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At least 631 records · Page 35Linked to original sources
PubMed1999

Porous bioactive glass matrix in reconstruction of articular osteochondral defects.

BACKGROUND AND AIMS: This study was carried out to investigate the use of porous bioactive glass implants in promotion of articular cartilage and subchondral bone repair in large osteochondral joint defects. MATERIAL AND METHODS: Two conical osteochondral defects (top diameter 3.0-3.2 mm) were drilled into the patellar grooves of the distal femurs in the rabbit. The defects, extending (approximately 6-7 mm) from the surface of the articular cartilage to the subchondral marrow space, were reconstructed with size-matched porous conical implants made of sintered bioactive glass microspheres (microsphere diameter 250-300 microm, structural implant compression strength 20-25 MPa) using press-fit technique. The implant surface was smoothened to the level of the surrounding articular cartilage. One of the two defects in each femur was left empty to heal naturally and to serve as the control. At 8 weeks, the defect healing was analyzed with use of a semiquantitative histological grading system, histomorphometry of subchondral bone repair, back-scattered electron imaging of scanning electron microscopy (BEI-SEM), and a microindentation test for characterization for the stiffness properties of the cartilage repair tissue. RESULTS: The porous structure of the bioactive glass implants, extending from the articular defect of the patellar groove into the posterior cortex of the femur, was extensively filled by new bone. Cartilage repair varied from near-complete healing by hyaline cartilage to incomplete healing predominantly by fibrocartilage or fibrous tissue. There were, however, no statistical differences in the histological scores of repair between the glass-filled and control defects, although the sum of the averages of each category was lowest for the bioactive glass filled defects. The indentation stiffness values of all the defects were also significantly lower than that of normal cartilage on the patellar groove. CONCLUSIONS: Porous textures made by sintering bioactive glass microspheres may expand the opportunities in reconstruction of deep osteochondral defects of weight-bearing joints. The implants act mechanically as a supporting scaffold and facilitate the penetration of stromal bone marrow cells and their chondrogenic and osteogenic differentiation. Ionic properties of the bioactive glasses make the substances highly potential even as delivery systems for adjunct growth factor therapy.

Animals↗
PubMed2001

Inhibition of sperm motility does not affect live-dead separation of bull sperm by glass beads.

AIM: This study was designed to explore factors which influence binding of dead versus live sperm to glass filters. METHODS: Multiple semen collections from bulls were used to explore selective filtration of bull sperm as influenced by nonlethal inhibition of sperm motility with fluoride, killing of sperm by quick-freezing, alteration of the glass surface with silicone, and different intervals of sexual rest between semen collections. RESULTS: A comparison of glass spheres 100, 200 and 390 microm in diameter indicated that 200 microm spheres were optimal for selective filtration. Quantitative separation of live from dead sperm was demonstrated with a correlation between the percentage of motile sperm and retention of sperm by the filter of r = -0.87 (P < 0.05). Up to 0.02 mol/L NaFl did not alter the proportion of sperm retained by the filter despite inhibiting sperm motility during filtration, an inhibition which was reversible. Proportions of live-dead sperm, based upon eosin staining, were unaffected by fluoride. Coating the glass spheres with silicone greatly reduced selective filtration. Dead sperm adherence to glass was reduced and resistance to NaFl inhibition was increased by daily ejaculation versus one-week intervals of sexual rest. CONCLUSION: These studies indicate that the adherence of sperm to glass is primarily due to some form of physico-chemical change accompanying death of the sperm cell independent of active sperm motility. This attraction between the sperm plasma membrane and glass is modified by the age of the ejaculated sperm. This information is useful in evaluating different clinical procedures used for sperm separation.

Animals↗
PubMed2002

[Development of GI-II tinted infiltration glass and determination of its properties].

