Hardened components for dental use

Abstract

The present invention provides a dental curable composition suitable for use as a structural color-based composite resin (CR) that has high radiopaqueness in its hardened form, is suitable for aesthetic restoration, and is suitable as a low-flow type flowable CR with fluidity, low dripping, and good moldability, allowing the paste to be directly filled into the cavity from the tip of a needle. [Solution] A dental curable composition comprising: a radical polymerizable monomer component (A); spherical inorganic powder (b) having a specific average particle size and particle size distribution, consisting of spherical inorganic particles having a refractive index greater than that of (A) and its cured form; a photopolymerization initiator; and an X-ray opaque filler (D) consisting of crystalline rare earth metal fluoride particles, wherein the full width at half maximum of the maximum intensity peak derived from the crystalline rare earth metal fluoride in the X-ray diffraction pattern is 0.3° or more, wherein the X-ray opaque filler (D) is composed of aggregated X-ray opaque filler (D1) and dispersed X-ray opaque filler (D2) in predetermined proportions.

Description

Technical Field

[0001] The present invention relates to a dental curable composition that can be suitably used as a dental flowable composite resin.

Background Art

[0002] Dental curable compositions mainly contain a polymerizable monomer (monomer), an inorganic filler (inorganic filler), and a polymerization initiator. Among them, composite resin (hereinafter sometimes abbreviated as "CR") is one of the most frequently used materials in dental treatment as a material for repairing cavities after removing tooth defects and caries.

[0003] Repair using such dental composite resin (CR) has rapidly spread because it can reduce the amount of tooth substance cut, can impart a color tone equivalent to that of natural teeth, and is easy to operate. In recent years, due to improvements in mechanical strength and adhesion to teeth, it is used not only for repairing anterior teeth but also for molars to which high occlusal pressure is applied.

[0004] In recent years, flowable composite resins (flowable CRs) have been developed that can be filled into syringes equipped with needle tips, which have small holes, allowing paste to be directly filled into cavities from the tip of the needle. These CRs possess fluidity while achieving a certain level of hardened strength and aesthetics, making tooth restoration easier. As a result, they are increasingly used in clinical practice. Among these flowable CRs, there are low-flow types, mainly used in cases where occlusal surface reproduction is required, and high-flow types, mainly used for lining (applying a thin layer of paste to the cavity) (to seal the openings of dentinal tubules that are open to the cavity and form a layer to prevent external stimuli from reaching the pulp). Therefore, in addition to good operability when dispensed from a syringe equipped with a needle tip, flowable CRs require the desired fluidity depending on the application. For example, low-flow composite resins are required to have low "sagging properties," which are evaluated as the tendency to drip when applied to a vertical surface, and good "formability" (the property of being resistant to deformation due to natural flow when left at rest, and being able to maintain its shape) that prevents deformation between shaping after filling and hardening. On the other hand, in high-flow types, while having an appropriate consistency is important, formability is not as important ("sagging properties" may increase), and rather high "flowability" that allows it to spread naturally on a horizontal surface (in an unloaded state) is required. Among flowable composite resins, the low-flow type described above is used in a wide range of cases because it allows for cavity filling and reproduction of the occlusal surface.

[0005] Flowable composite resins improve fluidity and dischargeability from syringes by reducing the amount of inorganic powders and granules they contain. However, this increased fluidity can sometimes make it difficult to achieve good formability.

[0006] To address these challenges, Patent Document 1 discloses a technique for improving the various properties of composite resins by using two types of inorganic powders in a specific ratio, each exhibiting opposite zeta potentials (in water) and possessing specific average particle sizes and specific surface areas. In the example, a polymerizable monomer, a silica-based composite oxide with an average particle size of 50 nm to 1 μm, and a specific surface area of ​​25 to 100 m² are used. 2 A dental hardening composition containing a crystalline rare-earth metal fluoride at a concentration of / g is described as having good dispensability (having a consistency suitable for dispensing from a syringe) and exhibiting moderate fluidity that suppresses paste dripping.

[0007] Incidentally, in order to perform highly aesthetic restorations with composite resin (CR), it is common practice to determine the color (hue and shade) of the tooth to be restored (this color determination is sometimes called "shade taking"), select a CR color that matches the determined color, and perform the restoration. In order to perform highly aesthetic restorations that faithfully reproduce the color variations depending on the part of the tooth, it was necessary to layer multiple CRs of different colors. Furthermore, while CR is usually colored by mixing pigment or dye substances into the CR, these substances can fade or change color due to deterioration over time in the hardened body after treatment. As time passes after the restoration, the appearance of the restored area may no longer match that of a natural tooth.

[0008] Recently, a type of CR (hereinafter, CR that exhibits such structural color) has been proposed and is attracting attention. This type uses an inorganic filler containing spherical inorganic particles having a specific average particle diameter and particle size distribution, and by making the refractive index of the spherical inorganic particles greater than that of the resin matrix that forms the matrix when cured, it exhibits a structural color that develops in a predetermined color tone independent of the angle of incidence of light due to light interference and scattering, etc. (See Patent Documents 2 and 3). The above-mentioned structural color CR is known to have the following excellent features: (1) Since it does not use dyes or pigments, it is less prone to discoloration over time; (2) Depending on the average particle size of the spherical inorganic powder used, it exhibits a specific color tone that does not depend on the angle of incidence of light, and in particular, when spherical inorganic powder with an average primary particle size of 230 to 350 nm is used, it can be colored to yellow to red, which is the same color as dentin; and (3) Since the hardened body has appropriate transparency, it is easy to harmonize with the color of the tooth to be restored, and it is possible to restore a tooth with an appearance close to that of a natural tooth for a wide range of tooth colors using one type of composite resin without the need for complicated shade taking or shade selection of composite resin.

[0009] The polymerization-curable composition constituting the above structural color system CR satisfies the following conditions (a) and (b), but it is known that satisfying the following condition (c) more reliably yields a cured product that exhibits the desired structural color (see Patent Document 2).

[0010] (a) Contains polymerizable monomer (A), inorganic filler (B), and photopolymerization initiator (C) as constituent components.

[0011] (i) The inorganic filler (B) is It consists of an aggregate of inorganic spherical particles having a predetermined average primary particle diameter within the range of 100 to 1000 nm. Each of the inorganic spherical particles constituting the aggregate is substantially composed of the same substance, and in the number-based particle size distribution of the aggregate, 90% or more of the total number of particles are present within a range of±5% around the above-mentioned predetermined average primary particle diameter, including one or more "Groups of spherical Particles having Identical Diameter" (G-PID). (ii) When the number of the above-mentioned one or more "Groups of spherical Particles having Identical Diameter" is a, each "Group of spherical Particles having Identical Diameter" is designated as G-PID m (where m is 1 when a is 1, and a natural number from 1 to a when a is 2 or more.) When represented as such, for each G-PID in the case where a is 2 or more m the substances constituting the individual particles may be different from each other, and in this case, for each G-PID m the average primary particle diameters are different from each other by 25 nm or more, and (iii) Let the refractive index of the cured product of the polymerizable monomer component (A) at 25°C be n (MX) and the refractive index of the inorganic spherical particles constituting each G-PID m at 25°C be n (G-PIDm) . Then, for any n (G-PIDm) [[ID=! n (MX) < n (G-PIDm) the relationship holds. All of the above conditions are satisfied.

[0012] (c) For a cured body obtained by curing a polymerization curable composition, the radial distribution function g(r), which represents the probability that another inorganic spherical particle exists at a distance r from the center of any inorganic spherical particle dispersed in the cured body, is determined based on a scanning electron microscope image with the interior surface of the cured body as the observation plane, and is based on the following: the average particle density of the inorganic spherical particles in the observation plane: <ρ>, the number of inorganic spherical particles in the region between a circle at a distance r from any inorganic spherical particle in the observation plane and a circle at a distance r+dr: dn, and the area of ​​the region: da (where da = 2πr·dr). Formula: g(r)={1 / 〈ρ〉}×{dn / da} When expressed as such, the arrangement structure of inorganic spherical particles in the hardened body has a short-range ordered structure that satisfies the following conditions 1 and 2.

[0013] [Condition 1] In a radial distribution function graph that shows the relationship between r / r0 and g(r) corresponding to r at that time, with the x-axis being a dimensionless number (r / r0) normalized by dividing the distance r from the center of any inorganic spherical particle dispersed in the hardened body by the average particle diameter r0 of all inorganic spherical particles dispersed in the hardened body, and the y-axis being the radial distribution function g(r), the nearest neighbor particle distance r1, defined as the r corresponding to the peak top of the peak closest to the origin among the peaks appearing in the radial distribution function graph, is a value of 1 to 2 times the average particle diameter r0 of all inorganic spherical particles dispersed in the hardened body of the mixture.

[0014] [Condition 2] When the next nearest neighbor particle distance: r2 is defined as the peak r corresponding to the peak top of the second nearest peak from the origin among the peaks appearing in the radial distribution function graph, the minimum value of the radial distribution function: g(r) between the nearest neighbor particle distance: r1 and the next nearest neighbor particle distance: r2 is a value between 0.56 and 1.10.

[0015] According to Patent Document 3, the colored light due to interference in the cured body occurs in areas where the constituent particles are relatively regularly arranged, while the colored light due to scattering occurs in areas where the constituent particles are disorderly dispersed. Furthermore, regarding [Condition 1], it is explained that when r1 is less than 1 times r0, there is a lot of overlap between particles in the plane, and when r1 is greater than 2 times r0, particles disappear from the vicinity of the selected central inorganic particle, resulting in a loss of short-range order and the inability to exhibit structural color. Regarding [Condition 2], it is explained that when the minimum value is less than 0.56, the long-range order of the arrangement structure of the inorganic spherical particles increases, not only increasing the dependence of the exhibited structural color on the incident angle of light, but also increasing the saturation of the cured body, making it difficult to obtain color matching when used as a dental filling material. On the other hand, when the minimum value exceeds 1.10, the arrangement structure of the inorganic spherical particles becomes random, making it difficult to obtain the desired reflective performance and making it difficult to exhibit the desired structural color.

[0016] Furthermore, for the reason that the short-range ordered structure described above can be obtained more easily and reliably, it is preferable that at least a portion of one or more groups of spherical particles of the same particle size be formulated as an organic-inorganic composite filler (i.e., an organic-inorganic composite filler containing only a single G-PID) which includes one type of spherical particle group of the same particle size and a resin whose refractive index at 25°C is smaller than that of the inorganic spherical particles constituting the one type of spherical particle group of the same particle size at 25°C, and which does not contain any other groups of spherical particles of the same particle size other than the one type of spherical particle group of the same particle size.

[0017] In polymerizable hardening compositions that satisfy conditions (a) to (c) above (hereinafter also referred to as "existing structural color dental hardening compositions"), when multiple groups of spherical particles of the same particle size (G-PIDs) are included, each G-PID develops a structural color in the hardened body corresponding to its average primary particle size. Therefore, it is possible to control the overall color tone by combining the G-PIDs that are included. This is thought to be because, when multiple G-PIDs are included, there is a certain difference in their average primary particle sizes, allowing inorganic spherical particles belonging to different G-PIDs to be dispersed in a short-range ordered structure that enables each G-PID to exhibit its own structural color without mutual substitution.

[0018] In general, inorganic oxide filling materials, particularly silica-based filling materials, are used as filling materials in hardening compositions used as composite resins (CR), including existing structural color-based dental hardening compositions. However, silica-based filling materials have low radiopaqueness. Therefore, during X-ray or CT scans during dental treatment, the hardened material in the cavity is not visualized, making it difficult to identify the treated area.

[0019] On the other hand, as a means of improving the radiopaqueness of hardened bodies of hardened compositions used in various applications, such as the dental compositions exemplified above, a method of using inorganic fillers containing atoms with large atomic numbers is known. For example, Patent Document 4 proposes a technique of using a filler made of fluorides of rare earth metals with atomic numbers 57 to 71. However, if the amount of the above filler is increased to improve radiopaqueness, the transparency of the hardened body after curing decreases, making aesthetic restoration difficult. As a technology to solve this problem, Patent Document 5 discloses an X-ray opaque filler that can suppress the decrease in transparency of the hardened body after curing, characterized in that it consists of a first powder (hereinafter also referred to as "low-crystalline rare-earth fluoride powder") which mainly contains crystalline rare-earth metal fluoride particles and has a full width at half maximum of the maximum intensity peak originating from the crystalline rare-earth metal fluoride particles in the X-ray diffraction pattern of 0.3° or more, and a powder selected from the group consisting of a second powder obtained by surface-treating the first powder. [Prior art documents] [Patent Documents]

[0020] [Patent Document 1] International Publication No. 2023 / 085201 brochure [Patent Document 2] International Publication No. 2017 / 069274 Brochure [Patent Document 3] International Publication No. 2020 / 050123 Brochure [Patent Document 4] Special Publication No. 3-17803 [Patent Document 5] International Publication No. 2023 / 042598 Brochure [Overview of the Initiative] [Problems that the invention aims to solve]

[0021] The radiopaque filling material (low-crystalline rare earth fluoride powder) disclosed in Patent Document 5 has the excellent features described above. However, when the present inventors tried incorporating it into existing structural color dental curable compositions, they found that a large amount of radiopaque filling material was necessary to obtain high radiopaqueness, and in that case, it became difficult to achieve the desired structural color.

[0022] For example, in order to have low sagging and good formability, which are important for low-flow type flowable CR, the specific surface area is 25 to 100 m² as shown in Patent Document 1. 2 When we attempted to prepare a structural color system CR containing low-crystalline rare earth fluoride powders and silica-based composite oxide powders at a concentration of / g, we confirmed that high X-ray contrast properties can adversely affect the expression of structural color (see Comparative Example 15 described later).

[0023] The present inventors have previously investigated the problem of inhibition of structural color expression due to the incorporation of low-crystalline rare-earth metal fluoride powders and have already proposed that this problem can be solved by incorporating low-crystalline rare-earth metal fluoride powders not directly, but as "organically composited low-crystalline rare-earth fluoride powders" consisting of organic-inorganic composite particles compounded with an organic resin. In other words, even when the amount of low-crystalline rare-earth fluoride powders is reduced, high X-ray opacity can be imparted, and this does not significantly adversely affect the expression of the desired structural color CR (Japanese Patent Application No. 2023-29645).

[0024] However, when the above-mentioned organically composited low-crystalline rare-earth fluoride powders were incorporated into existing structurally colored dental curable compositions, it became clear that they exhibited poor sagging and good moldability when attempting to provide adequate fluidity as a flowable composite resin (see Comparative Example 14 described later). Furthermore, it became clear that the radiopaque filling material may settle when stored for a long period (e.g., 3 months at 50°C).

