JPH0419864B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Technical Field) The present invention relates to a milky-white calcium phosphate-based crystallized glass dental molding having high strength and translucence, suitable for use as a dental material, such as an artificial tooth, It relates to manufacturing methods for dental crowns, inlays, bridges, etc.

(Prior art and its problems) As dental materials such as dentures, tooth roots, crowns, inlays, and bridges, and biomedical ceramic materials such as artificial bone materials for surgery, for example, Japanese Patent Publication No. 11625/1983 discloses CaO28 to 57wt%. , glass with a composition of 72 to 43 wt% P ₂ O ₅ , or 10 wt% or less of Al ₂ O ₃ ,
Calcium phosphate-based crystallized glass has been proposed, which is obtained by melting glass to which SiO ₂ or B ₂ O ₃ is added, and heat-treating the glass after forming to crystallize it to a degree of crystallinity of 20% or more.

This calcium phosphate crystallized glass has a composition very similar to that of natural teeth or natural aggregate, and the product is translucent and white in color, and its color and gloss are also similar to those of natural materials. and
Its physical, chemical, and mechanical properties are close to those of natural teeth or natural aggregate, and it is compatible with living organisms. Moreover, it is easy to melt the raw material powder into a glass shape, pour it into a mold, and then crystallize it. It can be manufactured using a simple process, and the shrinkage rate during the manufacturing process is only 1% or less, and precision machining is not required even for complex shapes, making it suitable for biological applications such as dental materials and surgical artificial bone materials. As a ceramic material, it is expected to have superior properties and high mass productivity compared to conventional metal and ceramic materials.

In addition, regarding the manufacturing method of calcium phosphate crystallized glass suitable for dental crown restoration materials, Japanese Patent Application Laid-open No. 1983-
Publication No. 141508, Comm.Am, Cera.Soc.C−101
(1984), in which a molding method using the lost wax method is disclosed.

When calcium phosphate crystallized glass is molded by the conventional lost wax method, a very good glass cast dental molded body can be obtained. However, since the glass molded body has low strength and is brittle, it is crystallized to form a crystallized glass molded body.

However, when glass is crystallized, voids are generated in the crystallized glass, which can cause holes in the surface of the molded product, damage the appearance, and reduce the strength of the voided parts, making them more likely to break. I had a problem.

(Objective of the invention and its problems) The present invention was obtained based on the results of various studies and studies aimed at solving the above-mentioned problems. When the glass molded body is crystallized to obtain a calcium phosphate-based crystallized glass molded body, the diameter of the sprue wire in the investment material that is the mold is adjusted to The present invention relates to a method for producing a calcium phosphate-based crystallized glass dental molded body, which is characterized by obtaining a void-free crystalline glass molded body by making the thickness larger than the wall thickness of the crystalline glass molded body.

(Structure of the invention) The present invention will be explained in more detail below.

The glass composition used in the present invention is composed of calcium metaphosphate (CaO・P ₂ O ₅ ) having a chain structure both in the glass state and in the crystalline state, and has an appropriate melting temperature and a melt that is easy to cast. In order to have liquid viscosity, it is optimal to have a calcium to phosphorus atomic ratio Ca/P in the range of 0.35 to 0.7, that is, a composition of CaO 28 to 36 wt% and P ₂ O ₅ 72 to 64 wt%. Particularly preferred are those with Ca/P in the range of 0.35 to 0.49, which are easy to cast by the lost wax method and are easy to crystallize.
CaO4 1 mol% to 49.5 mol% is desirable.
If the Ca/P ratio exceeds 0.7, vitrification becomes difficult and is undesirable, and if it is lower than 0.35, crystallization becomes difficult and uniform crystallization cannot be obtained, and the phosphorus component becomes excessive and durability deteriorates. It is unfavorable because it deteriorates. Calcium phosphate glass with this composition has the composition of natural teeth and aggregates, that is, it is mainly composed of calcium phosphate crystals and amorphous, and the atomic ratio of calcium to phosphorus, Ca/P, is in the range of about 1.75 to 2.0. It is similar and has good affinity with the subject. According to the glass having such a composition, an artificial dental material can be obtained through a simple process of melting the glass raw material powder into a glass form, pouring it into a mold, and crystallizing it.

