KR20040011885A - Bioactive Ceramics, Metallic Replacement Coated With Bioactive Ceramics And Method Thereof - Google Patents

Abstract

PURPOSE: Provided are a bio-active ceramics and a metallic implant used in surgical and dental applications coated with the ceramics in order to increase bio-affinity to a subject having the implant. CONSTITUTION: The bio-active ceramics comprises 40-49 wt.% of CaO, 40-49 wt.% of silica(SiO2) and 2-20 wt.% of B2O3. The process for producing the metallic implant comprises steps of preparing the bio-active ceramic by fusing raw material consisting of CaO, SiO2, B2O3 and quenching the fused material; grinding the frozen material into powders having less than 10 micrometer size; preparing slurry by adding aqueous or organic solvents and a binder; applying the slurry to a metallic implant by means of brush; and sintering the coated implant at 700-950 deg.C.

Description

Bioactive Ceramics and Metallic Implants Coated with Bioactive Ceramics and a Method for Manufacturing Them {Bioactive Ceramics, Metallic Replacement Coated With Bioactive Ceramics And Method Thereof}

The present invention relates to a metal implant coated with bioactive ceramics and bioactive ceramics and a method of manufacturing the same, and more particularly to coating bioactive ceramics in order to increase biocompatibility of metal grafts used in the surgical and dental fields. A bioactive ceramic coated metal implant and a method of manufacturing the same.

Currently used artificial joints or implants for fixation inside and outside the body use stainless steel, titanium or tartan alloys, and cobalt-chromium alloys with excellent mechanical strength. These materials have been applied to implants that must withstand mechanical stress because of their excellent mechanical strength with a tensile strength of 400 to 900 MPa and a fatigue strength of 200 to 900 MPa.

However, these metal grafts do not have biocompatibility, so they do not bind to surrounding bone tissues and gradually fall out or destroy bone tissues.

Bioactive ceramics, on the other hand, are materials that bind directly to bone, but are significantly less powerful than metals, and therefore cannot be used as artificial joints or internal and external fixators.

However, when bioactive ceramics are coated on the surface of a metal implant, the bioactive ceramic coating layer is an ideal implant because the bioactive ceramic coating layer directly bonds with surrounding bone tissue and the metal body serves to withstand mechanical stress.

Bioactive ceramics for coating have mainly used synthetic apatite (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ), similar to bone components. As a coating method, the plasma spraying method was most frequently used. This is a method in which apatite powder is melted in a high temperature plasma region of 20,000 to 30,000 degrees and then fused to a metal target. US Patent Publication No. 5730598 provides an apatite implant coated by plasma spraying. However, the coating layer coated by the plasma spray method is higher than the coating layer coated by the chemical vapor deposition method, sputtering method, etc., but there is still a problem that the destruction of the coating layer occurs on the metal surface and the surface of the coating layer. In recent years, metal implants are deposited in a solution containing calcium and phosphate ions to precipitate apatite on the metal surface or to modify the surface to deposit a simulated body fluid (SBF) to form a layer of apatite on the surface. In addition, methods for coating apatite fine particles using electrophoresis have been developed. U.S. Pat.Nos. 6069295, 6139585, 6146686, 6153266, 6207218, 6221111, and 6280789 disclose metal grafts deposited on a solution containing calcium salt, phosphate, and the like. It provides a method of coating by allowing the apatite to precipitate in.

US Patent Publication Nos. 5855612, 6129928, and Korean Laid-Open Patent Publication No. 2001-018331 provide a method of alkali-treating titanium implant surfaces by depositing them in pseudo-body fluids to form apatite carbonate layers on the surfaces. U.S. Patent Nos. 307326, 5205921, and 5723038 provide methods for coating apatite fine particles on a lass substrate by electrophoresis.

