Biomedical subjects

M Atsuta

Publications and source records attributed to M Atsuta.

At least 55 records · Page 3Linked to original sources

PubMed2001

Bonding of prosthetic composite material to Ti-6Al-7Nb alloy with eight metal conditioners and a surface modification technique.

PURPOSE: The purpose of the current study was to evaluate the adhesive performance of metal conditioners and a surface modification system when used for bonding between a prosthetic composite material and a titanium alloy. MATERIALS AND METHODS: Eight metal conditioners (Acryl Bond, All-Bond 2 Primer B, Alloy Primer, Ces II Opaque Primer, Eye Sight Opaque Primer, Metafast Bonding Liner, Metal Primer II, and MR Bond) and a bonding system (Siloc) were assessed. Cast disk specimens made of a titanium alloy (Ti-6Al-7Nb, T-Alloy Tough) were either primed with one of the eight primers or treated with the Siloc system and bonded with a light-activated prosthetic composite material (Artglass). Shear bond strengths were determined both before and after thermocycling (4 C-60 C, 60 s each, 20,000 cycles) for evaluation of the durability of the bonds. RESULTS: The results showed that the Siloc-treated group recorded the greatest post-thermocycling bond strength, followed by the two groups conditioned with the Cesead II Opaque Primer and Alloy Primer agents, both of which contain an identical hydrophobic phosphate-methacrylate functional monomer.

Alkanes↗

PubMed2000

Characterization of rat OX40 ligand by monoclonal antibody.

OX40 (CD134) is a member of the tumor necrosis factor (TNF) receptor superfamily first identified as a rat T cell activation marker. We previously identified the rat ligand for OX40 (OX40L) by molecular cloning. In the present study, we newly generated an anti-rat OX40L mAb (ATM-2) that can inhibit the binding of OX40 to rat OX40L and thus efficiently inhibits the T cell costimulatory activity of rat OX40L. Flow cytometric analyses using ATM-2 and an anti-rat OX40 mAb (MRC OX40) indicated that OX40 was inducible on splenic CD4(+) T cells by stimulation with immobilized anti-CD3 mAb, while OX40L was not expressed on resting or activated T cells. OX40L was expressed on splenic B cells after stimulation with lipopolysaccharide (LPS), but not on peritoneal macrophages. Interestingly, splenic dendritic cells (DC) expressed OX40L constitutively, which was further upregulated by LPS stimulation. The potent costimulatory activities of splenic DC for anti-CD3-stimulated rat CD4(+) T cell proliferation and cytokine (IL-2, IFN-gamma, IL-10, and IL-13) production were substantially inhibited by ATM-2. These results indicated that OX40L is expressed on professional antigen-presenting cells (APC), and may be involved in humoral immune responses via T-B interaction and in cellular immune responses via T-DC interaction in the rat system.

Animals↗

PubMed2000

CD27-mediated activation of murine NK cells.

CD27, a member of the TNF receptor superfamily, has been implicated in T cell activation, T cell development, and T cell-dependent Ab production by B cells. In the present study we examined the expression and function of CD27 on murine NK cells. Murine NK cells constitutively expressed CD27 on their surface. Stimulation with immobilized anti-CD27 mAb or murine CD27 ligand (CD70) transfectans solely could induce proliferation and IFN-gamma production of freshly isolated NK cells and enhanced the proliferation and IFN-gamma production of anti-NK1.1-sutimulated NK cells. Although NK cell cytotoxicity was not triggered by anti-CD27 mAb or against CD70 transfectants, prestimulation via CD27 enhanced the cytotoxic activity of NK cells in an IFN-gamma-dependent manner. These results suggest that CD27-mediated activation may be involved in the NK cell-mediated innate immunity against virus-infected or transformed cells expressing CD70.

Adjuvants, Immunologic↗

PubMed2000

Critical contribution of OX40 ligand to T helper cell type 2 differentiation in experimental leishmaniasis.

