JPH01268560A - Preparation of calcium phosphate ceramics implant - Google Patents

Abstract

PURPOSE:To enhance strength and to reduce the lowering of strength in a living body, by kneading a calcium phosphate powder with a thermoplastic org. material and performing the injection molding of the kneaded mixture to degrease and sinter the molded one. CONSTITUTION:A calcium phosphate powder and an org. material are kneaded to be subjected to injection molding and the obtained molded body is degreased and sintered to prepare a calcium phosphate ceramics implant. For example, 5-50wt.% of the org. material is added to the calcium phosphate powder and the resulting mixture is well melted and kneaded at 100-250 deg.C using a press kneader. The kneaded mixture is ground and granulated to be charged in an injection molding machine and injected in an implant body mold preliminarily processed into a predetermined shape to be subjected to molding. The molded body is taken out to be introduced into an atmospheric pressure or pressurized degreasing furnace and the org. material is slowly degassed and removed at 350-600 deg.C for 2-7 days. At last, the molded body wherein the org. material is removed is slowly sintered at 800-1,300 deg.C for 1-3 days in a vacuum, atmospheric pressure or pressurized sintering furnace to obtain a dense ceramic molded body.

Description

[Detailed description of the invention] The present invention relates to an implant.

Implants made using hydroxyapatite, which has excellent biocompatibility, must be molded into various complex shapes depending on the intended use. In order to improve quality such as formability, dimensional accuracy, and surface smoothness, post-processing such as finishing and surface polishing is required.

Therefore, in the case of ceramics with relatively low strength, such as calcium phosphate ceramics, numerous macrocracks and microcracks are formed on the surface during post-processing, leading to a decrease in strength. Furthermore, the strength decreases further due to in vivo dissolution, which is a major problem in practical use.

On the other hand, attempts have been made in recent years to apply injection molding to ceramic materials, which has the advantage of being the most efficient method for mass-producing processed products with complex shapes.
In addition to high production costs, this method cannot be said to be of practical use because it involves many technically difficult points, such as the selection of organic materials to be kneaded and the determination of degreasing conditions. Furthermore, materials with a large specific surface area of the ceramic raw powder itself require a larger amount of organic material, which has become increasingly technically difficult. Furthermore, hydroxyapatite has a much larger specific surface area than other ceramic materials, has excellent adsorption ability for various substances, and is widely used as an adsorption column for liquid chromatography, making it an outstanding material for injection molding. It was one of the raw materials said to be impossible to mold.

As a result of our diligent efforts, we have successfully kneaded calcium phosphate powder into a thermoplastic organic material, injection molded it, degreased it, and sintered it to create a compact ceramic body with sufficient moldability and homogeneity through subsequent processing. This book was developed based on the findings that the strength of the material is improved because it has excellent properties such as hardness, dimensional accuracy, and surface smoothness, and does not create macrocracks or microcracks on the surface of the material. This invention has been achieved.

Materials and manufacturing method Specific examples of the calcium phosphate compound having a Ca/P molar ratio of 15 to 2.0 in the present invention include hydroxyapatite, tricarnoum phosphate, tetracalcium phosphate, etc., and the manufacturing method thereof is as follows: For example, a method is proposed in which a slurry synthesized by a wet method or the like is spray-dried to form fine spherical particles with a particle size of 0.1 to 150 μm, and the resulting particles are fired at 300 to 1300°C.

In addition to spray-dried powder, crushed powder or granulated powder can be produced using various pulverization methods such as ball mills, sample mills, jet mills, and atomizers, or other synthesis methods such as thermal decomposition, alkoxide methods, and dry methods. It is better to use grain flour. or,
It can be made by using sintered powder made by sintering natural bones and teeth such as cow bones and fish bones at high temperatures.

Further, a material containing cations (such as Mg, Zr, Fe, Ti, Si, Sr, etc.) and anions such as Cl2-, F-, I-, CO3'- in an amount of about θ to 10% may be used.

Next, various organic materials are appropriately added to this calcium phosphate compound powder for the purposes of binding agents, peptizers, lubricants, plasticizers, wetting agents, antifoaming agents, coupling agents, surfactants, protective colloid agents, etc. Knead. As a binder, polyethylene, polypropylene, ethylene-vinyl acetate copolymer (
No. 1 VA), ethylene-acrylate copolymer (EEA
), acrylic resin, Boris tyreno, SMR resin, cellulose resin, polyester, etc.

