JPS6399869A - 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

Traditionally, metals such as precious metals, alloys such as stainless steel, ceramics such as α-alumina, and apatite ceramics have been used as implant materials, but these materials are toxic, have insufficient strength, and are difficult to process. It has at least one of the following disadvantages: lack of properties, elution, and lack of affinity 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 metal or ceramic with apatite. For this purpose, metal-ceramic and ceramic-ceramic bonding techniques are required, but so far only plasma spraying has been 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 (Japanese Patent Application No. 16954
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 develop artificial bones, artificial tooth roots, etc., which have good workability and sufficient mechanical strength, and which have high affinity with bone tissue 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 an implant material.

(Means for Solving the Problems) The present invention heats and oxidizes a metal base material to form an oxide layer of the base material component on the surface thereof, and further provides a coating layer of a calcium phosphate compound on the surface of the oxide layer. This is a method for producing a composite material coated with a calcium phosphate compound, which is characterized by forming a composite material coated with a calcium phosphate compound. An oxide layer consisting of an oxide of the metal constituting the metal base material, which has relatively good corrosion resistance and is sufficiently high, is formed by heating and oxidizing the metal base material, and thereby the calcium phosphate compound coating layer on the surface becomes oxidized. The purpose is to prevent the metal base material from coming into direct contact with the bone tissue and deteriorating the adhesion between them even when absorbed by the tissue.

The present invention will be explained in more detail below.

The present invention heats and oxidizes a metal base material to form an oxide layer of the metal base component on the surface of the metal base material, which has extremely excellent corrosion resistance in vivo, and then further hydrates the surface of the metal base material. A method for producing a calcium phosphate compound-coated composite material suitable as an implant material in which a coating layer of a calcium phosphate compound having extremely good affinity with living organisms such as acid apatite is formed,
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 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 to which a, Nb, platinum group metals, A1, V, etc. are added, and stainless steel is JIS (Japanese Industrial Standard) SUS304.310 and 316, etc., and cobalt-chromium based. Alloys include 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. A cleaning treatment such as sonic cleaning or steam cleaning may be performed to remove impurities and improve the uniformity of the oxide layer formed later.
Furthermore, if necessary, the surface can be roughened by blasting and/or etching treatment to improve affinity with the calcium phosphate compound coating layer described later and to activate it. Note that etching is not limited to chemical methods (it may also be performed by physical methods such as sputtering).

Next, the surface of the metal base material is heated and oxidized to form an oxide layer of the metal component of the metal base material on the surface. When the metal base material is heated as it is in an oxidizing atmosphere such as air to about 400 to 1000°C, an oxide layer is formed with a thickness depending on the type of the metal base material. The thickness of the oxide layer is relatively thin, for example, in the case of a substrate with sufficiently high heat resistance such as titanium or a titanium alloy, stainless steel, or chromium-cobalt-based alloy, in the range of several tens to several hundreds; Although the purpose of the present invention is achieved even with this thickness, it may be preferable to form a thicker oxide layer, and in that case, the following acid treatment or metal hydride formation may be performed as necessary. You can do it.

For acid treatment, the metal substrate may be treated by a coating method, a dipping method, etc. using a solution containing a corrosive inorganic or organic acid such as hydrochloric acid, sulfuric acid, nitric acid, or oxalic acid.
An oxide layer is formed by heating to about 800°C. The nucleic acid treatment corrodes the surface of the metal base material before heating, and the heating effect extends deep into the layer, resulting in the formation of a thicker oxide layer. For example, in the case of titanium or titanium alloys, when heated without acid treatment, a pale yellow oxide is formed, but when heated after acid treatment, a relatively thick blue oxide layer is formed and the oxide is Since the surface remains in a corroded or roughened state even after formation, it becomes possible to form a more strongly coated layer of calcium phosphate compound, which will be described later. Nucleic acid treatment can similarly form thick, stable oxide layers on stainless steel, chromium-cobalt-based alloys, or other metals at lower temperatures.

In addition, when the metal base material is stainless steel or chromium-cobalt based alloy, if an acid containing halogen such as hydrochloric acid is used as the inorganic acid, the halogen may remain in the oxide layer and have an adverse effect. , it is preferable to use sulfuric acid or nitric acid.

The metal hydride on the surface of the metal substrate is usually formed at the same time as the above-described acid treatment of the metal substrate.

400 to 700 in an oxidizing atmosphere such as air.
A corresponding oxide layer is obtained by heating to about °C. The thickness of the metal hydride layer formed by the acid treatment is 0.1
~ reaches several tens of μm. For example, for titanium or titanium alloys, a 10-20 μm thick metal hydride layer can be obtained by treatment in 20-30% boiling hydrochloric acid for 20-40 minutes, and a 4-8 hour treatment in 30% oxalic acid at 100°C. As a result, the unevenness of the surface becomes larger and becomes satin-like.
A metal hydride layer with a thickness of ~20 μm is obtained. The metal hydride is easily oxidized by heating to form a dense oxide layer with similar thickness. Similarly, in the case of stainless steel or chromium-cobalt based alloys, a metal hydride having a thickness of 10 to 20 μm can be obtained by treating the metal hydride in a subcontracting acid at room temperature for 2 to 10 hours.