In addition to apatite, there is also a method of coating bioactive glass. Glass is advantageous because its bioactivity is superior to apatite. Methods of coating the bioactive glass include enamelling, flame-spray, rapid-immersion coating, and the like. The enameling method is the most commonly used glass coating method. A glass powder is mixed with a solvent to make a slurry, and then it is coated by brushing, spraying, or immersing it, drying it, and then heat-treating it to heat the glass. It is chemically bonded to the oxide layer of the fused between the glass powder to form a dense coating layer. Frame spray is a method in which glass powder is poured into a 3000 degree flame, melted, and then fused onto a metal substrate. The steep coating method is a glass coating method in which a metal oxide layer is melted into a glass by thermally treating a metal substrate to form a metal oxide layer on a surface thereof, and then immediately depositing the same in a glass melt, and then chemically bonding the metal oxide layer into glass. US Patent Publication No. 5480438 provides a metal implant coated with bioactive glass composed of Al ₂ O ₃ , Ca _O , TiO ₂ , SiO ₂ , and the like. However, the conventional commercial bioactive glass has a problem that the coating on the metal substrate dissolves too quickly and disappears before bonding to the bone tissue. Ideally, the bioactive ceramic coating should have excellent bioactivity for fast bonding with bone, and its dissolution rate is similar to that of bone growth, so that it slowly dissolves during bone growth and finally reaches the surface of the metal implant. Required.

Known or commercially available bioactive ceramic coated metal implants often have weak adhesion strengths that dissolve too quickly before they separate between the metal and ceramic coating layers or grow bone around them, which is often beyond the purpose of the coating. In addition, coating equipment is expensive and the process is complicated.

Accordingly, the present invention has been made to overcome the problems of the prior art, a bioactive ceramic and a metal active body coated with a bioactive ceramic having a superior bioactivity and excellent bone bonding strength and a suitable dissolution rate and a method of manufacturing the same. The purpose is to provide.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph illustrating the sintering characteristics of ceramics in which apatite and wollastonite are combined to explain the present invention.

2a to 2f are electron micrographs of the surface of each specimen 1 day after the deposition of pseudo fluids.

Microstructure SEM photograph of the specimen sintered at 1300 ° C. for 2 hours in FIGS. 3A to 3E.

Figure 4 is an optical micrograph of the tissue near the implant taken 8 weeks after implanting the titanium alloy cortical screw coated with bioactive crystallized glass in dogs.

Figure 5 is an optical micrograph of the tissue near the implant taken after 8 weeks after implanting the uncoated titanium alloy cortical screw in dogs.

In order to achieve the above object, the present invention is that in the molar ratio of calcium oxide (CaO) is 40 to 49%, silica (SiO ₂ ) is 40 to 49%, B ₂ O ₃ is composed in the range of 2 to 20% It provides a bioactive ceramic characterized in that.

In addition, the present invention provides a metal implant obtained by coating a powder of a bioactive ceramic composed of CaO, SiO ₂ , B ₂ O ₃ by enamel coating and firing treatment, the present invention is CaO, SiO ₂ , B ₂ O ₃ Melting and quenching the formed raw powder to produce a bioactive ceramic; Pulverizing the bioactive ceramic to produce a powder of 10 μm or less; Preparing a coating slurry by adding an aqueous or organic solvent and a binder to the powder; Coating the coating slurry on the metal implant by means of a brush, spray, deposition, or the like; It provides a method for producing a metal implant coated with a bioactive ceramic, characterized in that it comprises the step of sintering at a temperature of 700 ~ 950 ℃.

The bioactive ceramics each have a composition containing 40 to 49% of calcium oxide (CaO) in a molar ratio, 40 to 49% of silica, and ₂ to 20% of B ₂ O ₃ , and crystallized by heat treatment to improve biosolubility. Let's do it.

The bioactive ceramic having the above composition is a crystallized glass and is composed of β-type wollastonite (CaSiO ₃ ), calcium borate (CaB ₂ O ₄ ), and borosilicate glass.

In addition, in the composition range, B ₂ O ₃ has a problem of dissolving too quickly if it contains more than 20% by playing a role of controlling the bio solubility, and less than 2% is less than the amount of B ₂ O ₃ is less than 2% Not much If CaO and SiO ₂ are 40% or less, respectively, the amount of B ₂ O ₃ is too high, which causes a problem of rapid dissolution. At 49% or more, glass cannot be manufactured because crystallization is easy during melting of raw materials. Compositions other than this composition range do not become glass or have no bioactivity, and crystallized glass of this composition range contains calcium borate and borosilicate that are well soluble in water, and β-type wollastonite, the main phase, is also gradually dissolved in water. It is a feature that disappears completely after a certain period of time.

Therefore, when the bioactive ceramic having the composition described above is used as a coating layer, the bone growth rate and the dissolution rate are similar, so that bone tissue grows well around the implant, and thus is more fixed than the uncoated implant. .

