JP2787829B2 - Manufacturing method of calcium phosphate ceramic implant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an implant.

Implants formed using hydroxyapatite, which has excellent biocompatibility, must be molded into a variety of complex shapes depending on the application.However, conventional methods such as uniaxial pressing and rubber pressing require molding. In order to improve the quality such as properties, dimensional accuracy and surface lubricity, post-processing such as finishing and surface polishing is required. Therefore, in the case of ceramics having relatively low strength such as calcium phosphate ceramics, countless macrocracks and microcracks are formed on the surface by post-processing, and the strength is reduced. Further, the strength decrease due to dissolution in a living body is further increased, which is a serious problem in practical use.

On the other hand, in recent years, attempts have been made to apply an injection molding method, which has the advantage of being the most efficient method capable of mass-producing processed products having complicated shapes, to ceramic materials, but the production cost is high and kneading is required. It cannot be said that it has reached practical use because it contains many technically difficult points such as selection of organic materials and determination of degreasing conditions. Further, materials having a large specific surface area of the ceramic raw material powder itself require more organic materials, and thus have become increasingly technically difficult. Hydroxyapatite has a remarkably large specific surface area among ceramic materials, is excellent in the ability to adsorb various substances, and is widely used as an adsorption column for liquid chromatography. It was one of the ingredients said to be.

As a result of our diligent efforts, after kneading the calcium phosphate powder with the thermoplastic organic material, injection molding was performed, and further, degreasing and sintering were performed. , Dimensional accuracy, surface lubricity, etc., and the strength is improved because macrocracks and microcracks are not formed on the material surface,
The inventors have found that there is little decrease in strength in a living body, and have reached the present invention.

Materials and Production Method The calcium phosphate compound having a Ca / P molar ratio of 1.5 to 2.0 in the present invention is specifically exemplified by, for example, hydroxyapatite, tricalcium phosphate, tetracalcium phosphate, and the like. A method is proposed in which a slurry synthesized by a method or the like is spray-dried to obtain spherical fine particles having a particle size of 0.1 to 150 µ and fired at 300 to 1300 ° C.

In addition to spray-dried powder, use crushed powder or granulated powder by various pulverization methods such as ball mill, sample mill, jet mill, atomizer, or granulated powder by another synthesis method such as pyrolysis method, alkoxide method, dry method You may. Further, calcined powder obtained by sintering natural bones and teeth such as cow bones and fish bones at a high temperature can also be used.

Also, Mg, Zr, Fe, Ti , Si, and cations such as Sr, Cl ^-, F ^-,
I ^-, CO ₃ ^2- anions, such as may be used those containing about 0-10%.

Next, a binder,
Various organic materials are appropriately kneaded for the purpose of peptizer, lubricant, plasticizer, wetting agent, defoaming agent, coupling agent, surfactant, protective colloid agent and the like. Examples of the binder include polyethylene, polypropylene, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylate copolymer (EEA), acrylic resin, polystyrene, SMR resin, cellulose resin, and polyester.

Examples of the lubricant include waxes such as paraffin wax and microcrystalline wax, higher fatty acids, fatty acid acids, fatty acid esters, and the like. Examples of the plasticizer include dibutyl phthalate and butyl benzene phthalate.

These organic materials are added to calcium phosphate
Add 50% by weight, and melt and knead well at 100-250 ° C using a pressure kneader. This is crushed and made into a granule, which is then put into an injection molding machine, and is injection-molded into an implant molding die previously processed into a predetermined shape. Next, the removed molded body is put into a normal pressure or pressure degreasing furnace, and 350 to 6 days in 2 to 7 days.
Degas the organic material slowly at 00 ° C.

Finally, the molded body excluding the organic components 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. Alternatively, sintering can be performed at 150 to 800 ° C. and 10 to 15,000 t / cm ² using hot isostatic pressing (HIP).

An implant refers to an instrument or device that is implanted in a living body for a long term and used for clinical treatment in the fields of medicine and dentistry. Representative ceramic implants include a percutaneous device (Perctaneous Device) and an artificial blood vessel (Artificial
Vascular Prosthesis, Blood Access Device, Artificial toot
h root), Artificial Trachea, Artificial Bone Prosthesis, Sensor
and so on.

Experiment 1 After synthesizing by a wet method, an organic material was added at a ratio shown in Table 1 to hydroxyapatite pulverized by a jet mill.

This was sufficiently kneaded with a kneader Labo Plastomill manufactured by Toyo Seiki, and then injection-molded into a mold capable of obtaining a cylindrical molded body by an injection molding machine MD-20 manufactured by Yamashiro Seiki. The organic matter was removed from this in a degreasing furnace SHKS-2 manufactured by Kono Seisakusho at 550 ° C. for about 5 days.

The mixture was fired at 1250 ° C. in a firing furnace BM-1530 manufactured by Siliconit Kokusai Kogyo to obtain a cylindrical dense sintered body having an outer diameter of 7.6 mm, an inner diameter of 3.5 mm, and a length of 10 mm.

FIG. 1 shows the results obtained by performing a pressure tube test using an Instron Material Testing Machine Model 1123 and determining the compressive tensile strength. As a comparison, Toyo hydraulic made uniaxial press machine, a compression molded cylindrical body at a pressure of about 1t / cm ² and secondary processing using a lathe and drilling machine, after obtaining the similar cylinder, in the same manner A sintered body was used.

As a result, the molded body according to the present method is 1.
There was almost 5 to 2 times the strength. In addition, it has been clarified that it has a strength equal to or higher than that of a columnar shape which is not subjected to secondary processing only by compression molding.

Experiment 2 After synthesizing by a wet method, an organic material was kneaded at a ratio shown in Table 2 into a spray-dried powder.

This was molded in a bending test sample molding die and then sintered as in Experiment 1. These are implanted under the back of the adult dog,
Removed after 3 months and 3 months. FIG. 2 shows the results of measuring the three-point bending strength of these samples with the Toritsu Autograph AG2000A. As a control, a disk-shaped sintered compact obtained by compression molding with a uniaxial press machine and then cut by an isomet diamond cutter 11-180 was used.

The test piece produced by this method had about 9% greater strength than the control. One month after implantation, the decrease in strength was smaller than that of the control, about 8% in this method and about 13% in the control. From this, it was found that the present method has higher strength and less decrease in strength in a living body than the conventional method requiring secondary processing.

From the above, it was found that the present method is excellent as a method for molding a long-term implantable implant using a calcium phosphate ceramic.

[Brief description of the drawings]

FIG. 1 is a graph showing the compressive tensile strength in the example of the present invention, and FIG. 2 is a graph showing the bending strength in the example of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-21763 (JP, A) JP-A-62-167250 (JP, A) JP-A-62-270164 (JP, A) JP-A-2- 6375 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) A61L 27/00

Claims (1)

(57) [Claims] 1. Calcium phosphate compound powder and 5 to 50% by weight of an organic material are melted and kneaded at 100 to 250 ° C., injection-molded, degreased at 350 to 600 ° C. for 2 to 7 days, and fired. A method for producing a calcium phosphate ceramic implant.