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PubMed2000

A comparison of the effects of two kinds of glass-ionomer cement on human gingival fibroblast attachment, proliferation and morphology in vitro.

The aim of this study was to compare the response of cultured human gingival fibroblasts to two kinds of glass-ionomer cement in vitro with regards to understanding the biocompatibility of these materials and their suitability for use as subgingival restorative materials. The glass-ionomer cements tested were Ketac Fil, and GC Fuji II. These cements were mixed according to the manufacturers' directions and condensed into tissue culture wells or cavities prepared on the root surfaces of extracted teeth. Healthy root slices and untreated tissue culture wells were used as controls. Several features such as attachment, proliferation and morphology of cells were studied. The results indicated that cells could not attach to the glass-ionomer cements unless they had been washed with distilled water and tissue culture media. No significant difference in initial attachment (1.5h) and long term attachment (48h) between the groups tested was noted. No significant difference was observed between levels of proliferation for human gingival fibroblasts grown on Ketac Fil, Fuji II, root slices and culture wells. No significant alterations of the cytomorphology could be detected in glass-ionomer cement compared with root slices. These results indicate that provided the surface is adequately washed, Ketac Fil, and Fuji II may be acceptable subgingival root surface restorative materials.

Analysis of Variance↗
PubMedDate not supplied

Effects of daily fluoride exposures on fluoride release by glass ionomer-based restoratives.

It is well documented that glass ionomer cements absorb and release fluoride following single fluoride exposures. This study examined fluoride release among three glass ionomer-based restorative materials following multiple daily exposures to three topical fluoride regimens. Using a Delrin mold, 32 cylindrical specimens, each of a glass ionomer (Ketac-Fil), resin-modified glass ionomer (Photac-Fil) and polyacid-modified resin (Dyract AP) were created. Each specimen was subjected to one of four daily treatments (n = 8): (1) no fluoride treatment (control); (2) application of a fluoride dentifrice (1000 ppm) for one minute once daily; (3) application of the same dentifrice for one minute twice daily; (4) the same regimen as (3), plus immersion in a 0.05% sodium fluoride (NaF) mouth rinse (225 ppm) for one minute immediately following the second dentifrice application. Each specimen was suspended in a polyethylene test tube containing 1.0 ml demineralizing solution (pH 4.3) at 37 degrees C for six hours, then transferred to a new test tube containing 1.0 ml remineralizing solution (pH 7.0) at 37 degrees C for 18 hours. Fluoride treatments were completed at the time of transfer daily for seven days. Media solutions were buffered with equal volumes of TISAB II; fluoride levels were measured using a digital ion analyzer and fluoride electrode. Fluoride release decreased significantly from Day 1 to Day 3 for all materials regardless of fluoride treatment (Repeated Measures ANOVA, Tukey HSD, p < 0.05). All specimens released significantly more fluoride in demineralizing solution than in remineralizing solution. For Days 2-7, Treatment 4 produced greater fluoride release than both the control and Treatment 2 for all three materials (p < 0.05); For each material, the fluoride release produced by Treatments 3 and 4 was statistically similar on most days throughout the study. By Day 7, Photac-Fil demonstrated both the greatest total fluoride release and the greatest rechargability, followed by Ketac-Fil and Dyract AP. Although subsequent daily fluoride release never approached that of Day 1, increasing daily fluoride exposures enhanced fluoride release for all three restorative materials.

Absorption↗
PubMed2003

Microstructured apertures in planar glass substrates for ion channel research.

We have developed planar glass chip devices for patch clamp recording. Glass has several key advantages as a substrate for planar patch clamp devices. It is a good dielectric, is well-known to interact strongly with cell membranes and is also a relatively in-expensive material. In addition, it is optically neutral. However, microstructuring processes for glass are less well established than those for silicon-based substrates. We have used ion-track etching techniques to produce micron-sized apertures into borosilicate and quartz-glass coverslips. These apertures, which can be easily produced in arrays, have been used for high resolution recording of single ion channels as well as for whole-cell current recordings from mammalian cell lines. An additional attractive application that is greatly facilitated by the combination of planar geometry with the optical neutrality of the substrate is single-molecule fluorescence recording with simultaneous single-channel measurements.

