JPH09220638A - Gypsum insert material for dental casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to exhibit excellent castability and adaptability, etc., by preventing the generation of the thermal decomposition gases of gypsum at the time of casting a high melting metal. SOLUTION: This gypsum insert material consists of a heat resistant material formed of a metal oxide, hemihydrated gypsum and a decomposition suppressing agent for suppressing the thermal decomposition of the gypsum at the time of casting. The decomposition suppressing agent for the gypsum is selected from among a cobalt compd., titanium compd., tungsten compd., nickel compd., chromium compd., manganese compd., zinc compd., selenium compd. and tin compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plaster investment material for dental casting capable of exhibiting excellent castability and compatibility while preventing generation of pyrolysis gas of gypsum during casting of refractory metal. Is.

[0002]

2. Description of the Related Art Conventionally, dental metal fillers such as crowns, bridges and inlays have been produced by the lost wax precision casting method, and the investment materials used at that time are roughly classified into the following two. . One is Tokuho 4-4
A gypsum-based investment material containing quartz or cristobalite as a main component and hemihydrate gypsum as a binding agent, such as found in Japanese Patent Application No. 0321 and Japanese Patent Application Laid-Open No. 61-193741, a gold alloy, a silver alloy, It is used for casting alloys with a relatively low melting point such as gold-silver-palladium alloy, and utilizes the total expansion that combines the rapid expansion of the transformation temperature range of cristobalite at about 200 to 300 ° C and the expansion of quartz. The contraction is compensated for and the conformity is obtained.

The other is a phosphate-based investment material utilizing the reaction of a metal oxide and a phosphate, such as that found in Japanese Patent Laid-Open No. 4-319039, which is a Ni-Cr alloy or high carat. It is used for casting relatively high melting point alloys such as gold alloys and low carat gold alloys, and compensates for metal shrinkage by utilizing the large expansion obtained by kneading with water or colloidal solution of silicic acid. Although such a phosphate-based investment material is difficult to operate because it uses highly viscous colloidal silica, it also causes uneven sintering expansion and deformation of the wax pattern. There is a problem that the yield strength is lowered by deforming or scratching the investment material when excavating because the mold strength is too large, so it is considered to use a gypsum-based investment material for casting a relatively high melting point alloy. ing.

However, in the conventional plaster-based investment material, the total expansion of solidification expansion and heat expansion is about 1.2 to 1.9% (700
Therefore, even if it exhibits sufficient compatibility for casting low melting point metals, when casting high melting point metals, the gas generated by thermal decomposition of the gypsum component causes roughening of the casting surface, seizure,
Gas absorption etc. occurs and it is difficult to cast for practical use,
In addition, expansion is insufficient for casting refractory metals and sufficient compatibility cannot be obtained. Furthermore, compatibility is achieved mainly with the help of abrupt expansion in the transformation temperature range of cristobalite at about 200 to 300 ° C. However, there is a problem that this phenomenon causes a rapid expansion of the investment material, causing cracks in the mold to generate burrs in the investment material, and the demand is increasing recently. It was not possible to cast dental metal fillings made of high melting point alloys such as porcelain baking alloys (precious, semi-precious, Ni-Cr) and Ni-Cr alloys for casting. .

[0005]

SUMMARY OF THE INVENTION The present invention seeks to solve the above-mentioned conventional problems.
Even when casting a high-melting point metal, it is possible to effectively prevent the generation of gas due to the thermal decomposition of the gypsum component, and to produce a cast body having a rough surface, a seizure-like surface property, and the like, and The heat shrinkage of gypsum can be suppressed and sufficient castability and compatibility can be demonstrated, and high quality investment material can be formed without the occurrence of burrs, and it has excellent fluidity and complexity. An object of the present invention is to provide a dental casting gypsum investment material that can accurately mold the investment material even if it has any shape, and can easily excavate the investment material without damaging it.

