Hideo Ogura

The Nippon Dental University, Edo, Tōkyō, Japan

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Publications (47)42.89 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this work was to fabricate zirconia copings from fully sintered Y-TZP blocks using a Nd:YVO4 nanosecond laser in order to avoid complicated procedures using conventional CAD/CAM systems. To determine the most appropriate power level of a Nd:YVO4 laser, cuboid fully sintered Y-TZP specimens were irradiated at six different average power levels. One-way ANOVAs for the average surface roughness and laser machining depth revealed that an average power level of 7.5 W generated a smooth machined surface with high machining efficiency. Y-TZP copings were then machined using the proposed method with the most appropriate power level. As the number of machining iterations increased, the convergence angles decreased significantly (p<0.01). The accuracy of the machined copings was judged to be good based on 3D measurements and traditional metal die methods. The proposed method using the nanosecond laser was demonstrated to be useful for fabricating copings from fully sintered Y-TZP.
    Dental Materials Journal 04/2014; 33(3). DOI:10.4012/dmj.2013-348 · 0.97 Impact Factor
  • Yuki Hasegawa · Shin-Ichi Goto · Hideo Ogura ·
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    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; 33(3). DOI:10.4012/dmj.2013-283 · 0.97 Impact Factor
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    ABSTRACT: PurposeThe purpose of this study was to examine the electric current induced in teeth and tooth-bonded brackets by electromagnetic fields from electric toothbrushes and the curing lights used for photo-activating light-cured resins.Materials and methodsCuring lights-generated low-frequency magnetic fields (1–2000 Hz) were measured with a spectrum analyzer. Temperature changes induced in the enamel and pulpal dentin surface of extracted upper premolar teeth (with or without a stainless steel or zirconia bracket) by electric toothbrushes and curing lights were estimated using an infrared thermometer. Electric current induced in these extracted teeth by electric appliances was estimated using a digital multimeter.ResultsCuring lights generated low-frequency magnetic fields. Irradiation of the tooth surface by curing lights elevated the temperature of the enamel and pulpal dentin surfaces, but there were no differences between curing lights. About electric current induced in extracted teeth (with or without a bracket) by electric toothbrushes and curing lights, the highest current was induced in teeth to which a zirconia bracket was bonded, whereas the lowest current was in unmodified teeth. Intermediate currents were generated in teeth bonded to stainless steel brackets.Conclusion The low-frequency magnetic fields induced by electric toothbrushes and light curing units induce electric current in tooth tissue, irrespective of whether these teeth are bonded to stainless steel or zirconia brackets.
    Orthodontic Waves 06/2013; 72(2):77-85. DOI:10.1016/j.odw.2013.03.002
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    ABSTRACT: Objective: Dedifferentiated fat (DFAT) cells derived from mature adipocytes have been considered to be a homogeneous group of multipotent cells, which might be an alternative source of adult stem cells for regenerative medicine. However, many aspects of the cellular nature about DFAT cells remained unclarified. Based on recent understandings on the connection between the tissue-specific progenitor and perivascular cells, this study aimed to elucidate the basic characteristics of DFAT cells underlying their perivascular functions and differentiation potentials. Method: By modified ceiling culture technique, DFAT cells were converted from human adipocytes in the buccal fat pads. Flow cytometry and differentiation analysis were carried out to determine the phenotype and multipotency of those cells. The pro-vascular ability of DFAT cells were studied by Matrigel assay also. Result: Flow cytometry analysis revealed that those derived cells were a homogeneous population of CD13+ CD29+ CD105+ CD44+ CD140b+ CD31- CD34- CD309- CD106- CD146- α-SMA- cells. Compared with previous reports, DFAT cells in this study demonstrated tissue-specific differentiation properties with strong adipogenic but much weaker osteogenic capacity. Neither did they exhibit endothelial phenotype under angiogenic induction. For the first time, we found human DFAT cells could undertake characteristics of perivascular lineage, including expression of pericyte markers, Dil-ac-LDL uptake ability, vascular network formation ability on Matgrigel. Furthermore, DFAT cells could largely promote and stabilize the vessels structures formed by human umbilical vascular endothelial cells (HUVECs) in vitro. Conclusion: This study provided novel evidence on the pericyte nature of human DFAT cells, which also supported the recent understanding about the perivascular origin of adult stem cells that tissue-specific progenitor cells in mesenchymal tissues would associate with the blood vessels, exhibiting perivascular characteristics and functions.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