OBJECTIVE: Glass is the weak phase in the glass-alumina composite, and it plays a key role in determining the physical, mechanical and optical properties. The purpose of this study was to explore the fabrication arts of GI-II tinted infiltration glass and determine its properties. METHODS: The thermal properties of the glass were tested on a TMA2940 thermal analyzer with heating rate of 5 degrees C/min and temperature range of 25-750 degrees C. The bar-shaped specimens were prepared with the size of 25 mm x 5 mm x 2 mm and their flexural strengths and elastic modulus with 3-point bending test were measured. The Vicker's hardness and indentation fracture toughness were also determined. The refractive index and changes of chemical constituents were tested by means of V prismatic refractometer and 2910 DTA analyzer. RESULTS: The results showed that the thermal expansion coefficient, Tg and Tf, refractive index, 3-point bending flexural strength, bending elastic modulus, Vicker's hardness, indentation fracture toughness and density were 6.997 x 10(-6) degrees C-1 (25-500 degrees C), 635 degrees C and 650 degrees C, 1.64 MPa, 96.27 MPa, 31.16 GPa, 5.534 GPa, 1.05 MN.m1/2, and 3.214 g/cm3 respectively. Though certain heat processing conditions did result in micro-crystalline in the glass, it remained stable under routine glass infiltration firing cycles. CONCLUSION: GI-II tinted infiltration glass had favorable physical, mechanical properties and good thermal stability.

Aluminum Oxide↗
PubMed2003

The effect of glass fiber reinforcement on the residual monomer content of two denture base resins.

OBJECTIVE: The amount of residual monomer is one of the principal factors affecting the properties of acrylic resin denture bases. In recent years, glass fibers have been used to strengthen denture base resins. The purpose of this study was to investigate the effect of glass fiber reinforcement on the amount of residual methyl methacrylate released from two different denture base resins (heat cured and autopolymerized). METHOD AND MATERIALS: Continuous unidirectional and woven preimpregnated glass fiber reinforcements (Stick and Stick Net) were used to reinforce heat-curing and autopolymerizing denture base resins. RESULTS: The release of residual methyl methacrylate from heat-cured and autopolymerized test specimens reinforced with glass fibers was significantly higher than that from unreinforced test specimens. Stick Net glass fiber reinforcement resulted in significantly higher residual monomer release than did Stick glass fiber reinforcement. Test specimens made from heat-cured denture polymethyl methacrylate released less residual methyl methacrylate than did specimens made from autopolymerized polymethyl methacrylate. CONCLUSION: Glass fiber reinforcement increases the residual monomer content of denture base resins. The level of residual monomer ranged from 0.11% to 0.37% in heat-cured resin and from 0.18% to 0.46% in autopolymerized denture base resin.

Acrylic Resins↗
PubMed2003

Bond strength of glass-ionomer cements to caries-affected dentin.

PURPOSE: The aim of this study was to assess the tensile bond strength of a resin-modified glass-ionomer cement (a: Fuji II LC) and three traditional glass-ionomer cements (b: Ketac-fil; c: Ketac Molar; d: Fuji IX) to caries-affected dentin. MATERIALS AND METHODS: Forty human permanent molars with occlusal caries in dentin were selected, embedded in polyester resin, and ground until the carious dentin was exposed. Infected dentin was removed with curettes according to the atraumatic restorative technique (ART), and the tooth surface was smoothed with SiC paper. A bonding site, limited to 3 mm in diameter, was treated with polyacrylic acid for 10 s. After surface treatment, an inverted glass-ionomer cone was prepared for each specimen, using a split bisected Teflon matrix. The cones were immediately protected with a thin layer of nail varnish or bonding agent. Specimens were stored in distilled water at 37 degrees C for 24 h, and then bond strength to failure was tested. RESULTS: The mean (SD) bond strengths in MPa were: a: 8.33 (2.35); b: 2.46 (1.60); c: 0.83 (1.18), and d: 1.45 (1.70). The data were analyzed using ANOVA and Tukey statistical tests. Fuji II LC, a resin-modified glass-ionomer cement, showed higher bond strength values and was statistically superior to the other groups, containing traditional glass ionomer cements (p < 0.05). CONCLUSION: Findings showed that the traditional glass-ionomer cements tested in this study had lower mean bond strength values to caries-affected dentin than did the resin-modified glass-ionomer cement.

Acid Etching, Dental↗
PubMed2002

[Na and Mg K-edge XANES study in silicate glasses].

The structural role of Na in Na2-O-SiO2 and Na2O-SiO2-P2O5 glasses was studied using Na K-edge XANES (X-ray near edge structure) spectra. The Na K-edge XANES shows little change with increase in the content of Na2O in Na2O-SiO2 glasses. However, the addition of P into the Na2O-SiO2 system causes dramatic change of the Na K-edge XANES, and the Na K-edge spectra of Na2O-SiO2-P2O5 glasses also change with the increase of P2O5 content. The structural role of Mg in CaMgSi2O6 (Di)--NaAlSi3O8 (Ab) glasses was studied using Mg K-edge XANES spectra. The Mg-O bond distance in these glasses is estimated to be 2.00 +/- 0.04 A. Thus, Mg in these glasses may be five coordinated with oxygen, or Mg may have multiple structural sites, MgIV, MgV and MgVI. The Di-Ab glasses may possess a medium-range ordering structure.