Animals↗
PubMed2003

[Prevention of enamel demineralization adjacent to orthodontic brackets bonded with resin-modified glass ionomer: an in vitro pH cycling study].

OBJECTIVE: To investigate the resin-modified glass ionomer cement for inhibition of enamel demineralization adjacent to orthodontic brackets under a pH cycling experiment. METHODS: The study used 5 pairs of extracted human premolars. The experiment teeth were bonded with resin-modified glass ionomer, the control teeth were bonded with composite resin. All samples were under the pH cycling experiment each day for 60 days. Demineralization lesions of enamel adjacent to orthodontic brackets were evaluated with polarized light microscopy. The depth and area of the lesion, and the distance between the edge of the adhesive on the enamel surface and the border of the lesion were measured. RESULTS: The depth and area of lesions of control were greater than those of experiment group were. Paired t test showed significant differences (p < 0.001). There was always a distance between the lesions border and the glass ionomer cement. In control group, all lesions were developed under the edge of composite resin. CONCLUSION: It was suggested that resin-modified glass ionomer may become an orthodontic bonding agent to minimize enamel demineralization.

Glass Ionomer Cements↗
PubMed1992

The relative shear bond strength of visible light-curing and chemically curing glass-ionomer cement to composite resin.

The purpose of this study was to compare the shear bond strength to composite resin of a light-curing glass-ionomer cement with that of various chemically curing glass-ionomer cements. Light-cured composite resin cylinders were bonded to cylindrical glass-ionomer substrates after etching for 30 seconds with 37% phosphoric acid. Specimens were maintained in distilled water for 7 days and then thermocycled in water baths. One group of light-cured glass-ionomer cement substrates was not etched. The interfacial bond strength of these specimens was measured in shear. Cement shear strength was also evaluated. Statistical analysis showed the light-curing cement to have a significantly higher bond strength to composite resin than any of the chemically curing cements tested.

Analysis of Variance↗
PubMed1992

Visible light-hardened glass-ionomer-resin cement restorations for primary teeth: new developments.

Bonded glass-ionomer-silver-cement cement and visible light-hardened glass-ionomer liner and base material have proven to be reliable dentinal and enamel restoratives since the mid-1980s. When used within their limitations, they offer advantages over mechanically interlocked silver amalgam material. A light-hardened glass-ionomer-resin cement restorative material, which appears to have greater wear resistance and fracture toughness than prior glass-ionomer cements, has been introduced. This paper describes use of the new material and discusses its potential future implications.

Acrylic Resins↗
PubMedDate not supplied

Shear resistance of silver- and stainless steel-reinforced glass-ionomer cements bonded to enamel and dentin.

The shear bond strength to human dentin and enamel was evaluated for four glass-ionomer cements: an experimental stainless steel-reinforced glass-ionomer cement, two commercially available silver-reinforced cements, and a conventional glass-ionomer cement. Bonded specimens were stored in distilled water for 7 days during which time they were subjected to thermocycling in water baths at 5 degrees C and 55 degrees C for a 1-minute dwell time per bath and 1500 cycles. Specimens were then shear tested. The experimental stainless steel-reinforced glass-ionomer cement had a significantly higher bond strength to enamel (P < .01) and dentin (P < .05) than did the commercially available cements.

Analysis of Variance↗
PubMed1992

Clinical comparison of Class V resin composite and glass ionomer restorations.

Three techniques for restoring abrasion/erosion lesions were evaluated over a 2-year period: 1) glass ionomer restoration (Ketac-Fil); 2) composite restoration with a dentin bonding agent (Silux Plus, Scotchbond 2); 3) composite restoration with glass ionomer liner and a dentin bonding agent (Silux Plus, Vitrebond, Scotchbond 2). There were 116 lesions restored and 115 evaluated for color match, cavosurface discoloration, surface texture, caries development, and retention. Most restorations were rated clinically acceptable for color match, cavosurface discoloration, surface texture, and caries development when measured at 2 years. Glass ionomer restorations and composite restorations with a glass ionomer liner and a dentin bonding agent demonstrated better retention rates, 97.4% and 100% respectively, than the composite restorations with a dentin bonding agent only (86.8%) (Cochrane Q test, P = 0.07).

