WO2004103423A1

WO2004103423A1 - Titanium substrate for biocompatible implant coated with hydroxyapatite/titania double layer and a coating method of the same

Info

Publication number: WO2004103423A1
Application number: PCT/KR2003/001488
Authority: WO
Inventors: Hyoun-Ee Kim; Hae-Won Kim; Sung-Min Chung; Ik-Sang Moon; Soon-Jung Hwang; Sun-Do Cho; Koo-Yeol Yoon; In-Ho Kim
Original assignee: Dentium Co., Ltd
Priority date: 2003-05-21
Filing date: 2003-07-24
Publication date: 2004-12-02
Also published as: AU2003250566A1

Abstract

The present invention relates to a method for coating on a biocompatible implant, and in particular to a method for implementing a double layer coating process on a titanium metal substrate for a biocompatible implant having an excellent mechanical property based on an outer layer of a hydroxyapatite(HA) and an inner layer of a titania. A fast osseointegration is implemented through an excellent tissue reaction by a hydroxyapatite in an outer layer, and in an inner layer, a surface of a titanium for a biocompatible implant has an anti-corrosion and anti-abrasion property by a titania in such a manner that a hydroxyapatite/titania double layer is concurrently formed based on a surface coating method among the methods for a surface process of a titanium for a biocompatible implant.

Description

TITANIUM SUBSTRATE FOR BIOCOMPATIBLE

IMPLANT COATED WITH HYDROXYAPATITE/TITANIA

DOUBLE LAYER AND A COATING METHOD OF THE

SAME

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to a titanium substrate for a biocompatible implant coated with a hydroxyapatite/titania double layer and a coating method of the same, and in particular to a method for implementing a double layer coating on a titanium metal substrate for a biocompatible implant having an excellent mechanical property based on a hydroxyapatite(HA) as an outer layer and a titania as an inner layer and relates to a titanium substrate for a biocompatible titanium fabricated by the above method.

Description of Related Art

A human body may corrode a certain metal therein. A biocompatibility implant titanium(Ti) is widely used as a living body material for an implant in a dental field as well as an orthopedic surgery based on its excellent biocompatibility which is nearest an environment of a bone of a human body, an excellent mechanical property, and a no-harm to a human body in a reaction with a living body tissue. Recently, there are many attempts for physically and chemically improving a surface property of the same for enhancing an osseointegration.

A physical characteristic of a surface is changed through a sandblasting or acid etching method or a surface is coated with a certain material having a certain chemical composition different from that of titanium. As a coating material, there may be various materials. Among the above materials, a coating of hydroxyapatite is reported to implement a fast and desired osseointegration when an implant is transplanted into a bone tissue.

In addition, there were some attempts to enhance a biocompatibility in such a manner that a surface of a titanium for a biocompatible implant with a titania(TiO₂). The material of an implant should not have any changes such as a corrosion, a decomposition absorption, etc. in a living body and should have a mechanically enough strength and should endure a chewing pressure.

A pure titanium(purity of 99.5%) which is mainly used as a material of an implant is known to react with a body liquid in a living body for thereby being corroded, so that a certain change may occur in a surface such as a corrosion, decomposition absorption, etc. Generally, an oxide layer is naturally formed on a surface of a titanium in a body liquid for thereby preventing a decomposition of the same in a human body, and an anti- abrasion and anti-corrosion property are enhanced. However, an oxide layer naturally formed on a surface of titanium is too thin to have a desired anti- abrasion and anti-corrosion property. Therefore, there are some attempts for enhancing a resistance with respect to corrosion by artificially forming a titania layer on a surface of a titanium for thereby enhancing a biocompatibility.

As a result of a research, it is known that as a roughness of a surface of an implant is increased, an osseointegration is increased. Therefore, as a means for enhancing a surface roughness, a sandblasting method is generally used. A method for implementing a blasting operation is most widely used using a titania as a medium.

