JPH0611663B2 - Calcium phosphate-based sintered body for living body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a calcium phosphate-based crystal sintered body which is most suitable as a medical material such as a dental material or an artificial bone material.

[Conventional technology]

In recent years, the range of applications of ceramics has been remarkably expanded to the medical field, and it has been attempted to apply ceramics to medical materials such as those in which metal and plastic have been mainly used in the past, such as artificial dental roots. .

Various bioceramics such as alumina and carbon have been announced, but calcium phosphate-based materials are attracting attention because they are superior in terms of biocompatibility.

[Problems to be solved by the invention]

Generally, among calcium phosphate-based materials, hydroxyapatite, tricalcium phosphate and the like are manufactured by a method in which a powdery crystal body is pressure-molded and then sintered at a high temperature.

When only powders such as hydroxyapatite and tricalcium phosphate are sintered, it is necessary to sinter at a considerably high temperature in order to obtain a product with a high degree of sintering before obtaining high strength. However, when heat-treated at a high temperature, grain growth occurs simultaneously with sintering and the size of crystallites becomes coarse, and in the case of hydroxyapatite, it dehydrates to tricalcium phosphate. In that case, there is a drawback that the crystal is transformed from β type to α type, resulting in a sintered body having inferior physical properties.

Therefore, in order to manufacture a high-strength sintered body at a low temperature, it is necessary to use a complicated manufacturing means such as a hot press or a hot isostatic press, and it is unavoidable that the product becomes expensive.

[Means for solving problems]

In the present invention, during the sintering of calcium phosphate-based materials such as hydroxyapatite and tricalcium phosphate,
By adding calcium phosphate-based glass or calcium phosphate-based crystallized glass containing a rare earth oxide as a sintering aid, a sintered body of a calcium phosphate-based crystal material such as high-density and high-strength hydroxyapatite or tricalcium phosphate. Is easily obtained by sintering under normal atmospheric pressure.

[Action]

The rare earth-containing calcium phosphate-based glass or calcium phosphate-based crystallized glass added in the present invention has a lower melting point than hydroxyapatite or tricalcium phosphate. Therefore, hydroxyapatite or tricalcium phosphate itself melts at a temperature much lower than that which sinters to form a direct bond, resulting in a low-viscosity melt that penetrates between the particles of hydroxyapatite or tricalcium phosphate. Produces a strong bond. Therefore, hydroxyapatite and tricalcium phosphate can be densely sintered at a low temperature, and the grain growth thereof can be suppressed.

In the present invention, the rare earth oxide is contained in the calcium phosphate-based glass or the calcium phosphate-based crystallized glass which is the sintering aid, and the rare earth oxide improves the wettability with hydroxyapatite and calcium phosphate, and thus the calcium phosphate-based glass. Promotes the function of glass or calcium phosphate-based crystallized glass as a sintering aid.

Furthermore, this rare earth oxide suppresses the grain growth of hydroxyapatite and tricalcium phosphate and acts to improve the strength of the sintered body, and at the same time, a sintering aid that eventually becomes calcium phosphate-based crystallized glass. It also prevents grain growth of the crystal nucleating agent and the calcium phosphate crystal during crystallization, and also helps to improve the strength of the bond.

As described above, the rare earth-containing calcium phosphate-based glass or the calcium phosphate-based crystallized glass in the present invention enhances the degree of sintering of the obtained sintered body, and the size of the crystal particles hardly increases. If the raw material is made of very fine crystal particles such as synthesized hydroxyapatite and tricalcium phosphate, it is possible to obtain high-strength hydroxyapatite ceramics and tricalcium phosphate that are dense and composed of fine crystal particles. It becomes possible to inexpensively manufacture ceramics and the like on an industrial scale.

[Structure of Invention]

The starting material for the rare earth-containing calcium phosphate-based glass or calcium phosphate-based crystallized glass that serves as a sintering aid for the sintered body of the present invention is calcium oxide or calcium hydroxide that produces CaO by firing such as calcium hydroxide, calcium carbonate and calcium oxalate. A compound and a phosphorus-containing compound, such as phosphorus or polyphosphoric acid, which similarly produces an oxide of phosphorus by firing are used. Further, calcium phosphate, apatites, etc., or calcium phosphate scraps used for other purposes can also be used.