Infection of inbred mouse strains with Leishmania major is a well characterized model for analysis of T helper (Th)1 and Th2 cell development in vivo. In this study, to address the role of costimulatory molecules CD27, CD30, 4-1BB, and OX40, which belong to the tumor necrosis factor receptor superfamily, in the development of Th1 and Th2 cells in vivo, we administered monoclonal antibody (mAb) against their ligands, CD70, CD30 ligand (L), 4-1BBL, and OX40L, to mice infected with L. major. Whereas anti-CD70, anti-CD30L, and anti-4-1BBL mAb exhibited no effect in either susceptible BALB/c or resistant C57BL/6 mice, the administration of anti-OX40L mAb abrogated progressive disease in BALB/c mice. Flow cytometric analysis indicated that OX40 was expressed on CD4(+) T cells and OX40L was expressed on CD11c(+) dendritic cells in the popliteal lymph nodes of L. major-infected BALB/c mice. In vitro stimulation of these CD4(+) T cells showed that anti-OX40L mAb treatment resulted in substantially reduced production of Th2 cytokines. Moreover, this change in cytokine levels was associated with reduced levels of anti-L. major immunoglobulin (Ig)G1 and serum IgE. These results indicate that anti-OX40L mAb abrogated progressive leishmaniasis in BALB/c mice by suppressing the development of Th2 responses, substantiating a critical role of OX40-OX40L interaction in Th2 development in vivo.

4-1BB Ligand↗

PubMed2000

Cutting efficiency of air-turbine burs on cast titanium and dental casting alloys.

OBJECTIVE: The purpose of this study was to investigate the cutting efficiency of air-turbine burs on cast free-machining titanium alloy (DT2F) and to compare the results with those for cast commercially pure (CP) Ti, Ti-6Al-4V alloy, and dental casting alloys. METHODS: The cast metal (DT2F, CP Ti, Ti-6Al-4V, Type IV gold alloy and Co-Cr alloy) specimens were cut with air-turbine burs (carbide burs and diamond points) at air pressures of 138 or 207 kPa and a cutting force of 0.784 N. The cutting efficiency of each bur was evaluated as volume loss calculated from the weight loss cut for 5 s and the density of each metal. The bulk microhardness was measured to correlate the machinability and the hardness of each metal. RESULTS: The amounts of DT2F cut with the carbide burs were significantly (p < 0.05) greater than for the other titanium specimens at either 138 or 207 kPa. The diamond points exhibited similar machining efficiency among all metals except for Type IV gold alloy. The increase in the volume loss of Co-Cr alloy (Vitallium) cut with the diamond points showed a negative value (-29%) with an increase in air pressure from 138 to 207 kPa. There was a negative correlation between the amounts of metal removed (volume loss) and the hardness (r2 = 0.689) when the carbide burs were used. SIGNIFICANCE: The results of this study indicated that a free-machining titanium alloy (DT2F) exhibited better machinability compared to CP Ti and Ti-6Al-4V alloy when using carbide fissure burs. When machining cast CP Ti and its alloys, carbide fissure burs possessed a greater machining efficiency than the diamond points and are recommended for titanium dental prostheses.

Alloys↗

PubMed2000

Analysis of composite type and different sources of polymerization light on in vitro toothbrush/dentifrice abrasion resistance.

OBJECTIVES: This study examined toothbrush/dentifrice abrasion of a photo-activated prosthetic composite (dentin and enamel variations) for the purpose of evaluating the influence of polymerization sources on abrasive wear. METHODS: A photo-activated prosthetic composite material (Artglass) was assessed. Dentin and enamel variations were polymerized using a proprietary photo-curing unit with two xenon stroboscopic lamps (UniXS), and other enamel specimens were polymerized either with a laboratory photo-curing unit with three fluorescent tubes or with a high intensity unit with two metal halide lamps. All specimens were stored in water for 14days and subjected to toothbrush/dentifrice abrasion (350g vertical load) using an abrasive slurry (Colgate Fluoriguard) and a toothbrush (Oral-B 40). The amount of vertical loss and the surface roughness of the specimens after 20,000 strokes were determined by profilometer. Average values of groups of five specimens were compared using analysis of variance (ANOVA) and Sheffe's S intervals (p<0.05). RESULTS: When polymerizing with the proprietary unit, the abrasion and surface roughness of the enamel material required respective means of 34.08microm (+/-3.66) and 1.00microm (+/-0.08), and the those of the dentin material required means of 42.02microm (+/-5.62) and 1.23microm (+/-0.20). Both abrasion and surface roughness after toothbrushing of the enamel material were significantly smaller than were those of the dentin material. The abrasion of specimens polymerized with the metal halide unit required a mean of 23.89microm (+/-6.17) and demonstrated minimal wear. CONCLUSIONS: The use of a high intensity metal halide photo-curing unit effectively enhanced the abrasion resistance of the composite. Surfaces of restorations should be covered with the enamel material in order to achieve smoothness and wear resistance.