Aged↗
PubMed1992

Properties of trypsin and of acid phosphatase immobilized in sol-gel glass matrices.

Trypsin and acid phosphatase-containing silica sol-gel glasses were obtained by mixing a solution of an enzyme with polyethylene glycol (PEG) 6000 and tetramethoxy orthosilicate at room temperature, followed by gelation and drying. Activity of the immobilized trypsin toward small substrates, such as N-benzoyl-L-arginine-4-nitroanilide at its Km, for the best preparations equaled that of the soluble enzyme. Polylysine (M(r) less than or equal to 13,000) and aprotinin (M(r) = 6,500) inhibited this activity. Larger polylysines as well as soybean trypsin inhibitor (M(r) = 20,100) were ineffective. The sol-gel-entrapped trypsin activity was stable when sol-gel glasses were incubated at ambient temperature (pH 7.5) for several months. In comparison, trypsin, immobilized in sol-gel glass by surface adsorption and incubated under the same conditions overnight, was completely autodigested. The firm interaction between the protein molecules and the silica matrix stabilized the enzymes. Thus, the half-life of sol-gel-entrapped acid phosphatase at 70 degrees C (pH 8.0) was two orders of magnitude larger than that of the enzyme in solution. Transparent, mechanically and chemically stable bioactive sol-gel glasses may be used for the development of robust on-line biochemical photodetection sensors and for the purposes of chemical catalysis.

Acid Phosphatase↗
PubMed1992

The clinical use of glass-ionomer cements.

The use of glass-ionomer cements in clinical dentistry has expanded greatly over the last decade. Their use in treating early carious or erosion lesions has been investigated widely and established techniques include fissure filling, restoration of erosion lesions without cavity preparation, and the internal or tunnel restoration. Because of their adhesion to moist tooth structure, biologic compatibility, and fluoride release, increasing use also has been made of their anticariogenic properties in treating geriatric patients. Glass-ionomers have proved very successful as dentin substitutes for attaching composites to enamel without involving risk of pulpal damage in the deeper cavity. The deficiencies of glass-ionomer cements are well known, including lack of toughness, early water sensitivity, low abrasion resistance, and porosity, leading to poor surface polish. Solving these problems is formidable because inherently the strength of these cements is related to their water content. The clinician should be aware of these deficiencies and stay within the parameters of the techniques outlined in this article. In particular, clinical success depends on early protection of the cement from hydration or dehydration and the current use of light-cured bonding agents largely has solved this problem. The future probably lies in using laminate techniques in which materials that attach to dentin and form a biologic seal can be covered by tougher and harder enamel veneers, thus mimicking the structure of the tooth. It is possible that future materials will be developed on the lines of these polyelectrolyte cements in which higher molecular weight polymers are used in conjunction with polymers that contain photoinitiators to effect light curing and toughen the matrix. In addition, the possibility of developing laboratory-cured glass-ionomer inlays in which porosity can be reduced and tougher polymers used should be considered.

Dental Restoration, Permanent↗
PubMedDate not supplied

In vitro marginal leakage of cervical composite restorations lined with a light-cured glass ionomer.

The purpose of this research effort was to investigate the microleakage of cervical restorations lined with a light-cured glass-ionomer liner. Wedge-shaped cervical cavities were cut on extracted teeth with the gingival cavosurface margin involving dentin. The cavities were randomly assigned to each of each of three groups: (1) restored with a microfilled composite resin, (2) restored with a light-cured glass-ionomer liner and microfilled resin as in the "sandwich" technique, and (3) restored entirely with the light-cured glass-ionomer liner. Half of the specimens in each group were thermocycled. Microleakage of these restorations was assessed by dye penetration. The results showed that differences were more pronounced at the gingival margin. Composite restorations inserted over the glass-ionomer liner demonstrated significantly less leakage than when the liner was not used.

Composite Resins↗
PubMed2003

[Glass fiber polymerization--an effective method of increasing fracture resistance of the denture base (case reports)].