In addition, the bioactive ceramics having this composition are sintered at a low temperature between 730 and 820 ° C., so that the reduction in adhesion strength due to the thickening of the metal surface oxide layer and the decrease in mechanical strength due to the increase in heat treatment temperature are less likely. In addition, calcium borate in the component is easily dissolved in body fluids to increase the supersaturation of calcium, and the borosilicate glass phase forms a silazane (Si-OH) group that serves to provide a nucleation site of apatite carbonate by reacting with water, At the time of implantation, a layer of apatite carbonate is easily generated, which is able to adsorb cells well on the surface.

The bulk bioactive ceramics prepared with the composition as described above are first crushed by induction or the like and then passed through a 250 μm sieve to an average particle diameter of 1 by a planetary mill or a spex mill. It is made of fine powder of ˜3 μm.

Coating slurry preparation is made by mixing the powder in a solvent in which a binder is dissolved. The binding agent strongly adheres the bioactive ceramic powder to the metal implant surface during coating and also strengthens the binding between the powder particles. The solvent is an organic solvent such as alcohol, toluene, heptane, isopropyl alcohol, acetone. Binder polymer compounds such as vinyl polymer, ethyl cellulose (EC), polymethyl methacrylate (PMM), polyvinyl butiral (PVB), epoxy, and resin use. Or you may use the B73210 by Ferro Inc. which mixes a binder and a solvent directly. However, the aqueous solvent is not preferable because the glass powder is rapidly hydrated.

The concentration of the binder is 5 to 40% by weight and less than 5 because the polymer content is low, it can not play a role as a binder, when more than 40% by weight has a problem of low viscosity and not soluble in the solvent.

The mixing ratio of the powder of the bioactive ceramic and the binder solution is in the range of 30% to 100% by weight with respect to the glass powder, and preferably sufficient adhesive strength can be obtained in the range of 40 to 60% by weight. When the amount of the binder added is less than 30% by weight, the binder is not sufficiently mixed in the powder, and when the amount is more than 100% by weight, the viscosity is too thin and the solid content is low, so that the coating layer is not formed densely.

Powder of the bioactive ceramic is added to the solvent containing the binder at a predetermined ratio and mixed sufficiently using a magnetic stirrer or a 3-roll mill. At this time, 0.01 to 10% by weight of a dispersant is added to suppress aggregation of the powder and mix well, and 0.01 to 5% by weight of surfactant is added to remove bubbles in the coating liquid. The coating may be performed by sufficiently impregnating a metal implant in the coating slurry, applying a coating slurry on a brush, or spraying the coating slurry on the implant using a spray. The coating thickness is adjusted by changing the content of the glass powder in the coating liquid or repeatedly by coating. The coating layer thickness in the coating process can be adjusted in the range of 0.1㎛ 500㎛. If the thickness of the coating layer is less than 0.1㎛, there is a problem that the thickness is too thin to weaken the bond with the bone tissue. If the thickness exceeds 500㎛, the stress is concentrated on the bioactive crystallized glass coating layer with weak mechanical strength, causing cracking and breaking in the coating layer. There is a problem. After the coating is finished, the coating is dried at 30 to 110 ° C. for 1 to 12 hours. At first, after drying at room temperature for a certain time, it is better to increase the drying temperature. If the drying at a high temperature from the beginning may cause cracks due to rapid drying, when the drying temperature is 110 ℃ or more there is a problem that the decomposition of the polymer starts. After the completely dried, the coating is put into an atmosphere control electric furnace and heated to burn the polymer, and the coating layer is sintered and gradually cooled to room temperature. The temperature increase rate is preferably in the range of 0.01 to 5 ℃ / min and if the temperature increase rate is too fast, the polymer burns rapidly, there is a risk that the coating layer loses shape. In particular, near the transition temperature of vitreous bioactive ceramics, that is, the temperature at which sintering occurs rapidly (700 to 950 ° C), the temperature is slowly increased at a rate of 0.01 to 1 ° C / min so that the bioactive ceramics are tightly fused to the metal surface. . When sintering is completed and cooled, the cooling rate is gradually reduced to a cooling rate of 0.01 to 3 ° C./min to minimize residual stress due to the difference in thermal expansion coefficient between the metal substrate and the bioactive ceramic coating layer. During heat treatment, excessive oxidation of the metal substrate is suppressed by forming a reducing atmosphere using a gas such as nitrogen and argon. At the end of sintering, the coated implants are taken out, sealed packaging and sterilized by gamma-ray sterilization to produce the final product. The metal implant used for the coating is composed of at least one material selected from the group consisting of titanium, titanium alloy, cobalt-chromium alloy, and stainless steel used for medical purposes, and there is no difference in coating process characteristics or coating layer characteristics depending on the metal type. It was confirmed.

