Hideo Ogura

The Nippon Dental University, Tokyo, Tokyo-to, Japan

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Publications (37)31.76 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This study aimed to evaluate the effect of EDTA solutions (3% and 10% EDTA•2Na) on corrosion fatigue of three Ni-Ti files with different shapes, in comparison with other solutions (6% NaClO, 3% H2O2, 0.9% NaCl and distilled water). Ni-Ti files were subjected to rotational bending in a bent glass tube (30° and 60° angles) filled with the solutions, and the number of rotations to failure was counted. At 30° bent angle, files in the two EDTA solutions showed significantly lower resistance than those in distilled water, but no significant difference was found between the two EDTA solutions. Fatigue resistance of two tested files in the two EDTA solutions was not significantly different from those in the other three solutions, whereas one file in EDTA solutions showed significantly lower resistance than that in 3% H2O2. At 60° bent angle, early failure within 1-2.5 min was observed for all tested files, and no significant difference was found among the six solutions. At both angles, significant differences in fatigue resistance were observed among the three tested files, which could be related to the difference in the cross-sectional shapes of the files.
    Dental Materials Journal 04/2014; · 0.81 Impact Factor
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    ABSTRACT: To investigate the effects of different fillers and their contents on the wear of composite resins, four composites (CS: non-porous spherical silica, AS: porous spherical silica, AZ: porous spherical zirconium silicate, and IS: non-porous irregular-shaped silica) were experimentally prepared using different fillers (CS, AZ, AS and IS). Simulated occlusal wear and toothbrush wear were evaluated for these composites and their worn surfaces were observed. The mechanical properties (flexural strength, elastic modulus and hardness) of these composites were determined to examine the relationships between wear and these mechanical properties. CS showed the highest occlusal wear, but the lowest toothbrush wear among four composites. AS and AZ had lower occlusal wear than CS and IS, while their toothbrush wear was higher than CS and close to that of IS. All composites showed increase in the occlusal wear as filler content increased. CS and IS showed decrease in the toothbrush wear as the filler content increased, whereas AS and AZ did not. The occlusal wear surfaces of CS and IS had concavities, while those of AZ and AS were relatively smooth with flattened filler. The toothbrush wear surfaces of CS and IS revealed the extrusion of filler from resin matrix, whereas those of AZ and AS were smooth with flattened filler. The toothbrush wear of CS and IS decreased as the mechanical properties increased, whereas those of AS and AZ did not. The occlusal wear of all composites increased as the mechanical properties increased, which would not reflect effects of these mechanical properties.
    Odontology 07/2012; · 1.58 Impact Factor
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    ABSTRACT: The purpose of this study was to investigate the relation between the texture of worn surfaces of composite resins and the maximum wear depth. Three types of composite resins were investigated: a hybrid composite resin consisting of irregular-shaped inorganic filler particles (APX); a composite resin which contained small, irregular-shaped, inorganic filler particles and large organic composite filler particles (SRE); and another which contained spherical inorganic filler particles and large organic composite filler (SDX). Surface profile measurement and elemental analysis were carried out on the worn surfaces of these three composite resins using an electron probe microanalyzer (EPMA). For the composite resin which exhibited the largest maximum wear depth, its surface texture was slightly rough with fine pores and grooves. For the composite resin with lowest maximum wear depth, it had a smooth worn surface due to the large organic composite filler being abraded during the combined wear test.
