Dental Composition

Abstract

To provide a dental composition that has excellent flowability and is polymerized and cured into a product having excellent impact resistance.SOLUTION: A dental composition contains a powder component and a liquid component. Relative to 100 pts.wt. of the powder component, the amount of the liquid component is 60-80 pts.wt. The powder component contains a particle (A) comprising a methyl methacrylate polymerized in the presence of a conjugated diene compound, and a particle (B) of polymethyl methacrylate. The weight ratio of the particles (A) and the particles (B) is 55: 45-99: 1.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dental composition. [Background technology]

[0002] Known dental compositions used for denture base materials, dental restorative materials, etc. include those containing a powder component primarily composed of polymer particles and a liquid component primarily composed of a polymerizable monomer. These powder and liquid components are configured to polymerize and harden upon mixing. Patent Document 1, for example, describes such a dental composition, which contains a (meth)acrylate as a resin matrix monomer and particles of polymethyl(meth)acrylate containing a conjugated diene compound. Patent Document 1 also describes that the use of this dental composition makes it possible to easily obtain denture bases and other products with excellent impact resistance at low cost. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-75862 Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the intended use or method of use, the dental composition described in Patent Document 1 may require improvement in terms of fluidity. For example, when preparing a denture base, a powder component and a liquid component are mixed, poured into a predetermined mold, and then hardened and molded. Insufficient fluidity can result in a long pouring process or an inability to obtain the desired shape corresponding to the mold. Additives can be used to enhance fluidity, but such additives may reduce the impact resistance of the resulting polymerized and cured product.

[0005] Therefore, an object of one aspect of the present invention is to provide a dental composition that has excellent fluidity and from which the resulting polymerized and cured product also exhibits excellent impact resistance. [Means for solving the problem]

[0006] One aspect of the present invention is a dental composition comprising a powder component and a liquid component, wherein the amount of the liquid component is 60 to 80 parts by weight per 100 parts by weight of the powder component, the powder component comprises particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound, and particles (B) of polymethyl (meth)acrylate, and the weight ratio of the amount of the particles (A) to the amount of the particles (B) is 55:45 to 99:1. [Effects of the Invention]

[0007] According to one aspect of the present invention, a dental composition can be provided that has excellent fluidity and the resulting polymerized and cured product also exhibits excellent impact resistance. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Dental composition> A dental composition according to one embodiment of the present invention is a powder-liquid composition comprising a powder component primarily composed of polymer particles and a liquid component primarily composed of a polymerizable monomer. When in use, the two components are mixed and polymerized and hardened to obtain a polymerized and hardened product. For example, a mixture obtained by mixing the powder component and the liquid component can be molded into a desired shape, or applied or filled to a desired object, and hardened to obtain a hardened product. The dental composition can be used as a material for denture bases or artificial teeth, or as a dental restorative material, and is particularly suitable as a material for denture bases.

[0009] The powder component in this embodiment contains at least two types of (meth)acrylate particles in a predetermined ratio. More specifically, the powder component contains particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound and particles (B) of polymethyl (meth)acrylate. The use of these two different types of particles results in excellent fluidity of the dental composition and excellent impact resistance of the cured dental composition. Furthermore, the dental composition after hardening also has excellent bending strength. Therefore, when a denture base is produced by pouring the composition into a predetermined mold, operability is improved and a desired shape with little or no defects corresponding to the mold can be reliably obtained. In this specification, "(meth)acrylate" refers to acrylate and / or methacrylate.

[0010] <Particles (A) Obtained by Polymerizing Methyl (Meth)acrylate in the Presence of a Conjugated Diene Compound> The powder component in this embodiment includes particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound. Particles (A) can be produced, for example, by dissolving a conjugated diene monomer or oligomer, or a conjugated diene rubbery (co)polymer in methyl (meth)acrylate to obtain a mixture, and then polymerizing the mixture. In this case, suspension polymerization is preferred as the polymerization method, since it produces particles with higher sphericity and a narrower particle size distribution. This method, in this embodiment, produces particles in which the conjugated diene compound is more uniformly dispersed within the polymethyl (meth)acrylate particles. More specifically, particles (A) are preferably a mixture of polymethyl (meth)acrylate and a conjugated diene compound, which produces particles in which the conjugated diene compound is microscopically uniformly dispersed within the polymethyl (meth)acrylate.

