Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “GLASSES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed2005

Biomimetic mineralization of partially bioresorbable glass fiber reinforced composite.

The aim of this study was to investigate the biomimetic mineralization on the surface of a glass fiber reinforced composite with partially resorbable biopolymer matrix. The E-glass fibers were preimpregnated with a novel biopolymer of poly(hydroxyproline) amide, and further impregnated in the monomer system of bis-phenyl glycidyl dimethacrylate (Bis-GMA)--triethylene glycol dimethacrylate (TEGDMA), which formed interpenetrating polymer networks (IPN) with the preimpregnation polymer. After light-initiated polymerization of the monomer system, the rhombic test specimens (n = 6) were immersed in the simulated body fluid (SBF) with the bioactive glass for 24 h, and then the apatite nuclei were allowed to grow for 1, 3, 5 and 7 days in the SBF. The control test specimens (n = 3) were immersed in SBF without the bioactive glass. According to the scanning electron microscope (SEM), a mineral layer was formed on the surface of all the specimens, which were immersed with bioactive glass. The layer was thickened by the prolonged immersion time to a uniform layer. The Ca/P atomic ratio of the mineral varied between 1.30 and 1.54 as analyzed by the energy dispersive X-ray analysis (EDXA). The Fourier transform infrared spectroscopy (FT-IR) spectra gave signals for the mineral, which are characteristic of both bone-like apatite and orthocalciumphosphate. In conclusion, the mineral layer was formed on the surfaces of the specimens by biomimetic mineralization, the mineral being a mixture of bone-like apatite, orthocalciumphosphate and other calcium phosphates.

Apatites↗
PubMed2006

Investigation of silica-iron-phosphate glasses for tissue engineering.

Phosphate-based glasses have previously been examined for tissue engineering applications, however they degrade rapidly in solution reducing its pH to below 5. This study presents a series of phosphate-based glass compositions that degrade at a lower rate, allowing the pH to remain close to neutral in cell culture medium. The compositions investigated were P50Ca30Na(15-x)Fe5Si(x) where x = 0, 1, 3 and 5 mol%. The dissolution and effect on pH in distilled water and cell culture medium, and ion release in distilled water were investigated over 7 days and MG63 cell attachment to glass fibres was observed after 24 hrs. Dissolution was much slower in cell culture medium (3% mass loss) compared to distilled water (50% mass loss), due to the large quantity of ions and pH buffer present. After 7 days, in cell culture medium the pH remained between 7 and 8.5, however the pH in distilled water fell to between 4 and 3, with the final pH being lower the greater the SiO2 content. Increasing the SiO2 content of the glass resulted in an increase in dissolution rate whilst the pH was maintained at 7 in cell culture medium. The attachment and spreading of MG63 cells was observed on all compositions. These glass compositions may therefore be suitable for tissue engineering applications.

Biocompatible Materials↗
PubMed2006

Genotoxicity and cytotoxicity of glass ionomer cements on Chinese hamster ovary (CHO) cells.

Glass ionomer cements are widely used in dentistry as restorative materials and adhesives for composite restorations. However, the results of genotoxicity studies using these materials are inconclusive in literature. The goal of this study was to examine the genotoxic and cytotoxic potential of three different glass ionomer cements available commercially (Ketac Cem, Ketac Molar and Vitrebond) by the single cell gel (comet) assay and trypan blue exclusion test, respectively. For this, such materials were exposed to Chinese hamster ovary (CHO) cells in vitro for 1 h at 37( composite function)C. Data were assessed by Kruskall-Wallis nonparametric test. The results showed that the powder from Ketac Molar displayed genotoxicity only in the maximum concentration evaluated (100 microg/mL). In the same way, the liquid from Vitrebond at 0.1% dilution caused an increase of DNA injury. Significant differences (P<0.05) in cytotoxicity provoked by all powders tested of glass ionomer cements were observed for exposure at 1,000 microg/mL concentration. With respect to liquids of glass ionomer cements evaluated, the major toxic effect on cell viability was produced at 10%, beginning at the dilution of 0.5% for Vitrebond. Taken together, we conclude that some components of glass ionomer cements show both genotoxic and cytotoxic effects.