Glass↗
PubMedDate not supplied

[Respiratory function in glass blowers].

The prevalence of chronic and acute respiratory symptoms and diseases and changes in lung function in a group of 80 glass blowers have been investigated. In addition a group of 80 not exposed workers was used as a control group for respiratory symptoms and diseases. In glass blowers, there was significant increase in prevalence of chronic bronchitis, nasal catarrh, and sinusitis than in the controls. Glass blowers exposed for more and less than 10 years had similar prevalences of respiratory symptoms. A large number of glass blowers complained of acute across-shift symptoms. Significant increase in FVC, FEF50 and FEF25 was documented at the end of the work shift. Comparison with predicted normal values showed that glass blowers had FVC and FEF25 significantly lower than predicted. RV and RV/TLC were significantly increased compared with the predicted normal values. DLCO was within the normal values in most glass blowers. It is concluded that work in the glass blower industry is likely to lead the development of chronic respiratory disorders.

Adult↗
PubMed1985

The use of glass as solid phase in enzyme immunoassay as exemplified by the detection of circulating immune complexes.

This article describes a solid-phase enzyme immunoassay for the quantitative determination of circulating immune complexes based on the covalent binding of proteins to glass. A quantitative comparison between adsorption to polystyrene and covalent binding to glass gave a protein higher concentration on the glass support. This leads, in connection with the strong attachment of the protein, to a higher sensitivity and precision in immunoassay. The binding of C1q to glass as solid phase offers the possibility to reuse the protein as well as the glass support after accomplishment of the immunoassay which can reduce the cost of the assay in routine work dramatically. Furthermore, the immobilization of C1q to glass gives an extreme stability of the protein which means that the c1q-coated glass supports can be used up to one year under routine conditions.

Adsorption↗
PubMed1995

Moisture susceptibility of resin-modified glass-ionomer materials.

The purposes of this experiment were to determine if resin-modified glass-ionomer cements are less sensitive to moisture than are conventional glass-ionomer cements, to investigate the effects of barrier coatings, and to study the effects of different setting environments. Discoid specimens of a variety of resin-modified glass-ionomer materials and a conventional glass-ionomer cement control were stored in different environments and were protected with different barrier coatings. The diametral tensile strengths of the specimens were determined and analyzed with three-way analysis of variance. Resin-modified glass-ionomer cements are less sensitive to moisture than is the conventional glass-ionomer cement control. Drier environments produced stronger resin-modified glass-ionomer specimens. Use of a fissure sealant as a barrier coating increased overall specimen strength, and the individual materials differed in strength.

Absorption↗
PubMed1994

Development of bioabsorbable glass fibres.

Calcium-iron phosphate glasses with an iron oxide content ranging from 5 wt.% to 22 wt.% were prepared to investigate the effect of iron oxide on the properties of the glass. It was found that the dissolution rate, the fibre strength and the glass transition temperature were strongly affected by iron oxide. The glass dissolution rate exhibited a 50-fold reduction while the fibre strength doubled when the iron oxide content was increased from 5 wt.% to 22 wt.%. The phosphate glass containing 22 wt.% of iron oxide had a dissolution rate of about 5 micrograms/(cm2 day). The fibres drawn from this glass also exhibited the highest tensile strength over 1000 MPa. A cortical bone plug method was used to assess the biocompatibility of the glasses with the hard and soft tissues. The tissues surrounding the samples showed no inflammation at 9 wk.

Animals↗
PubMedDate not supplied

The effect of various surface coatings on fluoride release from glass-ionomer cement.

