Ikuya Watanabe

Nagasaki University, Nagasaki, Nagasaki, Japan

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Publications (96)157.56 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to investigate the cytotoxic effects of elements released from gold and CAD-CAM fabricated ceramic crowns.Materials and methodsAccording to the determination of elements released from gold alloy1 and CAD-CAM fabricated ceramic2 crowns into saliva of fixed prosthodontic patients by using inductively coupled plasma mass spectroscopy, similar amounts of elements (Au, Pd, Ag, Zn, Cu, Al, Si) were prepared as salt solutions. A well without any tested element was used as a negative control. These salt solutions were tested for cytotoxicity by culturing mouse L-929 fibroblasts for a 7-day period of incubation. Then, the percentage of viable cells for each element was measured using trypan blue exclusion assay. The data (n = 5) were statistically analyzed by ANOVA/Tukey test (p < 0.05).ResultsThe lowest percentage of viable cells (Mean ± SD) was evident with Zn and Cu released from gold crowns indicating that they are the most toxic elements. Ag was found to be intermediate in cytotoxic effect. Au, Pd, Al, Si were found to be the least cytotoxic elements.Conclusion Zn and Cu released from gold alloy full crowns showed evidence of prominent cytotoxic effect on fibroblasts cell cultures.
    Tanta Dental Journal. 11/2014;
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    ABSTRACT: Introduction This study investigated the surface, fractured structure, and physicochemical properties related to cyclic fatigue in various nickel-titanium (NiTi) files. Methods Among a total of 10 groups of NiTi files, conventional NiTi files (ProFile [Dentsply Maillefer, Ballaigues, Switzerland] and K3 [SybronEndo, Orange, CA]) and new-generation NiTi files (ProFile Vortex [PV; Tulsa Dental Specialties, Tulsa, OK], Vortex Blue [VB; Tulsa Dental Specialties], and K3 XF [XF; SybronEndo, Orange, CA]) with the same tip diameter (ISO size 25) and 2 types of taper (0.04 and 0.06) were used in this study. Scanning electron microscopy of the file surface structure, differential scanning calorimetry, and cyclic fatigue resistance tests were conducted. Results Many mechanical grooves were recognized on the file surface. The surface in the ProFile group was extremely smooth compared with that observed for the other files. Many shallow hollows besides mechanical grooves were noted on the surface in the XF group. A smooth curve was observed in the ProFile, K3, and PV groups. Defined peaks in differential scanning calorimetry were observed in the VB and XF groups. The 0.04 taper files exhibited a statistically higher number of cycles to fracture than the 0.06 taper files in all groups (P < .05). Cracks along the mechanical grooves were observed in the NiTi files, with the exception of the XF group. The start of cracking was detected at U-shape sites in the ProFile group, the cutting edge in the PV and VB groups, and radial islands in the K3 and XF groups. Conclusions The present findings suggest that new-generation NiTi files are not necessarily improved compared with conventional files.
    Journal of Endodontics. 09/2014;
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    ABSTRACT: This study compared biomechanical patterns between finite element models (FEM) and a fresh dog mandible tested under molar and incisal physiological loads in order to clarify the effect of the bone transport distraction osteogenesis surgical process. Three FEM of dog mandibles were built in order to evaluate the effects of bone transport distraction osteogenesis. The first model evaluated the mandibular response under two physiological loads resembling bite processes. In the second model, a 5.0 cm bone defect was bridged with a bone transport reconstruction plate (BTRP). In the third model, new regenerated bony tissue was incorporated within the defect to mimic the surgical process without the presence of the device. Complementarily, a mandible of a male American foxhound dog was mechanically tested in the laboratory both in the presence and absence of a BTRP, and mechanical responses were measured by attaching rosettes to the bone surface of the mandible to validate the FEM predictions. The relationship between real and predicted values indicates that the stress patterns calculated using FEM is a valid predictor of the biomechanics of the bone transport distraction osteogenesis procedures. The present study provides an interesting correlation between the stiffness of the device and the biomechanical response of the mandible affected for bone transport.