[0011] The conjugated diene compound may be a liquid conjugated diene monomer or oligomer, or a conjugated diene rubbery (co)polymer. Examples of liquid conjugated diene monomers or oligomers include polybutadiene diacrylate and polybutadiene dimethacrylate. Here, "liquid" means that the compound is liquid at room temperature.

[0012] Conjugated diene rubber (co)polymers include styrene-butadiene rubber (SBR) and ethylene-propylene Jien Examples of suitable rubber include rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, etc. Among these, styrene-butadiene rubber is preferred because it is easily available and relatively inexpensive.

[0013] When the conjugated diene compound is a conjugated diene rubbery (co)polymer, its weight-average molecular weight is preferably 100,000 to 300,000, and more preferably 150,000 to 250,000. When the conjugated diene rubbery (co)polymer has a weight-average molecular weight of 100,000 or more, impact resistance can be improved, and when it is 300,000 or less, good fluidity as a dental composition can be obtained.

[0014] In this way, particles of polymethyl(meth)acrylate containing a conjugated diene compound are formed as particles (A), more specifically, polymer particles in which the conjugated diene compound is uniformly dispersed.Therefore, by including particles (A) in the powder component, the impact resistance of the cured product obtained by polymerizing and curing the dental composition of this form can be increased compared to when particles of the conjugated diene compound are directly blended into the powder component.

[0015] The particles produced by polymerization can be treated by one or more of the steps of separation, washing, drying and classification.

[0016] To obtain particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound, it is preferable to use a polymerization initiator during polymerization. When polymerization is performed by suspension polymerization, it is preferable to use a thermal polymerization initiator. Thermal polymerization initiators include organic peroxides and azo compounds. Preferred organic peroxides include aromatic diacyl peroxides and peroxyesters that can be considered as esters of perbenzoic acid, such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-tolyl peroxide, t-butyl peroxybenzoate, di-t-butylperoxyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di{(o-benzoyl)benzoylperoxy}hexane. Examples of azo compounds that can be used include azobisisobutyronitrile and other organometallic compounds such as tributylboron.

[0017] The methyl (meth)acrylate monomer used to prepare the particles (A) may be methyl methacrylate, methyl acrylate, or a combination thereof, among which methyl methacrylate is preferably used.

[0018] In the particles (A), the weight ratio of the conjugated diene compound to the polymethyl(meth)acrylate, i.e., (weight of the conjugated diene compound):(weight of the polymethyl(meth)acrylate), is preferably 5:95 to 15:85, and more preferably 5:95 to 10:90. When the amount of the conjugated diene compound is within the above range, the dental composition has good fluidity and the impact resistance of the cured product obtained by polymerizing and curing the dental composition is improved. In particular, when the weight ratio of the polymethyl(meth)acrylate to the conjugated diene compound is 90:10 or less, i.e., a weight ratio of 90:10 or an amount of the conjugated diene compound less than 90:10, the bending strength of the polymerized and cured product can be improved.

[0019] The average particle size of the particles (A) may be preferably 60 to 120 μm, more preferably 80 to 100 μm. By setting the average particle size within the above range, more preferable flowability, impact resistance, and bending strength can be obtained. In this specification, the average particle size is a volume-based average particle size measured by laser diffraction.

[0020] <Polymethyl (meth)acrylate particles (B)> The powder component in this embodiment further contains particles (B) of polymethyl (meth)acrylate in addition to the particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound.

[0021] The polymethyl (meth)acrylate particles (B) may be polymethyl acrylate, polymethyl methacrylate, a methyl acrylate-methyl methacrylate copolymer, or a mixture of polymethyl acrylate and polymethyl methacrylate. In consideration of flowability, the polymethyl (meth)acrylate particles (B) are preferably polymethyl methacrylate (PMMA).

[0022] In the particles (B), the weight average molecular weight of the polymethyl (meth)acrylate may be 800,000 to 1,000,000.

[0023] The powder component containing polymethyl (meth)acrylate particles (B) can improve the flowability of the dental composition, thereby improving its operability. For example, when the dental composition is used to mold a denture base or the like, the dental composition can be easily poured into a mold, and a molded product without defects can be obtained.

[0024] The average particle size of the polymethyl (meth)acrylate particles (B) may be preferably 60 to 120 μm, more preferably 80 to 100 μm. By setting the average particle size within the above range, more preferable operability and physical properties can be obtained. By setting the average particle size to 60 μm or more, the flowability when mixed with a liquid is improved, making handling easier. By setting the average particle size to 120 μm or less, the dental composition can be prevented from hardening before it has fully swelled, and good impact resistance and bending strength can be obtained.

