KR20050011576A - Porous titanium implant - Google Patents

Abstract

PURPOSE: A method for manufacturing porous titanium implant for use in artificial hip joints is provided which utilizes pure titanium having substantially the same Young's modulus with human's bone and has excellent elongating capability without brittle fractures. CONSTITUTION: The method comprises: preparing titanium powder(S10); preliminary sintering the titanium powder(S20); sintering the preliminarily sintered titanium powder at a vacuum furnace by annealing with no pressure applied thereto and annealing with pressures applied thereto (S30); forming the sintered product into an implant having a cubic shape(S40); polishing the implant(S50); and evaluating characteristics of the produced implant by installing a stain gauge(S60).

Description

Porous titanium implant

The present invention relates to a porous titanium implant using pure titanium (Ti), and more specifically, manufactured by pressing and sintering spherical titanium powder having a particle size of 40 to 150 μm and 150 to 250 μm, and having the same Young's modulus as human bones. The present invention relates to a porous titanium implant used for artificial hip joints.

Biomaterials are artificial materials to replace damaged functions in the human body. Especially, in order to be used as functional materials or structural materials, they must be harmless to the human body, have affinity with biological tissues, and do not break in the human body. It must be durable. Biomaterials are manufactured using metals, ceramics, polymers or composite materials prepared by mixing or combining them. Among these materials, metal materials are used for implants requiring strength.

Among the metal materials, pure titanium (Ti) and titanium alloys (Ti alloys) are attracting attention as biomaterials because of their excellent biocompatibility and corrosion resistance as well as their high specific strength. Titanium is a silver-white metal, and pure ones are malleable and ductile, can be annealed by heating, and are important industrially because of their corrosion resistance. There are two types of crystals, α type and β type, and α type is stable at room temperature and belongs to hexagonal system. Above 882 ℃, β type becomes equiaxed crystal system. The strength is about the same as that of carbon steel, and the strength-to-weight ratio is about two times iron and about six times aluminum. Moreover, thermal conductivity and thermal expansion coefficient are small, and the change of strength is small at 400 degrees C or less. It is stable in air, but when heated in oxygen, it becomes titanium oxide. When reacted with halogen, it reacts and is less soluble in iron than iron. In seawater, after platinum, it is strong in corrosion resistance and makes many metals and alloys.

The manufacturing and application technology of pure titanium (Ti) and titanium alloy (Ti) has been developed as a biomaterial since the late '60s since the beginning of the research in advanced countries including the United States and Japan. In addition to spurring the development of applications, active applications and research are underway. Currently, these materials are mainly used as artificial hips and dental implants. Representative pure titanium and titanium alloys, which have been developed or are currently being developed as implant materials, include α-type titanium (grade 2, 3, 4; ASTM), α + β-type Ti-6Al-4V, Ti-6Al-7Nb, Ti-15Sn-4Nb-4Ta-0.2Pd and β-type Ti-15Mo-5Zr-3Al, Ti-15Mo-3Nb, Ti-13Nb-13Zr, Ti-29Nb-13Ta-4.6Zr, and the like. Among them, the most commonly used hip joint is α + β-type Ti-6Al-4V, and as the dental material, α-type pure titanium grades 3 and 4 (Grade 3 and 4) are mainly used.

Artificial hip joint, which is a representative metal implant, is caused by any cause when the hip joint (joint that connects the pelvis and femur (femur) with the hip bone joint and free movement, etc.) is crushed or the cartilage in the joint is worn out. The pelvic socket and femoral head of the affected joint are cut out, replaced with an acetabular cup for the pelvis, and the femur with a femoral stem. The femoral stem is an implant made of pure titanium or titanium alloy is used.In order to insert the implant into the femur during the procedure, a hole is inserted into the femur using a drill, and then the implant is inserted and the femur and the implant are joined with medical cement.