[0025] In view of these circumstances, the present invention aims to provide a dental curable composition that can be suitably used as a structural color-based composite resin (CR) capable of aesthetic restoration, has high radiopaqueness in its cured form, and can be used as a low-flow type flowable CR with fluidity, low dripping, good moldability, and good storage stability, allowing the paste to be directly filled into the cavity from the tip of a needle. [Means for solving the problem]

[0026] The present invention solves the above problems, and the first embodiment of the present invention is a photopolymerizable composition comprising a monomer component (A) consisting of one radical polymerizable monomer or a mixture of multiple radical polymerizable monomers, an inorganic filler (B), and a photopolymerization initiator (C), (1) The above (B) consists of an aggregate of inorganic spherical particles whose uniform primary particle diameter, as measured by electron microscopy, is a predetermined value within the range of 100 to 1000 nm, wherein the individual inorganic spherical particles constituting the aggregate are composed of substantially the same substance, and the aggregate contains one or more "groups of spherical particles of the same particle size" (G-PID) in which 90% or more of the total number of particles in the particle size distribution based on the number of particles are located within 5% before or after the predetermined value of the average primary particle diameter. 1) When the number of the one or more G-PIDs is a, each G-PID is ordered in ascending order of its average primary particle diameter. m (However, m is 1 when a is 1, and a natural number from 1 to a when a is 2 or greater.) When expressed as such, each G-PID when a is 2 or greater m The materials constituting each individual particle may be different from each other, and in that case each G-PID m The average primary particle diameters differ from each other by more than 25 nm. 2) Let n be the refractive index of the sodium d line at 25°C, and let n be the refractive index of the cured monomer component (A). (MX) And each of the above G-PID m The refractive index of the inorganic spherical particles constituting the is n (G-PIDm) When that is the case, (G-PIDm) Even for n (MX) <n(G-PIDm) All conditions for the relationship to hold are satisfied, (2) For a cured body obtained by curing the photopolymerizable composition, the radial distribution function g(r), which represents the probability that another inorganic spherical particle exists at a distance r from the center of any inorganic spherical particle dispersed in the cured body, is determined based on a scanning electron microscope image with the interior surface of the cured body as the observation plane, and is based on the following: the average particle density of the inorganic spherical particles in the observation plane: <ρ>, the number of inorganic spherical particles in the region between a circle at a distance r from any inorganic spherical particle in the observation plane and a circle at a distance r+dr: dn, and the area of ​​the region: da (where da = 2πr·dr). Formula: g(r)={1 / 〈ρ〉}×{dn / da} When expressed as such, the arrangement structure of inorganic spherical particles in the hardened body is 1) In a radial distribution function graph where the x-axis is the dimensionless number (r / r0) normalized by dividing the distance r from the center of any inorganic spherical particle dispersed in the hardened body by the average particle diameter r0 of all inorganic spherical particles dispersed in the hardened body, and the y-axis is the radial distribution function g(r), the relationship between r / r0 and g(r) corresponding to r at that time is shown, and the nearest neighbor particle distance r1, defined as the r corresponding to the peak top of the peak closest to the origin among the peaks appearing in the radial distribution function graph, is a value of 1 to 2 times the average particle diameter r0 of all inorganic spherical particles dispersed in the hardened body of the mixture, and 2) When the next nearest neighbor particle distance: r2 is defined as the peak r corresponding to the peak top of the second nearest neighbor particle distance among the peaks appearing in the radial distribution function graph, the minimum value of the radial distribution function: g(r) between the nearest neighbor particle distance: r1 and the next nearest neighbor particle distance: r2 is a value between 0.56 and 1.10. Having a short-range ordered structure that satisfies the following conditions, The dental curing composition, comprising a photopolymerizable and curable composition, has the following characteristics:

[0027] In other words, (3) The viscosity of the monomer component (A) at 25°C is 100 to 1000 mPa·s, (4) All of the one or more G-PIDs consist of inorganic spherical powder (b) having an average primary particle diameter in the range of 230 to 500 nm, which is composed of inorganic spherical particles whose polarity of the zeta potential measured in water is negative. 1) A part of (b) above (b1) is formulated as (B1), which consists of at least one of the group comprising primary particles (b1-1), a granular material composed of aggregated particles of the primary particles (b1-2), and a composite aggregated granular material (E) composed of aggregated particles of the primary particles and other inorganic particles (e), wherein the granular material (b1-2) and the composite aggregated granular material (E) may be crushed and dispersed in the dental curable composition. 2) The remainder of (b) above (b2) is a specific single G-PID n (However, n is 1 when a is 1, and any natural number from 1 to a when a is 2 or greater.) Inorganic spherical powder (b2 n ) is dispersed in a resin matrix having a refractive index smaller than that of the constituent particles of the powder, (b2 n A composite that does not contain (b2) other than ) and the inorganic spherical powder (b2) relative to the total mass of the composite n It is included as one or more organic-inorganic composite powders (B2) composed of particles made of a composite whose average inorganic content, defined by the total mass of ), is 30 to 95% by mass, 3) The total content of (B1) and one or more of (B2) per 100 parts by mass of (A) is 150 to 300 parts by mass, and the content of one or more of (B2) in the total content is 50 to 70% by mass. (5) The (B) further comprises an X-ray opaque filler (D) comprising an aggregated X-ray opaque filler (D1) and a dispersed X-ray opaque filler (D2), 1) Both (D1) and (D2) are composed of crystalline rare earth metal fluoride particles that exhibit a positive zeta potential as measured in water, and the average primary particle size is 1 to 300 nm, and the full width at half maximum of the maximum intensity peak originating from the crystalline rare earth metal fluoride in the X-ray diffraction pattern is 0.3° or more, and the low crystalline rare earth fluoride powder (d) is used as the active ingredient. 2) The (D1) is composed of aggregated particles formed by the aggregation of primary particles constituting the low-crystalline rare-earth fluoride powder (d1) which is the active ingredient, and consists of low-crystalline rare-earth metal fluoride aggregated powder (d1-1) in which the average agglutinator diameter, defined as the median diameter in the volume-based particle size distribution measured by laser diffraction-scattering, is 1 to 30 μm, and the (d1-1) is included as aggregated particles in the dental curable composition. 3) The (D2) consists of primary particles (d2-2) of (d2) contained in a mixed inorganic powder (E1) having an average aggregate particle diameter of 1 to 50 μm, which consists of non-aggregated powder (d2-1) composed of primary particles constituting the low-crystalline rare earth fluoride powder (d2) that constitutes the active ingredient, and / or aggregated particles (e1) of the primary particles constituting (d2) and at least a portion of the constituent particles of (b1-3), wherein the (D2) contains (d2-1), and when the (D2) contains (d2-1), the (d2-1) is contained in the dental curable composition in a dispersed state as primary particles, and when the (D2) contains (d2-2), the (d2-2) is contained in the dental curable composition in a dispersed state as primary particles which are the pulverized product of the aggregated particles (e1). 4) The total content of (d) and the total content of (d2) per 100 mass of (A) are (d): 30 to 75 parts by mass and (d2): 5 to 25 parts by mass. This is a dental curable composition characterized by the following:

[0028] In the above-described form of dental curable composition (hereinafter also referred to as "the dental curable composition of the present invention"), it is preferable to provide a cured body that exhibits a predetermined structural color regardless of the angle of incidence of light.

[0029] Furthermore, it is preferable that the inorganic spherical particles (b) are made of a silica-based inorganic compound.

[0030] Furthermore, it is preferable that the average value of the total mass of the non-aggregated particles (d2-2) relative to the total mass of the inorganic spherical particles (b1-3) contained in each of the mixed aggregated particles (e1) constituting the mixed inorganic powder (E1) is within the range of 20 to 300 parts by mass.

[0031] Furthermore, it is preferable that the content of the photopolymerization initiator (C) per 100 parts by mass of (A) is 0.01 to 10, and that (C) contains 0.01 to 3.0 parts by mass of a tertiary amine compound (F) containing an aromatic amine compound containing a dimethylamino group per 100 parts by mass of (A).

[0032] A second embodiment of the present invention is a method for producing a dental curable composition of the present invention, The process includes a kneading step of kneading the monomer component (A); the powder (b1-1) and / or the powder (b1-2); the one or more organic-inorganic composite powder (B2); the non-aggregated powder (d2-1) and / or the mixed inorganic powder (E1); the low-crystallinity rare-earth metal fluoride aggregated powder (d1-1); and the photopolymerization initiator (C), In the kneading step, the amounts of each component (B2), (d1-1), and the photopolymerization initiator (C) relative to 100 parts by mass of (A) are set to (B2): 75 to 210 parts by mass, (d1-1): 5 to 70 parts by mass, and (C): 0.01 to 10 parts by mass, respectively. The amount of (b1-1) and / or (b1-2), and (d2-1) and / or (E1) relative to 100 mass of (A) is If (E1) is not included, the total amount of (b1-1) and (b1-2) shall be 45 to 150 parts by mass, and (d2-1) shall be 5 to 25 parts by mass. When incorporating (E1) as described above, the total amount of (b1-3) contained in (b1-1), (b1-2), and (E1) shall be 45 to 150 parts by mass, and the total amount of (d2-2) contained in (d2-1) and (E1) shall be 5 to 25 parts by mass. The method described above (hereinafter also referred to as "the manufacturing method of the present invention") is characterized by the above.

[0033] The manufacturing method of the present invention is a manufacturing method of the present invention that incorporates (E1), wherein the kneading step is a first kneading step in which (E1) or (E1) and (d2-1) are added to 100 parts by mass of (A) in such an amount that the total amount of (d2-1) and (d2-2) contained therein becomes a predetermined amount of (d2), and kneaded to obtain a paste in which (d2-1) and (d2-2) are uniformly dispersed as primary particles, Preferably, the process includes a second kneading step in which a predetermined amount of (d1-1) is added to the paste obtained in the first kneading step, and the mixture is kneaded in a manner that does not cause the aggregated particles constituting (d1-1) to break down.

[0034] A third embodiment of the present invention is a dental composite resin comprising the dental curable composition of the present invention, which provides a cured body in which the contrast ratio T, defined as the ratio of Yb (Yb measured under a black background) to Yw (Yw measured under a white background) using a colorimeter, is 0.20 to 0.50 for a 1 mm thick cured body sample, which serves as an indicator of the transparency of the cured body of the dental curable composition. In the dental composite resin of the above form (hereinafter also referred to as "the dental composite resin of the present invention"), it is preferable that the "flow value," defined as the diameter of paste spread (mm) when 0.1 g of the dental hardening composition is dispensed onto a glass plate and then left to stand horizontally in a 37°C incubator for 2 minutes, is 3.0 to 8.0 (mm), and that the "sag value," defined as the distance the paste moves (mm) when 0.03 g of the dental hardening composition is dispensed onto a glass plate and then left to stand vertically in a 37°C incubator for 1 minute, is 2.0 (mm) or less.

[0035] Furthermore, it is preferable to provide a hardened body in which the X-ray contrastability (%Al) of the hardened body sample, calculated from the brightness when a 1 mm thick hardened body sample and an aluminum step wedge are observed using a tabletop X-ray transmission inspection device, is 200 (%Al) or higher. [Effects of the Invention]

[0036] The dental curable composition of the present invention can obtain excellent effects such as high radiopaqueness, fluidity that allows paste to be directly filled into the cavity from the tip of the needle, low dripping, and good moldability without impairing the excellent characteristics of structural color CRs made from existing structural color dental curable compositions. [Modes for carrying out the invention]

[0037] As mentioned above, when organically compounded low-crystalline rare-earth fluoride powders are incorporated into existing structural-colored dental curable compositions, radiopaqueness can be imparted without significantly adversely affecting the expression of structural color. However, a paste exhibiting low sagging and good moldability has not yet been obtained. The inventors considered that if G-PID is compounded with an organic-inorganic compound, the short-range order between G-PID constituent particles will not be disrupted by the presence of different particles, reducing the contact area with monomer components and thus lowering fluidity. They also observed that rare earth metal fluoride particles tend to have higher X-ray contrast when they are in clumps rather than finely dispersed (when comparing the same amount of compounding), and that finely dispersing some of the rare earth metal fluoride particles contributes to lower fluidity. Therefore, they investigated whether it would be possible to improve X-ray contrast while suppressing adverse effects on the transparency and structural color expression of the cured product, and to ensure fluidity suitable for use as a low-flow type flowable CR, while also achieving low sagging and good formability, even without compounding the low-crystallinity rare earth metal fluoride powder and granules with an organic-inorganic compound, by dispersing some of it without compounding it with an organic-inorganic compound, and by agglomerating some of the low-crystallinity rare earth fluoride powder and granules and dispersing some of it as non-aggregated particles.

[0038] Specifically, the total amount of one or more G-PIDs, the ratio of those that form organic-inorganic composites (B2) to those that do not (B1), the total amount of low-crystallinity rare-earth metal fluoride particles (d), their primary particle size and aggregated particle size, and the ratio of those that aggregate on their own (d1) to those that do not aggregate on their own (d2) were changed, and the properties of the resulting paste, the structural color development and X-ray contrast properties of the cured body were evaluated. As a result, the conditions under which the desired effects could be obtained were identified, and the present invention was completed.

[0039] Although the reason for obtaining such effects is not clear, it is presumed that when the conditions specified in the present invention are satisfied, the decrease in "concentration" is suppressed by incorporating a certain proportion of the G-PID and (d) in an organic-inorganic composite or aggregated state, and that the disruption of the short-range order described in condition (c), which is a condition for existing structural color dental curable compositions, is suppressed, and furthermore, the sagging is reduced and the moldability is improved due to the formation of a network accompanying the electrostatic interaction between the constituent particles of (B1) that are not organic-inorganic composite and the constituent particles of (d2) that are not aggregated on their own.

[0040] Thus, the dental curable composition of the present invention is characterized in that, in a structural color dental curable composition using organic-inorganic composite powders disclosed in Patent Document 3, a system that satisfies specific conditions is selected, and an X-ray opaque filling material that satisfies specific conditions is further blended in such a way that it satisfies specific conditions, thereby making it suitable for use as a low-flow type flowable CR with high X-ray contrast properties. Therefore, after explaining the existing structural color dental curable composition that forms the basis of the dental curable composition of the present invention, the features of the dental curable composition of the present invention will be explained in detail.

[0041] In this specification, unless otherwise specified, the notation "x~y" using numerical values ​​x and y means "greater than or equal to x and less than or equal to y". If a unit is attached only to the numerical value y in such notation, that unit shall also apply to the numerical value x. Furthermore, in this specification, the term "(meth)acrylic" means both "acrylic" and "methacrylic". Similarly, the term "(meth)acrylate" means both "acrylate" and "methacrylate", and the term "(meth)acryloyl" means both "acryloyl" and "methacryloyl".

[0042] 1. Existing structural color dental curable composition As described above, the existing structural color dental curable composition is a dental curable composition comprising a monomer component (A) consisting of one radical polymerizable monomer or a mixture of multiple radical polymerizable monomers, an inorganic filler (B), and a photopolymerization initiator (C), which corresponds to condition (a) in Patent Document 2, and satisfies the following conditions (1) and (2) {corresponding to conditions (b) and (c) in Patent Document 2}, and is a dental curable composition that exhibits a structural color that develops to a predetermined color tone independent of the angle of incidence of light by utilizing light interference and scattering, etc.

[0043] (1) The inorganic filler consists of inorganic spherical powders having a predetermined average primary particle diameter in the range of 100 to 1000 nm, and includes one or more “groups of spherical particles of the same particle size”: G-PID, which are aggregates of spherical inorganic particles, in which 90% or more of the total number of particles in the particle size distribution based on the number of particles are located in the range of 5% before or after the predetermined average primary particle diameter. 1) Let a be the number of G-PIDs contained in the structurally colored dental curable composition, and each G-PID be listed in order of increasing average primary particle size. m (However, m is 1 when a is 1, and a natural number from 1 to a when a is 2 or greater.) When expressed as such, each G-PID when a is 2 or greater m The average primary particle diameters differ from each other by more than 25 nm. 2) Let n be the refractive index for sodium d line at 25°C, and let n be the refractive index of the cured polymerizable monomer component. (MX) And each of the above G-PID m The refractive index of the inorganic spherical granules that make up the structure is n (G-PIDm) When that is the case, (G-PIDm) Even in response to, n (MX) <n (G-PIDm) The following relationship holds true.

