Keiichi Yoshida

Nagasaki University Hospital, Nagasaki, Nagasaki, Japan

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Publications (26)33.13 Total impact

  • Source
    Keiichi Yoshida, Xiangfeng Meng
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    ABSTRACT: Objective: The purpose of this study was to evaluate the Knoop hardness number (KHN) of dual-cured core build-up resin composites (DCBRCs) at 6 depths of cavity after 3 post-irradiation times by 4 light-exposure methods. Material and Methods: Five specimens each of DCBRCs (Clearfil DC Core Plus [DCP] and Unifil Core EM [UCE]) were filled in acrylic resin blocks with a semi-cylindrical cavity and light-cured using an LED light unit (power density: 1,000 mW/cm2)at the top surface by irradiation for 20 seconds (20 s), 40 seconds (40 s), bonding agent plus 20 seconds (B+20 s), or 40 seconds plus light irradiation of both sides of each acrylic resin block for 40 seconds each (120 s). KHN was measured at depths of 0.5, 2.0, 4.0, 6.0, 8.0, and 10.0 mm at 0.5 hours, 24 hours, and 7 days post-irradiation. Statistical analysis was performed using repeated measures ANOVA and Tukey's compromise post-hoc test with a significance level of p<0.05. Results: For both DCBRCs, at 0.5 hours post-irradiation, the 20 s and 40 s methods showed the highest KHN at depth of 0.5 mm. The 40 s method showed significantly higher KHN than the 20 s method at all depths of cavity and post-irradiation times, except UCE at depth of 0.5 mm (p<0.05). The 120 s method did not result in significantly different KHN at all depths of cavity and post-irradiation times (p>0.05). In DCP, and not UCE, at 24 hours and 7 days post-irradiation, the B+20 s method showed significantly higher KHN at all depths of cavity, except the depth of 0.5 mm (p<0.05). Conclusion: KHN depends on the light-exposure method, use of bonding agent, depth of cavity, post-irradiation time, and material brand. Based on the microhardness behavior, DCBRCs are preferably prepared by the effective exposure method, when used for a greater depth of cavity.
    Journal of applied oral science: revista FOB 02/2014; 22(1):44-51. · 0.39 Impact Factor
  • Keiichi Yoshida, Xiangfeng Meng
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    ABSTRACT: The optimal luting material for fiber-reinforced posts to ensure the longevity of foundation restorations remains undetermined. The purpose of this study was to evaluate the suitability of 3 dual-polymerizing resin cements and 2 dual-polymerizing foundation composite resins for luting fiber-reinforced posts by assessing their Knoop hardness number. Five specimens of dual-polymerizing resin cements (SA Cement Automix, G-Cem LincAce, and Panavia F2.0) and 5 specimens of dual-polymerizing foundation composite resins (Clearfil DC Core Plus and Unifil Core EM) were polymerized from the top by irradiation for 40 seconds. Knoop hardness numbers were measured at depths of 0.5, 2.0, 4.0, 6.0, 8.0, and 10.0 mm at 0.5 hours and 7 days after irradiation. Data were statistically analyzed by repeated measures ANOVA, 1-way ANOVA, and the Tukey compromise post hoc test (α=.05). At both times after irradiation, the 5 resins materials showed the highest Knoop hardness numbers at the 0.5-mm depth. At 7 days after irradiation, the Knoop hardness numbers of the resin materials did not differ significantly between the 8.0-mm and 10.0-mm depths (P>.05). For all materials, the Knoop hardness numbers at 7 days after irradiation were significantly higher than those at 0.5 hours after irradiation at all depths (P<.05). At 7 days after irradiation, the Knoop hardness numbers of the 5 resin materials were found to decrease in the following order: DC Core Plus, Unifil Core EM, Panavia F2.0, SA Cement Automix, and G-Cem LincAce (P<.05). The Knoop hardness number depends on the depth of the cavity, the length of time after irradiation, and the material brand. Although the Knoop hardness numbers of the 2 dual-polymerizing foundation composite resins were higher than those of the 3 dual-polymerizing resin cements, notable differences were seen among the 5 materials at all depths and at both times after irradiation.
