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PubMed2005

Microleakage on Class V glass ionomer restorations after cavity preparation with aluminum oxide air abrasion.

This in vitro study assessed the marginal microleakage on class V cavities prepared with aluminum oxide air abrasion and restored with different glass ionomer cements. The cavities were prepared on the buccal and lingual surfaces of 15 sound third molars with an air- abrasion device (Kreativ Mach 4.1; New Image) using a 27.5-microm aluminum oxide particle stream, and were assigned to 3 groups of 10 cavities each. The restorative materials were: group I, a conventional glass ionomer cement (Ketac-Fil); groups II and III, resin-modified glass ionomer cements (Vitremer R and Fuji II LC, respectively). After placement of the restorations, the teeth were stored in distilled water at 37 degrees C for 24 h, polished and then submitted to a thermocycling regimen of 500 cycles, isolated, immersed in 0.2% Rhodamine B solution for 24 h, included and serially sectioned. Microleakage was assessed by viewing the specimens under an optical microscope connected to a color video camera and a computer. The images obtained were digitized and analyzed for microleakage using software that allows for a standard quantitative assessment of dye penetration in millimeters. Statistical analysis was done using the Kruskall-Wallis and Wilcoxon tests. Means of dye penetration (%) were: occlusal - I: 25.76 +/- 34.35, II: 20.00 +/- 42.16, III: 28.25 +/- 41.67; cervical - I: 23.72 +/- 41.84; II: 44.22 +/- 49.69, III: 39.27 +/- 50.74. No statistically significant differences (p>0.05) were observed among either the glass ionomer cements or the margins. In conclusion, class V cavities restored with either conventional or resin-modified glass ionomer cements after preparation with aluminum oxide air abrasion did not show complete sealing at the enamel and dentin/cementum margins.

Air Abrasion, Dental↗
PubMedDate not supplied

Retention of oral microorganisms on conventional and resin-modified glass-ionomer cements.

Secondary caries are a worldwide public and socioeconomic problem. The placement of restorations can lead to the development of environmental conditions favorable to microbial colonization, especially on the tooth/restoration interface, which is a predisposing factor for secondary caries. The aim of this study was to evaluate microbial retention on conventional (Chelon-Fil and Vidrion R) and resin-modified (Vitremer and Fuji II LC) glass-ionomer cements, in situ, using a hybrid composite resin (Z100) as a control. Twelve volunteers wore Hawley appliances with specimens made of all tested filling materials for 7 days. The specimens were then removed from the appliances and transferred to tubes containing 2.0 ml of Ringer-PRAS. Microorganisms from the samples were inoculated onto blood agar and Mitis Salivarius Bacitracin agar and incubated under anaerobiosis (90% N2, 10% CO2), at 37 degrees C, for 10 and 2 days, respectively. The resin-modified glass-ionomer cements and the composite resin retained the same levels of microorganisms on their surfaces. The resin-modified glass-ionomers retained less mutans streptococci than the composite resin and conventional glass-ionomer cements. The conventional glass-ionomer cements retained less mutans streptococci than the composite resin, but that difference was not statistically significant.

Adult↗
PubMed2001

Wear of resin-modified glass ionomers: an in vitro study.

The purpose of this study was to evaluate the wear resistance and clinical applicability of resin-modified glass ionomer cements as restorative or fissure-sealing materials. The in vitro wear of resin-modified glass ionomers was compared to conventional glass ionomers, a resin-based sealant, and a composite resin. A three-body wear test (enamel block--polymethylmethacrylate powder--experimental dental material) was performed by 20,000 cycles with a load of 4 kgf/cm2. The depth of wear of the experimental materials was measured and calculated using a computerized laser surface scanner. The glass ionomers generally showed more wear than the resin-based sealant and the composite resin, but there was no difference in wear between resin-modified and conventional glass ionomers. Type III ionomers (used for sealant) showed lower wear resistance than type II ionomers (used for restoration).

Bisphenol A-Glycidyl Methacrylate↗
PubMed2000

Effects of nicotine on the strength of attachment of gingival fibroblasts to glass and non-diseased human root surfaces.