On the other hand, as the rare earth, in addition to oxides, compounds such as carbonates, hydroxides and nitrates, which also become oxides by firing, are used. The rare earths may be used alone or as a mixture of two or more, and it is preferable that yttrium, lanthanum and cerium are contained therein.

One or more of each of the calcium-containing compound, phosphorus-containing compound and rare earth compound is selected so that the composition of calcium / phosphorus base paper ratio Ca / P is in the range of 0.35 to 1.7, and the rare earth compound is calcium phosphate.
Adjust to 0.05 to 10 parts by weight in terms of oxide based on 100 parts by weight.

When this atomic ratio Ca / P is 1.7 or more, the melting temperature becomes high and the glass does not vitrify. On the contrary, when the atomic ratio is 0.35, the melting temperature is lowered and the vitrification is facilitated at the same time, but the crystallization treatment is difficult, and excessive phosphoric acid is liberated to be chemically unstable, which is not preferable. Further, if the content of the rare earth oxide is less than 0.05 parts by weight, the effect of addition is poor, and if it is 10 parts by weight or more, the effect does not increase relative to the amount added, and the melting temperature rises, which is not preferable.

The ingredients are weighed and mixed well, then put in a container and kept at 900 ° C or higher.
It is preferably heated to 1000 to 1600 ° C to melt. Melting 17
It is necessary to be careful because vaporization of phosphorus components starts at temperatures above 00 ° C.

After melting, it is cooled and vitrified. This glass can be used as it is as a sintering aid, or a material obtained by subjecting this glassy material to a crystallized vitreous material by appropriate heat treatment can also be used as a sintering aid. Crystallization of glass is carried out in a suitable heating device such as an electric furnace at a temperature below the melting point, preferably at 600 to 1000 ° C.

Next, a method for manufacturing a sintered body will be described.

As the calcium phosphate-based crystal that is a raw material of the sintered body, a crystal having a high melting point such as hydroxyapatite or tricalcium phosphate is suitable. The production method is not particularly limited, but those synthesized by the precipitation method have fine particles and are particularly preferred.

To 100 parts by weight of the crystallized product, 0.1 to 25 parts by weight of the above-mentioned calcium phosphate-based glass or calcium phosphate-based crystallized glass finely pulverized product is added. If the amount added is less than 0.1 parts by weight, it is not expected that a sintering-based factory will be added.If the amount added is more than 25 parts by weight, the properties of the bonding part will appear too strongly in the properties of the sintered body, such as hydroxyapatite and tricalcium phosphate. The characteristics of can not be exhibited.

Water or dextrin, CMC or PVA in the above mixture
A molding auxiliary solution such as the above is added, and the mixture is thoroughly kneaded and then molded. As this molding method, a general molding method at ordinary temperature such as compression molding or rubber press which is usually performed is used, and a special high temperature method such as hot pressing is not required.

Then, the molded body is heated in a suitable baking apparatus such as an electric furnace at 900
The sintered body of the present invention is obtained by firing at -1500 ° C for 0-5 hours.

〔Example〕

Example 1 Calcium carbonate powder and orthophosphoric acid, which were weighed so that the atomic ratio Ca / P of phosphorus to Ca was 0.55, were converted to calcium phosphate and 100 parts by weight of yttrium nitrate was converted to Y ₂ O ₃ to obtain 5 parts. It was weighed and added so as to be in parts by weight, thoroughly kneaded, melted at 1300 ° C. for 1 hr, and rapidly cooled to vitrify.

Next, 5 parts by weight of the yttrium-containing calcium phosphate-based glass was added to 100 parts by weight of tricalcium phosphate having an average particle size of 0.5 μm obtained by the precipitation method, and well mixed by the wet method. This was dried at 110 ° C. for 3 hours, molded into a cylinder of 30φ × 80 mm at a pressure of 1500 kg / cm ² using a rubber press, and then fired and sintered at 1300 ° C. for 1 hour.