    The Journal of prosthetic dentistry 01/2014; · 1.22 Impact Factor
  • Qing Liu, Xiangfeng Meng, Keiichi Yoshida, Xiaoping Luo
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    ABSTRACT: Self-adhesive resin cement with the characteristics of glass ionomer cement is more susceptible to water than conventional resin cements. It is unknown if there is a higher risk of bond degradation at the interface with silanized ceramic in an oral environment. The purpose of this study was to evaluate the bond degradation behavior of self-adhesive cement under simulated oral conditions, by comparing it with the behavior of 3 conventional resin cements. Three conventional resin cements, Linkamx HV (LMHV), Clearfil Esthetic Cement (CEC), and SuperBond (SB), were bonded to silanized ceramic (ProCAD) with the manufacturer's recommended silane coupler (GC Ceramic Primer (GCCP), Clearfil Ceramic Primer (CCP), and Porcelain Liner M (PLM), respectively), while a self-adhesive cement (G-CEM) was bonded with each of the 3 silane couplers. Maximum water sorption and solubility of the resin cements were measured according to the ISO 4049 standard during 6 weeks of water storage. The microshear bond strength of each silane/cement group (n=10 per thermal cycling subgroup) was tested after 0, 10,000, and 30,000 thermal cycles (TC), and bond failure types were counted. One- and two-way ANOVAs and the Tukey multiple comparisons test (α=.05) were used to evaluate the bond strength data. G-CEM had significantly higher water sorption (P<.001) and solubility than conventional resin cements. Statistical analysis showed that the bond strength of all silane/cement groups was reduced significantly by thermal cycling (P=.01 for CCP/G-CEM, P=.003 for GCCP/LMHV, P<.001 for other groups). The bond strength of G-CEM with the 3 silane couplers was significantly degraded from TC 0 to 10,000 (P<.001 for GCCP/G-CEM and PLM/G-CEM, P=.01 for CCP/G-CEM); however, the bond strength appeared to stabilize with no significant degradation from TC 10,000 to 30,000. This behavior was different from that of conventional resin cements, which demonstrated bond degradation throughout TC 0-30,000. After TC 30,000, the bond strength of G-CEM did not differ significantly from that of the 3 conventional resin cements. The bond degradation behavior of G-CEM under thermal cycling conditions differs from that of conventional resin cements.
    The Journal of prosthetic dentistry 03/2011; 105(3):177-84. · 1.22 Impact Factor
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    ABSTRACT: The aim of this study was to measure siloxane quantity, pH value, and resin wettability on ceramics silanized by five silane coupling agents, and to test the correlation of these parameters of silane coupling agents with bond durability between a machinable glass ceramic and resin cements. 1.5-mm-thick ceramic plates (ProCAD, Ivoclar Vivadent) were polished, cleaned, and bonded with ten combinations of five silane coupling agents (Monobond S [Ivoclar Vivadent], Rely X Ceramic Primer [3M], Clearfil Ceramic Primer [Kuraray], GC Ceramic Primer [GC], Porcelain Liner M [Sun Medical]) and two dual-curing resin cements (VariolinkII [VLII, Ivoclar Vivadent], Linkmax HV [LMHV, GC]). Their microshear bond strength was measured after 0, 10,000, and 30,000 thermal cycles. Siloxane quantity, pH value of silane coupling agents and contact angle of Heliobond (Ivoclar Vivadent) to silanized ceramic were measured using a FTIR spectrophotometer, pH-indicator strips, and a contact-angle meter, respectively. Bond strength data were analyzed by three-way ANOVA. For each cement, Pearson's correlation coefficient was calculated to analyze possible correlation between bond strength under different thermocycling conditions and absorbance peak of siloxane, pH value of silane coupling agents, and contact angle of resin to the silanized ceramic surface. The bond strength of ceramic was significantly influenced by the silane coupling agent and thermal cycles, not by resin cement. For both cements, only a negative correlation was found to be significant between the contact angle of resin to silanized ceramic surfaces and bond strength after 30,000 thermal cycles. The better the wettability of resin on different silanized ceramic surfaces could improve their bond durability.