BACKGROUND: The aim of this study was to evaluate the effect of nicotine on the strength of attachment of human gingival fibroblast cells to glass and non-diseased human root surfaces. METHODS: Human gingival fibroblast cells (HGF) were trypsinized, suspended in RPMI 1640 medium, and incubated with autoclaved human root and glass sections and nicotine (NIC) concentrations of 0 (control), 25, 50, and 100 ng/ml for 1 week. HGF attached and grew on glass and root surfaces for 4 weeks at all NIC concentrations. HGF cultures were subjected to a rotary shaker machine for 30 minutes to test the strength of attachment of these cells at 100, 150, and 200 rpm. The root and glass sections were examined at 48 hours by light microscopy. RESULTS: Control groups exhibited a monolayer of long, spindle-shaped fibroblasts with a parallel alignment and minimal overlapping. With a concentration of NIC of 50 or 100 ng/ml as well as with increasing "speeds," the number of cells attached to these surfaces decreased dramatically. When 200 rpm was used for both groups at all NIC concentrations, very few HGF remained attached to these surfaces. CONCLUSIONS: This study showed that the nature of cell attachment to either glass or root surfaces is altered by nicotine, and marked detachment was noted when nicotine exposure was coupled with vigorous agitation at different rpm. Marked detachment noted in all specimens at 200 rpm indicates that this speed is excessive for use in subsequent experimentation.

Cell Adhesion↗
PubMed1980

General properties of antimony microelectrode in comparison with glass microelectrode for pH measurement.

Two kinds of pH-sensitive microelectrodes were constructed: 1) glass microelectrode with a pH-sensitive tip of 50--100 micrometers in length, and 2) antimony (Sb) microelectrode with a tip of 1--5 micrometers in outside diameter. Comparisons of the two were made on the change in the electromotive force (EMF) in response to various pHs and biological applicability. The pH sensitivity (slope constant) at 20 degrees C of the glass and Sb-microelectrodes averaged 51.7 and 51.9 (-mV/pH), respectively. Over the pH range of 2 to 9, both electrodes responded linearly to the change of pH. The pH-dependent EMF of the Sb-microelectrode was influenced by phosphate buffers, but not by Tris-HCl buffers. Through the glass microelectrode showed a linear response to all the buffers tested, its slope constant tended to be limited by the surface area of the pH-sensitive tip. The stability of the EMFs was well within 1 mV for 12 hr with the glass microelectrode but more than 10 mV with the Sb-microelectrode. One the other hand, the 95% response time was about 1 min with the glass microelectrode, whereas it was less than a few seconds with the Sb-microelectrode. Blood pH was measured with the two electrodes and reasonable values were obtained with both methods, although the values by use of the Sb-microelectrode were slightly higher than those of the other. In view of the practical ease of manufacturing, maintenance and durability, the use of the Sb-microelectrode in biological measurement should also be re-evaluated, but several restrictions must be imposed on it.

Animals↗
PubMed2001

Quantification of ground-glass opacity on high-resolution CT of small peripheral adenocarcinoma of the lung: pathologic and prognostic implications.

OBJECTIVE: The purpose of our study was to correlate the high-resolution CT findings of small peripheral adenocarcinoma of the lung with underlying histopathology and to evaluate the prognostic implications of the CT findings. MATERIALS AND METHODS: The high-resolution CT findings of small peripheral adenocarcinoma of the lung in 224 patients were analyzed by two independent observers for location, size, marginal characteristics, and extent of ground-glass opacity and necrosis. The pathologic specimens were reviewed by an experienced lung pathologist. RESULTS: One hundred and thirty-two patients had bronchioloalveolar carcinoma and 92 had adenocarcinoma. The extent of ground-glass opacity was greater in bronchioloalveolar carcinomas (mean +/- SD, 29% +/- 31.6%) than in other adenocarcinomas (8% +/- 13.3%) (p < 0.001). The extent of ground-glass opacity was significantly greater in patients without recurrence (p = 0.020) and those without nodal (p = 0.017) or distant (p = 0.007) metastases than in patients with nodal or distant metastases or in whom the carcinoma had recurred. CONCLUSION: The extent of ground-glass opacity in a nodule is greater in bronchioloalveolar carcinomas than in other adenocarcinomas. Greater extent of ground-glass opacity also correlates with improved prognosis.

Adenocarcinoma↗
PubMed1997

Characterization of 50wt%SiO2-20wt%P2O5-30wt%CaO glass-ceramic powders prepared by the sol-gel process.