    Dental Materials Journal 02/2012; 31(1):61-7. · 0.81 Impact Factor
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    ABSTRACT: When adipose-derived stem cells (ASCs) are retrieved from the stromal vascular portion of adipose tissue, a large amount of mature adipocytes are often discarded. However, by modified ceiling culture technique based on their buoyancy, mature adipocytes can be easily isolated from the adipose cell suspension and dedifferentiated into lipid-free fibroblast-like cells, named dedifferentiated fat (DFAT) cells. DFAT cells re-establish active proliferation ability and undertake multipotent capacities. Compared with ASCs and other adult stem cells, DFAT cells showed unique advantages in their abundance, isolation and homogeneity. In this concise review, the establishment and culture methods of DFAT cells are introduced and the current profiles of their cellular nature are summarized. Under proper induction culture in vitro or environment in vivo, DFAT cells could demonstrate adipogenic, osteogenic, chondrogenic and myogenic potentials. In angiogenic conditions, DFAT cells could exhibit perivascular characteristics and elicit neovascularization. Our preliminary findings also suggested the pericyte phenotype underlying such cell lineage, which supported a novel interpretation about the common origin of mesenchymal stem cells and tissue-specific stem cells within blood vessel walls. Current research on DFAT cells indicated that this alternative source of adult multipotent cells has great potential in tissue engineering and regenerative medicine.
    International Journal of Oral Science 07/2011; 3(3):117-24. · 2.72 Impact Factor
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    ABSTRACT: We examined the abrasiveness of glycine powders with particle diameters of 63 and 100 mum by measuring the depth and volume of defects produced during air polishing of human dentin. A total of 36 extracted human teeth were embedded in acrylic resin. The resin blocks were polished until the dentin surfaces were exposed. The nozzle of an air polisher was mounted 4 mm from the dentin surface, and the dentin surface was treated for 5 s at one of two angles of incidence (45 degrees or 90 degrees). Three materials were used in the polishing process: NaHCO(3) powder with a mean particle diameter of 100 microm (Handy Jet Powder), glycine powder with a mean particle diameter of 63 microm (Handy Jet Powder PMTC), and glycine powder with a mean particle diameter of 100 microm (Handy Jet Powder Recall). The defect depth at both angles was significantly deeper after treatment with Handy Jet Powder or Handy Jet Powder PMTC. The defect volume was the greatest with Handy Jet Powder, followed by Handy Jet Powder PMTC, and Handy Jet Powder Recall. The larger diameter glycine powder resulted in less damage to the dentin.
    Odontology 02/2010; 98(1):31-6. · 1.58 Impact Factor
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    ABSTRACT: The purpose of this study was to investigate the effects of three additives, Sn, Ga, and In, as well as the main constituents, Pd and Cu, of Ag-Pd-Au-Cu alloys on the initial bond strength of 4-META adhesive cement to these alloys. The Ag-Pd-Au-Cu alloys consisted of 20%, 30% or 40% Pd, and 10%, 15% or 20% Cu, 20% Au, and Ag as balance. Besides, additive metals (Sn, Ga, and In) of 2% and 4% were added to these compositions. The addition of three additives, in general, increased the initial bond strength of the cement in comparison to the mother compositions (0% additives), although the degrees of effectiveness of the three additives were different and varied with their contents. Among these additives, a remarkable increase in bond strength was observed with the addition of In. The increase in Cu content, in many cases, resulted in an increase in bond strength at high Pd contents (30% and 40%), but a decrease at low Pd content (20%) in some cases. The positive effects of the three additives and Cu could be due to the formation of a suitable oxide layer for strong bonding with 4-META.
    Dental Materials Journal 10/2008; 27(5):678-86. · 0.81 Impact Factor
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    Kiyoshi Kakuta, Hideo Ogura
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    ABSTRACT: Effects of abrasive and fiber components in a medium on the wear behavior of composite resins were evaluated. Calcium diphosphate and methyl cellulose were included in the medium as abrasive and fiber components respectively. A range of 0, 4, or 8% abrasive- or fiber-containing media were applied on a composite resin specimen during a simulated occlusal wear test. Four composite resins, Clearfil AP-X, Z100 Restorative, SOLARE P, and SOLIDEX F, were tested to evaluate the effects of these components in the medium. Presence of abrasive material in the medium increased the wear of composite resins significantly, but its effect differed among the composite resins. Presence of fiber material in the medium significantly decreased the wear of two composite resins, whereas the other two composites showed no significant differences. Nonetheless, presence of fiber in the medium generally tended to prevent the wear of composite resins.
