JPH02184563A - Ceramics for living body and production thereof - Google Patents

Abstract

PURPOSE:To contrive to provide a living body ceramics having improved mechanical strength and living body affinity by comprising a central portion consisting mainly of thick alumina and a surface portion consisting mainly of porous hydroxyapatite(HAP) in a state having continuously changed (alumina/HAP) ratios and porosities. CONSTITUTION:An alumina sol obtained by mixing aluminum isopropoxide with isopropanol is mixed with 0.05-0.2mum particle diameter HAP so as to give a composition having an alumina/HAP mol ratio of approximately 7/3 after gelled, and further mixed with a foaming agent such as N,N'-dinitroso pentamethylene tetramine in an amount of approximately 0.1wt.%. The mixture is subjected to a centrifugal separation process to give a constant concentration distribution wherein the concentrations of the HAP and foaming agent in the sol are inclined, followed by subjecting the centrifuged product to a heating, pH-adjusting or any other process to produce a wet gel. The wet gel is dried, heated to approximately 300 deg.C at a temperature-raising rate at approximately 20 deg.C/hr under vacuum, held in the states for approximately 8hr, subjected to a foaming treatment, to a water-desorbing and adsorbing treatment and subsequently to a sintering treatment of approximately 1200 deg.C for about 24hr to provide a ceramic for living bodies.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to bioceramics used in the medical field and a method for producing the same.

[Prior Art] When a bone defect occurs, the patient's own autologous bone or human allogeneic bone is transplanted. If the defect to be replaced is large and autologous bone alone is insufficient, or if suitable allogeneic bone is not available, artificial bone is used.

The material of this artificial bone is mostly ceramics.

In the early stages of development, bioinert materials were studied that were safe for living organisms but did not fuse with natural bone. In particular, alumina is still widely used due to its excellent mechanical strength.

However, recently, bioactive artificial bones that are biosafe and bond with natural bone have been developed.

A typical biological glass is SiO2-CaO-
Na 20-P 205 glass is an example, but it has low mechanical strength and cannot be put to practical use by itself. For this reason, S i O2, which has high mechanical strength, is currently used.
-Ca O-M g O-P 20 Research on carious bioglass is progressing.

Biological glasses are typically made using high temperature melting methods.

Powdered oxides, carbonates, hydroxides, etc. are mixed as raw materials, placed in a crucible, and melted in a melting furnace for 1400
C). After melting, the molten liquid is poured into a mold and cooled to create it. However, if it remains in this glass state, it has a lower mechanical strength than human bone, which poses a practical problem.

In addition, in order to improve biocompatibility and mechanical strength, attempts are being made to obtain crystalline biological glass by crushing the produced glass, shaping it, and sintering it at around the crystallization concentration.

At this time, apatite and wollastonite crystals are precipitated in the glass, which improves biocompatibility and mechanical strength.

[Problems to be Solved by the Invention] Generally, when biological glass is actually used for bone tissue, mechanical strength nearly three times that of cortical bone is required. The bending strength of cortical bone is approximately 170 (MN/m2), and the bending strength required for biological glass is approximately 500 (MN/m2).
This is more than three times the value of current biological glass. In addition, in order to increase biocompatibility, there is a method of forming a porous body and generating new bone within the pores. However, if it is made into a porous material, the mechanical strength is further reduced, so it has the problem that it cannot be used in practice.

The present invention is intended to solve these problems, and its purpose is to provide porous bioceramics with excellent mechanical strength and biocompatibility, and a method for producing the same.

[Means for Solving the Problems] The bioceramic of the present invention has a composition mainly composed of alumina in the center and a composition mainly composed of HAP in the surface part, and the ratio of alumina and HAP and the porosity are It is characterized by the fact that it changes continuously.

Further, according to the production method of the present invention, R is added to the alumina sol.
After adding and mixing fine powders of AP and blowing agent, the concentration of HAP and blowing agent in the sol is graded by centrifugation.
It is characterized by gelation and sintering at a stage with a certain concentration distribution.

[Function] The bioceramic of the present invention has a central part mainly composed of dense alumina with excellent mechanical strength, and a surface part that comes into contact with living tissues mainly contains a porous material of HAP, which has high biocompatibility. Therefore, it can have two properties: mechanical strength and biocompatibility.

Furthermore, since the two components of alumina and RAP change continuously, there is no interface and there is no deterioration in properties such as stress fracture occurring on the interface.

Furthermore, according to the production method of the present invention, HAP powder is added to the alumina sol, the concentration of this powder is graded by centrifugation, and the two components and the porosity are reduced by gelling and sintering. It can be changed continuously in ceramics.

