JPS6399868A - Production of composite material coated with calcium phosphate - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

(Prior art and its problems) Biomedical implant materials such as artificial bones and artificial tooth roots can be attached to the remaining bone or implanted into the jawbone in the event of bone loss or tooth loss due to an accident, etc. It has recently been attracting attention because it can be used in a form similar to that of natural substances and allows us to maintain a comfortable life. However, since these implant materials are to be implanted into 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 suitable for living organisms. It must also meet various conditions, such as having compatibility with

Conventionally, metals such as precious metals, alloys such as stainless steel, ceramics such as α-alumina, and apatite ceramics have been used as implant materials.
These materials have at least one of the following disadvantages: toxicity, insufficient strength, lack of processability, leaching, and lack of biocompatibility.

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 metal or ceramic with apatite. For this purpose, metal-ceramic-ceramic-ceramic bonding technology is 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. Through (Special application 1986-
No. 64012, No. 61-64013 and No. 61-70
504) or without intervention (Patent Application No. 16954/1986)
No. 7) We proposed a strongly bonded implant material.

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 bond with the bone tissue including these teeth. A coating of a calcium phosphate compound with good affinity can be assimilated into the bone tissue, eventually leading to direct contact between the bone tissue and the metal substrate. However, since the affinity between the metal base material and the bone tissue is insufficient, degeneration of the bone tissue may occur, which may deteriorate the adhesion resistance of the two, or in the worst case, lead to failure of extraction.

(Objective of the Invention) The object of the present invention is to provide an artificial bone, an artificial tooth root, etc., which have good workability and sufficient mechanical strength, and which have high affinity with bone-Mi fabric and maintain stable adhesion over a long period of time. An object of the present invention is to provide a method for manufacturing a composite material suitable for use as an implant material.

(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 electrolyte solution to form an oxide layer of a single metal base component component or a metal base material as an anode. After forming a mixed oxide layer of the base material component and the metal component in the electrolytic solution and, if necessary, heating the metal base material to stabilize its surface, a coating layer of a calcium phosphate compound is further applied to the surface. The most important feature is that the metal base material and the calcium phosphate compound coating layer have relatively good in-vivo affinity and corrosion resistance. An oxide layer or a mixed oxide layer consisting of a sufficiently large metal oxide is formed by electrolytically oxidizing the metal substrate, so that when the coating layer of the calcium phosphate compound on the surface is absorbed into bone tissue, Another point is to prevent the metal base material and the bone tissue from coming into direct contact 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 of This makes it possible to provide a composite material that can be bonded to bone tissue etc. with a sufficiently large affinity in the living body, maintains stable affinity for a long period of time, and has no adverse effects on the living body.

The metal base materials used in the present invention include titanium, titanium alloys, stainless steel, and chromium-based materials, which are stable in vivo.
A base material selected from cobalt-based alloys, etc. Titanium or titanium alloy here refers to metallic titanium and, for example, T
Stainless steel is selected from titanium alloys with additions of a, Nbs platinum group metals, AI, V, etc., and stainless steel is JIS (Japanese Industrial Standards) SUS304.310 and 316, etc., and cobalt-chromium based alloys. includes corrosion-resistant alloys, including cobalt-chromium alloys, for bioimplantation. Metal substrates made of such metals may be smooth such as a plate or rod, or may have a sponge-like porous surface, or may be an expanded mesh or perforated plate. Good too. These metals are used as base materials because they have sufficiently high mechanical strength and are easy to work with compared to sintered bodies or glass. The uniformity of the oxide layer or mixed oxide layer formed by electrolysis may be improved by removing impurities through cleaning treatment using sonic cleaning, steam cleaning, etc. as well as/
Alternatively, the surface may be roughened by etching treatment to improve affinity with a coating layer of a calcium phosphate compound to be described later, and to activate the surface. 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. The thickness of a thin layer of oxide up to this potential ranges from a few to a few hundred thick, and is effective for the purposes of the present invention, but it is preferable to form a thicker oxide layer, and IA /d11” or more, preferably 5 A/da
By passing a current of +g or more, the immobile [# oxide layer can be destroyed at a high voltage and a thick oxide layer can be formed. The conditions necessary for forming the oxide layer vary depending on the metal substrate and the type of electrolyte, but for example, in an electrolyte containing sodium carbonate, potassium carbonate, calcium carbonate, sodium sulfate, potassium sulfate, calcium sulfate, etc. 40～
An oxide layer of the desired thickness can be obtained by treatment at a voltage of 200 V and a current density of 5 to 200 AIdts for 10 seconds to 2 minutes, accompanied by the generation of sparks in the electrolyte. This phenomenon is sometimes 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 will be formed on the metal base material.For example, using a titanium base material,
When oxidation is carried out in an aqueous chromium sulfate solution with an electrode gap of 30 w1, a current density of 100 A/d can be obtained at a voltage of about 40 V, and chromium with a thickness of 0.1 μm to several tens of μm can be oxidized in 30 seconds to 1 minute. A mixed oxide layer of impregnated titanium oxide is obtained.

