JPH0226503B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method of manufacturing a denture base using a thermoplastic resin, which enables good molding with simple equipment. Prior Art For many years, conventional resin denture bases have been produced using acrylic resins by pressure molding by heating polymerization of polymers and monomers. This method has the advantage of being easy to handle and requiring no complicated processes, so it is inexpensive in terms of equipment. However, the denture base obtained by heating polymerization of such acrylic resin is brittle, and the thin part often breaks due to occlusal force, as well as being weak in strength.
Since the heating polymerization reaction is often insufficient, residual monomers may be eluted and cause allergic symptoms, which is a hygienic drawback. Therefore, in order to eliminate such drawbacks, injection molding of polysulfone resin using a plaster mold has been proposed and has come into practical use. However, with this injection molding method, high viscosity polysulfone resin must be injected into a predetermined denture base-shaped cavity in just the right amount, and excessive injection pressure or holding pressure may cause damage to the plaster mold or damage to the denture. Generates residual strain in floor moldings. Therefore, in order to systematically obtain good molded products, extremely strict temperature control, pressure control, injection speed control, etc. are required, which has the disadvantage that the molding machine becomes extremely large and expensive. It was hot. Problems to be Solved by the Invention It is an object of the present invention to provide a method of manufacturing a denture base that can stably obtain a good denture base using a thermoplastic resin and with simple equipment, which can eliminate such conventional drawbacks. It is. In other words, thermoplastic resins such as polysulfone are used instead of conventional acrylic resins, which are concerned about the elution of residual monomers, and they are easy to handle and require less expensive equipment than injection molding. The present invention provides a denture base manufacturing method that does not require upsizing and allows molding at low equipment costs. Means for Solving the Problems The present invention is characterized in that a mold consisting of an upper and lower flask having a desired denture base-shaped cavity therein is opened vertically to create a slight gap between both flasks. A container containing one bed of heat-softened thermoplastic resin is placed below the bottom injection port of the lower flask, and the container is pressed and crushed by the lower flask, thereby transferring the resin to the lower flask. After injecting into the flask through the inlet, the upper and lower flasks are pressed together. In the present invention, there is no particular restriction on the method of providing a desired denture base-shaped cavity inside the upper and lower flasks.
That is, in accordance with a conventional method, a so-called lost wax method is applied, in which a wax denture made of paraffin is embedded in plaster in upper and lower flasks, heated and softened, and then the paraffin is removed. In the present invention, there is no particular restriction on the method of arranging the upper flask and lower flask with a slight gap between them. For example, if a plate spring or coil spring is placed between the upper flask and the lower flask, and the upper and lower flasks are not pressurized, a gap will be formed between the upper and lower flasks due to the elasticity of the plate spring or coil spring, and the softened resin will flow into the flask. When the upper and lower flasks are pressurized after being injected into the container, the applied force exceeds the elasticity of the plate spring, coil spring, etc., and the upper and lower flasks are pressed together and brought into close contact. The gap between the upper flask and the lower flask is arbitrarily selected depending on the size of the denture base to be molded, but it is usually preferably about 0.5 to 5 mm, but it is important to ensure that the softened resin can fit easily into the cavity and that the resin can be cooled. A thickness of 1 to 3 mm is particularly preferable because the best molding condition can be obtained from the balance of viscosity increase, etc. In the present invention, there is no particular restriction on the container that accommodates one bed's worth of thermoplastic resin. It is sufficient to crush the container with the lower flask and inject the thermoplastic resin into the flask. Therefore, the container may be arbitrarily selected to have a cylindrical shape, a box shape, etc., but for example, a cylindrical shape may have a wall thickness of 0.05 to 1 mm. degree, diameter 20~50mm, depth 20~80mm
A diameter of approximately mm is selected depending on the size and shape of the intended denture base. There are no restrictions on the method of heating and softening the thermoplastic resin in the container, but it is possible to soften the thermoplastic resin in powder form.
It is made into granules, plates, etc. and stored in the container, and dried in an electric furnace, hot air circulation dryer, etc. depending on the type of resin.
Softens between ~400℃. A plate-shaped molded product is preferably used because it is difficult for air to be trapped between the molded products due to softening. In the present invention, the lower flask is usually made of metal such as brass or aluminum, with a hole in the bottom for resin injection and a plaster mold embedded inside, but the metal bottom plate is not necessarily used. It does not need to be attached, and the lower plaster mold equipped with a resin injection port directly presses the container containing the softened resin, crushes the container, and pours the resin into the denture base-shaped cavity in the upper and lower flasks. It is also possible to inject. There is no particular limitation on the method of pressing the upper and lower flasks together after the softened resin is injected into the flask. For example, the upper flask or the lower flask is actuated by hydraulic drive, resisting the elasticity of a spring such as a plate spring or a coil spring interposed between the upper and lower flasks, and further spreading the softened resin injected into the flask. A method of pressurizing and bringing the upper and lower flasks into close contact is applied. It is also possible to apply a method in which the upper or lower flask is driven by an electric motor or by manual operation of a handle, and brought into pressure contact. The thermoplastic resin used in the present invention is one that does not undergo thermal deterioration during the molding method, has an appropriate viscosity, has good moldability, and can be colored to resemble the color of the gums. The resin is required to have appropriate rigidity, moisture resistance, and toughness that does not cause stress cracks during use. Therefore, polystyrene, polymethyl methacrylate, polymethyllupentene-1, transparent nylon,
Polycarbonate, polyarylate, polyester carbonate, polyethylene terephthalate,
Transparent ABS, polysulfone resins, and the like are used, and polysulfone resins such as polysulfone and polyethersulfone are particularly preferred because they have excellent moisture resistance, rigidity, and stress cracking resistance. The polysulfone resin used as a preferred embodiment in the present invention is defined as a polyarylene polyether polysulfone in which arylene units are located in a disordered or ordered manner with ether and sulfone bonds. for example UCC polysulfone Udel with a structure