    Dental Materials Journal 10/2008; 27(5):716-22. · 0.81 Impact Factor
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    ABSTRACT: The effects of occlusal cycles and brushing cycles on wear of composite resins were investigated using a combined wear test, which carried out occlusal and toothbrush wear tests alternately. Worn volume and maximum worn depth were measured to evaluate wear under four combinations of two different cycles (occlusal cycles: 50 and 150 cycles; brushing cycles: 20 and 50 cycles). With composite resin APX, which consisted of relatively large and irregular-shaped filler particles, its worn volume and worn depth significantly increased with the number of occlusal cycles. With composite resin Z100, which consisted of relatively small and irregular-shaped filler particles, its wear values significantly increased with both brushing and occlusal cycles. With composite resin SRE, which consisted of small, irregular-shaped, inorganic filler particles and large organic filler particles, its worn volume significantly increased with the occlusal cycle when under a lower brushing cycle. With composite resin SDX, which consisted of spherical inorganic filler particles and large organic filler particles, its wear was not influenced by increases in both brushing and occlusal cycles.
    Dental Materials Journal 04/2008; 27(2):243-50. · 0.81 Impact Factor
  • Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology) 01/2008; 50(2):97-103.
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    Akira Nakai, Hideo Ogura
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    ABSTRACT: The objective of this study was to develop a casting investment that prevents the blackening of the cast surface of noble metal alloys. Experimental investments were prepared using a gypsum-bonded investment in which a hydroxide, namely Mg(OH)2 or Ca(OH)2, was added. An Ag-Pd-Cu-Au alloy was cast into the mold made of the prepared investment. The addition of both hydroxides showed a significant effect on the color of as-cast surfaces, which was improved with increase in additive content. When Mg(OH)2 or Ca(OH)2 was added at more than 4.0 mass% to the investment, it was useful in preventing the blackening of the as-cast surfaces of an Ag-Pd-Cu-Au alloy. As for differences in the effects between Mg(OH)2 and Ca(OH)2, they were not found.
    Dental Materials Journal 12/2007; 26(6):870-4. · 0.81 Impact Factor
  • Mihoko Kon, Kiyoshi Kakuta, Hideo Ogura
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    ABSTRACT: Effects of occlusal and brushing forces on the wear of composite resins were investigated using three different wear tests: simulated occlusal wear test, toothbrush wear test, and combined wear test which carried out toothbrush wear test and occlusal wear test alternately. Test specimens were prepared from four commercial composite resins. Worn volume and maximum worn depth were measured under different occlusal forces (40 N and 80 N) and brushing forces (1.5 N and 3 N) in the three wear tests. Worn surfaces were observed using a SEM. In all the three wear tests, both higher occlusal and brushing forces resulted in significantly greater worn volume and higher maximum worn depth. The effects of occlusal force on worn volume and maximum worn depth varied with different composites, indicating that the four tested composites showed different wear behaviors under different occlusal forces and brushing forces. It was suggested that their different wear behaviors most probably stemmed from the differences in their filler systems.
    Dental Materials Journal 04/2006; 25(1):183-94. · 0.81 Impact Factor
  • Katuma Kato, Kiyoshi Kakuta, Hideo Ogura
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    ABSTRACT: The aim of this study was to investigate the effect of antagonist material and configuration on combined wear, which was produced by alternating toothbrush wear and simulated occlusal wear on one specimen. Worn volume and maximum worn depth comparisons were done using two antagonist materials (steel and ceramic) and two antagonist configurations (flat and round). For the material factor, worn volume by the ceramic antagonist was greater than that by steel antagonist in the combined wear test. For the configuration factor, the round ceramic antagonist induced a greater volume loss of the resin composite. As for maximum worn depth, both the material and configuration of antagonist were influencing factors in the combined wear test--where the round ceramic antagonist induced a deeper wear of the resin composite. Based on the results of this study, we concluded that a round ceramic antagonist is suitable to be used for evaluating the wear behavior of resin composites.
