JPH0698156B2 - Dental mold treatment method and mold coating agent - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a dental mold and a coating agent for use in the method.

[0002]

2. Description of the Related Art As a dental casting apparatus, a pressure melting chamber capable of pressurizing with an inert gas such as argon and a depressurizing casting chamber capable of depressurizing are provided in a vertically connected manner. A melt passage that penetrates the center of the boundary wall of the chamber is opened, a metal crucible is installed in the pressure melting chamber so as to close the upper end of the melt passage, and a movable mold stand is installed in the vacuum casting chamber. Then, the upper end surface of the mold placed on this mold base is pressed against the boundary wall to close the lower end of the molten metal passage, and the inert gas is supplied to the pressurized melting chamber while discharging the air in the reduced pressure casting chamber. It is known that the dental metal in the metal crucible is melted by arc discharge in the atmosphere of the inert gas, and then the molten metal is injected into the lower mold through the molten metal passage.

FIG. 2 is a vertical cross-sectional view showing the vacuum casting chamber 10 of the dental casting apparatus. Reference numeral 11 is a boundary wall which also serves as a crucible stand, and 12 is a molten metal passage. The upper end surface of the dental mold 14 is in pressure contact with the ring-shaped packing 13 surrounding the molten metal passage 12. The dental mold 14 is placed on a mold stand 15 and is moved up and down by a jack (not shown) below. The mold 14 is made of a phosphate-based investment material, and the sprue 14a, the runner 14b, and the cavity 14 are formed along the center line thereof.
c is provided in order from the top, and the molten metal 16 injected from the upper crucible (not shown) enters the cavity 14c through the sprue 14a and the runner 14b, and fills the cavity 14c.

[0004]

Conventionally, a dental mold 1 has been used.
After molding No. 4 by the lost wax method, the molten metal having a relatively high melting point such as nickel-chromium alloy, cobalt-chromium alloy and titanium was poured into the sprue without any treatment on its surface. Contact surface with the mold,
In particular, when the molten metal is in the highest temperature state, and the surface of the sprue 14a which first comes into contact with the molten metal and intake air accompanying the decompression of the reduced pressure casting chamber 10 acts to reduce the castability, the molten metal and the investment material constituting the mold are separated from each other. There has been a problem that impurities are generated by the reaction and the performance of the cast product deteriorates. For example, when casting titanium using a phosphate-based investment material containing silica, which is the most common as the investment material, titanium (Ti)
And silica (Si O ₂ ) react to react with titanium oxide (TiO _2
2 ) occurred, resulting in a decrease in strength and corrosion resistance as titanium.

When zirconia powder or alumina powder is used as a refractory for the investment material in order to prevent the production of titanium oxide, the mold becomes expensive and the coefficient of thermal expansion of these is small, so that it is used for dental purposes. Was inappropriate.

The present invention can form a film capable of preventing the reaction between the molten metal and the burial agent on the surface of the sprue which the molten metal poured from the crucible first comes into contact with at the highest temperature. The present invention provides a method for treating a dental mold that enables the adoption of general silica as a material and improves the castability, and a template agent suitable for use in the treatment.

[0007]

That is, the method for treating a dental mold according to the first aspect of the present invention is directed to a zirconia as a coating agent on the surface of a substantially conical sprue recessed in the center of the upper end surface of the dental mold. It is characterized in that a mixture of sol and zirconia powder is applied.

The template agent according to the second aspect of the present invention is characterized by comprising a mixture of zirconia sol and zirconia powder.

The zirconia sol described above uses water as a dispersion medium, and the zirconia powder mixed with the zirconia sol preferably has a particle size of 0.1 to 44 μm. The blending amount of the zirconia powder is preferably 5 to 60% with respect to the total weight of the zirconia sol and the zirconia powder.
The amount of the above-mentioned coating agent can be adjusted by the number of times of application with a brush or a brush. For example, when the amount of the zirconia powder is about 60%, one application is sufficient, and about 5%. In this case, it is preferable to apply it 2 to 3 times. A surfactant and a defoaming agent can be added.

