JPH11178912A - Bioprosthetic members - Google Patents

Abstract

(57) Abstract: Provided is a bioprosthesis member having a coating layer having excellent biocompatibility and high peel strength, and having high mechanical strength of a base. The static load strength of the substrate is set to 900 MPa or more, and the fatigue strength thereof is set to half or more of the static load strength. In the coating layer, the first peak of the calcium phosphate compound in X-ray diffraction is the first peak of titanium. It should be larger than one peak. Then, the thickness of the coating layer is set to 10
By reducing the thickness to less than a micron, a decrease in adhesion strength is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bioprosthetic member for replacing or prosthetic living tissue, and more particularly to a coating layer containing a bioactive material on the surface of a titanium-based metal substrate. With respect to what formed.

[0002]

2. Description of the Related Art Conventionally, in order to replace a high applied load portion in a living body with a prosthesis, a metal material such as ceramics such as alumina and zirconia, a titanium alloy and the like, which are non-hazardous to the living body and a high strength material, has been used for a living body. Attempts have been made to coat the high strength materials with bioactive materials in order to combine the advantages of bioactive materials, such as apatite, which coalesce with actively proliferating bone tissue.

With respect to ceramics, for example, zirconia ceramics have a porous surface and a slurry of hydroxyapatite is poured into the surface and baked, or a slurry of glassy powder containing calcium oxide and phosphoric acid is used. After the preparation, the slurry is applied to a ceramic substrate and fired at 1000 to 1200 ° C. to form a coat layer containing apatite crystals (Japanese Patent Application Laid-Open No. 1-242067).

[0004] By the way, as a metal material, a material obtained by applying an apatite slurry to the surface of a titanium alloy substrate by performing arc spraying of titanium or the like on a roughened surface and drying the surface is put into practical use.

Japanese Patent Application Laid-Open No. HEI 8-117324 relates to a method for producing a biological implant material in which a coating layer having excellent adhesion to bone is formed on the surface of a metal substrate containing titanium as a main component. It is characterized in that a paste containing a metal powder made of an alloy and a powder of a bioactive substance such as a calcium phosphate compound or bioactive glass is applied, and then heat-treated in a vacuum or an inert gas atmosphere.

[0006]

2. Description of the Related Art A composite material in which a coating layer made of apatite or other bioactive substance is formed on the above-mentioned titanium-based metal substrate has excellent biocompatibility and has a characteristic that it is relatively quickly fused with bone. However, there is an inherent problem that the mechanical strength of the metal substrate is significantly deteriorated due to the effects of arc spraying and heat treatment at a high temperature of 1000 ° C. or higher.

[0007] In each case, the thickness of the coating film is several tens μm to
Since it was as large as about 100 μm, there was a problem that the adhesion strength (peeling strength) of the coating film could not be obtained as expected. In addition, it was impossible to coat a deep part in the pores due to the large thickness. Was.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems in the prior art, the present invention relates to a method for forming a coating layer comprising titanium and a calcium phosphate compound on a metal substrate containing titanium as a main component. C. so that the static load strength of the substrate is 900 MPa or more, and the fatigue strength thereof is half or more of the static load strength, and the first peak of the calcium phosphate compound in X-ray diffraction in the coating layer is It should be larger than the first peak of titanium. Then, by reducing the thickness of the coating layer to 10 μm or less, a decrease in adhesion strength is minimized.

That is, according to the present invention, the static load strength is 900 M
The surface of a metal base containing titanium as a main component and having a fatigue strength of not less than half of the static load strength, which is Pa or more, is composed of titanium and a calcium phosphate compound, and titanium is larger than the first peak of the calcium phosphate compound in X-ray diffraction. An object of the present invention is to provide a bioprosthesis member having a coating layer having an average thickness of 10 μm or less exhibiting a first peak.

[0010]

The biological implant material of the present invention has a metal base containing titanium as a main component and a coating layer composed of titanium metal and a bioactive calcium phosphate compound formed on the surface of the metal substrate. And the base and the coating layer contain titanium in common, and in the coating layer, the first peak of the calcium phosphate compound in X-ray diffraction is larger than the first peak of titanium, and the thickness is 10 μm. It is advantageous in terms of the adhesion between the two by making the thickness as thin as possible, and the breaking load of the base is 900 MPa.
As described above, since the fatigue strength is set to be equal to or more than half of the static load strength, it can be safely used in a living body.

