FI91712C - Bioactive glass composite and calcium phosphate ceramic and its method of preparation - Google Patents

Description

91712 COMPOSITE OF BIOACTIVE GLASS AND CALCIUM PHOSPHATE CERAMIC AND PROCEDURE FOR ITS MANUFACTURE

The invention relates to a composite of bioactive glass and calcium phosphate ceramic for use, for example, for medical purposes, to a method of manufacturing the composite and to an implant containing the composite.

The components of glass-calcium phosphate ceramic composites are bioactive glasses and calcium phosphate ceramics with different solubilities. The aim is to obtain the desired biological properties of the composites and to make their solubility properties desirable. Such materials are used as bone filler materials, joint implants, and subcutaneous drug implants.

At present, there are three types of artificial bone substitute material: 15 - tissue-unreactive e.g. titanium metal, alumina ceramic.

surface reactive, bioactive or soluble, such as calcium ceramics, surface reactants or bioactive glasses and glass ceramics.

- ·· 20 - composites made from materials of the foregoing group and from other non-bioactive materials, such as metals, ceramics, polymers and organic materials.

A major advantage of bioactive materials is their ability to rea-. Implanted in bone tissue such that the bone biochemically, chemically and mechanically associates with the surface of the implant. Due to this reaction, bioactive implants heal faster after surgery and have a higher binding strength to bone tissue. The ability of these materials to adhere to bone is due to the similarity of their composition to the mineral part of the bone or their ability to form a coating having a bone mineral composition when implanted in the surface itself in bone tissue. A group of materials similar to the bone mineral moiety are calcium phosphate ceramics. The best known of these is hydroxyl-5 apatite, a synthetic form of bone mineral. With bioactive glasses and glass-ceramics, the composition of the glass and its solubility determine the outcome of the reactions in the bone tissue.

Although the mechanism for forming the calcium phosphate layer on the surface of the glass 10 has not been fully elucidated, the following conclusions can be drawn: 1) The composition of the glass must be such that a silicon layer forms on the glass surface in aqueous solution or tissue fluid.

2) The concentration of (Ca11) and (Pv) ions in the vicinity of the glass surface has an effect on the rate of formation of the calcium phosphate layer and thus on the bioactivity. Therefore, CaO and P 2 O 5 are the desired additives in the glass composition.

20 3) If too many other silicon substitute oxides are added to the glass, the glass becomes too soluble and is unable to form a circuit or a layer of calcium phosphate on its surface.

:. 4) If there are not enough additives, the solubility is too low and the circuit layer is not formed at all or is not transparent enough to combine with calcium phosphate compounds.

5) The glass composition must be limited within certain composition limits in order to be bioactive. Within these composition limits, optimized glass compositions with maximized bioactive properties can be determined.

6) The maximization of the bioactivity of pure glasses is thus limited by achieving on the one hand the dissolution rate and on the other hand the maximization of the concentration of calcium phosphate ions.

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The main weakness of bioactive materials is their low mechanical strength. Therefore, they cannot be used as massive bodies for purposes where they are subjected to continuous or intermittent stress. Therefore, efforts have been made to combine bioactive materials with other materials to provide the necessary strength and bioactivity at the same time.

There are mainly two approaches to this purpose: 1. Coating with a bioactive material or 10 2. Adding a reinforcing phase to the bioactive material.

There have been weaknesses in both approaches. As coatings, bioactive materials are completely soluble, such as hydroxylapatite, or their bioactive properties have not otherwise been satisfactory. On the other hand, the addition of a reinforcing phase has in almost all cases resulted in a decrease in bioactivity compared to pure bioactive material. These setbacks have led to a decrease in the reliability of composite materials. In theory, bioactivity can be enhanced by increasing the concentration of calcium phosphate ions in the vicinity of the glass with maximum bioactivity.

The object of the present invention is to provide a new composite and a method for manufacturing it in a new way.

The composite according to the invention is characterized in that the glass phase of the composite consists of the following components, the weight percentages of which are indicated in parentheses for the substances:

SiO 2 (35-60% by weight) -Na 2 O (15-35% by weight) -CaO (0-40% by weight) -P 2 O 5 (0-15% by weight) -B 2 O 3 (2-5% by weight) - Al 2 O 3 30 (0-1.5% by weight).

