Biomedical subjects

Ikuya Watanabe

Publications and source records attributed to Ikuya Watanabe.

16 recordsLinked to original sources

PubMed2006

Joint properties of cast Fe-Pt magnetic alloy laser welded to gold alloys.

This study investigated the joint properties of a cast Fe-Pt magnetic alloy (Fe-36 at % Pt) laser welded to three gold alloys. The gold alloys used were ADA Type II and Type IV gold alloys, and an Ag-based (Ag-Au) gold alloy. Cast plates (0.5 x 3.0 x 10 mm) were prepared for each alloy. After the cast Fe-Pt plates were heat treated, they were butted against each of the three alloys and then laser welded with Nd:YAG laser at 200 V. Homogeneously welded specimens were also prepared for each alloy. Tensile testing was conducted at a crosshead speed of 1 mm/min. Failure load (N) and elongation (%) were recorded. After tensile testing, the fractured surfaces were examined with the use of SEM. The failure-load values of the group of alloys welded homogeneously were ranked in the order of: Ag-Au alloy > Type IV alloy > Type II alloy > Fe-Pt alloy. The Type IV alloy welded to Fe-Pt alloy had the highest failure-load value among the three alloys tested. The elongation results tended to follow a similar pattern. The results of this study indicated that Type IV gold alloy is a suitable alloy for metal frameworks to which cast Fe-Pt magnetic alloy is laser welded.

Alloys↗

PubMed2006

The effects of various additives on setting properties of MTA.

Delayed setting times may limit the use of mineral trioxide aggregate (MTA) in endodontic procedures. The purpose of this study was to identify types and amounts of MTA additives to enhance its setting properties. Additives tested include saline, 2% lidocaine, 3.0% NaOCl gel, chlorhexidine gluconate gel, K-Y Jelly, 3% and 5% CaCl2. The setting times were evaluated using a Vicat apparatus; compressive strengths of set materials were evaluated with an Instron machine. NaOCl gel, K-Y Jelly and 5% CaCl2 decreased the setting time to 20 to 25 min; compressive strengths of these set materials were significantly lower than MTA mixed with water (p < 0.05). Because MTA mixed with NaOCl gel demonstrated good working properties and improved setting time, this combination may be a viable option in single visit procedures where compressive strength of the material is not a critical issue.

Aluminum Compounds↗

PubMed2005

Effect of surface reaction layer on grindability of cast titanium alloys.

OBJECTIVE: The purpose of this study was to investigate the effect of the cast surface reaction layer on the grindability of titanium alloys, including free-machining titanium alloy (DT2F), and to compare the results with the grindability of two dental casting alloys (gold and Co-Cr). METHODS: All titanium specimens (pure Ti, Ti-6Al-4V and DT2F) were cast using a centrifugal casting machine in magnesia-based investment molds. Two specimen sizes were used to cast the titanium metals so that the larger castings would be the same size as the smaller gold and Co-Cr alloy specimens after removal of the surface reaction layer (alpha-case). Grindability was measured as volume loss ground from a specimen for 1 min using a handpiece engine with a SiC abrasive wheel at 0.1 kgf and four circumferential wheel speeds. RESULTS: For the titanium and gold alloys, grindability increased as the rotational speed increased. There was no statistical difference (p>0.05) in grindability for all titanium specimens either with or without the alpha-case. Of the titanium metals tested, Ti-6 Al-4V had the greatest grindability at higher speeds, followed by DT2F and CP Ti. The grindability of the gold alloy was similar to that of Ti-6 Al-4V, whereas the Co-Cr alloy had the lowest grindability. SIGNIFICANCE: The results of this study indicated that the alpha-case did not significantly affect the grindability of the titanium alloys. The free-machining titanium alloy had improved grindability compared to CP Ti.

Alloys↗

PubMed2005

Shear bond strength of resin composite to magnetic Fe-Pt alloy.

