IMPLANT AND MANUFACTURING METHOD THEREFOR

Abstract

Provided is an implant including a base material composed of magnesium or a magnesium alloy and an anodized membrane formed on a surface of the base material. The anodized membrane has 8,000 to 250,000 pores with an average diameter of 0.1 m to 1 m within 1 mm.sup.2.

Claims

1. An implant comprising: a base material composed of magnesium or a magnesium alloy; and an anodized membrane formed on a surface of the base material, wherein the anodized membrane has 8,000 to 250,000 pores with an average diameter of 0.1 m to 1 m within 1 mm.sup.2.

2. The implant according to claim 1, wherein the anodized membrane has 8,000 to 62,000 pores with an average diameter of 0.5 m to 1 m within 1 mm.sup.2.

3. The implant according to claim 1, wherein the anodized membrane has 62,000 to 250,000 pores with an average diameter of 0.1 m to 0.5 m within 1 mm.sup.2.

4. The implant according to claim 1, wherein the anodized membrane has pores each having a diameter of 10 m or larger.

5. The implant according to claim 1, wherein the anodized membrane contains 20% to 30% by weight of magnesium element, 40% to 50% by weight of oxygen element, and 10% to 30% by weight of phosphorus element and is formed by performing an anodizing process in an electrolytic solution having a phosphoric acid concentration of 0.1 mol/L or smaller.

6. A method for manufacturing an implant, comprising: performing an anodizing process involving immersing a base material composed of magnesium or a magnesium alloy in an electrolytic solution with a pH value ranging between 9 and 13 and containing 0.1 mol/L or smaller of phosphoric acid and 0.2 mol/L of ammonia or ammonium ions but not containing elemental fluorine and applying electricity to the base material, so as to form an anodized membrane having 8,000 to 250,000 pores of 0.1 m to 1 m within 1 mm.sup.2 on a surface of the base material.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0010] FIG. 1 is a partial vertical sectional view illustrating an implant according to an embodiment of the present invention.

[0011] FIG. 2 illustrates an electron-microscope image showing a first example of the implant in FIG. 1.

[0012] FIG. 3 illustrates an electron-microscope image showing a second example of the implant in FIG. 1.

[0013] FIG. 4 includes a microscope image (a) showing a state where the implant in FIG. 3 is implanted within a biological organism and an enlarged image (b) of (a).

[0014] FIG. 5 illustrates an electron-microscope image showing a third example of the implant in FIG. 1.

DESCRIPTION OF EMBODIMENTS

[0015] An implant and a manufacturing method therefor according to an embodiment of the present invention will be described below with reference to the drawings.

[0016] As shown in FIG. 1, an implant 1 according to this embodiment includes an anodized membrane 3 on the surface of a base material 2 composed of magnesium or a magnesium alloy.

[0017] The base material 2 may be composed of any material having magnesium as a main component and may be composed of metal containing magnesium alone or may be composed of a magnesium alloy. In order to give the base material 2, for example, moldability, mechanical strength, and ductility, a magnesium alloy is used. Examples of the magnesium alloy include a MgAl alloy, a MgAlZn alloy, a MgAlMn alloy, a MgZnZr alloy, a Mg-rare-earth-element alloy, and a MgZn-rare-earth-element alloy.

[0018] The anodized membrane 3 has 8,000 to 250,000 pores with an average diameter of 0.1 m to 1 m within 1 mm.sup.2.

[0019] A method for manufacturing the implant 1 according to this embodiment having the above-described configuration is as follows.

[0020] Specifically, the implant 1 according to this embodiment is manufactured by performing an anodizing process involving immersing the base material in an electrolytic solution with a pH value ranging between 9 and 13 and containing 0.1 mol/L or smaller of phosphoric acid and 0.2 mol/L of ammonia or ammonium ions but not containing elemental fluorine, and applying electricity to the base material.

[0021] The anodizing process is performed by connecting a power source between the base material 2 immersed in the electrolytic solution and serving as an anode and a cathode material similarly immersed in the electrolytic solution.

[0022] Although the power source used is not limited in particular and may be a direct-current power source or an alternating-current power source, a direct-current power source is preferred.

[0023] In the case where a direct-current power source is used, it is preferable that a constant-current power source be used. The cathode material used is not limited in particular. For example, stainless steel may be suitably used. The surface area of the cathode is preferably larger than the surface area of the magnesium alloy to be anodized.