Currently, the manufacturing technology of these implants is limited to melting, casting, and forging technologies. More specifically, the prior art refers to the establishment of a casting technique, that is, the development and post-treatment process of high-density, dense castings, focusing on the establishment of casting technology, that is, melting technology and precision casting process, for practical use of the above materials as implant materials. The focus is on microstructural control and characterization. The high density material obtained by such a process is evaluated to be excellent in product characteristics.

However, when the cast titanium-based material having such a high density is inserted into the bone, a Young's modulus difference between the implant and the bone occurs. The Young's modulus of bone has a value in the range of 10-30GPa according to age and type, but the Young's modulus of high density titanium is 100 ~ 250GPa, which is more than 10 times the Young's modulus. In general, it is known that the hip joint takes three to five times the weight of the human body, and the difference in Young's modulus causes damage to the bone with a small Young's modulus when stress is applied to the implant and the bone simultaneously. That is, a stress-shielding phenomenon in which a large amount of stress is added to a bone having a small Young's modulus occurs, causing mismatch between the implant and the bone, and in this case, many holes are formed in the bone.

Therefore, development of an implant material having a Young's modulus close to human bone is indispensable, and in order to solve these problems, it is focusing on the development of alloys in which the addition and composition of various elements having excellent biocompatibility based on titanium materials are changed. Recently (2002) succeeded in developing Ti-15Mo-5Zr-3Al with high ductility and high strength for artificial hip joints in Japan's Signal Steel Works, but the Young's modulus of these titanium alloys is about 90 GPa. The difference in Young's modulus with the bone is not resolved yet. When the implant is manufactured by the above process, the manufacturing process takes a long time, and it is difficult to satisfy the durability required as a biomaterial due to a large Young's modulus with bone.

Accordingly, an object of the present invention is to solve the problem of the high-density titanium-based implant, a porous implant having a Young's modulus equivalent to human bone by adjusting the porosity, open porosity and pore size of the implant To provide.

It is another object of the present invention to provide a porous implant having excellent stretching properties in which brittle deformation behavior in human bones does not appear.

Another object of the present invention is to develop an implant that is excellent in biocompatibility and capable of cell proliferation, so that bone cells are actively grown to the inside of the porous implant by directly contacting the porous implant with the bone without using medical cement during the procedure. The purpose of the present invention is to provide a porous implant exhibiting an effect of improving the fixed strength according to the increase of the contact interface between the liver.

1 is a manufacturing process flow chart of the present invention.

Figure 2 is a schematic diagram of an implant of the present invention used in the femoral stem of an artificial hip joint. The powder 24 and the pores 22 are shown bonded to each other after sintering the porous implant and the implant inserted into the femur.

3 is a photograph of a porous implant prepared by the present invention. The scanning electron micrograph of the porous implant manufactured by sintering at 1300 degreeC using the powder of 65 micrometers was shown.

Figure 4 is a graph of the fracture behavior of the porous implant produced by the present invention.

Figure 5 is a cell culture photograph of the porous implant prepared by the present invention. It is a fluorescence microscope photograph of the proliferation of cells on the surface of an implant prepared by sintering a powder having an average particle size of 189 µm at 1300 ° C.

※ Explanation of code for main part of drawing

21: porous implant 22: pore 23: femur

24: titanium powder 25: neck

41: Fracture Behavior of Porous Implants Prepared at 900 ° C. Using 65 μm

42: Fracture Behavior of Porous Implants Prepared at 1100 ° C. using 189 μm Powder

51: pore 52: powder 53: root root membrane-derived cells

In order to achieve the above technical problem, in the present invention, a porous implant having a Young's modulus equivalent to bone was manufactured by changing the particle size and sintering condition of the titanium powder. In addition, the implant of the present invention not only has the same Young's modulus as human bone, but also has the characteristics of elastic deformation, plastic yielding and deformation hardening.

