JPH0725720A - Gypsum composition for gypsum mold - Google Patents

Abstract

PURPOSE:To obtain a gypsum composition for a gypsum forming mold useful for efficiently preparing a denture excellent in compatibility by using an acrylic resin. CONSTITUTION:This gypsum composition for a gypsum forming mold useful for producing a denture of acrylic base contains 3-20wt.% carbon powder capable of generating heat by irradiation of microwaves in gypsum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gypsum composition for a gypsum mold for making acrylic resin dentures (acrylic dentures).

[0002]

2. Description of the Related Art Acrylic dentures are generally prepared by filling a dough containing a mixture of an acrylic polymer and a monomer into a plaster molding die prepared by a conventional method for dentistry, and then heating in hot water to polymerize the resin. There is a heat-moisture polymerization method for heating and curing the resin, and a microwave polymerization method for heating and curing the resin by heating a gypsum mold filled with dough with microwave irradiation such as a microwave oven (Japanese Patent Laid-Open No. 61-76149). .

However, since the conventional wet heat polymerization method and microwave polymerization method do not have very good matching accuracy, various methods have been developed for increasing the fitting accuracy of acrylic dentures.
For example, in the wet heat polymerization method, the temperature is lower than the temperature of hot water.
The long-term polymerization method in which it is polymerized in hot water at 0 to 70 ° C for 8 hours or more, and in the microwave polymerization method, aluminum powder is added to a model that reproduces the oral impression and irradiated with microwaves to control the temperature of the model. A method of polymerizing the resin from the surface of the model by raising the temperature of other gypsum molds (Japanese Patent Laid-Open No. 1-25
No. 6954) is proposed.

The method of polymerizing the resin from the surface of the model does not require a long time unlike the wet heat polymerization method, has a good matching accuracy, is simple, and is efficient. However, in order to effectively perform one-sided heating from the model. , 1 expensive aluminum powder in gypsum composition
It must be added in an amount of 0 to 30% by weight, the temperature rise of the model surface is low relative to the amount added, and the price of the model material is high. Furthermore, aluminum powder may cause ignition or explosion. Therefore, there is a drawback that special care is required when manufacturing the model material.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gypsum composition capable of improving the problems caused by the microwave polymerization method. Further, the present invention is to provide a gypsum composition for a gypsum mold for efficiently producing a denture having excellent compatibility by using an acrylic resin.

[0006]

The present invention relates to a gypsum composition for a gypsum molding die for producing an acrylic floor denture, which contains 3 to 20% by weight of carbon powder in the gypsum, the carbon powder generating heat when irradiated with microwaves.

In the present invention, gypsum that is usually used in dentistry can be used as the gypsum, but in consideration of the surface condition of the hardened material, the material price, etc., an anhydrite (α-type hemihydrate gypsum) or Ultra-hard gypsum is preferable, and ordinary gypsum (β-type hemihydrate gypsum) is preferable for burial. Incidentally, the dental plaster optionally contains a curing modifier, a coloring agent and the like.

As the carbon powder to be added to the gypsum in the present invention, carbon powder that generates heat by microwave irradiation such as a microwave oven is used. Graphite, carbon black and the like are preferably used as the carbon powder which generates heat when irradiated with microwaves. The amount of carbon powder in gypsum is 3 to 20% by weight, preferably 5 to 10% by weight. If the content of carbon powder is too small and heated in a microwave oven, the acrylic resin cannot be single-sided polymerized from the model surface without much difference from the temperature increase without addition of carbon powder, and if too much, the surface of the cured product There is a risk that carbon powder will easily come out of the product and a black product will mix into the acrylic dental prosthesis to be molded. The content of the carbon powder is preferably in the above range in order to efficiently generate heat in the model material and to maintain a gray color tone in which it is easy to write the design line of the denture base on the model.