[0024] The electric current density at the surface of the base material 2 serving as an anode when a constant-current power source is used as the power source is 20 A/dm.sup.2 or higher. The electricity application time is between 10 seconds and 1000 seconds. When electricity is to be applied by using a constant-current power source, the applied voltage is low at the start of the electricity application process but increases as time elapses. The final applied voltage when the electricity application process ends is 350 V or higher.

[0025] In the implant 1 manufactured in this manner, the anodized membrane 3 at the surface thereof has 8,000 to 250,000 pores with an average diameter of 0.1 m to 1 m within 1 mm.sup.2.

[0026] Pores of 1 m in size have an effect of maintaining fibrin fibers at the surface of the implant 1, and pores on the order of 0.1 m have an effect of increasing the adhesive force of cells, bone-active substances from osteoblastic cells, and the deposition amount of calcium. Therefore, the implant 1 according to this embodiment can enhance the osteo-integration performance.

[0027] Then, after direct fusion between the bone tissue and the implant 1 caused by osteo-integration, the base material 2 is biodegraded. Consequently, the implant 1 does not remain as a foreign object within a biological organism over a long period of time, thus eliminating the need for performing a removal process.

Examples

First Example

[0028] Next, a first example of an implant 1 according to an embodiment of the present invention will be described.

[0029] In the implant 1 according to this example, the anodized membrane 3 formed on the surface of the base material 2 composed of a magnesium alloy has 56,000 pores with an average diameter of 1 m within 1 mm.sup.2.

[0030] The base material 2 is immersed in an electrolytic solution with 0.05 mol/L of phosphoric acid. By using a constant-current power source with an electric current density of 20 A/dm.sup.2 at the anode surface as a power source, electricity is applied for 60 seconds. The final applied voltage when the electricity application process ends is 400 V.

[0031] An electron-microscope image of the anodized membrane 3 at the surface of the implant 1 manufactured in this manner is shown in FIG. 2. According to this, every 1 mm.sup.2 region has 56,000 pores with a diameter of 0.4 m to 5 m and an average diameter of 1 m.

[0032] According to this example, the anodized membrane 3 at the surface of the implant 1 can maintain the fibrin fibers at the surface of the implant 1 by means of the pores with the average diameter of 1 m.

[0033] The components of the anodized membrane 3 are as shown in Table 1 below.

TABLE-US-00001 TABLE 1 Element Mass Concentration(%) CK 3.58 OK 48.08 MgK 23.83 PK 21.58 PtM 2.93 Total 100.00

Second Example

[0034] Next, a second example of an implant 1 according to an embodiment of the present invention will be described.

[0035] In the implant 1 according to this example, the anodized membrane 3 formed on the surface of the base material 2 composed of a magnesium alloy has 62,000 pores with an average diameter of 0.5 m within 1 mm.sup.2.

[0036] The base material 2 is immersed in an electrolytic solution with 0.1 mol/L of phosphoric acid. By using a constant-current power source with an electric current density of 30 A/dm.sup.2 at the anode surface as a power source, electricity is applied for 60 seconds. The final applied voltage when the electricity application process ends is 350 V.

[0037] An electron-microscope image of the anodized membrane 3 at the surface of the implant 1 manufactured in this manner is shown in FIG. 3. According to this, every 1 mm.sup.2 region has 62,000 pores with a diameter of 0.2 m to 1.2 m and an average diameter of 0.5 m. Furthermore, pores (protrusions and recesses) that are about 10 m, which are considered to be processing marks, are formed over the entire surface of the implant 1.

[0038] According to this example, the anodized membrane 3 at the surface of the implant 1 can maintain the fibrin fibers at the surface of the implant 1 by means of the pores with the average diameter of 0.5 m.

[0039] The components of the anodized membrane 3 are as shown in Table 2 below.

TABLE-US-00002 TABLE 2 Element Mass Concentration (%) CK 3.73 OK 46.97 MgK 23.84 PK 21.51 PtM 3.95 Total 100.00

[0040] The implant 1 manufactured in this manner implanted in a bone of a rat, and a microscope image obtained after three months is shown in FIG. 4. The white circle at the center of FIG. 4(a) corresponds to the implant 1 according to this example. According to FIG. 4(a) and FIG. 4(b), which is an enlarged view thereof, it can be confirmed that the cells adhere to each other so that a magnesium oxide or magnesium phosphate elutes around the implant 1 and that bone formation starts therearound.

