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Biomedical subjects

M Atsuta

Publications and source records attributed to M Atsuta.

At least 109 records · Page 6Linked to original sources
PubMed1997

Bonding of silver-palladium-copper-gold alloy with thiol derivative primers and tri-n-butylborane initiated luting agents.

This in vitro study elevated the effect of two primers on bond strengths and durability of luting agents joined to a silver-palladium-copper-gold alloy. One primer (Metal Primer) contained methacryloyloxyalkyl thiophosphate derivative (MEPS). The other primer (V-Primer) contained 6-(4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4-dithiol (VTD). The luting agent was a methyl methacrylate (MMA)-based adhesive resin that contained 4-methacryloyloxyethyl trimellitate anhydride (4-META) and was initiated with tri-n-butylborane derivative (TBB). In order to evaluate the function of 4-META, MMA-TBB resin without 4-META was used as a control. The alloy specimens were bonded with six combinations of two primers and two luting agents. Shear bond strengths were determined before and after thermocycling. Both primers significantly elevated the bond strengths of the luting agents joined to the alloy. For unprimed groups, 4-META resin showed a more durable bond than did MMA-TBB resin. Combined use of Metal Primer with 4-META resin reduced the bond strength, while combination of V-Primer and 4-META resin did not affect the bond strength.

Acrylic Resins↗
PubMed1997

Bonding of titanium with acidic primers and a tri-n-butylborane-initiated luting agent.

Adhesive bonding of titanium was investigated with the use of five primers and two luting agents. All of the primers contained acidic methacrylate monomers for promotion of metal bonding. Titanium metal specimens were bonded with seven combinations of five primers and two luting agents. Durability of the bond was evaluated by means of thermocycling. Although all five primers enhanced the bond strength to titanium, three of the primers (Super-Bond Liquid, Metal Primer and Tokuso Rebase MR. Bond) demonstrated more durable bonds than the other two primers (Acryl Bond and All-Bond 2 Primer B). The tri-n-butylborane (TBB)-initiated luting agent exhibited better bonding ability as compared to conventional composite resin. The strongest and the most consistent bond was achieved by the combination of 4-methacryloyloxyethyl trimellitate anhydride (4-META) primer and TBB resin.

Acids↗
PubMed1997

A metal halide light source for laboratory curing of prosthetic composite materials.

A high-intensity laboratory photo-curing unit has been developed with the aim of improving the post-curing properties of composite veneering materials. This study introduces the structure of the curing unit and examines the resulting properties of a representative composite material. The curing unit is equipped with two metal halide lamps that radiate both ultraviolet and visible light. Unlike conventional metal halide lamps for industrial use, these metal halide lamps radiate an increased intensity of visible radiation. Properties of a microfilled composite veneering material cured with the new metal halide unit were ascertained. A xenon photo-curing unit was also used as a control. The specimens cured with the metal halide unit exhibited greater Knoop hardness numbers and flexural moduli as compared with those cured with the xenon unit, and also showed reduced water solubility values. These results suggest that the metal halide light source is effective in curing composite materials within a shorter period of time and with improved conversion.

Analysis of Variance↗
PubMed1997

Effect of pressure difference on the quality of titanium casting.

In casting titanium using a two-compartment casting machine, Herø et al. (1993) reported that the pressure difference between the melting chamber and the mold chamber affected the soundness of the castings. This study tested the hypothesis that differences in pressure produce castings with various amounts of porosity and different mechanical properties values. Plastic dumbbell-shaped patterns were invested with an alumina-based, phosphate-bonded investment material. Both chambers of the casting machine were evacuated to 6 x 10(-2) torr; the argon pressure difference was then adjusted to either 50, 150, 300, or 450 torr. The porosity of the cast specimens was determined by x-ray radiography and quantitative image analysis. Tensile strength and elongation were measured by means of a universal testing machine at a strain rate of 1.7 x 10(-4)/s. The fractured surfaces were examined by SEM. Changes in Vickers hardness with depth from the cast surface were measured on polished cross-sections of the specimens. Raising the argon pressure difference to 300 and 450 torr caused a significant increase in internal porosity and a resultant decrease in the engineering tensile strength and elongation. The highest tensile strength (approximately 540 MPa), elongation (approximately 10%), bulk hardness (HV50g 209), and lowest porosity level (approximately 0.8%) occurred in the specimens cast at 150 torr. Turbulence of the metal during casting was thought to be responsible for the increase in porosity levels with the increase in argon pressure difference. By choosing an argon pressure difference (around 150 torr) suitable for this geometry, we could produce castings which have adequate mechanical properties and low porosity levels.

