Manufacturing method of resin material for dental cutting

Abstract

To provide a method for producing a resin material for dental cutting work that is less likely to cause bubbles or cracks even if it contains fibers. [Solution] The process includes the steps of placing a fiber sheet inside a mold formed from a material other than metal and equipped with a means for equalizing the pressure inside and outside, and injecting unhardened resin material into the inside of the mold, or injecting unhardened resin material mixed with fibers into the inside of the mold, placing the mold in a container that can apply a predetermined pressure to the entire mold, pressurizing it to 1.0 MPa or more, and heating it to 60°C or more.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a dental cutting resin material used in producing dental prostheses such as inlays, crowns, and bridges. [Background technology]

[0002] In dental treatment, when aesthetics are required, such as inlays and crowns, filling restorations using dental composite resins or restorations using dental prostheses such as ceramic inlays, resin-faced cast crowns, porcelain-fused-to-metal-faced cast crowns, and all-ceramic crowns are generally performed.

[0003] However, in the case of filling restorations using dental composite resin, the paste-like dental composite resin is polymerized and hardened inside the tooth cavity, so it is inevitable that unpolymerized monomers will remain, resulting in the problem of pulp irritation.In addition, in the case of dental prostheses that can be made by sufficiently polymerizing the monomer outside the oral cavity, the shape of the oral cavity and the target area for the prosthesis differ from patient to patient, and the manufactured dental prostheses require extremely high dimensional accuracy of several microns, which requires not only the skill of a technician but also a great deal of time and money.

[0004] For this reason, in recent years, CAD / CAM systems have become increasingly popular for manufacturing dental prostheses, which use computers to design dental prostheses such as inlays, crowns, and bridges on a screen and then manufacture the dental prostheses through cutting. This allows for a stable supply of dental prostheses of consistent quality in a short amount of time. In cutting processes using CAD / CAM equipment, dental resin materials for cutting are used, which are dental resins formed into blocks or discs, as the material before being cut into shapes. As described in Patent Document 1, for example, this dental resin material for cutting is a block of an acrylic resin polymer containing 20% ​​to 70% by mass of inorganic filler with an average particle size of 0.001 μm to 0.04 μm.

[0005] Furthermore, in order to improve the strength of such dental cutting resin materials, there are materials in which fibers are mixed into the resin, and materials in which fiber sheets are laminated and filled with resin (for example, Patent Documents 2 to 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-323353 [Patent Document 2] Patent No. 5944602 [Patent Document 3] International Publication WO2020 / 166667 [Patent Document 4] Patent No. 6204801 Summary of the Invention [Problem to be solved by the invention]

[0007] However, resin materials for dental cutting that contain such fibers may have air bubbles during production, and these air bubbles may remain after the resin hardens, resulting in a decrease in mechanical strength.

[0008] Therefore, an object of the present disclosure is to provide a method for manufacturing a resin material for dental cutting that is less likely to leave air bubbles even when it contains fibers and that can suppress a decrease in mechanical strength. [Means for solving the problem]

[0009] The present application discloses a method for producing a resin material for dental cutting processing before cutting out a shape, the method including the steps of: placing a fiber sheet inside a mold formed from a material other than metal and equipped with a means for equalizing the internal and external pressures; injecting unhardened resin material into the mold; placing the mold with the fiber sheet and unhardened resin material placed in a container that can apply a predetermined overall pressure; and pressurizing the mold, unhardened resin material, and fiber sheet at 1.0 MPa or more; and heating the mold, unhardened resin material, and fiber sheet at 60°C or more.

[0010] The fibrous sheet may be pre-impregnated with a resin material.

[0011] The present application also discloses a method for producing a resin material for dental cutting before cutting out a shape, which includes the steps of injecting unhardened resin material mixed with fibers into the inside of a mold formed from a material other than metal and equipped with a means for equalizing the internal and external pressures, placing the mold with the fibers and unhardened resin material placed in a container that can apply a predetermined overall pressure, and pressurizing the mold, unhardened resin material, and fibers at 1.0 MPa or more, and heating the mold, unhardened resin material, and fibers at 60°C or more.