    The journal of adhesive dentistry 02/2011; 13(1):71-8. · 0.91 Impact Factor
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    ABSTRACT: The aim of the present study was to assess the influence of pre-treatments of zirconia by sandblasting and/or heat treatment on the flexural strength of zirconia and debonding/crack-initiation strength of porcelain-veneered zirconia ceramic. Zirconia ceramic specimens were divided into four groups according to treatment (grinding as controls, sandblasting, heat treatment at 1000°C for 10 min, and heat treatment after sandblasting). The porcelain- veneered zirconia specimens were also prepared. The zirconia specimens were subjected to three-point bending tests, and flexural strength was calculated. The debonding/crack-initiation strength of porcelain-veneered zirconia ceramic was measured according to ISO 9693. X-ray diffractometry (XRD) was used to estimate the relative amount of monoclinic phase. There was no significant difference in flexural strength between the four treatments (p > 0.05). The highest amount of monoclinic phase was found after sandblasting. No monoclinic phase was obtained from heat treatment and heat treatment after sandblasting groups, and these two groups showed significantly higher debonding/crack-initiation strength than other two groups (p < 0.05). All specimens failed within the veneering porcelain. No elements of veneering porcelain were detected on the zirconia side at the interface using EPMA (electron probe microanalyzer). The present study suggests that the pre-treatment of zirconia with heat treatment after sandblasting prior to firing porcelain does not affect the debonding/crack-initiation strength of porcelain-veneered zirconia ceramic.
    The journal of adhesive dentistry 02/2011; 13(1):79-84. · 0.91 Impact Factor
  • Xiangfeng Meng, Keiichi Yoshida, Mitsuru Atsuta
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    ABSTRACT: The bond strength and bond durability of two high-viscosity dual-curing resin luting agents with different surface treatments of ceramic were investigated. GN-I machinable ceramic surfaces were treated with 37% phosphoric acid for 30 s (PA), 5% hydrofluoric acid for 5 s (HF-5), 10 s (HF-10), or 30 s (HF-30), or blasting with 50-microm Al2O3 for 10 s (AB). The roughness of the ceramic surface was measured. Treated ceramic surfaces were bonded with three resin bonding systems (RBS): Ceramic Primer/LinkmaxHV (CP/LMHV), Monobond S/VariolinkIIHV (MBS/VLIIHV), or MBS/Heliobond/VLIIHV (MBS/HB/VLIIHV). A microshear test was used to measure the bond strength after 24 h (TC 0) and subsequent thermocycling (TC 10,000 at 4 degrees C and 60 degrees C). ANOVA was performed for statistical analysis, with significance set at p < 0.05. For three RBSs, bond strength at TC O was not affected, regardless of ceramic surface treatment (p > 0.05). All combined groups of ceramic surface treatment and resin bonding system decreased after 10,000 thermal cycles, especially groups treated with alumina blasting and bonded with each of three RBSs (p < 0.05). MBS/HB/VLIIHV with each surface treatment did not improve the bond strength and durability compared with MBS/VLIIHV. CP/LMHV and MBS/VLIIHV obtained sufficient bond strength and bond durability to GN-I machinable ceramic by only cleaning with PA; the application of HB may not be necessary.
    The journal of adhesive dentistry 06/2008; 10(3):189-96. · 0.91 Impact Factor
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    Xiangfeng Meng, Keiichi Yoshida, Mitsuru Atsuta
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    ABSTRACT: To investigate the influence of ceramic thickness on the mechanical properties and polymer structure (degree conversion and cross-linking density) of three dual-cured resin luting agents. Three dual-cured resin luting agents [Linkmax HV (GC), Nexus 2 (Kerr), and Variolink IIHV (Ivoclar-Vivadent)] were polymerized with or without 800 mW/cm2 irradiation through 0-3-mm-thick GN-I (GC) machinable ceramic. Bar-shape specimens were subjected to three-point bending to determine flexural strength (FS) and elastic modulus (EM) after dry storage at 37 degrees C for 24 h. Knoop hardness was measured on the irradiated surface of disk-shaped specimens before (KHN1) and after (KHN2) storage of 100% ethanol solution at 37 degrees C for 24 h. KHN1 and KHN2 were estimated as indirect indicators of degree of conversion (DC) and cross-linking density, respectively. Data were analyzed by one-way ANOVA and Student-Newman-Keuls test for each luting agent, and four mechanical properties were subjected to regression analysis. For three resin luting agents with dual-cured mode, FS, EM, KHN1, and KHN2 decreased with the increase of ceramic thickness. FS except for Nexus 2 and EM for three resin luting agents had a positive linear relationship with both KHN1 and KHN2. The variables tested behaved differently. When the ceramic thickness increased, the chemical cured components of dual-cured resin luting agents did not produce significant compensation for all variables. Mechanical properties and polymer structure of dual-cured resin luting agents was dependent on the intensity of light irradiation.