Analysis of Variance↗
PubMed1997

A coherent phase diagram of the [(AuCu)0.86Ag0.14]1-XPtX pseudobinary section in Au-Cu-Ag-Pt quaternary system.

In order to determine a coherent phase diagram of the [(AuCu)0.86Ag0.14]1-XPtX pseudobinary system, phase identifications and analyses of the microstructural configurations were performed by means of transmission electron microscopy. Various phase regions were detected in the coherent phase diagram as follows; (1) alpha 0 (fcc) single phase region, (2) two-phase region (alpha 1 + alpha 2), (3) AuCu I (L10) + alpha 0, (4) AuCu I + alpha 2, (5) AuCu II (L10-S) + alpha 2, (6) AuCu I + AuCu II + alpha 2, (7) AuCu I single phase region. Microstructural features of these regions relating to the phase transformations were described.

Chemical Phenomena↗
PubMed1996

Site restricted and neuron dominant expression of alpha 2,8sialyltransferase gene in the adult mouse brain and retina.

Gene expression of the alpha 2,8sialyltransferase (alpha 2,8S-T) responsible for GD3 synthesis in the adult mouse brain and retina was analysed by reverse transcription-polymerase chain reaction/Southern blotting (RT-PCR/Southern) and in situ hybridization. Among various portions of the brain, high levels of 9.5 kb mRNA were observed in the retina and midbrain. Results of RT-PCR/Southern did not necessarily correlate with the enzyme activities in the individual sites. In situ hybridization analysis revealed that this gene was characteristically expressed in the inner segment of photoreceptor cells, some nuclei in the midbrain, cranial nerve nuclei in the pons-medulla, Purkinje cells in the cerebellum, pyramidal cells of the hippocampus and granular cells of the dentate gyrus. In the retina, the alpha 2,8S-T gene was broadly expressed over the layers during development, and retained high expression levels in the photoreceptor cells of adult mice consistent with high expression of GD3. Destruction of neurons in the hippocampus and dentate gyrus by injection of kainic acid and colchicine respectively resulted in the disappearance of the hybridization signal, suggesting that the alpha 2,8S-T gene was mainly expressed by neurons.

Aging↗
PubMed1996

Bond strength and durability of porcelain bonding systems.

Because the most effective bonding system for ceramic restorations has not been documented, this study examined bond strength and durability of bonding systems joined to a feldspathic porcelain. Disks of porcelain specimens were fired on refractory investment materials and were air-abraded with alumina. The disks were then bonded with six combinations of five silane primers and six luting agents. Durability of the bond was evaluated by means of a thermocycling machine. Shear bond strengths were determined before and after thermocycling. The results showed that reduction in bond strengths after thermocycling was remarkable for five systems (p < 0.05). However, three systems exhibited shear bond strength greater than 20 MPa after 20,000 cycles.

Air↗
PubMed1996

Bonding of a cobalt-chromium alloy with acidic primers and tri-n-butylborane-initiated luting agents.

Limited information is available about chemical bonding of cobalt-chromium alloys for resin-retained fixed partial dentures. This study evaluated the effect of acidic primers on the bonding of luting agents joined to a cobalt-chromium alloy. Disk alloy specimens were bonded with eight combinations of five primers and two luting agents. Shear bond strengths were determined before and after thermocycling. The effect of priming on bond strength varied among the combinations of primer and luting agent. In particular, after thermocycling three groups demonstrated greater bond strengths than the other groups did. These were (1) specimens treated with a phosphate-methacrylate primer (Cesead Opaque Primer), (2) specimens bonded with an adhesive resin (Super-Bond Opaque), or (3) a combination of both.

Acrylic Resins↗
PubMed1996

Shear bond strengths of three resin cements used with three adhesive primers for metal.

