JPH0627025B2 - Hydroxyapatite filter cake dried product - Google Patents

Description

Detailed Description of the Invention

The present invention relates to a dried hydroxyapatite filter cake dried product. More specifically, the present invention relates to a dried hydroxyapatite filter cake that can be baked to obtain a white or translucent hydroxyapatite porcelain having high density, high purity and excellent thermal stability.

Hydroxyapatite is Ca ₁₀ (P
O ₄ ) ₆ (OH) ₂ or Ca ₅ (PO ₄ ) ₃ (OH) is one of the inorganic constituent components such as bone and teeth which are hard tissues of living body. A sintered body of synthetic hydroxyapatite (hereinafter referred to as hydroxyapatite porcelain) has been published as being usable as an implant material such as artificial tooth root or artificial bone that closely resembles a living body [eg, Aoki,
Kato, Ceramics, 10 (7), 469 (1975)], has recently received much attention.

When used in a living body, it is preferable that the synthesized hydroxyapatite porcelain has physical properties similar to those of a hydroxyapatite sintered body produced in a living body.
That is, the hydroxyapatite porcelain for such living body applications is required to have no coloration, high density, high purity, and safe for living body.

Here, the safety-related purity means physicochemical purity. That is, the purity does not include elements other than the essential constituent elements Ca, P, O and H of hydroxyapatite as much as possible, the constituent element ratio Ca / P is close to the theoretical value 1.67 of hydroxyapatite, and the physical structure is hydroxyapatite. It is decided by the fact that it is close to the structure of.

Of these, the defects in the physical structure are detected by X-ray diffraction of the porcelain itself, but even if the latent defects cannot be detected, they become clear after the sample is further treated at a high temperature of about 1350 ° C. May be detected. Witlock stones, which have a low element ratio Ca / P and a high solubility in the physical structure, unlike hydroxyapatite, are likely to be contained as impurities.

In any case, when these impurities are contained or there is a structural defect, the porcelain is colored or is eluted into the living body during use. This elution may promote the replacement with the biological tissue, but the elution may locally impair the electrolyte balance and may adversely affect the living body in terms of safety due to harmful effects of the eluate itself.

Therefore, it is strongly desired that the hydroxyapatite porcelain is colorless, has a high density and high purity, and it is extremely important to provide an industrial production method thereof. However, as shown below, the present situation is that hydroxyapatite porcelain which meets these requirements has not yet been obtained.

Several methods of synthesizing hydroxyapatite have been proposed so far. For example, RW Mooney et al.
Chem. Rev., 61, 433 (1961), Kanazawa et al., Area of Chemistry, 27,
622 (1973) and so on. However, there have been few studies on a method for producing a hydroxyapatite porcelain obtained by firing the hydroxyapatite. Among them, Monreo reported that a powder of synthetic hydroxyapatite was compression-molded and then fired at a temperature of 1300 ° C under normal pressure to obtain hydroxyapatite porcelain [J. Dent. Res., 50 860 (197
1)]. However, the hydroxyapatite porcelain is 30%
It also contains witlock stone (α-calcium triphosphate), and it is hard to say that it is a high-purity hydroxyapatite porcelain.
The reason why a high-purity hydroxyapatite porcelain cannot be obtained is that the hydroxyapatite used does not have a stoichiometric composition or has a structural defect. Probably a by-product.

Attempts have also been made to synthesize hydroxyapatite having a stoichiometric composition and then calcinate the hydroxyapatite. However, the hydroxyapatite obtained by the conventional synthesis method is poor in sinterability and thermal stability due to the problem of purity or its own crystal structure and crystal grain morphology, and is therefore thermally stable and high in density and high in density. We haven't reached the point where we obtain pure porcelain. For example, JP-A-52-64199
Proposes to add a heterogeneous metal compound such as MgO in order to improve the sinterability of the hydroxyapatite porcelain precursor having a stoichiometric composition obtained by a conventional synthesis method. However, the above method is based on the positive introduction of a different element to improve the sinterability, and has a different concept from the present invention as described later.

On the other hand, the method for synthesizing hydroxyapatite proposed by M. Jarcho utilizes the following reaction.