STATEMENT OF PROBLEM: It is important to obtain strong adhesion between resin composite material and magnetic Fe-Pt alloy for fabrication of an indirect veneered crown. However, little is known about the bond strength between these materials. PURPOSE: This study evaluated the bond strength of resin composite to magnetic Fe-Pt alloy, using 4 adhesive metal primers. MATERIAL AND METHODS: Seventy disk-shaped patterns (7.5 mm in diameter, 2.0 mm thick) were cast from a custom-made Fe-Pt ingot using a high-frequency centrifugal casting machine. After the bonding surfaces were airborne-particle abraded with 50 microm Al2O3, specimens were divided into groups (n=7) and primed with either Metal Primer II (MP), Meta Fast Bonding Liner (BL), New Meta Color INFIS Opaque Primer (IN), or Epricord Opaque Primer (EP). Nonprimed specimens served as controls (n=7). A resin composite (New Meta Color INFIS) was then applied to all specimens and polymerized. After the specimens were immersed in 37 degrees C water for 24 hours or thermal cycled at 4 degrees C to 60 degrees C with a 1-minute dwell time of up to 10,000 cycles, the shear bond strengths (MPa) were measured using a universal testing machine at a crosshead speed of 0.5 mm/min. The data were statistically analyzed by a 2-way analysis of variance and the Scheffe test (alpha=.05). RESULTS: Although IN had the lowest strength, there were no significant differences in bond strengths of the other 3 primers (MP, BL, and EP) before thermal cycling. The bond strengths of MP and EP were slightly altered by thermal cycling (P >.05); however, BL and IN underwent a significant decrease (P <.05). CONCLUSION: The results of this in vitro study indicate that MP and EP provide superior long-term shear strength when bonding the resin composite evaluated to Fe-Pt alloy.

Composite Resins↗

PubMed2005

Effect of heat treatment on joint properties of laser-welded Ag-Au-Cu-Pd and Co-Cr alloys.

PURPOSE: This study investigated the effect of heat treatment on the strengths of laser-welded cast Ag-Au-Cu-Pd and Co-Cr alloys. MATERIALS AND METHODS: Cast plates of Ag-Au-Cu-Pd (Ag) and Co-Cr (Co) alloys were prepared. After polishing the surfaces to be welded, the plates were matched and butted Ag to Ag (Ag/Ag), Co to Co (Co/Co), and Ag to Co (Ag/Co) and welded using Nd:YAG laser at a pulse duration of 10 ms, spot diameter of 1 mm, and voltage of 200 V. Five specimens were prepared for each experimental condition by bilaterally welding them with five spots. The Ag/Ag, Ag/Co, and control Ag underwent two heat treatments-softening (ST) and hardening (AH). A group of as-cast specimens serving as controls was not given either heat treatment. The failure load and percent elongation were measured at a crosshead speed of 1.0 mm/min. RESULTS: The fracture resistance of Co/Co was similar to that of the control Co, while the fracture resistance of Co/Ag was significantly lower than that of both like alloy pairings for all heat-treating conditions. The control Ag had greater fracture resistance after AH and lower fracture resistance after ST. The AH treatment increased the fracture resistance, and the ST treatment decreased the fracture resistance of both Ag/Ag and Co/Ag, although not significantly. The percentage of elongation appeared to positively correlate with the fracture resistance results. CONCLUSIONS: The results obtained in this study indicated that the age-hardening heat treatment increased the weld strength between the paired Au-Ag-Cu-Pd alloys and between the Au-Ag-Cu-Pd and Co-Cr alloys.

Chromium Alloys↗

PubMed2005

Joint properties of cast Fe-Pt magnetic alloy laser-welded to Co-Cr alloy.

This study investigated the joint properties of Fe-Pt alloy laser-welded to Co-Cr alloy. Cast plates (0.5 x 3.0 x 10 mm) were prepared with Fe-Pt and Co-Cr alloys. Fe-Pt plates were butted against Co-Cr plates and laser-welded using Nd:YAG laser. Control and homogeneously welded specimens were also prepared. Laser welding was performed with and without argon shielding. Tensile testing was conducted, and both fracture force (Ff: N) and elongation (El: %) were recorded. There were no differences in the Ff value between the specimens with and without argon shielding for the welded Fe-Pt/Co-Cr. Lower Ff value of the welded specimen was obtained in the order of Fe-Pt alloy < Fe-Pt/Co-Cr < Co-Cr alloy. The results indicated that Fe-Pt welded to Co-Cr had Ff values between the values of homogeneously welded Fe-Pt and Co-Cr alloys. Argon shielding, on the other hand, had no effect on the weld strength between Fe-Pt and Co-Cr alloys.

Argon↗

PubMed2004

Tensile strength and elongation of laser-welded Ti and Ti-6AL-7NB.