The present invention is prepared in a sintering step of charging a spherical titanium powder of 150 ~ 250㎛ in a mold and pressurized at a pressure of 60 ~ 80MPa and then firing and cooling at 1100 ~ 1300 ℃ using a hot press (Hot press), It relates to a porous titanium implant having a Young's modulus of 10-30 GPa, which is the same as that of human bones.

In addition, the present invention is prepared by the sintering step of charging a spherical titanium powder of 40 ~ 150㎛ in a mold and pressurized to a pressure of 60 ~ 80MPa and then calcined and cooled at 900 ~ 1100 ℃ using a hot press (Hot press) device It relates to a porous titanium implant having a Young's modulus of 10 to 30 GPa, which is the same as that of human bones.

The pressurization process is to uniformly disperse the powder in the mold, and if a pressure of less than 60 MPa is applied, the resulting pore distribution is uneven. And, the sintering step is preferably heated at a temperature increase rate of 7 ~ 15 ℃ / min under 1X10 ^-6 torr vacuum.

In addition, the present invention relates to a porous titanium implant for artificial hips, characterized in that the titanium powder is produced by a plasma rotating electrode process or gas atomization. Titanium powder of the present invention uses a pure titanium bulk material, more preferably can be produced using the titanium grade 2 of the α type.

In addition, the present invention relates to a porous titanium implant, characterized in that the porosity of the implant is 32 to 36%. If the porosity of the implant is outside the range of 32 to 36%, the desired Young's modulus cannot be obtained.

Furthermore, the present invention relates to a porous titanium implant, characterized in that the porous titanium implant is capable of cell proliferation in the surface pores and internal pores of the implant. The implants are open pores, that is, three-dimensionally connected, and because the pores are connected to each other in three dimensions without clogging, cells can proliferate not only to the surface of the implant but also to the inside thereof.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the scope of the present invention is not limited only to the description of these examples.

Example 1 Preparation of Porous Titanium Implants

Titanium powder was prepared using titanium grade 2 of α-type titanium powder having an average particle size of 65 μm and an average particle size of 189 μm at 150 to 300 μm by a gas spraying method (step S10 of FIG. 1). ).

The pre-sintering step was carried out by charging the powder into the mold and applying a pressure of 70 MPa for 10 minutes with a press device to uniformly disperse the powder in the mold (step S20 of FIG. 1).

The powder that has undergone the pre-sintering step is subjected to pressure-free heat treatment conditions of 900 ° C., 1100 ° C. and 1300 ° C., and a temperature of 950 ° C., above 882 ° C., in a hot press device capable of uniaxial loading for each average particle size. Sintering was carried out at 5 ° C. and 10 MPa under pressure heat treatment conditions. At this time, the furnace (furnace) was maintained in a vacuum state of 1x10 ^-6 torr and the temperature increase rate up to the target temperature was 10 ℃ / min, holding time 2 hours, cooling was carried out by the furnace cooling method.

Figure 3 is a porous implant prepared by sintering at 1300 ℃ using 65㎛ titanium powder.

Example 2: Characterization of Porous Titanium Implants

In this embodiment, in order to evaluate the characteristics of the porous implant sintered in Example 1, the implant was processed into a cube shape of 9 mm x 9 mm x 25 mm (step S40 of FIG. 1) and polished (step S50 of FIG. 1). When the powder falls out of the porous implant during the polishing step, the density change occurs, so the process should be carried out with caution. Characterization of the polished porous implant was performed by a compression test at room temperature by attaching a strain gage to the implant surface, the results are shown in Table 1 below.