Animals↗
PubMed1988

Microsequence analysis of peptides and proteins. VIII. Improved electroblotting of proteins onto membranes and derivatized glass-fiber sheets.

We have quantitatively examined the various parameters affecting the electrotransfer and sequence analysis of proteins from sodium dodecyl sulfate (SDS) gels to derivatized glass fiber paper or to polyvinyldifluoride (PVDF) membranes. Transfer yields in the range of 90-95% can be obtained for proteins in the molecular weight range of 10-90 kDa for transfer from 12% SDS gels to glass fiber paper derivatized with either QAPS (N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride) or APS (aminopropyltriethoxysilane). In order to achieve these yields, it was necessary to modify the conditions described by R. Aebersold et al. (J. Biol. Chem. 261, 4229-4238, 1986). We activated the glass fiber paper with dilute ammonia water and derivatized the activated glass fiber paper with QAPS and APS in anhydrous solvents which were allowed to slowly absorb moisture during the derivatization process. The transfer yield varied with transfer time versus molecular weight of the protein for a given percentage gel. Shorter transfer times and higher yields were obtained for higher molecular weight proteins on 8% gels. Lower molecular weight protein gave higher yields from 12% gels under similar transfer conditions. Sequencing yields of the transferred proteins were in the range of 40-80%, but a number of background peaks were observed on HPLC analysis of the phenylthiohydantoin amino acid derivatives. Transfer yields in the range of 85-95% were observed for similar experiments with PVDF membranes. In order to achieve these yields, it was necessary to modify the conditions described by P. Matsudaira (J. Biol. Chem. 262, 10035-10038, 1987). A lower voltage and longer transfer times gave higher transfer yields. In order to achieve consistently high transfer yields, it was also necessary to precoat the PVDF membranes with Polybrene. The PVDF membranes were cut into approximately 1-mm-wide strips and inserted into a continuous flow reactor (J. E. Shively, P. Miller, and M. Ronk, Anal. Biochem. 163, 517-525, 1987) for sequence analysis. Overall yields of samples loaded onto gels, electrotransferred to Polybrene-coated PVDF membranes, and sequenced ranged from 50-60% for beta-lactoglobin (10-50 pmol loaded onto SDS gels) to 20-30% for bovine serum albumin and soybean trypsin inhibitor (50 pmol loaded onto SDS gels). A comparison of the two methods shows clear advantages for the PVDF membranes over the derivatized glass fiber paper, including the ability to directly sequence the Coomassie blue-stained PVDF membranes, and the lower backgrounds observed on subsequent sequence analysis.

Amino Acid Sequence↗
PubMed1993

Fluoride uptake in human dentine from glass-ionomer cement in vivo.

The purpose was to examine F uptake and distribution in dentine from a F-containing glass-ionomer cement in vivo. Nine volunteers were selected from dental students who were scheduled for extraction of their third molars. Two cavities were prepared on the same occlusal surface of the third molars for each subject; one was restored with glass-ionomer cement (Virtabond), the other with zinc phosphate cement as a control. After 3 months the teeth were extracted. F profiles in the dentine from the cavity floor to the pulpal surface were determined in tissue immediately adjacent to the restorations. An abrasive micro-sampling technique was used. The F concentration of the dentine was highest immediately beneath glass-ionomer cement filling, decreasing towards the pulpal surface. Overall F concentrations were greater in the dentine beneath the glass-ionomer cement than in that beneath the zinc phosphate cement. It was concluded that the glass-ionomer cement markedly enhanced fluoride uptake by underlying dentine in vivo.

Adult↗
PubMed1986

Detection of glass foreign bodies by radiography.

During a 14-month period patients with suspected glass foreign bodies were radiographically examined before removal of the glass. In 25 out of 26 patients the glass foreign bodies were detected. In 9 patients the glass foreign bodies had been overlooked on previous visits to doctors or hospitals, where the examination had been limited to inspection and sometimes probing of the wound. Almost all glass foreign bodies can be detected radiographically. With high-resolution or mammographic techniques even minute splinters may show up.

Adult↗
PubMed1992

Sealing effectiveness of light-cured glass ionomer cement liners.