This study established data demonstrating the possible laser-welded strengths of cast Ti and Ti-6Al-7Nb and compared them to those of two dental-casting alloys. Cast plates of Ti, Ti-6Al-7Nb, gold, and Co-Cr alloy were prepared. After polishing the surfaces to be welded, two plates were abutted and welded using an Nd:YAG laser at a pulse duration of 10 ms, spot diameter of 1 mm, and voltage of 200 V. Five specimens were prepared for each metal by welding either three or five spots unilaterally or bilaterally. The fracture load and percent elongation were measured at a crosshead speed of 1.0 mm/min. The bilaterally welded specimens performed significantly greater than unilaterally welded specimens in both fracture load and elongation whether they were welded with three or five spots per side. The bilaterally welded Ti and Ti-6Al-7Nb specimens were nearly as strong as their corresponding control specimens, whereas the gold and Co-Cr specimens were approximately half as strong. When a large proportion of the cross-sectional area of the joint is laser welded, the strength of the laser-welded portion of the cast Ti and Ti-6Al-7Nb may approach or equal that of the nonwelded metal frameworks.

Alloys↗

PubMed2004

Optimizing mechanical properties of laser-welded gold alloy through heat treatment.

OBJECTIVE: The goal of this work was to improve the mechanical strength of laser-welded gold alloy with age-hardenability at intraoral temperature. METHODS: The gold alloy was cast conventionally in plate patterns (0.5 mm x 3.0 mm x 20 mm). After bench-cooling the mold to room temperature (as-cast state), transverse sections of the plate were made at mid-span. They were butted against one another and welded using Nd:YAG laser (current: 320 A; time: 10 ms; spot diameter: 1 mm). Three laser pulses were applied from both sides to cover the joint width (3.0 mm) of the specimens before or after solution heat treatment at 700 degrees C/5 min. Uncut control specimens (non-welded) were also prepared. After solution treatment, two different heat treatments were given the laser-welded specimens: high-temperature aging at 250 degrees C/15 min, or intraoral aging at 37 degrees C/3 days. Control specimens underwent all of the heat treatments after solution treatment. Tensile testing was conducted at a crosshead speed of 2 mm/min and a gauge length of 10 mm. RESULTS: Solution treatment of the gold alloy before laser-welding did not improve the mechanical strength of laser-welded gold alloy after high-temperature aging or intraoral aging. The joint strengths of laser-welded gold alloy were improved only by solution heat treatments after laser-welding and subsequent aging treatment at high or intraoral temperatures. SIGNIFICANCE: The results of this study indicated that laser-welded cast gold alloy prostheses aged at high or intraoral temperatures produce high strength when they are solution-treated after laser-welding.

Dental Soldering↗

PubMed2004

Tensile properties and hardness of cast Fe-Pt magnetic alloys.

STATEMENT OF PROBLEM: There is little information about the mechanical properties of castable magnetic attachments made of iron-platinum (Fe-Pt) alloys after heat treatment. MATERIAL AND METHODS: Dumbbell-shaped tensile specimens were cast with 5 alloys: 2 types of Fe-Pt alloys for magnets and keepers, pure Ti, Ti-6Al-7Nb, and Co-Cr alloy. The tensile specimens of the Fe-Pt magnets and keepers underwent different heat treatments to obtain the appropriate properties for a magnet and a keeper. Vickers hardness was measured prior to testing. Tensile testing was conducted in a universal testing machine at a crosshead speed of 2 mm/min until failure. Ultimate tensile strength, yield strength, elongation, and modulus of elasticity were recorded. The data were analyzed using 1-way analysis of variance and the Tukey test (alpha=.05), fractured surfaces were examined using a scanning electron microscope (SEM). RESULTS: The highest tensile and yield strengths were found for Ti-6Al-7Nb, followed by Co-Cr, CP Ti, and the Fe-Pt keeper. There was no significant difference in ultimate tensile strength between the CP Ti and the Fe-Pt keeper. The lowest elongation was found for the Fe-Pt magnet (2.8%), whereas the Fe-Pt keeper had the highest elongation (14.0%). The Fe-Pt magnet and keeper had similar modulus of elasticity values. The hardness of the cast Fe-Pt magnets was the highest among the metals tested. SEM micrographs of the Fe-Pt keepers showed a microstructure with ductile dimple fractures, whereas the Fe-Pt magnets were characterized by brittle fractures at the grain boundaries. CONCLUSIONS: The mechanical properties of the cast Fe-Pt keepers were similar to those of the cast pure Ti. The Fe-Pt magnets were extremely hard and brittle.

Analysis of Variance↗

PubMed2003

Application of cast iron-platinum keeper to a collapsible denture for a patient with constricted oral opening: a clinical report.