[0011]

Embodiments of the present invention will be described below.

In the bioprosthesis member of the present invention, the metal substrate mainly composed of titanium has a static load strength of 900 MPa or more,
And, on the surface of the metal base, the first peak of the calcium phosphate compound is larger than the first peak of titanium, which is composed of titanium and a calcium phosphate compound,
Further, it is characterized in that a coating layer whose thickness is reduced to 10 μm or less is formed.

The metal containing titanium as a main component in the present invention means pure Ti or Ti, Al, V, Zr, Sn, N
An alloy to which b, Ta, Pd, Mo, or the like is added, examples of which include Ti-6Al-4V, Ti-6Al-7Nb, but are not limited thereto.

In the present invention, examples of the calcium phosphate compound include hydroxyapatite, tricalcium phosphate, brushite, OCP and the like, but are not particularly limited thereto.

The bioprosthesis member preferably has a static load strength of 900 MPa or more. When the static load strength is less than 900 MPa, there is a problem that there is a possibility of breaking in a living body. Furthermore, considering long-term use in a living body, it is desirable that not only static load strength but also fatigue strength be large. Specifically, it is desirable to have a fatigue strength of a numerical value of half or more of the static load strength.

In the present invention, these static load strength and fatigue strength are measured based on JIS standards.

The coating layer contains a mixture of titanium and a calcium phosphate compound. However, in order to improve the film quality of the coating layer and to prevent cracks in the layer from occurring, the first peak of the calcium phosphate compound is preferably used. It is important to make it larger than the first peak of titanium. Also,
It is important that the coating layer has an average thickness of 10 μm. This is because the peel strength of the coating layer is increased by controlling the film thickness to this level.

The average thickness of the coating layer is measured by cutting a sample and photographing the cut surface with an SEM image.

In the bioprosthesis member of the present invention having the above-described structure, for example, a paste containing a metal powder containing titanium as a main component and a calcium phosphate compound is applied to the surface of a metal base containing titanium as a main component. Alternatively, it can be obtained by immersing a metal substrate in a slurry containing the metal powder and a calcium phosphate compound, and then performing a heat treatment in a vacuum or an inert gas atmosphere.

In such a production method, the average particle size of these powders is preferably about 0.1 to 3 μm in consideration of sinterability and reactivity between the particles and the substrate. The content of the metal powder is preferably 25% by weight or less and 5% by weight or more. If the content exceeds 25% by weight, there is a problem that the adhesion to bone is reduced, and if it is less than 5% by weight, there is a problem that the coating layer is easily peeled off from the substrate.

With respect to the binder and the solvent for obtaining the paste or slurry in the above-mentioned production method, the binder includes polyvinyl alcohol, polyethylene glycol, ethyl cellulose, polyolefin and the like. In addition, examples of the solvent include organic solvents such as water and alcohol, but are not particularly limited thereto. The metal powder contained in the paste is the same material as that of the base or a powder of titanium hydroxide.

As a method of preparing the paste and applying the paste to the metal substrate, spray coating or the like can be used. On the other hand, the metal substrate is immersed in the slurry. And
Thereafter, a heat treatment is applied to the metal substrate. However, since a metal containing titanium as a main component is easily oxidized and an oxide film to be formed is very brittle, heat treatment is performed in an atmosphere without oxygen. Therefore, before performing this heat treatment, it is necessary to dry the solvent in advance and to calcine the binder.

The heat treatment is preferably performed at a temperature in the range of 500 ° C. to 650 ° C. If the temperature is 650 ° C. or higher, the breaking strength of the metal substrate may be significantly deteriorated.
It is very difficult to obtain a breaking strength of Pa or more. On the other hand, when the temperature is lower than 500 ° C., the coating layer may be easily peeled from the substrate. As described above, the atmosphere for the heat treatment is desirably a vacuum or an inert gas atmosphere.

In addition, regarding the original surface properties of the metal substrate alone, sandblasting has the effect of increasing the strength by surface hardening, but the fatigue strength is reduced by the notch effect. Even if necessary, it is preferable to keep the Rmax within the range of 10 μm or less.

The average film thickness can be controlled to 10 μm or less by appropriately adjusting the binder concentration.