[0025] The polymethyl (meth)acrylate particles (B) may contain other monomer units other than methyl (meth)acrylate and / or other polymers other than polymethyl (meth)acrylate to the extent that the function of the particles (B) is not impaired. However, it is preferable that the particles (B) are substantially free of such other monomer units and other polymers. In particular, the particles (B) may be a polymer that is substantially free of monomer units of conjugated diene compounds and polymers or oligomers of conjugated diene compounds. Here, "substantially free of" a specified component means that the specified component is not actively added, and does not exclude the inevitable inclusion of the specified component during the raw material preparation stage or manufacturing process. Similarly, "substantially consisting of" a specified component means that no components other than the specified component are actively added, and does not exclude the inevitable inclusion of components other than the specified component during the raw material preparation stage or manufacturing process. More specifically, when the polymethyl(meth)acrylate in the particles (B) of polymethyl(meth)acrylate contains another monomer unit other than methyl(meth)acrylate (other than methyl methacrylate and / or methyl acrylate), the amount of the other monomer unit may be 1% by weight or less based on the total amount of polymethyl(meth)acrylate. Also, when the particles (B) contain another polymer other than polymethyl(meth)acrylate, the amount of the other polymer may be 1% by weight or less based on the total amount of polymer in the particles (B).

[0026] Thus, the powder component of the dental composition of this embodiment may contain a predetermined ratio of polymethyl(meth)acrylate particles (A) containing a conjugated diene compound and particles (B) essentially consisting of polymethyl(meth)acrylate. The powder component may also contain a predetermined ratio of particles (A) in which a conjugated diene compound is incorporated, preferably at 5% by weight or more, into a polymethyl(meth)acrylate polymer, and particles (B) consisting of polymethyl(meth)acrylate that is essentially free of a conjugated diene compound. This improves the fluidity of the dental composition while maintaining good impact resistance after curing.

[0027] The weight ratio of particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound to particles (B) of polymethyl (meth)acrylate, i.e., (weight of particles (A)):(weight of particles (B)), may be 55:45 to 99:1, preferably 60:40 to 85:15. A weight ratio of particles (A) to particles (B) of 55:45, or a weight ratio of particles (A) greater than 55:45, can improve the impact resistance of the resulting cured product. A weight ratio of particles (A) to particles (B) of 99:1, or a weight ratio of particles (A) less than 99:1, can improve the fluidity of the dental composition and the flexural strength of the resulting cured product.

[0028] <Liquid component> The liquid component of the dental composition according to this embodiment may mainly contain a polymerizable monomer (resin matrix monomer). The polymerizable monomer contained in the liquid component is preferably a (meth)acrylate compound. As the (meth)acrylate, a (meth)acrylate monomer having one unsaturated double bond or a (meth)acrylate monomer having two or more unsaturated double bonds can be used.

[0029] Examples of (meth)acrylate monomers having one unsaturated double bond include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hydroxypropyl methacrylate, tetrahydrofurfuryl methacrylate, glycidyl methacrylate, 2-methoxyethyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, and acrylates thereof. Among these, it is preferable to use methyl methacrylate because it is inexpensive and has excellent polymerizability.

[0030] Examples of (meth)acrylate monomers having two or more unsaturated double bonds include ethylene glycol 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, and acrylates thereof, as well as methacrylates and acrylates having a urethane bond in the molecule.

[0031] The above-mentioned (meth)acrylate monomers may be used alone or in combination of two or more. The (meth)acrylate compound used as a liquid component may be appropriately determined depending on the application and method of use of the dental composition. As a liquid component of a dental composition for a denture base or the like, it is preferable to use, for example, methyl methacrylate as the main component and ethylene glycol dimethacrylate in combination, since this provides a crosslinking effect. In this case, the amount of ethylene glycol dimethacrylate in the (meth)acrylate monomer may be preferably 1 to 20 wt %, more preferably 5 to 15 wt %.

[0032] The dental composition of this embodiment may contain 60 to 80 parts by weight of the liquid component per 100 parts by weight of the powder component. Furthermore, the amount of the liquid component may be preferably greater than 60 to 80 parts by weight, more preferably 62 to 78 parts by weight, and even more preferably 65 to 75 parts by weight per 100 parts by weight of the powder component. In the dental composition of this embodiment, by using 60 parts by weight or more of the liquid component per 100 parts by weight of the powder component, fluidity is improved and operability is enhanced. Furthermore, by using 80 parts by weight or less of the liquid component, the impact resistance of the resulting cured product can be improved.