Three cases are presented to demonstrate how the application of glass fibres could be integrated into the treatment plan of removable dentures. In Case one the lack of space excluded the use of chrome-cobalt framework, but glass fibre reinforcement for the implant prothesis, secured by ball attachments, ensured structural stability. In Case two in order to keep the upper canine, an overdenture was constructed, which incorporated glass fibres in its dental base to prevent fracture propagation there. In Case three where the transfer of an extremely great chewing load to the dental base caused repeated fractures, the complex treatment of second framed work, fibres reinforcement and reline gave a stable satisfactory result over a long-term monitoring period. It was concluded, as presented, that the application of glass fibre reinforcement polymerised in the denture base can ensure structural stability and prevent fracture.

Dental Materials↗
PubMedDate not supplied

Effect of Nd:YAG laser irradiation on shear bond strength of glass-lonomer luting cement to dentin surface.

PURPOSE: The purposes of this study were to evaluate the shear bond strength of luting glass-ionomer cement to a dentin surface treated by pulsed Nd:YAG laser irradiation, and to prove the hypothesis that the bond strength of glass-ionomer luting cement to dentin is favorably altered after Nd:YAG laser irradiation. MATERIALS AND METHODS: Sixty-four extracted human molars with an exposed flat dentin surface were divided into four groups (n = 16). After painting black ink on their surfaces, the teeth of groups 1, 2, and 3 were irradiated by an Nd:YAG laser at 1.064-microm wavelength at 1, 2, and 3 W, respectively; group 4 was untreated and served as a control. Some specimens of each group were used for morphologic and atomic analytic study, and the others were used for shear bond testing. The shear bond test was performed after cylindric titanium specimens were cemented with glass-ionomer cement on a circular dentin area and specimens were immersed in distilled water. The tested specimens were also morphologically investigated. RESULTS: Shear bond strength of group 3 was significantly higher than that of the control group. Morphologic observation of the cement-dentin interface showed good adaptation of the luting cement to laser-treated dentin. Analysis of atomic contents on the dentin surface showed a significant increase of calcium:phosphorus ratio after laser irradiation. CONCLUSION: The dentin surface was modified morphologically and chemically, and the shear bond strength of glass-ionomer luting cement to dentin was increased by Nd:YAG laser irradiation at 3 W.

Aluminum Silicates↗
PubMed2003

The marginal seal of a flowable composite, an injectable resin modified glass ionomer and a compomer in primary molars--an in vitro study.

The present study was carried out to compare the marginal microleakage of some newer materials viz. a flowable composite, an injectable resin modified glass-ionomer and a compomer in Class I cavities of 30 non carious primary molars. After 0.5% basic fuchsin dye penetration and sectioning, the teeth were studied under stereomicroscope. The results obtained revealed that flowable composite showed significantly lower microleakage (p<0.05) as compared to injectable resin-modified glass ionomer and compomer. However, no significant difference was observed when injectable resin modified glass-ionomer cement was compared to compomer. This concludes that flowable composite materials adhere better to the primary teeth than resin modified glass ionomer and compomer.

Adhesiveness↗
PubMed1992

A novel sensitive assay for functional factor XII based on the generation of kallikrein-C1-inhibitor complexes in factor XII-deficient plasma by glass-bound factor XII.

We developed a very sensitive assay for functional factor XII. This assay is based on the property of glass-bound factor XII to activate prekallikrein (PK) into kallikrein in factor XII-deficient plasma, which is assessed by measuring the formation of kallikrein-C1-inhibitor complexes in this plasma by radioimmunoassay. Incubation of varying amounts of factor XII in glass tubes led to a dose-dependent increase in kallikrein-C1-inhibitor complexes in factor XII-deficient plasma with a lower limit of detection of +/- 20 pg of factor XII. The specificity of the assay for factor XII was demonstrated by experiments with plasmas deficient for factor XII, PK or high molecular weight kininogen (HK) and by incubation of factor XII with Polybrene or with a monoclonal antibody that inhibits the amidolytic and procoagulant activity of factor XII. The high sensitivity of the assay appeared to be due to the inability of C1-inhibitor to inhibit factor XII bound to glass, which resulted in a molar ratio of generated kallikrein to glass-bound factor XII of at least 100:1. This assay for factor XII may be a feasible tool in studies on structural and functional aspects of (recombinant) factor XII species synthesized by cultured cells.

