Masatoshi Takahashi

• PhD
• Tohoku University

The aim of this study was to investigate the bactericidal effect and recovery of biocompatibility of contaminated titanium surfaces using a combination treatment involving silver, copper, or iron ion application along with 400 nm purple-LED light irradiation. Additionally, the study sought to develop a functional calcium phosphate (CaP) coating tre...

In orthodontic treatment, to achieve efficient tooth movement, it is important to reduce the frictional force between the wire and the bracket, especially the binding friction that occurs when the angle between the wire and the bracket is large. Electroless nickel–polytetrafluoroethylene (Ni-PTFE) coating is a coating technology used to deposit PTF...

The hydrophilic compound 2-hydroxyethyl methacrylate (HEMA) is a major component of dental bonding materials, and it enhances the binding of resin-composites to biomolecules. However, HEMA is a well-known contact sensitizer. We reported previously that intradermal injection of HEMA induces the production of IL-1 locally in the skin. Keratinocytes a...

Titanium-20 mass% Silver (Ti-20%Ag) alloy can suppress biofilm formation on the surface. Unlike bactericidal agents, it does not kill bacteria; therefore, the healthy oral microflora remains undisturbed. To utilize the unique functions of this alloy and enable its use in the fabrication of dental prostheses that require relatively high strength, we...

The Journal of the Japanese Society of Magnetic Applications in Dentistry

Titanium has excellent biocompatibility and good corrosion resistance and is extensively used in dental implants and denture bases. However, pure titanium lacks the strength for use in dental prostheses that require relatively high strength. We developed 15 different types of Ti-Nb-Cu alloys and investigated their alloy phases and mechanical proper...

Two oval sandwich type magnetic attachments set up in various angulations and spacing, then the pattern of retentive force against horizontal displacement studied. A measuring device and methodology that matches ISO 13017 was used. A pair of magnetic attachments fixed on the same plane at a specific distance on the measuring device and set in vario...

Purpose: Moisture exclusion while treating dental caries can be challenging, and the glass ionomer cements (GICs) used for these procedures are susceptible to water. Few studies have examined the effects of the powder/liquid ratio (PLR) on the physical properties of GICs exposed to water. In this study, the hardness and thickness of the water-susc...

We developed high-strength Ti−Nb−Cu alloys and investigated their grindability. The grindability of each alloy was evaluated based on the volume of metal removed per minute (grinding rate) and on the ratio of the metal volume removed to the volume of the wheel material lost (grinding ratio). The grinding rate of the Ti-6%Nb-4%Cu, Ti-18%Nb-2%Cu, and...

The aim of this study was to assess the utility of an actuator-driven pulsed water jet (ADPJ) as a hardness-dependent carious dentin removal device by using different outputs. Thirty-six plane surface dental caries samples were treated with the ADPJ at 150, 200, and 250 voltage (12 teeth each). The Knoop hardness number (KHN) and Ca/P mass ratio we...

Binary Ti-Fe alloys of varying concentrations of Fe between 5–25% were made, and their castings evaluated in terms of microstructures formed and mechanical properties. The aim of this study was to explore the composition of Ti-Fe alloys that offers improved wear resistance of titanium. X-ray diffraction and microstructural observation revealed that...

Binary Ti-Fe alloys with 5–25 mass% Fe were prepared, and subjected to reciprocating wear test. The aim of this study was to investigate the relationship between mechanical properties and the wear resistance of titanium and Ti-Fe alloys. The dimensions (length, width and depth) of wear marks on Ti-Fe alloys were less than those observed on pure Ti...

To characterize concentrated growth factors (CGFs) in vivo, we examined the degradation of implanted CGF in rabbits. Untreated CGF (U-CGF) and compressed CGF (C-CGF) were subcutaneously implanted into the dorsum. Histological analyses showed that the U-CGF and C-CGF induced very few inflammatory cells and that the U-CGF and C-CGF were subsequently...