Glass-ceramic powders with the oxide batch formulation 50wt%SiO2, 20wt%P2O5 and 30wt%CaO were prepared by the sol-gel process using tetraethoxysilane, calcium nitrate and phosphoric acid as raw materials. The obtained gels and powders were characterized by TG-DTA thermal analysis, FTIR analyses and XRD measurements. The results indicated that (1) heating to more than 600 degrees C brought about elimination of -OC2H5 side chains from gels, and formation of a SiO2-based glass network, (2) crystallization such as Ca3(PO4)2 notably occurred in the SiO2-based glass matrix when heated to more than 900 degrees C, (3) -OH groups existed on SiO2-based glass-ceramic surfaces in the temperature region less than 900 degrees C, and (4) the melting point of this composition was more than 1400 degrees C. This study suggests that sol-gel-derived SiO2-based glass-ceramic powder containing P and Ca might be useful as bioactive implant materials.

Calcium Compounds↗
PubMed2002

Relaxation modulus of denture base resin reinforced with woven glass fibers.

This study examined the reinforcing effect of woven glass fibers on the relaxation modulus by three-point loading of denture base resin. Three sandwich-type flexure test specimens polymerized by heating were used, all 3 mm thick: glass fibers in compression (U type); glass fibers in the center (C type); and glass fibers in tension (L type). Unreinforced specimens (ACR) were produced as a control. The relaxation modulus after 8 sec from the start of stress (Er(8)) was calculated from stress relaxation curves. In the glassy state, the Er(8)s of the U and L types were greater than those of the ACR and C types. In the rubbery state (plateau region), the Er(8)s of the U and L types were greater than those of the ACR and C types. The woven glass fibers added to the U and L type specimens increased the relaxation modulus of PMMA near the oral temperature; moreover, they inhibited stress relaxation when the temperature increased.

Algorithms↗
PubMed2003

Impact strength of acrylic denture base resin reinforced with woven glass fiber.

This study investigated the effect of the number and position of woven glass fibers in denture base resin matrix on its impact strength. Test specimens were reinforced with woven glass fiber 0.5, 1.0, or 1.5 mm below the surface. The impact strength was tested using an Izod-type impact tester with an impact speed of 335 cm/s, which simulates dropping the denture, and using a flywheel-type impact tester with a two-point support at 13.5 and 75.0 cm/s, which simulates the chewing. The woven glass fibers had a strengthening effect in all tests, and the impact resistance was further improved when the woven glass fibers were positioned more superficially in the resin. The results suggest that woven glass fiber is an effective reinforcement in denture base resin.

Analysis of Variance↗
PubMed2003

Color change in acrylic denture base resin reinforced with wire mesh and glass cloth.

In this study, the L*a*b* color system as a color system and light transmittance of the denture base resin reinforced with wire mesh and glass cloth were measured, and the color difference (deltaE*ab) was calculated using L*, a* and b* values which were measured both on a white calibration plate and on a null background. The thicknesses of test specimens, which were reinforced with wire mesh and glass cloth 0.5 and 1.0 mm below the surface, were 3 and 5 mm. L*, a* and b* values of wire mesh reinforcing specimens decreased in comparison with the non-reinforcing specimens (p<0.05). L* values of glass cloth-reinforcing specimens increased compared with the non-reinforcing specimens (p<0.05). The glass cloth is an effective reinforcing material and an aesthetically important property of denture base resin, since wire mesh makes the resin appear darker with the background condition greatly altering the color, while glass cloth makes the resin lighter.

Acrylic Resins↗
PubMed2005

Pulpal response to a hybrid composite resin inlay bonded with a newly developed resin-modified glass ionomer luting cement.

This study evaluated the pulpal response of hybrid composite resin inlay luted with a resin-modified glass ionomer cement, and compared it with a glass ionomer cement and an amalgam. Cervical cavities were prepared in monkey teeth. A resin-modified glass ionomer luting cement (Ionotite F, Tokuyama Dental Corp.) was applied to the teeth in one of the experimental groups, and then hybrid composite resin inlays (Estenia, Kuraray Medical Inc.) were bonded to the cavities. The teeth were extracted after 3, 30, and 90 days and stained with Hematoxylin and Eosin staining or Brown and Brenn gram stain for bacterial observation. No serious inflammatory reaction of the pulp, such as necrosis or abscess formation, was observed in any of the experimental groups. No bacterial penetration along the cavity walls was detected in the resin-modified glass ionomer luting cement group. Hence, the resin-modified glass ionomer luting cement showed an acceptable biological compatibility with monkey pulp.