Third Example

[0041] Next, a third example of an implant 1 according to an embodiment of the present invention will be described.

[0042] In the implant 1 according to this example, the anodized membrane 3 formed on the surface of the base material 2 composed of a magnesium alloy has 248,520 pores with an average diameter of 100 nm within 1 mm.sup.2.

[0043] The base material 2 is immersed in an electrolytic solution with 0.05 mol/L of phosphoric acid. By using a constant-current power source with an electric current density of 30 A/dm.sup.2 at the anode surface as a power source, electricity is applied for 60 seconds. The final applied voltage when the electricity application process ends is 350 V.

[0044] An electron-microscope image of the anodized membrane 3 at the surface of the implant 1 manufactured in this manner is shown in FIG. 5. According to this, every 1 mm.sup.2 region has 248,520 pores with a diameter of 50 nm to 200 nm and an average diameter of 100 nm.

[0045] According to this example, the anodized membrane 3 at the surface of the implant 1 can maintain the fibrin fibers at the surface of the implant 1 by means of the pores with the average diameter of 100 nm, and the adhesive force of cells, bone-active substances from osteoblastic cells, and the deposition amount of calcium can be increased.

[0046] The components of the anodized membrane 3 are as shown in Table 3 below.

TABLE-US-00003 TABLE 3 Element Mass Concentration (%) OK 45.74 MgK 24.36 PK 22.16 Others 3.56 Total 100.00

[0047] The above-described embodiment leads to the following inventions.

[0048] An aspect of the present invention provides an implant including a base material composed of magnesium or a magnesium alloy and an anodized membrane formed on a surface of the base material. The anodized membrane has 8,000 to 250,000 pores with an average diameter of 0.1 m to 1 m within 1 mm.sup.2.

[0049] According to this aspect, pores of 1 m in size formed in the anodized membrane have an effect of maintaining fibrin fibers at the surface, and pores on the order of 0.1 m can increase the adhesive force of cells, bone-active substances from osteoblastic cells, and the deposition amount of calcium, thereby enhancing the osteo-integration performance.

[0050] In the above aspect, the anodized membrane may have 8,000 to 62,000 pores with an average diameter of 0.5 m to 1 m within 1 mm.sup.2.

[0051] Accordingly, since there are a small number of pores on the order of 0.1 m, the adhesive force of cells is weakened, thereby allowing for improved removability when a problem occurs.

[0052] Furthermore, in the above aspect, the anodized membrane may have 62,000 to 250,000 pores with an average diameter of 0.1 m to 0.5 m within 1 mm.sup.2.

[0053] Accordingly, the adhesive force of cells, bone-active substances from osteoblastic cells, and the deposition amount of calcium can be increased, so that the osteo-integration performance can be sufficiently enhanced even for a patient with poor bone formation.

[0054] Furthermore, in the above aspect, the anodized membrane may have pores each having a diameter of 10 m or larger.

[0055] Accordingly, with the pores that are 10 m or larger, the contact area with the bone tissue is increased, so that a large number of osteoblastic cells are accumulated, thereby increasing the deposition amount of calcium.

[0056] Furthermore, in the above aspect, the anodized membrane may contain 20% to 30% by weight of magnesium element, 40% to 50% by weight of oxygen element, and 10% to 30% by weight of phosphorus element and may be formed by performing an anodizing process in an electrolytic solution having a phosphoric acid concentration of 0.1 mol/L or smaller.

[0057] Accordingly, the anodized membrane is biodegraded within the body, the fibrin fibers are maintained, and the adhesive force of cells, bone-active substances from osteoblastic cells, and the deposition amount of calcium can be increased.

[0058] Another aspect of the present invention provides a method for manufacturing an implant. The method includes performing an anodizing process involving immersing a base material composed of magnesium or a magnesium alloy in an electrolytic solution with a pH value ranging between 9 and 13 and containing 0.1 mol/L or smaller of phosphoric acid and 0.2 mol/L of ammonia or ammonium ions but not containing elemental fluorine and applying electricity to the base material, so as to form an anodized membrane having 8,000 to 250,000 pores of 0.1 m to 1 m within 1 mm.sup.2 on a surface of the base material.

REFERENCE SIGNS LIST

[0059] 1 implant [0060] 2 base material [0061] 3 anodized membrane