[Example] A mixed solution of aluminum isopropoxide and isopropanol is hydrolyzed under acidic conditions to create a sol. To this sol, HAP fine powder with a particle size of 0.05 to 0.2 (μm) is added, and 0.1 (wt%) of N,N'-dinitrosopentamethylenetetramine is added and dispersed as a blowing agent. and place it in the designated container. The amount of HAP added at this time is
The composition after gelation is a molar ratio of alumina/HAP=7/3
It was adjusted so that Thereafter, this container is rotated at a constant rotational speed, and when the fine powder of HAP and blowing agent shows a constant concentration distribution, gelation is performed by means such as heating and pH adjustment. Next, this wet gel was taken out from the container, dried for two weeks, and then dried at 20 ("C/
Heated to 300 ("C) at a temperature increase rate of 8 hours), and at the same concentration
After holding for a time and performing foaming treatment and desorption water treatment, 30
(Heat to 600 ('C) at a heating rate of 'C/hour, hold at the same concentration for 6 hours, further heat to 1200 ('C) at a heating rate of 30 (℃/hour), and hold at the same concentration for 24 hours. Hold for a while and perform sintering.

The shape of the obtained sintered body is φ10Xt30 (im) and φ
There are two types: 40Xt8 (mm). Regarding the former,
The bending strength and bond strength with human bone were measured, and the results are shown in Table 1. Conventional examples 1 to 4 in the table are each
Alumina, HAP, 5iO2-Ca O-N a 20
- P 205 festival main glass, Si02- Ca O-
This is a value measured for M g O-P 205 series crystallized living crow. Note that the bonding strength with human bone is the value after 8 weeks.

Table 1 From Table 1, the bioceramic of the present invention has both the mechanical strength of alumina and the biocompatibility of crystallized bioglass, and is considered to be capable of withstanding long-term use in living organisms. .

The remaining sample was divided into eight equal parts from the center to the outer periphery, and the composition and porosity of each sample were analyzed and the results are shown in FIG.

The composition near the center is mostly alumina, but the HAP composition increases continuously toward the outer periphery.

Normally, when ceramics having a plurality of compositions are sintered at the same time, large stress is often applied to the bonded surfaces, resulting in damage due to differences in shrinkage rates, thermal W tensile coefficients, etc.

However, since the present invention uses a sol-gel method, it becomes possible to easily gradient the composition at the sol stage. Therefore, by continuously changing the composition distribution of alumina and HAP in the sintered body, it is possible to eliminate so-called bonding surfaces and relieve stress, thereby producing bioceramics that have the characteristics of two types of ceramics. is now possible.

In addition, the center part has a dense structure mainly composed of alumina, and the surface part is made of porous HAP with high porosity.1, it has extremely high mechanical strength compared to ordinary porous ceramics. and has good biocompatibility.

The sol-gel method is used as the manufacturing method, and the composition distribution can be easily changed by changing the amount of HAP added, the particle size distribution of the powder, and the rotation speed during centrifugation, thereby achieving the required performance. You can easily create bioceramics that suit your needs.

Furthermore, the sol-gel method has a large degree of freedom in shape, and by selecting the shape of the container in which the gel is made, it can be controlled to a shape close to the final shape desired at the end of sintering. For this reason,
There is no need for secondary processing, and significant cost reductions can be achieved.

This porous bioceramic and its manufacturing method are not limited to alumina and HAP systems, and can also be combined with materials with higher mechanical strength or materials with excellent biocompatibility.

[Effects of the Invention] As described above, according to the present invention, mechanical strength and biocompatibility are improved by continuously changing the ratio and porosity of alumina, which has excellent mechanical strength, and HAP, which has biocompatibility. This has the effect of providing bioceramics that have two properties of affinity.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the composition distribution and porosity distribution of the bioceramic of the present invention. The sample numbers in the figure represent the positions of the samples where the composition analysis was performed, with 1 indicating the center and 8 indicating the outer periphery. Applicant: Seiko Epson Co., Ltd. Agent Patent Attorney Tosuzu, 3rd Department (1 other person)

Claims (2)

[Claims] (1) The center is composed mainly of dense alumina, and the surface is porous hydroxyapatite (hereinafter referred to as H
A bioceramic having a composition mainly composed of HAP (abbreviated as AP), and characterized in that the ratio of alumina to HAP and the porosity change continuously. (2) After adding and mixing fine powders of HAP and blowing agent into the alumina sol, the concentration of HAP and blowing agent in the sol is graded by centrifugation, and gelation occurs when a certain concentration distribution is achieved. 2. The method for producing bioceramics according to claim 1, further comprising the steps of: , foaming treatment, and sintering.