Complement C1 Inactivator Proteins↗
PubMedDate not supplied

Effect of glass-fiber reinforcement and water storage on fracture toughness (KIC) of polymer-based provisional crown and FPD materials.

PURPOSE: The effect of glass-fiber reinforcement and water storage on the fracture toughness (KIC) of polymer-based provisional crown and fixed partial denture (FPD) materials was investigated. MATERIALS AND METHODS: Five unreinforced single-edged, notched control specimens and five test specimens reinforced with unidirectional E-glass fibers (Stick) were fabricated from three dimethacrylate-based provisional materials and one monomethacrylate-based provisional material. The specimens were stored in water at 37 degrees C for 1, 7, 30, or 60 days. Specimens were loaded in three-point bending at a cross-head speed of 0.1 mm/s. Mode I plane-strain KIC was calculated using the maximum load, and results of the two groups were compared. The water storage effect on KIC with time was also evaluated. RESULTS: The KIC of provisional materials reinforced with glass fibers (range 7.5 to 13.8 MNm(-1.5)) was significantly higher than that of unreinforced materials (range 1.3 to 3.1 MNm(-1.5)), by a factor of 4.4 to 5.5. A small, gradual decrease of KIC in reinforced specimens occurred with aqueous storage, but it was not statistically significant. CONCLUSION: The KIC of polymer-based provisional crown and FPD materials was significantly increased when they were reinforced with unidirectional E-glass fibers. Water storage for up to 2 months still left the reinforced materials with KIC values in excess of 7 MNm(-1.5). Hence, their performance was satisfactory.

Acrylic Resins↗
PubMedDate not supplied

A split-mouth randomized clinical trial of single crowns retained with resin-modified glass-ionomer and zinc phosphate luting cements.

PURPOSE: This study compared the influence of two luting cements on the clinical performance of single crowns. MATERIALS AND METHODS: Twenty patients received 39 pairs of metal-ceramic and Procera crowns cemented with zinc phosphate and resin-modified glass-ionomer luting cement (Vitremer) in a split-mouth randomized pattern blinded to the recipient. The crowns were examined immediately after cementation, after 2 weeks, after 6 months, and then yearly. Clinical performance was scored according to CDA criteria, Silness and Loe criteria, patient satisfaction, and operator-appraised general clinical criteria. Three clinicians in private general practice carried out all procedures. RESULTS: During the observation period, which varied between 80 and 104 months, seven clinical events were recorded. Two abutments fractured vertically, two underwent retrograde endodontic surgery, and one developed pulp necrosis. Two crowns were recemented. Estimated survival, defined as no negative events observed, was 89% at 102 months (85% for crowns cemented with zinc phosphate and 93% for crowns cemented with resin-modified glass-ionomer). Estimated survival, defined as no recementation or loss of pulp vitality, was 96% at 102 months (95% with zinc phosphate and 97% with resin-modified glass-ionomer). The differences between cements were not statistically significant. CONCLUSION: A resin-modified glass-ionomer luting cement was at least as good as zinc phosphate cement to retain single crowns over a 102-month observation period.

Cariostatic Agents↗
PubMed2004

Flexural properties of denture-base polymer reinforced with glass-fibre polysulphone composite.

The aim of this study was to determine the effect of glass-fibre composite reinforcement on the flexural strength and flexural modulus poly-methyl methacrylate (PMMA). Prefabricated electrical glass-fibre polysulphone composite rods (GF/PSu), 3mm in diameter, were incorporated in cylindrical, heat polymerizing PMMA specimens with diameters of 4, 5 and 6mm respectively (n = 10). These specimens were compared with PMMA control groups of similar dimension. A three point loading test was performed in air after storage of specimens in water at 37 degrees C for 8 weeks. The following variables were measured : Flexural Strength (FS) and Flexural Modulus (FM). The data were analyzed using one way analysis of variance (ANOVA). After testing, the fracture zone was evaluated using a scanning electron microscope (SEM). The glass-fibre reinforcement used in this study significantly enhanced both the FM and FS values of PMMA. This enhancement was, however, progressively reduced in relation to an increase in cross-sectional dimension of the specimens. SEM evaluation revealed delamination and fracture of the glass-fibres in the polymer matrix.

Adhesiveness↗