JP3511542B2 - Titanium implant material for living body - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium implant material for living body, which has excellent corrosion resistance in vivo. More specifically, dentistry having sufficient strength as a bone substitute material and a bone reinforcing material, and having excellent biocompatibility and corrosion resistance in vivo, capable of increasing the fixing force with bone tissue,
An implant material useful in fields such as orthopedics is provided.

[0002]

2. Description of the Related Art In recent years, in the fields of orthopedic surgery and oral surgery, artificial bones, artificial tooth roots, etc. have been implanted in a living body. Especially when it comes to bone damage,
Embed artificial bone in the damaged area or reinforce or fix it until the bone is healed. Bone transplantation is also performed in spinal surgery.

In general, stainless steel and chromium-cobalt-based materials are often used as such artificial bones, joint materials or bone-reinforcing materials for these. However, stainless steel and chrome-cobalt alloys contain elements that are harmful to the human body, and there are many reports that malignant tumors were observed after artificial joint replacement. As described above, the elution of toxic metal ions in vivo has recently been regarded as a problem.

As described above, stainless steel is generally said to be a corrosion resistant material, but in a highly corrosive environment such as a living body, pitting corrosion or corrosion fatigue is likely to occur and it is easily destroyed. In addition, when the corrosion-resistant film (passive film) on the surface is partially destroyed due to the occurrence of scratches on the stainless steel itself during surgery or use, the passive film usually regenerates rapidly in the atmosphere. However, since the oxygen partial pressure in the body is low, the dough may be exposed for a long period of time, and metal ions such as nickel, which is the main additive component element of stainless steel, may be eluted. It has been reported that metallic nickel itself has toxicity as an allergic or carcinogenic substance.

Biocompatibility No cytotoxicity or nontoxicity per se Not elution as metal ion Good compatibility with living tissue Carcinogenicity and no antigenicity No metabolic disorders No blood coagulation or hemolysis No in vivo degradation or decomposition No adsorptivity or precipitate

Mechanical Properties Appropriate static (tensile, compression, bending, shear) strength and ductility Must have sufficient fatigue strength Excellent machinability

[0007]

Because of the problems as described above, it has come to be avoided to use a toxic metal or an alloy material containing the toxic metal as a component.

As a result, titanium materials, which are excellent in corrosion resistance and lighter in weight, have come to be paid attention as materials replacing stainless steel and chromium-cobalt materials. This titanium material is roughly classified into pure titanium and titanium alloy. The strength of pure titanium changes depending on the amount of oxygen.
In the standard, the ones with low oxygen content are classified into 1 to 3 types.

On the other hand, titanium alloys include V, Mo, Fe and Cr.
As the β-stabilizing element increases, the β-phase will exist up to room temperature, but depending on the presence or absence of this β-phase, α-type, α-
It is classified into β type and β type. Among the titanium alloys, Ti-6Al-4V is known for medical use. It is defined as a surgical implant material in American ASTM and ISO standards. However, some researchers have pointed out the danger of this alloy because it contains V, which is said to exhibit strong cytotoxicity when used alone. Therefore, a V-free titanium alloy for biological use is also being developed. It is being appreciated.

It is generally considered that titanium has no particular concern for cytotoxicity, but when artificial bone and a bone reinforcing material or a fastening wire for living body are used at the same place,
Since the contact portion between the both is soaked in the body fluid in the living body, there is a great risk that electrochemical corrosion will occur. This is especially noticeable when using dissimilar materials such as stainless steel.
Therefore, when using pure titanium or titanium alloy as a biomedical implant material such as artificial bone, it can be said that it is desirable to use the same kind of titanium material.

It is said that titanium material is inferior in mechanical strength and elongation to stainless steel, and is a pure titanium material specified by ASTM (and JIS standard) suitable as a biomedical implant? It is the current situation that no conclusion has been reached yet.

As such an implant material made of pure titanium, two kinds of JIS standard pure titanium have been proposed (Japanese Patent Laid-Open Publication No. 6-58242).
-125978 and JP-A-5-23355).