[0006]

The present invention, which has been made to solve the above-mentioned problems, provides a heat-resistant material made of a metal oxide,
It is characterized by comprising hemihydrate gypsum and a decomposition inhibitor that suppresses thermal decomposition of gypsum during casting. In addition,
As the decomposition inhibitor that suppresses the thermal decomposition of gypsum during casting, as a compound selected from cobalt compounds, titanium compounds, tungsten compounds, nickel compounds, chromium compounds, manganese compounds, zinc compounds, selenium compounds, tin compounds. A required amount thereof may be added, and a predetermined amount of a gypsum whisker, a metal such as Zr or W, a carbide thereof, or a nitride thereof may be added together with a decomposition inhibitor that suppresses the thermal decomposition of gypsum.

The present invention is a plaster investment material for dental casting which uses a heat-resistant material made of a metal oxide and a hemihydrate gypsum as a base material as a base material. One or two selected from alumina, alumina, magnesia, zirconia, and synthetic aluminum silicate
More than one species is common. Then, in the present invention, the heat-resistant material consisting of the metal oxide and the hemihydrate gypsum, which is a binder, are added to the base material in the required amount of a decomposition inhibitor that suppresses the thermal decomposition of gypsum during casting. There is a feature of the invention.

By adding a decomposition inhibitor that suppresses the thermal decomposition of gypsum to a heat-resistant material made of a metal oxide and hemihydrate gypsum that is a binder, excellent surface properties without roughening or seizure of the casting surface are obtained. Theoretically, the reason is that it is possible to produce a cast body that has a complicated shape, and that the investment material can be accurately formed even if it has a complicated shape and that the investment material can be easily dug out without damaging it. Although it has not been clarified, it is probably because a decomposition inhibitor that suppresses the thermal decomposition of gypsum acts to suppress the condensation reaction with calcium oxide and to suppress the generation of gas due to the thermal decomposition of gypsum during casting. The results of various studies conducted by the inventors through trial and error show that cobalt compounds, titanium compounds, tungsten compounds, nickel compounds, chromium compounds, manganese compounds, zinc compounds, selenium compounds. It has been found that can be selected from tin compounds. In addition, the preferable addition amount of the decomposition inhibitor necessary for suppressing the generation of sufficient gas is 0.5 to 30 parts by weight with respect to 100 parts by weight of a heat-resistant material and hemihydrate gypsum made of metal oxide by external addition. And particularly preferably 3 to 7 parts by weight.

In addition to a decomposition inhibitor that suppresses the thermal decomposition of gypsum during casting, for example, the diameter is about 2 to 5 μm, the average length is 50 to 100 μm, and the aspect ratio (aspect ratio =
By adding anhydrous salt type gypsum whiskers (fiber length / diameter) of about 20 to 50, sufficient expansion is secured even for gypsum-based investment materials, and sufficient castability and compatibility for casting of high melting point metals It is more preferable because the property can be exhibited. The addition amount of this gypsum whisker is 0.5 to 20 with respect to 100 parts by weight of heat-resistant material consisting of metal oxide and hemihydrate gypsum by external addition.
A range of parts by weight is preferred. This is because when the amount of gypsum whiskers added is less than 0.5 parts by weight or more than 30 parts by weight, an appropriate shrinkage suppressing effect cannot be obtained and it is difficult to achieve the initial purpose.

Furthermore, in order to further suppress the heat shrinkage of gypsum, one or two selected from Zr, W, Ti, Mo or carbides, nitrides, borides and silicides of these metals. It is preferable to add the above powders. this is,
Carbides, nitrides, borides of the above metals added,
This is because the powder of the silicide changes to an oxide when heated, and the oxidative expansion at this time expands the investment material and can exert a more sufficient shrinkage suppressing effect. The addition amount of such metal carbide, nitride, boride, or silicide powder is 10
If it exceeds 0.5 parts by weight, the fluidity of the slurry and the surface properties of the investment material may be affected, and if it is less than 0.5 parts by weight, the effect of further suppressing heat shrinkage of gypsum is poor, so 0.5-10. About parts by weight is preferable.

Further, as the heat-resistant material composed of the above-mentioned metal oxides, silica particles, which are widely used in conventional plaster-based investment materials, are replaced with those containing alumina having a particle size of 50 μm, particularly preferably 10 μm or less. It is preferable that the heat resistance can be improved and the surface roughness of the cast product can be greatly improved, and burrs can be prevented.