5Ca (NO ₃ ) ₂ +3 (NH ₄ ) ₂ HPO ₄ + 4NH ₃ + H ₂ O → Ca ₅ (OH) (PO ₄ ) ₃ + 10NH ₄ NO ₃ That is, pH of the reaction system is 10 to 12 with ammonia. The hydroxyapatite is synthesized by the method of reacting calcium nitrate and diammonium hydrogen phosphate while adjusting to 1, and further the filter cake of the hydroxyapatite is 1100 to 1200.
Average crystal size of about 0.2-3 μm after firing at a temperature of ℃,
It has been reported that hydroxyapatite porcelain having a density of 3.10 to 3.14 g / cm ³ is obtained [JP-A-51-40400, JP-A-52-94309; J. Material Sci., 11, 2027 (1976)]. . However, the document discloses that the hydroxyapatite porcelain is partially decomposed to produce witlock stone as a by-product when fired at 1250 ° C. or higher for 1 hour or longer. That is, the hydroxyapatite porcelain obtained by the method still contains structurally unstable elements, essentially has structural defects, and has poor thermal stability. Further, this method has a drawback that ammonium nitrate is produced as a by-product.

Further, as another method for synthesizing hydroxyapatite, the following reaction of calcium hydroxide and phosphoric acid: 5Ca (OH) ₂ + 3H ₃ PO ₄ → Ca ₅ (PO ₄ ) ₃
A synthesis method using (OH) + 9H ₂ O has also been proposed. The reaction is (1)
Since the starting material does not contain foreign elements and (2) the reaction by-product is only water, it is expected to be applied to the industrial production method of hydroxyapatite having a stoichiometric composition. But Samurai et al., Mooney [Chem. Rev., 61, 433 (1
961)], it is difficult to obtain hydroxyapatite having a stoichiometric composition (Ca / P theoretical value = 1.67) in the reaction, and hydroxyapatite having an element ratio Ca / P = 1.50 (corresponding to calcium triphosphate). Pointed out that it is only obtained.

On the other hand, R. Wallaeys [Ann. Chim. (Paris)
, 7, 808 (1952)] is a method such as boiling after completion of the reaction in order to completely advance the reaction, or advancing the reaction to the neutralization point of phenolphthalene in the boiling state by Ca / P =
We have obtained 1.61 to 1.67 hydroxyapatite. However, as a result of re-testing the method of Wallaeys, the dried product of the hydroxyapatite filter cake obtained by this method is inferior in sinterability, and therefore 3.11 g can be obtained even by the hot pressing method in which direct pressure is applied at high temperature for firing. Only porcelain with a density of about / cm ³ can be obtained, and it is colored (blue) during sintering
It was something to do. Although the cause of coloring is not clear, structural defects as porcelain may be considered in addition to the presence of trace impurities. Therefore, it became clear that the method of Wallaeys cannot achieve the object of the present invention.

As described above, the known hydroxyapatite porcelain contains different elements in order to improve the sinterability of the synthetic hydroxyapatite, has a structural defect with poor thermal stability, Further, there is a problem in characteristics or structure such as coloring during sintering. In other words, the present situation is that hydroxyapatite porcelain which solves the above problems and is suitable for application to a living body, has high purity, high density, and is excellent in thermal stability has not yet been completed.

In view of such circumstances, the inventors of the present invention have earnestly studied the relationship between the sinterability or thermal stability and the crystal form, structure, etc. of synthetic hydroxyapatite, and as a result, the stoichiometric composition having specific properties has been obtained. Synthetic hydroxyapatite filter cake dried product has high purity, high strength and no structural defects, and is heat-stable without decomposing and producing witlockite even if it is baked at 1350 ° C for 1 hour. The inventors have found that a colorless porcelain having excellent properties can be obtained, and arrived at the present invention.

That is, according to the present invention, hydroxyapatite is prepared by reacting an emulsion of fine particulate calcium hydroxide obtained by reacting porous fine-grained calcium oxide with an excess of water and an aqueous phosphoric acid solution in an inert atmosphere. To get
The uncalcined hydroxyapatite thus obtained has the following characteristics: ・ Ca / P analysis value = 1.67 to 1.69 ・ Average size Length = 187 to 1200 angstrom Width = 50 to 320 angstrom Length / width = 3.75 to 10 is doing.