[0033] <Polymerization initiator> The dental composition according to this embodiment may contain a polymerization initiator in the powder component, the liquid component, or both. Examples of the polymerization initiator include a thermal polymerization initiator, a chemical polymerization initiator, and a photopolymerization initiator.

[0034] The chemical polymerization initiator may be a combination of an organic peroxide and a tertiary amine. Preferred organic peroxides include aromatic diacyl peroxides and peroxyesters that can be considered as esters of perbenzoic acid, such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-tolyl peroxide, t-butyl peroxybenzoate, di-t-butylperoxyisophthalate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di{(o-benzoyl)benzoylperoxy}hexane.

[0035] Examples of tertiary amines include p-tolyldiethanolamine, N,N-dimethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethylaniline, N-methyl-N-β-hydroxyaniline, N,N-di(β-hydroxyethyl)-aniline, N,N-di(β-hydroxyethyl)-p-toluidine, N,N-di(β-hydroxypropyl)-aniline, N,N-di(β-hydroxypropyl)-p-toluidine, ethyl N,N-dimethylaminobenzoate, and isoamyl N,N-dimethylaminobenzoate.

[0036] Further, examples of the chemical polymerization initiator include a combination of a pyrimidinetrione derivative, an organometallic compound, and an organic halogen compound. These can be used by blending the pyrimidinetrione derivative and the organic compound in one of the powder component and the liquid component, and the organic halogen compound in the other.

[0037] Examples of pyrimidinetrione derivatives include 1-cyclohexyl-5-ethylpyrimidinetrione (1-cyclohexyl-5-ethylbarbituric acid), 1-benzyl-5-phenylpyrimidinetrione, 5-butylpyrimidinetrione, 5-phenylpyrimidinetrione, 1,3-dimethylpyrimidinetrione, and 5-ethylpyrimidinetrione. Such pyrimidinetrione derivatives are preferred because they can reduce or prevent discoloration (yellowing) of dental compositions.

[0038] Examples of organometallic compounds include copper acetylacetonate (bis-2,4-pentanedionate copper), copper 4-cyclohexylbutyrate, cupric acetate, copper oleate, manganese acetylacetonate, manganese naphthenate, manganese octoate, cobalt acetylacetonate, cobalt naphthenate, lithium acetylacetonate, lithium acetate, zinc acetylacetonate, zinc naphthenate, nickel acetylacetonate, nickel acetate, aluminum acetylacetonate, calcium acetylacetonate, chromium acetylacetonate, iron acetylacetonate, sodium naphthenate, and rare earth octoate.

[0039] Examples of the organic halogen compound include dilauryl dimethyl ammonium chloride, lauryl dimethyl ammonium chloride, tetra-n-butyl ammonium chloride, trioctyl methyl ammonium chloride, benzyl dimethyl cetyl ammonium chloride, and benzyl dimethyl stearyl ammonium chloride.

[0040] As a photopolymerization initiator, a combination of a sensitizer and a reducing agent can be used. Examples of sensitizers include camphorquinone, benzil, diacetyl, benzil dimethyl ketal, benzil diethyl ketal, benzil di(2-methoxyethyl) ketal, 4,4'-dimethylbenzyl dimethyl ketal, anthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone, 1,2-benzanthraquinone, 1-hydroxyanthraquinone, 1-methylanthraquinone, 2-ethylanthraquinone, 1-bromoanthraquinone, thioxanthone, 2-isopropylthioxanthone, 2-nitrothioxanthone, 2-methylthioxanthone, and 2 ,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chloro-7-trifluoromethylthioxanthone, thioxanthone-10,10-dioxide, thioxanthone-10-oxide, benzoin methyl ether, benzoin ethyl ether, isopropyl ether, benzoin isobutyl ether, benzophenone, bis(4-dimethylaminophenyl) ketone, 4,4'-bisdiethylaminobenzophenone, derivatives of acylphosphine oxide, compounds containing an azide group, etc.

[0041] Tertiary amines are commonly used as reducing agents. Examples of tertiary amines include p-tolyldiethanolamine, N,N-dimethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethylaminoethyl methacrylate, triethanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, and isoamyl 4-dimethylaminobenzoate. Other reducing agents include benzoyl peroxide, sodium sulfinate derivatives, and organometallic compounds.

