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At least 1,135 records · Page 63Linked to original sources
PubMed1995

Effect of glass ionomer manipulation on early fluoride release.

PURPOSE: To determine the amount of fluoride released from several glass ionomer products [Fuji Cap II, Fuji Ionomer Type II, Ketac-Silver, Chelon-Silver, and Miracle Mix (hand-mixed and encapsulated)], and to compare them between triturated (5, 10, 15 seconds) encapsulated and hand-mixed glass ionomers. MATERIALS AND METHODS: The amount of fluoride released at 1, 2, 3, 7, 14, 21 and 28 days after the start of immersion in deionized-distilled water at 37 degrees C was determined with a fluoride ion selective electrode. Rates of fluoride release and cumulative amounts of fluoride release were calculated. RESULTS: Each glass ionomer released the greatest amount of fluoride during the first 24-hour period. Although there was some variation between products, generally the hand-mixed specimens released significantly (P < 0.05) less fluoride than those prepared by mechanical trituration (10 and 15 seconds). The cumulative amounts of fluoride released from the mechanically triturated glass ionomers were significantly (P < 0.05) greater than the amounts released from the hand-mixed glass ionomers. No significant differences in the cumulative amounts of fluoride released from triturated materials were found among the different trituration times.

Analysis of Variance↗
PubMed1994

Measurement of respirable glass and total fiber concentrations in the ambient air around a fiberglass wool manufacturing facility and a rural area.

Little data are available on ambient concentrations of glass fibers which along with other manmade vitreous fibers are receiving increased regulatory attention. The purpose of this study was to measure glass and total respirable fibers around a large fiberglass wool manufacturing plant and a rural area. Samples were collected on mixed esters of cellulose filters using high-volume air samplers at flow rates of 1.2 m3/min. Fibers were counted using a modified NIOSH 7400B procedure. Glass fibers were found in very low concentrations for both areas sampled; 90% of the samples were below the detectable limit of 0.00001 fibers/cc. Average glass fiber concentrations accounted for less than 1% of the total fibers measured. Dispersion modeling was used to estimate ambient glass fiber concentrations around the plant. Predicted and measured results showed relatively good agreement.

Air Pollutants, Occupational↗
PubMed1994

Bond strength measurements of fissure sealant to glass ionomer (polyalkenoate) cement.

The management of fissure caries is greatly simplified by restricting cavity preparation to the removal of caries and restoring the tooth with a combination of either glass ionomer cement or composite resin with fissure sealant. Clinically, however, problems are experienced in achieving satisfactory retention of fissure sealant to the surface of glass ionomer cement. This in vitro investigation describes the effects of different surface treatments of glass ionomer cement on the shear bond strength obtained with self-cured and light-cured fissure sealant. The application of a halophosphorus ester of bis-glycidyl methacrylate (bis-GMA, Scotchbond Dual Cure) to the set surface of the glass ionomer cement significantly increased the shear bond strength values observed with both the self-cured and light-cured varieties of an unfilled bis-GMA pit and fissure sealant (Delton). Etching of the glass ionomer surface did not significantly improve the shear bond strengths observed.

Analysis of Variance↗
PubMed1993

Shear strength and microleakage of light-cured glass ionomers.

Bond to dentin and marginal integrity of three light activated glass ionomer cements were evaluated, and compared to a traditional chemical-cured glass ionomer cement. Results indicated no significant difference in shear bond strength among the glass ionomer cements tested. However, there was a significant difference among glass ionomer cements in bond strength variability, with coefficients of variation ranging from 55 to 102%. A discrepancy between manufacturers' instructions and optimum curing times is one possible explanation for these results. There were also no significant differences in microleakage among glass ionomer cements. Most samples exhibited minimal or no microleakage.

Analysis of Variance↗
PubMed1996

Proteins involved in the Vroman effect during exposure of human blood plasma to glass and polyethylene.