Analysis of Variance↗
PubMed2006

Effect of mica and glass on acrylic teeth material's color.

The purpose of this study was to evaluate the effect of two different ratios of silanized mica filler and milled glass fiber reinforcement on the color of acrylic denture teeth materials. Ten acrylic resin discs made of acrylic denture teeth material (PMMA) obtained from the manufacturer were used as the control group. Four experimental groups were modified from the control group's PMMA material by adding a ratio of 5% or 10% by weight of silane-treated mica filler or milled glass fibers. Each group consisted of 10 specimens. Measurements were performed using a spectrophotometer CM-2600d, and the color changes were characterized in the Commission Internationale d'Eclairage L*a*b* color space. deltaE* values of 5% mica-, 10% mica-, 5% glass-, and 10% glass-containing sample groups were 2.46, 3.03, 2.16, and 2.59 respectively. There were statistically significant differences in L*, a*, and b* values between the control group and each test group. It was shown that when PMMA denture teeth material was modified with silane-treated mica filler or silane-treated milled glass fibers for the purpose of reinforcement, it would also cause significant changes to the original color of the material.

Acrylic Resins↗
PubMed2004

Thermal inactivation of Listeria innocua in salmon (Oncorhynchus keta) caviar using conventional glass and novel aluminum thermal-death-time tubes.

Differences in the come-up times and thermal inactivation parameters of Listeria innocua in salmon (Oncorhynchus keta) caviar containing 2.5% salt using conventional thermal-death-time (TDT) glass tubes and a novel aluminum tube were tested and compared. Generally, the come-up times and decimal reduction times (D-values) were shorter and the change in temperature required to change the D-value (z-value) was longer in the aluminum than in the glass tubes. The D-values at 60, 63, and 65 degrees C for the aluminum TDT tubes were 2.97, 0.77, and 0.40 min, respectively, and for the glass TDT tubes, these values were 3.55, 0.84, and 0.41 min. The z-values were 5.7 degrees C in the aluminum and 5.3 degrees C in the glass. Because of the shorter come-up time, the aluminum TDT tubes may provide a more precise measurement of microbial thermal inactivation than the glass TDT tubes, particularly for viscous materials, solid foods, and foods containing particulate matter.

Aluminum↗
PubMedDate not supplied

Fracture strength of glass infiltrated-magnesia core porcelain.

PURPOSE: This study determined the fracture strength of magnesia-core porcelain after using a glass infiltration firing technique. MATERIALS AND METHODS: Eighty refractory dies were replicated from a stainless steel master die milled to the dimensions of a maxillary premolar that had been prepared for a porcelain crown. The core porcelain was applied to the refractory dies using traditional condensation methods, and then formed into standardized copings using a centrifugal sculpturing device. The copings were vacuum-fired from 593 degrees C to 1 of 8 high temperatures. Five copings per temperature were then coated with a glass-infiltrate and ground back to a standard thickness. The finished copings were bonded to a duplicate die with an adhesive resin luting system and placed in an Instron testing machine and loaded to fracture. RESULTS: Analysis of variance and Student-Newman-Keuls tests demonstrated significant differences among treatments and temperatures (P < 0.05). A significant increase in fracture strength was observed after glass infiltration of the magnesia-core porcelain. Sintering the copings to 871 degrees C or 899 degrees C prior to glass infiltration gave the highest fracture load values. CONCLUSION: Glass infiltration significantly increased the fracture strength of the magnesia-core porcelain.

Analysis of Variance↗
PubMedDate not supplied

Adherence of Candida albicans to the surface of polymethylmethacrylate--E glass fiber composite used in dentures.

PURPOSE: The use of reinforcing fibers in dentures has raised concerns about possible increased adherence of yeasts to the surface. The aim of this in vitro study was to compare the adherence of Candida albicans to the surface of denture-base polymer and to E-glass fibers. MATERIALS AND METHODS: Test specimens were made from an autopolymerized denture-base resin (Palapress) reinforced with preimpregnated unidirectional E-glass fibers, which were exposed at the surface. The test specimens were pretreated with parotid saliva and incubated without agitation in standardized yeast suspensions (10(8) colony-forming units per mL) in phosphate-buffered saline at 37 degrees C for 1 hour. The test specimens were then washed to remove nonadherent cells. After being air dried, they were sputter coated with gold-palladium for scanning electron microscopy (SEM). To compare the adherence to different surfaces, the number of yeast cells found either on the polymer matrix or on the glass fibers was counted from SEM fields (170 microns x 120 microns, 600 x) of randomly selected areas. RESULTS: The mean density of yeast cell found on the surface of the polymer matrix was significantly higher (P < 0.001) than that on the surface of glass fibers. The number of adherent yeast cells found at the interface between the fibers and polymer matrix was high. CONCLUSION: The adherence of C albicans to E-glass fibers was lower than to polymer matrix in the denture composite. If fibers are exposed only during polishing of the composite, the reinforcing material appears not to increase the adherence of this common oral yeast. However, areas with permanently exposed fibers may provide mechanical retention for yeast cells at the interface of the components.