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According to the invention, the process for the preparation of the composite is characterized in that the composite is prepared from its starting materials, bioactive glass and calcium phosphate-ceramic, so that a dense composite is formed by firing at a temperature below 680 ° C without substantially reacting between the starting phases. The method makes it possible to produce composites of calcium phosphate tiger ceramic and bioactive glass formations with maximum bioactivity and controlled solubility properties.

Previous attempts to produce such composites have failed because the glasses have reacted with the calcium phosphate tiger ceramic phase, thus destroying the composite system. The failures are due to the fact that at temperatures above 700 ° C Na ions diffuse into the Ca, F phase. In this case, the Ca, P phase undergoes a phase change at the same time as the glass becomes circular and often also crystallizes. Therefore, firing the glass-ceramic mixture at a temperature above 700 ° C does not give the desired result.

U.S. Patent 4,708,652 discloses a solution for preventing an adverse reaction. The solution is based on the stabilizing effect of the second reaction. The end result cannot be changed other than by changing the phase relationships. The patent · claims that hydroxylapatite is destroyed at 400-500 ° C

At 25 with glass (SiO 2 -CaO-P 2 O 5 -Na 2 O).

In the production process according to the invention, the Nations of the glass phase do not react with the Ca, P-ceramic particles thermally. at a temperature below 680 ° C. Also essential to the invention is the correct glass phase composition to produce a dense material by firing the glass-ceramic mixture.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which li 91712 5

Figure 1 is a block diagram of an example of the manufacture of bioactive glass.

Figure 2 is a block diagram of an example of the preparation of calcium phosphate ceramic.

Figure 3 is a block diagram of an example of a composite fabrication.

Figure 4 shows in cross-section an example of a composite made by the method according to the invention.

Figure 1 is a block diagram of an application example of a method of manufacturing a first component of a composite according to the invention, i.e. bioactive glass. Reference numeral 10 denotes the mixing step of the raw materials. In this case, the following essential ingredients are mixed in the raw material composition of the glass phase of the composite:

SiO 2 is a basic glass building material which, when modified with other ingredients, enables the above-mentioned bioactive and dissolution properties. The silicon content of the glass can be varied from 35 to 60% by weight.

Na 2 O By adding sodium, the melting temperature of the glass can be lowered so that the firing of the glass-ceramic mixture is possible at a temperature below 680 ° C. Sodium also increases the solubility of glass and its bioactivity. The sodium content of the glass can be varied from 0 to 35% by weight.

CaO also affects the solubility of glass, but is: only important as an enhancer of bioactivity. The CaO content can be varied from 0 to 40% by weight.

P205 is also an essential ingredient for bioactivity. Like sodium and calcium, phosphorus can be left alone in glass poirs, but 91712 6 their addition achieves maximum bioactivity in glass.

B203 Essential component for the firing of glass-ceramic alloys. An addition of 2% is sufficient to obtain a final tightness of the material of more than 95%. Without boron, only about 10% Ca, P-ceramic particles can be incorporated into the composite without the density dropping below 95%.

Al203 Has a positive effect on the combustion properties of glass 10 and limits its solubility. On the other hand, a concentration of more than 1.5% destroys the bioactive properties of glass. Therefore, the aluminum content of the glass must be kept below one and a half percent by weight.

In the application example of Fig. 1, the glass phase melting step denoted by reference numeral 11 has a duration of three hours at 1300 ° C. SiO2, CaCO3, Na2CO3, CaHPO4 »2H2O, BH3O3 and Al2O3 are used as pure starting materials. The molten glass is cooled in step 12 to e.g. deionized water, followed by rinsing the cullet with 100% ethanol in step 13 and grinding in step 14. The particle size of the resulting bioactive glass powder 15 is most preferably less than 10 μιη.

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The application example of Figure 2 shows a block diagram of the preparation of the calcium phosphate ceramic phase. The Ca, P-cera-25 miphase (20) is, for example, hydroxylapatite

Ca10 (PO4) 6 (OH) 2, fluorapatite, oxyapatite, rhenanite CaNaPO4, tricalcium phosphate Ca3PO4, tetracalcium phosphate. or other collections belonging to the same group. Reference numeral 20 denotes a mixture of raw materials 30 for the ceramic phase of the composite. For example, the following ingredients are essential in the composition of rhenanite:

Pure CaHPO 4 and Na 2 CO 3 powders are mixed in the correct molar ratios according to the formula tl 91712 7 2CaHPO 4 + Na 2 CO 3 -> 2 CaNaPO 4 + CO 2 + H 2 O.