The amounts of fibrinogen adsorbed to glass from various human blood plasmas have been measured as a function of time. The plasmas were 11 single donor plasmas, pooled plasma, a single donor high molecular weight kininogen (HMWK)-deficient plasma and HMWK-deficient plasma, which had been reconstituted with HMWK. For adsorption times between 1 min and 1 h more fibrinogen adsorbed from HMWK-deficient plasma compared with the amounts of fibrinogen which adsorbed from the other plasmas. This result supports the conclusion of several authors that HMWK is involved in the displacement of fibrinogen, initially adsorbed from normal human plasma to glass. Glass surfaces, pre-exposed to solutions of plasma and subsequently exposed to 1:1 diluted plasma, gives rise to a relatively high adsorption of HMWK which is independent of the plasma concentration of the precoating solution. The results indicate that HMWK from 1:1 diluted plasma is involved in the displacement of proteins from glass surfaces which had been pre-exposed to solutions with a low plasma concentration. Experiments with polyethylene as a substrate reveal that high density lipoprotein (HDL) from 1:1 diluted plasma is involved in the displacement of proteins from polyethylene surfaces which had been pre-exposed to solutions with a low plasma concentration. Moreover, evidence is presented that substantial amounts of albumin and fibrinogen, adsorbed from 1:1000 diluted plasma to glass and polyethylene, are displaced from the surfaces of these materials by proteins from 1:1 diluted plasma different from HMWK and HDL.

Adsorption↗
PubMedDate not supplied

Bond strength of glass ionomers to coronal and radicular dentin.

A study was conducted to compare the shear bond strength of a glass-ionomer cement and glass-ionomer base to coronal and radicular dentin. Two different glass ionomers were bonded to paired coronal and radicular human dentin surfaces that had received no surface treatment or had been treated passively for 20 seconds with either 40% or 25% polyacrylic acid. When only the effect of the type of dentin surface was considered, glass-ionomer bonds were greater to radicular dentin than to coronal dentin. With one exception, bond strengths to both dentin surfaces were greater with the base ionomer (Ketac-Bond) than with the luting cement (Ketac-Cem). Bond strengths of both glass ionomers were greater after dentin surface treatment with either 25% or 40% polyacrylic acid than with no treatment.

Acid Etching, Dental↗
PubMed1996

Properties of resin-modified glass-ionomer restorative materials and two polyacid-modified resin composite materials.

The objective of the study was to evaluate the physical properties of four resin-modified glass-ionomer cements (Fuji II LC, Ionosit Fil, Vitremer, Photac-Fil) and two polyacid-modified resin composite materials (Dyract and Variglass VLC)). They were compared with a hybrid resin composite (blend-a-lux) and a chemically cured glass-ionomer cement (ChemFil Superior). The compressive strength, flexural strength, modulus of elasticity, and surface microhardness of the resin-modified glass-ionomer materials and the polyacid-modified resin-composite materials were inferior to those of the hybrid resin composite and similar to those of the conventional glass-ionomer cement. The hybrid resin composite exhibited the lowest resistance to wear caused by brushing. Some of the materials showed a marked decrease in hardness at depths exceeding 2.0 mm. Generally, the strength properties of the tested resin-modified glass-ionomer materials and the polyacid-modified resin composite materials were inferior to those of the hybrid resin composite.

Chemical Phenomena↗
PubMed1994

Pulp reactions to light-cured glass ionomer cements.

This study compared the pulp responses to two light-cured glass ionomer liners with a chemically set glass ionomer lining cement and zinc oxide-eugenol. Deep Class V cavities were prepared at high-speed with carbide burs under a water coolant in 96 teeth of three young adult beagle dogs. The smear layer was left intact according to the manufacturers' recommendations. The cavities in each quadrant were lined with either Vitrebond light-cured glass ionomer liner, X-R Ionomer light-cured liner, GC lining cement or ZOE which served as a control. All cavities were restored with Silux Plus resin composite. The ZOE liner was covered with a varnish prior to the resin composite placement. The animals were terminated at 1, 4 and 12 weeks. Jaws were excised, fixed in 10% formalin and decalcified in 5% formic acid. Teeth were sectioned at 7 microns, and stained with hematoxylin and eosin. Selected slides were stained with the Brown and Hopps method for histologic demonstration of bacteria. The microscopic findings indicated that pulpal reactions to the two light-cured glass ionomer liners were minimal and comparable to those elicited by the chemically-cured glass ionomer lining cement and ZOE. Bacteria were observed in nine specimens but only one of these revealed a moderate pulp reaction.