However, the above-mentioned JIS standard pure titanium (hereinafter referred to as “CP titanium”) is advantageous in that it has good machinability and is superior in corrosion resistance to other materials. If the formation of the passivation film formed on the surface of titanium is not always sufficient, it has a possibility of being eluted as ions. It is also reported that titanium is also harmful to the human body when it is eluted at a high concentration, and since it is used in vivo as a bone substitute material or a reinforcing material for a long time, these are problems that cannot be ignored. Also, C
Even with P-titanium, a certain amount of metal components and the like are present as impurities, which causes local disorder in the structure of the surface oxide film, resulting in deterioration of corrosion resistance.

Under these circumstances, attempts have been made to improve the corrosion resistance by alloying, but this is to concentrate elements having high corrosion resistance on the surface by initial elution, and to improve the corrosion resistance when alloyed. This means that elution of a certain amount of metal is required for the purpose. In addition, it is expected that recovery of this corrosion resistance mechanism will be significantly delayed when the corrosion resistant coating of the alloy is destroyed in the human body.
Therefore, titanium alloys have not yet reached a fundamental solution.

[0015]

Means for Solving the Problems As a result of earnest tests and studies on the above problems, the present inventors have made it possible to more strictly adjust the amount of titanium-containing components.
The present invention has been accomplished by finding an excellent material that can be adapted as a biomedical implant material having improved workability and strength while improving corrosion resistance in vivo.

As described above, CP titanium has a problem that the passivation film (oxide film) is not formed quickly and sufficiently, but in the present invention, the passivation film is promoted by increasing the purity of titanium. By controlling the elements that interfere with the formation of the chemical film (oxide film) to the utmost limit, the corrosion resistance as an implant material is dramatically improved. That is, the present invention provides an excellent titanium implant material for a living body in which a corrosion resistant film is rapidly formed and can be quickly regenerated even if it is destroyed by deformation or the like.

[0017] The first aspect of the present invention, the total amount of the gas components of oxygen as the main component is 10～4000Ppm, the upper limit is 100 ppm, the remainder titanium content of the component other than the gas component, before
The upper limit of the amount of hydrogen contained as a gas component is 50 pp
m, upper limit of nitrogen content is 200 ppm, upper limit of carbon content is 40
The present invention relates to a titanium implant material for living body, which has a content of 0 ppm .

Next, the second invention is characterized in that an oxide film is formed on the surface by anodic oxidation, heat oxidation, molten hydrochloric acid, etc., and the total amount of gas components containing oxygen as a main component is 10 to 10. 4000 ppm (excluding oxygen contained in the oxide film on the surface), the upper limit of the content of the component other than the gas component 100
ppm, balance titanium, contained as the gas component
Upper limit of hydrogen content is 50ppm, upper limit of nitrogen content is 200
The present invention relates to an implant material made of titanium for living body having an upper limit of ppm and carbon amount of 400 ppm .

Next, the third invention is a tensile strength (TS).
Is 175 MPa or more and the elongation (El) is 10% or more , and relates to the titanium implant material for a living body according to the first or second aspect of the present invention.

Next, a fourth invention is a fastening titanium titanium for living body.
The present invention relates to the titanium implant material for living body according to the first to third aspects of the invention excluding the ear .

[0021]

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention and the operation thereof will be described below. First, the reasons for limiting oxygen contained in the titanium implant material for living body of the present invention will be described in detail.

Oxygen (O): In the present invention, the total amount of gas components containing oxygen as a main component is set to 10 to 4000 ppm. For rapid formation of the passivation film (oxide film), it is necessary to limit the amount of alloying elements and impurity elements contained in titanium as much as possible, but the reduction in strength cannot be denied. As will be described later, the improvement in strength can be controlled also by the recrystallization structure by plastic working or heat treatment, but the strength can be largely maintained by adjusting the oxygen content. The presence of oxygen in titanium does not affect the formation of passivation film (oxide film), at least 10 ppm
It is desirable to contain the above. Strength also improves as the amount of oxygen increases.

The surface of the titanium implant material for living body is subjected to anodic oxidation, heat oxidation or molten hydrochloric acid treatment,
An oxide film can be formed in advance. Thereby, the uniform and dense oxide film can significantly improve the corrosion resistance. Total amount of the gas component containing oxygen as the main component 1
The amount of oxygen contained in this surface oxide film is excluded from 0 to 4000 ppm.