This study investigated the bactericidal effect, the underlying mechanisms of treatment, and recovery of biocompatibility of the infected titanium surface using a combination treatment of silver ion application and ultraviolet-A (UV-A) light irradiation. Streptococcus mutans and Aggregatibacter actinomycetemcomitans were used in suspension and as a...

This study explored modification of an alkaline heat treated titanium surface, using magnesium ions, to improve bone compatibility through the sustained release of magnesium ions. Pure titanium surface was first subjected to alkaline treatment using 5 M NaOH then modified with magnesium through immersion in magnesium chloride solution before heatin...

The aim of this study was to construct a Ti-Nb-Cu ternary phase diagram that plays the role of a map for developing new titanium alloys with excellent machinability and mechanical properties. Fifteen experimental Ti-Nb-Cu ternary alloys composed of Ti-5–30%Nb-2–20%Cu were designed, and ingots made using Ar-arc melting furnace before casting to gene...

Corrosion resistance of cast dental Ti-Mn alloys containing between 5 and 20 mass％ of Mn in solutions specified in ISO 10271 was investigated. Anodic polarization curves of Ti-Mn alloys displayed a wide passive region and low passivation current density across the different compositions. The behavior of the Ti-Mn alloys was similar to that of Ti. S...

The mechanical properties —tensile strength, yield strength, elongation after fracture, and Vickers hardness— and alloy phases of the dental cast alloys Ti-6%Nb-4%Cu, Ti-18%Nb-2%Cu, and Ti-24%Nb-1%Cu were investigated. Ti-6%Nb-4%Cu consisted of a single α-phase, while Ti-18%Nb-2%Cu and Ti-24%Nb-1%Cu consisted of α-and β-phases. The tensile strength...

This study aimed to fabricate a growth factor-releasing biodegradable scaffold for tissue regeneration. We prepared multishell calcium phosphate (CaP) nanoparticles functionalized with DNA, polyethyleneimine (PEI), protamine and octa-arginine (R8) and compared their respective transfection activity and cell viability measures using human mesenchyma...

Titanium is difficult to machine because of its intrinsic properties. In a previous study, the machinability of titanium was improved by alloying with silver. This study aimed to evaluate the durability of tungsten carbide burs after the fabrication of frameworks using a Ti-20%Ag alloy and titanium with a computer-aided design and computer-aided ma...

The mechanical properties -tensile strength, yield strength, elongation after fracture, Vickers hardness, and Young's modulus-and the phases of Ti-Ag alloys were investigated, as prepared with 22.5, 25, 27.5, and 30 mass% Ag. The tensile strength, yield strength, hardness, and Young's modulus of the alloys increase with their Ag content up to 25 ma...

Polymethyl methacrylate (PMMA)-made prostheses used in the oral cavity were evaluated by multimodal assessment in order to elucidate the biodeterioration of PMMA. In used dentures (UD), the micro-Vickers hardness of the polished denture surface and denture basal surface was lower than that of the torn surface (p<0.05), whereas the shaved surface ap...

The corrosion resistance of different magnetic assemblies -Magfit DX800 (Aichi Steel), Gigauss D800 (GC), Hyper Slim 4013, and Hicorex Slim 4013 (Hitachi Metals)- were electrochemically evaluated using anodic polarization curves obtained in 0.9% NaCl solution at 37°C. Stainless steels (444, XM27, 447J1, and 316L) composing the magnetic assemblies w...

Pure titanium has excellent biocompatibility. However, due to its low thermal conductivity and high chemical reactivity, the machining of pure titanium is very difficult. Therefore, pure titanium is not widely used in dental materials. Recently, we developed Ti-Ag alloys and investigated their properties. The machining properties of Ti-Ag alloys we...

Titanium-silver (Ti-Ag) alloy has been improved for machinability and mechanical properties, but its anti-biofilm properties have not been elucidated yet. Thus, this study aimed to evaluate the effects of Ti-Ag alloy on biofilm formation and bacterial viability in comparison with pure Ti, pure Ag and silver-palladium (Ag-Pd) alloy. Biofilm formatio...

