JPH0595994A - Production of porous crystallized glass - Google Patents

Abstract

PURPOSE:To provide a method for producing a porous crystallized glass having high mechanical strength and being integrated with a bioorganization in a short time. CONSTITUTION:At first, a slurry is prepd. by mixing 30% ethanol and 3% polyvinyl butyral(PVB) to 100wt.% glass powder having a compsn. of 22-50% SiO2, 8-30% P2O5, 20-53% CaO, 1-16% MgO, 0.1-2% F2, 0-9% Al2O3, and 0-5% B2O3. Then, after a urethane foam is impregnated with the slurry and is dried, it is heat-treated to remove the urethane foam and PVB by burning and to sinter and crystallize the glass powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous crystallized glass, and more particularly to a method for producing a porous crystallized glass used for filling a bone defect.

[0002]

2. Description of the Related Art Conventionally, cancellous autologous bones, so-called cancellous bones, collected from a normal site of a patient have been used to replace a defective bone. There are problems that the patient's pain is great due to the excision, a great deal of labor is required to perform the operation, and the amount of autogenous bone collected is limited.

Under these circumstances, it has been attempted to artificially produce a cancellous bone-like filling material. As a typical example, porous ceramics such as hydroxyapatite have been proposed. Hydroxyapatite has good biocompatibility,
Moreover, it is a filling material having high bioactivity and, after filling in a defective portion, new bone grows and penetrates into the pores and is easily integrated with living tissue. However, this filling material has a drawback that its use site is significantly limited because the mechanical strength of the material itself is not sufficient.

Therefore, as a supplementary material having high mechanical strength,
Japanese Patent Publication No. 2-49260 discloses a porous crystallized glass in which crystals such as apatite (Ca ₁₀ (PO ₄ ) ₆ O) and wollastonite (CaO · SiO ₂ ) are deposited.

[0005]

[Patent Document 1] Japanese Patent Publication No. 2-492
The porous crystallized glass disclosed in No. 60 is obtained by uniformly mixing and molding glass powder and combustible substance particles, and then burning the combustible substance particles by heating to sinter and crystallize the glass powder. It is produced by

However, since the porous crystallized glass produced by such a method has a poor fluidity of the body fluid into the pores even if it is filled in the bone defect portion, new bone is unlikely to grow and invade, so It takes a long time to integrate with the tissue. Further, since a large amount of combustible substance is used, the glass is altered when it is burnt and removed, and the sinterability decreases. Therefore, there is a problem that the strength of the obtained crystallized glass is low.

An object of the present invention is to provide a method for producing a porous crystallized glass which has high mechanical strength and can be integrated with living tissue in a short time.

[0008]

As a result of various studies, the present inventors have found that the material itself has biocompatibility and bioactivity in order to facilitate the growth and invasion of new bone. Furthermore, they have found that the structure must be similar to that of cancellous bone, that is, a three-dimensional network structure having three-dimensionally continuous external communication holes, and have proposed the present invention.

That is, in the method for producing a porous crystallized glass of the present invention, the weight percentage is SiO ₂ 22 to 50%, P ₂ O.
_{5 8~30%, CaO 20~53%,} MgO 1~1
6%, F ₂ 0.1-2%, Al ₂ O ₃ 0-9%, B ₂ O
A glass powder having a composition of _{30 to} 5% is mixed with an organic solvent and a binder to form a slurry, and the slurry is impregnated into an organic porous body having a three-dimensional network structure, dried, and then heat-treated. It is characterized in that the organic porous material and the binder are burned and removed, and the glass powder is sintered and crystallized.

[0010]

According to the method for producing a porous crystallized glass of the present invention, a porous body having a three-dimensional network structure in which body fluid can easily flow is formed. Further, biocompatible apatite, wollastonite having high mechanical strength and bioactivity, and diopside (CaO.MgO) having high mechanical strength.
.2SiO ₂ ) is deposited, and thus the obtained porous crystallized glass is excellent in these characteristics. Moreover, the amount of flammable substances used is small, and the glass does not deteriorate.