Hydrogen (H): In the present invention, hydrogen is 50
It should be below ppm. Hydrogen affects ductility in a smaller amount than oxygen. Further, in terms of quickly forming a uniform and dense oxide film, it is rather a hindrance factor, so it is better to minimize it. When the hydrogen content exceeds 50 ppm, the ductility sharply deteriorates even if other impurities are reduced.

Nitrogen (N): In the present invention, nitrogen is 20
It should be 0 ppm or less. Nitrogen has a ductility reduction of about 1.5 times that of oxygen. If the nitrogen content exceeds 200 ppm, the ductility deteriorates sharply even if other impurities are reduced,
Further, in the sense that a uniform and dense oxide film can be rapidly formed, it becomes a hindering factor, so it is necessary to reduce it as much as possible.

Carbon (C): In the present invention, carbon is 40
It should be 0 ppm or less. Carbon exists as an interstitial solid solution element in Ti and acts to increase the strength of Ti.
On the contrary, this is about 0.75 times less ductility than that of oxygen at the same concentration. If the carbon content exceeds 400 ppm, the ductility sharply deteriorates even if other impurities are reduced. Further, in the sense that a uniform and dense oxide film can be rapidly formed, it becomes a hindering factor, so it is necessary to reduce it as much as possible.

Components other than gas components: In the present invention, the content of components other than gas components is 100 ppm or less. In order to form a passive film (oxide film) uniformly and densely as a biomedical implant material, it is necessary to reduce the content of components other than gas components as much as possible. In particular, for bone substitutes and the like to be implanted in the body for a long time, even if the oxide film is destroyed for some reason, it is necessary for the material to be able to quickly regenerate the film again in the body. The titanium implant material of the present invention can form an oxide film more quickly even under a low oxygen partial pressure in the body.

Description of tensile strength and proof stress In the above, the components mainly contained in the titanium implant material for living body have been described. However, sufficient tensile strength and physical strength are required as a bone substitute material and a bone reinforcing material. To be done. 175MP for tensile strength and physical strength
It is desirable to have a, 70 MPa or more.

The presence of oxygen to the extent described above is rather preferred because the oxygen described above usually results in an increase in the strength of titanium. However, the presence of excess tends to reduce workability and make it brittle.

As described above, strength and high ductility are indispensable for the biomedical implant material. Generally, the tensile strength and proof stress are 175M each as described above.
If Pa and 70 MPa or more are retained, there is no practical inconvenience, and it is suitable as a biomedical implant material.

When it is desired to increase the strength as much as possible in the case of joining bones to which a large load is applied, it is necessary to take structural measures or increase the diameter of the material.
Moreover, since the strength can be increased by plastic working, such a method is adopted as necessary. The biomedical implant material of the present invention sufficiently satisfies the above conditions.

Next, the average crystal grain size will be described. In the present invention, the average crystal grain size is 2 μm to 150 μm.
It is desirable to set m. The smaller the crystal grain size, the higher the toughness. However, in reality, if the grain size is less than 2 μm, it is difficult to manufacture, and even if it can be manufactured, some strain remains and the ductility value decreases.
On the other hand, when the average crystal grain size is large, particularly when it exceeds 150 μm, the number of crystal grains is reduced, the ductility is locally deteriorated, and the surface becomes rough during processing, which is not preferable in terms of processing accuracy.

Next, details of the manufacturing method will be described.
A titanium material having predetermined components prepared is melt-cast to produce a titanium ingot. Gas components oxygen, nitrogen,
A vacuum arc melting method, an electron beam melting method, or the like can be used to remove impurities such as hydrogen and carbon to a predetermined amount or less. The obtained titanium ingot is forged as required, and then rolled, pressed or the like to be formed into a predetermined shape.

Intermediate annealing (400-
The temperature range is 900 ° C., preferably 500 to 700 ° C., more preferably 550 to 650 ° C., for about 10 seconds to 5 hours).

After the final processing, a temperature range of 400 to 900 ° C., preferably a temperature range of 500 to 700 ° C., more preferably 5
Final annealing is performed in a temperature range of 50 to 650 ° C. for approximately 10 seconds to 5 hours. A predetermined crystal grain (for example, an average crystal grain size of 2 μm to 150 μm) is prepared through the above processing and annealing. The intermediate annealing and the final annealing can be either continuous or batch type. In this way, an implant material having a predetermined shape is manufactured. Further, in order to form an oxide film on the surface, a uniform and dense oxide film is formed by means such as anodic oxidation, heating oxidation, and molten hydrochloric acid after completion of plastic working or annealing.

