JPH0464362A - Surface treatment for material buried in vivo - Google Patents

Abstract

PURPOSE:To achieve higher biological affinity of a base material by electrically energizing a material to be buried in vivo in a bath liquid containing phosphate ions and calcium ions to form a firm apatite film on the surface thereof with a discharge made through an electrolytically generated gas layer. CONSTITUTION:A base material 3 to be treated, namely, a material to be buried in vivo worked as specified is immersed into a bath liquid 2 containing phosphate ions and calcium ions and energized electrically in a large current density through a bath liquid using the material to be treated as electrode to generate a large amount of an electrolytic gas 6. A discharging is caused through the electrolytic gas generated in the liquid to form an apatite as cover on the surface of the base material as generated being decomposed from the bath liquid with the action of heat, impact, an electric field and the like as generated with the discharging.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for surface treatment of artificial bones, artificial tooth roots, etc. to be implanted in living bodies.

[Prior art]

Conventionally, artificial materials such as metals, ceramics, and organic polymer materials have been used as implants.

It is known that when a foreign material is generally implanted into a living body, such as an implant, the tissue surrounding the material causes a certain biological reaction to the foreign material.

If the implant material is relatively similar to living tissue, it will be assimilated and absorbed, but if it is implanted with a harmful metal, the surrounding tissue will quickly try to isolate this foreign material and wrap it in fibrous tissue. Attempts to be quickly excreted from the body.

On the other hand, for intraosseous implant materials, materials with a calcium phosphate type chemical structure such as hydroxyapatite undergo an anabolic absorption effect, whereas alumina type materials bond directly with bone tissue or It is known that they can be bonded through a thin film.

In addition, alternative materials for biological hard tissues such as joints, bones, and tooth roots include:
Characteristics such as static strength, dynamic strength such as fatigue resistance, and elastic modulus that harmonize with the surrounding bone tissue are also required.

From this point of view, conventional metal materials such as Ti and Ti
Alloys, austenitic stainless steel, pitalium, etc. are used.

[Invention or problem to be solved]

As described above, from the viewpoint of mechanical properties, metal materials such as T1 have conventionally been mainly used as implants for biological hard tissue. Although these are usually considered rusty, they are not necessarily rustless if they remain in the body for a long period of time.

Even with these materials, slight corrosion occurs on the surfaces that come into contact with body fluids, which reduces the strength of the material and promotes friction on sliding parts.If corrosion of these metals occurs, metal ions or surrounding living organisms may be generated. There are problems such as transfer to other organizations.

The present invention is proposed to solve the above problems.

[Means to solve the problem]

The above objects of the present invention are achieved by forming an apatite coating layer on the surface of an in-vivo implant.

To form this apatite coating layer, electricity is applied to the substrate to be treated, that is, the in-vivo implant material to be treated, in a bath solution containing phosphate ions and calcium ions, and an electrolytically generated gas layer is formed. This causes discharge to occur through the .

In this specification, the apatite coating layer refers to apatite Ca4(PO4)3 hydroxyapatite Ca,
The main component is Q(PO4)6(0)1)2, and
Caz(PO4)2, CaHPO,, Ca5(PO4
)3(OH), Ca5(PO4)z(OH,C1,F
), CaJvPOa2H20, etc., containing a conjugate of phosphoric acid and calcium.

(Function) The present invention involves immersing a substrate to be treated, that is, an in-vivo implant material that has been subjected to a desired process, in a bath solution containing phosphate ions and calcium ions, and using the material to be treated as an electrode in the bath. By passing electricity through the liquid at a current density to generate a large amount of electrolytic gas, and causing a discharge in the liquid through the electrolytically generated gas, the effects of heat, shock, electric field, etc. generated with the discharge, The surface of the substrate is coated with apatite that is decomposed and produced from the bath liquid.

Therefore, an implant having a strong apatite coating formed on the surface of the material to be treated can be obtained very simply and easily, and the biocompatibility of the substrate can be improved by the apatite coating.

[Best mode for carrying out the invention]

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing an outline of an apparatus for carrying out the method of the present invention, and FIG. 2 is a cross-sectional view showing the mounting state of an implant treated by the method of the present invention.

