JPH0761880B2 - Mold for molding calcium phosphate-based crystallized glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold for molding calcium phosphate-based crystallized glass,
In particular, the present invention relates to a molding die capable of preventing bubbles from being generated on the surface or inside of the calcium phosphate crystallized glass.

(Prior Art) Calcium phosphate-based crystallized glass has good affinity with living organisms and has physical properties similar to those of natural teeth. Also, calcium phosphate-based glass is melted and cast using a mold, and then crystallized. Since it can be formed in the same manner as metal by the method, its application as a dental material has been proposed.

In general, as a casting mold for dental metal, since the molten metal (hot water) needs only to enter the casting part of the casting metal part, it is not necessary to consider the shape, and it is usually just a cylinder. It was provided as a void.

However, when such a casting mold is used for calcium phosphate-based glass, during the subsequent crystallization treatment, some bubbles are observed on the surface and inside of the molded product, which causes the shape to be damaged or broken. There is a drawback of.

The present inventor eliminates such drawbacks, and as a result of various studies and studies to obtain a calcium phosphate-based crystallized glass that does not generate bubbles, as a result, crystallization of the crystallized glass occurs from the surface and proceeds toward the inside at a fairly uniform speed. However, since crystallized glass has a higher density than ordinary glass, it has been found that voids are generated in the portion where crystallization last occurs due to shrinkage due to crystallization, and these remain as bubbles.

Based on this knowledge, when a calcium phosphate-based crystallized glass molded body is already obtained by the casting method as a means of creating a cavity in a portion other than the molded body, the diameter of the sprue wire (runner) of the mold is set to the thickness of the glass molded body. It was proposed in JP-A-61-71044 to make it larger to cause the final crystallization.

(Problems to be Solved by the Invention) The method proposed above is certainly an effective means, and there is no problem as an ordinary method for producing this seed crystallized glass.

However, in the case of calcium phosphate-based crystallized glass, the main crystal phase is calcium metaphosphate crystal, and the crystal forms thereof are β crystal and δ crystal, and crystallization is usually performed in the coexistence of these.

Further, in the case of such crystallized glass, it is desirable to make more β crystal in order to obtain glass having water resistance and a transparent appearance. And it is effective to allow the presence of fine crystals of calcium metaphosphate on the surface of the mold in contact with the glass as a means for achieving this, and to make the diameter of the runner of the proposed mold larger than the wall thickness of the glass molding together with this. It was found that, when used in combination, a cavity may unexpectedly occur in the molded body, and merely increasing the sprue wire diameter is not sufficient to prevent the cavity.

(Means for Solving Problems) The present invention has been made based on such findings, and by forming a basin at a specific location of the runner of the mold, a molded product can be obtained even if a mold having calcium metaphosphate on its surface is used. It was found that it did not create a cavity in it.

Thus, the present invention is a mold for casting and molding a calcium phosphate-based molten glass and crystallizing it before demolding to obtain a calcium phosphate-based crystallized glass dental crown material, and a runner leading to a cast molding part of the mold. Another object of the present invention is to provide a mold for molding calcium phosphate-based crystallized glass, characterized in that a spherical pool having an inner diameter of 5 mm or more is provided within 20 mm from the molding part.

The present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a sectional view for explaining the basic structure of a mold for molding calcium phosphate-based crystallized glass according to an example of the present invention. In FIG. 1, 1 is a forming part for forming a cast formed product such as a tooth, and 2 and 3 are runners into which a calcium phosphate-based glass melt (melt) is cast into the forming part 1. Reference numeral 4 denotes a basin provided between the runners 2 and 3, and the basin of the basin is measured at a lower portion of the forming part 1, that is, a contact point between the runner 2 and the basin 2 and is directed downward within 20 mm. It is provided so that the top comes, that is, the portion indicated by a in FIG. 1 has a maximum of 20 mm.

The part indicated by a has a maximum of 20 mm, preferably 10 mm
Hereafter, it is especially 5 mm or less, and it is also possible to provide a face-to-face contact with the lower part of the molding part 1.

If the position where the basin is provided exceeds 20 mm, it is unavoidable that cavities occur in the molded product, which is unsuitable. The basin should be spherical with an inner diameter of 5 mm or more. The volume of the basin is preferably less than 10 times the volume of the molded body.

The shapes of the runner 3 and the pouring port 5 are not particularly limited as long as the molten glass can flow into the molding portion 1 and molding can be performed, but in order to facilitate the inflow of the molten glass, the inner diameter thereof is 0.5 mm or more, preferably 1
mm or more is suitable.

On the other hand, it is preferable that the runner 2 is directly connected to the maximum thickness part of the forming part 1, and the inner diameter of the runner 2 is preferably at least the same as or larger than the maximum thickness part of the forming part 1. By doing so, it becomes possible to sufficiently suppress the generation of voids in the molded body. If the compact is a crown material, runner 2
The inner diameter of is 2 mm or more, preferably 3 mm or more.

As a material constituting such casting, for example, a phosphate-based investment material, an ethylsilicate-based investment material, a gypsum-based investment material, or the like can be appropriately adopted, and in particular, the surface of the molding part 1 has fine crystals of boron nitride and calcium metaphosphate ( (Usually 100 μm or less) is preferable. By doing so, crystallization of the molded body, particularly growth of β crystal, is remarkable, and mold release can be facilitated.