    Dental Materials 06/2008; 24(5):594-9. · 3.77 Impact Factor
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    ABSTRACT: The aim of the present study was to evaluate the crystalline phase and microstructure of 4 commercial machinable ceramic blocks--Cerec Vitablocs Mark II (Vita), ProCAD (Ivoclar/Vivadent), GN-I (GC), and GNCeram (GC)--and compare flexural strength and shear bond strength between a dual-curing resin luting agent and the ceramics treated with a silane coupling agent. Specimens were examined using scanning electron microscopy/energy-dispersive x-ray spectroscopy, and x-ray diffractometry. Three-point bending tests were performed with polished specimens 20 mm long, 4 mm wide, and 1.2 mm thick. Two differently shaped specimens for each of the 4 machinable ceramics were treated with a silane coupling agent. The specimens were then cemented together with a dual-curing resin luting agent. Half of the specimens were stored in water at 37 degrees C for 24 h and the other half were thermocycled 20,000 times. Chemical composition, crystalline phase, and crystallinity were significantly different between brands. The Vitablocs Mark II material had the significantly lowest flexural strength (101.7 +/- 15.3 MPa), while the GNCeram material had the highest (174.8 +/- 10.3 MPa). The use of a silane coupling agent yielded high shear bond strength after 20,000 thermocycles (Vitablocs Mark II: 37.7 +/- 3.7 MPa, ProCAD: 41.2 +/- 3.1 MPa, GNCeram: 50.2 +/- 2.1 MPa), except with the GN-I material (23.9 +/- 4.4 MPa). It appeared that crystal distribution and particle size of leucite crystal, not crystallinity, in the feldspar glass matrix of silica-based machinable ceramics might influence the flexural strength and efficacy of a silane coupling agent in bonding between a dual-curing resin luting agent and machinable ceramics.
    The journal of adhesive dentistry 09/2007; 9(4):407-13. · 0.91 Impact Factor
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    Xiangfeng Meng, Keiichi Yoshida, Mitsuru Atsuta
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    ABSTRACT: The purpose of this study was to evaluate the microshear bond strength and bond durability between ceramic and two dual-cured resin luting agents irradiated by different light intensities. Ceramic specimens were bonded with two resin bonding systems: Ceramic Primer and Linkmax HV (CP/LMHV) and Monobond S and Variolink IIHV (MBS/VLIIHV), and were either irradiated by 800, 310, 160, 80, and 40 mW/cm2 light or not irradiated. Bond strength was measured after 24-hour water storage at 37 degrees C and after subsequent 10,000 times of thermal cycling. Failure modes were determined by stereomicroscopy. After 24-hour water storage, there were no significant differences among the various irradiation conditions for both MBS/VLIIHV and CP/LMHV. However, regardless of light intensity, MBS/VLIIHV showed higher bond strength than CP/VLIIHV at each thermal cycling, except for no irradiation condition at 10,000 thermal cycles. In conclusion, thermal cycling significantly reduced the bond strength for all groups.
    Dental Materials Journal 08/2007; 26(4):575-81. · 0.81 Impact Factor
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    ABSTRACT: The purpose of the present study was to evaluate the effect of four silane coupling agents on the bond strength between two resin-modified glass ionomer cements and a machinable leucite glass ceramic. Ceramic specimens were ground with silicon carbide paper and cleaned with phosphoric acid. They were then conditioned and bonded with combinations of four silane coupling agents (GC Ceramic Primer, Clapearl Bonding Agent, Clearfil Mega Bond Porcelain Bonding Kit, and RelyX Ceramic Primer) and two resin-modified glass ionomer cements (Fuji Luting S and Fuji Lute). Shear bond strength was determined after 24-hour immersion in water or after thermocycling of 50,000 cycles. The results showed that every silane coupling agent significantly improved the bond strength. It was thus recommended that resin-modified glass ionomer cement be applied in conjunction with silane coupling agent when luting ceramic restorations.
