JP2000083973A - Crucible former for dental technique - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve castability when a high melting metal is used. SOLUTION: A body part 6 apart from the apex 5 of a setting base 4 of a conical shape is provided with an insertion hole 9 for mounting a sprue line to a crucible former 1. When a casting mold is manufactured by fixing the other end of the sprue line fixed with a casting prototype at one end to this insertion hole 9, the sprue of a runner through which a cavity part formed in correspondence to the casting prototype and the crucible formed in correspondence to the attachment base 4 communicate with each other exists at a position higher than the lowest part (apex) of the crucible. Even if, therefore the molten metal poured into the crucible is solidified by cooling near the lowest part at the time of casting, the molten metal maintains a high flow property at the sprue and flows smoothly into the cavity part via the runner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dental craft crucible for forming a dental prosthesis such as an inlay, a crown (metal crown), a metal floor, an implant, and an implant superstructure with a noble metal or a non-noble metal. The present invention relates to a former (generally referred to as a “frustum of cone”), and more particularly, to a dental crucible former suitable for using a refractory metal as a prosthetic material.

[0002]

2. Description of the Related Art Loss of a part or anterior tooth due to caries (cavities), periodontal disease, etc., not only causes a decrease in mastication and pronunciation functions, changes in appearance, but also adversely affects health. It is therefore important to treat early and repair missing teeth. As a method of this restoration, a method of replacing a defective portion with a metal casting is widely used. The morphology of the teeth differs from individual to individual, and the size and morphology of the missing part are not uniform. Therefore, in dental treatment, it is not possible to mass-produce a prosthesis to compensate for a lost site, and it is necessary to create a prosthesis having a different shape depending on the case of each individual. Further, in order to obtain an accurate occlusion, it is necessary to prepare a prosthesis with high accuracy. In order to obtain a casting that satisfies these requirements, in the field of dental casting, a lost wax method is generally used, which enables high-precision casting.

FIG. 6 is a flowchart showing a series of steps of dental casting by the lost wax method. With reference to this figure, a procedure for producing a prosthesis in dental treatment will be described.

[0004] First, a dentist or the like molds (takes an impression) according to the shape of the mouth and teeth of a patient (step S1), and casts a model material such as gypsum into the negative impression. Then, a positive model is prepared by hardening (step S2). Next, a casting mold (wax pattern) is formed of wax or a resin material on the model according to each purpose such as an inlay and a crown (step S3).
Then, a sprue wire for forming a runner is attached to an appropriate location of the casting mold using wax or the like (step S4). Thereafter, the casting prototype is removed from the model, and one end of the sprue wire is planted on a rubber crucible former (step S5).

FIG. 7 is an external front view showing a state in which a casting mold is erected on a conventional general crucible former. A substantially conical planting stand 31 is formed at the center of the crucible former 30, and an insertion hole 32 for inserting a sprue wire is provided at the top. The insertion hole 32 is filled with wax softened by heating, and the other end of the sprue wire 34 to which the casting mold 33 is fixed is inserted at one end, whereby planting can be performed.

[0006] Further, FIG.
A cylindrical casting ring is fitted into the crucible former shown in (1), and an investment material such as gypsum or a phosphate system is poured into the casting ring to immerse the casting mold in the investment material (step S6). After curing the investment, the crucible former is removed and the investment is heated. Then, the sprue wire and the wax buried in the inside are incinerated, and the portion corresponding to the casting prototype remains as a hollow portion to complete the mold (step S7).

[0007] The mold is heated to a predetermined temperature, and a metal melted by heating is poured into a crucible (inverted conical depression) formed according to the shape of the planting stand of the crucible former, and the sprue wire is formed. The so-called casting is performed by pouring the molten metal into the internal cavity through a runner which is a tubular cavity to be cast (step S8). And
When the cast metal has cooled and solidified, the investment material is broken and the internal casting is taken out (step S9), unnecessary parts such as the solidified metal are removed along the runner, and the surface of the casting is further polished. (Step S)
10) The prosthesis is completed.