Embodiments Hereinafter, embodiments of the bioprosthesis member of the present invention will be described in detail.

Table 1 shows the samples (No. 1) of the examples of the present invention.
4 to 4) and Comparative Examples (Nos. 5 to 8).

[0028]

[Table 1]

As a metal substrate, 10 × 15 × 0.2 mm
Was prepared using a Ti-6Al-4V alloy having a size of

Further, titanium powder and apatite powder were prepared as powders constituting the coating layer. The titanium powder and the apatite powder had an average particle diameter of 1 μm, 2 μm, and 3 μm for titanium, and the average particle diameter of 1 μm, 2 μm, and 3 μm for apatite was used according to the average film thickness.

Table 1 shows the composition of the powder for forming the coating layer.

The titanium powder and the apatite powder were mixed at the ratios shown in Table 1, and 2.5% by volume of polyisobutyl acrylate and 47.5% by volume of terpineol were added to 100% by volume of the mixed powder. Was prepared.

Next, the metal substrate was immersed in this paste, dried at 150 ° C., and held at 400 ° C. for 30 minutes to degrease the binder. Then, the substrate was placed in a vacuum firing furnace at a temperature shown in Table 1 for 60 hours.
Heat treated for minutes.

For each of these samples, the peel strength of the coating layer, which will be described later, was measured and the adhesiveness to bone was examined. I asked.

As shown in FIG. 1, two metal square bars 12 are bonded to the coating layer 11 located on the opposite surface of the sample 10 with an adhesive, and 12 were pulled in opposite directions, and the force when the coating layer 11 was peeled off was measured.

The adhesion to bone was determined by histologically examining each sample after embedding it in the tibia of a rabbit for 8 weeks, cutting out the material for each bone, embedding it in resin, and slicing it in the cross-sectional direction. And evaluated based on the presence or absence of bone tissue formed on the surface of the material.

In addition, a test piece (No. 1 test piece in a tensile test of Z2241 and No. 1 test piece in a rotary bending test of Z2274) in accordance with the JIS rules for static load strength and fatigue strength was used for Ti-6Al-4V alloy. And a coating layer was formed by the above method. For these, the static load strength and the fatigue strength were measured, and the ratio was determined.

As a result, in Samples 1 to 4, the static load strength of the substrate was 900 MPa or more, the ratio of fatigue strength / static load strength was more than 0.5, and the mechanical strength of the substrate was large. Had a relatively large peel strength of 100 kgf / cm ² or more. In addition, there was no problem in adhesiveness to bone. Note that the peel strength of Sample 6 was less than 100 kgf / cm ² because the processing temperature was low.

On the other hand, in Comparative Examples of Samples 6 to 8, Sample 6 had the peak height ratio of less than 1, and thus had a peel strength of less than 100 kgf / cm ² . Sample 7 had a low mechanical strength with a static load strength of less than 900 MPa. In Sample 8, the thickness of the coating layer was larger than 10 μm, and the peel strength was less than 100 kgf / cm ² .

[0040]

As described above, according to the present invention, a coating layer composed of titanium metal and a bioactive calcium phosphate compound is formed on the surface of a metal substrate containing titanium as a main component. Bonding with bone in a short period of time, and also including titanium commonly in the substrate and the coating layer, and in the coating layer, the first peak of the calcium phosphate compound in X-ray diffraction is larger than the first peak of titanium, By making the thickness as thin as 10 μm or less, it is advantageous in terms of the adhesion between them, and the breaking load of the substrate is reduced to 900 M
By setting the fatigue strength to be Pa or more and half or more of the static load strength, an excellent effect that the bioprosthesis member can be safely used in a living body is exhibited.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method for measuring the peel strength of a coating layer.

[Description of Signs] 10 Sample 11 Coating layer 12 Square rod 13 Adhesive

Claims (1)

[Claims] 1. A titanium-based calcium phosphate compound comprising titanium and a calcium phosphate compound on a surface of a metal base containing titanium as a main component having a static load strength of at least 900 MPa and a fatigue strength of at least half of the static load strength, and the titanium is subjected to X-ray diffraction. A bioprosthetic member comprising a coating layer having an average thickness of 10 μm or less and exhibiting a first peak larger than a first peak of a calcium phosphate compound.