Animals↗
PubMedDate not supplied

An in vitro caries inhibition of photopolymerized glass ionomer liners.

Caries inhibition of traditional chemical cure glass ionomers has been established. The newer photopolymerized glass ionomers demonstrate a different composition that may impair the ability of providing prevention to secondary caries at restoration margins. The purpose of this study was to evaluate the caries inhibition of photopolymerized glass ionomers (Vitrebond-3M Dental Products, Photac Bond-ESPE/Premier Dental Products) compared to a photopolymerized composite resin (Pertac Universal Bond-ESPE/Premier) control. Two standardized Class V preparations were placed in thirty permanent molars, the gingival margin placed below the cementoenamel junction. Equal numbers of preparations were restored with Vitrebond, Photac Bond and Pertac Universal Bond, according to manufacturer's instructions. The teeth were coated with an acid resistant varnish to within 2 mm of the restoration margins. All teeth were subjected to an artificial caries challenge (pH 4.2) for five days, then axial sections of 100 microns were cut longitudinally through the restored margins and photographed under polarized light microscopy. The polarized micrographs were projected onto a digitizing pad, where demineralized areas adjacent to the restoration margins were quantitated. Results demonstrated the mean (+/- S.D.) area (microns2) demineralization 100 microns from the restoration gingival margin to be: Photac Bond 66.1 +/- 27.8; Vitrebond 47.2 +/- 37.2; Pertac Universal Bond 120.9 +/- 66.0. Duncan's multiple range test indicated there was no statistically significant difference in demineralization inhibition between the two photopolymerized glass ionomers Photac Bond and Vitrebond (p < 0.05), but both photopolymerized glass ionomers demonstrated significantly less demineralization than the Pertac Universal Bond composite resin control (p < 0.05).

Dental Caries↗
PubMedDate not supplied

In vitro caries inhibition effects by conventional and resin-modified glass-ionomer restorations.

The ability of a material to inhibit recurrent caries formation is an important clinical therapeutic property. The objectives of this study were to develop an initial anticariogenicity profile (from fluoride release, to fluoride uptake, to resistance to an artificial caries challenge), testing the ability of conventional versus resin-modified glass-ionomer restorations to resist decay, and to study the effect of using intermediary dentin bonding agent components on the development of surface and wall carious lesions adjacent to a resin-modified glass-ionomer restoration. Cumulative fluoride release was measured from the immersion of disk-shaped specimens into deionized distilled water for 24 hours, 1, 2, 4, and 10 weeks. For the fluoride uptake and artificial caries test, standardized restorations were placed along the cementoenamel junction of extracted human molars. Secondary ion mass spectroscopy was used to determine the depth of fluoride uptake into the adjacent axial dentin from the restoration after 1 and 10 weeks. For the artificial caries test, the teeth were immersed into an acidified gelatin gel, pH 4.0, for 10 weeks. The development of recurrent decay was assessed using polarizing light microscopy. Statistical analyses were conducted using ANOVA and Fishers' LSD test (P < or = 0.05). There was generally greater fluoride release and uptake from the conventional glass ionomers, equivalent or less from the resin-modified glass ionomers, and none from the resin composite restorations. The use of an acid conditioner and primer from a dentin bonding system significantly increased the depth of fluoride uptake at 1 week. The additional use of an intermediary adhesive resin layer, however, significantly decreased the depth of fluoride uptake. The maximum depth of fluoride uptake into dentin was 300 microns at 10 weeks. Both conventional and resin-modified glass-ionomer restorations imparted resistance to dentin against the development of recurrent wall carious lesions in vitro. This was attributed to material fluoride release and uptake.

Cariostatic Agents↗
PubMedDate not supplied

Glass ionomer cement, an intelligent material.