In order to smooth the flow of the molten metal into the cavity during casting, the following three types are generally used. The first is a centrifugal casting method in which the molten metal is pushed into the inside of the mold by the action of centrifugal force by rotating the mold. Second, the molten metal is stored in a crucible after the surroundings are once evacuated and immediately thereafter. A pressure casting method in which molten metal is poured by utilizing the pressure difference between the cavity and the outside by pressing, and a third method is a suction casting method in which the molten metal is poured cruciblely and sucked and cast from the opposite surface. is there.

The pressure casting method will be described in detail. First, the pressure inside the cavity of the mold is reduced by reducing the pressure in the casting chamber in which the mold is disposed by a vacuum pump. 800-9 molds
Heat to a high temperature of about 00 ° C., heat and melt the metal above it, pour it into the crucible of the mold and store it. At this time, since the entrance of the runner, that is, the gate, is closed, the inside of the cavity is kept at a low pressure. Immediately thereafter, when a compressed gas or the like is fed into the casting chamber and pressurized, the molten metal flows into the cavity through the runner due to the differential pressure.

[0010] In this casting method, if the pressure is applied before the molten metal is sufficiently stored in a crucible manner, the air or other inert gas used for the pressurization enters the hollow portion, resulting in casting defects. Is generated. To prevent this, it is desirable to apply pressure after a sufficient amount of molten metal has accumulated in the crucible.

[0011]

However, when a high melting point alloy (usually 1000 ° C. or higher) such as a nickel-chromium alloy or a cobalt-chromium alloy is used as a casting material, the following problems arise. there were. Even if the investment of the mold is for high-temperature casting such as a phosphate investment,
The temperature can only be raised up to about 00 ° C.
For this reason, since the temperature of the mold is lower than the melting point of the molten metal, the molten metal poured into the mold crucible may be cooled and solidified before being pressurized. In addition, even if it does not solidify, the fluidity is reduced and casting cannot be performed smoothly, and casting defects or insufficient casting may occur.

In this case, if the melting temperature of the metal is set to a higher temperature, the time until the metal is solidified after being poured into the mold is increased, and the castability is increased. However, when the temperature is extremely high, the molten metal reacts with the investment material of the mold to make the surface of the casting rough, that is, a so-called rough surface or a rough surface, and it takes time for a post-process such as polishing. Also,
It may also affect properties such as hardness and toughness of the metal in the casting.

The present invention has been made in order to solve such a problem, and an object of the present invention is to perform casting with high castability even when a high melting point metal is used as a material of a casting. An object of the present invention is to provide a crucible former for a dental technician for producing a mold capable of forming a mold.

[0014]

Means for Solving the Problems and Embodiments of the Invention According to the present invention, there is provided a crucible former for dental technology according to the present invention, wherein one or a plurality of positions are provided on the abdomen of a cone-shaped planting stand. The sprue wire mounting portion is provided.

That is, in the crucible former according to the present invention, as shown in FIG. 7, a sprue wire attaching portion for fixing a sprue wire is not provided at the position of the top of the planting table. A sprue wire mounting part is provided on the inclined surface of the abdomen lowered (about several mm). The sprue wire mounting portion may be formed as a hole so that one end of the sprue wire can be easily inserted and fixed, or a fine surface may be used to improve the sticking property of the wax for attaching the sprue wire. The surface may have irregularities.

When a mold is manufactured using such a crucible former, the gate is formed not on the tip (bottommost portion) of the cone-shaped crucible but on an inclined surface at a position higher than the tip by a predetermined distance. When a molten metal made of a high melting point metal is poured into this crucible, the first poured metal reaches the tip of the crucible, and the surface in contact with the surrounding investment material is deprived of heat and solidified fastest. However, the molten metal poured from the top after that has a large heat capacity and is hard to solidify because a high temperature is maintained. Therefore, high fluidity of the molten metal is maintained near the gate, and the molten metal flows smoothly into the runner by pressurization and fills the cavity.

