Grindability of Ti−Nb−Cu Alloys for Dental Machining Applications

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 Ti-24%Nb-1%Cu alloys significantly exceeded that of unalloyed titanium at high, medium, and low grinding speeds, respectively. Additionally, the Ti-6%Nb-4%Cu alloy exhibited an excellent grinding ratio. Generally, materials with high strength and hardness frequently exhibit poor machinability; however, the Ti−Nb−Cu alloys developed in our study presented favorable grindability characteristics and, therefore, demonstrated good potential for application as dental titanium alloys that can be subjected to computer-aided design/manufacturing processes

Grindability of Ti−Nb−Cu Alloys for Dental Machining Applications

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 Ti-24%Nb-1%Cu alloys significantly exceeded that of unalloyed titanium at high, medium, and low grinding speeds, respectively. Additionally, the Ti-6%Nb-4%Cu alloy exhibited an excellent grinding ratio. Generally, materials with high strength and hardness frequently exhibit poor machinability; however, the Ti−Nb−Cu alloys developed in our study presented favorable grindability characteristics and, therefore, demonstrated good potential for application as dental titanium alloys that can be subjected to computer-aided design/manufacturing processes

Development of Ternary Ti-Ag-Cu Alloys with Excellent Mechanical Properties and Antibiofilm Activity

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 added copper (Cu) as an alloying element to improve strength. This study aimed to develop ternary Ti-Ag-Cu alloys with excellent mechanical properties and antibiofilm activity. As a result of investigating the mechanical properties of several experimental alloys, the tensile strength, yield strength, and hardness of Ti-20%Ag-1%Cu and Ti-20%Ag-2%Cu alloys were improved by the solid-solution strengthening or hardening of the αTi phase. In addition, these alloys had the same ability to suppress biofilm formation as the Ti-20Ag alloy. Thus, Ti-20%Ag-1–2%Cu alloys can be used for fabrication of narrow-diameter dental implants and prostheses subjected to extremely high force, and these prostheses are useful in preventing post-treatment oral diseases

Mechanical Properties of Ti-Nb-Cu Alloys for Dental Machining Applications

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 properties, including tensile and yield strength, elongation after fracture, and Vickers hardness. The alloy phases of Ti-8%Nb-2%Cu and Ti-13%Nb-2%Cu were α + β, while those of Ti-5%Nb-5%Cu and Ti-10%Nb-5%Cu were α + Ti2Cu. The tensile strength and hardness of these alloys were significantly higher than those of titanium; however, their elongation was less. In particular, the yield strength of these alloys was more than twice that of titanium. These differences in mechanical properties are attributable to solid–solution strengthening and precipitation strengthening. Other compositions with an alloy phase of α + β + Ti2Cu or β + Ti2Cu had high hardness but not high strength. These results suggest that the Ti-8%Nb-2%Cu, Ti-5%Nb-5%Cu, Ti-13%Nb-2%Cu, and Ti-10%Nb-5%Cu alloys can be applied to dental prostheses, which are subject to very high forces from accessories such as long-span bridges, clasps, implant-retained superstructures, and narrow-diameter implants

The Effect of Electroless Nickel–Polytetrafluoroethylene Coating on the Frictional Properties of Orthodontic Wires

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 PTFE particles with a low coefficient of friction on the coating surface to provide a low-friction surface for metallic materials. The purpose of this study was to investigate the effect of Ni-PTFE-coated orthodontic wires on the frictional force between brackets. The surface morphology, surface roughness, and frictional properties of Ni-PTFE-coated stainless steel wires and Ni-Ti wires were evaluated. The results demonstrate that the Ni-PTFE coating reduced the frictional force between the orthodontic wires and brackets, despite the increased surface roughness. Even when the angle between the wire and bracket was increased, assuming binding friction, the frictional force was reduced by the Ni-PTFE coating. This suggests that the friction between the wire and the bracket was suppressed by the PTFE particles deposited on the wire surface in contact with the bracket