Boron nitride should be present in an amount of 1 to 80% by weight from the surface of the mold to approximately 10 μ to 1 mm, and fine crystals of calcium metaphosphate should be present in an amount of approximately 1 to 50% by weight by approximately 10 μ to 1 mm from the surface of the mold. Is effective.

The mold is usually a buried system such as the Lost Wax method, but other types such as a split mold may be used.

The calcium phosphate-based glass used in the present invention is preferably one in which calcium metaphosphate crystals are precipitated as a main precipitation crystal phase. For example, those containing 80% by weight or more of calcium phosphate having an atomic ratio Ca / P of calcium to phosphorus of 0.35 to 0.7 are preferable.

In the present invention, in order to cast a calcium phosphate-based crystallized glass, for example, glass melted at 1000 ° C. or higher is cast into a mold by utilizing centrifugal force or a pressure difference of atmosphere, and after molding into a predetermined shape, in a mold. And then to 700 ° C 4
A method is employed in which crystallization is carried out by holding for a period of time, and then demolding is performed.

The mold according to the present invention is effective when calcium metaphosphate crystals are allowed to exist on the surface of the molded part to control and promote crystallization, but it is also effective for molds in which such a control accelerator does not exist. It goes without saying that it has the effect of not causing voids in the molded body.

(Example) Example 1 A mold having the shape shown in FIG. 1 was prepared as follows.

2 mm diameter on a conical rubber stand with an outer diameter of 30 mm and a height of 10 mm
Wax stick (Lady-Casting Wax manufactured by Meta Dental Industry Co., Ltd.) cut into a length of 5 mm, 3 is set up, and a wax ball 4 formed in a spherical shape with a diameter of 8 mm on the upper side (manufactured by Meta Dental Industry Co., Ltd.) Ready-casting wax)
In addition, a wax rod 2 with a diameter of 3 mm (same wax produced by Dojo Co., Ltd.) is cut up to a length of 5 mm on the upper portion thereof, and a crown-shaped wax pattern with a maximum wall thickness of 1.8 mm is formed on the upper portion thereof at the maximum wall portion. I installed it. And around it, the inner diameter is 30 mm and the height is 50 mm.
A stainless steel ring was placed. On the other hand, 30% by weight boron nitride powder, calcium metaphosphate crystals with an average particle size of 5μ
20% by weight, and the balance was a phosphate-based investment material (Blue vest manufactured by Tokuyama Soda Co., Ltd.) was sufficiently mixed, and it was made to flow into the ring in the form of slurry according to a conventional method, and was left until it was cured.

After that, the rubber base was removed, and the wax was incinerated by heating at 800 ° C. for 30 minutes to obtain a mold.

Next, CaO 24.5% by weight, P ₂ O ₅ 74.5% by weight, Al ₂ O
₃ 1.0% by weight of the composition was melted at 1250 ° C. to obtain a calcium phosphate glass, and the glass was centrifugally cast into the mold according to a conventional method. Then, the mold was kept at 700 ° C. for 2 hours to crystallize the glass in the mold.

After cooling to room temperature, the mold was broken and the crystallized glass was taken out, and the crown molding was cut at the interface with the runner.

In the same manner, a total of 10 crowns were created and inspected by the X-ray flaw detection method, respectively, and no cavity was found in any of them.

When the pool of water was observed in the same manner, large and small cavities were observed in the crystallized glass.

Comparative Example 1 A wax stick having a diameter of 3 mm cut into a length of 10 mm was erected on a conical rubber stand similar to that of Example 1, and a crown having the same crown shape as that of Example 1 was placed above the wax stick. Attached the pattern. Thereafter, burying, casting and crystallization were performed in the same manner as in Example 1 to obtain a total of 10 crystallized glass crowns, which were inspected by the X-ray flaw detection method. As a result, two had cavities that penetrated to the surface and the rest had cavities of 0.3 to 1.8 mm.

Examples 2 to 6 and Comparative Examples 2 to 6 In order to obtain a crystallized glass molded body having a disk shape (volume 265 mm ³ ) having a thickness of 1.5 mm and a diameter of 15 mm, a wax plate having the same shape was prepared, As shown in Fig. 2 and Table 1, the runners each having the shape shown in Fig. 2 were attached so that the angle was 30 degrees, and each of them was buried, cast, and crystallized in the same manner as in Example 1, and the crystallized glass plate was attached to each of them. I got 10 each.

Table 1 shows the result of the inspection conducted in the same manner as in Example 1.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining the basic structure of a mold for molding calcium phosphate-based crystallized glass according to an example of the present invention, and FIG. 2 is a calcium phosphate-based crystallization for showing examples and comparative examples of the present invention. It is sectional drawing for demonstrating the shaping | molding die of glass. 1,21: forming part, 2,3,22,24: runner, 4,23: hot water pool

Claims (3)

[Claims] 1. In a mold shape for obtaining a calcium phosphate crystallized glass crown material by casting and molding calcium phosphate-based molten glass and crystallizing it before demolding, a runner leading to a casting molding part of the mold. 1. A mold for molding calcium phosphate-based crystallized glass, characterized in that a spherical basin having an inner diameter of 5 mm or more is provided at a position within 20 mm from the molding part. 2. The molding die according to claim 1, wherein the length of the runner connecting the casting molding portion of the mold and the molten metal pool is 15 mm or less. 3. The molding die according to claim 1, wherein the cast molding portion of the mold has crystals of calcium metaphosphate on its surface.