    Dental Materials Journal 04/2007; 26(2):240-4. · 0.81 Impact Factor
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    ABSTRACT: The aim of the present study was to evaluate mechanical properties, including surface hardness, flexural strength, and flexural modulus, of two dual-cured resin luting agents [Clearfil Esthetic Cement (CEC) and Variolink II (VLII)] irradiated through four thicknesses of leucite ceramics (0, 1, 2, and 3 mm) and to evaluate their shear bond strength to zirconia ceramic (Cercon) using each ceramic primer. Knoop hardness was measured on a thin layer of resin luting agent on the ceramic surface. Three-point bending tests were performed after 24 hours of storage at 37 degrees C. Two differently shaped zirconia ceramic specimens with or without sandblasting with alumina were treated with each primer. The specimens were then cemented together with each resin luting agent. Half of the specimens were stored in water at 37 degrees C for 24 hours and the other half were thermocycled 5000 times. VLII revealed statistically higher Knoop hardness and flexural modulus than CEC for each thickness of ceramic. No significant differences in flexural strength were observed between VLII and CEC for each ceramic spacer. Reduction of the mechanical properties with increase of ceramic thickness varied for each property; however, these properties were similar in the two materials. Blasting with alumina was significantly effective for increasing shear bond strength of both resin luting agents before and after thermal cycling. The use of Clearfil Ceramic Primer showed the highest shear bond strength and maintained bond durability after 5000 thermocycles. Mechanical properties of CEC dual-cured resin luting agent appear adequate for ceramic restorations.
    Journal of Prosthodontics 01/2007; 16(5):370-6. · 0.68 Impact Factor
  • Yukiko Tsuo, Keiichi Yoshida, Mitsuru Atsuta
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    ABSTRACT: This study evaluated the effect of alumina-blasting and three commercial adhesive primers on the shear bond strength of a dual-cured resin luting agent to zirconia ceramics. Two different-sized zirconia ceramic specimens were treated with or without alumina-blasting and then treated with one of three adhesive primers. Subsequently, specimens were cemented together with Linkmax HV (GC). Half of the specimens were stored in water at 37 degrees C for 24 hours and the other half thermocycled 10,000 times before shear bond strength testing. For groups treated with either alumina-blasting or primer, shear bond strength significantly decreased after thermal cycling. For groups treated with both alumina-blasting and one of the three primers, there were no significant differences in shear bond strength before and after thermal cycling (p<0.05). It was thus concluded that the application of each of the three adhesive primers following alumina-blasting was effective for strong bonding of resin luting agent to zirconia ceramics.
    Dental Materials Journal 12/2006; 25(4):669-74. · 0.81 Impact Factor
  • Keiichi Yoshida, Mitsuru Atsuta
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    ABSTRACT: To evaluate the surface hardness (Knoop Hardness Number) of the thin layer in three light-cured and dual-cured resin cements irradiated through or not through 2.0 mm thick machinable ceramics. A piece of adhesive polyethylene tape with a circular hole was positioned on the surface of the ceramic plate to control the cement layer (approximately 50 microm). The cement paste was placed on the ceramic surface within the circle. The ceramic plate with resin cement paste was placed on a clear micro cover glass over a zirconia ceramic block to obtain a flat surface, and the material was polymerized using a visible-light-curing unit. The surface hardness was recorded at a series of time intervals up to 5 days, starting from the end of a light-irradiation period. The hardness steadily increased with post-irradiation time and tended towards a maximum, usually reached after 1 or 2 days. In all cases, the increase in hardness was relatively rapid over the first 30 minutes and continued at a lower rate thereafter. The dual-cured resin cement for each material showed a significantly higher hardness value than the light-cured resin cement irradiated either through or not through ceramics at all post-irradiation times. The resin cements cured through ceramic for each material were significantly less hard compared with those cured not through ceramics at all post-irradiation times.