The particle size of the carbon powder is not particularly limited,
In order to obtain good physical properties and operability, 20-600 mesh, preferably 30-400 mesh is suitable.
If the carbon powder contains too many fine particles, the amount of water mixed with the gypsum composition will increase and the strength of the hardened body will decrease, or the hardened body of the model material will contract due to evaporation of plastic water, Adhesion, etc. also occur. On the other hand, if the particle size is too large, the surface of the hardened product becomes uneven, and the surface of the model becomes poor.

The gypsum composition of the present invention is preferably used as a gypsum for a molding die when the acrylic resin is polymerized by irradiation with microwaves such as a microwave oven. Carbon powder is usually added to the model and / or primary buried gypsum that reproduces the oral impression, and then irradiated with microwave to raise the temperature of the model containing carbon powder and / or the primary buried gypsum higher than the temperature of other gypsum molds. By polymerizing the resin from the model surface, it is possible to efficiently produce an acrylic denture with good fitting accuracy in a short time.

[0011]

【Example】

Example 1 5% by weight of graphite powder (30 to 400 mesh) was added to dental anhydrite to prepare a gypsum composition, which was kneaded by adding 28 parts by weight of water to 100 parts by weight of the gypsum composition. A 4 × 4 × 4 mm cured body (sample) was prepared. The cured product was placed in a microwave oven of 500 W and heated for 30 seconds, and the temperature rise of the sample was measured. The results are shown in Table 1.

Example 2 A cured product was prepared in the same manner as in Example 1 except that the amount of the graphite powder added in Example 1 was changed to 10% by weight, and the temperature rise was measured in the same manner. The results are shown in Table 1.

Example 3 A cured product was prepared in the same manner as in Example 1 except that the amount of the graphite powder added in Example 1 was changed to 20% by weight, and the temperature rise was measured in the same manner. The results are shown in Table 1.

Comparative Example 1 A cured product was prepared in the same manner as in Example 1 except that graphite powder was not added, and the temperature rise was measured in the same manner. The results are shown in Table 1.

Comparative Example 2 A cured product was prepared in the same manner as in Example 1 except that 20% by weight of aluminum powder (200 mesh or less) was added instead of the graphite powder of Example 1, and the temperature was similarly raised. It was measured. The results are shown in Table 1.

Comparative Example 3 In place of the graphite powder of Example 1, 10% by weight of iron oxide powder (200 mesh or less) was added,
A cured product was prepared in the same manner as in Example 1, and the temperature rise was measured in the same manner. The results are shown in Table 1.

[0017]

[Table 1]

Example 4 To 100 parts by weight of the gypsum composition of Example 2 to which 10% by weight of graphite powder was added, 28 parts by weight of water was added and kneaded to prepare a model. I made a wax denture. This wax denture was embedded in the lower ring of an FRP flask using the gypsum composition of Example 3. After the primary investment material was cured, secondary investment and dewaxing were performed, and the dough of acrylic resin was filled in the gypsum mold.

Next, the gypsum mold filled with the acrylic resin dough was heated in the 500 W microwave oven for 3 minutes from the lower flask of the flask on the model side, and then the denture was taken out in accordance with the usual method.
I restored it to the model. While the denture was restored to the model, the denture was cut between 7 and 7 teeth and the gap between the denture base and the model was read and measured with a microscope to examine compatibility. The measurement points were 2 on the floor edge and 1 on the midline of the palate. As a result, the average amount of voids on the floor edge was 0.25 mm, and the median palate was 0.17 mm.

Comparative Example 4 A denture base was manufactured in the same manner as in Example 4 except that the anhydrite of Comparative Example 1 was used as the model material and the ordinary plaster was used as the investment material. As a result, the average amount of voids on the floor edge was 0.33 mm, and the median palate was 0.28 mm.

[0021]

According to the gypsum composition for a plaster molding die of the present invention, an acrylic resin is used, and it can be suitably used as a plaster for a molding die when polymerized by irradiation with microwaves such as a microwave oven, A denture having excellent compatibility can be efficiently produced.

Claims (1)

[Claims] 1. A gypsum composition for a gypsum molding die for producing an acrylic floor denture, which comprises 3 to 20% by weight of carbon powder in gypsum that generates heat when irradiated with microwaves.