In order to form the metal hydride, in addition to the acid treatment described above, a method of electrolytically forming the metal hydride by applying current to the metal base material as a cathode can also be adopted. This method is particularly effective for titanium or titanium alloys; for example, when treated in a 15% sulfuric acid aqueous solution at 60° C. for about 5 hours, a metal hydride coating of 0.5 to 10 μm can be formed. When the hydride is titanium or titanium alloy, the temperature is 400 to 700°C.
, other metals can be converted into the corresponding stable oxides by heating to 400-900°C.

Next, a coating layer of a calcium phosphate compound is formed on the oxide layer of the metal base material on which the 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 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 particle size of the hydroxyapatite is preferably a medium particle size of about 125 to 345 Mesosh.

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, the implant has good workability and sufficient mechanical strength, and is also able to maintain stable adhesion with the living body for a long period of time by increasing its affinity with the bone tissue in the living body. material can be obtained.

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

A rolled plate of 5US316L with a thickness of 1 fl on a forked coal was cut into a size of 40 mm in length and 20 mm in width, and its surface was roughened by blasting using #80 steel shot to obtain a metal base material. This metal substrate was degreased with trichlorethylene vapor and then immersed in a 25% by weight aqueous nitric acid solution at room temperature for 30 minutes to remove surface deposits such as blast sand residue.

The stainless steel base material cleaned in this way was
% nitric acid aqueous solution was applied and left at room temperature. After drying, the sample was placed in a 600° C. manifold furnace with air flowing through it, and heated for oxidation for 15 minutes. After repeating this operation three times, the thickness of the blue color was 5 μm.
A stainless steel substrate with an oxide coating layer of about 100 mL was obtained.

This oxide coating layer was found to be extremely strong in tape tests.

Next, a calcium phosphate compound coating layer mainly composed of hydroxyapatite was formed on this oxide coating layer by the following method. The coating layer was formed by adding 3 g of hydroxyapatite powder to 25
% nitric acid aqueous solution Log as a coating liquid,
It was obtained by coating the oxide-coated base material and thermally decomposing it at 500° C. for 10 minutes in a manuffle furnace flushed with argon. Furthermore, the coating-heating operation was repeated three times.

The produced calcium phosphate compound coating layer was substantially composed of hydroxyapatite and was sufficiently firmly attached to the substrate via the oxide layer.

Example 2 A JISI type titanium rolled plate with a thickness of 1.4 mm in length and 2 mm in width.
It was cut out to a size of 0 m and pretreated in the same manner as in Example 2 to obtain a metal base material.

The titanium base material was soaked in a 30% by weight aqueous sulfuric acid solution at 95°C for 15 minutes.
Soaked for minutes. As a result of this immersion, titanium was eluted and hydrogen was violently generated. Take out this titanium base material,
Place it in a Matsufuru furnace maintained at 550°C for 2 hours.
It was held for 0 minutes. Through this operation, a strong blue titanium oxide coating was formed. The titanium base material coated with titanium oxide was coated with hydroxyapatite powder prepared to have a particle size of 125 to 345 mesh by plasma spraying.

The conditions for the plasma spraying method are plasma gas Ar:Hz =
5:1 (volume), arc voltage 60V, and arc current 500A. This thermal spraying made it possible to form a strong coating of hydroxyapatite containing tricalcium phosphate.

Example 3 A JISI type titanium rolled plate having a thickness of 1 inch was pretreated in the same manner as in Example 1, and was used as a metal base material. Using the titanium base material as a cathode, 100 A/
Electrolysis was carried out for 30 minutes at a current density of 500 dm". As a result of this operation, the surface of the titanium base material became grayish white. When this was examined by X-ray diffraction, it was found that TiHz was generated on the surface. .

The titanium substrate was heated at 450° C. for 30 minutes in a Matsufuru furnace through which a gas mixture consisting of 25% oxygen and 75% nitrogen was passed. The surface became yellowish brown, and X-ray diffraction revealed that a rutile-type oxide was formed on the surface.

Example 1
A hydroxyapatite layer was formed under the same conditions.

The hydroxyapatite layer was extremely strong, and no peeling was observed in the tape test.

(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 heating and oxidizing the metal base material. When used as a 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, 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 with sufficient strength. be able to.

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 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.

Claims (4)

[Claims] (1) A metal base material is heated and oxidized to form an oxide layer of the base material component on the surface thereof, and a coating layer of a calcium phosphate compound is further formed on the surface of the oxide layer. A method for producing a calcium phosphate compound coated composite. (2) The manufacturing method according to claim 1, wherein the surface of the metal base material is previously treated with an acid to convert the surface of the metal base material into a metal hydride, and then the surface is heated and oxidized. (3) The manufacturing method according to claim 1, wherein the metal base material is previously energized as a cathode in an electrolytic bath to convert the surface of the metal base material into a metal hydride, and then the surface is heated and oxidized. . (4) The production according to any one of claims 1 to 3, wherein the metal base material is a corrosion-resistant metal or alloy selected from titanium or titanium alloy, stainless steel, and cobalt-chromium-based alloy. Method.