    Journal of biomechanical engineering. 08/2014;
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    ABSTRACT: We evaluated the influence of composition and powder/liquid (P/L) ratio on the setting characteristics and mechanical properties of autopolymerized hard direct denture reline resins composed of methyl methacrylate (MMA, monomethacrylate) and ethylene glycol dimethacrylate [EGDMA, dimethacrylate (cross-linking agent)], with poly (ethyl methacrylate) used as the powder, and a mixture of MMA and EGDMA containing p-tolyldiethanolamine as the monomer. Setting times were determined using an oscillating rheometer and mechanical properties were based on ISO specifications. Setting time increased exponentially with an increase in the ratio of EGDMA to MMA and decrease in P/L ratio. Materials with a liquid component of approximately 75-85 wt% EGDMA and a higher P/L ratio showed higher ultimate flexural strength and flexural modulus. Our results suggest that setting characteristics are more influenced by the ratio of monomethacrylate and cross-linking agent, whereas mechanical properties are more influenced by P/L ratio.
    Dental Materials Journal 07/2014; · 0.81 Impact Factor
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    ABSTRACT: Tricalcium silicate cements have been successfully employed in the biomedical field as bioactive bone and dentin substitutes, with widely acclaimed osteoactive properties. This research analyzed the effects of different tricalcium silicate cement formulations on the temporal osteoactivity profile of human bone marrow-derived mesenchymal stem cells (hMW-MSCs). These cells were exposed to 4 commercially-available tricalcium silicate cement formulations in osteogenic differentiation medium. After 1, 3, 7 and 10 days, quantitative real time-polymerase chain reaction and Western blotting were performed to detect the expression of target osteogenic markers ALP, RUNX2, OSX, OPN, MSX2, and OCN. After 3, 7, 14 and 21 days, alkaline phosphatase assay was performed to detect changes in intracellular enzyme level. Alizarin Red S assay was performed after 28 days to detect extracellular matrix mineralization. In the presence of tricalcium silicate cements, target osteogenic markers were downregulated at the mRNA and protein levels at all time-points. Intracellular alkaline phosphatase enzyme levels and extracellular mineralization of the experimental groups were not significantly different from the untreated control. Quantitative polymerase chain reaction results showed increases in downregulation of RUNX2, OSX, MSX2 and OCN with increase in time of exposure to the tricalcium silicate cements, while ALP showed peak downregulation at day 7. For Western blotting, OSX, OPN, MSX2 and OCN showed increased downregulation with increased exposure time to the tested cements. Alkaline phosphatase enzyme levels generally declined after day 7. Based on these results, it is concluded that tricalcium silicate cements do not induce osteogenic differentiation of hBM-MSCs in vitro.
    Acta biomaterialia 04/2014; · 5.68 Impact Factor
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    ABSTRACT: Objective: To nvestigate the possibility of electrical and laser welding to connect titanium-based alloy (beta-titanium and nickel-titanium) wires and stainless-steel or cobalt-chromium alloy wires for fabrication of combination arch-wires and to evaluate the joint strengths of connected alloy wires in tensile mode. Method: Four kinds of straight orthodontic rectangular wires (0.017 x 0.025 inch) were used: stainless-steel (S-S), cobalt-chromium (Co-Cr), beta-titanium alloy (β-Ti), and nickel-titanium (Ni-Ti). Homogeneous and heterogeneous end-to-end joints (15 mm long each) were made by electrical welding and laser welding. Non-welded wires (30 mm long) were also used as a control. Maximum loads at fracture (N) and elongation (%) were measured by conducting tensile test. The data (n=10) were statistically analyzed using analysis of variance/Tukey test (P<0.05). Result: When the electrical welding was used for homogeneous welding, the S-S/S-S and Co-Cr/Co-Cr specimens showed significantly higher values of the maximum load at fracture and elongation than those of the Ni-Ti/Ni-Ti and β-Ti/β-Ti specimens and those of the S-S/S-S and Co-Cr/Co-Cr specimens welded by laser. On the other hand, the laser-welded Ni-Ti/Ni-Ti and β-Ti/b-Ti specimens exhibited higher values of the maximum load at fracture and elongation compared to those of the corresponding specimens welded by electrical method. In the heterogeneously welded combinations, the electrically welded Ni-Ti/S-S, β-Ti/S-S and β-Ti/Co-Cr specimens showed significantly (P<.05) higher maximum loads at fracture and elongations than those of the corresponding specimens welded by laser. Conclusion: In homogeneous welding, laser welding indicated high value of maximum load at fracture and elongation for welding of titanium based alloy wires, whereas the S-S and Co-Cr alloy wires showed high load values when electrical welding was used. Electrical welding exhibited the higher values of maximum load at fracture and elongation for heterogeneously welded combinations than laser-welding.