To protect glass-ionomer cement from moisture contamination and dehydration during initial setting, immediate application of a surface coating agent is recommended. This study compared the effect of various surface coatings on F release from glass-ionomer cement. Twenty glass-ionomer cement (Ketac Fil Aplicap) disks (4.52 cm2) were prepared from a Teflon mold. The control group was uncoated, while the experimental groups were coated with Visiobond, Scotchbond II, and Ketac Varnish. In addition, five specimens of Variglass were similarly prepared and remained uncoated as per the manufacturer's instructions. F release was measured each day during week 1 and on the last day of weeks 2, 3, and 4. The results indicated that the application of the surface coatings did not completely inhibit F release from glass-ionomer cements, and that F release during the first week for all groups was significantly greater than in the subsequent 3 weeks. Visiobond-coated glass-ionomer cement allowed significantly more F release than Scotchbond II-coated glass-ionomer cement, Ketac Varnish-coated glass-ionomer cement, or Variglass.

Acrylic Resins↗
PubMed1996

An in vitro comparison of micro leakage in three glass ionomer cements used as retrograde filling materials.

The aim of this study was to evaluate the sealing ability of conventional self-cured glass ionomer cement, silver glass ionomer cement and light-cured glass ionomer cement as retrofilling materials. Micro-leakage was assessed by introducing the samples into a 1 per cent solution of methylene blue for eight days at a constant temperature of 37 degrees C. Dye penetration was greater when silver glass ionomer cement was used in comparison to the other two materials tested; the difference was statistically significant. Conversely, the sealing ability of light-cured glass ionomer cement was significantly higher than that of conventional glass ionomer cement. The condition of the dentine-filling material interface and the marginal adaptation of the glass ionomer cements under study were assessed using scanning electron microscopy.

Cermet Cements↗
PubMed1996

Radiopacity of resin-modified glass-ionomer restorative cements.

This in vitro study compared the relative radiopacities of three commercially available resin-modified glass-ionomer cements (Vitremer, Fuji II LC, and Photac-Fil), an experimental resin-modified glass-ionomer (V-66), two conventional glass-ionomers (ChemFil and Fuji Cap II), and amalgam (as the control). Radiopacity was assessed densitometrically and expressed as equivalent thicknesses of aluminum. All the glass-ionomer cements were more radiopaque than enamel and dentin, with the exception of ChemFil and Photac-Fil. Apart from the control material, the experimental resin-modified glass-ionomer material, V-66, had the highest radiopacity of all the materials tested. Of the three resin-modified glass-ionomer materials tested, Fuji II LC was the most radiopaque and Photac-Fil the least. For the radiopacity of restorative glass-ionomer materials to exceed that of enamel, it should be greater than 1.5 mm of equivalent thickness of aluminum.

Absorptiometry, Photon↗
PubMed1996

Marginal leakage of combinations of glass-ionomer and composite resin restorations.

This study compared the microleakage of four different combinations of glass-ionomer and composite resin restorations. Forty class V cavities were prepared in permanent posterior teeth. The gingival margin of the cavities were placed in cementum and the occlusal wall in enamel. The cavities were restored as either 1) light-cured glass-ionomer cement (LC-GIC); 2) chemically cured glass-ionomer cement (CC-GIC); 3) composite resin (with dentin bonding agent); or 4) light-cured glass-ionomer and composite resin (sandwich). Marginal microleakage was assessed by methylene blue dye penetration after thermocycling between 5 degrees C and 60 degrees C for 300 cycles. Microleakage of LC-GIC restorations and the dentin-bonded composite resin restorations were significantly lower than the CC-GIC and the LC-GIC sandwich technique restorations. There was no significant difference in the microleakage between the LC-GIC and the dentin-bonded composite resin restorations. The degree of microleakage of the sandwich restorations was significantly lower than the CC-GIC restorations. Light-cured glass-ionomer and dentin bonded composite resin restorations exhibited a lower degree of leakage than the glass-ionomer/composite sandwich and chemically cured glass-ionomer restorations at the gingival margins of class V restorations.

Analysis of Variance↗
PubMed1976

Glass for parenteral products: a surface view using the scanning electron microscope.