Insertion of a denture is especially difficult for patents with a constricted oral opening. This report describes the fabrication of a collapsible removable partial denture with a cast iron-platinum attachment for a partially edentulous woman with a constricted oral opening resulting from rheumatoid arthritis and a craniotomy for a subarachnoid hemorrhage.

Aged↗

PubMed2003

Electrochemical characterization of cast titanium alloys.

A reaction layer forms on cast titanium alloy surfaces due to the reaction of the molten metal with the investment. This surface layer may affect the corrosion of the alloy in the oral environment. The objective of this study was to characterize the in vitro corrosion behavior of cast titanium alloys. ASTM Grade 2 CP titanium, Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr alloys were cast into a MgO-based investment. Experiments were performed on castings (N=4) with three surface conditions: (A) as-cast surface after sandblasting, (B) polished surface after removal of the reaction layer, and (C) sandblasted surface after removal of the reaction layer. Open-circuit potential (OCP) measurement, linear polarization, and potentiodynamic cathodic polarization were performed in aerated (air+10% CO(2)) modified Tani-Zucchi synthetic saliva at 37 degrees C. Potentiodynamic anodic polarization was subsequently conducted in the same medium deaerated with N(2)+10% CO(2) gas 2 h before and during the experiment. Polarization resistance (R(P)) and corrosion rate (I(CORR)) were calculated. Numerical results were subjected to nonparametric statistical analysis at alpha=0.05. The OCP stabilized for all the specimens after 6 x 10(4)s. Apparent differences in anodic polarization were observed among the different surfaces for all the metals. A passivation region followed by breakdown and repassivation were seen on specimens with surfaces A and C. An extensive passive region was observed on all the metals with surface B. The Kruskal-Wallis test showed no significant differences in OCP, R(p), I(CORR) or break down potential for each of the three surfaces among all the metals. The Mann-Whitney test showed significantly lower R(P) and higher I(CORR) values for surface C compared to the other surfaces. Results indicate that the surface condition has more effect on corrosion of these alloys than the surface reaction layer. Within the oxidation potential range of the oral cavity, all the metal/surface combinations examined showed excellent corrosion resistance.

Alloys↗

PubMed2003

Surface changes induced by fluoride prophylactic agents on titanium-based orthodontic wires.

This study investigated the effect of fluoride prophylactic agents on the surfaces of titanium-based orthodontic wires. Four types of titanium-based orthodontic wires (2 nickel-titanium alloy wires [nickel-titanium and copper-nickel-titanium] and 2 beta-titanium alloy wires [titanium-molybdenum and titanium-niobium], all from Ormco, Glendora, Calif) with similar sizes were prepared and immersed in 5 fluoride prophylactic agents (2 acidulated phosphate fluoride agents [Nupro APF (Dentsply International, York, Pa) and Florentine III (Confi-Dental, Louisville, Colo)], 1 neutral agent [Neupro Neutral (Dentsply International)] and 2 stannous fluoride agents [Florentine II (Confi-Dental) and Perio-Med (Omni International, Warrenton, Va)]) for 5 minutes, 1 hour, and 24 hours. After immersion, average surface roughness and color changes were evaluated. The surface changes were observed with a scanning electron microscope. The average surface roughness data were statistically analyzed by analysis of variance and Tukey post hoc test at a significance level of alpha = 0.05. There were no significant differences in average surface roughness value among fluoride solutions or orthodontic wires, except for the titanium-molybdenum wire, which showed significantly (P <.05) higher average surface roughness values after immersion in Nupro APF for 24 hours. The results suggested that a few applications of acidulated phosphate fluoride agents might change the surface color of the beta-titanium alloy wires, particularly the titanium-molybdenum wire, which contains a large amount (about 80%) of titanium.

Acidulated Phosphate Fluoride↗

PubMed2003

Effect of welding method on joint strength of laser-welded gold alloy.

PURPOSE: To examine the effect of welding method and heat treatment on the strength of laser-welded gold alloy with age-hardenability at intraoral temperature. METHODS: Cast gold alloy plates (0.5 x 3.0 x 20 mm3) were prepared and cut perpendicular to the 3.0 mm surface of the plate. After the cut halves were fixed in a jig, they were laser-welded using a Nd: YAG laser. Three laser pulses were applied from one side (single-welded) or both sides (double-welded) to weld the entire joint width of the specimens. Three different heat treatments were given the specimens: solution treatment at 700 degrees C for 5 minute (ST), aging at 250 degrees C for 15 minute after ST (HA), and aging at 37 degrees C for 3 day after ST (IA). As-cast specimens were also reserved. Uncut specimens served as non-welded control specimens. Tensile testing was conducted at a crosshead speed of 2 mm/minute and a gauge length of 10 mm. The breaking stress (Bs: MPa) was recorded, and the data (n = 5 per group) were statistically analyzed. RESULTS: In the control groups, the Bs values of the IA were not significantly different (P > 0.05) from those of the HA specimens. The laser-welded IA specimens showed significantly greater (P < 0.05) Bs values compared to the solution-treated and as-cast specimens. The double-welded specimens showed significantly greater Bs values compared to the single-welded specimens after any heat treatment.