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, OH groups that may be incorporated into the oxide layer cannot be separated, 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 It becomes easy to peel off from the material.

When stainless steel or a cobalt-chromium based alloy is used 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 leaches out, making it difficult to obtain an oxide layer.

Further, 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, it is necessary to select an electrolytic solution with a pH of 6 to 13. Although the type of electrolytic solution does not matter, for example, carbonate or sulfate aqueous solutions of various metals, or organic baths containing these as supporting electrolytes are effective, and they can be used in organic baths. Examples of organic compounds 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. Therefore, 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 low rate of oxide layer formation and can withstand heating of 800° C. or higher.

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, WIN of a calcium phosphate compound is formed on the oxide layer of the metal base material on which the oxide layer or mixed oxide layer has been formed in this manner. In the present invention, the term "calcium phosphate compound" mainly refers to hydroxyapatite, and further includes tricalcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate, which are thought to be by-products due to heating and firing of hydroxyapatite in 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 representative 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 30 kW is sufficient, and the grain size of the hydroxyapatite is preferably a medium grain size of about 125 to 345 mesh.

When a thermal decomposition method is employed, a calcium phosphate compound, preferably hydroxyapatite, is dissolved, preferably saturated, for example, in an aqueous nitric acid solution, and applied to the surface of the oxide layer,
A coating layer having strong adhesion to the oxide layer of the metal base material is formed by heating and baking. The heated and calcined product in this case is a calcium phosphate compound mainly composed of hydroxyapatite. The optimal heating and firing conditions vary depending on the liquid used, especially the nitric acid concentration, and the optimal temperature increases as the nitric acid concentration increases.
For 0% nitric acid, 450 to 800°C is optimal. 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.
Peeling is likely to occur between the metal base material and the oxide layer.

The heating and firing may be performed in an oxidizing atmosphere such as air, but is preferably performed in an inert atmosphere such as argon.

In addition to this, a coating layer can be formed by applying a suitable mixture solution of calcium carbonate and calcium phosphate and heating and baking it in an oxidizing or inert atmosphere.
In this case, it is preferable to further perform hydrothermal treatment to improve crystallinity.

Through the above operations, it is possible to obtain an implant material that has good workability, has sufficient mechanical strength, has increased affinity with bone tissue in vivo, and can maintain stable adhesion with the living body for a long period of time. Can be done.

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

JISI type titanium rolled plate with thickness of 1 dragon in spring tide history 0m, width 29
It was cut to a size of 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/d+m'', 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. When the base material was taken out, the surface of the titanium base material was satin-like and covered with a white hard coating.The titanium base material was washed with deionized water, dried, and then examined using an X-ray diffractometer. The white coating on the surface was identified as rutile with low crystallinity (
It turned out to be Ti(h).

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 prepared by dissolving 3 g of hydroxyapatite powder in 10 g of a 25% nitric acid aqueous solution was used, and the coating solution was applied to the base material and heated at 500° C. in an argon gas atmosphere.
Pyrolysis was carried out for 15 minutes. Further, 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.

Forging Team 1 A titanium base material was prepared in the same manner as in Example 1. Using the base material as an anode, electricity was applied using a mixed aqueous solution of 50 g/II cobalt sulfate and 50 g/l sulfuric acid as an electrolyte. Current density is 1
00 A/dll”, sparks were emitted in the liquid,
Part of the titanium base material dissolved and the liquid became cloudy. The voltage at this time was 50V.