Acrylic Resins↗
PubMed1998

[Research on bending strength and fracture toughness of alumina-glass composite].

To develop a new ceramic material that can be machined and infiltrated with glass, a porous alumina blank sintered at 1350 degrees C was made of high purity, super fine alpha-alumina and then infiltrated with glass in this study. The density, bending strength and fracture toughness of the partially sintered alumina and alumina-glass composite were determined. The results indicated that the porous alumina density was 2.12 g/cm3, the three point bending strength 102 MPa, the fracture toughness 1.61 MPam1/2; that the alumina-glass composite density was 3.85 g/cm3, the three point bending strength 385 MPa, and the fracture toughness 4.05 MPam1/2. By SEM and EDXA analysis, lanthanum boroslicate glass was completely infiltrated into the 3 mm thick porous alumina blank for 6 h at 1150 degrees C. These suggest that the new developed alumina blank is suited for clinical use.

Aluminum Oxide↗
PubMed1999

Evaluation of esthetic parameters of resin-modified glass-ionomer materials and a polyacid-modified resin composite in Class V cervical lesions.

OBJECTIVE: The purpose of this study was to compare the esthetics of 3 resin-modified glass-ionomer materials and 1 polyacid-modified resin composite to the esthetics of a conventional glass-ionomer control material. METHOD AND MATERIALS: One hundred eighty-seven Class V cervical restorations were observed clinically over 18 months. The esthetic index system that was used evaluated color match, translucency or opacity, and surface roughness. RESULTS: The tested materials behaved very dissimilarly and inconsistently. In general, the esthetic results of the resin-modified glass-ionomer materials and the polyacid-modified resin composite were far from optimal. The esthetic appearance of restorations seriously deteriorated during clinical service, mainly because of discoloration of margins, changes in translucency and opacity, and rapidly appearing roughness or dullness on the surface. Both the resin-modified glass-ionomer materials and the polyacid-modified resin composite evaluated in this study performed better esthetically than did the conventional glass-ionomer material. CONCLUSION: Indications for these combination materials are limited to areas where esthetics is not a primary concern but where their ease of application may guarantee a more durable functional result.

Acrylic Resins↗
PubMedDate not supplied

Comparative quantitative and qualitative assessment of the marginal adaptation and apposition of bonded amalgam restorations using luting glass ionomer and 4-META adhesive liner under a scanning electron microscope. An in vitro study.

The present invitro study was conducted to assess the marginal adaptation and apposition of amalgam restorations bonded to tooth structure, using freshly mixed luting glass ionomer cement (type 1) and compared with the much documented material--Amalgam bond (4-META). Twelve freshly extracted human premolar teeth were used and class V cavities were prepared on the buccal and lingual surfaces of twelve teeth for the experimental groups. Buccal cavities (class V) were prepared on twelve other teeth for the control group. In the control, two coats of cavity varnish was applied as the liner. The experimental groups were lined with freshly mixed luting glass ionomer in twelve buccal cavities and amalgam bond adhesive liner in twelve lingual cavities. The amalgam was then condensed before the liner sets in all the cavities. The teeth were sectioned and mounted on aluminum stubs and then placed in the scanning electron microscope and were observed. The results of the study showed that marginal interface gaps were higher with luting glass ionomer and cavity varnish than with amalgam bond as the liner. The results were statistically not significant. All the three groups were effected by the severe thermal stresses introduced by the microscopy with the glass ionomer cement suffering the worst. The present investigation confirms that glass ionomer cement (type 1) can be effectively used as a bonding agent between amalgam and the tooth when it is painted onto the cavity walls after which the amalgam is condensed immediately, prior to its setting. Its ability to bond amalgam to the tooth structure with minimal gaps is comparable to that of amalgam bond.

Acrylic Resins↗