    AADR Annual Meeting & Exhibition 2014; 03/2014
  • Source
    W. Elshahawy, I. Watanabe
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    ABSTRACT: Many different types of alloys are now available in the market to be used for dental restorations and fixed prostheses. The common criterion for all these fixed prosthodontic materials is the permanent existence of them in the oral cavity for prolonged time without the ability to be removed by the patient. Therefore, knowledge about the biocompatibility of dental alloys is of great importance. This article presents a literature review on the biocompatibility of dental alloys. A PubMed database search was conducted for studies pertaining to the biocompatibility of dental alloys. The search was limited to peer-reviewed articles published in English between 1985 and 2013. Available data revealed that substances are released from alloys into the surrounding tissues; mainly nickel, zinc, and copper. Some alloys such as nickel–chromium alloy have shown to be cytotoxic in vitro. Also, elements released from gold alloy showed in vitro cytotoxic effect. Therefore, clinicians should give up assuming that gold alloy is completely inert and biocompatible with oral tissues. The clinical relevance of these findings remains unclear. Further in vitro studies, as well as controlled clinical trials, are needed due to possible exceptions.
    Tanta Dental Journal. 01/2014;
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    ABSTRACT: Bone transport distraction osteogenesis (BTDO) is a surgical procedure that has been used over the last 30 years for the correction of segmental defects produced mainly by trauma and oncological resections. Application of BTDO has several clinical advantages over traditional surgical techniques. Over the past few years, several BTDO devices have been introduced to reconstruct mandibular bone defects. Based on the location and outline of the defect, each device requires a uniquely shaped reconstruction plate. To date, no biomechanical evaluations of mandibular BTDO devices have been reported in the literature. The present study evaluated the mechanical behavior of three different shaped prototypes of a novel mandibular bone transport reconstruction plate and its transport unit for the reconstruction of segmental bone defects of the mandible by using numerical models complemented with mechanical laboratory tests to characterize strength, fatigue, and stability. The strength test evaluated device failures under extreme loads and was complemented with optimization procedures to improve the biomechanical behavior of the devices. The responses of the prototypes were characterized to improve their design and identify weak and strong regions in order to avoid posterior device failure in clinical applications. Combinations of the numerical and mechanical laboratory results were used to compare and validate the models. In addition, the results remark the importance of reducing the number of animals used in experimental tests by increasing computational and in vitro trials.
    Journal of Medical Devices-Transactions of the Asme. 01/2014; 8(2).
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    ABSTRACT: The purpose of this study was to evaluate and compare the bond strengths between resin composite veneer and laser-sintered cobalt-chromium (Co-Cr) alloy with and without retention devices (Laser-R and Laser-N respectively). Cast Co-Cr alloy with and without retention devices (Cast-R and Cast-N respectively) were also prepared for fabrication technique comparison. Disk-shaped Co-Cr alloy specimens were air-abraded with alumina and veneered with a veneering system, Estenia C&B (ES) or Ceramage (CE). After 20,000 thermocycles, tensile testing was performed. Data were analyzed by ANOVA and multiple comparison test. When no retention devices were present, no significant differences were observed between Laser-N/ES and Cast-N/ES, or between Laser- N/CE and Cast-N/CE, but ES exhibited significantly higher bond strength than CE. With retention devices, Laser-R/ES, Cast- R/ES and Laser-R/CE showed no significant differences, and their retention strengths were significantly higher than that of Cast- R/CE. Compared to cast Co-Cr alloy, laser-sintered Co-Cr alloy with retention devices provided better retention durability for resin composite-veneered prostheses.