Analysis of Variance↗

PubMed2000

Effect of thione primers on bonding of noble metal alloys with an adhesive resin.

OBJECTIVES: The purpose of the current study was to evaluate the effects of two metal conditioners on the bond durability of an adhesive resin joined to noble metal alloys by comparing pre- and post-thermocycling bond strengths. METHODS: Two different sizes of disk specimens (10 and 8mm in diameter by 2.5mm thickness) were prepared from silver-indium (Ag-In-Zn, Salivan), silver-palladium-copper-gold (Ag-Pd-Cu, Castwell M.C.12), metal-ceramic gold (Au-Pt-Pd, Degudent-Universal), metal-ceramic palladium (Pd-Ga-Co, PTM 88), type IV gold (type IV, Casting Gold) alloys, and pure silver (pure Ag). The specimens were air-abraded with 50-microm grain sized alumina, conditioned either with a thiouracil primer (Metaltite) or with a thione-phosphate primer (Alloy Primer), then bonded with an adhesive resin (Super-Bond Opaque). Shear bond strengths were determined both before and after repeated thermocycling (4 degrees C and 60 degrees C, 1min each, 100, 000cycles). The results were compared by analysis of variance and post-hoc multiple comparison intervals. RESULTS: The average post-thermocycling bond strengths in MPa (n=8) generated with the thiouracil primed and thione-phosphate primed groups, respectively, were: 3.4 and 5.8 for the Ag-In-Zn alloy, 40.4 and 37.7 for the Ag-Pd-Cu alloy, 26.4 and 33.5 for the Au-Pt-Pd alloy, 27.4 and 36.6 for the Pd-Ga-Co alloy, 40.2 and 40.3 for the type IV alloy, and 37.3 and 32.4 for the pure Ag. The Ag-In-Zn alloy exhibited significantly lower bond strength than the other alloys, whereas the Ag-Pd-Cu and type IV alloys exhibited the greatest magnitude of bond strength for both primers (p<0.05). CONCLUSIONS: It can be concluded that the combined use of either of the two thione primers and the adhesive resin is effective for bonding the metal/alloys examined, with the exception of the Ag-In-Zn alloy.

Adhesiveness↗

PubMed2000

Adhesive bonding of titanium with a thione-phosphate dual functional primer and self-curing luting agents.

A consistent bond between the metal framework and the luting agent is desired when resin-bonded prostheses are constructed with titanium. The purpose of this study was to evaluate three different metal primers on titanium bonding. Two sources of titanium (machined 99.9% titanium and cast Titan Ingot JS2) were used. Disk specimens were bonded with eight combinations of three primers and two luting agents (Panavia 21 and Super-Bond C&B), including two controls. Shear bond strengths were determined after 24-h water storage and after 10,000 cycles of thermocycling. Bond strengths were influenced by thermocycling, primer, luting agent and their combinations, but no significant differences were found between the machined 99.9% titanium and the cast ingot. The thione-phosphate dual functional primer (Alloy Primer) was comparable to the phosphate primer (Cesead II Opaque Primer) and the thiophosphate primer (Metal Primer II) for bonding the titanium metals examined. The most durable bond was obtained in three combinations of these primers and one luting agent (Super-Bond C&B).

Analysis of Variance↗

PubMed2000

Effect of etching and sandblasting on bond strength to sintered porcelain of unfilled resin.