In the present invention, Al ₂ O ₃ , ZrO ₂ , TiO 2 is added to the calcium phosphate crystalline glass having the above composition in order to improve the water resistance of the glass and to uniformly precipitate crystallization in the crystallization process _. ,
SnO ₂ , Y ₂ O ₃ , Fe ₂ O ₃ and the like can be added in an amount of 0.5 to 5 mol % to the above calcium phosphate crystallized glass. If the addition ratio of additive components such as Al ₂ O ₃ exceeds 5 mol %, melting and vitrification of the calcium phosphate crystalline glass will become difficult, which is undesirable, and if it is lower than 0.5 mol %, the effect of improving water resistance will be reduced. This is not desirable as it becomes low.

In producing the calcium phosphate glass of the present invention, CaO or a calcium compound that can become CaO and a phosphoric acid compound that can become P ₂ O ₅ as raw materials,
Al ₂ O ₃ or an aluminum compound that can be Al ₂ O ₃ is prepared, mixed, slurried as necessary, dried, and crushed to prepare calcium phosphate powder containing Al ₂ O ₃ , Melt this. When producing a dental molded body from this calcium phosphate crystalline glass, the melt is cast into a predetermined shape by the lost wax method, and then slowly cooled.
It is then crystallized to obtain the final product.

The most typical calcium compounds mentioned above are calcium carbonate and calcium oxide.
Other calcium hydroxide, calcium hydrogen carbonate,
Inorganic and organic salts of calcium such as calcium oxalate and calcium acetate are produced. As the phosphoric acid compound, phosphoric acids such as orthophosphoric acid, or ammonium salts of these phosphoric acids are used.

In addition, calcium phosphates such as calcium phosphate, calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium pyrophosphate, acidic calcium phosphate, calcium polyphosphates, and hydroxyapatite can also be used alone or in combination with other calcium compounds or phosphorus compounds. You can also use

Further, as the aluminum compound, aluminum hydroxide, aluminum oxide, aluminum nitrate, ammonium aluminum carbonate, aluminum chloride, etc. are used.

For example, in producing the calcium phosphate-based crystallized glass dental molded article described above, finely pulverized CaCO ₃ is mixed with 28 to 42 mol% and H ₂ PO ₄ is mixed with 55 to 42 mol%.
Weigh and mix 73 mol%, powdered Al(OH) ₃ , 0.5 to 5 mol%, and add water to this to form a slurry.
This is dried and crushed to prepare calcium phosphate powder containing Al ₂ O ₃ components, which is heated at 200 to 900℃.
Fire for 1 to 10 hours to prepare glass raw materials. Next, put the required amount of this glass raw material into a platinum crucible.
After heating and melting at 900 to 1,500°C for 5 minutes to 10 hours to homogeneously vitrify, a mold of a predetermined shape is made from wax based on the lost wax method, and a phosphate-based slurry is embedded around this mold. After the investment material has solidified, the wax is incinerated to form a casting mold, the casting mold is maintained at 500 to 800°C, and centrifugal casting, compression casting,
Temperatures of 900°C or more are achieved by casting methods such as vacuum compression casting.
Molten glass at around 1500℃ is cast and shaped. Next, the calcium phosphate-based crystalline glass molded body is subjected to a crystallization treatment to obtain a calcium phosphate-based crystallized glass. This molded body may be subjected to heat treatment and crystallization treatment together with the investment material, or may be taken out from the investment material and subjected to crystallization treatment. The crystallization means for this glass molded body is not particularly limited, and for example, 500
A method of holding in an atmosphere at ~900°C for 5 minutes to 100 hours is used.

However, this glass molded object has low strength and is brittle, so it easily breaks when removed from the investment material.
In addition, deformation may occur during crystallization, so
A method in which the entire investment material is heat treated is preferred.

However, in calcium phosphate crystalline glass, crystallization occurs from the surface and progresses to the inside at a fairly uniform rate. Crystallized glass has a higher density than glass, so when the glass parts left inside crystallize, voids may occur due to shrinkage due to crystallization. This void occurs in the component where crystallization occurs last.

In the case of the lost wax casting method, sprue wire is used to form the sprue (runner) in the mold. The sprue wire is a columnar body made of a material such as wax, and is attached to a wax pattern. After burial, it is removed at the same time as the wax pattern is incinerated and the cavity in that area becomes sprue.

In the present invention, by making the diameter of this sprue wire larger than the maximum thickness part of the cast glass molded body, a part where crystallization will finally occur is created in the sprue. That is, according to the present invention, by selectively forming voids generated during crystallization within the sprue, it is possible to prevent voids from forming within the intended shaped crystallized glass.

It is preferable that the sprue wire is attached to the wax pattern near the maximum thickness part, and it is preferable to attach a plurality of sprue wires to the part where there are a plurality of maximum thickness parts.

(Example) Examples of the present invention will be described below.