One example is polyether sulfone Victrex manufactured by ICI, which has the structure of [Formula]. Effect The heating and softening of the thermoplastic resin in the present invention can be carried out by placing one bed's worth of thermoplastic resin in a simple container such as a cylinder or box, and using a commonly used electric furnace or dryer. Since this method is possible, there is no need for special heating devices such as cylinders, screws, etc. that are used in injection molding methods, and the purpose can be fully achieved with extremely simple equipment. In addition, since the resin is injected into the flask by crushing the container containing the softened thermoplastic resin with the lower flask, it is only necessary to select a container that is strong enough not to destroy the flask. flask, no special container required,
No expensive equipment is required. Furthermore, the container is crushed and the softened thermoplastic resin is injected into the flask through the injection port of the lower flask, but since there is a slight gap between the upper and lower flasks, thin-walled parts such as the neck part etc. However, the flow of resin does not stop and the denture base-shaped cavity is filled to a point close to the end. After one bed's worth of resin has been injected, the upper and lower flasks are pressurized and brought into close contact, allowing the resin located in thin-walled areas such as the oral cavity to spread out, reaching a predetermined thickness and forming the alveolar ridge. Even thick parts such as the vicinity of artificial teeth and areas where resin filling tends to be insufficient are filled with resin in just the right amount, and insufficient pressure that causes sink marks etc. does not occur. That is, a container containing one bed's worth of heat-softened thermoplastic resin is crushed in a lower flask,
By injecting softened resin into the upper and lower flasks and press-fitting the upper and lower flasks, which have a slight gap in advance, after injecting the resin, we are able to eliminate the strictness required by conventional injection molding methods. This eliminates the need for temperature control, pressure control, injection speed control, etc., eliminates the associated increase in size and cost of equipment, and provides a simple and inexpensive method that is extremely easy to handle. Hereinafter, the present invention will be specifically explained with reference to Examples, but these are illustrative of preferred embodiments and are not limited to the scope of the Examples. Example A flask in which a denture base wax model was embedded was heated to soften and flow the wax, thereby forming a predetermined denture base-shaped cavity 2 containing an artificial tooth 1 inside the flask as shown in FIG. Ta. upper flask 3
A plate spring 5 is placed between the upper and lower flasks 4, so that a gap 6 of 2 mm is provided between the upper and lower flasks.
Upper and lower flasks were placed. On the other hand, a cylindrical container 7 made of aluminum with a wall thickness of 0.1 mm, a diameter of 30 mm, and a depth of 40 mm was filled with a thermoplastic resin polyethersulfone (manufactured by ICI) colored to resemble gums.
After accommodating one bed of 3mm thick plate-shaped molded products of Victrex 4100G), they were placed in a hot air circulation dryer at 360℃ for 10 minutes.
Heat for a minute to soften. Aluminum container 7 containing heat-softened polyether sulfone 8
After placing the container 7 at a position 7 cm below the lower flask, raise the container 7 as shown in FIG. The polyether sulfone 8 softened by pressing strongly and crushing the container 7.
was inserted into the denture base-shaped cavity 2 in the flask through the resin injection port 9. After injecting a predetermined amount of softened polyether sulfone, as shown in FIG. 3, the upper flask 3 was pressurized downward and the leaf springs 5 were spread out to bring the upper flask 3 and the lower flask 4 into close contact. After cooling, the plaster was crushed and the denture base molded product was taken out. The denture base molded product was completely filled with resin in every corner, no sink marks were observed even in the thick wall portion, and the product had a good wall thickness and dimensions that were faithful to the denture base wax model. Effects of the Invention As described above, the present invention involves injecting one bed's worth of softened thermoplastic resin contained in a simple container into the flask by crushing the container with the lower flask. By pressing the upper and lower flasks together, the softened resin is filled into every corner of a predetermined cavity, so the following effects are achieved. (1) Stricter temperature control compared to traditional injection molding methods,
Since injection pressure control and injection speed control are not required, the device is small and can be manufactured at low cost. (2) After injecting the softened resin, the resin is spread and inserted under pressure, so excessive residual strain does not occur at the resin injection part (gate part) during injection molding. (3) Sufficient pressure is applied until the softened resin completely fills the cavity, so thick parts such as the alveolar ridge will not collapse. (4) Since thermoplastic resin is used, there is no residual monomer, which is a problem with conventional acrylic heating polymerization methods.

[Brief explanation of drawings]

1 to 3 are cross-sectional views showing the steps of an embodiment of the method of the present invention. 1... Artificial tooth, 2... Denture base shaped cavity, 3... Upper flask, 4... Lower flask, 5... Leaf spring, 6
...Void, 7...Container, 8...Thermoplastic resin, 9
...Resin injection port.

Claims (1)

[Claims] 1. A mold consisting of an upper and lower flask with a desired denture base-shaped cavity inside is opened up and down to create a slight gap between both flasks, and a bed of heat-softened mold is placed below the injection port at the bottom of the lower flask. The method is characterized in that a container containing a thermoplastic resin is placed, the container is pressed and crushed by the lower flask, and the resin is injected into the flask through the injection port of the lower flask, and then the upper and lower flasks are brought into pressure contact. A denture base manufacturing method.