The reason why the composition of the glass powder used in the present invention is limited as described above will be described below.

SiO ₂ is a constituent of wollastonite and diopside, and its content is 22 to 50%. If the SiO ₂ content is less than 22%, only a small amount of these crystals will precipitate, and the mechanical strength of the crystallized glass will be insufficient. If the SiO ₂ content is more than 50%, the viscosity of the glass melt will increase, making it difficult to melt the glass. In addition, the precipitation amount of apatite crystals decreases.

P ₂ O ₅ is a constituent of apatite,
Its content is 8-30%. When P ₂ O ₅ is less than 8%, the devitrification becomes high and the glass becomes difficult to melt, and only a small amount of apatite precipitates. Again 3
If it is more than 0%, the amount of wollastonite and diopside deposited will be small.

CaO is a constituent of apatite, wollastonite and diopside, and the content thereof is 20-.
53%. If the content of CaO is less than 20%, only a small amount of these crystals precipitates, and if the content of CaO is more than 53%, it is difficult for the melt to become glass.

MgO is a constituent of diopside,
Its content is 1 to 16%. If MgO is less than 1%, it is difficult for the melt to become glass, and if it is more than 16%, only a small amount of apatite or wollastonite is precipitated.

F ₂ is a nucleating component, and its content is 0.1-2%. When F ₂ is less than 0.1%, the nucleation is insufficient, and when it is more than 2%, the crystallization rate is increased and the sinterability is deteriorated.

The content of Al ₂ O ₃ is 0 to 9%. A
If l ₂ O ₃ is more than 9%, the biocompatibility becomes poor.

The content of B ₂ O ₃ is 0 to 5%. B ₂
When O ₃ is more than 5%, it takes a long time to integrate with living tissue. The glass powder used in the present invention includes Li ₂ O, Na ₂ O, K ₂ O, SrO and T in addition to the above components.
One or two or more selected from the group consisting of iO ₂ , ZrO ₂ , Nb ₂ O ₅ and Ta ₂ O ₅ can be contained in a total amount of 10% or less.

Next, a method for producing the porous crystallized glass of the present invention will be described.

First, a glass powder having the above composition is mixed with an organic solvent and a binder to form a slurry. Usually, water is used as the dispersion medium. However, the glass of the above-mentioned system has poor water resistance and is corroded by contact with water to reduce the sinterability. Therefore, an organic solvent is used instead of water. As the organic solvent, one having a boiling point of 200 ° C. or lower, particularly alcohols such as methanol, ethanol, propanol and butanol, is preferably used alone or in combination so as to be easily dried. Although various binders can be used, polyvinyl butyral (PVB) is particularly preferable. Further, the mixing amounts of the organic solvent and the binder are preferably 20 to 100% and 0.5 to 4% with respect to 100% by weight of the glass powder. Next, the slurry is impregnated into an organic porous body having a three-dimensional network structure (for example, urethane foam) and dried. Thereafter, these are heat-treated to burn and remove the organic porous material and the binder, and the glass powder is sintered and crystallized to obtain a porous crystallized glass having a three-dimensional network structure.

The average pore diameter and porosity of the obtained crystallized glass can be obtained at desired values by appropriately selecting the organic porous material to be used and by adjusting the amount of the slurry to be impregnated. However, the average pore size is 20 to 2000 μm and the porosity is 66 to 95 for the following reasons.
Volume% is preferred. That is, if the average pore size is smaller than 20 μm, new bone cannot penetrate, and if it is larger than 2000 μm, sufficient mechanical strength cannot be obtained. When the porosity is less than 66%, a sufficient amount of new bone does not penetrate and it is easy to include independent pores. On the other hand, when the porosity is higher than 95%, the skeleton structure of the porous body is likely to collapse, and sufficient mechanical strength cannot be obtained.

[0022]

EXAMPLES The method for producing the porous crystallized glass of the present invention will be described below based on Examples and Comparative Examples.