[0012] The mold may be made of any of thermoplastic resin, silicone resin, and polypropylene. [Effects of the Invention]

[0013] According to the manufacturing method of the resin material for dental cutting processing disclosed herein, it is possible to provide a resin material for dental cutting processing that reduces the amount of residual air bubbles even when it contains fibers, thereby suppressing a decrease in mechanical strength. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of the exterior of a mold according to one example. DETAILED DESCRIPTION OF THE INVENTION

[0015] The above-described functions and advantages of the present disclosure will become apparent from the following embodiments, although the present disclosure is not limited to these embodiments.

[0016] 1. Dental polymerizable composition First, the dental polymerizable composition used in this embodiment will be described.

[0017] [Curable resin] The curable resin (polymerizable monomer) used may be a methacrylate compound or an acrylate compound that has been widely used in conventional dental materials. Examples of the methacrylate compound or acrylate compound include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxy-1,3-dimethacryloxypropane, n-butyl methacrylate, isobutyl methacrylate, tetrahydrofurfuryl methacrylate, glycidyl methacrylate, 2-methoxyethyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, phenyl methacrylate, phenoxyethyl methacrylate, 2,2-bis(methacryloxyphenyl)propane, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane, 2,2-bis(4-methacryloxydiethoxyphenyl)propane, 2,2-bis(4-methacryloxypolyethoxyphenyl)propane, ethylene glycol Examples of (meth)acrylates include 1,3-butanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, pentaerythritol trimethacrylate, trimethylolmethane trimethacrylate, pentaerythritol tetramethacrylate, di-2-methacryloxyethyl-2,2,4-trimethylhexamethylene dicarbamate, 1,3,5-tris[1,3-bis(methacryloyloxy)-2-propoxycarbonylaminohexane]-1,3,5-(1H,3H,5H)triazine-2,4,6-trione, and acrylates thereof. These (meth)acrylates can be used alone or in combination as needed. Here, (meth)acrylate refers to a compound having a methacryloyloxy group and / or an acryloyloxy group (hereinafter referred to as a (meth)acryloyloxy group).

[0018] In addition to or instead of the above, a curable resin having only one group selected from the group consisting of a urethane group, a urea group, and a carbonate group (hereinafter referred to as a urethane group, etc.) may be contained. The urethane group is a linking group represented by -NHCOO-. The urea group is a linking group represented by -NHCONH-. The carbonate group is a linking group represented by -OCOO-.

[0019] A curable resin having only one urethane group or the like contains one urethane group or the like, but does not contain two or more urethane groups or the like. The curable resin having only one urethane group or the like is not particularly limited, and is, for example, a (meth)acrylate containing only one urethane group or the like.

[0020] The (meth)acrylate containing only one urethane group or the like is preferably a (meth)acrylate having two or more (meth)acryloyloxy groups.

[0021] A (meth)acrylate containing only one urethane group or the like is represented by, for example, the following formula (1).

[0022] [ka]

[0023] In formula (1), A1 and A2 are each independently a (meth)acryloyloxy group or a (meth)acrylamide group which may have an alkyl group having 3 or less carbon atoms on the side chain, B is a urethane group, and R1 and R2 are each independently an alkyl group having 8 or less carbon atoms which may have a (meth)acryloyloxy group or a (meth)acrylamide group on the side chain.

[0024] Here, the (meth)acrylamide group refers to a methacrylamide group and / or an acrylamide group, where the acrylamide group is a substituent represented by -NHCO(CH=CH2).

[0025] It is preferable that A1 and A2 have an alkyl group with 2 or less carbon atoms in the side chain of the (meth)acryloyloxy group or (meth)acrylamide group, or that the (meth)acryloyloxy group or (meth)acrylamide group does not have an alkyl group in the side chain. It is also preferable that R1 and R2 have an alkyl group with 5 or less carbon atoms.