When the suspended reaction solution containing the hydroxyapatite is filtered, washed with water and dried, the following characteristics are obtained: void volume = 0.2 to 0.8 cm ³ / g average pore radius between crystals = 50 to 150 A dried hydroxyapatite filter cake having an angstrom is obtained.

When the above-mentioned dried hydroxyapatite filter cake is calcined, the element ratio Ca / P = 1.67 to 1.69, the average crystal size of the cross section = 4 to 20 μm, and the density = 3.14 to 3.16 g / cm ^3. A hydroxyapatite porcelain is obtained. Since the obtained porcelain has a larger crystal size than the conventional synthetic hydroxyapatite porcelain, it is clear that it is a porcelain obtained from a crystallographically highly pure raw material. . Further, the dried filter cake, which is an aggregate of hydroxyapatite, is heated to 1350 ° C. for 1 hour.
Since no witlock stones formed by the decomposition of hydroxyapatite are observed even after calcination for a long time, it is clear that the composition does not retain a component that induces a decomposition reaction and that it has excellent thermal stability.

The present invention will be described in detail below.

The dried hydroxyapatite filter cake of the present invention is (a) converted into calcium oxide by thermally decomposing high-purity powdery calcium carbonate at 800 to 1300 ° C. for 0.5 to 10 hours in an inert atmosphere, b) cooling the high temperature calcium oxide to at least 500 ° C. under an inert atmosphere,
(c) Subsequently, the cooled calcium oxide and water are reacted while being stirred at high speed to convert into calcium hydroxide, and (d) the milky liquid suspension of the calcium hydroxide and the phosphoric acid aqueous solution under an inert atmosphere, It is obtained by reacting at a temperature of 0 to 50 ° C. under a high-speed stirring condition, separating by filtration and drying.

The porous fine-grained calcium oxide according to the present invention is obtained by thermally decomposing powdery calcium carbonate. It is preferable that the raw material calcium carbonate has a high purity of 99.8% or more and is fine. Pyrolysis conditions are an inert atmosphere, a temperature of 800 to 1300 ° C., preferably 950 to 1200 ° C., and a time of 0.5 to 10 hours, preferably 1 to 5 hours. Calcium carbonate desorbs carbon dioxide gas by thermal decomposition under the conditions, and is converted into a highly porous and highly reactive calcium oxide fine powder. At this time, if the pyrolysis conditions are mild, undecomposed calcium carbonate is mixed in the produced calcium oxide. The calcium carbonate thus mixed is not preferable because it is difficult to remove, and it also contributes to the structural defect of the final product hydroxyapatite porcelain and the decrease in thermal stability. On the other hand, if the thermal decomposition conditions are too strong, the surface of the calcium carbonate will melt and the thermal decomposition will be insufficient, and the calcium hydroxide emulsion forming reaction will be delayed. Further, the cooling after the thermal decomposition should be performed in an inert atmosphere up to a temperature of at least 500 ° C., preferably 200 ° C., in order to prevent the formation of calcium carbonate by carbon dioxide gas in the air.

The inert atmosphere means an atmosphere containing no components that induce a secondary reaction with calcium oxide or calcium hydroxide produced like carbon dioxide and ammonia.

By blowing an inert gas such as nitrogen, helium or argon into the thermal decomposition reaction system to obtain the inert atmosphere, the carbon dioxide gas generated can be effectively and sequentially removed.

The particulate calcium hydroxide emulsion according to the present invention can be produced by adding the above calcium oxide to a large amount of water under high speed stirring under the above-mentioned inert atmosphere. The amount of water per 1 part by weight of calcium oxide is not particularly limited, but is usually 10 to 100 parts by weight. The above reaction is preferably carried out at a low temperature for a long time under high speed stirring, and is usually 0 to 80 ° C, preferably 0 to 50 ° C, and 0.5
~ 96 hours, preferably 1 to 24 hours.