The obtained sintered body is very dense with a sintering degree of 99.8%,
The three-point bending strength showed an extremely high value of 255 MPa. When the structure of the fracture surface was observed by SEM, it was 1 μm.
It was found that the particles were composed of fine particles of m or less, and the growth of the particles was well suppressed.

Comparative Example 1 Only the same tricalcium phosphate particles as in Example 1 were molded into the same shape as in Example 1 at a pressure of 2000 kg / cm ² using a rubber press, and were fired and sintered at 1450 ° C. for 3 hours.

The obtained sintered body had a degree of sintering of only 94% and had a structure in which pores remained considerably. Its 3-point bending strength is only 86M
Pa was lower than that of Example 1, and the presence of coarse particles and pores of 10 to 15 μm was observed by SEM observation.
It is considered that this resulted in a decrease in strength.

Comparative Example 2 According to Example 1, the atomic ratio Ca of calcium to phosphorus Ca
A calcium phosphate glass containing no yttrium compound having a / P of 0.55 was prepared.

Next, as in Example 1, with respect to 100 parts by weight of the tricalcium phosphate particles, 5 parts by weight of the calcium phosphate glass and 0.25 part by weight of yttrium nitrate converted to Y ₂ O ₃ were added and mixed well by a wet method. . After drying this at 110 ° C. for 3 hours, a rubber press was used and a pressure of 2000 kg / cm ³ was applied to Example 1.
Was molded into the same shape as above, and was fired and sintered at 1450 ° C. for 3 hours.

The obtained sintered body has a sintering degree of 96% and its three-point bending strength is 10%.
It was 0 MPa. Regarding the distribution of yttrium atoms by EPMA, in the case of Example 1, the yttrium atoms are uniformly distributed in the grain boundaries of the tricalcium phosphate particles, whereas in this example, the aggregate of yttrium atoms is distributed over the entire sample. It was found that they were present and dispersed as yttrium oxide particles. SEM observation also showed coarse grains with grain growth of 10 to 15 μm, both of which were considered to be the cause of strength reduction.

Comparative Example 3 A sample was obtained in the same manner as in Comparative Example 2 except that 5 parts by weight of calcium phosphate glass and 1.9 parts by weight of yttrium nitrate converted to Y ₂ O ₃ were added to 100 parts by weight of tricalcium phosphate particles. It was The obtained sintered body had a sintering degree of 97% and a three-point bending strength of 145 MPa. The distribution of yttrium atoms by EPMA was almost the same as in Comparative Example 2.
It can be seen that even if the amount of yttrium oxide used is increased, the strength of the sintered body cannot be obtained due to the difference in the distribution state of yttrium atoms.

〔The invention's effect〕

As seen in the examples, the calcium phosphate sinter of the present invention uses a calcium phosphate-based glass or a calcium phosphate-based crystallized glass containing a rare earth as a sintering aid, even at a low molding pressure and a low sintering temperature, It is possible to obtain a dense and high-strength sintered body having a higher degree of sintering, and the grain growth is suppressed due to the low temperature during sintering, which is also the reason why high strength can be obtained. .

 ─────────────────────────────────────────────────── ─── Continuation of front page Examiner Takeshi Yoneda (56) References JP-A-55-80771 (JP, A)

Claims (1)

[Claims] 1. A rare earth oxide is added to 100 parts by weight of a calcium phosphate composition having a calcium to phosphorus atomic ratio Ca / P of 0.35 to 1.7 in a calcium phosphate-based sintered body.
~ 10 parts by weight of calcium phosphate-based glass or calcium phosphate-based crystallized glass as a sintering aid, 0.1 to 25 parts by weight of calcium phosphate-based crystal 100 parts by weight and heated and sintered, the sintered body Is a calcium phosphate-based sintered body for living body characterized by having a structure in which a rare earth oxide is present at a grain boundary of a calcium phosphate-based crystal.