[0026] In addition, when the number of carbon atoms in the alkyl group of R1 and R2 is 9 or more, the curable resin having only one urethane group or the like is likely to be distorted, and the cured product obtained by curing the dental polymerizable composition containing such a curable resin does not have sufficient mechanical strength.

[0027] The (meth)acrylate represented by the above formula (1) is not particularly limited, but is, for example, a (meth)acrylate containing only one urethane group represented by the following formulas (2) to (6): The (meth)acrylate represented by formula (3) is sometimes referred to as mUDMA.

[0028] [ka]

[0029] [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] Furthermore, by using a curable resin having only one urethane group or the like, it is possible to obtain a cured product with high strength while keeping the viscosity low. That is, since the viscosity can be kept low without reducing the strength of the cured product, it is possible to obtain a cured product that is less likely to trap air bubbles (the generation and retention of air bubbles can be reduced) while maintaining strength.

[0034] The content of the above-mentioned curable resin in the dental polymerizable composition is not particularly limited, but is preferably 5% by mass to 30% by mass, more preferably 10% by mass to 28% by mass, and even more preferably 12% by mass to 25% by mass. When the content of the curable resin having only one urethane group or the like is 10% by mass to 27% by mass, the cured product of the dental polymerizable composition can maintain high mechanical strength.

[0035] The content of the curable resin varies depending on the use of the dental polymerizable composition, but when the dental polymerizable composition is used as a resin material for dental cutting, it is preferably 5% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 25% by mass or less.

[0036] [Polymerization initiator] Since the resin is used as a dental cutting resin material, a polymerization initiator may be used. In the present disclosure, molding is performed by pressurizing and heating, so a thermal polymerization initiator is preferred. Examples of thermal polymerization initiators include organic peroxides and azo compounds. Specific examples include benzoyl peroxide, ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxyester, peroxydicarbonate, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 4,4'-azobis-4-cyanovaleric acid, 1,1'-azobis-1-cyclohexanecarbonitrile, dimethyl-2,2'-azobisisobutyrate, and 2,2'-azobis-(2-aminopropane) dihydrochloride. These may be used alone or in combination.

[0037] [Filler] A filler may be blended into the dental polymerizable composition. The filler is preferably an inorganic filler having an average particle size of 0.01 μm to 100 μm, more preferably 0.05 μm to 70 μm, and even more preferably 0.1 μm to 50 μm. Here, the average particle size refers to the average particle size defined by the median diameter (d50).

[0038] Colloidal silica is a common inorganic filler, and examples of such fillers include Aerosil OX-50 (average particle size 0.04 μm) and Aerosil R-972 (average particle size 0.016 μm) manufactured by Nippon Aerosil Co., Ltd. Crushed glass powder is a common inorganic filler, and although its composition is not particularly limited, suitable fillers include quartz glass, aluminosilicate glass, X-ray contrast glass containing alkaline earth metal atoms such as calcium, strontium, and barium, zinc glass, and lead glass. The glass powder is preferably surface-silanized before use, and is typically silanized using a conventional method using an organosilicon compound such as 3-methacryloxypropyltrimethoxysilane or 8-methacryloxyoctyltrimethoxysilane as a surface treatment agent.

[0039] If the content of the inorganic filler is less than 0.1% by mass, it is difficult to obtain a sufficient thickening effect, while if it exceeds 2% by mass, the resin paste hardens when the dental polymerizable composition is prepared, and air bubbles tend to be mixed into the resin polymer, which is not appropriate.If the content of the inorganic filler is less than 1% by mass, it is difficult to obtain sufficient abrasion resistance, while if it exceeds 80% by mass, it is not appropriate, because the resin paste hardens when the dental polymerizable composition is prepared, and air bubbles tend to be mixed into the resin polymer.

