JPS632521B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a mixing liquid for dental gypsum-based investment materials. Dental investment materials are in powder form and are used after being mixed with water or a special mixing liquid. A dental investment material is used as a mold material when manufacturing a dental prosthesis by precision casting, and its usage is as follows. A prototype made of wax is immersed in a slurry made by kneading dental investment material with water or a special liquid, and after solidification, the wax is incinerated by increasing the temperature to 700 to 900 degrees Celsius in an electric furnace. Molten alloy is injected into the resulting cavity. Dental investment materials mainly consist of a binding material and a refractory material, and the binding material solidifies the investment material and binds the refractory material particles to give the molded product strength after solidification and expansion during solidification. The refractory material has the function of providing fire resistance during heating and causing thermal expansion. Solidification expansion and thermal expansion are necessary to compensate for the shrinkage of the alloy during casting by expanding the mold, and to make the cast body the same shape and size as the original. Dental investment materials can be classified according to the type of binding material: those that use gypsum as a binding material (hereinafter referred to as "gypsum-based investment materials") and those that use phosphate as a binding material (hereinafter referred to as "phosphate-based investment materials"). Silica powder such as quartz and cristobalite is used as the refractory material. Gypsum-based investment materials solidify using a hydration reaction in which gypsum hemihydrate becomes gypsum dihydrate, while phosphate-based investment materials solidify oxides such as magnesium, calcium, strontium, and zinc into primary phosphate. It is solidified using a reaction in which it reacts with soluble phosphates such as ammonium and monosodium phosphate to produce insoluble phosphates. Compared to phosphate-based investment materials, gypsum-based investment materials are easy to operate during mixing and burial, have excellent air permeability as molds, and do not seize on cast objects. Because it is easy to use, it is widely used for casting gold alloys, silver alloys, and gold-silver-palladium alloys. On the other hand, phosphate-based investment materials, such as nickel-chromium alloys, can maintain a good cast surface even when cast at high temperatures, so they are often used when casting at temperatures of 1300°C or higher. However, from the viewpoint of operability, gypsum-based investment is difficult, as the conditions during mixing greatly affect the suitability and surface roughness of the cast object, and the investment material sticks to the cast object, making post-casting processing time-consuming. It is inferior to wood. The present invention is a compound that can be used in combination with dental investment materials for the purpose of being easy to process after mixing, embedding, or casting, increasing the strength and fire resistance at high temperatures, and further improving the surface condition of the cast body. This was completed as a result of repeated research aimed at developing a Japanese liquid. Hereinafter, the mixing liquid for the dental investment material according to the present invention will be explained in detail. The focus of the present invention is on the development of a dental investment material mixture for producing a dental investment material mixture that has the operability of a gypsum-based investment material. As a result of repeated studies to achieve this objective by mixing the gypsum investment material with a special mixing solution, we found that
It was discovered that it is effective to knead a gypsum-based investment material with an aqueous solution containing 0.6 to 6% by weight of aluminum phosphate, 1 to 3% by weight of sodium chloride, and 10 to 100 ppm of a surfactant, and having a pH of 1.6 or higher. Ta. The mixing ratio of the kneading liquid to the investment material powder is preferably 1:0.2 to 0.4. As the aluminum phosphate used in the present invention, primary aluminum phosphate, secondary aluminum phosphate, or tertiary aluminum phosphate is effective, but dibasic aluminum phosphate and tertiary aluminum phosphate have low solubility. It is necessary to lower the PH. However, although most inorganic acids can be used for this purpose, sulfuric acid is not suitable since it produces insoluble products. Next, sodium chloride can be replaced with other chlorides, such as potassium chloride, calcium chloride, magnesium chloride, etc., but sodium chloride is the most effective. Furthermore, nonionic and anionic surfactants are suitable. The reason for adding limitations to the scope of the claims is as follows. Aluminum phosphate provides strength when heating the mold and improves the surface of the cast body, but if it is less than 0.6%, the effect of improving the surface of the cast body is not sufficient;
If it exceeds this, problems such as delay in solidification time and sticking of the investment material to the cast body will occur, so it was set at 0.6 to 6%.
Sodium chloride is also useful for improving the surface of castings, but if it is less than 1%, the effect is not sufficient;
If it exceeds 1%, irritating chlorine gas will be generated when heating the mold, so it was set at 1% to 3%. Surfactants are also effective in improving the surface of castings, but they are ineffective at less than 10 ppm;
If it exceeds 100ppm, it will delay the solidification time of the investment material.
10~ to avoid warping and causing surface roughness of the cast body.
It was set to 100ppm. Generally, a very small amount of an antifoaming agent may be used in combination with a surfactant, which is naturally included in the present invention. If the pH is less than 1.6, it is difficult to dissolve aluminum phosphate, so the pH was set to 1.6 or higher. Examples will be described in detail below. All percentages mentioned herein are percentages by weight. Kneading solution 1 of the present invention: 6 g (0.6%) of tertiary aluminum phosphate and 30 g (3%) of sodium chloride are poured into water, and after adding phosphoric acid to completely dissolve, water is added to
g. 50 ppm of sulfonic surfactant (anionic) was added dropwise to this. I measured the pH with a PH meter and it was 3.0. Kneading solution 2 of the present invention 60g (6%) of primary aluminum phosphate and 10g (1%) of sodium chloride are dissolved in 930g (93%) of water, and a fluorine-based surfactant (anionic) is added.
When 50pm was dropped and the PH was measured with a PH meter,
It was 1.6. Kneading solution 3 of the present invention 33 g (3.3%) of di-aluminum phosphate and 20 g (2%) of sodium chloride are poured into water, phosphoric acid is added and dissolved, and a fluorine-based surfactant (nonionic) is added. 50 ppm was added dropwise and water was added to make 1000 g. I determined the pH using a PH meter and found it to be 2.4. Comparative Kneading Solution 1 Only water was used as the kneading solution. Comparative kneading solution 2 33g (3.3%) of primary aluminum phosphate in 967ml of water
g (96.7%), and 50 ppm of a fluorine-based surfactant (nonionic) was added dropwise. Comparative kneading solution 3 33g (3.3%) of primary aluminum phosphate and 20g (2%) of sodium chloride were mixed with 947g (94.7%) of water.
dissolved in Example 1 300 g (30%) of dental anhydrite [JIS T6605, hard plaster for dentistry] and 700 g (70%) of silica sand for foundry use [JIS G5901, silica sand for molding] were mixed uniformly with a mixer. The product prepared in this way was kneaded using the mixing liquid 1 of the present invention and tested according to the method of "JIS T6601 Dental casting investment materials", and the crushing resistance was 51.
It was Kg/ ^cm2 . Moreover, the crushing force after heating to 700°C was 60Kg/cm ² . Next, a wax plate with a smooth surface was buried, heated to 700°C to incinerate the wax, and then cast using molten dental nickel-chromium alloy at 1400°C. After cooling, the cast body was removed. The surface was beautiful and the average center line roughness was 2.1 μm. Examples 2 to 8 Among commercially available dental investment materials, gypsum-based investment materials for inlays, crowns, and cast beds were prepared in the same manner as in Example 1 using the mixing solutions 1 to 3 of the present invention. The test was carried out as follows. The results are shown in Table 1.

