JPH0240962Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention is applicable to a denture base molding device, particularly when a denture base is molded from polymethyl methacrylate (hereinafter referred to as PMMA) resin using an injection molding machine.
This invention relates to a denture base forming device that can compensate for shrinkage that occurs during polymerization and solidification of PMMA.

<Conventional technology> PMMA has conventionally been used as a denture base material. For molding methods using such materials,
After dissolving PMMA powder in liquid methyl methacrylate (hereinafter referred to as MMA) monomer and making it into a rice cake shape, this was filled into a denture base forming space previously formed using plaster in a hollow space inside a pair of flasks, and then heated in boiling water or steam. The rice cake-like PMMA is polymerized and solidified by heating it to about 100°C to 130°C in a pressure cooker.
However, with this method, some of the liquid MMA monomer evaporates, and volume changes occur due to PMMA polymerization and hardening, causing shrinkage in the formed denture base, which may not match the jaw model formed with plaster. There are many. The shrinkage of PMMA above is usually about 1.8-2.0
%, PMMA weight approximately 0.2 per complete denture
It is about 0.3g. The above-described incompatibility of the denture base with the alveolar ridge due to shrinkage has become a problem in recent years, such as causing poor adhesion of the denture, tooth movement, or tenderness during mastication.

The above-mentioned shrinkage correction device when thermoplastic resin is used as the denture base material is, for example, disclosed in U.S. Pat.
No. 145609 and Utility Model Application Publication No. 58-145610, however, the method of filling a plaster mold with rice cake-like PMMA and then heating and polymerizing it cannot be applied to the apparatus disclosed in the above-mentioned publications. This is because if PMMA for shrinkage correction is heated or exists outside the flask, it will polymerize and solidify, making it impossible to correct for shrinkage.

<Problems to be solved by the invention> The present invention was made in view of the above-mentioned circumstances, and aims to correct the shrinkage by separately replenishing the space created by the contraction of the rice-cake-like PMMA with rice-cake-like PMMA. The present invention provides a denture base forming device that can obtain a denture base having a shape that perfectly matches the alveolar ridge.

The present invention also provides a denture base forming device that can inject and press-fit rice cake-shaped PMMA into a denture base forming space formed of plaster in a pair of compressed flasks using an injection molding method.

<Means for Solving the Problems> The present invention uses an injection molding method to mold the denture base forming space in the flask through the injection hole and the sprue hole of the sprue hole closing member formed of rubber fixed to the flask. In a denture base forming device that forms a denture base by injecting and press-fitting the mochi-like PMMA material, the sprue hole closing member is located inside the flask at the tip of the injection hole and has a tapered shape that prevents the backflow of the mochi-like PMMA. The formed backflow prevention valve consists of a space communicating with the outside formed around the injection hole on the inside of the flask, and the cake-shaped PMMA is press-fitted into the denture base preparation space and the sprue hole.
A replenishment section that is elastically crushed by the pressure of the above-mentioned closure member and enables replenishment of a predetermined amount of rice cake-like PMMA by the elastic compression force. It consists of a release valve that opens after the replenishment part is filled with rice cake-like PMMA.

<Operation> The nozzle of the injection molding machine is applied to the outer opening of the sprue hole closing member, and the rice cake-shaped PMMA is injected. Mochi-shaped
PMMA passes through the non-return valve of the closure member;
It passes through a sprue hole formed with plaster and is filled into the denture base formation space. When the denture base forming space and the entire sprue hole space are press-filled with the rice cake-like PMMA, the pressure of the rice cake-like PMMA increases, and the replenishing part is elastically deformed in response to this pressure. This elastic deformation region is further press-filled with rice cake-shaped PMMA. As the rice cake-like PMMA continues to be press-fitted into the flask through the nozzle, the elastic deformation of the replenishing part reaches its limit, and then the release valve opens without being able to resist the above pressure, and the rice cake-like PMMA is released from here to the outside. . After confirming this condition, the injection press-fitting of the mochi-shaped PMMA was stopped, and the injection pressure was kept equal to the internal pressure of the plaster mold and left for a while.
Wait for the backflow prevention valve to close.

After this operation is completed, the flask is heated in boiling water or a pressure cooker at a temperature of about 100°C to 130°C, and the polymerization and solidification reaction of the rice cake-like PMMA proceeds sequentially starting from the outer edge of the denture base (buccal side). The sparse area caused by the contraction is replenished by the elastic return of the replenishing part, which pushes out the mochi-shaped PMMA in this area. In this way, the shrinkage correction effect is achieved.