However, since a method of blasting titania does not satisfy a needed surface roughness, a method of using an alumina(AI₂O₃) is developed. However, the method using alumina has an advantage for increasing a surface roughness, but the effects with respect to a human body of an alumina existing in a surface of an implant is not fully known. Therefore, it is not actually in a clinic.

As another method for increasing a surface roughness, a TPS(Titanium Plasma spray) is used. This method is implemented at a very high temperature of 6,000-15,000°C and is impossible to obtain a pure and uniform layer. In addition, it is impossible to increase an adhering strength with respect to a titanium substrate. It is known that there is a negative effect in an osseointegration since the roughness of surface is too high. In addition, there is an acid etching method. However, since this method does not satisfy a required surface roughness based on only an acid etching method, the acid etching method is performed together with a blasting method. However, the above combined method has a complicated process. The thin titanium layer naturally formed on a surface of a titanium is known to increase an adhering strength between a titanium and a hydroxyapatite when a hydroxyapatite is coated on a surface of titanium, but it is too thin, so that it is impossible to implement an enough adhering strength.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a titanium substrate for a biocompatible implant coated with a hydroxyapatite/titania double layer and a coating method of the same, and in particular to provide a method for implementing a double layer coating on a titanium metal substrate for a biocompatible implant having an excellent mechanical property based on a hydroxyapatite(HA) as an outer layer and a titania as an inner layer and relates to a titanium substrate for a biocompatible titanium fabricated by the above method. In the present invention, a hydroxyapatite and a titania are fabricated using a sol gel method for simplifying a coating process and forming a good quality coating layer.

In order to achieve the above objects, there is provided a hydroxyapatite/titania double layer coating method on a titanium substrate for a biocompatible implant, comprising the steps of a step for preparing a hydroxyapatite sol, a step for preparing a titania sol, a step for coating a titania layer on a titanium substrate for a biocompatible implant, a step for heat-treating a titanium substrate for a biocompatible implant coated with a titania, a step for coating a hydroxyapatite layer on a titanium substrate for a biocompatible implant which is coated with a titania and is heat-treated, and a step for heat-treating a titanium for a biocompatible implant coated with a hydroxyapatite.

DETAILED DESCRIPTION OF PREFFERED EMBODIMENTS The preferred embodiments of a titanium surface processing method for a biocompatible implant according to the present invention will be described with reference to the accompanying drawings.

Figure 1 is a flow chart of a coating process according to the present invention. As shown in Figure 2, a system according to the present invention is formed of a double layer formed of an outer layer of a hydroxyapatite and an inner later of a titania on a substrate of a titanium.

Figure 3 is a photo taken by a scanning electron microscope(SEM) for showing a cross section shape of a hydroxyapatite/titania double layer formed on a titanium substrate by a sol gel method according to the present invention. As shown in Figure 2, a double layer structure of a hydroxyapatite outer layer and a titania inner layer is clearly shown. The thickness of each layer is about 800nm in a hydroxyapatite layer and is about 200nm in a titania layer. The hydroxyapatite outer layer and the titania inner layer are very uniform and are formed in a dense micro structure. In addition, it is known to have a very good adhering property since there are not any cracks and exfoliation in the interior of a coating layer and in each interface.

Figure 4 is a graph that a phase of a hydroxyapatite/titania double layer formed on a titanium substrate by a sol gel method is shown by a X-ray diffraction method according to the present invention. As shown therein, since a peak of a hydroxyapatite phase and a peak of a titania phase are clearly shown therein, it is judged that each phase is properly formed.

Figure 5 is a graph that an adhering strength of a hydroapatite/titania double layer and a hydroxyapatite single layer formed on a titanium substrate by a sol gel method are shown based on a heat treatment temperature. As shown therein, at a heat treatment temperature above 450°C, a double layer in which a titania is inserted as an intermediate layer has an adhering strength higher by about 60% compared to a single layer formed of only a hydroxyapatite. In the case that a heat treatment is performed at 500°C, it is known that a strength of a double layer is a highest value of 55Mpa. The above high adhering strength is obtained in such a manner that a titania inserted as an intermediate layer has an excellent chemical compatibility with respect to a titanium as well as a hydroxyapatite.