[0040] Depending on the required performance, an organic-inorganic composite filler can be added, which is prepared by mixing the inorganic filler with a methacrylate or acrylate monomer having at least one unsaturated double bond, curing the mixture, and pulverizing the mixture to an average particle size of 5 μm to 50 μm. In this case, the content of the organic-inorganic composite filler is preferably 1% by mass to 40% by mass. If the content is less than 1% by mass, the effect of improving surface smoothness and abrasion resistance is not observed, and if it exceeds 40% by mass, the mechanical strength decreases.

[0041] In addition, trace amounts of ultraviolet absorbers, colorants, polymerization inhibitors, polymerization accelerators, chain transfer agents, fluorescent agents, antibacterial agents, etc. may be used as needed.

[0042] [fiber] The dental polymerizable composition of this embodiment contains fibers. This is an embodiment in which fibers are contained in the mixed composition of the above-mentioned materials, but fine fibers may be dispersed so as to be mixed in the mixed composition, or fibers woven into a sheet may be contained so as to be arranged. Examples of fibers include inorganic fibers.

[0043] The inorganic fibers are not particularly limited as long as they are inorganic materials, but examples include glass fibers, ceramic fibers, alumina fibers, zirconia fibers, etc. These fibers may be used alone or in combination of two or more. Among these inorganic fibers, glass fibers are preferred from the viewpoint of mechanical strength. Glass fibers include long fibers (glass fiber) and short fibers (glass wool), with long fibers being preferred. There are several types of glass fibers, and they are not particularly limited, but A glass fiber, C glass fiber, E glass fiber, S glass fiber, T glass fiber, ECR glass fiber, AR glass fiber, NCR glass fiber, etc. can be used.

[0044] The average fiber diameter of the inorganic fibers is not particularly limited, but is preferably 2.0 μm or more and 20 μm or less. The lower limit is more preferably 4.0 μm or more, and more preferably 6.0 μm. On the other hand, the upper limit is more preferably 18 μm, and more preferably 15 μm. If the average fiber diameter is smaller than 2.0 μm, the strength of the dental cutting resin material tends to be insufficient. If the average fiber diameter exceeds 20 μm, the strength may be too high, resulting in reduced cutting ability. The average fiber diameter can be determined, for example, by observation. Specifically, a cross section perpendicular to the direction of extension of the inorganic fibers is photographed using a scanning electron microscope (SEM), and the fiber diameters of the inorganic fibers observed within the field of view of the SEM photograph are measured by image analysis and averaged over 100 fibers. Since the cross section of the fiber is not exactly circular, the fiber diameter is determined by the diameter of a circle that corresponds to the cross-sectional area of ​​the fiber.

[0045] The fiber length of the inorganic fibers is not particularly limited, but can be, for example, 50 μm or more and 150 mm or less. The lower limit is more preferably 80 μm or more, and even more preferably 100 μm. Meanwhile, the upper limit is more preferably 120 mm, and even more preferably 100 mm.

[0046] The inorganic fibers may be surface-treated, thereby increasing the mechanical strength of the dental cutting resin material. Known surface treatments can be used. Examples of surface treatments include organometallic compounds such as organosilicon compounds, organotitanium compounds, organozirconium compounds, and organoaluminum compounds, as well as acidic group-containing organic compounds having at least one acidic group, such as a phosphate group, a pyrophosphate group, a thiophosphate group, a phosphonate group, a sulfonate group, or a carboxylic acid group. Among these, silanization using organosilicon compounds such as 3-methacryloxypropyltrimethoxysilane and 8-methacryloxyoctyltrimethoxysilane is preferred.

[0047] When a woven fiber sheet is used, it can have a structure in which a plurality of inorganic fiber bundles aligned in one direction intersect with a plurality of inorganic fiber bundles aligned in a different direction, thereby reducing the directional strength difference in the dental cutting resin material. That is, a mesh-like structure can be produced by weaving warp threads (vertical threads) and weft threads (horizontal threads) of inorganic fiber bundles. The weaving method is not particularly limited, but examples include "plain weave," "twill weave," and "satin weave." Among these, twill weave is preferred. In twill weave, when the warp threads cross the weft threads two above and two below, it is called a "2 / 2 twill weave," when they cross two above and one below, it is called a 2 / 1 twill weave, and when they cross three above and one below, it is called a "3 / 1 twill weave." Among these, 2 / 2 twill weave, in which the warp threads cross at intervals of two in both the warp and weft directions, is preferred because it has a good balance of strength.