[0044] (2) For a hardened body obtained by hardening an existing structural color dental hardening composition, the radial distribution function g(r) representing the probability that another inorganic spherical particle exists at a distance r from the center of any inorganic spherical particle dispersed in the hardened body is determined based on a scanning electron microscope image with the interior surface of the hardened body as the observation plane, and is based on the average particle density of the inorganic spherical particles in the observation plane: <ρ>, the number of inorganic spherical particles present in the region between a circle at a distance r from any inorganic spherical particle in the observation plane and a circle at a distance r+dr: dn, and the area of ​​the region: da (where da = 2πr·dr). Formula: g(r)={1 / 〈ρ〉}×{dn / da} When expressed as such, the arrangement structure of inorganic spherical particles in the hardened body is 1) In a radial distribution function graph where the x-axis is the dimensionless number (r / r0) normalized by dividing the distance r from the center of any inorganic spherical particle dispersed in the hardened body by the average particle diameter r0 of all inorganic spherical particles dispersed in the hardened body, and the y-axis is the radial distribution function g(r), the relationship between r / r0 and g(r) corresponding to r at that time is shown, and the nearest neighbor particle distance r1, defined as the r corresponding to the peak top of the peak closest to the origin among the peaks appearing in the radial distribution function graph, is a value of 1 to 2 times the average particle diameter r0 of all inorganic spherical particles dispersed in the hardened body of the mixture, and 2) When the next nearest neighbor particle distance: r2 is defined as the peak r corresponding to the peak top of the second nearest neighbor particle distance among the peaks appearing in the radial distribution function graph, the minimum value of the radial distribution function: g(r) between the nearest neighbor particle distance: r1 and the next nearest neighbor particle distance: r2 is a value between 0.56 and 1.10. It has a short-range ordered structure that satisfies the following conditions.

[0045] Here, the radial distribution function g(r) is a well-known function for determining the probability of another particle existing at a distance r from any given particle, and is defined by equation (1) below. g(r)={1 / <ρ>}×{dn / da}···(1) In equation (1) above, <ρ> represents the average particle density of particles in a plane, dn represents the number of particles in the region between two circles centered on an arbitrary particle in the plane, with radii of r and r+dr, respectively, and da represents the area of ​​the above region, which is 2πr·dr. Furthermore, the radial distribution function g(r) is generally represented by a radial distribution function graph in which the distance r is plotted on the x-axis (distance axis) and the value of g(r) at that r {calculated result from equation (1) above} is plotted on the y-axis (vertical axis), or by a radial distribution function graph in which a dimensionless number normalized by dividing r by the average particle diameter is plotted on the distance axis and the value of g(r) at r corresponding to the x-axis value (calculated result from the above equation) is plotted on the y-axis (vertical axis).

[0046] The components of the existing structural color dental curing compositions described below are essentially the same as those in Patent Documents 2 and 3, except for the characteristics described later, but these will be briefly explained below.

[0047] 1-1. Monomer component (A) The monomer component (A) consists of one radical polymerizable monomer or a mixture of multiple radical polymerizable monomers. Any radical polymerizable monomer used in dental curable compositions can be used as the radical polymerizable monomer, provided it satisfies the above conditions. For ease of handling and physical properties (mechanical properties and, in dental applications, adhesion to tooth structure) when used as a dental filling and restorative material, it is preferable to use a (meth)acrylic compound as the radical polymerizable monomer. Furthermore, when used as a CR, it is preferable that the monomer component (A) consists of a (meth)acrylate monomer that does not have an acidic group.

[0048] Examples of (meth)acrylic compounds that can be suitably used include (meth)acrylic acid, methyl (meth)acrylate, n-butyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2,2-bis[(3-methacryloyloxy-2-hydroxypropyloxy)phenyl]propane, 2,2-bis(4-methacryloyloxydiethoxyphenyl)propane, 2,2-bis(4-methacryloyloxytetraethoxyphenyl)propane, 2,2-bis(4-methacryloyloxypentaethoxyphenyl)propane, and 2,2-bis[(4-methacryloyloxypentaethoxyphenyl)propane. Examples include [cryloyloxypolyethoxy)phenyl]propane, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, nonamethylenediol dimethacrylate, neopentyl glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-bis(methacrylateethyloxycarbonylamino)trimethylhexane, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, and the like.

[0049] 1-2. Inorganic filler (B) and G-PID The inorganic filler (B) comprises one or more “groups of spherical particles of the same particle size” (G-PID). Here, each inorganic spherical particle constituting the G-PID is composed of the same or substantially the same material.

[0050] The individual inorganic spherical particles constituting G-PID can be any of the following, without particular limitation, that are used as fillers in conventional dental curing compositions: amorphous silica, quartz, titania, zirconia, metal oxides such as chromium oxide, iron oxide, and tungsten oxide; or composite oxides such as silica-zirconia, silica-titania, silica-titania-barium oxide, silica-titania-zirconia, borosilicate glass, aluminosilicate glass, and fluoroaluminosilicate glass. It is preferable that the particles be composed of silica-based composite oxides because the refractive index can be easily adjusted and, furthermore, because the particle surface has a large amount of silanol groups, surface modification can be easily performed using silane coupling agents, etc. Silica-based inorganic compounds mean inorganic compounds containing silica. Among silica-based inorganic compounds, silica-titanium group element oxide composite oxides such as silica-zirconia, silica-titania, silica-titania-barium oxide, and silica-titania-zirconia are preferred because they are expected to have an effect of further enhancing X-ray contrast properties, and silica-zirconia is the most preferred because it yields a hardened body with excellent wear resistance. In addition, in silica-titanium group element oxide composite oxides, the refractive index can be adjusted in the range of approximately 1.45 to 1.58 depending on the silica content.

[0051] Each G-PID of one or more G-PIDs m The average primary particle diameter in this context is determined by electron microscopy, specifically scanning electron microscopy, as follows: A scanning electron microscope (e.g., Philips XL-30S) is used to take photographs of the powder at a magnification of 5,000 to 100,000x. Image analysis software (e.g., IP-1000PC, product name; Asahi Kasei Engineering Co., Ltd.) is used to process the captured images. From the 100 or more particles observed within a unit field of view, n particles (where n is a natural number greater than or equal to 30) are arbitrarily selected to have the maximum diameter of each particle: x i (Units are nm. i represents a natural number from 1 to n.) Measure the values ​​and sum them up: Σx i From the following formula x AV =( Σxi ) / n x is obtained by AV It means...

[0052] Furthermore, "spherical" does not necessarily mean perfectly spherical; it is sufficient if it is approximately spherical. Specifically, it means that the average uniformity, determined as follows, is 0.6 or higher, preferably 0.8 or higher. That is, a photograph of the powder is taken with a scanning electron microscope, and for each of the n (≧30) spherical particles observed within the unit field of view of the photograph, the longest diameter measured is L i Let B be the minor axis, which is the diameter in the direction perpendicular to the major axis. i When this is the case, the ratio of the two in each particle is (B i / L i The sum of ): Σ(B i / L i )from, Average symmetry = {Σ(B i / L i ) / n} This means that the average uniformity determined by this is 0.6 or higher, preferably 0.8 or higher.

[0053] Furthermore, as will be described later, each G-PID of the one or more G-PIDs contained in the dental curable composition of the present invention m The average primary particle diameter in this material needs to be within the range of 230 to 500 nm, but in existing structural color dental curable compositions, it is considered sufficient if it is within the range of 100 to 1000 nm.

[0054] Furthermore, the difference of 25 nm or more in the average primary particle diameter in condition (1) 1) above is preferably 30 to 100 nm, particularly 40 to 60 nm, and the number of G-PIDs (a) contained in the existing structural color dental curable composition is preferably 1 to 3, particularly 1 or 2, and from the viewpoint of ease of manufacture, it is preferably 1.

[0055] Each G-PID of one or more G-PIDs mIn an aggregate of inorganic spherical particles (granular material) that constitutes the above, in order to exhibit the desired structural color, it is necessary that 90% or more of the total number of particles in the number-based particle size distribution are located within 5% before or after the predetermined average primary particle diameter. Here, the proportion of particles located within 5% before or after the average primary particle diameter in the number-based particle size distribution is calculated by measuring the number of particles with a primary particle diameter (maximum diameter) outside the particle diameter range of ±5% of the average primary particle diameter among the n particles (where n is a natural number of 30 or more) selected when determining the average primary particle diameter, subtracting this value from n to obtain the number of particles within the particle diameter range of ±5% of the average primary particle diameter, and then using the following formula The proportion of particles within 5% of the mean primary particle diameter (%) = (Number of particles within ±5% of the mean primary particle diameter) / n × 100 It was calculated according to the following.

[0056] While powders and granules having such particle size components can be obtained by classification, powders and granules composed of spherical particles made of silica-based inorganic compounds, particularly silica-titanium group element oxide composite oxides, can be suitably produced by the so-called sol-gel method described in, for example, Japanese Patent Publication No. 58-110414, Japanese Patent Publication No. 58-151321, Japanese Patent Publication No. 58-156524, and Japanese Patent Publication No. 58-156526. Such sol-gel methods have the characteristic of producing powders and granules consisting of granular particles with uniform primary particle sizes because the formation and growth of particle nuclei occur uniformly, and the primary particle size can be controlled by reaction conditions such as reaction time. Spherical inorganic particles obtained by such a method are preferably calcined at a temperature of 500 to 1000°C after drying in order to impart surface stability. During firing, some of the primary particles may aggregate. Therefore, it is preferable to use a jet mill, vibrating ball mill, or the like to break down the large aggregated particles into primary particles or smaller aggregated particles, and then adjust the particle size of the remaining aggregated particles to a predetermined range before use. Furthermore, it is preferable to surface treat the spherical inorganic particles with a silane coupling agent or a titanate-based coupling agent. The above surface treatment may be performed on either the primary particles or the aggregated particles. When producing aggregated particles by spray drying, it is efficient to perform the surface treatment simultaneously during this process.

[0057] Each G-PID m Regarding the refractive index n for sodium d lines at 25°C, any G-PID m In this case, the refractive index of the inorganic spherical granules that constitute it: n (G-PIDm) is, n (MX) <n (G-PIDm) The following relationship must hold: Δn=n (G-PIDm) -n (MX) The value of n is preferably 0.002 to 0.1, and particularly preferably 0.005 to 0.05. In order to satisfy these conditions, when selecting the composition of monomer component (A) and the material of G-PID, it is necessary to adopt a combination that satisfies the above relationship. For monomer component (A), the refractive index is set to n because it easily satisfies the relationship. (A) When this is the case, {n (G-PIDm) -n (A) It is preferable that the value of} be 0.03 to 0.20, and particularly 0.05 to 0.10. Furthermore, when using a silica-titanium group element oxide composite oxide, which allows for easy adjustment of the refractive index, as mentioned above, its refractive index will be in the range of approximately 1.45 to 1.58 depending on the silica content, so n (MX) n can be adjusted to a range of approximately 1.40 to 1.57. (A) It is preferable to set the type and amount of polymerizable monomer so that the ratio is in the range of 1.38 to 1.55.

[0058] In existing structural color dental curable compositions, at least one of the G-PIDs constituting one or more G-PIDs may be included in the composition as an organic-inorganic composite powder, in which a portion of the inorganic spherical powder constituting the G-PID is composed of particles made of a composite in which the inorganic spherical powder is dispersed in a resin matrix, and each G-PID m The spherical inorganic particles constituting the structure may form aggregated particles. It is said that adopting such a configuration makes it easier to satisfy the short-range ordered structure defined in (2) above.

[0059] Furthermore, the content of one or more G-PIDs in existing structural color dental curable compositions is 50 to 1500 parts by mass per 100 parts by mass of monomer components.

[0060] 1-3. Photopolymerization initiator (C) The photopolymerization initiator (C) is not particularly limited as long as it has the function of polymerizing the monomer component (A) when exposed to light, and any photopolymerization initiator used in dental curable compositions can be used without particular restriction. Suitable photopolymerization initiators include photosensitizing compounds or combinations of photosensitizing compounds with polymerization accelerators and / or photoacid generators. The amount of photopolymerization initiator is usually 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, per 100 parts by mass of monomer component (A).

[0061] Photosensitizing compounds are compounds that absorb light with wavelengths of 400 nm to 500 nm from a typical dental light curing unit and have the function of generating active species effective for polymerization. These active species are usually generated as a result of energy transfer or electron transfer between the photosensitizing compound, which has been excited by light absorption, and the polymerizable monomer or other compound. Examples of photosensitizing compounds that can be suitably used include 2,3-pentadione benzyl, camphorquinone, 9,10-phenantraquinone, 9,10-anthraquinone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldimethyl ketal, benzophenone, and 4,4'-dimethylbenzophenone. When using a photosensitizing compound, the amount typically blended is 0.01 to 10 parts by mass, preferably 0.03 to 5 parts by mass, and particularly preferably 0.05 to 2 parts by mass, per 100 parts by mass of monomer component (A).

[0062] Tertiary amine compounds function as polymerization accelerators that enhance curability. Examples of suitably usable tertiary amine compounds include ethyl p-(N,N-dimethyl)aminobenzoate, amyl p-(N,N-dimethyl)aminobenzoate, isoamyl 4-(dimethylamino)benzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 4'-dimethylaminoacetophenone, 4-(dimethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, 4-(dimethylamino)benzonitrile, 4-dimethylaminobenzoic acid, and N,N-dimethylamine. Examples of tertiary amine compounds include 4-(trifluoromethyl)aniline, N,N-dimethyl-4-nitroaniline, methyl 2-(dimethylamino)benzoate, methyl 3-(dimethylamino)benzoate, N,N-dimethylaniline, N,N-dibenzylaniline, N,N-dimethyl-p-toluidine, N,N-diethyl-p-toluidine, methyl p-(N,N-dimethyl)aminobenzoate, N-ethyldiethanolamine, triethanolamine, and tri(isopropanol)amine. When using tertiary amine compounds, the amount blended is usually 0.03 to 3.0 parts by mass per 100 parts by mass of monomer component (A), and is particularly preferably 0.1 to 1.5 parts by mass.

[0063] Photoacid generators have the function of generating acid when irradiated with light. The generated acid becomes an active species and promotes polymerization. Examples of photoacid generators that can be suitably used include diphenyliodonium nitrate, diphenyliodonium chloride, diphenyliodonium acetate, bis(p-chlorophenyl)iodonium chloride, ditolylodonium, bis(p-methoxyphenyl)iodonium chloride, bis(p-tert-butylphenyl)iodonium chloride, diphenyliodonium-2-carboxylate monohydrate, 2,4,6-tris(trichloromethyl)-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, and 2-(p-chlorophenyl)-4,6-bis(trichloromethyl)-s-triazine. When using a photoacid generator, the amount to be blended is usually 0.001 to 3.0 parts by mass, preferably 0.05 to 1.5 parts by mass, and particularly preferably 0.07 to 1.0 parts by mass, per 100 parts by mass of monomer component (A).

[0064] 2. Dental curable composition of the present invention The dental curable composition of the present invention is based on the premise that it falls within the category of existing structural color dental curable compositions, and by selecting a system that satisfies specific conditions and further incorporating an X-ray opaque filling material that satisfies specific conditions, it is provided with high X-ray contrast properties and a paste-like consistency suitable for a low-flow type flowable composite resin.

[0065] Specifically, an existing structural color dental curable composition that satisfies the above conditions has the following characteristics (3) to (5).

[0066] (3) The viscosity of the monomer component (A) at 25°C is 100 to 1000 mPa·s.

[0067] (4) All of the one or more G-PIDs consist of inorganic spherical powder (b) whose average is in the range of 230 to 500 nm, composed of inorganic spherical particles whose polarity of the zeta potential measured in water is negative. 1) A part of (b) above (b1) is formulated as (B1), which consists of at least one of the group comprising primary particles (b1-1), a granular material composed of aggregated particles of the primary particles (b1-2), and a composite aggregated granular material (E) composed of aggregated particles of the primary particles and other inorganic particles (e), wherein the granular material (b1-2) and the composite aggregated granular material (E) may be crushed and dispersed in the dental curable composition. 2) The remainder of (b) above (b2) is a specific single G-PID n (However, n is 1 when a is 1, and any natural number from 1 to a when a is 2 or greater.) Inorganic spherical powder (b2 n ) is dispersed in a resin matrix having a refractive index smaller than that of the constituent particles of the powder, (b2 n A composite that does not contain (b2) other than ) and the inorganic spherical powder (b2) relative to the total mass of the composite n It is included as one or more organic-inorganic composite powders (B2) composed of particles made of a composite whose average inorganic content, defined by the total mass of ), is 30 to 95% by mass, 3) The total content of (B1) and the one or more (B2) per 100 parts by mass of (A) is 150 to 300 parts by mass, and the content of the one or more (B2) in relation to the total content is 50 to 70% by mass.