<Example> In FIGS. 1 to 3, numeral 1 denotes a sprue hole closing member, which is made of rubber having a hardness of about 80 to 90 according to the JIS standard. 2 is an injection hole, and the nozzle of the injection molding machine comes into contact with the opening at the left end in the figure. 3 is inside the flask, located at the tip of the injection hole, and has a mochi-like shape.
A tapered backflow prevention valve 4 that prevents backflow of PMMA is a cake-shaped PMMA replenishment part and has a space 5 inside. The space 5 has an air vent hole 18
It communicates with the outside via. The size relationship between the space outer wall thickness d and the space inner wall thickness D of the replenishing portion 4 is D
>d, therefore, the injection hole 2
The elastic strength of the surrounding wall portion is greater than the elastic strength of the outer circumferential wall of the replenishing part 4. 6 is a protrusion engaging portion that fixes the closing member 1 to the flask; 7 is a mochi-shaped PMMA
The discharge valve is formed by a notch reaching the injection hole 2 from the surface of the closing member 1. The elastic strength of this discharge valve 7 is greater than that of the replenishment part 4, and therefore the discharge valve 7 is designed to open after the elastic deformation of the replenishment part 4 reaches its limit. Incidentally, instead of the notch-shaped discharge valve 7, it may be formed of only a rubber pipe. In this way, when a predetermined pressure is reached, the opening of the injection hole 2 will expand, and the cake-like PMMA will come out.

FIG. 4 shows the flask 8 of the sprue hole closing member 1.
The groove 9 formed in the flask 8 shows how it is attached to the flask 8.
The protrusion engaging portion 6 is fitted into the closing member 1, and the closing member 1 is fixed to the flask 8. The check valve 3 and the replenishment part 4 are located inside the flask 8, and the discharge valve 7 is located outside the flask 8. The inside of the flask 8 is filled with plaster 10, and a denture base forming space 11 is formed in advance by the plaster 10. 12, 12... are artificial teeth embedded in plaster 10. The above denture base forming space 11
The wall surface conforms to the shape of the outer surface of the denture base.
13 is a sprue hole. 14, 14... are screw holes for tightening and fixing. Another flask 15, indicated by a broken line in the figure, is superimposed on the flask 8, and both are clamped together with bolts or the like through screw holes 14, 14, . . . . The other flask 15, like the flask 8 described above, is filled with gypsum, and a jaw model taken from the patient and a sprue hole are formed with the gypsum.

Next, the injection and press-fitting state of the rice cake-like PMMA will be explained step by step based on FIG.

(A) The nozzle 16 of the injection molding machine is brought into contact with the sprue hole closing member 1 fixed to the pair of clamped flasks 8 and 15, and the nozzle 16 of the injection molding machine
PMMA17 is injected. The mochi-shaped PMMA17
passes through the injection hole 2, opens the backflow prevention valve 3, and is press-fitted into the sprue hole 13. 10 and 10 are plaster.

(B) When the entire space of the denture base forming space 11 (Fig. 4) and the sprue hole 13 is filled with the sticky PMMA 17, the sticky PMMA inside the flasks 8 and 15
The pressure at 17 increases, and the space 5 of the replenishing part 4 is elastically deformed as if being crushed by this pressure.
In this way, the mochi-like PMMA is made even more by this deformation.
17 will be filled and replenished into the flasks 8 and 15. The amount of deformation of the replenishing part 4 is set in advance so that this amount of replenishment is the amount necessary to correct the shrinkage of the denture base (at least this amount if the amount of shrinkage is 0.2 g).

(C) When the elastic deformation of the replenishing part 4 reaches its limit and no further deformation occurs, the release valve 7 opens due to the increased pressure of the rice cake-shaped PMMA 17.
From here, the mochi-like PMMA17 is flask 8,1
5 released to the outside.

(D) Check the condition and manually shape the rice cake.
After gradually stopping the discharge drive of the PMMA 17 and leaving it as it is for a while to close the backflow prevention valve 3, the nozzle 16 is separated from the opening of the injection hole 2. In this way, the rice cake-like PMMA 17 is sealed in the flasks 8 and 15 while being subjected to the elastic compressive force by the replenishing part 4.