    Dental Materials Journal 11/2013; · 0.81 Impact Factor
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    ABSTRACT: Objectives: This study evaluated the marginal accuracy of cast titanium using a three-unit fixed partial denture (FPD). Methods: A two-abutment stainless-steel die was used to duplicate a set made of a stone die and an epoxy master die. The FPD wax pattern made on a stone die was invested in a mold. Commercially pure titanium (Titanium Ind., Rockaway, NJ) was cast using a centrifugal casting unit in a magnesia mold. As controls, nickel-chromium (Talladium, Valencia, CA) and gold alloys (Tokuriki Honten, Tokyo, Japan) were cast centrifugally into phosphate and cristobalite molds, respectively. Overall burnout schedules followed manufacturers' instructions. Each casting was luted to the epoxy die under a 2 kgf static load. The luted assembly was cut longitudinally at the center of the casting. The clearance between the die and the casting was measured at different measurement locations along the cervical shoulder, and data (μm) for the exterior or the interior shoulders (n= 4 bridges; 8 shoulders) were averaged in terms of the vertical gap (VG) and the horizontal discrepancy (HD), then were statistically analyzed by ANOVA/Tukey test (P <0.05). Results: The VG and HD values of the titanium specimens showed less marginal accuracy compared to the others at all measurement locations of the exterior shoulders. However, there was no statistical difference (P > 0.05) among the cast metals at the interior shoulder except at I-J location (Horizontal Discrepancy) in which all the horizontal discrepancy values were negative. Conclusions: Using a magnesia investment, marginal accuracy of cast titanium was evident to be less than that of conventional alloys of simulated FPD restoration. The correlation between thermal expansion and titanium bridge accuracy is still high.
    09/2013
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    ABSTRACT: Calcium aluminosilicate cements are fast-setting, acid-resistant, bioactive cements that may be used as root-repair materials. This study examined the osteogenic/dentinogenic potential of an experimental calcium aluminosilicate cement (Quick-Set) by using a murine odontoblast-like cell model. Quick-Set and white ProRoot MTA (WMTA) were mixed with the proprietary gel or deionized water, allowed to set completely in 100% relative humidity, and aged in complete growth medium for 2 weeks until rendered non-cytotoxic. Similarly aged Teflon disks were used as negative control. The MDPC-23 cell line was used for evaluating changes in mRNA expressions of genes associated with osteogenic/dentinogenic differentiation and mineralization (quantitative reverse transcription polymerase chain reaction), alkaline phosphatase enzyme production, and extracellular matrix mineralization (alizarin red S staining). After MDPC-23 cells were incubated with the materials in osteogenic differentiation medium for 1 week, both cements showed up-regulation in ALP and DSPP expression. Fold increases in these 2 genes were not significantly different between Quick-Set and WMTA. Both cements showed no statistically significant up-regulation/down-regulation in RUNX2, OCN, BSP, and DMP1 gene expression compared with Teflon. Alkaline phosphatase activity of cells cultured on Quick-Set and WMTA were not significantly different at 1 week or 2 weeks but were significantly higher (P < .05) than Teflon in both weeks. Both cements showed significantly higher calcium deposition compared with Teflon after 3 weeks of incubation in mineralizing medium (P < .001). Differences between Quick-Set and WMTA were not statistically significant. The experimental calcium aluminosilicate cement exhibits similar osteogenic/dentinogenic properties to WMTA and may be a potential substitute for commercially available tricalcium silicate cements.
    Journal of endodontics 09/2013; 39(9):1161-6. · 2.95 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the proper time to restore composite resin over mineral trioxide aggregate (MTA). Thirty-five samples of MTA blocks were divided into 7 groups with 3 different times (10 minutes, 1 day, and 7 days) selected for restoring the composite resin over MTA with and without bonding resin, and a control group was included for comparison. After 21 days, the distances between MTA and the composite resin or between MTA and the bonding agent on sectioned planes along the long axis were measured using a scanning electron microscope (×2,000 magnification). The hardness of the MTA near the composite resin was presented as the Vickers microhardness. There were no gaps at the interface in the 10-minute groups, the 1-day group with a bonding agent, and the 7-day group with a bonding agent. The groups without a bonding agent at 1 and 7 days presented a separation or gap at the interface. The value of the Vickers microhardness in the 1-day groups was significantly decreased compared with those of the other groups regardless of the presence or absence of a bonding agent. These findings suggest that composite resin with a bonding agent over MTA can be restored almost immediately after MTA mixing during a single visit.
