. Three direct restorative techniques were evaluated for their effects on microleakage. Sixty Class V cavities were prepared in extracted human maxillary molar teeth. The cavities were restored with resin composite placed in one bulk increment, resin composite and a beta-quartz insert, or resin composite and a prepolymerized resin composite ball insert. After they were thermocycled and placed in 0.5% basic fuchsin for 24 hours, the specimens were sectioned and examined for microleakage. The restorations with a prepolymerized ball of resin composite exhibited significantly more microleakage than did restorations with a beta-quartz insert or restorations inserted in bulk.

Ceramics↗
PubMed1995

RF electric field mapping in MR coils with a quartz crystal.

The electric field strength and distribution in MRI/MRS probes was assessed with a quartz crystal whose resonance frequency coincided with the probe frequency. A quartz crystal was used as the sensor because: (i) it was capable of producing a resonance signal when it was excited with a pulsed RF electric field; and (ii) the resonance signal was proportional to the square of the electric field strength (or RF excitation power). The sensor was placed in the vicinity of the MR coil under evaluation and was excited with a short RF pulse applied to the coil and, immediately after the pulse, the resonance signal induced was picked up by the same coil acting as a receiver coil. Intensities of the signals were used to assess the distribution of RF electric fields in the coil. This device is useful for probe design, particularly in the minimization of dielectric losses, which have been attributed to the presence of electric fields in MR coils.

Magnetic Resonance Imaging↗
PubMed2000

Determination of the binding parameters of drug to protein by equilibrium dialysis/piezoelectric quartz crystal sensor.

A novel method, equilibrium dialysis/piezoelectric quartz crystal sensor, applied to determine the binding parameters of diethyldithiocarbamate to human plasma protein is proposed. Based on the investigation of the equilibrium reaction for the binding of drug to protein, the related theoretical equations for this binding were derived. By monitoring the frequency responses of a copper-plated piezoelectric quartz crystal sensor to drug in and out of a dialysis membrane after equilibrium, the binding parameters were determined, i.e., 0.375 micromol g(-1) for beta(p), 6.496 microM for K(dp), 141.99 L mmol(-1) for K(p), and 0.043 for N. These values were in good agreement with reference values. It was found that this method may have application for studying the characteristics of the interaction between other drugs and proteins.

Biosensing Techniques↗
PubMed1998

Coagulation of Quartz Particles in Aqueous Solutions of Copper(II).

The colloidal stability of quartz suspension was determined over a wide range of pH in aqueous copper nitrate where the state of Cu(II) is changed from mainly aqua ions and monohydroxyl complexes in the acid and neutral pH to polynuclear hydroxo complexes and colloidal precipitated copper hydroxide at higher pH. Two regions of instability were observed and in both cases the particles were shown to have low electrophoretic mobility. In the neutral pH region, the uptake of Cu(II) was sufficient to reduce the mobility of the particles to zero, while in the high-pH region evidence suggested coagulation between precipitated Cu(OH)2 and the quartz particles. It was shown that in all cases the coagulation was reversible and that the uptake of Cu(II) was dependent on the uncharged surface hydroxyl density. Studies of the coagulation kinetics showed that extended time scales were involved (several minutes in the neutral pH region to tens of minutes at high pH). Copyright 1998 Academic Press.

Journal Article↗
PubMed1999

Aqueous Wetting Films on Fused Quartz.

Using an image analyzing interferometer, IAI, the interfacial characteristics of an isothermal constrained vapor bubble, CVB, in a quartz cuvette were studied as a precursor to heat transfer research. The effects of pH and electrolyte concentration on the meniscus properties (curvature and adsorbed film thickness) and the stability of the aqueous wetting films were evaluated. The surface potential in the electric double layer was a function of the cleaning and hydroxylation of the quartz surface. The disjoining pressure isotherm for pure water was very close to that predicted by the Langmuir equation. For aqueous solutions of moderate electrolyte concentration, the Gouy-Chapman theory provided a good representation of the electrostatic effects in the film. The effect of temperature on the film properties of aqueous solutions and pure water was also evaluated: The meniscus curvature decreased with increasing temperature, while Marangoni effects, intermolecular forces, and local evaporation and condensation enhanced waves on the adsorbed film layer. Pure water wetting films were mechanically metastable, breaking into droplets and very thin films (less than 10 nm) after a few hours. Aqueous wetting films with pH 12.4 proved to be stable during a test of several months, even when subjected to temperature and mechanical perturbations. The mechanical stability of wetting films can explain the reported differences between the critical heat fluxes of pure water and aqueous solutions. The IAI-CVB technique is a simple and versatile experimental technique for studying the characteristics of interfacial systems. Copyright 1999 Academic Press.

Journal Article↗
PubMed2000

CD Spectroscopy of Proteins Adsorbed at Flat Hydrophilic Quartz and Hydrophobic Teflon Surfaces.

Spectroscopic methods provide a powerful tool for studying the properties of proteins at interfaces. The protein accumulated in one adsorbed layer is frequently less than the minimum mass of protein required by a detection method. In such a case (as is the case in circular dichroism spectroscopy) the sorbent material is usually supplied as dispersion. However, light scattering by the dispersed particles often interferes with the measurement of the circular dichroism of the protein. Therefore, there is a strong need for an experimental setup that enables these measurements to be made using flat surfaces. An example of such a setup is the multiplate quartz cell presented here. The potential of this multiplate quartz cell is shown by some preliminary circular dichroism measurements of IgG adsorbed on different types of surfaces. Copyright 2000 Academic Press.

Journal Article↗
PubMed2002

A quartz crystal microbalance study of the adsorption of asphaltenes and resins onto a hydrophilic surface.

The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quartz crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures.

Journal Article↗