The termination of the reaction is determined by X-ray diffraction analysis. That is, a part of the reaction product is taken out, and the reaction is completed when the d ₂₀₀ of calcium oxide on the X-ray diffraction chart disappears.

The average particle size of calcium hydroxide in the emulsion of the present invention is 0.05 to 0.1 μm, and the average particle size obtained when ordinary commercial grade calcium hydroxide is dispersed in water is 1 to 10 μm. It is much finer.

The emulsion of calcium hydroxide in the form of fine particles is an important requirement for obtaining a good-sintering hydroxyapatite described later.

The hydroxyapatite of the present invention is in a suspended state by adding and reacting an aqueous phosphoric acid solution corresponding to Ca / P = 1.67 to 1.69 with the above-mentioned particulate calcium hydroxide emulsion in an inert atmosphere at a high speed with stirring. Is generated. In the production of the hydroxyapatite, it is preferred that after the emulsion forming reaction of calcium hydroxide is completed, the stirring is continued and the phosphoric acid aqueous solution is directly added into the system to cause the reaction. Phosphoric acid is usually prepared as an aqueous solution of 1 to 10 wt% and gradually added to the emulsion by a method such as dropping.

In the present specification, high speed stirring means that the liquid in the reaction system is in a turbulent state.

The reaction temperature is 0 to 50 ° C. If the reaction temperature is too low, the viscosity of the emulsion will increase, making it difficult to carry out a uniform reaction. On the contrary, if the reaction temperature is too high, the sinterability of the dried hydroxyapatite filter cake will be impaired. That is, the reaction temperature is a very important factor with respect to the crystal size involved in sinterability or the easy sedimentation described later. Reaction time is usually 0.5 to 20
0 hours, preferably 5 to 100 hours. In the reaction, the pH in the reaction system is 8 to 8 due to the initial high alkalinity (pH = about 13).
It drops to 9 and completes.

Although hydroxyapatite in the reaction system is in a suspended state, it has an excellent sedimentation property and can be easily separated by filtration. According to microscopic observation, the hydroxyapatite usually has a length of 187 to 1200 angstrom and a width of 50 to 320.
Angstrom, length / width = 3.75 to 10 average crystal size. Such a crystal size is clearly different from a conventionally known plate crystal having a length of 200 angstroms and a width of 200 angstroms, which is obtained by the reaction of calcium nitrate and diammonium hydrogen phosphate. The hydroxyapatite of the present invention is easy to settle because of such a crystal size,
It can be considered to be caused by the morphology and further the charge state of the crystal surface. It is also speculated that these factors contribute to the formation of the dried filter cake having good sinterability of the present invention.

The dried filter cake of the present invention can be obtained by subjecting the hydroxyapatite filter cake synthesized by the above-mentioned production method to ordinary drying.

The dried filter cake of the present invention has the following characteristics: Element ratio (Ca / P) = 1.67 to 1.69 Crystal size Length (L) = 187 to 1200 angstrom Width (W) = 50 to 320 angstrom L / W = 3.75 to 10, void volume = 0.2~0.8 cm ³ / g, having an average pore radius = 50 to 150 Å. The various properties affect the properties of the hydroxyapatite porcelain described below.

The dried filter cake according to the present invention has extremely good sinterability, and by firing as it is, a porcelain having excellent properties as described below can be obtained.

Of course, an ordinary method, for example, molding using a mold, rubber or the like, and then firing or directly applying pressure at high temperature and firing under reduced pressure can also be performed.

Further, the dried filter cake of the present invention may be pressure-molded and then fired under reduced pressure to obtain a porcelain having extremely high transparency, high density, high purity and excellent thermal stability. it can. The firing conditions are 850 to 1400 ° C, preferably
1250 to 1400 ° C, 0.5 to 5 hours, preferably 1 to 3 hours. Upon sintering, the hydroxyapatite crystals of the present invention grow large.

The hydroxyapatite porcelain obtained by firing the dried hydroxyapatite filter cake of the present invention has the following characteristics: Elemental analysis value Ca / P = 1.67 to 1.69 ・ Average crystal size = 4 to 20 μm ・ Density = 3.14 to 3.16 g / cm ³ · Thermal stability = No formation of witlockite even after firing at 1350 ° C for 1 hour.