This study compared the durability and shear bond strengths of combinations of three adhesive primers and three resin cements bonded to silver-palladium-copper-gold (Ag-Pd-Cu-Au) and cobalt-chromium (Co-Cr) alloys. The adhesive luting cements Imperva Dual, Panavia 21, and Super-Bond C&B and the adhesive primers Metal Primer material, V-Primer material, and Cesead Opaque Primer material were used. The application of Metal Primer material was effective in improving the shear bond strengths between each of the three resin cements and Ag-Pd-Cu-Au alloy compared with nonprimed specimens. Co-Cr alloy primed with Cesead Opaque Primer, followed by cementation with Imperva Dual or Super-Bond C&B luting cements yielded the strongest shear bond strengths after 50,000 thermocycles, and Panavia 21 cement did not reveal any significant differences in bond strengths between nonprimed specimens and those primed with Cesead Opaque Primer at all thermocycles.

Adhesives↗
PubMed1996

Effect of ultrasonic instrumentation on bond strength of three dental cements bonded to nickel-chromium alloy.

This study examined the effect of ultrasonic instrumentation on the bond strength of three types of luting material joined to a nickel-chromium alloy. Disk metal specimens were bonded together with zinc phosphate, glass ionomer, and adhesive resin luting agents. The bonded specimens were immersed in water, then vibrated with an ultrasonic unit for 0 to 5 minutes. The shear bond strength in the 0 or nonvibrated group was 50.1 MPa for adhesive resin, 18.4 MPa for glass ionomer, and 4.7 MPa for zinc phosphate cement. Vibration for a period of 5 minutes significantly diminished the bond strength of adhesive resin and glass ionomer materials, whereas the bond strength of zinc phosphate cement was affected after only 1 minute.

Acrylic Resins↗
PubMed1996

Heterogeneity in the expression pattern of two ganglioside synthase genes during mouse brain development.

Gangliosides are synthesized by sequential catalytic reaction of multiple glycosyltransferases. GM2/GD2 synthase and GD3 synthase are key enzymes for ganglioside synthesis, because their relative activities regulate the main profiles of ganglioside expression. Mouse GD3 synthase (EC 2.4.99.8) cDNA was cloned by eukaryotic expression cloning, and its mRNA expression as well as that of GM2/GD2 synthase gene during the development of the mouse CNS was analyzed by using northern blotting, reverse transcription-polymerase chain reaction, and in situ hybridization. When brain tissue was analyzed as a whole mass, a typical pattern corresponding to the reported findings obtained by biochemical analyses was observed, i.e., high expression of GD3 synthase gene in the early stage and gradual increase of GM2/GD2 synthase gene expression in the late stage of the development. However, the results of in situ hybridization of these two genes revealed that the expression kinetics of these two genes were heterogeneous among various sites in the brain under development. These findings suggest that various expression patterns of the two genes reflect differences in the course of the development of individual sites, and also different ganglioside components are required in individual portions of the brain for development and maintenance of the function.

Amino Acid Sequence↗
PubMed1996

Bonding of a mica-based castable ceramic material with a tri-n-butylborane-initiated adhesive resin.

Adhesive bonding of a mica-based castable ceramic material (Olympus Castable Ceramics, OCC) was evaluated in vitro with the use of a silane primer in conjunction with an adhesive luting material. The primer contained a silane coupler and 4-methacryloxyethyl trimellitate anhydride (4-META), while the methyl methacrylate (MMA)-based luting agent was initiated with a tri-n-butylborane derivative (TBB) and contained 4-META (4-META/MMA-TBB resin). Ceramic specimens were sanded with No. 600 silicon carbide paper followed by blasting with alumina and/or etching with ammonium bifluoride. The specimens were bonded with various combinations and shear bond strengths were determined. Both priming and alumina blasting enhanced the bond between 4-META resin and OCC. Although etching with ammonium bifluoride roughened the ceramic surface, this procedure did not improve the bond strength. Electron probe microanalysis of the ceramic surface revealed a decrease in silicon and aluminium elements after etching with ammonium bifluoride.

Acid Etching, Dental↗
PubMed1996

Adhesive bonding to dentin with ferrous chloride primers and tri-n-butylborane-initiated luting agents.

