Yamamoto Precious Metal Co.

Konan, Japan

Yamamoto Precious Metal Co.

Konan, Japan

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Tanaka H.,Yamamoto Precious Metal Co. | Tanaka H.,Kochi University of Technology | Maeda T.,Kochi University of Technology | Yamazoe M.,Yamamoto Precious Metal Co. | And 2 more authors.
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2017

Leucite (KAlSi2O6) glass-ceramic dental prostheses are fabricated by firing glass-ceramic powder into the shape of a tooth crown on an abutment-tooth frame made from a precious metal alloy. It is known that, if this alloy contains silver, the prosthesis suffers from an unattractive yellow discoloration. Although the addition of antimony trioxide to the glass-ceramic mixture has been shown to reduce such yellowing, this compound is believed to be toxic to humans. In this study, we investigate yellowing with the addition of cerium oxide, which is a promising replacement for antimony trioxide due to its low toxicity to biological organisms. Using scanning electron microscopy, energy dispersive X-ray spectrometry, and ultraviolet and visible spectrophotometry, we analyze the fine-grained structure and composition of the fired glass-ceramic body that comes into contact with silver, as well as the nature and extent of the resulting yellowing. Our findings indicate that, as previously thought, the yellowing is indeed caused by the diffusion of silver ions into the fired glass-ceramic body to form colloids, but they also reveal a contribution from sodium at the interface between the fired body and the silver. To investigate methods suppressing the yellowing, we fabricate several model glasses with different sodium-to-cerium ratios, and study the nature and extent of the yellowing for each glass. Our results reveal that the extent of yellowing is correlated with increased sodium content and that the yellowing may be suppressed by adjusting the sodium-to-cerium ratio. © 2017 The Ceramic Society of Japan. All rights reserved.


Nagasawa S.,Matsumoto Dental University | Yoshida T.,Matsumoto Dental University | Tamura K.,Matsumoto Dental University | Yamazoe M.,Matsumoto Dental University | And 6 more authors.
Dental Materials Journal | Year: 2010

To construct a human teeth database which is freely available to researchers and students, three-dimensional human tooth models were generated in a previous study, by means of micro-CT, from 35 human teeth extracted during orthodontic treatment. In this study, X-ray images of 55 extracted human teeth were acquired using three-dimensional micro-CT at a resolution of 50×50×50 μm, and then visualized using a numerical data visualization software. These carious tooth models provided insight into the morphology and progression of carious defects as well as a rare insight into the morphology of carious tooth pulp, therefore rendering them as a useful tool and efficient method for dental students' learning. Moreover, these three-dimensional models could be simultaneously observed and used by many students and researchers at any one time, which was a superior advantage than having only one actual tooth for learning and study by many.


Patent
Yamamoto Precious Metal Co., Shinko Metal Products Co. and NHK Spring Co. | Date: 2015-06-10

Provided are an alloy material having excellent conductivity, and further having high hardness and excellent workability for use in a contact probe; and a contact probe and a connection terminal each of which consists of the alloy material. A composition range of a ternary alloy of silver (Ag), palladium (Pd), and copper (Cu) contains 17 at% to 25 at% of Ag, 30 at% to 45 at% of Pd, and 30 at% to 53 at% of Cu. At least one of manganese (Mn), tin (Sn), silicon (Si), antimony (Sb), titanium (Ti) and magnesium (Mg) is added to the composition in a range of 4.5 at% or less, in which the Mn in a range of 0.5 at% to 3.5 at%, the Sn in a range of 1 at% to 2 at%, the Si in a range of 0.5 at% to 2 at%, the Sb in a range of 0.5 at% to 3 at%, the Ti in a range of 0.5 at% to 2 at%, and the Mg in a range of 0.5 at% to 3.5 at% are added to the composition.


Patent
Yamamoto Precious Metal Co., Nhk Spring Co. and Shinko Metal Products Co. | Date: 2013-08-02

An alloy material includes: a composition containing 17 at % to 25 at % of silver (Ag), 30 at % to 45 at % of palladium (Pd), and 30 at % to 53 at % of copper (Cu) in a composition range of a ternary alloy of Ag, Pd, and Cu; and at least one of manganese (Mn), tin (Sn), silicon (Si), antimony (Sb), titanium (Ti) and magnesium (Mg) added to the composition in a range of 4.5 at % or less, and the Mn in a range of 0.5 at % to 3.5 at %, the Sn in a range of 1 at % to 2 at %, the Si in a range of 0.5 at % to 2 at %, the Sb in a range of 0.5 at % to 3 at %, the Ti in a range of 0.5 at % to 2 at %, and the Mg in a range of 0.5 at % to 3.5 at % are added to the composition.