    Journal of endodontics 09/2013; 39(9):1167-70. · 2.95 Impact Factor
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    ABSTRACT: CPoint is a polymeric endodontic point that takes advantage of water-induced, non-isotropic radial expansion to adapt to canal irregularities. This study evaluated the effects of CPoint on the viability and mineralization potential of odontoblast-like cells. The biocompatibility of CPoint and commercially available gutta-percha points was evaluated by using a rat odontoblast-like cell line (MDPC-23). Cell viability was evaluated with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry, and confocal laser scanning microscopy. The mineralization potential of MDPC-23 cells, in the presence of the root-filling materials, was evaluated by examining the changes in osteogenic gene marker expression (quantitative real-time polymerase chain reaction), alkaline phosphatase activity, alizarin red S assay, and transmission electron microscopy. CPoint showed higher initial cytotoxicity compared with gutta-percha and Teflon (P < .05), which became nonsignificant after 4 immersion cycles. Significant differences were also found between eluents from CPoint and gutta-percha at 1:1 concentration (P < .05) but not at 1:10 or 1:100 concentration. Both materials induced minimal apoptosis-induced alteration in plasma membrane permeability, as evidenced by flow cytometry and confocal laser scanning microscopy. Compared with the Teflon negative control, CPoint and gutta-percha groups showed up-regulation of most osteogenic gene markers except for dentin sialophosphoprotein, which was down-regulated. Alkaline phosphatase activity and alizarin red assay for CPoint and gutta-percha were both significantly higher than for Teflon but not significantly different from each other (P > .05). Transmission electron microscopy showed discrete nodular electron-dense mineralization foci in all 3 groups. The in vitro biocompatibility of CPoint is comparable to gutta-percha with minimal adverse effects on osteogenesis after elution of potentially toxic components.
    Journal of endodontics 07/2013; 39(7):883-8. · 2.95 Impact Factor
  • T. ODATSU, I. WATANABE, T. SAWASE
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    ABSTRACT: Objective: The purpose of this study was to investigate the effect of surface polishing and finishing methods on the surface roughness of restorative ceramics. Method: Disk specimens were prepared from feldspar-based, lithium disilicate-based, fluorapatite leucite-based and zirconia ceramics. Four kinds of surface polishing and finishing methods evaluated were: Group 1 (CP: Carborundum Points; Control); Group 2 (SP: Silicone Points); Group 3 (DP: Diamond Paste); Group 4 (GZ: Glazing). Surface roughness was measured using an interferometer and the parameters of Sa (average height deviation of the surface) and St (maximum peak-to-valley height of the surface) were evaluated. Data were statistically analyzed using two-way analysis of variance (p<0.05). The specimen surfaces were evaluated by 3-D images using an interferometer. Result: The significantly lowest Sa values and St values were obtained for lithium disilicate-based and zirconia ceramics finished with DP and GZ. The fluorapatite leucite-based ceramic showed significantly reduced Sa and St values from DP to GZ. The feldspar-based ceramic showed the highest surface roughness values among all types of ceramics after any polishing and finishing procedure. 3-D images of the feldspar-based ceramic showed most scabrous surfaces with pores among all types of ceramics. The surfaces of lithium disilicate-based and fluorapatite leucite-based ceramic showed a few pores and defects, and were much smoother as compared to the feldspar-based ceramic. The zirconia surface finished by DP still showed the remaining scratches induced by polishing with carborundum points. However, these scratches disappeared after finishing with GZ. Conclusion: The results obtained in this study indicated that the lithium disilicate-based and zirconia ceramics finished with DP and GZ produce the smoother surface, and the surface textures of restorative ceramics were different from each other.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