[0042] The photopolymerization initiator undergoes a polymerization reaction when irradiated with actinic rays such as ultraviolet light or visible light. As the light source, various ultra-high pressure, high pressure, medium pressure and low pressure mercury lamps, chemical lamps, carbon arc lamps, metal halide lamps, fluorescent lamps, tungsten lamps, xenon lamps, argon ion lasers, etc. are used.

[0043] When a thermal polymerization initiator is used, the same thermal polymerization initiator as that used in the preparation of the particles (A) can be used.

[0044] <Other ingredients> The dental composition of this embodiment may contain inorganic fillers, such as inorganic fillers obtained by coupling treatment of inorganic powders such as silica, to the extent that the functions of the components contained therein are not impaired. Furthermore, polymerization inhibitors, oxidation stabilizers, discoloration inhibitors, plasticizers, surfactants, antibacterial agents, UV absorbers, pigments, dyes, fibers, etc. may be added to one or both of the powder component and the liquid component as needed. The term "fiber" is used to represent the pseudo-capillaries in the denture base.

[0045] The above-mentioned other components may be added when preparing the particles (A) by polymerization. For example, a polymerization inhibitor, an oxidation stabilizer, a discoloration inhibitor, a plasticizer, a surfactant, an antibacterial agent, an ultraviolet absorber, a pigment, a dye, a fiber, or the like may be added to the monomer methyl (meth)acrylate during polymerization, as needed. [Example]

[0046] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0047] [Preparation of particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound] Particles (A1) to (A5) were prepared as particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound.

[0048] <Preparation of particles (A1)> Five parts by weight of styrene-butadiene rubber (trade name: KRATON D1192, manufactured by Kraton Corporation) having an average molecular weight of 150,000 was dissolved in 95 parts by weight of methyl methacrylate, and suspension polymerization was carried out using 0.5 parts by weight of benzoyl peroxide to obtain particles (A1) having an average particle size of 80 μm. The average particle size was a volume-based average particle size measured using a particle sizer (laser diffraction / scattering particle size distribution measuring device (HORIBA LA-950V2, manufactured by Horiba, Ltd.) (hereinafter, the average particle size of particles was measured in the same manner).

[0049] <Preparation of particles (A2)> Suspension polymerization was carried out in the same manner as for particles (A1), except that the amount of methyl methacrylate was changed to 90 parts by weight and the amount of styrene-butadiene rubber was changed to 10 parts by weight, to obtain particles (A2) with an average particle size of 80 μm.

[0050] <Preparation of particles (A3)> Suspension polymerization was carried out in the same manner as for particles (A1), except that the amount of methyl methacrylate was changed to 92.5 parts by weight and the amount of styrene-butadiene rubber was changed to 7.5 parts by weight, to obtain particles (A3) with an average particle size of 80 μm.

[0051] <Preparation of particles (A4)> Suspension polymerization was carried out in the same manner as for particles (A1), except that the amount of methyl methacrylate was changed to 97 parts by weight and the amount of styrene-butadiene rubber was changed to 3 parts by weight, to obtain particles (A4) with an average particle size of 80 μm.

[0052] <Preparation of particles (A5)> Suspension polymerization was carried out in the same manner as for particles (A1), except that the amount of methyl methacrylate was changed to 88 parts by weight and the amount of styrene-butadiene rubber was changed to 12 parts by weight, to obtain particles (A5) having an average particle size of 80 μm.

[0053] [Preparation of powder and liquid components] Example 1 A powder component was prepared by mixing 60 parts by weight of particles (A1), 40 parts by weight of polymethyl methacrylate particles (B) (trade name: ACRYCON AC, manufactured by Mitsubishi Rayon Co., Ltd.), 0.1 parts by weight of red cellulose fiber and red pigment combined, 1 part by weight of 1-cyclohexyl-5-ethylbarbituric acid, and 0.001 part by weight of copper bis-2,4-pentanedionate.

[0054] On the other hand, a liquid component was prepared by mixing 90 parts by weight of methyl methacrylate, 10 parts by weight of ethylene glycol dimethacrylate, 0.4 parts by weight of dilauryldimethylammonium chloride, 1 part by weight of N,N-dimethyl-p-toluidine, and 0.05 parts by weight of dibutylhydroxytoluene (BHT).

[0055] (Examples 2 to 12 and Comparative Examples 1 to 6) The type and amount of particles (A) and the amount of particles (B) were changed as shown in Table 1, and powder components were prepared in the same manner as in Example 1. Liquid components were prepared in the same manner as in Example 1. The amounts in the table are in parts by weight.

