JPH0822731B2 - Dental material Ca -4 below P-2 below O-9 below Powder manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention can produce a hardened body having a high filling bulk density and a high crushing resistance, which is suitable as a dental material such as a dental cement and a root canal filling material. The present invention relates to a method for producing Ca ₄ P ₂ O ₉ powder for dental materials.

[Prior Art] Conventionally, zinc oxide and silicon oxide have been used as cement fillers used in dentistry, but these have a drawback that they have no biocompatibility. Recently, α-tricalcium phosphate (hereinafter referred to as α-TCP), which is close to human bone composition and has high biocompatibility, has been attracting attention. However, α-TCP produced by the conventional production method has a small packing bulk density, and a cured product obtained by kneading the same with a kneading liquid has a small crushing resistance and is unsuitable as a dental material.

Therefore, apart from this, the present inventors have found that α-TCP, which has a large packed bulk density and can provide a cured product with a large crushing resistance.
A manufacturing method of powder was proposed.

[Problems to be solved by the invention]

However, α-TCP produced by the above method gives a cured product with a crushing resistance of 800 kg / cm ² or more, but the disintegration rate is 2%.
Since it is high as above, the use is limited to those that can be used even at this disintegration rate.

The present inventor paid attention to Ca ₄ P ₂ O ₉ which has a structure similar to α-TCP and promoted earnest research.

Usually, Ca ₄ P ₂ O ₉ powder is calcium carbonate (CaCO ₃ )
If, dicalcium phosphate (CaHPO ₄ or CaHPO ₄ · 2H
₂ O) or calcium pyrophosphate (Ca ₂ P ₂ O ₇ ) powder is mixed in a predetermined molar ratio, fired at a synthesis temperature, and then crushed. However, the Ca ₄ P ₂ O ₉ powder produced by this method has a primary particle size of about several μm at the maximum, many secondary agglomerated particles, an unstable particle size, and a packed bulk density of less than 1.2. It was low. As a result, for example, the crushing effect of a cured product obtained by using an aqueous solution of 40 to 60 wt% of a copolymer of acrylic acid 85 parts by weight and itaconic acid 15 parts by weight as a kneading liquid is 200 kg / cm ² or less, which is completely unsatisfactory. there were.

The present inventors, based on the knowledge obtained in the development of α-TCP powder manufacturing method for dental materials, as a result of various studies, Ca ₄ P ₂ O ₉ as well as α-TCP, powder particles It was found that the shape, particle size distribution, packed bulk density, and the like of the above, influence the crushing resistance of the cured product using this as a filler.

The present invention has been made based on the above findings, good biocompatibility, high packing bulk density, a large crushing resistance of a cured product made using this, and a low disintegration rate,
An object of the present invention is to provide a method for producing Ca ₄ P ₂ O ₉ powder suitable for dental materials.

[Means for solving problems]

The present invention has been made to achieve the above object, the gist thereof is a powder obtained by uniformly mixing calcium carbonate powder and dicalcium phosphate powder in a molar ratio of 1: 1 or calcium carbonate powder and calcium pyrophosphate powder. To 2:
The powder uniformly mixed in a molar ratio of 1 was molded at a pressure of 0.1 t / cm ² or more, reacted at a temperature of 1200 ° C. or more, and then pulverized and classified to 70 wt% of powder having a particle diameter of 2 to 32 μm. This is a method for producing a Ca ₄ P ₂ O ₉ powder for dental materials, which is a powder containing the above.

[Specific configuration and operation of the invention]

In the present invention, CaCO ₃ , which is used as a raw material for synthesizing Ca ₄ P ₂ O ₉ , CaHPO ₄ , CaHPO ₄ .2H ₂ O, Ca ₂ P ₂ O ₇ , the particle size of the powder is not strictly limited, but in coarse particles Since the reaction between solids is slow, it is usually used as a powder having an average particle size of 5 μm or less. Further, the raw materials are mixed in a molar ratio of 1: 1 in the case of CaCO ₃ and CaHPO ₄ · 2H ₂ O, and in a 2: 1 ratio in the case of CaCO ₃ and Ca ₂ P ₂ O ₇ .