[0068] (5) The (B) further comprises an X-ray opaque filler (D) comprising an aggregated X-ray opaque filler (D1) and a dispersed X-ray opaque filler (D2), 1) Both (D1) and (D2) are composed of crystalline rare earth metal fluoride particles that exhibit a positive zeta potential as measured in water, and the average primary particle size is 1 to 300 nm, and the full width at half maximum of the maximum intensity peak originating from the crystalline rare earth metal fluoride in the X-ray diffraction pattern is 0.3° or more, and the low crystalline rare earth fluoride powder (d) is used as the active ingredient. 2) The (D1) is composed of aggregated particles formed by the aggregation of primary particles constituting the low-crystalline rare-earth fluoride powder (d1) which is the active ingredient, and consists of low-crystalline rare-earth metal fluoride aggregated powder (d1-1) in which the average agglutinator diameter, defined as the median diameter in the volume-based particle size distribution measured by laser diffraction-scattering, is 1 to 30 μm, and the (d1-1) is included as aggregated particles in the dental curable composition. 3) The (D2) consists of primary particles (d2-2) of (d2) contained in a mixed inorganic powder (E1) having an average aggregate particle diameter of 1 to 50 μm, which consists of non-aggregated powder (d2-1) composed of primary particles constituting the low-crystalline rare earth fluoride powder (d2) that constitutes the active ingredient, and / or aggregated particles (e1) of the primary particles constituting (d2) and at least a portion of the constituent particles of (b1-3), wherein the (D2) contains (d2-1), and when the (D2) contains (d2-1), the (d2-1) is contained in the dental curable composition in a dispersed state as primary particles, and when the (D2) contains (d2-2), the (d2-2) is contained in the dental curable composition in a dispersed state as primary particles which are the pulverized product of the aggregated particles (e1). 4) The total content of (d) and the total content of (d2) per 100 mass of (A) are (d): 30 to 75 parts by mass and (d2): 5 to 25 parts by mass.

[0069] These characteristics allow for the development of high radiopaqueness in the cured material while maintaining structural coloration, and enable fluidity, low sagging, and good moldability, allowing the paste to be directly filled into the cavity from the tip of the needle.

[0070] Furthermore, the aggregated particles (e) and composite aggregated powder (E) in (4) 1) above include the aggregated particles (e1) and mixed inorganic powder (E1) in (5) 3) above, respectively. As shown in (5) 3), the aggregated particles (e1) are crushed in the dental curable composition and dispersed as primary particles. However, even when dispersed, (b1-3) and (d2-2) exist in close proximity, so it is thought that a tertiary network structure is formed by electrostatic interaction between the two particles, resulting in good sag and shapeability. Furthermore, (b1-2), (E1), (E) other than (E1), and (d1-1) are all incorporated as granular materials composed of aggregated particles, but their cohesive strength varies. According to the inventors' studies, although it differs depending on the mixing conditions when preparing the dental curable composition, when general mixing conditions are adopted, (d1-1) is hardly broken down if mixed carefully, whereas (b1-2) and (E1) are relatively easily broken down, and it has been confirmed that if (E1) is mixed strongly, most of (d2-2), which constitutes the composite particles, can be uniformly dispersed in the composition as is, similar to (d2-1).

[0071] In the dental curable composition of the present invention, low-crystalline rare-earth metal fluoride particles are present at a high density in (d1-1), which is thought to increase the brightness in X-ray images and improve the X-ray contrastability of the cured body. On the other hand, (d2-1) and / or (d2-2), which are dispersed in the composition as non-aggregated particles, are thought to have reduced sagging and improved moldability due to network formation resulting from electrostatic interaction with (b1-1) and / or (b1-2).

[0072] Furthermore, since it is difficult to identify the exact form in which each of the above components, which are incorporated as granular materials composed of aggregated particles, exist within the dental curable composition through analysis, the identification in (4) 1) above is based on the state in which they are incorporated.

[0073] The features of the dental curable composition of the present invention will be described in detail below.

[0074] 2.1 Selection of the aforementioned characteristic point (3): monomer component (A) The monomer component (A) contained in the dental curable composition of the present invention must consist of one radical polymerizable monomer or a mixture of multiple radical polymerizable monomers, and the monomer component must have a viscosity of 100 to 1000 mPa·s at 25°C. If the viscosity is less than 100 Pa·s, there is a risk that organic-inorganic composite powder particles or agglomerated X-ray opaque fillers will easily settle in the composition, and if it exceeds 1000 mPa·s, there is a risk that it will not have the fluidity suitable for a flowable composite resin that can be directly filled into a cavity from the tip of a needle tip. Furthermore, from the viewpoint of facilitating the discharge of paste from the tip of a needle tip using a kneader, etc., and facilitating the handling of the monomer mixture when kneading the paste, the viscosity is preferably 150 to 500 mPa·s, and particularly preferably 200 to 380 mPa·s.

[0075] The viscosity of monomer component (A) can be confirmed by measuring it using a dynamic viscoelasticity measuring device generally called a rheometer. In this invention, a viscoelasticity measuring device CS rheometer "CVO120HR" (manufactured by Bohlin Corporation), which has a cone / plate geometry of 4 cm / 2° and a temperature control system, was used to evaluate the viscosity at a measurement temperature (plate temperature) of 25°C and a shear rate of 1 rps, and the average value of three measurements was taken as the viscosity.

[0076] As the monomer component (A) included in the dental curable composition of the present invention, a radical polymerizable monomer described as monomer component (A) in an existing structural color dental curable composition may be used, and the composition may be prepared to have such viscosity.

[0077] 2.2 Characteristic point (4): Average primary particle diameter of G-PID constituent particles, zeta potential polarity The dental curable composition of the present invention, like existing structural color dental curable compositions, contains one or more "spherical particle groups of the same particle size": G-PID as an inorganic filler (B). However, all of the one or more G-PIDs used in the dental curable composition of the present invention must consist of inorganic spherical powder (b) having an average primary particle diameter in the range of 230 to 500 nm, composed of inorganic spherical particles whose zeta potential polarity, as measured in water, is negative.

[0078] If the average primary particle diameter falls outside the range of 230 to 500 nm, the yellow to red structural color, which provides high color compatibility with surrounding tooth structure when this composition is used for restoring natural teeth, may not be easily expressed, and the light transmittance at 400 nm to 500 nm (purple to blue), especially at 470 nm, may decrease during curing. The above average primary particle diameter is preferably 240 to 450 nm, and most preferably 250 to 380 nm.

[0079] The zeta potential in water can be measured by electrophoresis, which involves dispersing powder in water, applying an external electric field to induce electrophoresis of the particles, and measuring the migration speed to determine the zeta potential. If inorganic spherical particles exhibiting a negative zeta potential are not used, it becomes difficult to obtain low sagging and good shapeability. A zeta potential of -20mV or less is preferred, and -40mV or less is more preferred. While there is no particular lower limit to the zeta potential, it is generally -100mV or higher.

[0080] Many of the materials exemplified as G-PID constituent particles in existing structural color dental curable compositions have a negative zeta potential polarity in water, and spherical inorganic particles made of silica-based composite oxides, including silica-titanium group element oxide composite oxides which are said to be suitably used, also have a negative zeta potential polarity in water. Therefore, silica-based composite oxides, particularly silica-titanium group element oxide composite oxides, can be suitably used in the dental curable composition of the present invention. Furthermore, the surface may be treated with a silane coupling agent or the like, as long as it does not change the polarity of the zeta potential.

[0081] 2.3 Characteristic points (4) 1) and 2): Form of G-PID As described above, in the dental curable composition of the present invention, a portion (b1) of the inorganic spherical powder (b) must be formulated as (B1), which is at least one of the group consisting of all the primary particles (b1-3) contained in a composite aggregated powder (E) composed of primary particles (b1-1), aggregated particles of the primary particles (b1-2), and aggregated particles (e) of the primary particles and other inorganic particles. In this case, the powder (b1-2) and the composite aggregated powder (E) may be crushed and dispersed in the dental curable composition.

[0082] Here, (b1-1) and (b1-2) can be obtained by the method described in Section 1-2, that is, by calcining the powder or granules obtained by the so-called sol-gel method, then using a jet mill or the like to convert them into primary particles or small aggregated particles, and further adjusting the particle size to a predetermined range or performing surface treatment as needed. Also, (E) can be obtained in accordance with the method for producing the mixed inorganic powder or granules (E1) described later.

[0083] Furthermore, the remainder of (b) above (b2) is a specific single G-PID n (However, n is 1 when a is 1, and any natural number from 1 to a when a is 2 or greater.) Inorganic spherical powder (b2 n ) is dispersed in a resin matrix having a refractive index smaller than that of the constituent particles of the powder, (b2 n A composite that does not contain (b2) other than ) and the inorganic spherical powder (b2) relative to the total mass of the composite n It must be included as one or more organic-inorganic composite powders (B2) consisting of particles made of a composite having an average inorganic content of 30-95% by mass, as defined by the total mass of the organic-inorganic material.

[0084] Here, (B2) can be manufactured by the methods described in Patent Documents 2 and 3. Preferred embodiments of (B2) and their manufacturing methods will be described later.

[0085] Furthermore, the total content of (B1) and one or more of (B2) relative to 100 parts by mass of (A) must be 150 to 300 parts by mass, and the content of one or more of (B2) relative to the total content must be 50 to 70% by mass. If this condition is satisfied, the total content of (b) = total content of (b1) + total content of (b2) will be 76.5 to 292.5 parts by mass.

[0086] If the content of (b1) blended as (B1) above is less than 45 parts by mass per 100 parts by mass of (A), it becomes difficult to obtain low sagging and good formability, and it also leads to a decrease in mechanical strength. If it exceeds 150 parts by mass, it leads to a deterioration in the dispensing feel of the dental curable composition. Conversely, if the content of one or more (B2) is less than 50% by mass {in this case, the lowest content of (b2) per 100 parts by mass of (A) is 22.5 parts by mass}, it not only results in the cured product exhibiting the desired structural color, but also leads to a deterioration in the dispensing feel and a decrease in mechanical strength of the dental curable composition. Furthermore, if the above content exceeds 70% by mass {in this case, the lowest content of (b2) per 100 parts by mass of (A) is 199.5 parts by mass}, it becomes difficult to obtain low sagging and good formability, the specific surface area decreases, the viscosity of the composition decreases, and sedimentation of one or more (B2) becomes more likely.

[0087] For low-flow type flowable CR, the desired fluidity and shapeability are easily obtained, and the desired structural color is easily expressed. Therefore, the total content is preferably 150 to 270 parts by mass, particularly 200 to 250 parts by mass, and the content of (B2) in the total content is preferably 55 to 70% by mass.

[0088] 2.4 Preferred embodiments of organic-inorganic composite powders and granules (B2) The organic-inorganic composite powder (B2) contained in the dental curable composition of the present invention is composed of particles made of a composite in which a part of (b) (b2) is compounded with resin, and in order to maintain the short-range order of the constituent particles of the G-PID, a specific one G-PID is formed. n (However, n is 1 when a is 1, and any natural number from 1 to a when a is 2 or greater.) Inorganic spherical powder (b2 n ) The refractive index of the constituent particles of the granular material is n (b2n) The refractive index smaller than n: (b2mx) Dispersed in a resin matrix having (b2 n The complex must not contain any other (b2) besides n. (b2mx) <n (b2n) If this relationship does not hold, interference will be more likely to occur with short-wavelength light rather than interference light due to particle size according to Bragg diffraction conditions, and the desired structural color may not be easily expressed. In addition, if the dental curable composition of the present invention contains multiple G-PIDs, there may be G-PIDs that are not organically-inorganic composited at all, provided that the above conditions are satisfied. However, it is preferable that the proportion of organically-inorganic composited G-PIDs be the same among all G-PIDs for the reason that the desired structural color is easily expressed.

[0089] Furthermore, in order to avoid impairing the transparency of the cured body of the dental curable composition of the present invention, the difference in refractive index: {n (b2n) -n (b2mx) The value of} is preferably 0.002 to 0.1, particularly 0.005 to 0.05, and the refractive index of the hardened body of (A) is n (mx) The difference from: {n (b2n) -n (mx) The value of} is preferably 0.002 to 0.1, and particularly preferably 0.005 to 0.05. As the resin matrix of (B2), a cured product that satisfies these conditions can be used from among those that can be used as (A).

[0090] Also, (b2 n A composite that does not contain (b2) other than ) and the inorganic spherical powder (b2) relative to the total mass of the composite nThe average inorganic content, defined by the total mass of the organic-inorganic compounds, is 30 to 95% by mass. If the average inorganic content is less than 30% by mass, the expression of structural color may be impaired, and the properties as a structural color-based dental curable composition may not be obtained. If the average inorganic content is higher than 95% by mass, there is a risk that the organic-inorganic composite will disintegrate in the dental curable composition. From the above viewpoint, it is preferable that the average inorganic content be 50 to 90% by mass, and particularly 60 to 85% by mass.

[0091] In (B2), the average particle diameter, defined as the median diameter in the volume-based particle size distribution measured by the laser diffraction-scattering method, is preferably 1 to 100 μm, preferably 5 to 50 μm, and particularly preferably 5 to 30 μm. If the average particle diameter is less than 1 μm, the dispensing performance when dispensing the dental curable composition with a syringe tends to be poor, and if the average particle diameter is greater than 100 μm, the mechanical strength, such as the flexural strength of the cured body of the dental curable composition, tends to decrease.

[0092] Organic-inorganic composite powder (B2) is (b2 n (b2) may be obtained by polymerizing a mixture of a raw material radical polymerizable monomer that serves as the raw material for the resin matrix of (B2) and a polymerization initiator, and then grinding the mixture. Alternatively, (b2 n The aggregated powder, composed of inorganic aggregated particles formed by the aggregation of the above-mentioned radical polymerizable monomer, may be immersed in a polymerizable monomer solution containing the above-mentioned raw material radical polymerizable monomer, polymerization initiator, and organic solvent, then the organic solvent is removed, and the polymerizable monomer is polymerized and cured to obtain a microporous organic-inorganic composite powder. The above-mentioned aggregated powder can be obtained, for example, by spray-drying an aqueous dispersion containing inorganic spherical powder (b). The polymerization initiator can be used without particular limitation as long as it has the function of polymerizing the above-mentioned raw material radical polymerizable monomer.

[0093] 2.5 Characteristic points (5) and (5)1): Low-crystalline rare earth fluoride powder (d) In the dental curable composition of the present invention, in order to impart high radiopaqueness to the cured body, the inorganic filler must include, in addition to one or more G-PIDs, an aggregated radiopaque filler (D1) and a dispersed radiopaque filler (D2). Here, both (D1) and (D2) are composed of crystalline rare earth metal fluoride particles that exhibit a positive zeta potential when measured in water, and the active ingredient is a low-crystalline fluorinated rare earth powder (d) having an average primary particle diameter of 1 to 300 nm and a full width at half maximum of the maximum intensity peak originating from the crystalline rare earth metal fluoride in the X-ray diffraction pattern of 0.3° or more.

[0094] As shown in Patent Document 1, all rare earth metal fluoride particles exhibit a positive zeta potential when measured in water. Therefore, the low-crystalline rare earth fluoride powder (d) corresponds to the X-ray opaque filler disclosed in Patent Document 5. As for the material of the low-crystalline rare earth fluoride powder (d), any crystalline rare earth metal fluoride particles can be used without restriction. However, in terms of color and safety, it is preferable to use crystalline rare earth metal fluorides such as ytterbium fluoride (YbF3), lanthanum fluoride (LaF3), cerium fluoride (CeF3), and gadolinium fluoride (GdF3), and from the viewpoint of X-ray opacity, it is most preferable to use ytterbium fluoride. Whether or not a material is crystalline can be determined by whether or not peaks based on crystal planes are observed when X-ray diffraction measurements are performed.

