JPH0214060B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is useful for implant materials such as artificial bones, teeth, tooth roots, etc., and their bonding materials, and has a surface that is compatible with bone and tooth tissues. The present invention relates to a method for producing a composite material comprising a metal substrate coated with a particularly excellent calcium phosphate compound.

(Prior art and its problems) Biological implant materials such as artificial bone and artificial tooth roots are
When a bone is lost or a tooth falls out due to an accident, etc., it can be attached to the remaining bone or implanted in the jawbone, allowing it to be used in a form similar to that of the original, allowing people to maintain a comfortable lifestyle. Recently, it has been attracting attention because of its However, since these implant materials are to be implanted within the human body, they must be harmless to the human body, and they must also be strong enough, processable, non-eluting, have an appropriate specific gravity, and be compatible with living organisms. It must also meet various conditions such as affinity.

Traditionally, metals such as precious metals, alloys such as stainless steel, ceramics such as α-alumina, and abatite ceramics have been used as implant materials, but these materials are toxic.
Insufficient strength, no workability, elution,
It has at least one of the following drawbacks: lack of compatibility with living organisms.

In order to eliminate these drawbacks, it is desired to develop a biocompatible metal or ceramic material as a composite material by coating the surface of the metal or ceramic with apatite. For this purpose, metal-ceramic and ceramic-ceramic bonding techniques are required, but until now only plasma spraying was known. However, although plasma spraying is useful for such bonding, it has drawbacks such as poor yield of expensive apatite particles and insufficient bonding between the coating and the base material. Furthermore, if the conditions are too severe, a portion of the material will decompose during the thermal spraying process, making it necessary to perform additional processing such as crystallization.

In order to eliminate these conventional drawbacks, the applicant has developed a coating layer consisting of a metal substrate and a calcium phosphate compound, which can be manufactured without using a thermal spraying method, and an intermediate layer containing a calcium phosphate compound. (Patent Application No. 61-64012, No. 61-64013)
We have proposed implant materials that are firmly bonded (Japanese Patent Application No. 61-169547) or without interposition (Japanese Patent Application No. 61-169547).

These implant materials have a sufficiently high bonding strength between the metal base material and the calcium phosphate compound coating layer, but when implanted in a living body, over a long period of time they will become compatible with the bone tissue including the teeth. A coating of highly resistant calcium phosphate compounds can be assimilated into the bone tissue, ultimately resulting in direct contact between the bone tissue and the metal substrate. However, since the affinity between the metal base material and bone tissue is insufficient, degeneration of the bone tissue may occur, worsening the adhesion of the two, or in the worst case, causing the metal base material to fall off.

(Objective of the Invention) The object of the present invention is to provide an artificial bone and an artificial tooth root that have good workability and sufficient mechanical strength, and can also improve affinity with bone tissue and maintain stable adhesion over a long period of time. It is an object of the present invention to provide a method for manufacturing a composite material suitable for implant materials such as the following.

(Means for Solving the Problems) The present invention uses a metal base material as an anode and electrolytically oxidizes the metal base material in a conductive electrolytic solution to form an oxide of a metal base component alone or a metal base. Form a passive thin layer of a mixed oxide of the material component and the metal component in the electrolytic solution, and further oxidize to destroy the passive thin layer to form an oxide or metal of the metal base component alone. After forming a thicker oxide layer of a mixed oxide of the base material component and the metal component in the electrolyte, and optionally heating the metal base material to stabilize its surface, further This is a method for producing a composite material coated with a calcium phosphate compound, which consists of forming a coating layer of a calcium phosphate compound. A relatively thick oxide layer or mixed oxide layer with relatively good corrosion resistance and sufficient corrosion resistance is formed by electrolytically oxidizing the metal substrate, so that the coating layer of calcium phosphate compound on the surface is absorbed into the bone tissue. The purpose of this invention is to prevent the metal base material and the bone tissue from coming into direct contact with each other and deteriorating the adhesion between the two.

The present invention will be explained in more detail below.

The present invention provides a method for electrolyzing a metal base material in an electrolytic solution and applying an oxide layer of the metal base component alone or a metal base component in the electrolyte solution to the surface of the metal base material, which has extremely excellent corrosion resistance in vivo. After forming a mixed oxide layer with a metal component, a calcium phosphate compound coated composite material suitable as an implant material is further formed with a coating layer of a calcium phosphate compound having extremely good affinity with living organisms such as hydroxyapatite on the surface. As a result, it is possible to provide a composite material that can be bonded to bone tissue etc. with a sufficiently large affinity in the living body, can maintain stable affinity for a long period of time, and has no adverse effects on the living body.