When electricity was applied for 1 minute and the titanium base material was taken out, the surface of the titanium base material was found to be satin-like and 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 produced in this manner, elemental analysis was performed using an X-ray microanalyzer, and state analysis was performed using an X-ray diffraction needle. As a result of elemental analysis, it was found that the constituent components were Ti:Co=95:5 (metal mol%). In xi diffraction, C is found in rutile-type titanium oxide (TiO□) 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 base material on which the coating layer was formed was measured by a tape test, and no peeling of the coating was observed.

Ura 挌 ■ 1 IR thickness stainless steel 5US316L plate vertically 4
It was cut out to a size of 0 m by 201 m in width, and the surface was roughened by blasting using #80 steel shot. The 5US316L plate was immersed in a 25% aqueous hydrochloric acid solution at 40° C. for 30 minutes to remove deposits on the surface.

Using the stainless steel base material as an anode, electrolysis was performed at 95° C. in a 0.5 mol % calcium carbonate aqueous solution adjusted to pH 12. When electrolysis was first performed at a current density of 0.5 A/dI112, no oxide formation was observed on the surface, so electrolysis was continued at a current density of IA/dm2. When electrolysis continued for about 30 minutes, the surface of the substrate turned black and the electrolysis voltage increased by 1 inch. When electrolysis was 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 method, it was found that
It was found that the oxide was mainly composed of α-Fez03 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. Using reagent-grade hydroxyapacite powder with a particle size of 125 to 345 mesh as a thermal spraying material, and using plasma gas with an argon:hydrogen ratio of 5:1 (volume ratio), an arc voltage of 60 V and an arc current of 500 A were used to coat the coating to a thickness of approximately 100 μm. A layer was formed. The coating layer was hydroxyapatite containing a small amount of tricalcium phosphate. The coating layer did not peel off at all even in a tape test, and was found to have extremely strong adhesion resistance.

(Effects of the Invention) In the present invention, firstly, the metal base material is titanium, titanium alloy, stainless steel, or chromium-based material, which has particularly corrosion resistance.
A cobalt-based alloy or the like is used, and a metal oxide layer containing the metal components of the metal base material is formed on the surface by electrolytic oxidation, and the composite material according to the present invention is used as an artificial bone or an artificial tooth root. It is harmless to living organisms, stable, and has almost no possibility of elution, and has sufficient mechanical strength and is easy to work with.

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

Thirdly, 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 the 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 Ml to be coated with the calcium phosphate compound and the metal base material, and the coating layer and the 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.

Claims (6)

[Claims] (1) Using a metal base material as an anode, the metal base material is electrolytically oxidized in a conductive electrolyte solution to form an oxide layer of the metal base component alone or a metal base component and the metal component in the electrolyte solution. A calcium phosphate compound-coated composite material comprising forming a mixed oxide layer with a metal substrate, heating the metal base material as necessary to stabilize its surface, and then further forming a coating layer of a calcium phosphate compound on the surface. manufacturing method. (2) A metal base material that is titanium or a titanium alloy is treated with sulfuric acid,
1A/dm in an electrolyte containing sulfate and/or carbonate
2. The manufacturing method according to claim 1, wherein an oxide layer or a mixed oxide layer is formed on the surface of the metal substrate by performing electrolytic treatment at a current density of ^2 or more. (3) A metal base material that is titanium or a titanium alloy is heated at 1 A/d in an electrolytic solution containing cobalt and/or chromium ions.
2. 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 substrate by performing electrolytic treatment at a current density of m^2 or higher. (4) A metal base material made of stainless steel or a chromium-cobalt based alloy is electrolytically treated in an electrolytic solution which is a neutral or weakly alkaline aqueous solution or an organic solution at a current density of 1 A/dm^2 or more, and the above-mentioned The manufacturing method according to claim 1, wherein an oxide layer is formed on the surface of the metal base material. (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 improve the surface of the metal base material. 2. The manufacturing method according to claim 1, wherein a mixed oxide layer containing cobalt and/or chromium is formed on the substrate. (6) Heating the oxide layer or mixed oxide layer in air for 20
The manufacturing method according to any one of claims 1 to 5, wherein the manufacturing method is carried out at a temperature of 0 to 700°C.