[0012]

Example A gypsum-based investment material was prepared by mixing the components having the compositions shown in Tables 1 to 4, and this gypsum-based investment material was used as a high melting point metal for porcelain baking alloys with Ni-Cr alloys. As a result of casting a dental metal filler made of a precious alloy (including a semi-precious alloy), it was confirmed that all of the castability, compatibility and surface properties were satisfied.
On the other hand, as a comparative example, a component having the composition shown in Table 5 was blended to prepare a gypsum-based investment material, and a dental metal filling was cast with this gypsum-based investment material. No conforming or surface quality was obtained. In each table, ◯ means good, Δ means usable, x means not usable, and PR indicates precious alloy. In addition, except for Comparative Example 2, in all other cases, the water mixing rate is 35%, and all% in the table are weight% and the addition amount is a heat-resistant material made of metal oxide +
It is the amount of external addition to 100 parts by weight of gypsum hemihydrate.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Table 4]

[0017]

[Table 5] (Note) The water mixing ratio of Comparative Example 2 is 45%, and the water mixing ratio of all others is 35%.

[0018]

As is apparent from the above description, the present invention effectively prevents the generation of gas due to the thermal decomposition of the gypsum component even when casting a high melting point metal, and the surface of the casting is roughened, seized, etc. It is possible to produce a cast body with excellent surface properties and to prevent heat shrinkage of gypsum to exhibit sufficient castability and compatibility, and it is a high quality burial without burrs. Material that can be molded, and that has excellent fluidity and can accurately mold the investment even if it has a complicated shape, and can also easily excavate the investment without damaging it. Is. Therefore, the present invention, as a dental casting gypsum investment material that has eliminated the conventional problems,
The contribution to industrial development is extremely large.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Haruhisa Kato 3-36, Noritake Shinmachi, Nishi-ku, Nagoya-shi, Aichi Noritake Co., Ltd. Limited (72) Inventor Tatsuo Yamamoto 3-chome, Noritake Shin-cho, Nishi-ku, Aichi No. 1-36 Noritake Co., Ltd. in Limited (72) Inventor Takahiro Ito Noritake Shincho, Nishi-ku, Nishi-ku, Nagoya, Aichi Prefecture No. 1-36 Noritake Co. Limited (72) Inventor Akio Takimoto Noritake-shin, Nishi-ku, Nagoya, Aichi No. 3 1-36 Noritake Co., Ltd. (72) Inventor Kiyoko Saka 37, Ueda Sanchikawara, Tenpaku-cho, Tenpaku-ku, Nagoya, Aichi Prefecture Tenpaku-cho, Tenpaku-ku, Nagoya Prefecture Hara 37 address of 313, Ltd. cusp dental service within the plies

Claims (7)

[Claims] 1. A plaster investment material for dental casting, comprising a heat-resistant material made of metal oxide, hemihydrate gypsum, and a decomposition inhibitor that suppresses thermal decomposition of gypsum during casting. 2. A decomposition inhibitor for suppressing thermal decomposition of gypsum,
Cobalt compound, titanium compound, tungsten compound,
The plaster investment material for dental casting according to claim 1, which is selected from nickel compounds, chromium compounds, manganese compounds, zinc compounds, selenium compounds, and tin compounds. 3. A heat-resistant material consisting of metal oxide + hemihydrate gypsum 1
The plaster investment material for dental casting according to claim 1, wherein 0.5 to 30 parts by weight of a gypsum decomposition inhibitor is externally added to 100 parts by weight. 4. A heat-resistant material consisting of metal oxide + hemihydrate gypsum 1
The plaster investment material for dental casting according to claim 1, 2 or 3, wherein 0.5 to 20 parts by weight of gypsum whiskers are externally added to 00 parts by weight. 5. A heat-resistant material composed of metal oxide + hemihydrate gypsum 1
1 part selected from carbides, nitrides, borides, and silicides of Zr, W, Ti, Mo or their metals per 100 parts by weight.
The plaster investment material for dental casting according to claim 1, 2 or 3 or 4, wherein 0.5 to 10 parts by weight of one or more powders is externally added. 6. The plaster investment material for dental casting according to claim 1, wherein part or all of the heat-resistant material made of a metal oxide is alumina. 7. The plaster investment material for dental casting according to claim 6, wherein the particle size of alumina is 50 μm or less.