Kato T.,Yamamoto Precious Metal Co. | Kato T.,Kochi University of Technology | Kimura H.,Yamamoto Precious Metal Co. | Saigo K.,Kochi University of Technology | And 3 more authors.
Journal of Applied Polymer Science | Year: 2013

Adhesion of a cured dental opaquer, which masks metallic appearance and color, to sandblasted Ti aided by 3-methacryloyloxypropyltrimethoxysilane (MPTS) is investigated. The tensile bond strengths of Ti and the opaquer are 43.3 and 45.9 MPa, respectively, when MPTS dissolved in ethanol (6 wt %) and premixed with the opaquer (3 wt %) are applied to the sandblasted Ti surface. Mirror finishing alone and sandblasting alone result in the bond strengths of 1.8 and 21.3 MPa, respectively. After thermal cycling (4 and 60°C for 5000 cycles), the bond strengths of the Ti with sandblasting and the MPTS treatment remain higher than that of the Ti with sandblasting only. Sandblasting and the MPTS treatment effectively promote the adhesion of the opaquer to Ti that rapidly forms an oxide surface layer. The silane-aided adhesion of the opaquer to the sandblasted Ni-Cr, Co-Cr, and Au-Ag-Pd alloys attain adhesive strengths of 33.2, 31.9, and 31.6 MPa, respectively. Copyright © 2012 Wiley Periodicals, Inc.


Kato T.,Yamamoto Precious Metal Co. | Kato T.,Kochi University of Technology | Saigo K.,Kochi University of Technology | Tsuneishi M.,Yamamoto Precious Metal Co. | And 2 more authors.
Kobunshi Ronbunshu | Year: 2012

A newly developed inorganic coagulated filler consisting of SiO 2, ZrO 2, and Al 2O 3 was mixed with a matrix composite containing 1,6-bis-(methacryloyloxy-2-ethoxycarbonylamino)-2,4, 4-trimethylhexane (UDMA) and colloidal silica as main ingredients in order to attain the highly esthetic and tough dental resin. Differences in the refractive index between the filler and the matrix before and after curing by a camphorquinone/amine/visible light initiation system were minimized to achieve the high translucency required for the esthetic resin. The refractive index of the filler was adjusted by coagulation of the primary particle at an optimum temperature (1100°C). Flexural strength of the resin was increased by the anchor effect, depending on the surface conditions of the filler. Furthermore, the flexural strength of the resin was found to increase to 250 MPa by post-curing upon heating at 110°C. As a result, the sufficiently translucent and tough resin in comparison to commercial products (flexural strength ≤220 MPa) was successfully obtained. © 2012. The society of polymer science, Japan.


Tanaka Y.,Hokkaido University | Tanaka Y.,Yamamoto Precious Metal Co. | Ishikawa M.,Hokkaido University | Ishikawa M.,Kyoto University | And 6 more authors.
Crystals | Year: 2012

Electrolysis of Na and K salts of the anion dicyano(phthalocyaninato)cobalt(III) (Co(Pc)(CN)2) in ethanol yields one-dimensional partially oxidized salts of A[Co(Pc)(CN)2]2·4(EtOH) (A = Na and K). The cationic component is the supramolecular cation [A(EtOH)4]+, which forms hydrogen bonds with the CN ligands of the Co(Pc)(CN)2 units. The crystal shows metallic conductivity, in contrast to the thermally activated conductivity observed in the isomorphous tetraphenylphosphonium (TPP) salt of TPP[Co(Pc)(CN)2]2. Since the π-π interactions in these isomorphous crystals are nearly the same, the distinctive behavior of the Na and K salts may be attributed to the difference in the degree of charge disproportionation in these crystals. © 2011 by the authors; licensee MDPI, Basel, Switzerland.


Tomoshige R.,Sojo University | Tanaka H.,Yamamoto Precious Metal Co.
Archives of Metallurgy and Materials | Year: 2014

Hot shock compaction method was utilized for the consolidation of MAX phase composites consisting of Ti, Al and C. This paper presents the production of dense, crack-free composites by combining the combustion synthesis with explosive detonation. Another objective is to investigate various properties of the obtained shock-compacts. The shock compacted materials were post-annealed at 1173 K for releasing the shock-induced strain. As a result, these compacts had strong interparticle bonding strength and few macro cracks. Intermetallic compounds (TiAl, Ti2Al and Ti3Al) and non-oxide ceramics (TiC and Ti4Al2C2) were detected in as-synthesized and annealed materials by X-ray diffraction experiments. Also, lamella structures of Ti4Al2C2 phase were observed by SEM. It was known that the coefficient of thermal expansion increased with increasing temperature, and decreased with increasing TiC content. © 2014, Committee of Metallurgy. All rights reserved.

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