When a metal having a relatively low melting point is used as the casting material, the temperature difference between the melting point and the mold is small or the temperature of the mold is higher, so that the molten metal solidifies even at the tip of the crucible. Does not occur. Therefore, in the crucible former for dental technology according to the present invention, if a structure is also provided in which a sprue wire attaching portion is provided also on the top of the planting table, when a high melting point metal is used, the abdominal sprue wire attaching portion, a low melting point metal Can be used properly, such as a sprue wire mounting portion at the top.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a crucible former for dental technology according to the present invention. FIG.
(A), (b), and (c) are a top view, a front view, and an oblique side view as viewed from the direction of arrow A showing the appearance of the crucible former of the present embodiment.

In this crucible former 1, a cylindrical wall 3 is provided upright around a disk-shaped substrate 2, and a substantially conical planting stand 4 is formed at the center of the substrate 2 in a raised state. The planting table 4 has a peripheral surface formed by rotating an upwardly swelling curve around a center line extending vertically from the substrate 2 at the outermost periphery, and the peripheral surface is flat from the substrate 2. The top 5 has been reached. In addition, the peripheral surface has a rotation angle of 1 around the top 5.
It forms an abdomen (three places) 6 which is depressed with a curved surface inside at a position of 20 degrees. The bottom side of the abdomen 6 forms a substantially flat step 7 which is higher than the upper surface of the base 2 by a predetermined height. One of the top 5 and the abdomen 6 has a cylindrical top insertion hole 8 and an abdomen insertion hole 9, each of which is open, and these holes 8 and 9 communicate with each other.

Since the crucible former 1 needs to have both appropriate elasticity and wear resistance, it is an integrally molded product made of, for example, nitrile rubber (NRB). Of course, it is also possible to mold using other materials.

Next, the crucible former 1 of the present embodiment.
A method of performing casting of an inlay or the like by using (steps corresponding to steps S4 to S8 in FIG. 6) will be described with reference to FIGS. Here, nickel and nickel
A high melting point alloy such as a chromium alloy is used.

FIG. 2 is a cross-sectional view showing a state in which a casting mold is implanted in the crucible former of this embodiment and a casting ring is fitted thereto. FIG. 3 is an example of a mold manufactured using this crucible former. FIG. 4 is an end view showing a state when casting is performed using this mold.

An operator (for example, a dental technician) fills the abdomen insertion hole 9 (and the top insertion hole 8) of the crucible former 1 with the wax 14 softened by applying heat, and fixes the casting mold 12 at one end. Wax (or synthetic resin material)
The other end of the sprue wire 13 is inserted into the abdominal insertion hole 9 and fixed while heating and melting with an appropriate tool. When the wax 14 cools and hardens, the casting mold 12 is fixed to the planting table 4 of the crucible former 1 via the sprue wire 13 as shown in FIG.

Next, a cylindrical casting ring 10 made of metal is used.
Into crucible former 1. Since the inner diameter of the cylindrical wall 3 of the crucible former 1 is slightly smaller than the outer diameter of the casting ring 10, the cylindrical wall 3 is fitted into the open end face of the casting ring 10, and the end of the cylindrical wall 3 contacts the base 2. When the cylinder is pushed in until it contacts, the cylindrical wall 3 presses the casting ring 10 from the outer peripheral side with an appropriate force, and both are firmly fastened. The inner peripheral surface of the casting ring 10 is lined with an asbestos ribbon 11 made of ceramic fiber or the like in order to absorb the thermal expansion of the investment material when the mold is heated.

Then, as shown in FIG. 2, the investment material is poured from the upper open end face of the casting ring 10 while the crucible former 1 is arranged on the lower side, and is filled to the vicinity of the open end face. As the investment material, for example, a phosphate investment material may be used for high-temperature casting.