A variety of surface modifications with metal chlorides has been used to enhance the bond of resins to dentin. This study investigated the effectiveness of ferrous chloride in terms of the initiation of polymerization in dentin bonding. The efficacy of experimental dentin primers was evaluated via the bonding of two luting agents to dentin. The 16 primers evaluated were ferrous chloride (FeCl2) aqueous solutions, eight with and eight without 35% 2-hydroxyethyl methacrylate (HEMA). The concentrations of FeCl2 in the primers ranged from 2.0 x 10(-6) to 5.0 x 10(-4) mol/g. One luting agent (Super-Bond C&B) consisted of methyl methacrylate (MMA), 4-methacryloyloxyethyl trimellitate anhydride (4-META), and tri-n-butylborane (TBB) initiator. The other luting agent was prepared with MMA and TBB, but without 4-META. Bovine dentin surfaces were flattened, etched with an aqueous solution of 10% phosphoric acid, primed, and then bonded with stainless steel rods. Tensile strengths of the bonded specimens were measured after one-day immersion in water. Tensile testing revealed that the bond strength was influenced by the application of FeCl2 and/or HEMA. The maximum bond strength of 33.0 MPa was recorded with the use of primer containing FeCl2 and HEMA in MMA-TBB resin. In the case of Super-Bond, only surface treatment of dentin with aqueous primers containing 5.0 x 10(-5) to 2.0 x 10(-4) mol/g ferrous chloride resulted in bond strength values above 22.0 MPa. This bonding technique, combining the use of ferrous chloride primer with Super-Bond resin, may potentially be applied for seating resin-bonded restorations.

Analysis of Variance↗
PubMed1995

Effect of two metal primers on adhesive bonding with type IV gold alloys.

Bond strengths of an adhesive resin bonded to two types of gold alloys were investigated in vitro with two different metal primers. Disk specimens were cast in a type IV gold alloy designed for resin-bonded restorations and in a low-temperature age-hardenable gold alloy. The specimens were primed with either a vinyl-thiol primer or a thiophosphate primer, then bonded with an adhesive resin initiated with tri-n-butyl borane derivative. Both primers effectively enhanced bond between gold alloys and the adhesive. The use of metal primers in conjunction with type IV gold alloys is useful for resin-bonded fixed partial dentures.

Acrylic Resins↗
PubMed1995

Effect of unfilled resins and a silane primer on bonding between layers of a light-activated composite resin veneering material.

This investigation evaluated the effect of unfilled resins and a silane primer on bonding between layers of a urethane-based composite resin veneering material. Shear bond strengths between the layers were determined with a two-liquid silane primer and three unfilled resin bonding agents. The silane primers and unfilled resins enhanced the bond between layers of the veneering material. Durability of the bond, however, was influenced by the composition of the bonding agent. Among the systems investigated, combined use of the silane primer with triethyleneglycol dimethacrylate-based unfilled resin exhibited durable and consistent bond strength.

Analysis of Variance↗
PubMed1995

A comparison of water temperatures for thermocycling of metal-bonded resin specimens.

The thermocycling test to evaluate the bonding durability of the adhesive interface against water penetration and thermal stress is one of the most important studies before clinical application of metal-bonded resin systems is performed. Researchers have adopted various water temperatures for thermocycling adhesion specimens, which makes a direct comparison with thermocycling data attained by other researchers difficult. In this study tensile and shear bond strengths of metal-bonded resin specimens were measured after 20,000 thermocycles with the temperatures of the hot bath at 50 degrees C, 60 degrees C, and 70 degrees C. The results indicated that adhesive bonding strengths attained after thermocycling at 50 degrees C may be nearly comparable with those at 60 degrees C.

Analysis of Variance↗
PubMed1995

Diverse expression of beta 1,4-N-acetylgalactosaminyltransferase gene in the adult mouse brain.

Among various tissues of mouse, beta 1,4-N-acetylgalactosaminyltransferase (GM2/GD2 synthase) gene is expressed predominantly in the brain. Further analysis of the gene expression in the mouse CNS was performed by northern blotting and by enzyme assays using extracts from various parts of the CNS. In situ hybridization was also done to investigate the distribution of cells generating GM2/GD2 synthase. In northern blots, diverse levels of the gene expression were observed, depending on the regions examined. By in situ hybridization, pyramidal cells in the hippocampus, granular cells in dentate gyrus and cerebral cortex, Purkinje cells in cerebellum, and mitral cells in the olfactory bulb expressed high levels of the mRNA; these results corresponded to the results obtained by northern blot. Enzyme levels in these sites were accordingly high. However, enzyme levels in certain areas with low mRNA intensities, such as thalamus and pons medulla, were higher than expected from the results of northern blotting. The significance of the high gene expression in certain areas for brain function and the reason for the discrepancy between mRNA level and enzyme activity in some regions are discussed.

Animals↗