    Dental Materials Journal 10/2005; 24(3):368-76. · 0.81 Impact Factor
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    ABSTRACT: The purpose of this study was to investigate the effect of repeated machining up to 51 times using the same diamond bur on machining accuracy of inner and outer surfaces of CAD/CAM (computer-aided designing and computer-aided manufacturing) machined ceramic crowns. The surface topography of machined crowns was examined using photographs. It was found that machining accuracy was not affected by the number of machining times. In all measuring points, the inner surface was machined to a dimension larger than the die model (i.e., increased gap), whereas the outer surface was machined to a dimension smaller than the crown model (i.e., smaller crown). Photo observation showed that cervical contour was machined in a clear, rounded form from 1st to 11th crowns.
    Dental Materials Journal 04/2005; 24(1):123-33. · 0.81 Impact Factor
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    ABSTRACT: The diamond burs of two dental CAD/CAM systems (GN and CD) were examined if they could be used to fabricate up to 21 ceramic full crowns without fracture. After one, 11, and 21 machining times, the surfaces of the diamond burs were observed and the number of particles captured on SEM pictures was counted. The average surface roughness of the crowns was also measured. All diamond burs could be used to fabricate 21 ceramic crowns without fracture. A significant decrease in the number of diamond particles was found on the surfaces of GN burs after 11 and 21 machining times, but not on those of CD burs. The average surface roughness of GN crowns significantly increased with increase in the number of machining times. A significant positive correlation was found between the average surface roughness and the number of diamond particles.
    Dental Materials Journal 04/2005; 24(1):134-9. · 0.81 Impact Factor
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    ABSTRACT: Full crowns were fabricated from three different materials (titanium, ceramic, and resin composite) at different rest diameters using a dental CAD/CAM system, and then their marginal discrepancy measured. The deflection of cylindrical specimens at 500 gf was measured using the same materials and diameters as for the accuracy measurement. Marginal discrepancy decreased as rest diameter increased, and at the same rest diameter the titanium crown had lower marginal discrepancy than ceramic and composite crowns. A significant correlation was found between marginal discrepancy of the crowns and deflection of the materials. This correlation was aptly expressed in the regression equation, MG = 4.54DF+53.9, where MG represented marginal discrepancy and DF represented deflection. This equation can be used as a good measure for new materials which have different modulus of elasticity.
    Dental Materials Journal 01/2005; 23(4):572-6. · 0.81 Impact Factor
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    ABSTRACT: The mechanical properties of six 35Ag-30Pd-20Au-15Cu alloys containing different contents (2% and 4%) of Sn, Ga, or In and a 35Ag-30Pd-20Au-15Cu alloy without additives were evaluated. These alloys were subjected to four different heat treatments before a mechanical test. The distribution of the elements and their contents were analyzed. The mechanical properties of 35Ag-30Pd-20Au-15Cu alloy changed in wide-ranging ways with different heat treatments and with different additive contents. The effects of heat treatment on tensile strength and hardness significantly varied with different additives and their contents. These different changes could be attributed to the formation of different phases in these alloys. Based on the high strength and wide-ranging changes in the mechanical properties when subjected to softening and hardening heat treatments, the 2% Sn-added, 2% In-added, and 4% Ga-added alloys can be recommended for different dental restorations such as crown & bridges, inlays, and denture frameworks.