Average particle size (㎛) Sintering Condition Young's modulus (GPa) Porosity (%) Open porosity (%) Pore size (㎛) 189 900 ℃ - 36.4 100 - 1100 ℃ 12.8 33.8 93.0 99.7 1300 ℃ 15.4 33.6 91.2 73.1 950 ° C, 5MPa 74.9 8.70 83.6 43.5 950 ℃, 10MPa 75.8 8.74 83.6 39.1 65 900 ℃ 12.5 34.4 93.2 35.1 1100 ℃ 27.8 32.4 92.7 19.0 1300 ℃ 39.2 28.7 91.6 19.9 950 ° C, 5MPa 85.3 5.1 78.5 11.5 950 ℃, 10MPa 87.6 5.0 73.2 10.1

As shown in Table 1, the porosity of the porous implants prepared under pressureless sintering conditions of 1100 ° C and 1300 ° C was 33.8% and 33.6%, respectively, and their Young's modulus was the same as that of human bone. In addition, the porosity of the porous implants prepared under the pressureless sintering conditions of 900 ° C and 1100 ° C is 34.4% and 32.4%, respectively, and the Young's modulus is the same as that of the bone.

In the case of the implants whose characteristic values are not indicated in Table 1, the powders were separated from the implants during the shape processing and the polishing process under the influence of the low sintering temperature, and thus the characteristic evaluation was impossible. That is, when the porosity of the implant is about 36% or more, it was found that it is impossible to manufacture an implant having a perfect shape. Therefore, it was found that the porous implant having a porosity in the range of 32.4% to 35.6% has the same Young's modulus as the bone.

In addition, a flexural strength test was performed by selecting a porous implant having a Young's modulus equivalent to that of human bone. Respectively, the average particle size of the 189 μm powder was 1100 ° C., and the 65 μm powder was a porous implant prepared by pressureless sintering at 900 ° C., and the results are shown in FIG. 4.

The load-displacement curve of FIG. 4 shows the linear deformation of the straight line with plastic yielding and strain hardening up to peak stress. Although the stress drop decreased after showing the peak stress, it can be seen that it has the advantage of not showing the sudden stress drop that appears in the bone.

Example 3: Cell Culture Experiment

Cell culture experiments were carried out using a porous implant prepared by sintering 374 μm powder and 189 μm powder having the same Young's modulus as bone at 1300 ° C. A porous implant prepared at 1300 ° C. with 374 μm powder and 189 μm powder was immersed in α-MEM medium containing 10% fetal bovine serum (FBS), and the root cell membrane-derived cells obtained from the molar teeth were 3.0 x 10 ^5. Cells / ml were planted on the porous implant surface.

It was confirmed that the cells proliferated to the interior of the porous implant prepared at 1300 ℃ 189㎛ powder (Fig. 5), it was confirmed that the cells proliferate well not only to the surface of the porous implant but also inside.

Therefore, excellent biocompatibility of titanium has been proved from the results of this embodiment, and the effect of improving the fixation strength between the porous implant and the bone cells can be expected without the use of medical cement during the procedure.

As described above, the present invention can provide a porous implant having three-dimensional interconnected pores as the powder particle size and sintering conditions are changed.

In addition, the present invention has the same Young's modulus as human bone and has the advantage of compensating for the shortcomings of brittle fracture behavior in bone due to excellent elongation ability when stress is applied, and at the same time excellent cell culture It is possible to provide a porous implant that can have the ability.

Claims (5)

Spherical titanium powder of 150 ~ 250㎛ is charged into a mold and pre-sintered at a pressure of 60 ~ 80MPa, and then it is manufactured by the sintering step of firing and cooling at 1100 ~ 1300 ℃ using a hot press device. Porous titanium implant, 10-30 GPa, equivalent to human bone. Spherical titanium powder of 40-150㎛ is charged into a mold and pre-sintered at a pressure of 60-80 MPa, and is then manufactured by a sintering step of firing and cooling at 900-1100 ° C. using a hot press device. Porous titanium implant, 10-30 GPa, equivalent to human bone. The porous titanium implant of claim 1 or 2, wherein the titanium powder is produced by a plasma rotating electrode process or a gas atomization method. The porous titanium implant according to claim 1 or 2, wherein the implant has a porosity of 32 to 36%. The porous titanium implant of claim 1 or 2, wherein the porous titanium implant is capable of cell proliferation in surface pores and internal pores of the implant.