The metal base material in the present invention refers to a base material selected from titanium, titanium alloys, stainless steel, chromium-cobalt-based alloys, etc., which are stable in vivo. Titanium or titanium platinum as used herein is selected from metallic titanium and titanium alloys to which Ta, Nb, platinum group metals, Al, V, etc. are added, and stainless steel is
JIS (Japanese Industrial Standards) SUS304, 310, and 316, etc., and cobalt-chromium-based alloys include corrosion-resistant alloys including cobalt-chromium alloys for biological implants. Metal base materials made of such metals may be flat, such as a plate or rod, or may have a porous surface like a sponge, or may be an expanded mesh or perforated plate. Good too. The use of these metals as base materials is
This is because it has sufficient mechanical strength and is easier to work with than sintered bodies or glass, and the surface of the base material has been cleaned in advance by water washing, pickling, ultrasonic cleaning, steam cleaning, etc. The uniformity of the oxide layer or mixed oxide layer formed by electrolysis may be improved by removing impurities, and if necessary, the surface may be roughened by blasting and/or etching treatment to improve the calcium phosphate layer described below. It is also possible to improve the affinity of the compound with the coating layer and to activate it. Note that etching may be performed not only by a chemical method but also by a physical method such as sputtering.

Next, the metal substrate is electrolytically oxidized to form an oxide layer or mixed oxide layer on its surface. In general, titanium or a corrosion-resistant metal alloy such as titanium alloy or stainless steel is used as an anode, and when electricity is applied in a conductive electrolyte, a thin layer of passive oxide is formed on the surface of the anode, the potential increases, and a hyperpassive state occurs, resulting in oxygen occurs. In the present invention, in order to destroy the passive layer and form a thicker oxide layer, a current of 1 A/dm ² or more, preferably 5 A/dm ² or more is applied and further oxidized to form a thick oxide layer. can do. The conditions necessary for forming the oxide layer vary depending on the metal base material and the type of electrolyte, but for example, sodium carbonate, potassium carbonate, calcium carbonate,
For electrolytes containing sodium sulfate, potassium sulfate, calcium sulfate, etc., at a voltage of 40 to 200V, 5
An oxide layer of desired thickness can be obtained by treatment at a current density of ~200 A/dm ² for 10 seconds to 2 minutes. At this time, sparks may be generated in the electrolyte, and this phenomenon is called submerged spark discharge.

When the current is applied, a part of the surface of the metal base material is eluted into the electrolyte solution, and a phenomenon occurs where the surface of the metal base material is deposited again in the form of an oxide on the surface of the metal base material, and if metal ions are present in the electrolyte solution, the ions are taken in at the same time. In this case, a mixed oxide layer of the metal that is a component of the metal base material and the metal in the electrolyte is formed on the metal base material. For example, if a titanium base material is used and oxidized in an aqueous chromium sulfate solution with a gap of 30 mm,
A current density of 100A/ ^dm2 can be obtained at a voltage of approximately 40V,
A mixed oxide layer of chromium-impregnated titanium oxide with a thickness of 0.1 μm to several tens of μm is obtained in 30 seconds to 1 minute.

The oxide layer or mixed oxide layer formed in this way is formed on the entire surface of the metal substrate, but the surface is not uniform and has irregularities, so when forming the coating layer of the calcium phosphate compound described below on it, it is difficult to This effectively increases the contact area and provides strong adhesion. Further, the oxide layer or mixed oxide layer is relatively thick, has low crystallinity, and may partially contain electrolyte components, so it can be stabilized by heating if necessary. Heating is 200-700℃ in air
The heating time can be selected as appropriate, but 10 minutes to 3 hours is appropriate. At temperatures below 200°C, it is not possible to separate the OH groups that may be incorporated into the oxide layer, and at temperatures above 700°C, oxidation of the metal base material itself progresses, and even if the oxide layer is stabilized, the metal base cannot be separated. It becomes easy to peel off from the material.