Figure 6 is a view illustrating a multiplication that a HOS cell was cultivated in a double layer for 5 days and was grown for checking a cell reaction characteristic of a hydroxyapatite/titania double layer formed on a titanium substrate based on a sol gel method according to the present invention. As shown therein, it is known that cells are well grown on a coating layer. Figure 7 is a graph that a HOS cell was cultivated in a hydroxyapatite/titania double layer for seven days and was grown, and the cells were compared with the cells cultivated in a titanium coated with only a pure titanium and titania. As a result, it is known that the number of cells of a titania single coating and a hydroxyapatite/titania double layer is larger compared to that of a pure titanium. Figure 8 is a graph illustrating an ALP(Alkaline Phosphatase) activation degree after the cells were cultivated in a hydroxyapatite/titania double layer for measuring a differentiation degree of cells according to the present invention. The differentiation degree of cells represents an activation of cells and a functional degree of a bone formation as a step after a cell is cultivated among the steps of forming bone. The ALP activation degree is an important index which represents a cell differentiation. It shows a high differentiation ratio by coating using titania compared to a pure titanium. In the case of a double layer coated with a hydroxyapatite thereon, a higher differentiation ratio was obtained. In addition, it was possible to enhance a biocompatibility by coating using a hydroxyapatite/titania double layer on a titanium substrate.

[Examples] The examples of the present invention will be described in detail.

The step for preparing a hydroxyapatite sol includes the steps of a step for preparing a calcium solution in such a manner that Ca(NO₃)₂- 4H₂O which is a material of a calcium is dissolved in an ethanol(C₂H₅OH) and is agitated, a step for preparing a phosphorus solution in such a manner that P(CH₃CH₂O) ₃ which is material of a phosphorus and a distilled water(H₂O) are dissolved in an ethanol(C₂H₅OH), a step for mixing and agitating the calcium solution and the phosphorus solution, and a step for aging the above solution.

A mixture solution of the calcium solution and phosphorus solution are characterized in that calcium and phosphorus are mixed at a mol ratio of 1.67. The mixture solution is aged at a room temperature for 60 hours through 80 hours and then is aged again at a temperature of 35°C through 45°C for 20 hours through 30 hours. <Second example>

The step for preparing a titania sol includes the steps of a step for adding Ti(OCH₂CH₂CH₃) ₂ which is material of a titanium into a solution mixed with an ethanol(C₂H₅OH) and a di-ethanolamine[(HOCH₂CH ) 2NH] and mixing the same, and a step for agitating the mixture solution, adding a distilled water and agitating the same.

The ethanol(C₂H₅OH) and the di-ethanolamine[(HOCH₂CH₂) ₂NH] are mixed at a volume ratio of 5:1 .

The step for coating a titania layer on a titanium substrate includes the steps of a step for wetting a titanium substrate by adding a titania sol to a titanium substrate for a biocompatible implant, a step for implementing a spin coating process using a spin coating unit, a step for drying a titanium substrate coated with a titania sol, and a step for heat-treating the dried titanium substrate.

A spinning process is performed for 10 seconds through 30 seconds at a speed of 3500rpm using a spin coating unit. The drying process is performed for 5 hours through 7 hours at a temperature of 70°C through

90°C.

The step for coating a hydroxyapatite outer later includes a step in which a titanium substrate is wetted by adding a titania sol to a titanium substrate for a biocompatible implant, a step in which a spinning process is performed using a spin coating unit, a step in which the titanium substrate coated with a titania sol is dried, and a step in which the dried titanium substrate is heat-treated. The spinning process is performed using a spinning coating unit at a speed of 3000rpm for 20 seconds. The above drying process is performed for 6 hours at a temperature of 80°C. The above heat treatment is performed for one through two hours at a temperature of 400°C through 600°C.