After leaving the investment material in the casting ring 10 for a predetermined time to cure, the crucible former 1 is removed.
Then, the mold is housed in an electric furnace and heated to incinerate the sprue wire 13 and the casting mold 12. As a result of the heat incineration, as shown in FIG. 3, a mold having a cavity 16 in the shape of a casting mold is formed inside the cured investment material 15. A substantially conical crucible 1 corresponding to the shape of the planting table 4 of the crucible former 1 is provided on the upper part of the mold.
7 is formed, and the inclined surface on the inner periphery of the crucible 17 and the cavity 16 are connected by a runner 18 corresponding to the shape of the sprue wire when buried.

On the other hand, in order to melt the metal with a reversing casting machine for pressure casting, a necessary amount of a casting material (nickel-chromium alloy) is accommodated in a dedicated crucible, and heated by means such as an arc, a high frequency wave or a heater. Increase the temperature to dissolve. If melting is confirmed, the heat-incinerated mold as described above is quickly set at a predetermined position (below the crucible) in a casting chamber (not shown) while the temperature is high. Reduce pressure by pump. At this time, the temperature of the mold is 800 to 900.
℃, on the other hand, the temperature of the molten metal is 1300-1400 ℃
It is about.

When the pressure in the casting chamber is reduced, the cavity 1
The pressure in 6 also drops. Immediately thereafter, as shown in FIG.
At a predetermined timing, the crucible 19 is inverted and descends to the upper part of the mold. When the crucible 19 descends vertically, the edge of the open end surface of the crucible 19 comes into contact with the peripheral flat portion 20 of the crucible 17 formed corresponding to the step 7 of the crucible former 1. At this time, in the portion of the upper end peripheral portion of the crucible 17 where the peripheral flat portion 20 is not formed (that is, the portion that does not correspond to the abdomen 6 in the crucible former 1), the edge of the crucible 19 and the inner peripheral surface of the crucible 17 are There is a gap between them.

When the crucible 19 is inverted, the liquefied metal 2
1 flows down and accumulates in the crucible 17. Investment 15
Since the temperature of the molten metal itself is about 900 ° C. at the highest, the molten metal that first flows into the crucible 17 is quickly taken away when it comes into contact with the investment material 15. For this reason, in the vicinity of the bottom of the crucible 17, the temperature of the metal falls below its melting point, and it may start to solidify as indicated by reference numeral 22 in FIG. However, in the upper layer, the degree of cooling of the metal is lower and the high temperature is maintained, so that the metal is in a molten state. At this time, the entrance of the hot spring 18 (gate)
Is closed by a molten metal, and the cavity 16 is sealed with a low pressure.

When a predetermined time has passed since the crucible 19 was inverted, compressed gas is supplied to the casting chamber to perform pressurization. As described above, the edge of the open end face of the crucible 19 and the crucible 17
The compressed gas flows into the crucible 17 through the gap as shown by the arrow B in FIG. At the time of pressurization, crucible 19
The entire amount of metal melted in the crucible 17 flows into the crucible 17. When a force acts on the molten metal from above by pressurization, the differential pressure between the high pressure on the crucible 17 side and the low pressure in the cavity 16 causes Molten metal flows smoothly into cavity 16 through 18. At this time, the flow of the molten metal may be promoted by vibrating the mold.

As described above, since the gate is located at a position higher than the lowest portion of the crucible 17, even if some metal is solidified at the lowest portion, or even if the metal does not solidify, the viscosity decreases and the fluidity deteriorates. Even so, the molten metal maintains high fluidity near the gate. For this reason, the molten metal can be reliably fed into the cavity 16 without being affected by solidification in the lower layer, and the molten metal can be spread evenly in the cavity 16. as a result,
There is no danger of insufficient casting, and casting defects can be prevented.