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    ABSTRACT: Objective: This study investigated the frictional forces of aesthetically coated orthodontic wires through two types of ceramic brackets. Method: Four types of rectangular orthodontic wires (0.019 x 0.025 inches), nickel-titanium (Ni-Ti), stainless steel (SS), Ni-Ti coated with TiO2+SiO2 (C-Ni-Ti) and SS coated with epoxy (C-SS) were used to measure the frictional forces through two types of ceramic brackets: metal-reinforced bracket (Clarity TM) with elastic ligation (0.12mm) and self-ligating bracket (CLIPPY-C) with a slot dimension of 0.022 inch. The coated wires display white teeth color. After each wire was set into each bracket, frictional forces (N) were measured during 5 mm slide in the bracket set on a device at two bracket-wire angulations (0° and 10º) using an universal testing machine at a cross-head speed of 10 mm/min. For each wire/bracket combination, static friction forces were recorded (n=8). The results were statistically analyzed by Mann-Whitney U-tests (p<0.05). Result: For both Ni-Ti and SS wires, the frictional forces (2.00N-4.29N) slid in the metal-reinforced ceramic bracket showed the higher fractional forces than those (0.97N-2.04N) in the ceramic self-ligating bracket at any bracket-wire angulation. Furthermore, aesthetical coating reduced frictional force when both wires were set in the metal-reinforced ceramic brackets (Clarity TM) at a bracket-wire angulation of 0º. All of the wire-bracket combinations measured at a bracket-wire angulation of 10º had the higher frictional forces than those measured at 0° except for a combination of C-Ni-Ti and self-ligating bracket (CLIPPY-C), which demonstrated similar values (approx. 1N) of fractional force (no statistical difference). The highest difference in frictional force was observed in a combination of C-SS and metal-reinforced bracket (Clarity TM). Conclusion: Aesthetical coating on nickel-titanium and stainless steel wires reduced the frictional forces when the wires were slid through the metal-reinforced ceramic brackets (Clarity TM) without bracket-wire angulation.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
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    ABSTRACT: Objective: The objective of this study was to evaluate the effect of four primers and a self-curing adhesive resin on shear bond strength of a veneering resin composite to Ce-TZP/Al2O3 nanocomposite (NANOZR, Panasonic healthcare). Methods: Four primers used were M.L. Primer (Shofu, ML), AZ Primer (Shofu, AZ), Alloy Primer (Kuraray Noritake Dental, AP), Clearfil Ceramic Primer (Kuraray Noritake Dental, CP). Disk shaped NANOZR specimens (10 mm in diameter by 2.5 mm thick) were ground with #600 silicon carbide paper, air-abraded with 50 µm alumina, and primed. After a piece of making tape and an acrylic mold were put on the specimen, a series of veneering pastes (Pre-opaque, Opaque, Body composites) of Ceramage (Shofu Inc.) were applied on it, and then light polymerized. As experimental groups, a self-curing adhesive resin (Super Bond C&B Opaque Ivory Sun-Medical, SB) was used instead of the Pre- opaque paste. The veneered specimens were stored in distilled water at 37°C for 24 hour. Shear bond strengths were determined using a universal testing machine. Data were statistically analyzed by ANOVA and a multiple comparison test (α=0.05). Results: Mean shear bond strengths of ten specimens were ML/PO, 10.1 MPa; AZ/PO, 10.6 MPa; AP/PO, 9.6 MPa; CP/PO, 13.5 MPa; ML/SB, 21.0 MPa; AZ/SB, 22.9 MPa; AP/SB, 23.5 MPa; CP/SB, 25.3 MPa. When Pre-opaque was used, no significant differences were observed among ML, AZ, AP, and CP. ML/SB, AZ/SB, AP/SB and CP/SB showed significantly higher bond strengths than ML, AZ, AP and CP, respectively. Conclusion: It is concluded that and SB improved the shear bond strength of veneering resin composite on the Ce-TZP/Al2O3 nanocomposite material, in cooperation with the primer used.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
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    ABSTRACT: The objective of this study was to quantitatively investigate the elemental ion release from the fixed gold alloy and ceramic crowns into patient saliva. Twenty patients who participated in the study were divided into two equal groups; 1) full coverage type IV gold crowns and 2) full coverage CAD-CAM-fabricated ceramic crowns. Saliva collection and clinical evaluation of marginal integrity and gingival health were performed before crowns preparation, 3 months and 6 months after crowns placement. Clinical evaluations were conducted using California Dental Association criteria. Collected saliva samples were analysed for element release using inductively coupled plasma mass spectrometer. The zinc, copper, palladium, gold and silver were released from type IV gold crowns into saliva, while the silicon and aluminium were released from ceramic crowns. A clinically significant number of subjects had increased release of zinc from baseline to three-month recall and increased silicon release from baseline to both three-month and six-month recalls. For all elements, the subjects' counts for the case of three-month recall to six-month recall were never higher than that of the case of baseline to three-month recall except for palladium. No obvious adverse effects on marginal integrity or gingival health were noticed. Significant increased releases of zinc from cast gold crowns and silicon from CAD-CAM-fabricated ceramic crowns into the saliva were evident after 3 months of clinical service.