[0048] The inorganic fiber bundles constituting the warp and weft of the fiber sheet are made by bundling inorganic fiber threads together, and the width of the inorganic fiber bundles for the fiber sheet is preferably 0.2 mm to 1.5 mm.

[0049] Such a fiber sheet may be impregnated in advance with the composition containing the curable resin described above. The impregnation method is not particularly limited, and examples thereof include immersing the fiber sheet in the composition.

[0050] The mass ratio of the "fibers" to the volume of the dental cutting resin material is not particularly limited, but is preferably 65% ​​to 82% by mass.

[0051] 2. Manufacturing method of resin material for dental cutting Next, a method for producing a resin material for dental cutting using the dental polymerizable composition will be described.

[0052] The dental resin material for cutting is manufactured by injecting the dental polymerizable composition described above into a mold having a desired shape (for example, FIG. 1 shows a rectangular box-shaped mold 1 with a bottom 1a on one side. However, the shape of the mold is not particularly limited, and it may be a cylindrical box, a tapered rectangular box, etc.), pressurizing it in the range of 1.0 MPa to 8 MPa, and once the pressure increase is complete, heating it in the range of 60°C to 200°C to polymerize and harden it, and molding it into a block or disk shape.

[0053] Here, the material constituting the mold is a material other than metal. Among them, synthetic resin is preferable from the viewpoint of dimensional accuracy and moldability of the mold. Thermoplastic resin and silicone resin are more preferable. This can significantly reduce the occurrence of cracks in the dental cutting resin material produced. The thermoplastic resin used can be a resin that has been widely used in general industry, and among them, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polytetrafluoroethylene, acrylonitrile butadiene styrene resin, acrylic resin, etc. can be used.

[0054] The placement of the dental polymerizable composition in the mold is not particularly limited, but the dental polymerizable composition may be one in which fibers have been mixed into the composition, or a fiber sheet may be placed in the mold in advance and then other materials may be injected into the mold.

[0055] The process of pressurizing the mold and the unhardened dental polymerizable composition poured into the mold at 1.0 MPa or more, and the process of heating the mold and the unhardened dental polymerizable composition poured into the mold at 60°C or more and 200°C or less are processes in which the composition is placed in a non-metallic mold, placed in a container that can apply a predetermined pressure to the entire mold, and pressurized and heated to polymerize the composition so that the pressure inside and outside the mold is equal. The container can be a pressurized heating container such as an autoclave or pressure cooker used in industry. Means for equalizing the pressure inside and outside the mold in this step include providing an open opening in the mold, or, for example, in a concave-convex mold, pouring the composition into the concave portion of the concave mold, placing the convex mold on top of it in a floating state, and then pressurizing and heating the composition in the container. Alternatively, the composition can be poured into a rectangular container with an open top, and then pressurizing and heating the composition through the open top opening with a thin resin film such as plastic wrap placed on top of the composition.

[0056] Regarding pressure, if the pressure is less than 1.0 MPa, the inclusion of air bubbles cannot be sufficiently suppressed, increasing the possibility of the formation of air bubbles that can cause chipping. On the other hand, even if the pressure exceeds 8 MPa, the performance of the dental cutting resin material itself is not affected, but further improvement in effectiveness by increasing the pressure is not observed and it becomes difficult to maintain high pressure.

[0057] Regarding the heating temperature, a heating temperature of less than 60°C is not appropriate because unpolymerized monomers may remain. However, from the viewpoint of avoiding a long polymerization time and improving productivity, a heating temperature of 80°C or higher is preferable. On the other hand, a heating temperature of more than 200°C is not appropriate because it restricts the material of the packing used in the pressurizing and heating container.