Dental Soldering↗

PubMed2003

Shear bond strengths of laboratory-cured prosthetic composite to primed metal surfaces.

PURPOSE: To examine the effect of using metal primers to enhance the shear bond strength of a laboratory-cured prosthetic composite to cast metal surfaces. METHODS: Cast discs (10 mm diam., 2.5 mm thick) were prepared from high gold-containing alloy, Ag-Au-Pd alloy, and commercially pure titanium (CP Ti). After casting, the surfaces of the discs were sandblasted with 50 microm Al2O3. Each surface to be bonded was treated with one of four types of metal primers: V-Primer (VP), Metal Primer II (MP), Cesead II Opaque Primer (OP), and an experimental primer (EP). Specimens without primer were prepared as controls. After tape with a circular hole (5 mm diam.) was fixed on the disc surface to define the bonding area, the opaque resin was applied within the hole and light-cured according to the manufacturer's instructions. After polymerization of the opaque resin, a layer (1 mm thick) of each dentin and enamel resin was applied separately using Teflon matrices (6 mm I. D.). The bonded specimens were immersed in 37 degrees C water for 24 hours (baseline) and were then thermocycled for 5,000 and 10,000 cycles. The shear bond strengths were determined at the baseline and after thermocycling. The results were analyzed using ANOVA/Bonferroni/Dunn's test (c = 0.05). RESULTS: There were no statistical differences (P > 0.05) in the shear bond strength among surface applications for the gold alloy at the baseline. After 5,000 and 10,000 thermocycles, the gold alloy specimens primed with OP and EP primers exhibited higher bond strength compared to those primed with VP and MP primers, and the non-primed control specimens. The Ag-Au-Pd alloy specimens tended to be similar to the gold alloy specimens after each number of thermocycles. The shear bond strengths to CP Ti primed with OP and EP were significantly (P < 0.05) higher than the others after 5,000 and 10,000 thermocycles.

Analysis of Variance↗

PubMed2002

Application of cast magnetic attachments to sectional complete dentures for a patient with microstomia: a clinical report.

Patients with microstomia who must wear removable dental prostheses often state that they are unable to insert or remove the prosthesis because of the constricted opening of the oral cavity. This article presents a cast iron-platinum magnetic attachment system applied to sectional collapsed complete dentures for an edentulous patient with microstomia. With the use of lingual and palatal midline hinges and a cast iron-platinum magnetic attachment, the sectional prosthesis was successfully and easily inserted and provided adequate function in the patient's mouth.

Aged↗

PubMedDate not supplied

Laser welding of cast titanium and dental alloys using argon shielding.

PURPOSE: This study investigated the effect of argon gas shielding on the strengths of laser-welded cast Ti and Ti-6Al-7Nb and compared the results to those of two dental casting alloys. MATERIALS AND METHODS: Cast plates of Ti, Ti-6Al-7Nb, gold, and Co-Cr alloy were prepared. After polishing the surfaces to be welded, two plates were abutted and welded using Nd:YAG laser at a pulse duration of 10 ms, spot diameter of 1 mm, and voltage of 200 V. Five specimens were prepared for each metal by bilaterally welding them with three or five spots either with or without argon shielding. The failure load and percent elongation were measured at a crosshead speed of 1.0 mm/min. RESULTS: The factor of argon shielding significantly affected the failure load and elongation of the laser-welded specimens. The failure loads of argon-shielded laser-welded CP Ti and Ti-6Al-7Nb were greater compared with the failure loads of specimens welded without argon shielding for both three- and five-spot welding. Regardless of argon shielding, the failure loads of the laser-welded gold alloy were approximately half that of the control specimens. In contrast, the failure loads of the nonshielded laser-welded Co-Cr alloy were greater. The percent elongations positively correlated with the failure loads. CONCLUSIONS: The use of argon shielding is necessary for effective laser-welding of CP Ti and Ti-6Al-7Nb but not for gold and Co-Cr alloy.

Analysis of Variance↗