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    ABSTRACT: Very weak electrical, magnetic and ultrasound signal stimulations are known to promote the formation, metabolism, restoration and stability of bone and surrounding tissues after treatment and operations. We have therefore investigated the possibility of intraoral generation of electricity and magnetism by occlusal force in an in vitro study. Biting bimorph piezoelectric elements with lead zirconate titanate (PZT) using dental models generated appropriate magnetism for bone formation, i. e. 0.5-0.6 gauss, and lower electric currents and higher voltages, i. e. 2.0-6.0 μA at 10-22 V (appropriate levels are 30 μA and 1.25 V), as observed by a universal testing machine. The electric currents and voltages could be changed using amplifier circuits. These results show that intraoral generation of electricity and magnetism is possible and could provide post-operative stabilization and activation of treated areas of bone and the surrounding tissues directly and/or indirectly by electrical, magnetic and ultrasound stimulation, which could accelerate healing.
    Dental Materials Journal 11/2012; 31(6):1001-7. DOI:10.4012/dmj.2012-123 · 0.97 Impact Factor
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    ABSTRACT: Magnetic fields can represent a health problem, especially low frequency electromagnetic fields sometimes induced by electric current in metallic objects worn or used in or on the body (as opposed to high frequency electromagnetic fields that produce heat). Electric toothbrushes are widely used because of their convenience, but the electric motors that power them may produce electromagnetic waves. In this study, we showed that electric toothbrushes generate low frequency (1-2000 Hz) magnetic fields and induce electric current in dental appliances (e. g. orthodontic and prosthetic appliances and dental implants). Current induced by electric toothbrushes might be dependent on the quantity and types of metals used, and the shape of the appliances. Furthermore, these induced currents in dental appliances could impact upon human oral health, producing pain and discomfort.
    Dental Materials Journal 10/2012; 31(5):856-62. DOI:10.4012/dmj.2012-129 · 0.97 Impact Factor
  • Yoichi Tamura · Kiyoshi Kakuta · Hideo Ogura ·
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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; 101(2). DOI:10.1007/s10266-012-0074-1 · 1.52 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. DOI:10.4012/dmj.2010-091 · 0.97 Impact Factor
  • Kazuo Ohkuma · Miku Kazama · Hideo Ogura ·
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    ABSTRACT: Using a casting ring with openings on both sides and a water-absorbent polymer, heterogeneity is maintained in a single casting and a precise MOD inlay can be produced. We produced 9 different kinds of gold-silver-palladium (Au-Ag-Pd) alloys by changing the ratio of palladium, gold, and copper and investing them, and changing parameters such as the angulation of the casting ring openings and the water:powder ratios to produce MOD inlay castings. We measured the expansion and shrinkage percentage of the castings in both the buccolingual and mesiodistal directions. From this experiment, we learned that precise MOD inlay castings can be produced using rings with 240° openings when invested in a thick mix having a standard water:powder ratio or using rings with 200° openings when invested in a thick mix having a water:powder ratio for a 12 wt%Au-20∼26Pd-20.48∼26.48Cu-40Ag-1.5Zn-0.02Ir alloyes.
    Odontology 08/2011; 100(1):34-40. DOI:10.1007/s10266-011-0016-3 · 1.52 Impact Factor
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    Kazuo Ohkuma · Miku Kazama · Hideo Ogura ·
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    ABSTRACT: Recently, the use of all-ceramic restorations has increased and been applied for many types of clinical treatment such as bridges which can be made with high strength ceramic material: yttria partially stabilized zirconia (Y-PSZ) employing the CAD/CAM system. Consequently, points that can grind high strength ceramic material effectively are necessary for modifying the shape of restorations or removing them. So in our research, we fabricated new diamond points used to grind Y-PSZ. These points were made by electrodeposition of diamond grains. The diameter of the diamond grains are larger (200 µm) than that of traditional points (100 µm). High strength ceramic material was ground to assess the grinding weight and grinding depth various types of points. As a result, Y-PSZ could be ground efficiently with the diamond point which has a larger diameter and employs lager grains (200 µm).
    Dental Materials Journal 07/2011; 30(4):511-6. DOI:10.4012/dmj.2010-152 · 0.97 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. DOI:10.4248/IJOS11044 · 2.53 Impact Factor