Further, the molding pressure is preferably 0.1 t / cm ² or more particularly ^{1t / cm 2 ~2t / cm 2} . If the molding pressure is less than 0.1 t / cm ² , it is difficult to obtain a desired particle size distribution. In this case, even if the molding is carried out at a pressure slightly lower than 0.1 t / cm ² , for example, a desired particle size and a particle size distribution can be obtained by firing at a temperature of 1400 ° C. or higher,
High heating temperature is not economical. Also, the molding pressure is 2t / c
Even if it exceeds m ² , the crushing resistance is not improved and it is economically disadvantageous. A rubber press, a briquetting machine, a die press or the like can be used for the pressure molding.

The temperature at which the pressure-molded compact is fired needs to be 1200 ° C. or higher. If the firing temperature is less than 1200 ° C, the reaction does not proceed sufficiently and the crystal phase and physical properties are poor. The firing temperature is not particularly limited as long as it is a temperature between 1200 ° C. and the melting point of Ca ₄ P ₂ O ₉ , but unnecessarily high temperature is not preferable because of large economic loss. The firing is performed in an electric furnace, the atmosphere is a normal atmospheric atmosphere, preferably dry air, and the firing time is about 1 to 6 hours after the temperature of the formed body exceeds 1200 ° C.

The calcined and reaction-generated Ca ₄ P ₂ O ₉ compact was roughly pulverized and then pulverized by a ball mill, etc., and then classified by an air classifier to obtain a powder containing 70 wt% or more of particles in the range of 2 to 32 μm. The body. In this case, 70 wt% of particles in the range of 2-32 μm
If it is less than the range, sufficient crushing resistance as a filler for dental cement cannot be obtained. Also, the filling bulk density is 1.2 or more, especially
1.4 or more is preferable. If it is less than 1.2, sufficient crushing resistance cannot be obtained.

SEM observation of the Ca ₄ P ₂ O ₉ powder produced by the above method revealed that no blocky primary particles, secondary agglomerated particles, or coral-shaped particles were observed at all, and the packed bulk density was 1.4 or more. Met.

To use this Ca ₄ P ₂ O ₉ powder for dental treatment, usually, the acrylic acid, used by kneading 50 wt% about of an aqueous solution of itaconic acid copolymer as a kneading liquid, Ca ₄ P ₂ O _{9 The} powder / kneading liquid weight mixing ratio is preferably 1.0 to 2.0. If the weight mixing ratio is less than 1.0, the crushing resistance of the cured product will be reduced to 2.0.
If it exceeds the above range, the amount of powder is too large to perform sufficient kneading. As the kneading liquid, an aqueous solution of a lactic acid polymer and glycolic acid (for example, 23% by weight of lactic acid polymer and 6% by weight of glycolic acid) is used in addition to the above copolymer.

Thus, the Ca ₄ P ₂ O produced by the method of the present invention
All of the cured products obtained by kneading ₉ powders with an acrylic acid / itaconic acid copolymer aqueous solution have a crushing resistance of 700 kg / cm ² or more and a disintegration rate of less than 2%.

Further, the raw material powder mixture in the above method is heated to 1200 ° C. or higher to previously generate Ca ₄ P ₂ O ₉ , and this is pressure-molded at a molding pressure of 0.1 t / cm ² or higher, and this molded body is again subjected to 1200 Particles in the range of 2 to 32 μm that have been baked, crushed and classified at 70 ° C or higher are used.
All Ca ₄ P ₂ O ₉ powders containing more than wt% have no blocky primary particles, secondary agglomerated particles, or coral-shaped particles, and their filling bulk density is 1.4 or more, and they are hardened by kneading with the kneading liquid. The crushing resistance of the body was 700 kg / cm ² or more, and the disintegration rate was less than 2%. Although the product with good physical properties can be obtained as described above, the number of steps is increased, which is disadvantageous as a manufacturing method.

However, the above results show that when processing the raw material powder that is uniformly mixed to a predetermined molar ratio, if a step of heating it to 1200 ° C. or higher after molding it at a pressure of at least 0.1 t / cm ² or more, It is shown that Ca ₄ P ₂ O ₉ powder having excellent blocky primary particles as a filler for dental cement is obtained.

EXAMPLES Next, the present invention will be described with reference to examples and comparative examples.