When using stainless steel styrene or a cobalt-chromium based alloy as the metal base material, care must be taken in selecting the electrolyte, unlike when using titanium or a titanium alloy. That is, when anodic polarization is performed in an acidic solution, the surface of the metal dissolves, making it difficult to obtain an oxide layer. Furthermore, in a strong alkaline solution, the generated oxide on the surface of the metal base material slightly dissolves, so that a sufficiently grown oxide layer may not be obtained. Therefore pH6
It is necessary to select ~13 electrolytes, and the type does not matter, but for example, carbonate or sulfate aqueous solutions of various metals, or organic baths with these as supporting electrolytes are effective, and the organic compounds used in the organic bath as,
Examples include ethyl alcohol, n-butyl alcohol, and isopropyl alcohol.

An oxide layer or mixed oxide layer can be formed in the same way with an electrolytic solution containing halogen ions such as chlorine, but halogen ions may remain in the layer even after heat treatment, making it difficult to use for a long period of time. Stainless steel and cobalt-chromium-based alloys may corrode during this process, which poses problems in terms of stability, so when using these as metal substrates, electrolytes containing halogens should be used. is not desirable.

In addition, stainless steel and cobalt
Chromium-based alloys have a slow oxide layer formation rate;
Can withstand heating over 800℃.

Even when a metal or alloy other than those mentioned above is used as the metal base material, the desired oxide layer can be obtained by appropriately selecting conditions based on the characteristics of the metal.

Next, a coating layer of a calcium phosphate compound is formed on the oxide layer of the metal substrate on which the oxide layer or mixed oxide layer has been formed in this manner. In the present invention, the term "calcium phosphate compound" refers mainly to hydroxyapatite, and also to tricalcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate, which are thought to be by-produced by heating and calcination of hydroxyapatite according to the method of the present invention. In addition, it contains a calcium phosphate compound formed by impurity components or components in the oxide layer or mixed oxide layer and hydroxyapatite.

The method and conditions for forming the coating are not particularly limited, but
Typical methods include plasma spraying and thermal decomposition.

Although the plasma spraying method uses expensive hydroxyapatite as described above and has problems such as insufficient yield, it has the advantage of being able to easily form a coating. However, in the past, when spraying directly onto metal, the spraying had to be carried out under harsh conditions in order to obtain sufficient adhesion, which resulted in the decomposition of some of the expensive hydroxyapatite. However, in the present invention, the base of the coating layer of the calcium phosphate compound is an oxide layer, and even if thermal spraying is performed under conditions where the hydroxyapatite does not decompose, sufficiently strong adhesion can be obtained.

The thermal spraying conditions are, for example, an atmosphere consisting of argon gas and hydrogen, and a power of about 30kW is sufficient.
The particle size of the hydroxyapatite is preferably a medium particle size of about 125 to 345 mesh.

When a thermal decomposition method is adopted, a calcium phosphate compound, preferably hydroxyapatite, is dissolved, preferably saturated, for example, in an aqueous solution of nitric acid, and applied to the surface of the oxide layer, and heated and fired to remove the oxidation of the metal base material. Forms a coating layer that has strong adhesion to the material layer. The heated and calcined product in this case is a calcium phosphate compound mainly composed of hydroxyapatite. The optimal temperature for heating and firing conditions changes depending on the liquid used, especially the nitric acid concentration.The higher the nitric acid concentration, the higher the optimal temperature is.
℃, 450-800℃ is optimal for 60% nitric acid. The heating and firing temperature is preferably 300 to 800°C. If it is less than 300°C, the strength of the calcium phosphate compound coating layer will be insufficient, and if it is higher than 800°C, the oxidation rate of the metal base material will increase, causing the metal base material and the oxide layer to Peeling is likely to occur between the two. The heating and baking may be performed in an oxidizing atmosphere such as air, but is preferably performed in an inert atmosphere such as argon.

In addition, a coating layer can be formed by applying a solution of a mixture of calcium carbonate and calcium phosphate in an appropriate ratio and heating and baking the mixture in an oxidizing or inert atmosphere. In this case, hydrothermal treatment is also required. It is preferable to improve crystallinity.

Through the above operations, an implant material is obtained that has good workability and sufficient mechanical strength, improves its compatibility with the bone tissue in the living body, and maintains stable adhesion with the living body over a long period of time. be able to.

(Examples) The present invention will be explained in more detail with reference to Examples below, but these Examples do not limit the present invention.