The effects of the β-stabilizing elements (Ag, Au, Co, Cr, Cu, Fe, Mn, and Pd) on the characteristics of the experimental binary titanium alloys were examined with respect to mechanical properties, high temperature reactivity, corrosion resistance, grindability and machinability. The addition of β stabilizers to titanium lowers the fusion temperatu...

We developed experimental Ti–Ag alloys and characterized their ­properties. The mechanical properties and machinability of the Ti–Ag alloys were superior to those of pure titanium. The Ti–Ag alloy surfaces inhibited biofilm formation by Streptococcus mutans. The spontaneous formation of calcium phosphates on the Ti–Ag alloys upon immersion in simul...

The purpose of this study was to establish a geometric design method for the occlusal outlines of complex inlay cavities as a continuation study of a previous design method for simple class I inlay cavity. A method for extending the occlusal outline to the buccal or lingual groove and to three preparation types of the proximal portions of class II...

The purpose of this study was to evaluate the corrosion resistance of experimental Ti-Ag alloys used as dental materials. An elution test and a rest-potential measurement of alloys with 5–30 mass.% Ag were performed in a 1 % lactic acid solution. The amount of Ti ions released from the α phase of the Ti-Ag alloys decreased as the Ag concentration i...

The purpose of this study was to improve the grindability of titanium by alloying with zirconium. The grindability of dental cast Ti-Zr binary alloys (10, 20, 30, 40 and 50 mass%Zr) was evaluated using a carborundum wheel. The Ti-Zr alloys up to 30 mass%Zr formed an α structure, and the 40 mass^Zr and 50 mass%Zr alloys formed an a structure. The Ti...

The purpose of this study was to evaluate the corrosion resistance of experimental dental Ti-Ag alloys in 0.9% NaCl solution. Open-circuit potential (OCP) measurement and elution tests of the alloys with 5-30% Ag were performed. The amounts of both Ti and Ag ions released from the alloys with Ag ≤ 20% were below the detection limit. A very small am...

We prepared experimental Ti–Ag alloys and investigated their properties. The strength and hardness of the Ti–Ag alloys increased We prepared experimental Ti–Ag alloys and investigated their properties. The strength and hardness of the Ti–Ag alloys increased with the concentration of Ag. Moreover, the alloys exhibited sufficient elongation, making t...

The retentive force of wire clasp made of a low Young’s modulus β-type Ti–6Mo–4Sn alloy (β-Ti-alloy) was evaluated using a piezoelectric transducer to determine an appropriate undercut (UC) for the retainer of removable partial dentures. There were no significant differences between the retentive force of a β-Ti-alloy wire with a 0.50 mm UC and tha...

The retentive force of a wire clasp composed of a b-type Ti-6Mo-4Sn alloy (b-Ti alloy) with a low Young modulus was evaluated using a piezoelectric transducer to determine the appropriate undercut for removable partial dentures. There were no significant differences in retentive force between a b-Ti alloy wire with a 0.50-mm undercut and a cobalt-c...

Ti-Ag alloys with 20 and 25 mass% Ag were prepared; their surfaces were polished using silicon carbide abrasive papers. The polished alloys were immersed in a simulated body fluid (SBF), and their surfaces were observed by scanning electron microscope (SEM) to investigate the spontaneous formation of calcium phosphates. The precipitates formed on t...

The purpose of this study was to improve the grindability of titanium by alloying with zirconium. The grindability of dental cast Ti-Zr alloys (10, 20, 30, 40 and 50 mass% Zr) was evaluated using a carborundum wheel. The Ti-Zr alloys up to 30 mass% Zr formed an α structure, and the 40 mass% Zr and 50 mass% Zr alloys formed an α′ structure. The Ti-4...

This study is an investigation of the machinability of experimental Ti-Cu alloys (2, 5, and 10 mass% Cu) as new dental titanium alloy candidates for CAD/CAM use. The alloys were slotted with a vertical milling machine and carbide square end mills under two cutting conditions. Their machinability was evaluated through cutting force using a three-com...