(Example)

Hereinafter, with reference to the accompanying drawings showing a preferred embodiment of the present invention described above in more detail.

1 is a graph illustrating the sintering characteristics of the bioactive glass (CSG1) powder used in the coating for explaining the present invention. FIGS. 2A and 2B are electron micrographs of the surface of the screw coated with the bioactive crystallized glass. 3A and 3B are electron micrographs of a cross section and a surface of a coating layer coated on a titanium-coated silicon substrate, and FIG. 3C is an electron micrograph of the surface of the coated specimen observed after immersion in pseudo fluid for one day. Optical micrographs of the tissues near the implants taken 8 weeks after implantation of a titanium crystal alloy coated with activated crystallized glass into a dog. Figure 5 is an optical micrograph of the tissue near the implant taken after 8 weeks after implanting the uncoated titanium alloy cortical screw in dogs.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to the following examples.

1. First embodiment

First, 99.99% calcium carbonate (CaCO ₃ ), 99.9% silica (SiO ₂ ), 99.9% borate (B ₂ O ₃ ) in a molar ratio of CaO: 45.8%, SiO ₂ : 45.8%, B ₂ O _3: 8.4 Quantify to% and mix dry. The mixed raw materials are placed in a platinum crucible, heated to 1500 degrees, held for 2 hours, completely melted, and immediately taken out and poured into a stainless mold to prepare a bioactive ceramic (a bioactive glass represented below also has the same meaning).

The bioactive glass was first pulverized to pass through a 250 μm sieve with alumina-induced powder, which was then pulverized in a planetary mill using a zirconia ball for 5 hours at 200 rpm to have an average particle diameter of 1 to 3 μm. Get The coating slurry is a mixture of alcohol, toluene solvent, polyvinyl butiral (PVB) binder, alcohol, toluene solvent and glass powder in a weight ratio of 1: 1 and zirconia balls in a polyethylene bottle for 24 hours. Mixed. The 20 mm cortical screw made of a titanium alloy (Ti-6Al-4V) was immersed in the coating slurry thus prepared, and then rotated at a high speed of 3000 rpm or more in a high speed rotating device to uniformly disperse the slurry on the metal surface and remove excess slurry. After maintaining at room temperature for 2 hours, and then slowly passed through a vertical electric furnace set at 90 ℃ at a rate of 5mm / min to dry. The metal implant thus prepared was placed in a tube electric furnace supplied with nitrogen at a flow rate of 300 cc / min, heated to a temperature rising rate of 1 ° C./min up to 850 ° C., maintained at 850 ° C. for 1 hour, and then again 1 ° C./min. Cool slowly at the cooling rate of. The determination of the sintering temperature is made from the shrinkage rate curve with the temperature of the molded body consisting only of the bioactive glass powder. 1 is a shrinkage rate curve according to the temperature of the bioactive glass powder compact obtained by pressing, where sintering starts at around 730 ° C, sintering is finished at around 830 ° C, and shrinkage change around 800 ° C is due to crystallization of the bioactive glass. Tell the fact that it occurs near the temperature. Surface electron micrographs of the screw coated by the above process are shown in FIGS. 2A and 2B. Here, the coating layer is uniformly coated along the valleys and acids of the cortical screw, and the surface shows a very dense microstructure with few pores.

2. Comparative Example

Uncoated titanium alloy cortical screw

3. Second Embodiment

Bioactive crystallized glass was coated on the silicon substrate coated with titanium instead of the metal implant substrate in the same process as in the first embodiment.

(1) bioactivity evaluation

Bioactive glass coating layer is observed, a second embodiment 10 × 10mm ² into the specimen, loading before change of the surface after 1 day passed in vivo activity is pseudo body fluid (simulated body fluid) of 35cc to see if. A cross-sectional view of the coating layer is shown in FIG. 3A, and the coating thickness is about 10 μm. Figure 3b is an electron micrograph of the surface observed before loading, Figure 3c is an electron micrograph of the surface observed after one day.