In FIG. 1, 1 is a processing container in which a bath liquid 2 is stored. 3 is a substrate to be treated immersed in the bath liquid; 4 is an energizing electrode provided at the bottom of the container I to supply electricity to the substrate 3 through the bath liquid 2; 5 is a connection between the substrate 3 to be treated and the electrode 4; A power supply device 6 is an electrolytically generated gas.

Therefore, it is recommended that the surface area of the electrode 30 be made sufficiently larger than that of the substrate 3 to be treated.

Further, as the power source 5, a direct current, a commercial or high frequency alternating current, a pulse power source, etc. are used singly or in combination.

The bath liquid 2 contains equivalent amounts of phosphate ions and calcium ions.

The phosphoric acid component is supplied as a phosphoric acid compound as described below.

(1) Inorganic phosphates Sodium phosphate, calcium phosphate, polymetaphosphoric acid.

(2) Phosphate esters such as dimethyl phosphate, trimethyl phosphate, tributyl phosphate, triethyl phosphate, and alkyl phosphate.

(3) Polynucleotides Oligonucleotides and nucleic acids.

(4) Organic phosphoric acids Cellulose phosphate, starch phosphate, etc.

Furthermore, the following compounds can be used as compounds that supply calcium.

(1) Organic acid calcium salts calcium acetate, calcium butyrate, calcium valerate,
Calcium lactate, calcium glyconate, calcium tartrate, calcium citrate, and calcium adipate.

(2) Chelate calcium complex salts Calcium complex salts of chelates such as ethylenecyaminetetraacetic acid, nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid and others (3) Calcium salts of ionophore calcium salts, cyclopentangenyl, crown ether, cryptant, etc. .

(4) Inorganic calcium compounds such as calcium chloride, calcium phosphate, and calcium oxide.

Further, as the bath liquid, an alcohol/phosphoric acid mixed solution of alkoxide (Ca) containing calcium and phosphoric acid can also be used.

When the substrate 3 to be treated is placed in a bath liquid containing dissolved phosphoric acid and calcium as described above and electricity is applied, a large amount of electrolytic gas 6 such as oxygen, hydrogen, and water vapor is generated around the substrate 3 to be treated due to electrolytic action. The particles are generated, adhere to the substrate 3 of the object to be processed, and come to cover the surface thereof.

Therefore, an equivalent resistance is inserted in series in the current-carrying circuit, and this resistance increases in proportion to the amount of gas generated.

When the electrolytic current density on the surface of the substrate 3 to be processed is increased beyond a certain limit, discharge occurs in the electrolytic gas layer.

That is, as the current increases, the amount of gas generated also increases, which increases in proportion to the resistance value or the amount of gas generated, so the generation of Joule heat is accelerated, and the temperature of the liquid around the substrate 3 to be treated increases rapidly. Due to water vapor and electrolytic gas, electrical discharge occurs in the generated gas area.

If electrical discharge occurs between the bath liquid 2 and the substrate 3 to be treated, the temperature will further rise, and the amount of water vapor and gas generated will increase accordingly, enveloping the substrate 3 to be treated. The resistance increases more rapidly, causing the bath temperature to rise further.

When the temperature of the liquid around the electrode approaches 100° C., the amount of water vapor generated increases, and as a result, the discharge in the mixed gas surrounding the substrate 3 to be treated becomes active, and the temperature rises even more rapidly.

For this reason, the surface of the substrate 3 to be treated can be easily
．． It can be heated to about 000°C.

Apatite can (po4) is formed on the surface of the heated electrode 3 by a chemical reaction between calcium and phosphoric acid in the bath liquid components due to the heating action of this discharge, impact effect, electric field effect, etc.
3 and hydroxyapatite Ca+o(POa)s(
OH)2, Caz(POt)2, CaHPO4
, Ca6(Po4)s(OH), Ca5(PO4)
i(OH, CI, P), Ca2HtPO42H20, and other phosphoric acid-calcium combinations are precipitated to form a dense film.

This produced coating is baked onto the surface of the substrate 3 to be treated as the temperature of the substrate 3 rises, so that a strong apatite coating that adheres to the surface is formed.

This apatite film has a high affinity with living organisms and can be easily obtained as a dense and uniform coating with a thickness of several μm to more than 10 μm, so it is extremely effective as an implant surface coating.

Next, examples will be explained.