This study determined the bond strength of an unfilled resin joined to a feldspathic porcelain for the purpose of evaluating the retentive performance of the prepared material surfaces. Porcelain disks (VMK 68 dentin) were either air abraded with alumina (AAA) or etched with one of the following five etchants: (1) ammonium hydrogen bifluoride (AHB); (2) acidulated phosphate fluoride (APF); (3) hydrofluoric acid (HFA); (4) phosphoric acid (PHA); and (5) sulfuric acid-hydrofluoric acid (SHF). Specimens ground with abrasive paper were also used as controls. After surface preparation, the two different sized porcelain disks were bonded together with a methyl methacrylate-based resin initiated with tri-n-butylborane (MMA-TBB resin). Shear bond strengths were determined both before and after thermocycling. Before the thermocycling, the greatest bond strengths (21.3 and 23.7 MPa) were generated with the use of the SHF and HFA agents, followed by the AHB agent (18.4 MPa). Reduction in bond strength after thermocycling was significant for all groups, although the SHF- and HFA-treated groups exhibited bond strengths greater than 15 MPa even after the thermocycling. The results indicated the effectiveness of the SHF- or HFA-etching for retaining the acrylic resin to the porcelain. However, ageing testing also revealed insufficient retentive characteristics of the acrylic resin by etching alone.

Acid Etching, Dental↗

PubMed2000

Comparative evaluation of secondary heat treatment and a high intensity light source for the improvement of properties of prosthetic composites.

This study determined the hardness and water solubility of two prosthetic composites polymerized with three curing modes for the purpose of evaluating the influence of secondary heating and a high intensity light source on resulting material properties. Two prosthetic composite materials (Artglass and Dentacolor) were cured with the following methods: (1) exposure by means of a photo-curing unit with a xenon stroboscopic light source (Dentacolor XS) for 120 s; (2) exposure with the xenon unit for 120 s, followed by heating in an oven (KL 100) at 100 degrees C for 15 min; and (3) exposure by means of a photo-curing unit with two metal halide lamps (Hyper LII) for 120 s. Knoop hardness and water solubility were determined according to standardized testing methods. Although post-cure heat treatment considerably elevated the Knoop hardness number for both materials, the greatest hardness number was generated with the use of the metal halide unit. Water solubility of the Dentacolor material was lowest when the material was cured with the metal halide unit, followed by the secondary heated group, whereas, solubility of the Artglass material was unaffected by the curing modes. This suggests that the use of a high intensity light source is more effective than the application of secondary heating for improving the post-curing properties of composites.

Analysis of Variance↗

PubMed2000

Corrosion resistance of a magnetic stainless steel ion-plated with titanium nitride.

This in vitro study evaluated the corrosion resistance of a titanium nitride (TiN) ion-plated magnetic stainless steel (447J1) for the purpose of applying a magnetic attachment system to implant-supported prostheses made of titanium. The surface hardness of the TiN ion-plated 447J1 alloy with varying TiN thickness was determined prior to the corrosion testing, and 2 micrometers thickness was confirmed to be appropriate. Ions released from the 447J1 alloy, TiN ion-plated 447J1 alloy, and titanium into a 2% lactic acid aqueous solution and 0.1 mol/L phosphate buffered saline (PBS) were determined by means of an inductively coupled plasma atomic emission spectroscopy (ICP-AES). Long-term corrosion behaviour was evaluated using a multisweep cyclic voltammetry. The ICP-AES results revealed that the 447J1 alloy released ferric ions into both media, and that the amount of released ions increased when the alloy was coupled with titanium. Although both titanium and the TiN-plated 447J1 alloy released titanium ions into lactic acid solution, ferric and chromium ions were not released from the alloy specimen for all conditions. Cyclic voltamograms indicated that the long-term corrosion resistance of the 447J1 alloy was considerably improved by ion-plating with TiN.

Coated Materials, Biocompatible↗

PubMed2000

Influence of formaline cresol on bond strength of adhesive luting agents to dentin.