[0010]

[Function] When a casting agent composed of zirconia sol and zirconia powder is applied to the sprue of a dental mold, the zirconia sol penetrates into the investment material, and the zirconia sol envelops the zirconia powder on the surface of the sprue to form a gel, A low and dense zirconia layer film is formed, and by this film formation, the intake action on the sprue surface due to the pressure reduction outside the mold during casting is greatly reduced, and the pouring pressure is increased accordingly and the casting action is improved. At the same time, the molten metal in the highest temperature state immediately after being poured from the crucible and the investment material on the sprue surface are disconnected, and the reaction between the molten metal and the investment material is prevented. Therefore, an extremely high purity cast product can be obtained.

However, if the amount of the zirconia powder blended is less than 5%, the desired effect cannot be obtained because the coating of the zirconia layer is not formed even if the number of coatings is increased, and 60%.
If it exceeds, the above-mentioned coating will be cracked and cannot be used. Further, when mere water is used instead of the zirconia sol, the zirconia powder is not bonded and simply rides on the surface of the sprue, so that it is easily peeled off by vibration and is washed away during casting. The use of powders of calcia, magnesia, or alumina instead of zirconia powder is not suitable because calcia and magnesia react with water, and alumina reacts with titanium, albeit slightly.

[0012]

EXAMPLE In FIG. 1, a dental mold 20 is made of silica 5
A phosphate-based investment material consisting of 4% by weight, zirconium silicate 30% by weight, magnesium oxide 8% by weight and primary ammonium phosphate 8% by weight was kneaded with a colloidal silica solution and formed into a columnar shape by the obtained investment material composition. It is molded and has a cone-shaped sprue 2 from the top along its center line.
1, a runner 22 and a cavity 23 are provided in that order, and a coating agent of zirconia layer and zirconia powder is applied to the surface of the sprue 21 to form a coating film 24 of a zirconia layer.

The film 24 of the zirconia layer is formed by forming zirconia powder (OZC-OS6 manufactured by Osaka Cement Co., Ltd.),
Surfactant (Perex OT-P manufactured by Kao Corporation),
Defoaming agent (San Nopco Ltd., SN deformer-2
47) and zirconia sol (AZS-NB manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.). At that time, adjusting various coating agents with different blending amounts of zirconia powder,
The mold coating agent was applied to the sprue 21 of the dental mold 20 with a brush, dried, and molten titanium was poured into the mold 20 to cast a crown. Table 1 shows the composition of the mold wash.

Table 1 Example 1 Example 2 Example 3 Example 4 Zirconia powder (%) 10 25 30 50 Surfactant (%) 0.25 0.25 0.25 0.25 Defoamer (%) 0.03 0.03 0.03 0.03 Zirconia sol (%) ) Remaining amount Remaining amount Remaining amount Remaining amount

After casting, the mold is destroyed and the cast product is taken out,
When the surface thereof was visually inspected, no abnormality was found in the appearance in any of the products prepared by applying the mold coating materials of Examples 1 to 4 above. In contrast,
In the comparative example prepared without applying the above mold coating agent, the surface of the mold that was in contact with the sprue was discolored to give a moire pattern, and rough skin having small irregularities was formed.

Next, with respect to the crowns of Example 3 and Comparative Example, the range of 10 μm in length and width from each surface layer of the occlusal surface to each depth of 10 μm was analyzed to examine the composition. The results are shown in Tables 2 and 3. However, Table 2 shows the contents of aluminum, zirconium, phosphorus and oxygen, and Table 3 shows the contents of magnesium, titanium and silicon.