Example 1 CaCO ₃ and Ca ₂ P ₂ O ₇ were pulverized and mixed in a molar ratio of 2: 1 for 2 hours, molded with a rubber press at a pressure of 1 t / cm ² , and calcined in an air atmosphere at 1300 ° C. for 3 hours. . After baking this with a milk body 2000μ
coarsely pulverized to m or less and further pulverized with a ball mill for 24 hours. This was classified to obtain Ca ₄ P ₂ O ₉ powder having a particle size of 5 to 16 μm of 90 wt%. SEM observation of this powder revealed that there were no secondary agglomerated particles, all were blocky primary particles, and their packed bulk density was 1.5. Then, acrylic acid 8 as a kneading liquid
A 50% aqueous solution of a copolymer of 5 parts by weight and 15 parts by weight of itaconic acid was used and kneaded at a ratio of Ca ₄ P ₂ O ₉ powder / aqueous copolymer solution ratio of 1.5 to obtain a cured product. The crushing resistance of this cured product is 711 kg /
cm ² , disintegration rate was 0.8%. However, the collapse rate is JIS-T66
As shown in 02,
Immerse the product in water at ℃ for 24 hours to reduce the weight loss of the cured product.
It is shown by.

Comparative Example 1 CaCO ₃ and Ca ₂ P ₂ O ₇ were pulverized and mixed at a molar ratio of 2: 1 for 2 hours to obtain 130
It was calcined at 0 ° C. for 3 hours to form Ca ₄ P ₂ O ₉ and crushed for 2 hours with a ball mill. The particle size distribution after crushing is 48 μm or less, particle size
50 μm or less was 3.8 μm or less, and the packed bulk density was 1.15. When this powder was observed by SEM, the primary particle diameter was 8 μm at maximum, and many coral-shaped primary particles and secondary aggregated particles were observed. Using this Ca ₄ P ₂ O ₉ powder, a cured product was prepared in the same manner as in Example 1, but the crushing resistance was 285 kg /
It was cm ² .

Comparative Example 2 The Ca ₄ P ₂ O ₉ powder having a packed bulk density of 1.15 obtained in Comparative Example 1 was molded with a rubber press at a pressure of 1 t / cm ² and baked at 1300 ° C. for 3 hours. This was coarsely pulverized to 2000 μm or less, further pulverized with a ball mill, and classified to obtain Ca ₄ P ₂ O ₉ powder having a particle size distribution of 3 to 16 μm of 90 wt%. Using this, the packed bulk density and the crushing resistance of the obtained cured product were measured under the same conditions and operations as in Example 1, and the same results as in Example 1 were obtained.

Comparative Example 3 CaCO ₃ and Ca ₂ P ₂ O ₇ were pulverized and mixed at a molar ratio of 1: 1 for 2 hours, molded with a rubber press at a pressure of 1 t / cm ² , and calcined at 1300 ° C. for 3 hours to obtain α-TCP. did. This was roughly crushed to 2000 μm or less in a mortar and then crushed for 24 hours with a ball mill. This was classified to obtain α-TCP powder having 5 to 16 μm of 90 wt%. Using this powder, a cured product was produced under the same conditions and operations as in Example 1. The crushing resistance of this cured product was 896 kg / cm ² , but the disintegration rate was as high as 5%.

〔effect〕

As described above, Ca obtained by the production method of the present invention
₄ P ₂ O ₉ powder has a high packing bulk density, and a cured product obtained by kneading this with a kneading liquid has excellent physical properties such as a high crushing resistance and a low disintegration rate. In addition, such excellent Ca ₄ P ₂ O
₉ Powder can be produced efficiently, which greatly contributes to dental treatment.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Hiraiwa 1 Shiga, Shiojiri City, Nagano Prefecture Shiojiri Laboratory, Showa Denko KK (56) References JP 61-270249 (JP, A) JP 61- 68054 (JP, A)

Claims (1)

[Claims] 1. A powder in which calcium carbonate powder and dicalcium phosphate powder are uniformly mixed in a molar ratio of 1: 1 or a powder in which calcium carbonate powder and calcium pyrophosphate powder are uniformly mixed in a molar ratio of 2: 1 is 0.1t. Dental material characterized by being molded at a pressure of / cm ² or higher, reacted at a temperature of 1200 ° C. or higher, then crushed and classified to a powder containing 70 wt% or more of powder having a particle size of 2 to 32 μm For the production of Ca ₄ P ₂ O ₉ powder for industrial use.