Glass ionomer materials have been used as liners or bases beneath restorations, but light-cured varieties have recently been introduced. Microleakage at the restoration/tooth interface in cervical cavities was used to test the adhesion to dentin of two new light-cured glass ionomer cement lining materials, XR-Ionomer and Fuji Lining LC. Wedge-shaped cervical cavities were prepared on extracted teeth with a gingival cavosurface margin involving dentin, and the specimens were assigned randomly to three groups. The experimental groups were restored with two light-cured glass ionomer cements, the controls were restored with a chemically cured glass ionomer cement; and marginal leakage was assessed by dye penetration. The two light-cured glass ionomer cements displayed some adhesion to dentin in class V test cavities, but there was no significant difference between the two materials.

Dental Bonding↗
PubMed1989

Properties of a glass-ionomer/resin-composite hybrid material.

A small percentage of the liquid resin used in commercial dental composites was added to the liquid used in a commercial glass-ionomer restorative in order to produce a fluoride-containing hybrid restorative-type material that would adhere to dentin while being stronger, less brittle, and less sensitive to desiccation in the oral cavity than glass ionomer. Compressive strength, yield strength, elastic modulus, fracture toughness, and tensile strength were analyzed for this hybrid, light-cured material. In addition, the solubility in water, adhesion to dentin, and surface roughness were also examined in vitro. The results suggest that the early (one-hour) mechanical properties of the hybrid material exceed those of glass ionomer. In addition, the brittleness and solubility of the material are less than those of commercial glass ionomer, while adhesion to dentin is unaffected. Most importantly, surface crazing, a documented problem with some glass ionomers when they become desiccated, is alleviated with this hybrid formulation.

Composite Resins↗
PubMed1991

In vitro abrasion resistance and hardness of glass-ionomer cements.

The aim of this study was to compare the abrasion resistance and surface hardness of four glass-ionomer cements. The effects of hydration and dehydration on wear resistance were also studied. A composite material, enamel, and dentin were used as controls. For wear testing, the specimens were abraded on abrasion discs under water. All glass ionomers showed greater wear than composite and enamel, but less wear than dentin. Ketac-Fil showed the highest and Ketac-Silver the lowest wear resistance. Hydration or dehydration of the specimens did not significantly influence the wear rate of conventional glass ionomers, but the wear resistance of Ketac-Silver was increased due to dehydration. Ketac-Fil had the highest and Ketac-Silver the lowest hardness rating of the glass ionomers. The cement material did not show abrasion resistance better than that of the conventional glass ionomers, as has previously been suggested.

Cermet Cements↗
PubMed1992

Microleakage comparison of dentin bonding systems with glass ionomer.

Glass-ionomer cements have been suggested as substitutes for dentin-bonded composites. This investigation was designed to compare microleakage of glass-ionomer restorations with that of dentin-bonded composite restorations. Eighty extracted human molars were used in this study. Class V cavities were prepared on the mesial and distal surfaces of each tooth. The distal cavities were restored with Ketac-Fil Glass Ionomer (ESPE). The mesial cavities were divided into four groups and treated with four different dentin bonding systems: Gluma (Columbus Dental), Tenure (two-part powder system; second version, Den-Mat), Scotchbond 2 (3M), and an experimental ferric oxalate system. The commercial materials were placed according to the manufacturers' instructions. The teeth were then thermocycled 3800 cycles between 5 degrees C and 55 degrees C, subjected to silver nitrate staining, and sectioned for microleakage evaluation by three evaluators on a scale of 0 to 4. The ferric oxalate system exhibited significantly less microleakage (median score = 1; Wilcoxon paired testing, p = 0.01) than the glass ionomer (median score = 3). The other dentin bonding systems were similar in microleakage to the glass ionomer (median score = 3).

Composite Resins↗
PubMed1993

Fluoride release in vitro from various glass ionomer cements and resin composites after exposure to NaF solutions.