    Journal of Oral Rehabilitation 02/2013; · 2.34 Impact Factor
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    ABSTRACT: To investigate the effect of surface polishing and finishing methods on the surface roughness of restorative ceramics. Disk specimens were prepared from feldspar-based, lithium disilicate-based, fluorapatite leucite-based and zirconia ceramics. Four kinds of surface polishing/finishing methods evaluated were: Group 1: Control: carborundum points (CP); Group 2: silicon points (SP); Group 3: diamond paste (DP); Group 4: glazing (GZ). Surface roughness was measured using an interferometer and the parameters of Sa (average height deviation of the surface) and St (maximum peak-to-valley height of the surface) were evaluated. Data were statistically analyzed using two-way ANOVA (P < 0.05) followed by post-hoc test. The mean values were also compared by Student's t-test. Specimen surfaces were evaluated by 3-D images using an interferometer. The zirconia showed the least surface roughness (Sa and St) values after grinding with carborundum points. The significantly lowest Sa values and St values were obtained for lithium disilicate and zirconia ceramics surfaces finished with DP and GZ. The fluorapatite leucite ceramic showed significantly reduced Sa and St values from DP to GZ. The feldspathic porcelain showed the highest surface roughness values among all types of ceramics after all of the polishing/finishing procedures.
    American journal of dentistry 02/2013; 26(1):51-5. · 1.06 Impact Factor
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    ABSTRACT: This study evaluated the effects of the fluorinated monomer of 2,2,2-trifluoroethyl methacrylate (TFEMA) on the properties of autopolymerized hard direct denture reline resins. Iso-butyl methacrylate (i-BMA) and 2-hydroxyethyl methacrylate (2-HEMA) containing 30% TFEMA by weight were used as monomers, while poly(ethyl methacrylate) was used as a powder. Setting characteristics, dynamic mechanical properties, and changes over time, as well as wettability were determined by use of an oscillating rheometer, dynamic viscoelastometer, and contact angle meter. Water absorption and solubility were also measured according to ISO specifications. The reline resin based on i-BMA had greater elasticity and stiffness properties, while that based on 2-HEMA showed fewer dynamic mechanical property changes over time with the addition of TFEMA. Furthermore, water absorption and solubility tended to be reduced and contact angle increased. The results of this study suggest that TFEMA improves mechanical properties and durability of reline resins over time.
    Dental Materials Journal 01/2013; 32(5):744-752. · 0.81 Impact Factor
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    ABSTRACT: Mineral trioxide aggregate (MTA) has been used successfully for perforation repair, vital pulpotomies, and direct pulp capping. However, little is known about the interactions between MTA and glass ionomer cement (GIC) in final restorations. In this study, 2 null hypotheses were tested: (1) GIC placement time does not affect the MTA-GIC structural interface and hardness and (2) moisture does not affect the MTA-GIC structural interface and hardness. Fifty cylinders were half filled with MTA and divided into 5 groups. The other half was filled with resin-modified GIC either immediately after MTA placement or after 1 or 7 days of temporization in the presence or absence of a wet cotton pellet. The specimens were then sectioned, carbon coated, and examined using a scanning electron microscope and an electron probe microanalyzer (SEM-EPMA) for interfacial adaptation, gap formation, and elemental analysis. The Vickers hardness numbers of the interfacial MTA were recorded 24 hours after GIC placement and 8 days after MTA placement and analyzed using the analysis of variance test. Hardness testing 24 hours after GIC placement revealed a significant increase in hardness with an increase of temporization time but not with a change of moisture conditions (P < .05). Hardness testing 8 days after MTA placement indicated no significant differences among groups. SEM-EPMA showed interfacial adaptation to improve with temporization time and moisture. Observed changes were limited to the outermost layer of MTA. The 2 null hypotheses were not rejected. GIC can be applied over freshly mixed MTA with minimal effects on the MTA, which seemed to decrease with time.
    Journal of endodontics 08/2012; 38(8):1126-9. · 2.95 Impact Factor

Publication Stats

810 Citations
157.56 Total Impact Points

Institutions

  • 1994–2014
    • Nagasaki University
      • • Department of Dental and Biomedical Materials Science
      • • Department of Applied Prosthodontics
      • • School of Dentistry
      Nagasaki, Nagasaki, Japan
  • 2013
    • Tanta University
      • Faculty of Dentistry
      Tanda, Muhafazat al Gharbiyah, Egypt
  • 1999–2011
    • Baylor College of Dentistry
      • • Division of Biomaterials Science
      • • Department of Endodontics
      Dallas, Texas, United States
  • 2007
    • Kagawa University
      • Faculty of Engineering
      Takamatsu-shi, Kagawa-ken, Japan
  • 2000–2006
    • Tsurumi University
      • Department of Removable Prosthodontics
      Yokohama, Kanagawa, Japan
  • 2005
    • Texas A&M University System Health Science Center
      Bryan, Texas, United States