The present study investigates the influence of the pulpotomy agent formaline cresol (FC) on bond strength between dentin and five adhesive systems (Super-Bond C&B, Bistite II, Imperva Dual Set, Panavia 21, and Panavia 21 with AD Gel). After the dentin surfaces of 75 bovine teeth (including 25 control samples) were exposed by grinding, 25 of the samples were soaked in FC for 2 days, and 25 samples were soaked for 7 days. Samples were bonded to acrylic rods using five adhesive systems, and tensile bond strengths were determined after 1-day immersion in water. Data were analysed by analysis of variance and Duncan's new multiple range test, and the fractured surfaces were observed through a scanning electron microscope. The bond strengths were found to be influenced by the type of system, soaking period, and their combination. The bond strength values of three adhesive systems (Super-Bond C&B, Imperva Dual Set Bistite II, and Panavia 21 with AD Gel) decreased after soaking in FC. After 7 days of FC exposure, the highest bond strength (9.8+/-2.9 MPa) was obtained with the Super-Bond C&B system.

Analysis of Variance↗

PubMed2000

Clinical evaluation of an urethane tetramethacrylate-based composite material as a prosthetic veneering agent.

The purpose of the current study was to evaluate the clinical performance of a hybrid composite material used as a prosthetic veneering agent after servicing for more than 4 years. A photo-curable composite material (Cesead) was selected as the veneering agent. Composite resin veneered restorations made with the composite and a noble metal alloy were inserted into 110 teeth of 40 patients. Modified United States Public Health Service (USPHS) criteria were used for direct evaluation of colour matching ability, veneer-metal interfacial staining, veneer surface texture, staining of the metal casting, and wear of the veneer-metal interface. After an average observation period of 5 years and 3 months, the rate of restorations considered to be clinically ideal (Alfa) was 75.5% for colour match, 93.6% for veneer-metal interfacial staining, 82.7% for veneer surface texture, 97.3% for staining of the metal casting, and 95.5% for wear. The restorations judged as clinically unacceptable (Charlie) consisted of only one case for colour match and three cases for veneer surface texture. Although the Alfa rate decreased with increasing length of service, the Cesead composite is considered to be a clinically reliable material as a prosthetic veneering agent.

Adult↗

PubMed2000

Adhesive bonding of stainless steels and their component metals.

The purpose of the current study was to evaluate the bond strength of a metal adhesive system bonded to stainless steels and their component metals. Two sizes of disk specimens (10 and 8 mm in diameter x 2.5 mm thickness) were machined from two stainless steels designed for magnetic attachment (AUM20 and SUS 316L), as well as from high-purity chromium (Cr) and nickel (Ni) metals for reference. The specimens were air-abraded with alumina, either primed with a metal conditioner (Cesead II Opaque Primer) or left unprimed, and bonded with an adhesive resin (Super-Bond Opaque). Shear bond strengths were determined before and after thermocycling, and the results were analysed by analysis of variance (ANOVA). Post-thermocycling bond strengths of the unprimed groups were 16.3 MPa for the AUM20 alloy, 7.5 MPa for the SUS 316L alloy, 31.1 MPa for Cr and 3.1 MPa for Ni. Those of the conditioned groups were 30.3 MPa for the AUM20 alloy, 32.9 MPa for the SUS 316L alloy, 39.3 MPa for Cr and 13.1 MPa for Ni. Application of the conditioner elevated the bond strengths of all groups (P<0.05). It can be concluded that combined use of the conditioner and the Super-Bond adhesive is effective for bonding the stainless steels examined, and that Cr is a suitable component for the bonding system in question.

Analysis of Variance↗

PubMed2000

Wear and surface roughness of current prosthetic composites after toothbrush/dentifrice abrasion.

STATEMENT OF PROBLEM: Surface changes of prosthetic composites caused by toothbrushing are known, although composite materials have been improved and are now widely used for various kinds of prosthetic restorations. PURPOSE: This study evaluated the influence of toothbrushing on abrasive wear and surface roughness of current prosthetic composites. MATERIAL AND METHODS: Seven composite materials (Artglass, Axis, Cesead II, Conquest Sculpture, Estenia, Infis, and Targis) were assessed, and a machinable ceramic material (Cerec 2 Vitablocs) was used as a reference. Composite specimens polymerized with their proprietary curing units and sectioned ceramic specimens were stored in water for 14 days, and subsequently subjected to toothbrush-dentifrice abrasion. The amount of vertical loss and the surface roughness of each specimen after 20,000 strokes were determined with a profilometer. Average values of groups of 5 specimens were compared with ANOVA and Duncan new multiple range test. RESULT: Significantly (P < .05) less wear was observed with respect to the Targis (10.01 microm; SD = 0.53 microm) and Estenia (13.04 microm; 1.95 microm) materials than for the other composites assessed, whereas Artglass (34.08 microm; 3.66 microm) and Conquest Sculpture (31.78 microm; 4.67 microm) materials demonstrated the most wear. The least surface roughness was exhibited by Conquest Sculpture (Ra, 0.54 microm; 0.07 microm) material, and the greatest by Cesead II (1.10 microm; 0.13 microm). Ceramic material showed a more wear-resistant (4.54 microm; 0.79 microm) and smoother (0.26 microm; 0.02 microm) surface than any of the composite materials. CONCLUSION: Abrasion and surface roughness of the prosthetic composites caused by toothbrushing varied in accordance with the material. Type of prosthetic composite significantly influenced the surface condition after toothbrushing.