Example 1 A rolled titanium plate of JIS type 1 with a thickness of 1 mm was prepared with a length of 40 mm and a width of 40 mm.
It was cut to a size of 20 mm and degreased in trichlorethylene vapor to obtain a metal base material. Electricity was applied using the metal base material as an anode and a 5% potassium carbonate aqueous solution as an electrolyte. When the current density was set to 50 A/dm ² , sparks were emitted in the liquid, part of the titanium base material dissolved, and the liquid became cloudy. The voltage at this time was 70V.
Electricity was applied for 1 minute, and when the titanium base material was taken out, the surface of the titanium base material had a matte finish and was covered with a white hard coating. After washing the titanium base material with deionized water and drying, the white coating on the surface was identified using an X-ray diffraction meter, and it was found to be rutile (TiO ₂ ) with low crystallinity.

A coating layer mainly composed of hydroxyapatite was formed on the surface of the titanium base material on which the oxide layer was formed using a thermal decomposition method. As a coating solution for coating formation, a solution in which 3 g of hydroxyapatite powder was dissolved in 10 g of a 25% nitric acid aqueous solution was used, and the coating solution was applied to the base material and thermally decomposed at 500° C. for 15 minutes in an argon gas atmosphere. . Furthermore, the coating-heating operation was repeated four times. As a result, an extremely strong coating layer consisting essentially of hydroxyapatite was formed on the titanium substrate via the titanium oxide oxide layer.

Example 2 A titanium base material was prepared in the same manner as in Example 1. Using the base material as an anode, 50 g/cobalt sulfate and 50
Electricity was applied using a mixed aqueous solution of g/g of sulfuric acid as an electrolyte. When the current density was set to 100 A/dm ² , sparks were generated in the liquid, part of the titanium base material was dissolved, and the liquid became cloudy. The voltage at this time was 50V. Electricity was applied for 1 minute, and when the titanium base material was taken out, the surface of the titanium base material had a matte finish and was covered with a yellow-green hard coating. The titanium base material was washed with deionized water, dried, and then placed in an electric furnace flowing air at 500° C. and heated for 1 hour. No change in color tone was observed due to this heating. In order to investigate the constituent components and structure of the mixed oxide layer prepared in this way,
Elemental analysis was performed using an X-ray microanalyzer, and state analysis was performed using an X-ray diffractometer. As a result of elemental analysis, it was found that the constituent components were Ti:Co=95:5 (metal molar ratio %). X-ray diffraction shows that Co is present in rutile-type titanium oxide (TiO ₂ ) in the rutile-type crystal phase.
was found to be a solid solution. A coating layer of hydroxyapatite was formed on the titanium base material under the same conditions as in Example 1. The adhesion strength of the titanium substrate on which the coating layer was formed was measured by a tape test, and no peeling of the coating was observed.

Example 3 A stainless steel SUS316L plate with a thickness of 1 mm was cut into a size of 40 mm in length and 20 mm in width, and the surface was #80.
The surface was roughened by plastering using a steel shot. The SUS316L plate was immersed in a 25% aqueous hydrochloric acid solution at 40°C for 30 minutes to remove deposits on the surface.

The stainless steel base material is used as an anode, and the pH is 12.
In a 0.5 mol% calcium carbonate aqueous solution adjusted to
Electrolysis was performed at 95°C. When electrolysis was first carried out at a current density of 0.5 A/dm ² , no oxide formation was observed on ^the surface, so electrolysis was continued at a current density of 1 A/dm ² . When electrolysis continued for about 30 minutes, the surface of the substrate turned black and the electrolysis voltage increased by 1V.
When electrolysis continued for another 60 minutes, the voltage increased by another 2V, and as the voltage began to rise rapidly, electrolysis was stopped. After washing the stainless steel substrate with deionized water, it was placed in an electric furnace at 350° C. and heated for 1 hour. When the surface of the base material was examined by X-ray diffraction, it was found that
It was found that it is an oxide mainly composed of α-Fe ₂ O ₃ with low crystallinity.