This study investigated the machinability of experimental Ti-Ag alloys (5, 10, 20, and 30 mass% Ag) as a new dental titanium alloy candidate for CAD/CAM use. The alloys were slotted with a vertical milling machine and carbide square end mills under two cutting conditions. Machinability was evaluated through cutting force using a three-component for...

This study is an examination of the released ions from dental cast experimental Ti-Ag alloys by an immersion test. Ti-Ag alloys (5–25mass%Ag) and pure titanium (control) were cast into magnesia molds; the hardened surface layer was then removed. After each specimen was immersed in aerated 0.9% NaCl or 1% lactic acid solution at 37°C for 7 days, rel...

The Young’s moduli of experimental binary titanium alloys with Cu, Ag, Au, Zr, Nb, or Hf (up to 30 mass%) were determined. As the concentration of Cu increased, the Young’s modulus monotonically increased. As the concentration of Ag, Au, or Nb increased to 20%, the Young’s modulus decreased, followed by a subsequent increase in value. The Young’s m...

Anodic polarization tests were performed in 0.9% NaCl and 1% lactic acid solutions to characterize the relationship between the corrosion behavior and the microstructures of cast Ti-Ag (5-40% Ag) alloys. The anodic polarization curves for the Ti-Ag alloys up to 17.5% Ag were similar to those for pure titanium in both solutions. On the other hand, a...

This study investigated the effect of alloying titanium with gold, silver, or copper on the elastic properties of the alloys. A series of binary titanium alloys was made with four concentrations of gold, silver, or copper (5, 10, 20, and 30 mass%) in an argon-arc melting furnace. The Young's moduli and Poisson's ratios of the alloy castings were de...

As part of our systematic studies characterizing the properties of titanium alloys, we investigated the grindability of a series of cast Ti-Hf alloys. Alloy buttons with hafnium concentrations up to 40 mass% were made using an argon-arc melting furnace. Each button was cast into a magnesia-based mold using a dental titanium casting machine; three s...

Experimental Ti–Au (5–20 mass% Au), Ti–Ag (5–20 mass% Ag) and Ti–Cu (2–10 mass% Cu) alloys were made. Mechanical properties and grindability of the alloys were examined. The hardness and tensile strength became higher and the elongation became lower than pure titanium. The grindability of titanium was improved by alloying with silver or copper, esp...

Anodic polarization was performed in 0.9% NaCl and 1% lactic acid solutions to characterize the relationship between the corrosion behavior and microstructures of cast Ti-Au (5-40%) alloys. An abrupt increase in the current density occurred at approximately 0.6 V vs. SCE for the 30% and 40% Au alloys in the 0.9% NaCl solution. The microstructures a...

Experimental Ti-Au alloys (5, 10, 20 and 40 mass% Au) were made. Mechanical properties and grindability of the castings of the Ti-Au alloys were examined. As the concentration of gold increased to 20%, the yield strength and the tensile strength of the Ti-Au alloys became higher without markedly deteriorating their ductility. This higher strength c...

Aiming at developing a dental titanium alloy with better mechanical properties and machinability than unalloyed titanium, a series of Ti-Nb alloys with Nb concentrations up to 30% was made. They were cast into magnesia-based molds using a dental casting machine and the mechanical properties and grindability of the castings were examined. The hardne...

Experimental Ti-Ag alloys (5, 10, and 20 mass% Ag) and Ti-Cu alloys (2, 5, and 10 mass% Cu) were cast into magnesia molds using a dental casting machine, and their grindability was investigated. At the lowest grinding speed (500 m min(-1)), there were no statistical differences among the grindability values of the titanium and titanium alloys. The...

In this study, experimental Ti-Ag alloys (5, 10, and 20 mass% Ag) and Ti-Cu alloys (2, 5, and 10 mass% Cu) were made in an argon-arc melting furnace. The alloys were cast into magnesia molds using an argon gas-pressure dental casting machine, and the mechanical properties and microstructures of the castings were investigated. As the concentration o...