As described above, in the present invention, it is possible to implement - a high biocompatibility based on a method of coating a hydroxyapatite/titania double layer on a surface of a titanium of a biocompatible implant according to the present invention. In addition, it is possible to increase an adhering strength with respect to a titanium substrate of a hydroxyapatite coating layer by forming a titania intermediate layer between a titanium for a biocompatible implant and a hydroxyapatite. A thin, uniform and dense layer is obtained based on a sol gel method for a coating process. The present invention may be well adapted to an application of a hydroxyapatite coating using other coating methods based on an increase of an adhering strength by inserting a titania intermediate layer. In addition, it is possible to implement a simple process for thereby being economical.

A high demand of a biocompatible implant fabricated according to the present invention is expected, and it is possible to implement a substantial supply based on a mass production.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims

What is claimed is:

1. In a surface processing method of a titanium for a biocompatible implant, a hydroxyapatite/titania double layer coating method on a titanium substrate for a biocompatible implant, comprising the steps of: a step for preparing a hydroxyapatite sol; a step for preparing a titania sol; a step for coating a titania layer on a titanium substrate for a biocompatible implant; a step for heat-treating a titanium substrate for a biocompatible implant coated with a titania; a step for coating a hydroxyapatite layer on a titanium substrate for a biocompatible implant which is coated with a titania and is heat-treated; and a step for heat-treating a titanium for a biocompatible implant coated with a hydroxyapatite.

2. The method of claim 1 , wherein said step for preparing a hydroxyapatite sol includes the steps of: a step for preparing a calcium solution in such a manner that Ca(NO₃) ₂- 4H₂O which is a material of a calcium is dissolved in an ethanol(C₂H₅OH) and is agitated; a step for preparing a phosphorus solution in such a manner that P(CH₃CH₂O) ₃ which is material of a phosphorus and a distilled water(H₂O) are dissolved in an ethanol(C₂H₅OH); a step for mixing and agitating the calcium solution and the phosphorus solution; and a step for aging the above solution.

3. The method of claim 2, wherein a mixture solution of the calcium solution and phosphorus solution are characterized in that calcium and phosphorus are mixed at a mol ratio of 1.67.

4. The method of claim 2, wherein said mixture solution is aged at a room temperature for 60 hours through 80 hours and then is aged again at a temperature of 35°C through 45°C for 20 hours through 30 hours.

5. The method of claim 1 , wherein said step for preparing a titania sol includes the steps of: a step for adding Ti(OCH₂CH₂CH₃) ₂ which is material of a titanium into a solution mixed with an ethanol(C₂H₅OH) and a di- ethanolamine[(HOCH₂CH₂)₂NH] and mixing the same; and a step for agitating the mixture solution, adding a distilled water and agitating the same.

6. The method of claim 5, wherein said ethanol(C₂H₅OH) and said di- ethanolamine[(HOCH₂CH₂)₂NH] are mixed at a volume ratio of 5:1.

7. The method of claim 1 , wherein said step for coating a titania layer on a titanium substrate includes the steps of: a step for wetting a titanium substrate by adding a titania sol to a titanium substrate for a biocompatible implant; a step for implementing a spin coating process using a spin coating unit; a step for drying a titanium substrate coated with a titania sol; and a step for heat-treating the dried titanium substrate.

8. The method of claim 7, wherein a spinning process is performed for 10 seconds through 30 seconds at a speed of 3500rpm using a spin coating unit.

9. The method of claim 7, wherein said drying process is performed for 5 hours through 7 hours at a temperature of 70°C through 90°C.

10. The method of claim 7, wherein said heat treatment is performed for one hour through two hours at a temperature of 400°C through 600°C.

11. The method of claim 1, wherein said step for coating a hydroxyapatite on a titanium substrate which is coated with a titania and is heat-treated is implemented by the same manner as in Claims 7 through 10.

12. A titanium for a biocompatible implant coated with a hydroxyapatite/titania double layer which is fabricated based on the methods of claims 1 through 11.