[0056] [evaluation] The flexural strength, impact resistance (fracture toughness), and fluidity of the dental compositions of Examples 2 to 11 and Comparative Examples 1 to 7 were evaluated as follows. The results are shown in Table 1.

[0057] <Liquidity> The liquid component and the powder component were mixed under the conditions shown in Table 1. The time from the start of mixing was measured with a stopwatch, and the fluidity of the mixture was confirmed 2 minutes after mixing.

[0058] Excellent: When the container containing the mixture is tilted, sufficient fluidity is maintained. Good: When the container containing the mixture is tilted, fluidity is maintained. Acceptable: When the container containing the mixture is tilted, the fluidity decreases due to the progression of swelling.

[0059] <Bending strength> The mixture obtained by mixing the liquid and powder components was poured into a pre-prepared plaster mold conforming to JIST 6501 (denture base resin) and then placed in water heated to 55°C and polymerized at 0.2 MPa for 30 minutes. After polymerization, the mixture was removed and subjected to a bending strength test conforming to JIST 6501. More specifically, test specimens measuring 64 mm in length, 10.0 ± 0.2 mm in width, and 3.3 ± 0.2 mm in thickness were prepared and immersed in 37°C water for 50 ± 2 hours. The specimens were then removed and immediately immersed in a 37°C water bath. A load was applied using a load plunger at a constant crosshead speed of 5 ± 1 mm / min, and the bending strength was calculated.

[0060] <Impact resistance (maximum stress intensity factor and total work of fracture)> The mixture obtained by mixing the liquid and powder components was poured into a pre-prepared plaster mold conforming to JIST 6501 (denture base resin) and then immersed in water heated to 55°C and polymerized at 0.2 MPa for 30 minutes. After polymerization, the mixture was removed and subjected to fracture toughness testing in accordance with JIST 6501. Specifically, test specimens measuring approximately 39 mm in length, 8.0 ± 0.2 mm in height, and 4.0 ± 0.2 mm in width were prepared. A 3.0 ± 0.2 mm notch was made in the center of the specimen using a diamond disc, and a sharp notch of 100–400 μm was made in the notch using a razor. The notched specimens were stored in a constant-temperature water bath at 37 ± 1°C for 168 hours (7 days) ± 2 hours. After immersion, the test specimens were removed and tested at a crosshead speed of 1.0±0.2 mm / min until the maximum load was exceeded and the load decreased to 5% of the maximum load or became smaller than 1.0±0.2 N. The maximum stress intensity factor and total work to fracture were then calculated.

[0061] [Table 1]

[0062] As shown in Table 1, dental compositions (Examples 1-12) containing a powder component containing 55-99 wt% particles (A) and 1-45 wt% particles (B) in weight ratios ranging from 55 to 99 wt% particles (A) and 1 to 45 wt% particles (B), with a liquid component of 60 to 80 wt% per 100 wt% powder component, exhibited excellent fluidity and the resulting cured products also exhibited excellent impact resistance (fracture toughness). Furthermore, compositions (Examples 1-11) containing a conjugated diene compound and polymethyl (meth)acrylate in a weight ratio of 5:95 to 10:90 in particles (A) exhibited excellent fluidity, cured products with excellent impact resistance, and cured products with excellent flexural strength. Furthermore, compositions (Examples 6-11) containing 65 wt% or more liquid component per 100 wt% powder component exhibited particularly excellent fluidity while maintaining good impact resistance and flexural strength.

Claims

1. A dental composition comprising a powder component and a liquid component, The amount of the liquid component is 60 to 80 parts by weight per 100 parts by weight of the powder component, The powder component is Particles (A) obtained by polymerizing methyl (meth)acrylate in the presence of a conjugated diene compound; and polymethyl (meth)acrylate particles (B), A dental composition, wherein the weight ratio of the amount of the particles (A) to the amount of the particles (B) is 55:45 to 99:

1.

2. 2. The dental composition according to claim 1, wherein a weight ratio of the conjugated diene compound to the polymethyl (meth)acrylate in the particles (A) is from 5:95 to 10:

90.

3. 3. The dental composition according to claim 1, wherein the conjugated diene compound is a styrene-butadiene rubber having a weight average molecular weight of 100,000 to 300,000.

4. 4. The dental composition according to claim 1, wherein the polymethyl(meth)acrylate particles (B) are methyl methacrylate particles.

5. The dental composition according to claim 1 , wherein the liquid component is a (meth)acrylate monomer.

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