[0058] By producing a dental cutting resin material under the above conditions, a dental cutting resin material with good moldability and few cracks or bubbles can be obtained. Although the shape of the dental cutting resin material is usually a rectangular parallelepiped or cylindrical, it is preferable to pre-shape it into a shape similar to the shape of an inlay, crown, or bridge, since this reduces the amount of cutting required during cutting.

[0059] The dental resin material for dental cutting thus obtained is used to prepare a dental prosthesis, for example, as follows. First, impressions of the patient's oral cavity, including the abutment tooth side and the opposing tooth side, are taken using dental impression material. The upper and lower jaw impressions can be taken simultaneously or separately. Next, a plaster model is made based on the impression taken. The plaster model is then measured using a contact or non-contact measuring device to obtain three-dimensional coordinate data of the shape of the oral cavity, which is then stored as a digital signal in the memory of a computer. The three-dimensional coordinate data stored in memory is then used to graphically display the shape of the patient's abutment teeth on the computer's CRT screen using wire frames, etc. The positional relationship with the opposing teeth is determined by setting certain reference points on the plaster models of the upper and lower jaws in advance, and then using the shape measurement data of the plaster models of the upper and lower jaws, the reference points are aligned and the result is reproduced graphically on the CRT.

[0060] The shapes of the inlay, crown, or bridge are drawn and designed based on the abutment tooth and opposing tooth shapes graphically displayed on the CRT. This process can be further facilitated by using pre-registered standard data for the inlay, crown, or bridge. If necessary, a cement space can be created by offsetting the inner surface of the inlay, crown, or bridge by any desired dimension. Once the design of the inlay, crown, or bridge is complete and the three-dimensional coordinate data is obtained, processing commands are transmitted from the computer to an NC-controlled processing machine. The processing machine then processes the dental cutting resin material described above to produce the inlay, crown, or bridge according to the instructions. If necessary, characterization, such as staining, can be performed using dental hard resin or crown coloring material to match the color tone of the patient's remaining teeth.

[0061] The resin material for dental cutting produced according to the present disclosure has few cracks and bubbles, making it less likely to cause defects such as chipping during production, and enabling the production of high-quality dental prostheses. [Example]

[0062] In the following examples, resin materials for dental cutting were prepared according to the examples and comparative examples to be compared with them, and their quality was verified.

[0063] [Monomer liquid] Four types of monomer liquids were prepared. Using a magnetic stirrer, various materials were mixed in the blending ratios shown in Table 1 to obtain monomer liquids of Blends 1 to 4.

[0064] [Table 1]

[0065] The abbreviations used in Table 1 represent the following chemical substances: mUDMA: Formula (3) above Bis-MEPP: 2,2-bis(4-methacryloxypolyethoxyphenyl)propane UDMA: Di-2-methacryloxyethyl-2,2,4-trimethylhexamethylene dicarbamate Bis-GMA: 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane TEGDMA: Triethylene glycol dimethacrylate BPO: Benzoyl peroxide

[0066] [Composition] Table 2 shows the types and compositions of materials for Examples 1 to 10 and Comparative Examples 1 to 4. In Table 2, "fiber sheet" refers to fibers formed into a sheet, "short fiber" refers to fibers with a fiber length of 100 μm, and "long fiber" refers to fibers with a fiber length of 30 mm. All fibers were E-glass fibers that had been treated in advance with 3-methacryloxypropyltrimethoxysilane. Also in Table 2, the filler is colloidal silica + silane-treated glass.