Next, a coating layer of a calcium phosphate compound mainly composed of hydroxyapatite was formed on the stainless steel base material by plasma spraying. Particle size 125~345
Metsuyu's reagent-grade hydroxyapatite powder was used as the spraying material, and plasma gas with an argon:hydrogen ratio of 5:1 (volume ratio) was used to produce an arc voltage of 60V and an arc current.
At 500A, a coating layer with a thickness of about 100 μm was formed.
The coating layer was hydroxyapatite containing a small amount of tricalcium phosphate. It was found that the coating layer did not peel off at all even in a tape test, and had extremely strong adhesion.

(Effects of the Invention) In the present invention, particularly corrosion-resistant titanium, titanium alloy, stainless steel, chromium-cobalt-based alloy, etc. are used as the first metal base material, and the surface thereof further contains the metal component of the metal base material. The metal oxide layer is formed by electrolytic oxidation, and when the composite material of the present invention is used as an artificial bone or artificial tooth root, it is harmless to living organisms, stable, and has almost no possibility of elution, and is easy to use mechanically. It has sufficient strength and is easy to work with.

Second, since the surface of the metal base material is coated with a calcium phosphate compound, typified by hydroxyapatite, it has a sufficiently high affinity in vivo that it can be easily bonded to bones, etc. in vivo and has sufficient strength. Can be joined.

Third, as mentioned above, since a metal oxide layer is formed on the surface of the metal base material, the calcium phosphate compound, which has particularly excellent affinity, is absorbed into bone tissue over a long period of time after implantation. Even later, the oxide layer formed on the metal base material prevents direct contact between the bone tissue and the metal base material, which is based on the insufficient affinity between the bone tissue and the metal base material. By preventing deterioration of the adhesion between the two, it is possible to use the calcium phosphate compound-coated composite material of the present invention for a long period of time without causing any change in stability as an implant material.

Fourth, a metal oxide layer is formed between the calcium phosphate compound coating layer and the metal base material, and the coating layer and metal oxide layer have a sufficiently strong bond even when sprayed under relatively mild conditions. Therefore, when forming the coating layer, it becomes possible to use a thermal spraying method which is easy to form a coating but could not be used conventionally due to the decomposition of hydroxyapatite.

Fifth, the metal substrate is subjected to strong electrolytic oxidation to destroy the initially formed passivation layer and form a thicker oxide layer, making the composite produced by the present invention more effective than the conventional case. Corrosion resistance and affinity in vivo are improved.

Claims (1)

[Scope of Claims] 1. Electrolytically oxidize the metal base material in a conductive electrolytic solution using a metal base material as an anode, and form an oxide of the metal base component alone or a metal base component in the electrolyte solution. forming a passive thin layer of mixed oxide with metal components,
Further oxidation is continued to destroy the passive thin layer and form a thicker oxide layer of an oxide of the metal base component alone or a mixed oxide of the metal base component and the metal component in the electrolyte. A method for producing a composite material coated with a calcium phosphate compound, which comprises heating the metal base material to stabilize its surface, if necessary, and then further forming a coating layer of a calcium phosphate compound on the surface. 2. A metal base material that is titanium or a titanium alloy is placed in an electrolytic solution containing sulfuric acid, sulfate, and/or carbonate,
By performing electrolytic treatment at a current density of 1A/dm2 or ^more ,
The manufacturing method according to claim 1, wherein an oxide layer or a mixed oxide layer is formed on the surface of the metal base material. 3 A metal base material that is titanium or a titanium alloy is placed in an electrolytic solution containing cobalt and/or chromium ions.
By performing electrolytic treatment at a current density of 1A/dm2 or ^more ,
The manufacturing method according to claim 1, wherein a mixed oxide layer containing cobalt and/or chromium is formed on the surface of the metal base material. 4. A metal base material made of stainless steel or a chromium-cobalt based alloy is electrolytically treated in an electrolytic solution that is a neutral or weakly alkaline aqueous solution or an organic solution at a current density of 1 A/dm ² or more to obtain the metal base material. The manufacturing method according to claim 1, wherein an oxide layer is formed on the surface. 5 A metal base material that is stainless steel or a chromium-cobalt based alloy is electrolytically treated in an electrolytic solution containing cobalt and/or chromium at a current density of 1 A/dm ² or more to coat the surface of the metal base material with cobalt and The manufacturing method according to claim 1, wherein a mixed oxide layer containing/or chromium is formed. 6 Heating the oxide layer or mixed oxide layer in air
Claim 1: The process is carried out at 200 to 700°C.
The manufacturing method described in section.