Table 2 Content of each element by depth (%) Depth Example 3 Comparative example (μ) Al Zr P O Al Zr P O 10 0.065 1.356 0.377 58.399 0.000 0.000 0.000 92.278 20 0.043 0.628 0.088 10.245 0.013 0.918 0.113 51.955 30 0.000 0.119 0.010 6.523 0.000 0.348 0.467 51.354 40 0.000 0.047 0.025 4.608 0.000 0.109 0.312 15.648 50 0.000 0.072 0.016 4.459 0.000 0.000 0.007 8.795 60 0.000 0.036 0.000 4.276 0.000 0.012 0.142 5.534 70 0.000 0.000 0.004 3.779 0.001 0.022 0.127 4.459 80 0.000 0.003 0.000 3.976 0.000 0.000 0.085 4.249 90 0.000 0.000 0.001 3.707 0.000 0.000 0.069 4.038 100 0.003 0.000 0.000 2.869 0.000 0.021 0.009 4.021 110 0.000 0.000 0.000 3.224 0.000 0.000 0.009 4.100

Table 3 Content of Element by Depth (%) Depth Example 3 Comparative Example (μ) Mg Ti Si Total Mg Ti Si Total 10 0.044 37.792 1.968 100 0.097 3.411 4.214 100 20 0.018 86.027 2.950 100 0.071 13.659 33.271 100 30 0.000 91.788 1.559 100 0.040 18.069 29.722 100 40 0.000 92.435 2.886 100 0.012 76.061 7.861 100 50 0.000 93.822 1.631 100 0.000 90.798 0.400 100 60 0.012 95.526 0.152 100 0.000 92.311 2.000 100 70 0.005 96.206 0.006 100 0.000 93.583 1.808 100 80 0.000 96.004 0.017 100 0.002 94.092 1.572 100 90 0.000 96.289 0.003 100 0.000 94.844 1.048 100 100 0.000 97.115 0.012 100 0.000 95.731 0.217 100 110 0.000 96.760 0.016 100 0.000 95.891 0.000 100

As is apparent from Tables 2 and 3 above, in Example 3, the titanium content reaches about 38% in the surface layer having a depth of 10 μ, and exceeds 90% at the depth of 30 μ. In the comparative example, the titanium content in the surface layer having a depth of 10 μ was 1/10 of that in Example 3, and the titanium content exceeded 90% after the depth of 50 μ. On the other hand, the silicon contents of Example 3 and the comparative example were about 2% and about 4% at a depth of 10 μ, respectively, and a depth of 30.
The values of μ are about 1.6% and about 30%, respectively, and the comparative example is remarkably higher than that of Example 3. The oxygen contents of Example 3 and Comparative Example are about 58 at a depth of 10 μm.
% And 92%, about 6% and 5 at 30μ depth respectively
1%, which is significantly higher than that in Example 3.

[0020]

As described above, according to the first aspect of the present invention, zirconia sol and zirconia are used as a mold coating agent on the surface of the substantially conical sprue recessed in the center of the upper end surface of the dental mold. Since it is a dental mold treatment method characterized by applying a mixture with powder, a film of a non-air-permeable zirconia layer is formed on the surface of the sprue, and this film raises the pressure of the feeder and makes it easier to cast. And the contact between the molten metal in the highest temperature state immediately after pouring from the crucible and the investment material on the sprue surface is prevented, and the reaction between the molten metal and the investment material is prevented. Therefore, an extremely high-purity cast product is obtained, and even when titanium that is easily oxidized at high temperature is cast with a mold made of silica, which is the most common investment material, the corrosion resistance and strength of titanium are not lost, There is no need to use expensive investment materials such as zirconia powder and alumina powder.

The second invention described in claim 2 is
Since it is a dental coating agent characterized by comprising a mixture of zirconia sol and zirconia powder, it can be used in the practice of the first invention to produce a highly pure dental casting.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a dental mold.

FIG. 2 is a vertical cross-sectional view of a conventional cast mold.

[Explanation of symbols]

 10: Decompression casting chamber 11: Boundary wall between pressure melting chamber and decompression casting chamber 12: Molten metal passage 13: Ring packing 14: Mold 15: Elevating mold stand 20: Mold 21: Gate 22: Spout 23: Cavity 24: Zirconia layer film

Claims (2)

[Claims] 1. A dental mold characterized in that a mixture of zirconia sol and zirconia powder is applied as a mold coating agent to the surface of a substantially conical sprue recessed in the center of the upper end surface of the dental mold. Processing method. 2. A dental coating agent comprising a mixture of zirconia sol and zirconia powder.