While the known hydroxyapatite porcelain having the above-mentioned composition produces witlock stones when fired under severe conditions of 1200 ° C. or higher and 1300 ° C. or higher, it is obtained from the dried hydroxyapatite filter cake of the present invention. The obtained porcelain is extremely stable even at a temperature of 1300 ° C. or higher, and has a large crystal size, which is clearly distinguished from known hydroxyapatite porcelain.

Among the characteristics of the porcelain, the thermal stability is 1350.
It was confirmed by X-ray diffraction measurement of the porcelain obtained by firing at ℃ for 1 hour.

The porcelain obtained from the dried hydroxyapatite filter cake of the present invention can be inferred to have no structural defects in addition to the above characteristics, but is excellent in in vivo stability.

It is also possible to produce hydroxyapatite porcelain by continuously performing the drying step and the firing step on the undried hydroxyapatite filter cake obtained from the reaction solution.

As described above, according to the present invention, a stoichiometric hydroxyapatite excellent in sinterability can be easily obtained by reacting a specific calcium hydroxide and phosphoric acid under mild conditions. It is possible and the method of the present invention is extremely effective as an industrial production method. Moreover, since the hydroxyapatite porcelain obtained from the dried hydroxyapatite filter cake of the present invention has a very high purity in terms of chemical and physical structure, it is stable and safe for living organisms, and is an implant material for artificial dental roots and artificial bones. Is useful as

The hydroxyapatite porcelain material obtained by firing the dried hydroxyapatite filter cake of the present invention can be applied to a living body by the following method when it is actually applied as an implant material, especially an artificial tooth root material. That is, the implant denture method is a method in which an artificial tooth root is embedded in a jawbone or the like, and two or three months later, the denture is joined to the tooth root. In this case, it is necessary to promptly correct and remove the tooth root. In this case, if the adhesive force between the artificial tooth root and the natural bone such as the jawbone is too strong, it is necessary to take measures such as scraping the jawbone and removing the artificial tooth root, which may cause pain to the patient or cause the natural bone loss. You will be relieved.

An implant material is provided by combining the hydroxyapatite porcelain obtained from the dried hydroxyapatite filter cake of the present invention with an organic polymerizable binder or an organic binder.

Since the organic binder is embedded in the living body for a long period of time, it is required that the resin does not deteriorate and the living cells do not collapse. Polymerization of bisphenol A diglycidyl methacrylate, triethylene glycol dimethacrylate polymerization is required. Material, trifluoromethacrylate resin, silicone resin, polymethylmethacrylate, poly-2-hydroxyethylmethacrylate, polyethylene, polysulfone resin, polyamide resin, polyester resin, polytetrafluoride ethylene, polyvinylidene fluoride, polycarbonate resin A single type or a mixture of two or more types or a copolymer of two or more types of monomers constituting these polymers is preferable.

From the viewpoint of molding processability, ease of handling, mechanical strength, etc., the above-mentioned implant material is mixed with a hydroxyapatite porcelain having a particle diameter of 1000 μm or less, preferably 100 to 0.01 μm, and an organic binder, and then by a known method. It can be obtained by molding or impregnating the hydroxyapatite porcelain obtained from the dried hydroxyapatite filter cake of the present invention into a porous material and impregnating it with an organic binder, but the important point here is the portion that corresponds to the adhesive surface with bone. The area ratio of the hydroxyapatite porcelain phase to the binder phase is in the range of 5/95 to 70/30. When the surface occupying area ratio of the hydroxyapatite porcelain phase exceeds 70%, the bond with the natural bone becomes strong and the natural bone is lost during extraction. On the other hand, when the surface occupying area ratio of hydroxyapatite is less than 5%, it is excluded because it is not preferable. Considering durability and adhesiveness as an artificial tooth root, the surface area ratio is 10/90 to 60/40.
Is preferred.