Examples of the lubricant include waxes such as paraffin wax and microcrystalline wax, higher fatty acids, fatty acid acids, and fatty acid esters. Examples of plasticizers include dibutyl phthalate and butylbennon phthalate.

5 to 5 of these organic materials to calcium phosphate powder
Add 0% by weight and use a pressurized knee gun to add 100 to 250
Melt and knead well at °C. This is crushed and made into granules, which are then put into an injection molding machine and injection molded into an implant molding die that has been previously processed into a predetermined shape. Next, the molded body taken out is placed in a normal pressure or pressurized degreasing furnace, and the material is slowly degassed at 350 to 600°C for 2 to 7 days.

Finally, the molded body except for part a is slowly sintered at 800 to 1300°C for 1 to 3 days in a vacuum, normal pressure, or pressure sintering furnace to obtain a dense ceramic molded body. Or, using hot isostatic compression (1-IIP), 150 to 800 °C,
It is also possible to sinter at 10 to 15,000 t/cm.

In the fields of medicine and dentistry, an implant refers to an instrument or device that is implanted in a living body and left in place for a long period of time to be used for clinical treatment. Typical ceramic implants include Percutaneous Devices and Artificial Vascular Pros.
thesis), Blood Access Device (B100
Fl Access Device), artificial tooth root (Ar
tiritialtooth root), artificial trachea (
Artificial Trachea), Human 1-Bone (
Artificial Bone Prosthesis
s), sensor (S (!nsor), etc.).

Experiment 1 Drilling material was added to hydroquine apatite synthesized by a wet method and then ground in a jet mill in the proportions shown in Table 1.

Table 1 This was sufficiently kneaded using a Labo Blast Mill, a kneader manufactured by Toyo Seiki, and then injection molded into a mold capable of obtaining a cylindrical molded body using an injection molding machine MD-20 manufactured by Yamaguchi Seiki. This was heated at 550°C for about 50 minutes in a degreasing furnace S I-I K S-2 type manufactured by Kou Seisakusho.
Organic components were removed for several days.

Sintered at 1250°C in a siliconite high-temperature industrial firing furnace model BM-1530, with an outer diameter of 7.6 mra and an inner diameter of 3.5 mra.
A cylindrical dense sintered body with tam and length of 1OIII11 was obtained.

A pressure tube test was carried out using an Instron material testing machine model 112a, and the results of compressive tensile strength are shown in FIG. For comparison, a Toyo Hydraulic shaft press machine produces approximately 1 t/cI11.
A cylindrical body compression-molded at a pressure of 100 mm was subjected to secondary processing using a lathe and a drill press to obtain a cylindrical body similar to that described above, and then a sintered body was used in the same manner.

As a result, the molded body according to the present invention was made into a cylindrical shape by secondary processing after compression molding using a -axis press, compared to B.
It was 5 to 2 times as strong.

It was also revealed that the strength was equal to or higher than that of a cylindrical product that was only compression molded and did not undergo secondary processing.

Experiment 2 Organic materials were kneaded in the proportions shown in Table 2 to the powder that had been synthesized by a wet method and then spray-dried.

Table 2: Bending test sample After molding with a mold, it was sintered in the same manner as in Experiment 1. These are implanted subcutaneously in the back of an adult.
They were taken out after 1 month and 3 months. 3 of these samples
The point bending strength was measured using a Kosha Autograph A 0200OA, and the results are shown in Figure 2. As a control, a disc-shaped sintered body that had been compression-molded using a -axis press and then cut using an isometric diamond cutter 11-180 was used.

The test specimens prepared with the present invention had approximately 9% greater strength than the control. In addition, the decrease in strength after the implant injury was smaller than that of the control, about 8% for the original and about 13% for the control. From this, it was found that the strength is greater than that of conventional methods which inherently require secondary processing, and the strength decreases less in vivo.

From the above, it was found that the present invention is an excellent method for forming implants for long-term in-vivo implantation using calcium phosphate ceramics.

[Brief explanation of the drawing]

FIG. 1 is a graph showing compressive tensile strength in an example of the present invention, and FIG. 2 is a graph showing bending strength in an example of the present invention. Patent Applicant: Advance Co., Ltd. Figure 2 1 Neimerito #8 Seki (Geki Onpe S)

Claims (1)

[Claims] (1) A method for producing a calcium phosphate ceramic implant, which comprises kneading a calcium phosphate compound powder and an organic material, performing injection molding, followed by degreasing and sintering.