[Example 1] A substrate to be treated made of Ti was immersed in a mixed aqueous solution of 5% citric acid and 20% calcium phosphate (supersaturated) by weight, and electricity was applied using this as a negative electrode.

When heat treatment was performed for 5 minutes under discharge conditions of 100 V and IOA, an apatite film of approximately several 10 μm was able to be formed on the surface of the Ti material.

[Example 2] 20% Ca salt of ethylenediaminetetraacetic acid by weight
using a bath solution consisting of 10% sodium phosphate and the balance water.
Electric discharge was performed using the material as a positive electrode.

By applying current for 5 minutes under discharge conditions of 100 V and IOA, an apatite film with a thickness of about 5 μm could be formed.

[Example 3] Discharge was performed using a tributyl phosphate emulsion containing calcium chloride 2096 and using a Ti material as a negative electrode.

The discharge conditions are 100V, 5A, and a thickness of approximately 4 mm after being treated for 5 minutes.
It was possible to form an apatite film of μm.

[Example 4] Using a paste consisting of tributyl phosphate and calcium glyconate, discharge was performed using a Ti material as a negative electrode.

An apatite film with a thickness of about 60 μm could be formed by treatment under discharge conditions of 200 μm, 3 A, and 20 minutes.

[Example 5] An aqueous solution containing 5% citric acid, IO% calcium acetate, and 20% sodium phosphate was used as a bath liquid, and a Ti material was used as a negative electrode.

The discharge conditions were 100V and IOA for 5 minutes to a thickness of approximately 6mm.
An apatite film with a thickness of μm was formed.

[Example 6] Using a mixed aqueous solution of 20% cyclopentadienyl calcium, 20% trimethyl phosphate + 45% Nas PO,
Discharge treatment was performed using a Ti material as a negative electrode.

The discharge conditions were 180V and 5AS was used for 10 minutes to form an apatite film with a thickness of 12μ.

[Example 7] A Ti material was placed in a paste consisting of ATP and CaO, and high frequency discharge with an output of 500 W was performed.

When treated for 20 minutes, an apatite film with a thickness of about 30 μm was formed.

[Experimental Example 8] Using a mixed solution of alkoxide (Ca), alcohol, and phosphoric acid, a Ti material was inserted into the solution, and positive electrode discharge was performed.

The discharge conditions were 30V, 0.5A, 10 minutes of electrophoresis and arc discharge, and 1.5KW.
Baking treatment was performed using microwave discharge at 2450 MHz to form an apatite film with a thickness of 100 μm.

FIG. 2 is a cross-sectional view showing the state of treatment when the method invented in 2010 is applied to a dental implant.

7 is an artificial tooth root formed by processing a metal material such as Ti or a Ti alloy, and 8 is an apatite coating formed on the surface thereof.

The artificial tooth root 7 is inserted and fixed into the jawbone 9 and used as an abutment for the artificial tooth 11 in place of a fallen or extracted tooth.

The apatite coating 8 is mainly formed on the surface of the plate portion of the artificial tooth root 7, that is, the portion that vertically penetrates the dental pulp and is inserted into the jawbone 9 and fixed therein.

This apatite film 8 is desirably formed to have a thickness of about IO μm or less.

The blade surface is completely covered with this apatite thin film 8, and the blade metal does not come into direct contact with living tissue within the jawbone 9.

Furthermore, although the neck of the implant is covered by the gingival mucosa 10, the apatite film blends extremely well with the living tissue, so there is no gap between the implant and the gingiva, and the implant adheres closely to the living tissue. This also reduces the risk of bacteria entering the body and causing infection.

In this way, the implant functions stably and is firmly embedded in the living tissue, so if the crown 11 made of metal or porcelain is firmly fixed to the head of the implant, an extremely stable denture can be created. .

As mentioned above, if submerged discharge is used, an apatite film can be easily generated within a short time, and the film is welded to the surface of the base material by the discharge heat and is baked firmly.
An adhesion strength of about 60 to 70 kg or more can be obtained per unit.

The thickness of the film can also be freely controlled by controlling the treatment time, and an optimum film thickness of several μm to several tens of μm can be easily obtained by several minutes of discharge treatment.

Conventionally, plasma spraying has been the most common method for forming this type of film, but when this method is used, the film is too thick, at 50 μm, and it is difficult to maintain the shape accuracy of the base material. The adhesion was poor and the required adhesion strength could not be obtained.