It can be seen that the surface of the fine hydroxyapatite (Hydroxycarbonate apatite, HCA) was formed only one day after the deposition.

(2) Evaluation of biocompatibility through animal clinical trial

Figure 4 is a histological optical micrograph of the area containing the implant after the implantation of the coated cortical screw of the first embodiment to the dog thigh 8 weeks, (A) is a structure of dense bone, (B) is a Structure (C) shows the structure of the opposite dense bone. Here, not only is the contact with the cortical bone more prominently coupled with the bone tissue to the peaks and bones of the screw, but even the contact with the cavernous bone is evenly coupled to the acid and bone of the screw. These findings are not found in the comparative example (uncoated screw) shown in FIG. 5 (A) showing the structure of the dense bone, (B) the structure of the spongy bone, and (C) the structure of the opposite dense bone, respectively. In the comparative example, only a small amount of bone tissue was bound to the cortical contact surface, and bone tissue was hardly bound to bone and acid at the contact surface of the cavernous bone. In addition, the coating layer of the first embodiment was absorbed relatively uniformly, so that the direct coupling between the screw and the bone was increased, and the phenomenon that the coating layer remained and was separated from the screw was not observed. Table 1 shows the torque values to estimate the bone bonding force of the first example and the comparative example. Torque was slowly rotated in the direction of screw removal to measure the torque at the time of rapid decrease in resistance as the screw moved, and this value was evaluated as an index of bone-screw coupling. The torque of Example 1 was 8.07 cN · M, which was statistically significantly higher than that of 6.37 cN · M of the comparative example.

Torque (cN · M) Example 1 8.07 ± .64 Comparative Example 2 6.37 ± .85

The present invention made as described above is increased compared to the implantation of the graft without coating the bone bonding force by implanting the metal graft coated with the bioactive glass using the bioactive glass having the appropriate bioabsorbability and low temperature sintering characteristics And bone tissue is generated around the implant to ensure a firm fixation. In addition, the coating process is very inexpensive and simple compared to other coating processes, providing a very advantageous effect on production.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments and the general knowledge in the technical field to which the present invention pertains without departing from the spirit of the present invention. Various changes and modifications will be made by those who possess.

Claims (8)

Biologically active ceramics comprising calcium oxide, silica, and borate. The method of claim 1, wherein the calcium oxide, silica, and borate are in a molar ratio of 40 to 49% calcium oxide (CaO), 40 to 49% silica (SiO ₂ ), and ₂ to 20% B ₂ O ₃ , respectively. Bioactive ceramic, characterized in that. A metal implant was used to prepare a slurry containing powders of bioactive ceramics each composed of 40 to 49% calcium oxide (CaO), 40 to 49% silica (SiO ₂ ), and ₂ to 20% B ₂ O _3. A bioactive ceramic coated metal implant, characterized in that it is produced by sintering after coating on a substrate. 4. The bioactive ceramic coated metal implant according to claim 3, wherein the sintering treatment is performed at 700 to 950 캜. Dissolving the polymer binder in an aqueous or organic solvent to obtain a solution; Powders of bioactive ceramics composed of calcium oxide (CaO): 40 to 49%, silica (SiO ₂ ): 40 to 49%, and B ₂ O ₃ : 2 to 20% in molar ratios were added to the solution and stirred. Preparing a slurry; Coating the slurry on a metal implant substrate to obtain a coating; And drying the coating to heat treatment to burn the polymer binder and to sinter and crystallize the remaining bioactive ceramic. The method of claim 5, wherein the metal implant is made of at least one material selected from the group consisting of titanium, titanium alloys, cobalt-chromium alloys, and stainless steel. The method of claim 5, wherein the organic solvent is at least one selected from alcohol, toluene, heptane (isoptane), isopropyl alcohol, acetone, the polymer binder is a vinyl (Vinyl) polymer, ethyl cellulose (EthylCellulose, EC) , Graft metal coated with bioactive ceramics using at least one material selected from the group consisting of polymethyl methacrylate (PMM), polyvinyl butiral (PVB), epoxy, and resin Method of making sieves. 6. The method of claim 5, wherein the slurry of the bioactive ceramic is mixed with 30 to 100% by weight of the slurry containing the polymer binder.