The main task of a dental filling material is to permanently seal the dentinal wound and to restore the anatomy. In particular with respect to the former requirement, glass-ionomer cements exhibit, thanks to it's ingenious composition, unique properties, which allows it to react on external information in such a way that the cement automatically and adequately fulfills it's function as a proper restorative material. Because of it's setting mechanism, glass-ionomer cement restorations have a better perspective to seal the tissue than amalgam or resin composites do. As resistance to wear of glass ionomers is inferior to resin composites it proves to be a better dentin replacement, than a substitute for tooth enamel. Restorations made in a combination of glass-ionomer cement and resin composite, the so called sandwich restorations, have shown to function excellently, both at the tooth interface as well as the outer surface. As any leakage still cannot be excluded, the fluoride release at the margins of the restoration forms a wellcome contribution to the prevention of secondary caries. Once more, glass-ionomer cement shows to be intelligent by automatically activating an advantageous process when the environment requires it.

Dental Bonding↗
PubMed1997

In vitro marginal leakage around Class II resin composite restorations with glass-ceramic inserts.

The aim of the study was to evaluate in vitro the marginal seal in Class II resin composite restorations reinforced with glass-ceramic inserts. Forty Class II cavities, with the gingival margins located at the cementoenamel junction, were restored with Palfique Estelite light-cured resin composite and one of two different bonding agents, All Bond 2 and Tokuso Light Bond, with or without the inclusion of glass-ceramic inserts. The extent of dye penetration along the tooth-restoration interface was measured under an optical microscope. The marginal seal of composite restorations placed with All Bond 2 was significantly better than that of restorations placed with Tokuso Light Bond. There was significantly less microleakage in All Bond 2 restorations without glass-ceramic inserts than in All Bond 2 restorations containing glass-ceramic inserts. No significant difference in marginal seal was demonstrated between Tokuso Light Bond restorations with glass-ceramic inserts and those without inserts.

Bicuspid↗
PubMed1993

Biomechanical evaluation of bonding with glass ionomer cement.

This study was designed to determine the bond strength of three commercially available glass ionomer cements when used to bond mesh-backed medium twin standard edgewise (.022" x .028") brackets to enamel surface. The bond strength of one composite resin was compared with those of the glass ionomer cements. Scanning electron microscopic study of the debonded enamel surface was carried out to evaluate the effects of the bonding agents on enamel. The teeth were bonded with all the materials according to manufacturers' specifications. Each specimen was embedded in Dental stone with the bonded facial surface exposed. A special bracket holder was used to hold the brackets precisely under the wings during debonding. An Instron universal testing machine was used to measure the force required for bond failure. To simulate oral conditions, the direction of pull was so designed that it included an element of torsional stress along with tensile force. The findings indicate that Ketac-cem and Fuji II Glass ionomer cements hae adequate bond strength for clinical use. The scanning electron photomicrographs revealed that the enamel was least affected and well preserved in the Glass ionomer cement group. Further investigation is required to test the bond strengths of Glass ionomer cements clinically.

Biomechanical Phenomena↗
PubMedDate not supplied

Implant placement enhanced by bioactive glass particles of narrow size range.

Poor bone quality and quantity are often related to implant failure. Synthetic bone grafts may be used to enhance the formation of new bone in bone defects. The purpose of this animal study was to determine the efficacy of bioactive glass particles of narrow size range (300 to 335 microns, Biogran) in the treatment of bone defects prior to implant placement. On both sides of the mandible of six beagle dogs, areas of partial edentulousness were created by the removal of the intra-alveolar septa to obtain large defects, instantly filled on one side with bioactive glass particles. The other side was left empty as a control. After a healing period of 4 months, three oral implants each were placed in the glass-treated area and in the control zone. In three dogs, the implants were left subgingival for 3 months after which histologic sections were made. In the remaining three dogs, the implants were functionally loaded with a fixed partial prosthesis for 7 weeks before sacrifice. Qualitative and quantitative analysis of both groups revealed statistically significantly more bone tissue and higher remodeling activity at the interface and at a distance of implants placed in glass-treated areas, compared to implants placed in untreated regions. Implant placement in bioactive glass-filled defects was not jeopardized, on the contrary.