However, according to the discharge coating method according to the present invention, the thickness of the coating can be controlled by changing the treatment time, and it is particularly easy to control the coating thickness to a suitable thickness of 108 m or less. In addition, this thin film has high adhesion to the base material and high biocompatibility, which increases the strength and safety of implantation into the bone, making it a safe, stable and strong material for a long period of time without side effects. It is possible to embed it.

In the embodiment shown in FIG. 1, the bath liquid 2 in the processing container 1 is stored in a storage tank (not shown), and the discharge treatment is performed while circulating it between the bath liquid 2 and the processing container 1 by a pump. In that case, a liquid temperature control device, an ion concentration control device, etc. are installed in the supply circuit using a pump to control the temperature and composition of the bath liquid, and then the processing liquid is circulated and supplied, so that it is always kept constant. It is recommended that the configuration be configured to perform stable processing under certain conditions.

〔Effect of the invention〕

As described above, since the present invention is constructed as described above, according to the present invention, an apatite thin film with good biocompatibility can be easily formed on the surface of a material, and the thickness of the coating can be controlled. It is easy to form a thin film of about 10 μm or less, which is the best for practical use, and the film is strongly baked onto the base material by the welding and baking effect of discharge heat, so it has extremely high adhesion.

By forming such an apatite film on the surface of a metal base material, a good intraosseous implant with high biocompatibility can be easily obtained.

In other words, bones are made up of fibrous organic matter deposited with minerals such as calcium, phosphoric acid, and carbonic acid, and have unique viscoelastic properties.

The chemical formula and crystal structure of these natural bone minerals have been studied for a long time, and the crystal structure is mainly hydroxylated abatai)Ca. (po, )s (oH) 2
It is known that

Therefore, when an implant coated with apatite is implanted into bone, it undergoes biological assimilation and absorption, and at the same time, the formation of new bone is promoted at the site, allowing the implant to bond firmly with the bone. become.

In addition, by selecting a Ti material as the base metal that harmonizes with the characteristics of the surrounding bone tissue in terms of static strength, dynamic strength such as fatigue resistance, and elastic modulus, we can create excellent artificial bones. can be formed.

Apatite coatings have high adhesion to metal substrates and completely cover the surface of the substrate without forming pinholes, so there is no direct contact between the substrate metal and body fluids, which prevents corrosion. It has the effect of completely preventing deterioration and strength loss.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an outline of an apparatus for carrying out the method of the present invention, and FIG. 2 is a cross-sectional view showing the mounting state of an implant treated by the method of the present invention. ■・・・・・・・・・Processing container 2・・・・・・・Bath liquid 3.7・・・・・・Substrate to be treated 4・・・・・・・Electricity electrode 5・・・・..... Power supply device 6 ..... Electrolytically generated gas 8 ..... Apatite film 9 ..... Jawbone 10 ..... Gums Mucous membrane 11......Tooth crown

Claims (2)

[Claims] (1) An apatite coating layer is formed on the surface of the substrate by applying electricity to the substrate in a bath solution containing phosphate ions and calcium ions and causing discharge between the substrate and the bath solution. 1. A method for surface treatment of an in-vivo implant, characterized by forming a surface. (2) The bath liquid contains sodium phosphate, calcium phosphate, polymetaphosphoric acid and other inorganic phosphates, dimethyl phosphate, trimethyl phosphate, tributyl phosphate, triethyl phosphate, phosphate alkyl esters and other phosphate esters, oligonucleotides, nucleic acids and other polynucleotides. at least one phosphoric acid compound selected from the group consisting of cellulose phosphate, starch phosphate, and other organic phosphoric acids, and calcium acetate, calcium butyrate, calcium valerate,
Calcium lactate, calcium glyconate, calcium tartrate, calcium citrate, calcium adipate and other organic acid calcium salts, ethylenediaminetetraacetic acid, nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid and other calcium complex salts of chelates, cyclopentangenyl, crown The raw material according to claim 1, which is an aqueous solution containing at least one calcium compound selected from the group consisting of ether, cryptant and other ionophore calcium salts, calcium chloride, calcium phosphate, calcium oxide and other inorganic calcium compounds. Surface treatment method for implantable materials.