[0067] [Table 2]

[0068] [Preparation and evaluation of resin materials for dental cutting] In Examples 1 to 5, the E-glass fibers woven into a sheet were laid out in a mold (a container-like mold with one side open, the same applies below) measuring 15 mm in length, 19 mm in width, 39 mm in depth, and 1 mm in thickness, and the monomer liquid was filled around the mold to impregnate it. The materials of the mold are shown in Table 3. In Examples 6 and 7, E-glass short fibers and a filler were mixed in a double planetary mixer to prepare a paste, which was then filled into a mold measuring 15 mm in length, 19 mm in width, 39 mm in depth, and 1 mm in thickness. In Example 8, a sheet of woven E-glass fibers was pre-soaked in a monomer solution and placed near the center of a mold measuring 15 mm in length, 19 mm in width, 39 mm in depth, and 1 mm in thickness. A paste containing E-glass short fibers and a filler (prepared in the same manner as in Examples 6 and 7) was packed around the sheet. In Example 9, E-glass long fibers were laid in a mold measuring 15 mm in length, 19 mm in width, 39 mm in depth and 1 mm in thickness, and the monomer liquid was filled around the fibers to impregnate them. In Example 10, E-glass long fibers were pre-impregnated with a monomer liquid and placed near the center of a mold measuring 15 mm in length, 19 mm in width, 39 mm in depth, and 1 mm in thickness. A paste containing E-glass short fibers and a filler (prepared in the same manner as in Examples 6 and 7) was packed around the fibers.

[0069] In Comparative Examples 1 and 2, the material was filled into the mold in the same manner as in Examples 1 to 5. In Comparative Example 3, the material was filled into the mold in the same manner as in Example 8. In Comparative Example 4, the material was filled into the mold in the same manner as in Example 9.

[0070] In each example, the hardenable composition filled into the mold was polymerized and hardened for 80 to 180 minutes at 100 to 130°C under nitrogen pressure of 1.0 to 5.0 MPa to obtain a rectangular solid-shaped hardened body (resin material for dental cutting).

[0071] The hardened material (dental cutting resin) obtained in each example was evaluated by the following tests. <Moldability> The hardened body removed from the mold was visually inspected to ensure that it had no voids, had spread to the shape of the inner surface of the mold, and had the correct shape.

[0072] <Cracks and bubbles> The hardened body was removed from the mold and cut into 15 pieces with a thickness of 1.5 mm using a diamond cutter, and the presence or absence of cracks and bubbles inside the hardened body was checked using a microscope (Keyence Corporation, VHX-8000).

[0073] The mold materials and evaluation results are shown in Table 3. In Table 3, "PP" stands for polypropylene, and "SUS" stands for stainless steel SUS303.

[0074] [Table 3]

[0075] As can be seen from Table 3, when metal molds are used as in the comparative example, at least one of voids, cracks, and bubbles occurs in the hardened body after molding, while such defects do not occur when non-metallic molds are used. [Explanation of symbols]

[0076] Type 1

Claims

1. A method for producing a resin material for dental machining before cutting out a shape, comprising: placing a fiber sheet inside a mold formed of a material other than metal and having a means for equalizing internal and external pressure; Injecting an uncured resin material into the mold; a step of placing the mold in which the fiber sheet and the uncured resin material are placed into a container capable of applying a predetermined pressure to the mold, the uncured resin material, and the fiber sheet at a pressure of 1.0 MPa or more; and heating the mold, the uncured resin material, and the fiber sheet to 60°C or higher. A manufacturing method for resin materials for dental cutting.

2. The method for manufacturing a resin material for dental cutting according to claim 1, wherein the fiber sheet is pre-impregnated with the resin material.

3. A method for producing a resin material for dental machining before cutting out a shape, comprising: A step of injecting a resin material before hardening mixed with fibers into the inside of a mold formed of a material other than metal and having a means for equalizing the pressure inside and outside; a step of placing the mold in which the fibers and the uncured resin material are placed into a container capable of applying a predetermined pressure to the mold, the uncured resin material, and the fibers at a pressure of 1.0 MPa or more; and heating the mold, the uncured resin material, and the fibers to 60°C or higher. A manufacturing method for resin materials for dental cutting.

4. 4. The method for manufacturing a resin material for dental cutting according to claim 1, wherein the mold is formed from any one of thermoplastic resin, silicone resin, and polypropylene.

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