[0095] The average primary particle size of the low-crystallinity rare-earth fluoride powder (d), as measured by the electron microscope image analysis, is 1 to 300 nm or less, due to reasons such as ease of handling and the low-crystallinity treatment. From the viewpoint of aesthetics (e.g., polishability and transparency), the average primary particle size is preferably 10 to 300 nm, and more preferably 15 to 250 nm. Furthermore, the refractive index of the aggregated X-ray opaque filler (D1) is preferably 1.4 to 1.7 from the viewpoint of transparency of the hardened body of the dental hardening composition, and ytterbium fluoride satisfies this requirement.

[0096] Crystalline particles made of rare earth metal fluorides, particularly ytterbium fluoride, are well known as X-ray contrast-enhanced fillers. However, when incorporated into dental hardening compositions such as composite resins (CR) in a highly crystalline state, it is known that the transparency of the hardened material decreases. Therefore, as described in Patent Document 5, mechanochemical treatment, i.e., a treatment that applies mechanical energy to the raw material powder (specifically, a treatment that involves at least one of mechanical grinding, pulverization, and dispersion), is performed to increase amorphousness and suppress the decrease in transparency. This is done so that the full width at half maximum of the maximum intensity peak originating from the crystalline rare earth metal fluoride in the X-ray diffraction pattern is 0.3° or more. From the viewpoint of suppressing the decrease in transparency, a maximum peak full width at half maximum of 0.4° or more, and particularly 0.5° or more, is preferable. The upper limit of the maximum peak full width at half maximum is not particularly limited, but it does not usually exceed 2.0°.

[0097] Here, the maximum peak full width at half maximum in the aforementioned X-ray diffraction pattern can be determined by performing X-ray diffraction measurements on inorganic particles consisting of crystalline rare-earth metal fluoride particles (after mechanochemical treatment). Specifically, X-ray diffraction measurements are performed using an X-ray diffractometer in the range of 2θ; 20 to 120°, and the peaks originating from the crystalline rare-earth fluoride are identified in the obtained X-ray diffraction pattern (chart) with the horizontal axis as 2θ (°) and the vertical axis as diffraction intensity. The full width at half maximum, i.e., the peak width at which the intensity is 50% of the peak intensity (the absolute value of the difference in 2θ between the two intersection points of the intensity and the peak line: unit "deg[°]"), can be determined by finding the peak with the maximum intensity among them (for example, for YbF3, the peak that appears around 2θ = 28.0° and corresponds to the crystal plane (1,1,1)). Furthermore, when performing the measurement, it is preferable to use a powder sample from which coarse particles have been removed, for example, by using a sieve with a mesh size of 100 μm.

[0098] The mechanochemical treatment is no different from the treatment described in Patent Document 5, and can be suitably carried out by a wet bead mill treatment in which a slurry, which is a mixture of the powder to be treated and a medium, is brought into contact with a media that is moved by stirring or vibration, thereby crushing and / or pulverizing. At this time, it is preferable to use a volatile medium such as water or alcohol that is liquid at room temperature (15-25°C) as the medium. Furthermore, it is preferable to use beads made of alumina or zirconia with a diameter of φ0.01-0.5 mm as the media (beads). The concentration of the slurry subjected to mechanochemical treatment is preferably 50 parts by mass or less of inorganic particles per 100 parts by mass of medium. It is possible to add a dispersant to suppress the increase in viscosity when mechanochemically treating a high-concentration slurry, but it is preferable not to use surfactants that may cause discoloration. The full width at half maximum of the maximum peak varies depending on the treatment conditions such as the slurry concentration. These conditions can be adjusted by conducting preliminary experiments using the actual equipment and conditions for mechanochemical processing, and confirming the maximum peak width at half maximum (FMAX) of the treated crystalline rare earth metal fluoride in relation to the mechanochemical processing time. During manufacturing, by sampling the processed slurry as needed and confirming the maximum peak width at FMAX as appropriate, it is possible to reliably produce low-crystalline rare earth fluoride powder (d) with the desired maximum peak width at FMAX.

[0099] 2.6 Feature point (5) 2): Agglomerated X-ray opaque packing material (D1) The aforementioned agglomerated X-ray opaque filler (D1) is composed of agglomerated particles formed by the aggregation of primary particles constituting the low-crystalline rare-earth fluoride powder (d1), which is part of the low-crystalline rare-earth fluoride powder (d), and consists of low-crystalline rare-earth metal fluoride agglomerated powder (d1-1) having an average agglomerator diameter defined as the median diameter in the volume-based particle size distribution measured by laser diffraction-scattering method of 1 to 30 μm. In this context, the low-crystalline rare-earth metal fluoride agglomerated powder (d1-1) means that it maintains its state and is dispersed as agglomerated powder having the above average agglomerator diameter in the dental curable composition of the present invention.

[0100] If the average particle diameter is less than 1 μm, it may adversely affect the development of structural color, and if it exceeds 30 μm, the mechanical strength of the cured body of the dental curable composition may decrease. From the viewpoint of mechanical strength and ease of manufacture, the average agglutinator diameter is preferably 2 to 25 μm, and more preferably 3 to 20 μm. Note that the low-crystalline rare-earth metal fluoride agglutinated powder (d1-1) which becomes (D1) is an agglutinated particle consisting of inorganic particles having a fine average primary particle diameter, so even if the average particle diameter is 1 μm or more, the polishability of the resulting cured body will not decrease, and it will not become difficult to obtain a cured body with a smooth surface.

[0101] (d1-1) having such an average agglomerate diameter can be suitably obtained by spray-drying the treated slurry obtained by mechanochemical treatment. Spray drying can be carried out by spraying the mixture in fine droplets using a high-speed airflow and drying it, or by dropping the mixture onto a disc-shaped rotating body rotating at a rotational speed of 1,000 to 50,000 rpm and blowing it off in a mist by centrifugal force and drying it. However, it is difficult to obtain powder or granular material with an average agglomerate diameter of 3 μm or less using such methods.

[0102] The aggregated particles obtained by the above spray drying method may have a small amount of dispersion medium remaining. For this reason, it is preferable to perform vacuum drying after spray drying. Vacuum drying is generally performed under reduced pressure of 0.01 to 100 hectopascals at 20 to 150°C for 1 to 48 hours. Furthermore, by heating under reduced pressure using a vacuum dryer or the like, it is possible to remove the dispersion medium remaining after spray drying and to increase the cohesive force of the rare earth metal fluoride particles.

[0103] The average aggregated particle size of the resulting granular powder usually varies depending on the size of the droplets during spray drying, but it can be controlled to a predetermined average aggregated particle size by adjusting the slurry concentration. Note that (d1-1) may be surface-treated with a silane coupling agent, titanate coupling agent, etc.

[0104] The state of existence of the low-crystalline rare-earth metal fluoride aggregate powder (d1-1), which is (D1), in the dental curable composition can be confirmed by scanning electron microscopy observation. For example, when a hardened body obtained by irradiating the dental curable composition with light is observed as a backscattered electron image at 1,000x magnification using a scanning electron microscope, it can be confirmed as particles with a particle size of 1 μm or larger and high brightness.

[0105] 2.6 Feature points (5) 3) and 4): Dispersive X-ray radiopaque filler (D2) The dispersed X-ray opaque filler (D2) consists of primary particles (d2-2) of (d2) contained in a mixed inorganic powder (E1) having an average aggregate particle diameter of 1 to 50 μm, which is composed of non-aggregated powder (d2-1) composed of primary particles constituting the low-crystalline rare-earth fluoride powder (d2) that constitutes the active ingredient (d2), and / or aggregated particles (e1) of the primary particles constituting (d2) and at least a portion of the constituent particles of (b1-3). Here, (d2-2) is blended as a mixed inorganic powder (E1), but the aggregated particles (e1) constituting it are crushed in the kneading process for preparing the dental curable composition of the present invention, and basically exist dispersed in the dental curable composition of the present invention as crushed aggregated particles (e1) in the state of primary particles. Thus, (d2), which becomes the dispersed X-ray opaque filler (D2), is basically dispersed as primary particles in the dental curable composition of the present invention. However, when the aggregated particles (e1) are crushed, they may not be crushed down to the primary particles and may exist as a very small number of (d2-2) primary particles or as cluster particles consisting of (d2-2) primary particles and (b1-3) primary particles. Therefore, (d2-1) and (d2-2) are distinguished depending on the formulation. The non-aggregated granular material (d2-1) only needs to be dispersed as primary particles in the dental curable composition of the present invention, and may be formulated as aggregated granular material if it is dispersed as primary particles by kneading during the preparation of the dental curable composition of the present invention.

[0106] When formulated as (E1), electrostatic interactions between (d2-2) primary particles and (b1-3) primary particles are more likely to occur during the crushing process in kneading, resulting in the formation of a three-dimensional network in the dental curable composition of the present invention, making it easier to obtain low sagging and good moldability. For this reason, it is preferable that the dispersed radiopaque filler (D2) be a mixed inorganic powder (E1).

[0107] The state of existence of (d2-1) and / or (d2-2) in the dental hardening composition can be confirmed by scanning electron microscopy observation or the like, as in (d1-1).

[0108] 2.7 Method for producing mixed inorganic powders and granules (E1) The mixed inorganic powder (E1) can be suitably produced by spray-drying a mixed slurry prepared by mixing a slurry (Sb) in which constituent particles of inorganic spherical powder (b1-3) at a rate of 100 parts by mass are uniformly dispersed in a dispersion medium, and a slurry (Sd2) in which primary particles of low-crystalline rare earth fluoride powder (d2-2) are uniformly dispersed in a dispersion medium.

[0109] Slurry (Sb) can be obtained by dispersing a mixture of a dispersion medium and inorganic spherical powders (b1-3). The dispersion process can be carried out using a dispersion medium consisting of water or a mixture of water and a volatile organic solvent, similar to the mechanochemical process for preparing (d) described above, and using a mixing device such as a bead mill. Slurry (Sd2) can also be prepared in the same manner as the mechanochemical process described above, and the slurry obtained by the mechanochemical process for preparing (d) can be used as is.

[0110] The two slurries can be mixed using a stirrer or the like. When mixing, it is preferable that the amount of low-crystalline rare earth fluoride granules (d2-2) in the mixed slurry be 20 to 300 parts by mass, more preferably 22 to 280 parts by mass, and particularly 25 to 250 parts by mass, for every 100 parts by mass of inorganic spherical granules (b1-3).

[0111] During mixing, the viscosity increases due to electrostatic interactions between the constituent particles of the two types of powders and granules. However, if slurry (Sb) and slurry (Sd2) adjusted to the aforementioned dispersion concentrations are used, and the ratio of (b1-3) to (d2-2) is within the above range, a uniform slurry can be prepared without adding a dispersant. While the use of dispersants is not excluded, ionic surfactants can inhibit the hardening of dental curable compositions and cause discoloration and reduced strength of the cured product, so it is preferable not to use them.

[0112] Furthermore, the mixed slurry may contain a surface treatment agent, such as a silane coupling agent or a titanate-based coupling agent, as needed. By using a surface treatment agent, (b1-3) and / or (d2-2) can be surface treated. The amount of surface treatment agent is usually 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass, per 100 parts by mass of the total of both powders.

[0113] Mixed inorganic powder (E1) can be obtained by spray drying the mixed slurry. Spray drying can be carried out in the same manner as spray drying during preparation (d1-1). The powder obtained by spray drying may be crushed as needed to adjust the particle size so that the average aggregated particle diameter is within the range of 1 to 50 μm. If the average aggregated particle diameter is outside this range, not only is preparation difficult, but handling becomes difficult. From the viewpoint of ease of preparation, it is preferable that the average aggregated particle diameter of (E1) is 3 to 50 μm.

[0114] 2.8 The proportions of characteristic point (5)(d) and (d2) In the dental curable composition of the present invention, the total content of (d) and the total content of (d2) per 100 mass of (A) must be (d): 30 to 75 parts by mass and (d2): 5 to 25 parts by mass. If the total content of (d) is less than 30 parts by mass, high radiopaqueness may not be obtained, and if it exceeds 75 parts by mass, the mechanical strength of the dental curable composition may decrease. From the viewpoint of easily achieving both high radiopaqueness and mechanical strength, the above content is preferably 30 to 60 parts by mass, and particularly preferably 35 to 55 parts by mass. Furthermore, if the above content of (d2) is less than 5 parts by mass, it is difficult to obtain low sagging and good formability, and if it exceeds 25 parts by mass, it may be difficult to produce the desired structural color. The above content of (d2) is preferably 10 to 25 parts by mass, and particularly preferably 15 to 25 parts by mass.

[0115] 2.9 Other additives, etc. The dental curable composition of the present invention may contain other additives such as polymerization inhibitors, ultraviolet absorbers, fluorescent agents, antioxidants, and antibacterial agents, to the extent that they do not impair its effect. Examples of polymerization inhibitors include hydroquinone, hydroquinone monomethyl ether, and dibutylhydroxytoluene. As described above, the cured product of the structural color dental curable composition of the present invention exhibits structural color even without the use of coloring substances such as pigments. Therefore, it is not necessary to include pigments that may change color over time in the curable composition according to this embodiment. However, this does not negate the use of pigments altogether, and pigments may be included in amounts that do not interfere with the coloring light caused by the interference of spherical fillers. Specifically, pigments may be included in amounts of about 0.0005 to 0.5 parts by mass, preferably about 0.001 to 0.3 parts by mass, per 100 parts by mass of polymerizable monomer.

[0116] Furthermore, the dental curing composition of the present invention may contain inorganic powders consisting of inorganic particles other than the G-PID and the constituent particles of (D), to the extent that they do not impair its effect.

[0117] 3. Manufacturing method of the present invention The composition of the dental curable composition of the present invention is determined by controlling the amount of each component based on the amount of monomer component (A) used. For example, the content of low-crystalline rare earth fluoride powder (d) can, in principle, be controlled by the amount of low-crystalline rare earth metal fluoride aggregate powder (d1-1), non-aggregated powder (d2-1), and / or mixed inorganic powder (E1) used, and the content of (d2-2) in (E1) when (E1) is used.

[0118] Therefore, the dental curable composition of the present invention, The process includes a kneading step of kneading the monomer component (A); the powder (b1-1) and / or the powder (b1-2); the one or more organic-inorganic composite powder (B2); the non-aggregated powder (d2-1) and / or the mixed inorganic powder (E1); the low-crystallinity rare-earth metal fluoride aggregated powder (d1-1); and the photopolymerization initiator (C), In the kneading step, the amounts of each component (B2), (d1-1), and the photopolymerization initiator (C) relative to 100 parts by mass of (A) are set to (B2): 75 to 210 parts by mass, (d1-1): 5 to 70 parts by mass, and (C): 0.01 to 10 parts by mass, respectively. The amount of (b1-1) and / or (b1-2), and (d2-1) and / or (E1) relative to 100 mass of (A) is If (E1) is not included, the total amount of (b1-1) and (b1-2) shall be 45 to 150 parts by mass, and (d2-1) shall be 5 to 25 parts by mass. When incorporating (E1) as described above, the total amount of (b1-3) contained in (b1-1), (b1-2), and (E1) shall be 45 to 150 parts by mass, and the total amount of (d2-2) contained in (d2-1) and (E1) shall be 5 to 25 parts by mass. The present invention, characterized by the above, can be suitably manufactured.

[0119] Here, in the kneading process, (d2-2) needs to be dispersed in a primary particle state as a defatted product of the aggregated particles (e1). When (E1) is not used, this is not a problem, and the content of (d2) can be controlled by the amount of (d2-1) used. However, when (E1) is used, depending on the kneading conditions, (d2-2) in (E1) may not be sufficiently dispersed and may not function as a dispersed X-ray opaque packing material (D2).