    Dental Materials Journal 01/2005; 23(4):474-89. · 0.81 Impact Factor
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    ABSTRACT: The purpose of this study was to evaluate the durability of tungsten carbide burs for the fabrication of titanium crowns using two dental CAD/CAM systems (DECSY, Digital Process, Japan and Cadim, Advance, Japan). A tungsten carbide bur in each system was examined and used without fracture to fabricate 51 titanium crowns. For both systems tiny chips were found on the bur blade at the 11th machining. These chips gradually enlarged as the number of machining times increased. At the first machining no significant difference in the average surface roughness was found on the crown between the two systems (1.6 microm for DECSY and 1.2 microm for Cadim). The cutting grooves became dull and the average surface roughness increased as the number of machining times increased. It is concluded that the tungsten carbide burs for both systems can be used to fabricate up to 51 titanium crowns.
    Dental Materials Journal 07/2004; 23(2):190-6. · 0.81 Impact Factor
  • Yukun Meng, Akira Nakai, Hideo Ogura
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    ABSTRACT: Different reducing agents (B, Al, Si and Ti) were individually added to two gypsum-bonded investments to prepare investments preventing surface blackening of some noble cast alloys. The effect of different additive contents on green-body and burnout compressive strength, setting and thermal expansion of the investments were evaluated. The strength and expansion of the investments were changed by the additives. The compressive strength of Al-, Si- and Ti-added investments decreased with the increase of additive contents. The burnout strength of B-added investments significantly increased while green-body strength remained unchanged. The setting expansion of the B-added investments increased while those of the Al-, Si- and Ti-added investments decreased with the increase of additive contents. The thermal expansion of the Si- and Ti-added investments decreased, and that of the Al- and B-added investments remained unchanged. Further study is necessary to evaluate the effects of these additives on the accuracy of dental castings.
    Dental Materials Journal 07/2004; 23(2):129-35. · 0.81 Impact Factor
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    ABSTRACT: The Vickers hardness of the cross-sectioned area of titanium castings made from an experimental resin-bonded calcia investment and three commercial investments was evaluated. The microstructure and element distribution of the surface zone were analyzed using an EPMA. The results showed that the high hardness of the casting surface could be decreased using the experimental investment. The hardness of the castings made from the experimental investment at a 25-50 microm depth was lower than those from the other investments, and the thickness of the hardened casting surface was 125 microm. Layered structures with fewer layers were formed on the surfaces of the castings made from the experimental investment. The layered structures were influenced by both the investment components and the mold temperature at casting. The less contaminating nature of the experimental investment components and the technology of the room temperature mold contributed to the improved surface properties of the resulting castings.
    Dental Materials Journal 04/2004; 23(1):46-52. · 0.81 Impact Factor
  • Hiroko Soma, Yukio Miyagawa, Hideo Ogura
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    ABSTRACT: A metal-resin composite material was experimentally prepared by mixing a powder consisting of Ag-Cu particles and BPO with a paste consisting of UDMA-based monomer and 4-META in the absence of tertiary amine. The working time and setting time were mainly affected by the amounts of 4-META, BPO and metal particles, most of them fulfilling the requirements for working time and setting time specified in ISO 4049:2000 in the present experimental conditions. The flexural strength ranged from 49.6 MPa to 77.8 MPa, and the highest value was obtained when the 4-META concentration was high and metal particle content was low. The flexural modulus of elasticity, ranging from 6.7 GPa to 11.9 GPa, significantly increased as the 4-META concentration and metal particle content increased. Based on its mechanical properties, this metal-resin composite in which metal particles are involved in the polymerization initiation system has the potential to be used as a dental restorative material.
    Dental Materials Journal 01/2004; 22(4):543-55. · 0.81 Impact Factor

Publication Stats

70 Citations
31.76 Total Impact Points

Institutions

  • 1999–2012
    • The Nippon Dental University
      • • Department of Dental Materials Science
      • • Department of Periodontology
      • • Graduate School of Life Dentistry at Niigata
      Tokyo, Tokyo-to, Japan
  • 2004
    • Showa University
      Shinagawa, Tōkyō, Japan
  • 1996–2003
    • Mahidol University
      • Department of Prosthodontices
      Bangkok, Bangkok, Thailand