[Table] In Example 8 using the kneading solution 3 of the present invention,
Figure 1 shows the results of measuring the surface roughness of a dental nickel-chromium alloy cast using a kneaded and solidified investment material as a mold. Comparative Examples 1 to 4 Tests were conducted using comparative kneading solutions in the same manner as in the examples, and the results are shown in Table 2. Figures 2 and 3 show the results of measuring the surface roughness of each casting when Comparative Mixing Solution 1 in Comparative Example 2 and Comparative Mixing Solution 2 in Comparative Example 3 were used. Indicated.

【table】

[Table] As described above, by mixing the gypsum investment material with the product of the present invention, it became possible to cast a nickel-chromium alloy. This makes it easier to manufacture prosthetics made of nickel-chromium alloy and dramatically improves dental care.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the measurement of the surface roughness of a dental nickel-chromium alloy cast using the investment material solidified using the mixing solution of Example 8, and Figure 2. shows the case of Comparative Example 2, and FIG. 3 shows the case of Comparative Example 3.

Claims (1)

[Claims] 1 aluminum phosphate as weight percent
A dental gypsum-based investment material mixing liquid containing 0.6 to 6% sodium chloride, 1 to 3% sodium chloride, and 10 to 100 ppm of a surfactant, and having a pH of 1.6 or more.