[0120] Therefore, when using (E1), it is preferable to blend the components that become (D) as follows in order to ensure that (d2-2) in (E1) functions as (D2). Specifically, it is preferable to blend 100 parts by mass of monomer component (A) with non-aggregated particles (d2-1) and (d2-2) in (E1) in such a way that the total amount is a predetermined amount of (d2), and then perform a first kneading step using a kneader or the like to make a paste, and after confirming that (d2-1) and (d2-2) are uniformly dispersed as primary particles, further blend a predetermined amount of low-crystalline rare earth metal fluoride aggregated powder (d1-1) and perform a second kneading step in such a way that the aggregated particles do not break down.

[0121] Furthermore, the uniform dispersion of (d2-1) and (d2-2) as primary particles can be confirmed by FE-SEM image observation. Low-crystallinity rare-earth fluoride particles are usually not spherical, and their contrast in the observation field differs from that of silica-based composite oxides, so the dispersion state of (d2-1) and (d2-2) can be confirmed even if (b1-1) and (b1-2) are present.

[0122] Furthermore, in the first kneading step, in order to ensure that (d2-2) is reliably dispersed uniformly in the composition as primary particles, it is preferable to perform the mixing (kneading) under conditions where the paste hardness, measured using a rheometer, is 3 kg or more, and then confirm the dispersion state with an electron microscope before ending the mixing, or to adopt mixing conditions that have been confirmed in advance to obtain the desired dispersion state by checking the dispersion conditions with an electron microscope over time. Here, paste hardness refers to the maximum load when the paste is filled into a sample stage having a hole with a diameter of 5 mm and a depth of 3 mm, shielded from light, left to stand at 23°C for 2 minutes, and then compressed into the hole filled with paste using a rheometer (Sun Science Co., Ltd.) at a load speed of 240 mm / min to a load depth of 2 mm. When this paste hardness is 3 kg or more, shear is easily applied to the paste, and the constituent particles of the inorganic spherical powder (b) and (d2) are easily dispersed uniformly in the composition as primary particles. The paste consistency is determined by the ratio of polymerizable monomer solution to each powder, so after mixing the polymerizable monomer solution and each powder in the appropriate ratio, the remaining polymerizable monomer solution should be added.

[0123] Furthermore, in the second kneading step for mixing the agglomerated X-ray opaque filler (D1), it is preferable to knead (mix) under conditions where the viscosity measured using a CS rheometer is 150 Pa·s or less, for example, and then confirm the dispersion state with an electron microscope before ending the mixing, or to adopt mixing conditions that have been confirmed to yield the desired dispersion state by checking the dispersion conditions over time with an electron microscope. The above viscosity refers to the maximum viscosity measured using a CS rheometer (Anton Pahl, MCR302) with a parallel plate, at a measurement temperature of 25°C and a shear rate of 5 / s. When this viscosity is 150 Pa·s or less, the paste is less likely to be sheared, and the agglomerated particles are more likely to be uniformly dispersed in the composition without being destroyed. Since the viscosity is determined by the ratio of polymerizable monomer solution to each powder, an appropriate amount of polymerizable monomer solution should be added before adding the agglomerated X-ray opaque filler (D1).

[0124] The paste hardness during the first mixing step varies depending on the desired dental curable composition, but normally, if the above conditions are satisfied, (d2-2) will be uniformly dispersed as primary particles. Similarly, the viscosity during the second mixing step varies depending on the desired dental curable composition, but normally, if the above conditions are satisfied, the aggregated particles will not break down. In either case, to ensure certainty, it is preferable to confirm the dispersion state by observing FE-SEM images.

[0125] 4. Dental composite resin of the present invention The dental composite resin of the present invention comprises the dental curable composition of the present invention and is characterized in that, for a cured sample with a thickness of 1 mm, the contrast ratio T, defined as the ratio of Yb (Yb) measured under a black background and Yw (Yw) measured under a white background using a colorimeter, is 0.20 to 0.50.

[0126] If the contrast ratio of the 1mm hardened material is less than 0.20, the hardened material may become too transparent, making it unsuitable for aesthetic restoration as a structurally colored dental hardened composition. If the contrast ratio of the 1mm hardened material exceeds 0.50, the hardened material may become too opaque, making it unsuitable for aesthetic restoration as a structurally colored dental hardened composition. From the viewpoint of color compatibility, a contrast ratio of 0.20 to 0.45 is more preferable.

[0127] The dental composite resin of the present invention has suitable formability as a low-flow type flowable CR. For example, it is preferable that the "flow value," defined as the spread diameter (mm) of the paste when 0.1 g of the dental hardening composition is dispensed onto a glass plate and left to stand horizontally in a 37°C incubator for 2 minutes, is 3.0 to 8.0 mm, and the "sag value," defined as the distance (mm) the paste moves when 0.03 g of the dental hardening composition is dispensed onto a glass plate and left to stand vertically in a 37°C incubator for 1 minute, is 2.0 mm or less. If the flow value is less than 3.0 mm, the fluidity of the paste is low and there is a risk that the paste cannot be pushed out from the tip of the needle tip with suitable force. If it exceeds 8.00 mm, there is a risk that the paste will flow and it will not be possible to form an occlusal morphology. If the sag value exceeds 2.0 mm, there is also a risk that the paste will flow and it will not be possible to form an occlusal morphology.

[0128] Furthermore, the dental composite resin of the present invention preferably provides a hardened material in which the radiopaqueness (%Al) of the hardened sample, calculated from the brightness when a 1 mm thick hardened sample and an aluminum step wedge are observed using a tabletop X-ray radiography device, is 200 to 300 (%Al). If the radiopaqueness (%Al) of the 1 mm thick hardened sample is less than 200 (%Al), there is a risk that it will be indistinguishable from human tooth enamel when an X-ray image is obtained, and if it exceeds 300 (%Al), there is a risk that the amount of radiopaque filling material added will need to be increased, which may reduce the mechanical strength.

[0129] Furthermore, the dental composite resin of the present invention preferably has fluidity that allows it to be extruded with good force from the tip of a needle. For example, it is preferable that the "concentration value," defined by the spread radius (mm) of the paste after 10 seconds when 0.2g of the dental curable composition extruded onto a polypropylene film is crushed with a load of 50g at 25°C, is between 10.0 and 25.0 (mm). Note that consistency is an index representing the hardness (softness) of the flowable CR paste. If the "concentration value" is less than 10.0, the paste may be too hard and may not be extruded with good force from the tip of the needle. If the "concentration value" exceeds 25.0, the paste may be too fluid and lack shape-forming properties. [Examples]

[0130] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0131] I. Raw materials, main components, and their preparation The raw materials used in the examples and comparative examples, their respective main components, preparation methods, and physical properties are described below.

[0132] 1. Monomer component (A) Table 1 shows the radical polymerizable monomers and radical polymerizable monomer mixtures (monomer components) used in the examples and comparative examples, labeled A-1 to A-6. The abbreviations in the polymerizable monomer column of the table represent the following compounds, and the numbers in parentheses after the abbreviations represent the parts by mass used. UDMA: 1,6-bis(methacrylateethyloxycarbonylamino)trimethylhexane • 3G: Triethylene glycol dimethacrylate · D-2.6E: 2,2-Bis[(4-methacryloyloxypolyethoxy)phenyl]propane ND: Non-methylenediol dimethacrylate • Bis-GMA: 2,2-Bis[(3-methacryloyloxy-2-hydroxypropyloxy)phenyl]propane Furthermore, the viscosity and refractive index of the polymerizable monomers and A-1 to A-6 were evaluated by the following method.

[0133] <Viscosity Evaluation> Viscosity was measured using a CS rheometer under the following conditions: A viscoelasticity measuring instrument, the CS rheometer "CVO120HR" (manufactured by Bohlin), equipped with a cone / plate geometry of 4 cm / 2° and a temperature control system, was used to evaluate viscosity at a measurement temperature (plate temperature) of 25°C and a shear rate of 1 rps. The average value of three measurements was calculated to determine the viscosity of the polymerizable monomer.

[0134] <Evaluation of refractive index of monomer components> The refractive index n of the monomer components A-1 to A-6 used with respect to the sodium d line at 25°C. (A) The measurements were taken using an Abbe refractometer (manufactured by Atago) in a constant temperature room at 25°C.

[0135] <Refractive index n of the monomer component polymer (cured product) (MX) Evaluation > The refractive index n of the polymers of monomer components A-1 to A-6 used was measured in a constant temperature room at 25°C using an Abbe refractometer (manufactured by Atago) for polymers polymerized under conditions almost identical to those used in the cavity. Specifically, a homogeneous polymerizable monomer (or mixture of polymerizable monomers) was prepared by mixing camphorquinone (CQ): 0.2% by mass, pN,N-dimethylaminobenzoate ethyl (DMBE): 0.3% by mass, diphenyliodonium 2-carboxylate monohydrate (DPIC): 0.4% by mass, and hydroquinone monomethyl ether (HQME): 0.15% by mass. This mixture was placed in a mold with through-holes measuring φ7 mm × depth 0.5 mm, and polypropylene films were pressed onto both sides. Subsequently, light intensity of 800 mW / cm² was applied. 2The sample was cured by irradiating it with light for 30 seconds using a halogen-type dental light curing unit (Demetron LC, manufactured by Cybron), and then removed from the mold to prepare a polymerizable monomer. When setting the polymer in an Abbe refractometer (manufactured by Atago), a solvent (1-bromonaphthalene) with a higher refractive index than the sample was dropped onto the sample without dissolving it, in order to ensure close contact between the polymer and the measurement surface, and then measured.

[0136] [Table 1]

[0137] 2. Group of spherical particles with the same particle size (G-PID), etc. 2-1. [Production of inorganic spherical powders (b) and powders (b1-2)] The inorganic spherical powders (b): FB-1 to FB-4 constituting the group of spherical particles of the same particle size (G-PID) were prepared by the so-called sol-gel method described in Japanese Patent Publication No. 58-110414, Japanese Patent Publication No. 58-156524, etc., by adding a mixed solution containing a hydrolyzable organosilicon compound (tetraethyl silicate) and a hydrolyzable organotitanium group metal compound (tetrabutyl zirconate or tetrabutyl titanate), etc., to an ammoniacal alcohol solution into which ammonia water was introduced, performing hydrolysis to precipitate the reaction product, and then drying, grinding, and calcining.

[0138] The inorganic amorphous powder granules FB-5, which consist of crushed inorganic particles (inorganic particles with inconsistent shapes obtained by crushing or pulverizing) that do not fall under the (G-PID) used as a reference, were prepared by following the methods described in Japanese Patent Publication No. 2-132102, Japanese Patent Publication No. 3-197311, etc., dissolving an alkoxysilane compound in an organic solvent, adding water to partially hydrolyze it, then adding other metal alkoxides and alkali metal compounds to be compounded and hydrolyzing them to produce a gel-like substance, and then drying the gel-like substance, pulverizing it as needed, and calcining it.

[0139] Table 2 shows the analytical results for the inorganic granules (inorganic spherical granules and inorganic amorphous granules) FB-1 to FB-5 used in the examples. The refractive index n for the sodium d line at 25°C was measured by the immersion method using an Abbe refractometer (manufactured by Atago). Specifically, the inorganic granules were dispersed in 50 mL of anhydrous toluene in a 100 mL sample bottle in a constant temperature room at 25°C. While stirring this dispersion with a stirrer, 1-bromotoluene was added dropwise little by little, and the refractive index of the dispersion was measured when the dispersion became the clearest, and the obtained value was taken as the refractive index of the inorganic granules. In addition, the average primary particle diameter, the percentage of particles within ±5% of the average primary particle diameter, and the zeta potential of FB-1 to FB-5 were evaluated by the following method.

[0140] <Method for measuring the average primary particle diameter> A scanning electron microscope (Philips XL-30S) was used to take photographs of the powder at magnifications of 5,000 to 100,000 times. The captured images were processed using image analysis software (IP-1000PC, product name; manufactured by Asahi Kasei Engineering Co., Ltd.), and the average primary particle diameter was determined based on the number of particles (100 or more) observed within the unit field of view of the photograph.

[0141] <Percentage of particles that fall within ±5% of the average primary particle diameter> The number of particles within ±5% of the average primary particle diameter was determined by subtracting the number of particles with a primary particle diameter (maximum diameter) outside the ±5% particle diameter range of the average primary particle diameter from the number of particles evaluated during the measurement of the average primary particle diameter. The proportion of particles within ±5% of the average primary particle diameter was then calculated according to the following formula.

[0142] The proportion of particles within 5% of the mean primary particle diameter (%) = (Number of particles within ±5% of the mean primary particle diameter) / n × 100 <Method for measuring the zeta potential of inorganic powders and granules> Inorganic powders were suspended in deionized water with a pH of 7, and the material was dispersed in the water by irradiating it with ultrasound for 30 minutes until the suspension concentration was 1.0% by mass. The zeta potential of this suspension was measured using a zeta potential measuring device (ELSZ-2000, manufactured by Otsuka Electronics Co., Ltd.). Three measurements were performed on each sample, and the average was taken as the zeta potential.

[0143] [Table 2]

[0144] 2-2. [Manufacturing of Organic-Inorganic Composite Powders (B2)] 100 g of the inorganic spherical powder (FB-1) shown in Table 2 was added to 150 g of water, and a water-dispersed slurry (Sb-1) was obtained using a circulating pulverizer SC Mill (manufactured by Nippon Coke Industries Co., Ltd.). Meanwhile, 4 g (0.016 mol) of γ-methacryloyloxypropyltrimethoxysilane and 0.003 g of acetic acid were added to 80 g of water, stirred for 1 hour and 30 minutes, and a homogeneous solution with pH 4 was obtained. This solution and 50 g of water were added to the dispersion slurry of the inorganic spherical powder and mixed until homogeneous. Then, the dispersion slurry was lightly mixed and supplied onto a rapidly rotating disk, and granulation was performed by spray drying. Spray drying was performed using a spray dryer TSR-2W (manufactured by Sakamoto Giken Co., Ltd.) equipped with a rotating disc that atomizes the powder using centrifugal force. The disc rotation speed was 10,000 rpm, and the temperature of the drying atmosphere air was 200°C. Subsequently, the powder obtained by granulation through spray drying was vacuum-dried at 60°C for 18 hours to obtain 73 g of granular material (aggregated granular material) composed of roughly spherical aggregated particles.

[0145] Next, 30 g of the above-mentioned agglomerated powder was immersed in a polymerizable monomer solution prepared by mixing 4.1 g of UDMA as a polymerizable monomer, 0.015 g of azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and 12.4 g of ethanol as an organic solvent. After thorough stirring and confirmation that the mixture had become a slurry, it was left to stand for 1 hour. The above mixture was dried in a vacuum dryer under reduced pressure of 10 hectopascals and heating conditions of 40°C for 1 hour to remove the organic solvent. After removal of the organic solvent, a non-aggregating, highly fluid powder was obtained. The above powder was heated for 20 minutes under reduced pressure of 10 hectopascals and 140°C to polymerize and harden the polymerizable monomers in the powder. Next, it was sieved through a mesh size of 100 μm to obtain 26 g of organic-inorganic composite powder (B2):CF-1, which consists of approximately spherical organic-inorganic composite particles, the surface of which of the resulting spherical aggregates is coated with an organic polymer.

[0146] Organic-inorganic composite powder CF-2 was obtained in the same manner as CF-1, except that the amount of polymerizable monomer UDMA used was changed to 22.6 g. Organic-inorganic composite powder CF-3 was obtained in the same manner as CF-1, except that the amount of polymerizable monomer UDMA used was changed to 7 g. Organic-inorganic composite powder CF-4 was obtained in the same manner as CF-1, except that the amount of polymerizable monomer UDMA used was changed to 0.6 g.

[0147] The average particle size (median diameter in the volume-based particle size distribution) was determined for the obtained organic-inorganic composite powder (B2) as follows. The results are shown in Table 3.

[0148] <Evaluation of average particle size of organic-inorganic composite powder (B2)> 0.1 g of organic-inorganic composite powder (B2) was dispersed in 10 mL of ethanol and irradiated with ultrasound for 20 minutes. Using a laser diffraction-scattering particle size analyzer "LS230" (Beckman Coulter), the optical model "Fraunhofer" was applied, and the average particle size was determined from the median diameter of the volume statistics.