After that, the pair of flasks 8 and 15 are placed in boiling water or a pressure cooker while being clamped, and boiled for about 100 minutes.
Heated at ℃~130℃ for about 10 to 20 minutes. In this case, the flasks 8, 15 must be placed vertically, that is, with the sprue hole closing member 1 positioned at the upper end, and the lower portions of the flasks 8, 15 must be heated by immersing them in hot water. This is because, in order to correct the shrinkage that occurs during denture base molding, the refill portion 4 and the sprue hole 13 need to be polymerized and solidified last. still,
If the area around the replenishment part 4 and the sprue hole 13 is surrounded by a heat insulating material such as silicone rubber, the above-mentioned problem with the placement condition will not occur.

The temperature rises from the outer wall of the flasks 8 and 15 toward the inside, and the cake-like PMMA 17 becomes
It is polymerized and solidified from the peripheral part, that is, from the buccal side of the denture base. Due to the contraction that occurs at this time, the rice cake-like PMMA17
When the density becomes sparse, the elastic compressive force of the replenishing part 4 pushes out the mochi-shaped PMMA 17 in this part, and a new mochi-like PMMA 17 is released from the sprue hole 13 into the sparse space.
PMMA17 is replenished. In this case, of course, the elastic compressive force of the replenishing unit 4 is required to have a minimum strength sufficient to push out an amount of PMMA corresponding to the replenishment amount due to PMMA contraction. PMMA in the flasks 8 and 15, including the replenishment part 4 and the sprue hole 13.
After all 17 have polymerized and solidified, the flasks 8 and 15 are divided, the plaster is destroyed, and the artificial teeth 12, 12...
The denture base to which it is fixed is removed. Thereafter, the PMMA 17 in the sprue hole 13 is ground away.

<Effects of the invention> The denture base forming device according to the invention has a mochi-like PMMA
When polymerizing and solidifying in a heated atmosphere to form a denture base, a replenishing part with elasticity is formed, and the structure is such that the cake-like PMMA is replenished into the denture base forming space. The deformation is corrected by the contraction that occurs during polymerization, making it possible to obtain a denture base with a shape that perfectly matches the alveolar ridge.

In addition, the present invention provides a mochi-shaped sprue hole closing member.
Since it has a PMMA backflow prevention valve, replenishment part, and discharge valve, it is molded into a rice cake shape by an injection molding machine.
During the injection press-fitting process of PMMA into the flask, it is possible to simultaneously replenish the replenishment section with mochi-shaped PMMA.
Moreover, it is possible to confirm that the optimum amount of rice cake-like PMMA is filled into the flask, and it is highly effective when used in conjunction with an injection molding machine.

[Brief explanation of the drawing]

1 is a perspective view showing a sprue hole closing member according to an embodiment of the present invention, FIG. 2 is a right side view of the sprue hole closing member shown in FIG. 1, and FIG.
FIG. 4 is a perspective view of the embodiment, and FIGS. 5A, B, C, and D are sectional views for explaining changes in shape of the sprue hole closing member at each stage of the injection operation. be. 1... Sprue hole closing member, 2... Injection hole, 3
... Backflow prevention valve, 4 ... Replenishment section, 5 ... Space, 6
... Protrusion engaging portion, 7 ... Release valve, 8, 15 ... Flask, 10 ... Plaster, 11 ... Denture base formation space, 12, 12 ... ... Artificial tooth, 13 ... Sprue hole, 16 ... ...Nozzle, 17...Mochi-shaped PMMA.

Claims (1)

[Scope of utility model registration request] The molding material in a plastic state is introduced into the denture base forming space made of plaster in a pair of pressed flasks through the injection hole and sprue hole of a sprue hole closing member made of rubber and fixed to the flask. In a denture base forming device that forms a denture base by injection press-fitting, the sprue hole closing member is a tapered backflow member located inside the flask and at the tip of the injection hole to prevent backflow of the molding material. A blocking valve, and a space formed inside the flask and communicating with the outside around the injection hole, and is elastically crushed by the pressure of the molding material press-fitted into the denture base forming space and the sprue hole. is,
A replenishment part that enables replenishment of a predetermined amount of molding material by its elastic compressive force, and a notch located on the outside of the flask that reaches the injection hole from the surface of the closing member, the replenishment part being refilled with the molding material. 1. A denture base molding device comprising: a molding material release valve that opens after completion of molding.