When a low melting point metal (such as about 1000 ° C. or less) such as a silver-palladium-gold alloy is used, there is no possibility of solidification in the crucible 17 as described above. The sprue wire 13 may be inserted into the top insertion hole 8 when planting the crucible former 1. According to this, in the mold as shown in FIG. 3, it is possible to form a runner that hangs almost straight from the bottom (tip) of the crucible 17.

In the above embodiment, the insertion hole is formed for attaching the sprue wire to the crucible former. However, other structures may be used as long as the sprue wire can be stably fixed. FIG. 5 is an enlarged detailed view showing a structure of a sprue wire mounting portion that replaces the top insertion hole and the abdomen insertion hole of the planting table 4, and shows a portion corresponding to the vicinity of the top portion 5 in FIG. It is. In this example, the planting stand 4
A plurality of projections are formed at predetermined portions of the top 5 and the abdomen 6 (reference numerals 80 and 90). When the unevenness is provided on the surface constituting the planting table 4 in this manner, the wax attached to the end of the sprue wire enters the concave portion, and the wax is difficult to peel off. Therefore, one end of the sprue wire can be fixed.

The above embodiment is merely an example, and it is apparent that changes or modifications can be appropriately made within the scope of the present invention.

[0035]

As described above, in the crucible former for dental technology according to the present invention, the sprue wire attaching portion is provided on the abdomen of the planting table. A gate is formed on an inclined surface at a position higher than the lowermost portion (tip portion) of the shaped crucible. Therefore, upon casting, even if the molten metal poured into the crucible is deprived of heat by the investment material constituting the crucible and solidification or fluidity is significantly reduced near the bottom, even near the gate in the upper layer than that In this case, since the high fluidity of the molten metal is maintained, when the pressure is applied, the molten metal flows smoothly through the runner into the internal cavity. Therefore, occurrence of casting defects can be prevented.

If a sprue wire mounting portion is provided also on the top of the planting table, when a low-melting-point metal which does not have a risk of solidification of the molten metal is used as a casting material, the crucible can be formed as in the conventional case. A runner that hangs straight down from the bottom (tip) can be formed. Such a runner has a lower resistance and is shorter, so that the molten metal can easily pass through and the castability is higher. Further, the sprue wire can be easily erected and workability is good. Furthermore, low melting point metals are generally expensive because of the large amount of noble metals, but if the bottom of the crucible is a gate, there is no waste of metal.

[Brief description of the drawings]

FIG. 1 is a top view (a) and a front view (b) showing the appearance of a cruciable former for dental technology which is an embodiment of the present invention.
And an oblique side view seen from the direction of arrow A (c).

FIG. 2 is a cross-sectional view showing a state in which a casting mold is erected and a casting ring is fitted to the dental craft crucible former of the present embodiment.

FIG. 3 is an end view showing an example of a mold manufactured using the crucible former for dental technology of the present embodiment.

FIG. 4 is an end view showing a state when casting is performed using the mold of FIG. 3;

FIG. 5 is an enlarged detailed view showing a structure of a sprue wire mounting portion according to another embodiment.

FIG. 6 is a flowchart showing a series of steps of dental casting by the lost wax method.

FIG. 7 is an external front view showing a state where a casting prototype is erected on a conventional general crucible former.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Crucible former 2 ... Disk-shaped base material 3 ... Cylindrical wall 4 ... Planting stand 5 ... Top 6 ... Abdomen 7 ... Step 8 ... Top insertion hole 9 ... Abdomen insertion hole 10 ... Cast ring 12 ... Casting mold 13 ... Sprue line

Claims (4)

[Claims] 1. A crucible former for dental technology, wherein one or more sprue wire mounting portions are provided on the abdomen of a cone-shaped planting stand. 2. The crucible former for dental technology according to claim 1, wherein the sprue wire mounting portion is a hole into which a sprue wire can be inserted. 3. The crucible former for dental technology according to claim 1, wherein the sprue wire mounting portion is a surface having fine irregularities on the surface. 4. The crucible former for dental technology according to claim 1, wherein a sprue wire mounting portion is provided also on a top portion of the planting table.