The release of fluoride from 1) discs made from five glass ionomer cements and two composites, and 2) the same discs after exposure to different NaF solutions, were studied. The specimens were placed in distilled water for 10 wk. After 24 h and then once a week, the specimens were transferred to fresh distilled water. After 5 wk, the specimens were divided into four groups and exposed to 0, 0.02, 0.2 and 2% NaF solutions for 5 min. The fluoride release was highest during the first week after preparation, after which it decreased sharply and then more slowly. The amount of fluoride released was ordered: liner/base > restorative glass ionomer > composites. The composites released significantly less fluoride than the glass ionomer cements. After exposure to NaF, the fluoride release was significantly higher for the silver cermet material than for the other glass ionomers tested. From a clinical point of view, the results from this study imply that glass ionomer restorations may act as intraoral devices for the controlled slow release of fluoride at sites at risk for recurrent caries.

Acrylic Resins↗
PubMed1993

Early strength of glass ionomer cements.

The present study compared the compressive, tensile and flexural strengths of 26 commercial glass ionomer cements, which were evaluated 24 h after the beginning of the setting reaction. In order to give a global estimation of their overall strength, a coefficient was attributed to each glass ionomer cement. This strength coefficient provided a ranking of the tested materials. The highest scores were obtained by the restorative glass ionomers; however, these materials exhibited lower mechanical properties than the more classic restorative materials such as amalgams or composites. The results also showed a large scattering of the mechanical properties among the luting and lining glass ionomer cements. The creep behavior of the glass ionomer cements was also investigated.

Analysis of Variance↗
PubMed1994

Mechanical behavior of glass ionomer cements affected by long-term storage in water.

OBJECTIVES: The early strength of glass ionomer cements was investigated previously (Cattani et al., 1993). Using the same set of glass ionomer cements, this study was designed to determine if mechanical property degradation occurred after an extended period of storage in water. METHODS: In the present study, the effect of aging in water on the compressive, tensile and flexural strengths of twelve commercial glass ionomer cements was evaluated at different time intervals after the beginning of the setting reaction. The aging periods varied from 24 h to 12 mon. RESULTS: The results show that the mechanical properties of the tested materials are in some cases affected by long-term aging in water. The evolution of strength follows distinct patterns of change. It has been established that the glass ionomer cements are neither characterized by a continuous increase nor a continuous decrease in strength. Most of the materials tested maintained a constant strength. However, several of them first display an improvement of the mechanical strength followed by a reduction. In this case, the 24h and the 12 mon strengths are usually similar. SIGNIFICANCE: The aging mechanisms of glass ionomers are complex. Strengthening probably results from additional crosslinking and build-up of a silica gel phase, whereas weakening may result from erosion and plasticizing effect of water.

Acrylic Resins↗
PubMed1994

Effect of cement film thickness on the fracture resistance of a machinable glass-ceramic.

OBJECTIVES: The aim of this study was to determine the fracture resistance of a machinable glass-ceramic plate cemented to a resin composite block as a function of the cement film thickness for two types of cement. METHODS: Ceramic plates were cemented to resin composite blocks using either zinc phosphate cement or a resin composite cement. For the zinc phosphate cement, the film thickness was 33 +/- 8 microns or 128 +/- 8 microns; for the resin composite cement, the thickness ranged from 26 +/- 11 microns to 297 +/- 48 microns. The elastic modulus was determined for each of the cements. Fracture loads were obtained by using a spherical steel indenter in the center of the glass-ceramic plate. The Weibull distribution was used for the statistical analysis. RESULTS: For glass-ceramic plates cemented with zinc phosphate cement, the fracture resistance was independent of the film thickness. When the resin composite cement was used, a gradual decrease of the fracture strength was observed that became statistically significant at a cement thickness of 300 microns or more. The characteristic fracture strength of glass-ceramic plates cemented with the resin composite cement was about 75% higher than when using the zinc phosphate cement. This difference is attributed to the bonding of the resin cement to the ceramic plate and the supporting structure. SIGNIFICANCE: The findings of this study suggest that the resistance to fracture due to indentation of the glass-ceramic may not be affected by the cement film thickness as much as previously thought.

Acrylic Resins↗
PubMed1995

The influence of water sorption on the development of setting shrinkage stress in traditional and resin-modified glass ionomer cements.