As a result, the bone substitute material and the bone reinforcing material have sufficient strength and ductility, excellent corrosion resistance in vivo, and even if the oxide film is destroyed in vivo, the film can be rapidly formed. It is possible to provide an excellent biomedical implant material that can be regenerated.

[0038]

Example 1 and Comparative Example 1 CP-Ti (titanium) in which the content of components other than gas components such as iron exceeds the upper limit of the examples (examples) of the present invention suitable as implant materials for living bodies
Also, a comparison with a comparative example of stainless steel (SUS316L) will be described.

A sample of each titanium was prepared as follows. The titanium material with the adjusted components was melted and cast by the electron beam melting method to obtain ingots of the respective components. These ingots were further forged and cold rolled into a plate material. During this processing, intermediate annealing was appropriately performed in the temperature range of 400 ° C to 900 ° C. Further, after the final cold working, final annealing was performed in a temperature range of 400 ° C to 900 ° C to obtain a recrystallized structure. Stainless steel as a comparative example (SUS3
For 16 L), a commercially available plate material was used. The plate material obtained above was cut into blocks of 10 × 10 × 5 mm, and a wire made of the same material was spot-welded and embedded in a water-insoluble polymer. This was polished with water-resistant polishing paper to expose a surface of 10 × 10 mm, and this surface was used as a measurement surface.

The analytical values of the chemical components of these samples are shown in Table 1. Sample 1 and sample 2 in Table 1 are the chemical analysis values of the example of the present invention, sample 3 (CP-Ti) and sample 4.
(Stainless steel) shows the chemical analysis value of the comparative example. Sample 3 has a high iron (Fe) content, and is 0.03% by weight (300 p
pm) contained.

[0041]

[Table 1]

Corrosion Resistance Test (Kinematic Potential Polarization Curve) For each titanium sample, the surface to be measured was # 600 with water-resistant abrasive paper.
After polishing, chemical polishing was performed with a polishing liquid composed of hydrofluoric acid-hydrogen peroxide water-water, washed with pure water, and then immersed in the measurement liquid without direct contact with the atmosphere. In addition, stainless steel (S
US316L) was prepared by buffing the measurement surface to a mirror surface, then washing with pure water as in the case of the titanium sample, and then immersing it in the measurement liquid without directly touching the atmosphere.

The measurement conditions are as follows. Electrolyte solution; Hank's solution deoxidized by Ar, solution temperature; 31
0K reference electrode; Ag / AgCl, counter electrode; Pt, potential sweep rate;
The result of 40 mV / min or more is shown in FIG.

Results of Corrosion Resistance Test Both titanium and stainless steel (SUS316L) show potentiodynamic polarization curves in the state where no passive film is present on the initial surface. As is clear from FIG. 1, titanium samples 1 and 2 which are examples of the present invention have a natural immersion potential on a nobler side than titanium sample 3 which is a comparative example, and titanium sample 3 which is a comparative example due to formation of a corrosion resistant film. The current value is lower than. From this, it is understood that the titanium samples 1 and 2 of the present invention have high corrosion resistance. Sample 4 stainless steel (SUS316
In L), the current value rises immediately, so the corrosion resistance is worse than any titanium material. Further, as is clear from FIG. 1, in the titanium samples 1 and 2 of the present invention, the rising of the current is sharp at the initial stage of polarization, and the oxide film is rapidly formed.
This means that even if the oxide film is destroyed in the body, the oxide film reforms faster than other corrosion resistant materials, and it has the excellent feature that it is suitable as a biomedical implant material. I understand.

[0045]

Example 2 and Comparative Example 2 Titanium and stainless steel (SUS316L) were processed in the same steps as in Example 1 and Comparative Example 1.
An original sample was prepared, the measurement surface was finished, and the following surface treatment was performed to obtain a sample. The chemical components are the same as in Example 1 and Comparative Example 1. The difference is that an oxide film is formed in advance by anodic oxidation. Titanium sample is oxalic acid
Anodization was performed in a sulfuric acid bath using SUS304 as a cathode.
The oxidation voltage at this time is 6.5V. After anodic oxidation, it was washed with pure water and then immersed in the measurement liquid without directly contacting the atmosphere. Stainless steel (SUS316L) sample is AST
According to the method of MF-86, it was dipped in nitric acid for 30 minutes, washed with pure water, and then dipped in the measurement liquid without being in direct contact with the atmosphere.