Alveolar Bone Loss↗
PubMed1999

Influence of P2O5 on crystallinity of apatite formed in vitro on surface of bioactive glasses.

Two sol-gel glasses with 80 mol % SiO2 were prepared in the system SiO2-CaO-P2O5; the first one had 3 mol% P2O5 in its composition, and the second one was P2O5 free. The in vitro behavior of glasses was studied by soaking them in simulated body fluid for 7 days at 37 degrees C. After the in vitro test, the study by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, electron diffraction, and transmission electron microscopy showed an apatite-like layer had formed on the surface of both glasses. However, for identical soaking time, the apatite crystals formed on the surface of the glass containing P2O5 in the composition were larger. Therefore, the presence of P2O5 in the sol-gel glass composition promotes the crystal growth of the apatite.

Ceramics↗
PubMed2000

Quantitative comparison of bone growth behavior in granules of Bioglass, A-W glass-ceramic, and hydroxyapatite.

The hypothesis that bioactive glass particulate increases the rate of bone proliferation over that of synthetic hydroxyapatite and bioactive glass-ceramic was tested in these experiments. Three types of bioactive particles-45S5 Bioglass(R), synthetic hydroxyapatite, and A-W glass-ceramic-were implanted in 6-mm-diameter holes drilled in the femoral condyles of mature rabbits. Bone growth rate was measured using an image processor. 45S5 Bioglass(R) produced bone more rapidly than either A-W glass-ceramic or hydroxyapatite. At the later time periods, 45S5 Bioglass(R) was resorbed more quickly than A-W glass-ceramic. Synthetic hydroxyapatite was not resorbed at all. Backscattered electron imaging suggested that the resorption process occurred by solution-mediated dissolution, which produced chemical changes in the enclosed particulate. It was concluded that the rate of bone growth correlates with the rate of dissolution of silica as the particles resorb.

Animals↗
PubMed2000

Bioactive glass serves as a substrate for maintenance of phenotype of nucleus pulposus cells of the intervertebral disc.

The objective of the study was to investigate the capability of bioactive glass 45S5 to serve as a substrate for nucleus pulposus cells in vitro. Nucleus pulposus cells were isolated from adult rabbit discs and seeded onto bioactive glass. At selected time intervals, the cells and glass were evaluated. We found that the cells rapidly attached to the substrate, colonizing it within 12 h. By 21 days, they had formed a lawn of cells over the glass substrate. DNA measurements showed a progressive increase in cell number with time. The phenotype was maintained; the cells expressed aggrecan, and collagen type II and I, but were negative for collagen type X. CD44, a cell-surface glycoprotein that binds hyaluronate, was also expressed by these cells. Electron dispersive X-ray analysis and Fourier transform infrared spectroscopy revealed calcium phosphate-rich layer formation on the substrate surface. The results of this study suggest that nucleus pulposus cell proliferation may be an anchorage dependent event, and that the cells use the calcium phosphate-rich layer to facilitate cell adhesion, and subsequent proliferation. These findings point to the importance of the conditioned bioactive glass as a substrate for nucleus pulposus cells.

Aggrecans↗
PubMed2003

Role of temperature in controlling performance of photorefractive organic glasses.

We present a detailed temperature-dependence study of dielectric, birefringent, conductive, and photorefractive (PR) properties of high-performance low-molecular weight organic glasses that contain 2-dicyanomethylene-3-cyano-2,5-dihydrofuran (DCDHF) derivatives. DCDHF organic glasses sensitized with C60 exhibit high two-beam coupling gain coefficients in the red-wavelength region. However, in the best performing DCDHF glasses at room temperature the PR dynamics are limited by slow molecular reorientation in the electric field. While orientational and, therefore, PR speed can be significantly improved by increasing the temperature above the glass-transition temperature of the material, the steady-state performance may worsen. Comprehensive study of the temperature dependence of various processes, which contribute to the PR effect in DCDHF glasses, clarifies the limiting factors and allows for optimization of the overall PR performance.

Journal Article↗