In the present specification, the term "adequate adhesiveness" means that the adhesiveness is not eliminated after implantation, and the adhesive structure has sufficient adhesive strength for practical use after connecting the upper structure of the denture, and causes inconvenience. In the case of extraction, the extent to which natural bones are not broken or missing is specified.

In addition, a co-molded sintered body with an organic substance such as cellulose or collagen, a porous body by perforation, a composition in which a porous body is impregnated or polymerized with an organic resin, a composite of powdered porcelain and an organic or inorganic matrix Alternatively, it can be used as a biomaterial by combining them.

As described above, the hydroxyapatite and the aggregate thereof of the present invention can be used not only as a porcelain by firing but also as a chromatographic packing material.

The present invention will be described in detail below with reference to examples.

[0051]

EXAMPLES Example 1 600 g of calcium carbonate powder (manufactured by Kishida Chemical Co., Ltd., special grade reagent) was placed in an electric furnace under a nitrogen gas flow (1 l / min) atmosphere, and 1000 ° C. at a temperature rising rate of 3 ° C./min. The temperature was raised to the temperature of 1 and the mixture was pyrolyzed for 3 hours. Then, the mixture is cooled to 200 ° C. under a nitrogen gas flow (1 l / min) atmosphere and calcium oxide 335
g (yield 99.7%) was obtained. The obtained calcium oxide is X
It was confirmed by line diffraction that it did not contain calcium carbonate (99.8% purity by EDTA method). In addition, the microscopic observation of this calcium oxide showed that the raw calcium carbonate crystals remained in their original form and were porous.

6 l of degassed distilled water was placed in a 17 l three-neck enamel tank equipped with a stirrer, heater, controller and thermometer, and the atmosphere was replaced with nitrogen while stirring (350 rpm). 280 g (5
Mol) was gradually added over 10 minutes. After the addition, reaction was carried out in a nitrogen gas atmosphere at 50 ° C. for 5 hours and further at room temperature for 15 hours to obtain a fine calcium hydroxide emulsion having an average particle diameter of 0.075 μm.

Next, the calcium hydroxide emulsion is added to 3000 r
The mixture was stirred while maintaining a turbulent flow at pm, and a 3.5% phosphoric acid aqueous solution (3 mol) was gradually added to this liquid over 30 minutes. After the addition, the mixture was reacted at a temperature of 20 ° C for 48 hours. After the completion of the reaction, the obtained suspension was filtered with a pressure filter, washed with water and then washed with water.
It was dried at a temperature of ° C for 16 hours to obtain 497 g of dried hydroxyapatite filter cake (Sample No. -1). The dried filter cake had the properties shown in Table 1.

Example 2 Reaction conditions of calcium hydroxide and phosphoric acid aqueous solution (20 ° C.,
A dried hydroxyapatite filter cake (Sample No.-2) was obtained in the same manner as in Example 1 except that (48 hours) was 40 ° C. and 24 hours. The dried filter cake had the properties shown in Table 1.

Comparative Example 1 5 mol of calcium hydroxide powder as a special grade reagent was dispersed in 6 l of degassed distilled water to obtain a dispersion. This dispersion was placed in the enamel tank used in Example 1 and replaced with nitrogen.
With stirring at 3000 rpm, 3 mol of a 3.5% phosphoric acid aqueous solution was gradually added. Then, the mixture was reacted at 70 ° C. for 24 hours to obtain a dried filter cake (Sample No.-3) in the same manner as in Example 1. The dried filter cake had the properties shown in Table 1.

Comparative Example 2 The dried filter cake (Sample No. 4) obtained by a known method by the reaction of diammonium hydrogen phosphate and calcium nitrate had the properties shown in Table 1.

The reaction between diammonium hydrogen phosphate and calcium nitrate was as follows.