The measurement conditions are as follows. Electrolyte solution; Hank's solution deoxidized by Ar, solution temperature; 31
0K reference electrode; Ag / AgCl, counter electrode; Pt, potential sweep rate;
The result of 40 mV / min or more is shown in FIG.

As a result of the corrosion resistance test, each of titanium and stainless steel (SUS316L) is a potentiodynamic polarization curve with a passive film formed on the surface.
As is clear from FIG. 2, titanium samples 1 and 2 which are examples of the present invention are titanium samples 3 whose natural immersion potential is a comparative example.
It is on the more noble side and has a lower current value than the titanium sample 3 of the comparative example due to the formation of the corrosion resistant film. From this, it is understood that the titanium samples 1 and 2 of the present invention have high corrosion resistance. Although the stainless steel (SUS316L) of the comparative sample 4 is on the noble side of the titanium sample, the corrosion resistance is worse than any of the titanium materials because the current value rises rapidly. Further, as is clear from FIG. 2, the titanium sample 1 of the present invention
It can be seen that the samples Nos. 2 and 2 have a lower current rise and are superior in corrosion resistance to the titanium sample of the comparative example.

As is clear from the above, any titanium material of the present invention can be used with other titanium materials and stainless steel (SUS31).
6L), the corrosion resistance is significantly higher and the oxide film is formed more quickly. This means that even if the oxide film is destroyed in the body, the reformation of the oxide film is faster than other corrosion-resistant materials, and it has an excellent feature that it is suitable as a biomedical implant material.

[0049]

INDUSTRIAL APPLICABILITY As shown in the above detailed description and Examples of the present invention, the present invention provides a titanium implant material for living body which is excellent in corrosion resistance in the living body. That is, in the fields of dentistry, orthopedics, etc., which have sufficient strength as a bone substitute material and a bone reinforcement material, and are excellent in biocompatibility and corrosion resistance in vivo, and which can increase the fixing force with bone tissue A useful implant material is provided.

Titanium is already known to be good in fatigue strength, tensile strength, corrosion resistance, and biocompatibility, but in the present invention, the important problem of fastening property which has been a problem in the past. Is the solution.

[Brief description of drawings]

FIG. 1 is a potentiodynamic polarization curve of titanium and stainless steel of Example 1 and Comparative Example 1 in which a passive film is not formed on the surface.

FIG. 2 is a potentiodynamic polarization curve of titanium and stainless steel of Example 2 and Comparative Example 2 in which a passive film was formed on the surface by anodic oxidation.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeaki Shimada 4 187 Usuba, Hwagawa Town, Kitaibaraki City, Ibaraki Prefecture Japan Energy Co., Ltd.-Isohara Factory (56) Reference JP-A-8-164195 (JP, A) JP-A-5-23355 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) A61L 27/00 A61C 8/00

Claims (4)

(57) [Claims] 1. The total amount of gas components containing oxygen as a main component is 1
0～4000Ppm, the upper limit of the content of the component other than the gas component 100 ppm, and the balance titanium, and the gas component
The upper limit of the amount of hydrogen contained by 50ppm, the upper limit of the amount of nitrogen
Is 200 ppm, and the upper limit of carbon content is 400 ppm . 2. A total amount of a gas component containing oxygen as a main component is 10 to 4000 pp, characterized in that an oxide film is formed on the surface by anodic oxidation, heat oxidation, molten hydrochloric acid oxidation, or the like.
m (excluding oxygen contained in the oxide film on the surface), the upper limit of the content of the component other than the gas component 100 ppm, with the balance titanium
And the upper limit of the amount of hydrogen contained as the gas component is 5
0ppm, upper limit of nitrogen amount is 200ppm, upper limit of carbon amount
The implant material made of titanium for living body having a content of 400 ppm . 3. The tensile strength (TS) is 175 MPa or less.
The titanium implant material for living body according to claim 1 or 2 , wherein the elongation (El) is 10% or more . 4. The implant material made of titanium for living body according to claim 1 , excluding the fastening titanium wire for living body.