This is followed by a first pressing step 21 in the ceramic phase manufacturing process, in which the mixed powders 5 are pressed uniaxially at a pressure of 100 MPa. In the first firing step 22, the compressed material is fired at 1100 ° C under normal atmospheric pressure for three hours. In the first grinding step 23, the burned material is ground from the surface, and in the first crushing step 24, the material 10 is crushed so that the particle size of the particles is less than 45 μπι.

This is followed by a second pressing step 21 followed by a second firing step 22, a grinding step 23 and a crushing step 24. The same is repeated a third time 15 times, but now the third firing step 22 takes place at 1300 ° C for 16 hours. The subsequent grinding step 23 and crushing step 24 are similar to the above. Finally, in the grinding step 25, the ceramic material is ground to a Ca, P-ceramic powder 26 with a particle size of less than 20 10 μπι. Essential to the manufacture of ceramics is that the ceramic is fired tightly and crushed.

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Figure 3 is a block diagram of an application example of a composite manufacturing process. In the example shown, the glass and ceramic powders are mixed in a mixing step 30 25 so that 7 pairs of bioactive glass powder 15 and 3 parts by weight of Ca, P-ceramic powder 26 are taken.

V In the compression step 31, the mixed powders are compressed uniaxially at a pressure of 100 MPa without binders or other additives. -The compressed pills are fired in combustion step 30 32 in air at 600-650 ° C for 60 minutes. The resulting material is allowed to slowly cool in an oven to room temperature in the cooling step 33. The final product is a glass-calcium phosphate ceramic composite 34.

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Figure 4 shows in cross-section an example of a material made by the above-mentioned method. The density of the material is 96%. X-ray diffraction and scanning electron microscopy analyzes showed no significant reactions between the glass phase (40) and the calcium phosphate ceramic particle (41).

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Claims (5)

A composite (34) consisting of bioactive glass (15) and calcium phosphate ceramic (26), which is intended for use, for example, for medical purposes, in which the starting materials of the composite (34), the bioactive glass (15) and the calcium phosphate ceramic ( 26), form a dense composite without the starting phases (15, 26) reacting substantially with each other, and in the bioactive glass matrix of the composite, calcium phosphate ceramic particles are characterized in that the glass phase (10) of the composite (34) is composed of the following constituents. , whose amounts in weight percentages have been stated in connection with the substances in brackets: SiO 2 (35-60 wt%) -Na 2 O (15-35 wt%) -CaO (0-40 wt%) -P 2 Os (0-15 and that the calcium phosphate ceramic (26) of the composite (34) has been densified by firing and comminuted prior to mixing with the bioactive glass (wt%) -B2 O3 (2-5 wt%) (15). Composite according to claim 1, characterized in that the Ca, β-ceramic phase (20) of the composite (34) is hydroxyl apatite Ca10 (POA) 6 (OH) 2, fluorapatite, oxyapatite, rhenanite CaNaPO *, tricalcium phosphate Ca3 PO4, tetracalcate or tetracalcate something else ceramic that belongs to the same group. A process for making a composite (34) according to claims 1 or 2, characterized in that the composite (34) is made of its starting materials, the bioactive glass (15) and the calcium phosphate ceramic (26), in particular. a dense composite is formed by firing at a temperature below 680 ° C without the starting phases (15, 26) substantially reacting with each other. 30 Process for the preparation of a composite according to claim 3, characterized in that bioactive, surface-reactive SiO 2 (35-60 wt%) -Na20 91712 (15-35 wt%) -CaO (0-40 wt%) -P2O5 (0-15% by weight) -B2 O3 (2-5% by weight) -Al2O3 (0-1.5% by weight) glass powder (15) and Ca, P ceramic powder (26) are mixed, pressed and burned at a temperature below 680 ° C at any pressure, without the starting substances reacting substantially with each other. Implant consisting of a composite (34) consisting of bioactive glass and calcium phosphate ceramics, and optionally a substrate characterized in that the composite (34) is a composite according to claim 1 and that the implant - is manufactured in granular form, or - is a metal, polymer or ceramic substrate coated with the composite (34), or - consists of a particle or powder form mixture which is the composite (34) and another material such as ceramic, metal or polymer, or - is completely soluble. «» · «F