OBJECTIVES: The aim of this study was to determine the setting stress development for some traditional and resin-modified glass ionomer cements and to assess the effect of early water exposure to this stress. METHODS: The development of the setting stress of the glass ionomer cements was determined in a tensilometer set-up as described earlier by Feilzer et al. (1987). RESULTS: The results of this study show the influence of water sorption on the development of setting shrinkage stress in bonded glass ionomer cements. When curing took place under isolated conditions (no hydration or dehydration), all the traditional glass ionomer cements investigated fractured spontaneously, either adhesively and/or cohesively, due to the developing stress. Early exposure to water led to stress relief and prevented spontaneous fracturing. For the light-cured products, no spontaneous failures were observed under isolated conditions. Stress relief due to water sorption reversed the contraction stress into an expansion stress. SIGNIFICANCE: Exposure of traditional glass ionomer cements to water at an appropriate time by the use of permeable matrix systems is advised. Whether the conversion of contraction stresses into expansion stresses as observed for the resin-modified products, is beneficial for a restoration requires further study.

Absorption↗
PubMed1992

Influence of substituting B2O3 for CaF2 on the bonding behaviour to bone of glass-ceramics containing apatite and wollastonite.

Glass-ceramics containing crystalline oxy-fluoroapatite (Ca10(PO4)6(O,F2)) and wollastonite (CaSiO3) (designated AWGC) are reported to have a fairly high mechanical strength as well as the capability of forming a chemical bond with bone tissue. The chemical composition is MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, and CaF2 0.5 in weight ratio. In this study the influence of substituting B2O3 for CaF2 on the bonding behaviour of glass-ceramics containing apatite and wollastonite to bone tissue was investigated. Two kinds of glass-ceramics containing apatite and wollastonite were prepared. CaF2 0.5 was replaced with B2O3 at 0.5 and 2.0 in weight ratio (designated AWGC-0.5B and AWGC-2.0B). Rectangular ceramic plates (15 x 10 x 2 mm, abraded with No. 2000 alumina powder) were implanted into a rabbit tibia. The failure load, when an implant detached from the bone, or the bone itself broke, was measured. The failure load of AWGC-0.5B was 8.00 +/- 1.82 kg at 10 weeks after implantation and 8.16 +/- 1.36 kg at 25 weeks after implantation. The failure load of AWGC-2B was 8.08 +/- 1.70 kg at 10 weeks after implantation and 9.92 +/- 2.46 kg at 25 weeks after implantation. None of the loads for the two kinds of glass-ceramics decreased as time passed. Giemsa surface staining and contact microradiography revealed direct bonding between glass-ceramics and bone. SEM-EPMA showed a calcium-phosphorus rich layer (reaction zone) at the interface of ceramics and bone tissue. The thickness of the reaction zone was 10 to -15 microns and did not increase as time passed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Erosion and compressive strength of hybrid glass ionomer cements when light activated or chemically set.

It is claimed that light-activated hybrid glass ionomer cements offer advantages over the conventional glass ionomer lining materials. The compressive strengths and erosion rates of two hybrid glass ionomer lining cements, when light activated and chemically set, were compared with conventional glass ionomer cements. The results demonstrated that the erosion rates of the light-activated materials were comparable with those of the conventional materials. The conventional material, Ketac-Bond, was stronger than the light-activated hybrids. When the hybrid materials were allowed to set chemically alone, their performance was inferior to the conventional glass ionomer lining cements.

Glass Ionomer Cements↗
PubMed1994

Aluminium release from glass ionomer cements during early water exposure in vitro.

Aluminium is a major constituent of glass ionomer cements. During mixing and setting aluminium is released from the glass into the polyalkeonic acid solution. Part of this aluminium may not combine with the polyalkeonic acid, but may be released from the cement. The aluminium release from auto-cured and light-cured glass ionomer cements during early water exposure was studied. The former cements released more aluminium than the latter. Scanning electron microscopy (SEM) showed extensive loss of polymer matrix for the cements with the highest aluminium release. Insufficient curing of light-cured cements also resulted in loss of matrix. It is suggested that the considerable release of aluminium from glass ionomer cements during early water exposure may explain the reported lack of mineralization of predentin in the pulp beneath glass ionomer cements. This would correspond to the inhibiting effect of aluminium on bone mineralization.

Aluminum↗