    American journal of dentistry 11/2006; 19(5):303-7. · 1.06 Impact Factor
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    ABSTRACT: The purpose of this study was to evaluate the bond strength between four bonding systems (GC Ceramic Primer and Linkmax HV (CP+LM), Clapearl Bonding Agent and Clapearl DC (CBA+CL), Clearfil Mega Bond Porcelain Bonding kit and Panavia F2.0 (MB+PF), and RelyX Ceramic Primer and RelyX ARC (RC+RA)) and two machinable ceramics (Vitablocs Mark II, VMII and GN-I ceramic block, GNI). Shear bond strength was determined after 24-hour immersion in water or after thermocycling of 20,000 cycles. It was found that the post-thermocycling bond strength of each bonding system to VMII was significantly higher than that to GNI. VMII showed no significant differences between CP+LM, MB+PF, and CBA+CL--the values of which were higher than that of RC+RA. Regarding GNI, CP+LM showed the greatest bond strength after thermocycling among the four bonding systems used. It was concluded that the crystalline phase of the ceramics used might have an effect on bond strength.
    Dental Materials Journal 10/2006; 25(3):621-5. · 0.81 Impact Factor
  • Xiangfeng Meng, Keiichi Yoshida, Mitsuru Atsuta
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    ABSTRACT: This study investigated the Knoop hardness of a thin layer in three dual-cured resin cements (Linkmax HV, Nexus 2, and Variolink II HV) irradiated through or not through different thicknesses (1 through 5 mm) of a machinable ceramic. Hardness was recorded at a series of time intervals up to five days, starting from the end of a light irradiation period. Increase in hardness was more rapid over the first 0.5 hour; thereafter it continued at a low rate until maximum hardness was attained. Ceramic thickness had a significant influence on hardness in all dual-cured resin cements, especially when ceramic thickness was more than 4 mm. In addition, it was noted that the polymerization of Nexus 2 seemed to be more dependent on light exposure compared with the other two materials. Variolink II HV and Linkmax HV, on the other hand, seemed to indicate the potential of being compensated by chemical curing to some degree.
    Dental Materials Journal 04/2006; 25(1):132-7. · 0.81 Impact Factor
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    Keiichi Yoshida, Yukiko Tsuo, Mitsuru Atsuta
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    ABSTRACT: This study evaluated the shear bond strength between dual-cured resin luting cement and pure zirconium (99.9%) and industrially manufactured yttrium-oxide-partially-stabilized zirconia ceramic, and the effect of MDP (10-methacryloyloxydecyl dihydrogen phosphate) primer (MP) and zirconate coupler (ZC) on bond strength. Two different-shaped pure zirconium and zirconia ceramic specimens were untreated or treated with various primers, including different concentrations of MP containing phosphoric acid ester monomer (MDP) in ethanol, ZC containing a zirconate coupling agent in ethanol, or a mixture of MP and ZC. The specimens were then cemented together with dual-cured resin luting cement (Clapearl DC). Half of the specimens were stored in water at 37 degrees C for 24 h and the other half were thermocycled 10,000 times before shear bond strength testing. The bond strengths of resin luting cement to both the zirconium and zirconia ceramic were enhanced by the application of most MPs, ZCs, and the mixtures of MP and ZC. For the group (MP2.0+ZC1.0) containing 2.0 wt % MP and 1.0 wt % ZC, no significant difference was observed between in shear bond strength before and after thermal cycling for both zirconium and zirconia ceramic (p > 0.05). For the other primers, statistically significant differences in shear bond strength before and after thermal cycling were observed (p < 0.05). The application of the mixture of MP and ZC (MP2.0+ZC1.0) was effective for bonding between zirconia ceramic and dual-cured resin luting cement. This primer may be clinically useful as an adhesive primer for zirconia ceramic restoration.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 04/2006; 77(1):28-33. · 2.31 Impact Factor
  • Keiichi Yoshida, Maki Yamashita, Mitsuru Atsuta
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    ABSTRACT: To evaluate the shear bond strength of two dual-cured resin luting cements (Linkmax HV and Panavia Fluoro Cement) to machinable glass-ceramics (Decsy Machinable Ceramic) and the effect of three silane coupling agents (Clearfil Porcelain Activator, Ceramic Primer, and Porcelain Liner M) on the bond strength. Disk-shaped specimens fabricated from machinable glass-ceramic blocks using a low-speed cutting saw were either treated or not treated with one of three silane coupling agents and then bonded together with one of two dual-cured resin luting cements. Specimens were stored in water at 37degrees C for 24 hours and/or thermal cycled 50,000 times before shear bond strength testing. Regardless of the resin luting cement and thermal cycling, specimens treated with the Clearfil Porcelain Activator showed the highest shear bond strength among all the treatments. Surface treatment of the Clearfil Porcelain Activator showed significantly greater shear bond strength after 50,000 thermocycles compared with other treatments. However, significant differences in bond strength were observed between 0 and 50,000 thermocycles for all treatments.