(Example) Table 1 shows an example of the present invention (Sample N).
o. 1 to 5).

[0024]

[Table 1]

Sample No. 1-5 were prepared as follows. Glass raw materials were blended so as to have the composition shown in the table, put in a platinum crucible, melted at 1400 to 1600 ° C. for 3 hours, roll-molded, pulverized with a ball mill, and classified with a 200-mesh sieve. To 100% by weight of this glass powder, 30% of ethanol (first grade) and 3% of PVB were mixed to form a slurry, which was impregnated in urethane foam and dried, and then heated at a rate of 30 to 300 ° C. for 1 hour. , 1000
A sample having a three-dimensional network structure was obtained by firing at ˜1200 ° C.

As is apparent from the table, each sample had an average pore diameter of 150 to 400 μm and a porosity of 68 to 80%. Further, when the precipitated crystal was obtained by X-ray diffraction, the sample No. Sample No. 1 has apatite and wollastonite precipitated. In Nos. 2 to 5, diopside was further precipitated.

Next, each sample was cut into a size of 10 × 10 × 10 mm, and the compressive strength was measured by an autograph. As shown in the table, values of 121 to 167 kg / cm ² were shown. In addition, the bone defect (4φ
(10 mm) was formed, each sample was filled and the post-operative course was observed. After 2 weeks, formation of new bone was observed inside the pores in all the samples.

Comparative Example 1 Hydroxyapatite synthesized by the wet method was dried, calcined at 800 ° C., pulverized and classified with a 200 mesh sieve. Next, 100% by weight of this hydroxyapatite powder was mixed with 30% of ethanol (first grade) and 3% of PVB to form a slurry, which was impregnated in urethane foam and dried, and then 30% per hour.
The temperature was raised at a rate of ° C and firing was performed at 1200 ° C. The sample thus obtained had a three-dimensional network structure and had an average pore diameter of 200 μm and a porosity of 70%.

When the compressive strength and the rate of new bone formation of this sample were measured in the same manner as in the example, formation of new bone was observed within the pores after 3 weeks. However, the compressive strength of the sample was as low as 20 kg / cm ² .

(Comparative Example 2) Sample No. in the table. Glass having a composition of 1 was crushed and classified with a 200-mesh sieve, and then polymethylmethacrylate (PM
(MA) beads to which a small amount of paraffin was added were added to the glass powder in an amount of 60% by weight and mixed by heating, and the surface of the beads was thinly coated with the glass powder. Then, this is put into a mold, and a pressure of 600 kg / cm ² is applied to mold it.
The temperature was raised at a rate of 30 ° C. per hour, and the sample was baked at 1200 ° C. to obtain a sample. The sample thus obtained was a porous body having independent spherical pores or continuous pores in which spherical pores were connected at the contact points of the spheres, and did not have a three-dimensional network structure. The average pore diameter is 200 μm and the porosity is 7
It was 0%, and apatite and wollastonite were precipitated.

The compressive strength and the rate of new bone formation of this sample were measured in the same manner as in the example, and the compressive strength was 1
10 kg / cm ² and sample No. 36k compared to 1
The g / cm ² was also low. Even after 3 weeks, formation of new bone was hardly observed inside the stomata.

[0032]

As described above, according to the method for producing a porous crystallized glass of the present invention, the porous crystal has a high mechanical strength and has a three-dimensional network structure in which new bone is likely to grow and penetrate. It is possible to make fog glass.

Claims (1)

[Claims] 1. SiO ₂ 22 to 50% by weight,
_{P 2 O 5 8~30%, CaO} 20~53%, MgO
1-16%, F ₂ 0.1-2%, Al ₂ O ₃ 0-9%,
The glass powder having a B ₂ O ₃ 0~5% of the composition, an organic solvent, is mixed with a binder to the slurry, the slurry is impregnated into an organic porous body having a three-dimensional network structure, dried, heat-treated A method for producing a porous crystallized glass, which comprises burning and removing the organic porous material and the binder, and sintering and crystallizing the glass powder.