[0149] [Table 3]

[0150] 3. Polymerization initiators {photopolymerization initiator (C) and tertiary amine compound (F), etc.} The abbreviations for the compounds used as polymerization initiators (C) are shown below. Photopolymerization initiator (photosensitizer) • CQ: Camphorquinone Photoacid generator DPIC: Diphenyliodonium 2-carboxylate monohydrate Polymerization accelerator: Tertiary amine compound (F): • DMBE: pN,N-dimethylaminobenzoate ethyl • DMA: 4'-dimethylaminoacetophenone DMBA: 4-dimethylaminobenzoic acid DMBN: 4-(dimethylamino)benzonitrile DMTFA: N,N-dimethyl-4-(trifluoromethyl)aniline ·2-DMBM: Methyl 2-(dimethylamino)benzoate • 3-DMBM: Methyl 3-(dimethylamino)benzoate DMBH: 2-ethylhexyl 4-dimethylaminobenzoate Polymerization inhibitors • HQME: Hydroquinone monomethyl ether 4.Radio-opaque filling material (D) 4-1. [Crystalline rare earth metal fluoride powder / granules] The following crystalline rare earth metal fluoride powders were used as raw materials for the low-crystalline rare earth fluoride powders (d). • Inorganic powder composed of YbF3-40:3 ytterbium fluoride (average primary particle size 46 nm, manufactured by Treibacer). • YbF3-300:3 Inorganic powder composed of ytterbium fluoride (average primary particle size 270 nm, manufactured by Treibacer). • Inorganic powder composed of YbF3-800:3 ytterbium fluoride (average primary particle size 735 nm, manufactured by Sukgyung).

[0151] 4-2. [Production of low-crystalline rare earth fluoride powder (d)] By subjecting each of the aforementioned crystalline rare earth metal fluoride particles to mechanochemical treatment, slurries (Sd-1 to Sd-5) containing dispersed crystalline rare earth metal fluoride particles (d), which serve as raw materials for low-crystalline rare earth metal fluoride aggregates (d1-1) and mixed inorganic powders (E1), were obtained. Mechanochemical treatment was performed using a wet bead mill SC50 (manufactured by Mitsui Mining Co., Ltd.) by mixing an inorganic powder mixture consisting of 400 parts by mass of each crystalline rare earth fluoride with 600 parts by mass of ion-exchanged water, and dispersing the slurry using 100 g of φ0.3 mm zirconia beads at a rotation speed of 3000 rpm for the treatment time shown in Table 4. Furthermore, the obtained slurry was dried under reduced pressure using an evaporator to prepare low-crystallinity fluoride rare earth powders (d): Fd-1 to Fd-5 for physical property confirmation. For these obtained (d) samples, the average primary particle size and zeta potential were measured in the same manner as in 2-1 above, and the 2θ, full width at half maximum (deg:°), and specific surface area of ​​the peak of the crystal plane (1,1,1) in the X-ray diffraction pattern were measured as follows.

[0152] <Method for measuring 2θ and full width at half maximum (deg:°) of crystal plane (1,1,1)> The aforementioned granular material was packed into a sample stage, and an X-ray diffraction pattern (chart) was obtained by measuring it using an X-ray diffractometer {Rigaku Corporation's "Smartlab"}, with the horizontal axis representing 2θ (°) and the vertical axis representing diffraction intensity. Here, CuKα rays were used as the X-rays for the X-ray diffraction measurement. When the material of the crystalline rare earth metal fluoride particles is YbF3, the peak with the greatest intensity is the peak originating from the (1,1,1) plane (a peak observed around 2θ = 28°), so the full width at half maximum (deg:°) of this peak was determined.

[0153] <Method for measuring specific surface area> 0.1 g of the crystalline rare earth metal fluoride particles (Fd-1 to Fd-5) were placed in a sample cell, and pretreatment was performed at 100°C for 3 hours under vacuum using a pretreatment device (BELPREP-miniII, manufactured by Microtrac-Bell Co., Ltd.). Subsequently, nitrogen adsorption isotherms were determined using a gas adsorption pore distribution analyzer (BELSORP-miniII, manufactured by Microtrac-Bell Co., Ltd.) with nitrogen as the adsorption gas and liquid nitrogen as the refrigerant, and the specific surface area was calculated by the BET method.

[0154] [Table 4]

[0155] 4-3. [Low-crystallinity rare-earth metal fluoride aggregate powder (d1-1) and its production] By spray-drying the slurry in which the low-crystallinity rare earth fluoride powder (d) was dispersed, low-crystallinity rare earth metal fluoride agglomerated powder (d1-1) FD1-1 to FD1-5, which serve as agglomerated X-ray opaque packing material (D1), and reference low-crystallinity rare earth fluoride powder (FD1-6 to FD1-7) were prepared. Specifically, the slurry: Sd-1 was dried using a nozzle-type spray dryer (Mini Spray Dryer B-290 Advanced; manufactured by Nippon Büch Co., Ltd.), and inorganic aggregated particles were obtained from the cyclone recovery section. The obtained inorganic aggregated particles were spread on a tray and vacuum-dried at 80°C for 15 hours to obtain a powder which was designated as a low-crystalline rare-earth metal fluoride aggregated powder (d1-1): FD1-1, which would serve as an agglomerated X-ray opaque packing material (D1). FD1-2 was prepared in the same manner as FD1-1, except that the mass percentage concentration of the slurry during spray drying with a spray dryer was set to 5%. Furthermore, inorganic aggregated particles obtained from the recovery section at the bottom of the main unit under the same conditions as FD1-1 were designated as FD1-3. Additionally, FD1-4 to FD1-5 were prepared in the same manner as FD1-1, except that the slurry used was changed to Sd-2 to Sd-3. Reference low-crystalline rare earth fluoride powder granules: FD1-6 were prepared in the same manner as FD1-1, except that the slurry used was changed to Sd-4. Finally, FD1-3 was sieved through a 25 μm mesh sieve, and the powder remaining on the sieve was designated as reference low-crystalline rare earth fluoride powder granules: FD1-7. For each of the (d1-1) samples obtained in this manner, the average particle size (median diameter in the volume-based particle size distribution) was determined as follows. The results, along with those for "Other X-ray opaque fillers: CFD-1" described later, are shown in Table 5.

[0156] <Evaluation of average particle size> 0.1 g of aggregated X-ray opaque packing material (D1) was dispersed in 10 mL of deionized water and shaken by hand. Using a laser diffraction-scattering particle size analyzer "LS230" (Beckman Coulter), the optical model "Fraunhofer" was applied, and the average particle size was determined from the median diameter of the volume statistics.

[0157] [Table 5]

[0158] 4-4. [Production of mixed inorganic powders and granules (E)] Using a slurry containing dispersed spherical inorganic powders (b1-3) and a slurry containing low-crystalline rare-earth metal fluoride aggregates (d2-2) as raw materials, FE-1 to FE-6, which become dispersed X-ray opaque packing materials (D2), and reference mixed inorganic powders (FE-7 to FE-9) were prepared as follows.

[0159] Specifically, 100 g of slurry Sb-1, in which spherical inorganic granules (b1-3) were dispersed, and 25 g of slurry Sd-1, in which low-crystalline rare-earth metal fluoride aggregate granules (d2-2) were dispersed, were mixed to obtain a mixed slurry. Next, 1.6 g (0.006 mol) of γ-methacryloyloxypropyltrimethoxysilane and 20 g of water were added, and then acetic acid was added to adjust the pH to 4. The mixture was stirred for 1 hour and 30 minutes to obtain a homogeneous solution. This solution and ion-exchanged water (50 g) for concentration adjustment were added to the mixed slurry and mixed uniformly. After that, the inorganic powder was dried by spray drying while lightly mixing the dispersion, and recovered from the cyclone recovery section and the main body lower recovery section. Spray drying was performed using a spray dryer (spray dryer "FOC-20", manufactured by Okawara Chemical Machinery Co., Ltd.) at a disk rotation speed of 26,000 rpm and a drying atmosphere air temperature of 200°C. After spray drying, the recovered inorganic powder was vacuum-dried at 80°C for 17 hours to obtain mixed inorganic powder (E1):FE-1.

[0160] Mixed inorganic powders (E1): FE-2 to FE-5 and reference mixed inorganic powders: FE-7 to FE-9 were prepared in the same manner as FE-1, except that the types and proportions of the spherical inorganic powder (b1-3) slurry and the low-crystallinity rare-earth metal fluoride aggregated powder (d2-2) slurry used, and the amount of ion-exchanged water added for concentration adjustment were changed as shown in Table 6. Furthermore, after obtaining the mixed liquid under the conditions shown in Table 6, the spray dryer used for spray drying was changed to the spray dryer "RL-8" (manufactured by Okawara Chemical Machinery Co., Ltd.), and spray drying was performed at a spray pressure of 0.20 MPa and a drying atmosphere air temperature of 200°C. The obtained powder was then vacuum dried in the same manner to obtain mixed inorganic powder (E1):FE-6. For FE-1 to FE-9 obtained in this way, the average particle size (median diameter in the volume-based particle size distribution) was determined as follows. This is shown in Table 6.

[0161] <Evaluation of average particle size> 0.1 g of mixed inorganic granules was dispersed in 10 mL of ethanol and shaken by hand. Using a laser diffraction-scattering particle size analyzer "LS230" (Beckman Coulter), the optical model "Fraunhofer" was applied, and the average particle size was determined from the median diameter of the volume statistics.

[0162] [Table 6]

[0163] 4-5. [Other X-ray opaque fillers: Production of organic-inorganic composite low-crystalline rare-earth metal fluoride powders and granules] A monomer composition consisting of 80 parts by mass of UDMA, 20 parts by mass of 3G, and 1 part by mass of AIBN was weighed out, and 75 parts by mass of the above-mentioned FD1-1 were mixed using an agate mortar to prepare a paste-like raw material composition. Subsequently, the obtained raw material composition was heat-cured by heating under nitrogen pressure at 100°C for 30 minutes using a nitrogen-pressure thermal polymerization oven (manufactured by Towa Giken Co., Ltd.) to obtain a cured body consisting of a composite in which mechanochemically treated YbF3 particles are dispersed in a resin matrix (YbF3 particle content: 75.0% by mass). The obtained cured body and zirconia balls (diameter: 25 mm) were placed in a zirconia pot and subjected to rotary grinding for 60 minutes to obtain a pulverized product of the cured material. Coarse particles were removed from this pulverized product using a stainless steel sieve with a mesh size of 45 μm to obtain the organic-inorganic composite aggregate X-ray opaque filler CFD-1. The average particle size (median diameter in the volume-based particle size distribution) of the obtained organic-inorganic composite aggregate X-ray opaque packing material CFD-1 was determined in the same manner as in (E) above, and was found to be 26.3 μm.

[0164] II. Examples and Comparative Examples Example 1 A homogeneous polymerizable monomer composition was prepared by adding 0.2 parts by mass of CQ, 0.5 parts by mass of DMBE, and 0.15 parts by mass of HQME to 100 parts by mass of monomer component A-1 and mixing. Next, 58 parts by mass of FB-1, an inorganic spherical powder (b1-2) surface-treated with γ-methacryloyloxypropyltrimethoxysilane as (B1), 105 parts by mass of CF-1 as (B2), and 47 parts by mass of FE-1 as a mixed inorganic powder (E1) that will serve as a dispersed X-ray opaque packing material (D2). These were weighed out and thoroughly kneaded in a mortar under red light until homogeneous with the polymerizable monomer composition to form a paste. A portion was then taken and observed by SEM using the method described below, confirming that the mixed inorganic powder (E1) that will serve as the dispersed X-ray opaque packing material (D2) was sufficiently crushed and that (d2-2) was dispersed as primary particles. Furthermore, 23 parts by mass of FD1-1, which is a low-crystalline rare-earth metal fluoride aggregate powder (d1-1) that will serve as an aggregated X-ray opaque filler (D1), was added, and the mixture was lightly mixed in a mortar until homogeneous and degassed to prepare a paste-like dental curable composition. The obtained dental curable composition was observed by SEM using the method shown below, and it was confirmed that the aggregated low-crystalline rare-earth metal fluoride aggregate powder (d1-1) that will serve as a dispersed X-ray opaque filler (D1) had not been disintegrated.

[0165] <Evaluation of Dispersive X-ray Opaque Filler (D2)> Before adding the low-crystallinity rare-earth metal fluoride aggregate powder (d1-1), a portion of the paste was taken and placed in a mold with a 7mmφ × 1mm through-hole. Polyester film was pressed onto both sides, then the polyester film was peeled off from only one side. The peeled side was then irradiated with a dental light curing unit (Elliper Deep Cure, 3M) from a distance of 3mm for 20 seconds. After the paste hardened, it was removed from the mold, placed in 10mL of ethanol, and treated with ultrasound for 20 minutes. The resulting hardened body was fixed to a sample stage with carbon tape with the light-irradiated surface facing upwards, and a measurement sample was prepared by applying a conductive treatment (platinum deposition). The backscattered electron image of this measurement sample was observed at 1,000x magnification using a scanning electron microscope (JEOL Ltd. "JSM-7800F PRIME"), and it was confirmed that there were no bright particles larger than 3μm observed within the unit field of view of the image.

[0166] <Evaluation of aggregated X-ray opaque packing material (D1)> The obtained dental hardening composition was observed using a scanning electron microscope in the same manner as the evaluation of the dispersed radiopaque filling material (D2) described above, and it was confirmed that there were multiple (10 or more) highly bright particles of 1 μm or larger.

[0167] The obtained dental curable compositions were evaluated for paste consistency, drip, flowability, dispensing feel, radial distribution function, visually observed coloration, color matching, radiopaqueness, flexural strength, and contrast ratio using the method described below. The results are shown in Table 9. Note that the amount of (B1) in the table is calculated by totaling the inorganic spherical granules (b1-2) and the inorganic spherical granules (b1-3) contained in the mixed inorganic granules (E1). The ratio of (B2) to the total amount of (B1) and (B2) in the table is calculated by totaling the amount of organic inorganic composite granules (B2) to the total amount of inorganic spherical granules (b1-2), organic inorganic composite granules (B2), and inorganic spherical granules (b1-3) contained in the mixed inorganic granules (E1). In addition, the amount of the dispersion X-ray radiopaque filler (D2) in the table, that is, the amount (d2), when the mixed inorganic powder (E1) is included, is calculated based on the amount of the low-crystalline rare earth fluoride powder (d2-2) contained in (E1), and the amount of the X-ray radiopaque filler (D) is calculated as the total amount of the amount of the aggregated X-ray radiopaque filler (D1), the above-mentioned amount (D2), and the amount (d) in other X-ray radiopaque fillers.