Analysis of Variance↗

PubMed2000

Relative contribution of NK and NKT cells to the anti-metastatic activities of IL-12.

Conventional T cells, NK cells and NKT cells have been implicated in the anti-tumor activities induced by IL-12. Here we show that IL-12-induced immune responses are partially impaired in T and NKT cell-deficient RAG-2(-/-) mice, and in NKT cell-deficient CD1(-/-) mice. In response to a small dose (<1000 U) of IL-12, RAG-2(-/-) and CD1(-/-) mice demonstrated reduced cytotoxicity, serum IFN-gamma elevation and anti-metastatic activities; in contrast, in response to a high dose (>2000 U) of IL-12, the IL-12-induced immune responses of RAG-2(-/-) and CD1(-/-) mice were indistinguishable from wild-type mice. The defective responses to low-dose IL-12 of RAG-2(-/-) mice were corrected by adoptive transfer of NKT cells but not NK cells. These findings indicate that both NK and NKT cells contribute to the anti-metastatic responses induced by IL-12, and that NKT cells are mostly responsible for the low-dose activities of this cytokine.

Adoptive Transfer↗

PubMed2000

Bond strength of prosthodontic luting materials to titanium after localized cyclic loading.

PURPOSE: To establish an in vitro analysis system to evaluate the effect of cyclic loading on the bond strengths and durability of luting materials bonded to titanium. MATERIALS AND METHODS: Machine-milled titanium disks were finished with 600 grit silicon-carbide paper and pairs of disks were bonded together using the five different luting materials. A stainless steel stylus was vertically loaded at a center position (Model 1) or at the border (Model 2) of the specimens with a force of 75.6 N at 7500 cycles/hr. When the stylus contacted the specimen surface through the water slurry of poly(methyl methacrylate) beads, it rotated clockwise up to 15 degrees and counter-rotated. Shear bond strengths were determined 1 hr after bonding, after storage in water at room temperature for 24 hr, and after the loading for 100,000 cycles. RESULTS: The bond strengths of the unfilled adhesive resin and resin-based composite cement (RBC) were significantly higher than those of the glass-ionomer cements. Zinc phosphate cement demonstrated no bonding ability to titanium. After 100,000 cycles, peripheral loading in Model 2 significantly reduced the bond strength of the RBC and glass-ionomer cements, while Model 1 loading did not. The highest and the most durable bonds were obtained with the unfilled adhesive resin in both models.

Adhesiveness↗

PubMed2000

Influence of acidulated phosphate fluoride agents on surface characteristics of composite restorative materials.

PURPOSE: To evaluate the surface changes of resin-based composites (RBC) when they were exposed to acidulated phosphate fluoride (APF) agents. MATERIALS AND METHODS: One microfilled (Silux Plus) and four hybrid (Clearfil AP-X, Lite-Fil IIA, Palfique Estelite, Progress) RBCs were separately treated with two APF agents (Fluorident Gel, Floden A). Changes in surface roughness were determined with a surface analyzer, and relief patterns were observed using a scanning electron microscope. RESULTS: Although the surfaces of hybrid RBC materials containing macro-inorganic filler particles were generally found to be rougher than that of the microfilled composite regardless of APF treatment, macro-inorganic fillers in two of the hybrid composites demonstrated noticeable etched patterns generated by an APF solution.

Acidulated Phosphate Fluoride↗