Example 1 As Example 1, a method for manufacturing a dental crown according to the present invention will be described with reference to FIG.

First, as shown in FIG. 1a, heated and melted wax was applied to a tooth plaster mold 1 to create a wax pattern 2 for making a dental crown. This wax pattern 2 had a wall thickness of 1.8 mm at the center, a wall thickness of 0.8 mm at the periphery, and a diameter of 10 mm. A sprue wire 3 was attached to this wax pattern 2 for making a tooth crown, and this was set approximately in the center of the container 4 as shown in FIG. 1b. This sprue wire 3 becomes the sprue (runner) 5, and has a diameter of 3 mm. Next, as shown in FIG. 1B, a slurry 6 of a phosphoric acid-based investment material prepared as an investment material is poured into the container 4 in which the wax pattern 2 is set, and the wax pattern 2 is buried therein. After curing and drying this
Wax pattern 2 and sprue wire 3 were incinerated by heating to 300°C to 1000°C. In this way, the first
A lost wax mold 7 for a tooth crown and a sprue 5 having the same shape as shown in Figure c, having a thickness of 1.8 mm at the center, a thickness of 0.8 mm at the periphery, and a diameter of 10 mm were formed.

On the other hand, _CaCO3 powder corresponding to 46 mol% as _CaO and Al(OH) ₃ corresponding to 1 mol% as _Al2O3
Phosphoric acid containing H ₃ PO ₄ corresponding to 53 mol% as P ₂ O ₅ was added to the mixture with the powder, the resulting reaction product was dried and crushed, and then the powder was heated at 400°C.
The fired product was fired for 5 hours in a platinum crucible.
A glass melt was prepared by melting at 1250°C for 2 hours with stirring.

As shown in Fig. 1d, this glass melt 10 is cast through the sprue 5 into a lost wax mold 7 for making a dental crown using a centrifugal casting machine, and then the investment mold 8 is held in an electric furnace at 630°C for 20 hours. After crystallization treatment, the molded body was taken out from the investment material. Then, as shown in FIG. 1e, the sprue 5 was cut along line A-A' to obtain a tooth crown 9.

When the 10 calcium phosphate-based crystallized glass tooth crowns thus obtained were examined for voids using an X-ray transmission method, no voids were observed in any of the crystallized glass tooth crowns.

In addition, the obtained crystallized glass tooth crown has a dimensional change of less than 30μ compared to the wax type, and has an extremely precise precision, and has a compressive strength of 4000
Kg/m ³ , and the bending strength was 1200 Kg/cm ² .

Comparative Example Ten crystalline glass tooth crowns were obtained in the same manner as in the example except that the diameter of the sprue wire was 1 mm.

When inspecting for voids using an X-ray transmission method, formation of voids was observed in 6 out of 10 samples.

(Effects of the Invention) As described above, according to the present invention, since the diameter of the sprue is larger than the maximum thickness part of the cast glass molded body, the part where crystallization occurs last is within the sprue, and therefore, Even if voids occur, these voids can be prevented from occurring within the sprue and within the molded crystallized glass that will become the tooth crown, and a dense biomorphic body can be obtained. Therefore, the strength of calcium phosphate-based crystallized glass molded objects such as dental crowns does not decrease, become brittle, or lose their appearance, and the artificial dentistry has high strength, good surface quality, and excellent appearance. materials can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a process for manufacturing an artificial dental material by a lost wax method according to an embodiment of the present invention. 1: Plaster mold, 2: Wax pattern, 3: Sprue line, 4: Container (ring), 5: Sprue,
6: Investment material, 7: Lost wax type (cavity created by wax incineration), 8: Investment type, 9: Dental crown,
10: Glass melt.

Claims (1)

[Claims] 1. Calcium phosphate-based crystalline glass is cast by a lost wax method to obtain the crystalline glass molded body, and the crystalline glass molded body is subjected to crystallization treatment to obtain the calcium phosphate-based crystallized glass molded body. A calcium phosphate-based crystallized glass dental molded body, characterized in that a void-free crystallized glass molded body is obtained by making the diameter of the sprue wire in the investment material of the mold larger than the wall thickness of the crystalline glass molded body. manufacturing method. 2. The method for producing a calcium phosphate-based crystallized glass dental molded body according to claim 1, wherein the wall thickness of the crystallized glass molded body is 0.1 to 5.0 mm. 3. The method for producing a calcium phosphate-based crystallized glass dental molded article according to claim 1, wherein the crystallized glass molded article is a dental crown, an inlay, a bridge, or a denture.