    American journal of dentistry 11/2005; 18(5):327-30. · 1.06 Impact Factor
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    ABSTRACT: To investigate the pre-clinical relevancy of a machinable composite, its physical properties were evaluated and compared with a machinable ceramic and two indirect composites. A machinable resin composite (GN-I composite, CO), a machinable ceramic (GN-I ceramic, CE), and two resin composites (Artglass dentin, AG; Estenia dentin, ET) were used. Compressive strength, diametral tensile strength, flexural strength, elastic modulus, and fracture load of standardized, premolar crown-shaped specimens were determined. In terms of compressive strength, diametral tensile strength, and flexural strength, AG showed significantly lower values than the other three materials. In terms of fracture load, specimens with 1.5 mm thick wall showed a higher value than those with 1.0 mm thick wall, and the value decreased in the order of ET, CE, CO, and AG. Marginal tipping was also observed in ET and CE. Within the limits of the current study, CO showed physical properties favorable for constructing esthetic restorations.
    Dental Materials Journal 04/2005; 24(1):24-9. · 0.81 Impact Factor
  • Keiichi Yoshida, Maki Yamashita, Mitsuru Atsuta
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    ABSTRACT: To evaluate the shear bond strengths of two dual-cured resin luting cements to pure zirconium and the effect of zirconate coupling agent on the bond strength. The two different-shaped pure zirconium specimens (99.9%) were untreated or treated with one of the four primers including zirconate coupler and then cemented together with one of the two dual-cured resin luting cements. Half of the specimens were stored in water at 37 degrees C for 24 hours and the other half thermocycled 20,000 times before shear bond strength testing. Regardless of the resin luting cement and thermocycling, specimens treated with the mixture of zirconate coupler and resin bonding agent showed the highest shear bond strength among the five treatments. Surface treatment with the mixture of zirconate coupler and resin bonding agent showed significantly greater shear bond strength compared with other treatments at 20,000 thermocycles. The application by the mixture of zirconate coupler and resin bonding agent on the pure zirconium metal surface appears to be effective for bonding between zirconium and dual-cured resin luting cements.
    American journal of dentistry 09/2004; 17(4):249-52. · 1.06 Impact Factor
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    ABSTRACT: The purpose of this study was to determine the flexural strength and flexural fatigue strength of a machinable composite (GN-I) and three hybrid composites (Artglass, Estenia, and Gradia). Specimens (2 x 2 x 25 mm) were polymerized in a laboratory photo-curing unit and then immersed in water at 37 degrees C for 24 h, 6 months, and 1 year. After each immersion period, flexural strengths (4-PFS) were measured at a cross-head speed of 1 mm/min in 4-point bending (span = 20 mm; distance between inside loading points = 10 mm). The cyclic fatigue test was performed at 2.0 Hz on a fatigue tester. The staircase method was employed for flexural fatigue strength (FFS) using a 5000 cyclic load limitation, 5-MPa stress increment, and 20 specimens for each material. Both 4-PFS and FFS of the machinable composite after all immersion periods were significantly greater than those of the three hybrid composites. The FFS results followed the same pattern as those of the 4-PFS. The Estenia material exhibited the highest 4-PFS and FFS after 24 h of immersion among three hybrid composites, whereas after 1 year of immersion, all three composites showed almost identical 4-PFS and FFS statistically. A strong correlation was observed between 4-PFS and FFS of the machinable composite and three hybrid resin composites.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 09/2004; 70(2):218-22. · 2.31 Impact Factor

Publication Stats

214 Citations
33.13 Total Impact Points

Institutions

  • 2014
    • Nagasaki University Hospital
      Nagasaki, Nagasaki, Japan
  • 1993–2011
    • Nagasaki University
      • • Department of Applied Prosthodontics
      • • Graduate School of Biomedical Sciences
      • • School of Dentistry
      Nagasaki, Nagasaki, Japan
  • 2008
    • Nanjing University
      Nan-ching, Jiangsu Sheng, China
  • 1998
    • Kagoshima University
      Kagosima, Kagoshima, Japan