160 g of diammonium hydrogen phosphate was dissolved in 3 l of distilled water, and 1700 ml of 28% aqueous ammonia solution was added.
The pH was adjusted to 11-12. Further, distilled water was added to dissolve the precipitated diammonium hydrogen phosphate. Then add 1800 ml of distilled water adjusted to pH 12 with 60 ml of concentrated ammonia solution.
The above solution of diammonium hydrogen phosphate was added dropwise to a solution of 20 g of calcium nitrate dissolved at 20 ° C. under high speed stirring over 30 minutes, and then diluted with distilled water until the total amount became 7.0 l. Further, this diluted solution was boiled for 10 minutes and then left at room temperature for 20 hours. The produced gelatinous substance was separated by filtration using a Buchner funnel under a weak vacuum and washed with water, and when a crack was formed in the filter cake, the degree of vacuum was increased by using a rubber dam. After 2 hours, the rubber dam was removed to obtain a filter cake. The filter cake was dried at 150 ° C. for 15 hours to obtain 197 g of a dried filter cake.

Comparative Example 3 Reaction Conditions of Calcium Hydroxide and Phosphoric Acid Aqueous Solution (20 ° C.,
A dried hydroxyapatite filter cake (Sample No. 5) was obtained in the same manner as in Example 1 except that the temperature was 48 hours) at 60 ° C. for 24 hours. The dried filter cake had the properties shown in Table 1.

[0060]

[Table 1]

Example 3 The sinterability test was performed on each of the dried filter cakes of the starting sample No. 1 obtained in Example 1 and the starting sample No. 4 obtained in Comparative Example 2. For the sinterability test, 20 g of each dried filter cake was used.
It is an X-ray diffraction analysis of the abundance (%) of witlockite in the sintered body when it was fired at 1200 ° C, 1250 ° C, 1300 ° C and 1350 ° C for 1 hour. The results are shown in Table 2.

[0062]

[Table 2]

Reference Example 1 20 g of the dried hydroxyapatite filter cake obtained in Examples 1 and 2 and Comparative Examples 1, 2 and 3 was used as a starting sample, and these were placed in an electric furnace at a heating rate of 3 ° C./min. The temperature was raised to 1350 ° C. and fired for 1 hour to obtain a porcelain. The characteristics of the obtained porcelain are shown in Table 3.

[0064]

[Table 3]

From the above results, it was found that the porcelain obtained from the dried hydroxyapatite filter cake of the present invention is obviously different from known porcelain.

Reference Example 2 20 g of the dried filter cake (starting sample number 1) obtained in Example 1 was calcined at 1250 ° C. for 1 hour under a reduced pressure of 10 ⁻² mmHg,
Then, it was cooled under reduced pressure to a temperature of 200 ° C. to obtain a porcelain.
The porcelain was colorless and transparent with a theoretical density of 3.16 g / cm3.

Reference Example 3 The powder of 200 mesh pass obtained by crushing the porcelain obtained from the starting sample No. 1 in Reference Example 1 and bisphenol-A diglycidyl methacrylate / methyl methacrylate (weight ratio 6/4) were used in a volume ratio ( It means 1: 1 by the actual volume ratio determined from the specific gravity), 0.05% by weight of benzoyl peroxide as a polymerization initiator was further added, and then uniformly mixed with a stirrer. Then, the homogeneous mixture was put into a glass tube having an inner diameter of 5 mm, defoamed, and then subjected to a polymerization reaction at a temperature of 80 ° C. for 2 hours to obtain a hydroxyapatite composition. This composition has a diameter of 3.5
mm, 10 mm in length, and cut into a cylindrical shape, and immediately after tooth extraction, it was embedded in the jawbone of an adult dog that had a hole drilled. As a result, buried 3
It was not eliminated even after months. When the jawbone of an adult dog was cut off 6 months after the implantation and examined by an optical microscope and an X-ray photography, the implant part was healed normally, and new bone tissue was generated in the gap between the implant composition and the jawbone. It was recognized that

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Claims (1)

[Claims] 1. Elemental ratio Ca / P = 1.67 to 1.69, average crystal size length = 187 to 1200 angstrom, width = 50 to
320 angstrom, formed from hydroxyapatite with a length / width of 3.75 to 10 and a void volume of 0.2 to 0.8 cm ³ /
g and the average pore radius between the hydroxyapatite is
A dried hydroxyapatite filter cake, characterized in that it is 50 to 150 angstroms, and no witlock stone is formed even if it is baked at a temperature of 1350 ° C. for 1 hour.