JP7779473B2 - Titanium alloy - Google Patents

Description

The present invention relates to titanium alloys. In particular, it relates to titanium alloys that are suitable for use in dental prostheses and medical devices.

In medical settings, applications that primarily involve direct contact with living organisms require that materials have as little impact on the organism as possible. For this reason, highly biocompatible materials with low cytotoxicity and allergenicity, such as precious metals and titanium alloys, have traditionally been used. However, in addition to the effects of the materials themselves on the organism, it has been pointed out that biofilms formed by bacteria and exopolysaccharides on the surface of materials during use within the body can cause various diseases in the organism, and conventional materials have been insufficient in preventing biofilm formation. For this reason, titanium-silver alloys with biofilm adhesion and growth inhibitory properties (hereafter referred to as bacteriostatic properties) have been proposed.

Patent Document 1 discloses a titanium-silver alloy that, by adding silver to titanium, controls the surface properties of the metal, reducing its impact on the normal bacterial flora in the oral cavity and inhibiting the formation of biofilms that can have harmful effects on the living body.

Patent Publication No. 2010-121153

However, while the titanium-silver alloy described in Patent Document 1 has the workability to be processed into any shape required for dental prostheses and medical device manufacturing, and maintains its antibacterial properties over the long term, there is room for improvement in its mechanical properties when applied to dental prostheses and medical devices such as guide wires, stents, and implants. Mechanical properties are particularly important for large dental prostheses such as dentures and bridges, which are subject to significant loads due to occlusion, and there is a demand for materials that combine antibacterial properties, workability, and high mechanical properties.

The object of the present invention is to provide a titanium alloy that is antibacterial and easy to process, while also possessing high mechanical properties that make it suitable for use in dental prostheses and medical devices.

After extensive research, the inventors have developed a titanium alloy that combines Ti, Ag, Nb, and Cu in an optimal composition range, resulting in antibacterial properties, workability, and excellent mechanical properties.

That is, the above-mentioned objectives are achieved by a titanium alloy characterized by 3 to 25 mass% Ag, 0.5 to 30 mass% Nb, 0.1 to 7.5 mass% Cu, and the balance being Ti. This titanium alloy can be used, for example, as a material for dental prosthetics and as a material for medical devices.

The present invention makes it possible to provide a titanium alloy that has antibacterial properties and workability, while also possessing the high mechanical strength required for dental prostheses and medical devices such as guidewires, stents, and implants.

The following describes in detail an embodiment of the present invention.

The present invention is a titanium alloy characterized by 3 to 25 mass% Ag, 0.5 to 30 mass% Nb, 0.1 to 7.5 mass% Cu, and the balance being Ti.

Adding Ag to alloys imparts antibacterial properties. If the amount added is less than 3 mass%, antibacterial properties are poor, while if it exceeds 25 mass%, elongation becomes insufficient. The preferred amount is 4 to 23 mass%.

By adding Nb and Cu simultaneously to a TiAg alloy, it is possible to improve hardness and yield strength while maintaining antibacterial properties. Adding Nb alone does not improve hardness or yield strength, and adding only Cu in the amount necessary to improve hardness and yield strength significantly reduces workability.

When Nb and Cu are added simultaneously, if the amount of Nb added is less than 0.5 mass%, sufficient workability cannot be obtained, and if it exceeds 30 mass%, the yield strength becomes insufficient. The amount of Nb added is preferably 0.7 to 27 mass%, more preferably 3 to 17 mass%.
On the other hand, if the amount of Cu added is less than 0.1 mass%, sufficient hardness and yield strength cannot be obtained, and if it exceeds 7.5 mass%, workability becomes insufficient. The preferred amount is 0.3 to 6 mass%.

The present invention will be explained in the following examples, but the manufacturing method is not limited to these embodiments.

The alloy compositions of the examples and comparative examples are shown in Table 1. The raw materials Ti, Ag, Nb, and Cu were weighed and mixed to obtain the compositions shown in Table 1. They were then melted in an argon atmosphere using an arc melting method to produce alloy ingots.

The produced ingots were hot forged, then hot rolled, and then heat treated to produce 2 mm thick plates (Examples 1-10, Comparative Examples 1-3).

The following evaluations were carried out on the sheets of each alloy produced. The results are shown in Table 2.

Workability was evaluated by processing the ingot into 2mm thick plates. Alloys from which 2mm thick plates could be obtained are marked with a 〇, and alloys from which cracks occurred during processing and 2mm thick plates could not be obtained are marked with an × in Table 2. Note that for alloys with an × in workability, test specimens could not be prepared, and the columns for the evaluation of antibacterial properties and each mechanical property are marked with a "-".

Bacteriostatic properties were evaluated using the following biofilm adhesion test. First, test pieces measuring 2 mm thick, 15 mm long, and 10 mm wide were cut from the test material. The sterilized test pieces were immersed in a container containing a sucrose-containing complex liquid medium, and Streptococcus mutans, a bacterium simulating oral biofilm formation, was added and anaerobically cultured for a specified period of time. The test pieces were then transferred to a container containing water and washed. After that, the attached biofilm was collected with a spatula and suspended in a specified amount of water. The biofilm volume was calculated from the turbidity. The smaller the biofilm volume, the better the bacteriostatic properties of the material. Bacteriostatic properties were evaluated as follows: if the reduction in biofilm volume of the alloy compared to pure Ti material was 10% or more, it was marked "Good"; if the reduction in biofilm volume of the alloy was less than 10% (including an increase in biofilm volume), it was marked "X." These are shown in Table 2.

Hardness was measured using a micro-Vickers hardness tester using test pieces 2 mm thick, 15 mm long, and 10 mm wide cut from the test material, with a load of 200 gf and a holding time of 10 seconds. The results are shown in Table 2. Hardness was evaluated as ◎ if it was 300 HV or higher, 〇 if it was less than 300 HV and 270 HV or higher, and × if it was less than 270 HV, and are shown in Table 2.

Yield strength was measured at room temperature in air at a crosshead speed of 1.5 mm/min using test pieces 2 mm thick, 50 mm long, and 3 mm wide cut from the test material. Comparative Example 1 is set to 100%, and the relative yield strengths of the Examples and other Comparative Examples relative to that of Comparative Example 1 are shown in Table 2. Furthermore, the yield strength ratio was evaluated as ◎ if it was 120% or greater, 〇 if it was less than 120% and 110% or greater, and × if it was less than 110%, and these results are shown in Table 2.

Elongation was determined from the butt joint elongation of the test specimen after the above tensile test. Elongation was evaluated based on the properties required for Type 5 (devices requiring high rigidity and high strength) of JIS T 6123 (non-precious metal materials for fixed dental restorations), with an elongation of 2% or more being evaluated as "Good" and an elongation of less than 2% being evaluated as "Poor." The results are shown in Table 2.

These results demonstrate that the alloys produced according to the present invention possess antibacterial properties and workability, while also possessing the mechanical properties required for dental prostheses and medical devices. Therefore, the present invention makes it possible to provide titanium alloys that are suitable for use in medical settings.

Claims (3)

A titanium alloy characterized by containing 3-25 mass% Ag, 0.5-30 mass% Nb, 0.1-7.5 mass% Cu, and the balance Ti, having a hardness of 270 HV or more, an elongation of 2% or more, and having antibacterial properties . The titanium alloy described in claim 1, characterized in that it is used for dental prostheses. The titanium alloy described in claim 1, characterized in that it is used for medical devices.