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    ABSTRACT: Objectives: Bass-technique, which requires brush angle kept at 45 degree against teeth, is well-known as an effective tooth-brushing method for plaque control since 1954. However it was doubtful whether people utilized Bass-technique properly. The aim of this study was to analyze the brush-angle guiding intervention factors (BGIF) involved during tooth-brushing in order to guide people to proper manner of Bass-technique. Methods: In order to clear effect of BGIF, we evaluated the brush angle during tooth-brushing by logging data of accelerator which is introduced in the powered toothbrush (HT-B551, Omron healthcare, Japan). HT-B551 has a brush angle auto guiding system operated by an accelerator, which detects component force of gravity for calculating the brush angle. This system enables to operate other device, such as vibrator, light, et al. to inform brush angle nearby 45 degree. Five BGIF were evaluated in this study, (1) special operational mode nearby 45 degree, (2) symbolic bump on the surface, (3) power-on lamp showing nearby 45 degree, (4) with or without dental education, (5) watching through mirror during tooth-brushing. Ten examinees took a brushing test to measure a practical brush angle when they tried to brush their teeth in contact with 45 degree. Results: The investigation of BGIF revealed that: (1) Special operational mode was the best (45.12.1deg.), (2) Symbolic bump was the worst (47.27.7deg.), (3) People with dental education performed slightly well(48.819.0deg.), compared with group without any BGIF (44.99.8 deg., n=10, statistically analyzed). Conclusion: Our research suggests that selecting special operational-mode nearby 45 degree is the best method to guide people to proper manner of Bass-technique. At that point of view, using HT-B551 is the best way to obtain proper manner of Bass-technique easily, rather than depending on symbolic bump introduced in many toothbrush.
    IADR General Session 2011; 03/2011
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    ABSTRACT: Objectives: Self-performed infection control is important to improve oral hygiene since professions may not monitor their patients during home dental care. Powered-toothbrush is one of the promising tools for home dental care since powered-toothbrush can introduce sensors to detect parameters relevant to plaque-removal. Accelerator introduced powered-toothbrush (AIPT) enables to detect the brush-angle, therefore makes it possible to control the operational-mode by certain brush-angles, leading to better plaque-removal effect. The aim of this study was to analyze the plaque-removal effect of AIPT. Methods: We evaluated the powered-toothbrush by measuring the percent removal of the artificial plaques in a dental model via imaging analysis and compared it with clinical data. AIPT (HT-B551, Omron healthcare, Japan) have three operational-modes, one operating on specific speed at certain brush-angle (Auto-mode) and the other operating on several monotonous speeds. Auto-mode operates on the combination of three specific frequencies, high-speed was chosen when brushing at occlusion-side, intermediate-speed was chosen when brush-angle is nearby 45 degrees and low-speed was chosen when brushing at buccal-side and lingual-side. Point-mode is one of the monotonous operational-mode of AIPT which operates on high-speed. Results: The investigation of plaque-removal effect for AIPT revealed that: (1) operating AIPT at specific frequency will enlarge the vibration due to mechanical-resonance even at the lower speed range and improves plaque-removal; (2) Point-mode marked the best plaque-removal among three specific frequencies; (3) tendency of the in vitro data was relevant to in vivo data ; (4) plaque-removal of the Auto-mode overcomes Point-mode by 74.56.5% to 66.911.3% (n=6, statistically analyzed). Conclusion: Our research suggests that focusing on mechanical-resonance for operating the powered-toothbrush induces efficient plaque-removal and also selecting best operational-mode at certain brush angle possibly benefit patients with plaque-removal due to realizing elongated brushing time and reducing stimulus toward gingival from the powered-toothbrush.
    IADR General Session 2010; 07/2010
  • Kazuhiro Tada · Kiyoshi Kakuta · Hideo Ogura · Soh Sato ·
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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. DOI:10.1007/s10266-009-0113-8 · 1.52 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. DOI:10.4012/dmj.27.678 · 0.97 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. DOI:10.4012/dmj.27.716 · 0.97 Impact Factor
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    Amornrat Wonglamsam · Kiyoshi Kakuta · Hideo Ogura ·
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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. DOI:10.4012/dmj.27.243 · 0.97 Impact Factor

  • Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology) 01/2008; 50(2):97-103. DOI:10.2329/perio.50.097
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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. DOI:10.4012/dmj.26.870 · 0.97 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. DOI:10.4012/dmj.25.183 · 0.97 Impact Factor

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256 Citations
42.89 Total Impact Points

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  • 2000-2014
    • The Nippon Dental University
      • • Department of Dental Materials Science
      • • School of Life Dentistry - Niigata
      Edo, Tōkyō, Japan
  • 1996
    • Mahidol University
      • Department of Prosthodontices
      Bangkok, Bangkok, Thailand