The scanning electron microscope was utilized to explore the internal surface of glass ampuls and vials used in parenteral products. The surface topography of USP Type I borosilicate glass containers was viewed after exposure to "sulfur," ammonium bifluoride, and sulfuric acid treatments. The scanning electron micrographs showed startling differences in the appearance of the surface regions. "Sulfur treatment" of ampuls was associated with a pitting of the surface and the presence of sodium sulfate crystals. The sulfur treatment of vials altered the glass surface in a characteristically different manner. The dissimilarity between the surface appearances was attributed to the method of sulfur treatment. Ampuls exposed to sulfuric acid solutions at room temperature did not show the pitting associated with the sulfur treatment. Scanning electron micrographs of ammonium bifluoride-treated ampuls showed a relief effect, suggesting that the glass was affected by the bifluoride solution but that sufficient stripping of the surface layer did not occur to remove the pits associated with the sulfur treatment. Flakes emanating from the glass were identified with the aid of the electron microprobe. Scanning electron micrographs showed that these vitreous flakes resulted from a delamination of a thin layer of the glass surface. It is concluded that the scanning electron microscope, in conjunction with other analytical techniques, is a valuable tool in assessing the quality of glass used for parenteral products. The techniques studied should be of particular importance to the pharmaceutical industry where efforts are being made to reduce the levels of particulate matter in parenteral dosage forms.

Beryllium↗
PubMed1999

Deposition of Colloidal Zinc Sulfide on Glass Substrate.

The effect of colloidal forces involved in the deposition of spherical zinc sulfide colloidal particles on a packed bed of glass has been studied. Experiments were performed by pumping a suspension of monodisperse colloidal ZnS particles through a cylindrical plug of ground glass, and by continuous determination of the outgoing suspension concentration. The flux density of adhered particles, jexp (number of particles deposited per unit time and unit surface area of glass collector), decreased with both pH and ionic strength of the aqueous electrolyte solution. Qualitative explanation of the experiments has been given in terms of the total energy of interaction between the dispersed particles and the substrate, and between the particles themselves, computed from the extended DLVO theory, including acid-base interactions. The contributions to the total free energy of interaction were determined from the zeta potential and surface free energy of ZnS and glass, measured under different experimental conditions. It was found that at pH 4 (below the isoelectric point of ZnS) the efficiency of the deposition of ZnS on glass was maximum. At higher pH values the amount of ZnS deposited on glass clearly decreased. Increasing NaCl concentration at fixed pH (>/=6) decreased the efficiency of the deposition. Adhesion experiments were also performed at pH 4 in the presence of increasing concentrations of CaCl2 or La(NO3)3 in the dispersion medium. In these cases, the rate of adhesion was qualitatively well correlated with the computed ZnS-glass interactions. Copyright 1999 Academic Press.

Journal Article↗
PubMed1987

High-yield high-performance liquid chromatographic analysis of steroid hormone receptors on glass columns.

The HPLC characteristics of extensively purified chicken oviduct progesterone receptors were compared on TSK 3000 SW size-exclusion and DEAE-5-PW media packed in either glass or stainless-steel columns. Recoveries of [3H]progesterone-labeled receptor from size exclusion were 75-95% in glass columns and less than 10% in stainless-steel columns. Similarly, recoveries from DEAE were greater than 90% in glass columns but only approximately 45% in stainless-steel columns. Recoveries in glass columns were similar on several HPLC systems. Thus, the requisite component for high yields from extensively purified receptor preparations was the glass column itself. While receptor B exhibited ionic strength-dependent mobility similar to several standard proteins on size-exclusion glass column HPLC, receptor A was very peculiar. Resolution of receptors A and B was superior to previous reports using size exclusion open-end chromatography. We also resolved functionally active proteolytic fragments. Finally, the generality of glass column size-exclusion HPLC was demonstrated by high-yield analysis of different steroid hormone receptors from different tissues and species.

Animals↗
PubMed2004

Radiation-blocking glasses allow vision during ophthalmic plaque radiation therapy.

PURPOSE: To evaluate the use of leaded safety glasses to block radiation and allow for vision during ophthalmic plaque radiation therapy. DESIGN: Interventional case series. METHODS: Eight patients were treated with palladium 103 ophthalmic plaque radiotherapy and measured for emitted radiation while wearing leaded glasses or a lead patch. Radiation emission was measured at 1 m so as to compare the glasses' ability to block radiation in vivo. RESULTS: In two patients the tumor was in the patients' only seeing eye, and the leaded radiation safety glasses allowed them to function (feed themselves and walk to the bathroom unassisted). In two additional patients, the glasses allowed binocularity and were preferred over the patch. Measurements revealed that both the lead patch and leaded radiation safety glasses reduced exposure to levels acceptable for discharge to home in New York City. CONCLUSIONS: Leaded radiation safety glasses improved patients' quality of life without sacrificing radiation safety.

Brachytherapy↗