[0168] <Evaluation method for the dispersion state (radial distribution function) of inorganic spherical particles> The dispersion state (radial distribution function) of the inorganic spherical particles in the curable composition was evaluated by the following procedure. The prepared paste-like dental curable composition was placed in a mold having a through-hole of 7 mm φ × 1 mm, and polyester films were pressure-bonded to both sides. The distance was adjusted so that the irradiation intensity on the surface of the polyester film was 1000 mW / cm 2 and both sides were irradiated with light for 20 seconds each using a dental light irradiator (Elipar Deep Cure, manufactured by 3M). After curing the dental curable composition, it was taken out of the mold to prepare a cured body. For the prepared cured body, cross-sectional milling was performed under the conditions of 2 kV and 20 minutes using an ion milling device (IM4000, manufactured by Hitachi, Ltd.) to obtain an observation plane. Then, after fixing the cured body on the sample stage with carbon paste, a measurement sample subjected to conductive treatment (platinum evaporation) on the observation plane was prepared. Next, this measurement sample was observed at a magnification of 10,000 times with an electron microscope (JSM-7800F PRIME, manufactured by JEOL Ltd.), and the coordinates in the observation image were obtained for 1,000 inorganic spherical particles in the obtained observation image using image analysis software (Simple Digiizer ver3.2, Free-soft). Arbitrarily select one coordinate of an inorganic spherical particle from the obtained coordinate data, draw a circle with a radius of a distance t containing at least 200 or more inorganic spherical particles centered on the selected inorganic spherical particle, determine the number of spherical particles contained in the circle, and calculate the average particle density <ρ> (unit: particles / cm 2The following equation was calculated. dr is a value of approximately r0 / 100 to r0 / 10 (where r0 represents the average primary particle diameter of inorganic spherical particles). The number of particles dn contained within the region between the circle at a distance r and the circle at a distance r+dr from the central inorganic spherical particle, and the area da of the aforementioned 54 region are determined. Using the values ​​of <ρ>, dn, and da obtained in this way, the following equation is used. ·g(r)={1 / <ρ>}×{dn / da} The radial distribution function g(r) was determined by calculating the following. Subsequently, a graph was created showing the relationship between the radial distribution function and r / r0 (where r represents an arbitrary distance from the center of the circle, and r0 represents the average primary particle diameter of the inorganic spherical particles). Based on the obtained graph, it was evaluated whether the following conditions [Condition 1] and [Condition 2] were satisfied (○) or not (×). [Condition 1] The nearest neighbor particle distance: r1, defined as r corresponding to the peak top of the peak closest to the origin among the peaks appearing in the radial distribution function graph, is a value of 1 to 2 times the average particle diameter: r0. [Condition 2] The minimum value of the radial distribution function g(r) between the nearest neighbor particle distance: r2, defined as the r corresponding to the peak top of the second closest peak from the origin among the peaks appearing in the radial distribution function graph, and the nearest neighbor particle distance: r1, is a value between 0.56 and 1.10.

[0169] <Visual evaluation of colored light> A polyacetal mold with a φ7mm x 1mm deep hole is filled by dispensing the paste from the syringe container, then pressed with a polypropylene film, and a light intensity of 1000mW / cm² is applied from above. 2 After curing the material by irradiating it with light for 20 seconds using an LED dental light curing unit (Ellipa Deep Cure, manufactured by 3M), the cured material was removed from the mold and placed on the adhesive side of a black tape (carbon tape) approximately 10 mm square, and the color tone of the colored light was checked visually.

[0170] <Visual evaluation of color compatibility> A hard resin tooth was used to recreate a Class I cavity (4 mm in diameter, 2 mm deep) in the center of the occlusal surface of the lower right sixth tooth. The defective area was filled with a hardening composition, hardened, and polished. The color match was visually confirmed and evaluated on a 5-point scale from 1 to 5 as shown below. 1: The color of the restoration is indistinguishable from that of a hard resin tooth. 2: The color of the restoration matches well with the hard resin tooth. 3. The color of the restoration is similar to that of a hard resin tooth. 4. The color of the restoration is similar to that of the hard resin tooth, but the fit is not good. 5. The color of the restoration does not match that of the hard resin tooth. For the hard resin teeth, we used high-saturation hard resin teeth (equivalent to A4) and low-saturation hard resin teeth (equivalent to A1) within the A-series (reddish-brown) category of the shade guide ("VITA Classical," manufactured by VITA), and high-saturation hard resin teeth (equivalent to B4) and low-saturation hard resin teeth (equivalent to B1) within the B-series (reddish-yellow) category of the shade guide ("VITA Classical," manufactured by VITA).

[0171] <Method for measuring the contrast ratio (Yb / Yw) of a cured cured composition> The prepared paste-like dental curing composition was placed in a mold with a through-hole measuring 7 mm in diameter and 1 mm in length, and polyester films were pressed onto both sides. The irradiation intensity on the surface of the polyester film was 1000 mW / cm². 2 The distance was adjusted accordingly, and both sides were irradiated with a dental light curing unit (Ellipa Deep Cure, 3M) for 20 seconds each. After the dental hardening composition was cured, it was removed from the mold, and the Y values ​​of the tristimulus values ​​(black and white background) of the cured body were measured using a colorimeter (Tokyo Denshoku "TC-1800MKII"). The following formula was used: Contrast ratio (Yb / Yw) = Y value when background is black / Y value when background is white The contrast ratio (Yb / Yw) was calculated based on this.

[0172] <Method for measuring "flowability"> The prepared paste-like dental hardening composition was left to stand in a 45°C incubator for one day, then filled into a cylindrical syringe. A plunger for dispensing the contents of the syringe and a 20G needle tip were attached to the syringe tip. After standing in a 25°C constant temperature room for 30 minutes, a circle with a diameter of 5 mm was drawn on a glass plate. 0.1 g of the dental hardening composition was dispensed into the circle, and then left to stand horizontally in a 37°C incubator for 2 minutes. The spread of the paste during this time was measured by measuring the vertical and horizontal diameters, and the average of the two was calculated. This evaluation was performed twice, and the average value was defined as the flowability of the paste.

[0173] <Method for measuring "sagging"> The prepared paste-like dental hardening composition was left to stand in a 45°C incubator for one day, then filled into a cylindrical syringe. A plunger for dispensing the contents of the syringe and a 20G needle tip were attached to the syringe tip. After standing in a 25°C constant temperature room for 30 minutes, 0.03 g of the dental hardening composition was extruded onto a glass plate from the tip of the needle tip. The extruded dental hardening composition was fixed vertically, and the distance the paste moved was measured after standing in a 37°C incubator for one minute. The above evaluation was performed twice, and the average value was taken as the paste drip.

[0174] <Method for measuring "concentration"> The consistency of the prepared paste-like dental curing composition was measured by the following method after it had been left to stand in a 45°C incubator for 1 day and then at 25°C for 30 minutes. 0.2 g of paste was weighed onto a polypropylene film, with the center slightly raised. A polypropylene film, a glass plate, and a weight (totaling 50 g) were placed on top in this order. After 10 seconds, the glass plate and weight were removed, and the vertical and horizontal diameters of the paste were measured through the polypropylene film. The average of these two measurements was then calculated. This evaluation was performed twice, and the average value was taken as the consistency of the paste.

[0175] <Evaluation of the sensation of discharge> The prepared paste-like dental hardening composition was left to stand in a 45°C incubator for one day, then filled into a cylindrical syringe. A plunger for dispensing the contents of the syringe and a 20G needle tip were attached to the tip of the syringe. 0.2g of paste was dispensed from the needle tip onto a glass plate (5cm x 10cm), and the ease of pressing the plunger was checked. The feel of dispensing the paste was evaluated according to the following evaluation criteria. A dispensing feel score of 1 to 3 was considered acceptable. 1: Paste can be dispensed even with light pressure, and the dispensing performance is excellent. 2: Paste can be dispensed without difficulty, and the dispensing performance is good. 3: The paste can be dispensed by pressing with a little force, and the dispensing performance is acceptable. 4. While it is possible to dispense the paste by pressing hard, the dispensing performance is poor. 5: The paste cannot be dispensed at all.

[0176] <Method for measuring "X-ray contrast-enhancing properties"> A polyethylene terephthalate mold with a 15mm diameter and 1mm thick hole was filled with paste and pressed with a polypropylene film. The mold was then exposed to light from a visible light irradiator (Tokuyama "Powerlight") five times, changing its position each time to ensure even illumination. After removing the polypropylene film, the cured body was removed from the mold and used as a sample. The prepared sample was observed using a tabletop X-ray transmission inspection system (μB1300, Matsusada Precision). In addition, aluminum step wedges with thicknesses of 1-4mm were observed simultaneously with the sample. The observed images were imported into dedicated image acquisition software (μRayVision, Matsusada Precision), and the brightness of the sample and aluminum step wedges was measured. A calibration curve was created from the brightness of the aluminum step wedges of each thickness, and the X-ray contrast properties of the sample were calculated as equivalent to the aluminum thickness (%Al).

[0177] <Method for measuring "flexural strength"> For the dental curing composition paste, the paste was filled into a stainless steel mold and pressed with a polypropylene film. Using a visible light curing unit (Elliper Deep Cure, 3M), the paste was irradiated with light from one side for 30 seconds x 3 times, changing positions to ensure the entire surface was exposed to light, and then pressed tightly against the polypropylene film. Next, the same process was repeated from the opposite side, pressed tightly against the polypropylene film for 30 seconds x 3 times, to obtain a cured body. The cured body was shaped into a 2 x 2 x 25 mm rectangular prism using #1500 waterproof abrasive paper. This sample was mounted on a testing machine (Shimadzu Corporation "Autograph AG5000D"), and the three-point bending fracture strength was measured with a support distance of 20 mm and a crosshead speed of 1 mm / min. A load-deflection curve was obtained, and the bending strength was calculated using the formula shown below. Five test pieces were evaluated, and the average value was taken as the bending strength. Formula: σB=(3PS) / (2WB 2 ) The symbols above represent, respectively: σB: bending strength (Pa), P: load at fracture of the test specimen (N), S: distance between supports (m), W: width of the test specimen (m), and B: thickness of the test specimen (m).

[0178] Examples 2-13, Comparative Examples 1-13 A paste-like dental curable composition was prepared in the same manner as in Example 1, except that the monomer component (A), inorganic spherical powder (B1), organic-inorganic composite powder (B2), agglomerated X-ray opaque filler (D1), and mixed inorganic powder (E) used were changed as shown in Tables 7 and 8. The obtained composition was evaluated in the same manner as in Example 1. The results are shown in Tables 9 and 10.

[0179] Example 14 A homogeneous polymerizable monomer composition was prepared by adding 0.2 parts by mass of CQ, 0.5 parts by mass of DMBE, and 0.15 parts by mass of HQME to 100 parts by mass of polymerizable monomer A-1 and mixing. Next, 82 parts by mass of inorganic spherical powder FB-1 surface-treated with γ-methacryloyloxypropyltrimethoxysilane, 105 parts by mass of organic-inorganic composite powder CF-1, and 23 parts by mass of X-ray opaque filler Fd-1 were weighed out and thoroughly kneaded with the polymerizable monomer composition in a mortar under red light until homogeneous, and it was confirmed that the X-ray opaque filler Fd-1 was dispersed as primary particles in the same manner as in Example 1. Subsequently, 23 parts by mass of FD1-1, which is a low-crystalline rare-earth metal fluoride aggregate powder (d1-1) that serves as an aggregated X-ray opaque filler (D1), were added, and the mixture was lightly mixed in a mortar until homogeneous and degassed to prepare a paste-like dental curable composition. The obtained composition was evaluated in the same manner as in Example 1. The results are shown in Table 9.

[0180] Comparative Example 14 A homogeneous polymerizable monomer composition was prepared by mixing 100 parts by mass of polymerizable monomer A-1 with 0.2 parts by mass of CQ, 0.5 parts by mass of DMBE, and 0.15 parts by mass of HQME. Next, 58 parts by mass of inorganic spherical powder FB-1 surface-treated with γ-methacryloyloxypropyltrimethoxysilane, 105 parts by mass of organic-inorganic composite powder CF-1, and 70 parts by mass of organic-inorganic composite aggregated X-ray opaque filler CFD-1 were weighed out and kneaded with the polymerizable monomer composition in a mortar under red light until homogeneous and degassed to prepare a paste-like dental curable composition. The obtained composition was evaluated in the same manner as in Example 1. The results are shown in Table 10.

[0181] Comparative Example 15 To 100 parts by mass of the coincident monomer A-1, 0.2 parts by mass of CQ, 0.5 parts by mass of DMBE, and 0.15 parts by mass of HQME were added and mixed to prepare a uniform polymerizable monomer composition. Next, 58 parts by mass of an inorganic spherical powder FB-1 surface-treated with γ-methacryloyloxypropyltrimethoxysilane, 105 parts by mass of an organic-inorganic composite powder CF-1, and 70 parts by mass of an X-ray radiopaque filler Fd-1 were weighed out and kneaded with the above polymerizable monomer composition in a mortar under red light until uniform and then defoamed to prepare a paste-like dental curable composition. The obtained composition was evaluated in the same manner as in Example 1. The results are shown in Table 10.

[0182]

Table 7

[0183]

Table 8

[0184]

Table 9

[0185]

Table 10

[0186] As understood from the results of Examples 1 to 14, the dental curable composition of the present invention has a cured body with high X-ray contrast, can be suitably used as a structural color system CR capable of aesthetic restoration, and has good fluidity and formability.

[0187] As understood from the results of Comparative Example 1, when the total content of (B1) and (B2) is less than 150 parts by mass, the expression of structural color is weak and the color tone compatibility is poor. As understood from the results of Comparative Example 2, when the total content of (B1) and (B2) exceeds 300 parts by mass, it can be seen that the paste becomes hard and the ejection feeling becomes heavy. As understood from the results of Comparative Example 3, when the ratio of (B2) to the total amount of (B1) and (B2) is less than 50% by mass, it can be seen that the paste becomes hard and the ejection feeling becomes heavy. As understood from the results of Comparative Example 4, when the ratio of (B2) to the total amount of (B1) and (B2) exceeds 70% by mass, it can be seen that the ejection feeling becomes heavy.

[0188] As understood from the results of Comparative Example 5, when the content of the dispersed radiopaque filler (D2) exceeds 25 parts by mass and when the content of the radiopaque filler (D) exceeds 75 parts by mass, not only is the color tone compatibility poor, but the flexural strength also tends to decrease. As understood from the results of Comparative Example 6, when the content of the radiopaque filler (D) is less than 30 parts by mass, it can be seen that the radiopacity decreases. As understood from the results of Comparative Example 7, when the content of the dispersed radiopaque filler (D2) is less than 5 parts by mass, it can be seen that the flow value and the sag value become high and the desired formability as a low flow cannot be obtained.

[0189] As understood from the results of Comparative Example 8, when the refractive index of the monomer component is larger than the refractive index of the inorganic powder particles, no yellowish-red structural color is expressed and the color tone compatibility is poor. As understood from the results of Comparative Example 9, when the inorganic spherical powder particles are amorphous, no yellowish-red structural color is expressed and the color tone compatibility is poor. As understood from the results of Comparative Example 10, when the particle size of the inorganic spherical powder particles (b) is less than 230 nm, no yellowish-red structural color is expressed and the color tone compatibility is poor. As understood from the results of Comparative Example 11, when the ratio of the inorganic spherical powder particles in the organic-inorganic composite powder particles exceeds 95% by mass, it can be seen that the organic-inorganic composite powder particles are crushed in the dental curable composition and the flexural strength is poor.

[0190] As can be seen from the results of Comparative Example 12, when the particle size of the aggregated X-ray opaque filler (D1) exceeds 30 μm, the flexural strength is inferior. As can be seen from the results of Comparative Example 13, when the full width at half maximum of the crystalline rare earth metal fluoride is less than 0.3° without mechanochemical treatment, the transparency decreases and the color matching is inferior. Furthermore, when the particle size of the dispersed X-ray opaque filler (D2) exceeds 300 nm, the flow value becomes high, and the desired shape-forming properties cannot be obtained as a low-flow material.

[0191] As can be seen from the results of Comparative Example 14, when an X-ray opaque filler containing a predetermined amount of rare earth metal fluoride particles with a full width at half maximum of 0.3° or more of the maximum intensity peak is used in the resin matrix, although a yellow structural color is produced, the flow value and sagging value become high, and the desired shapeability cannot be obtained as a low-flow filler. Furthermore, as can be seen from the results of Comparative Example 15, when a specific surface area of ​​25 to 100 m² is used as shown in Patent Document 1, 2 When crystalline rare earth metal fluorides at a concentration of / g were incorporated into a structural color system (CR), a low-flow type flowable CR could be prepared, but it did not exhibit a yellow-red structural color, indicating poor color compatibility.

[0192] Examples 15-24 In Examples 1-14 and Comparative Examples 1-15, a combination of CQ and DMBE and HQME were used as the photopolymerization initiator (C) in all examples. Therefore, in these examples, other photopolymerization initiator systems were used, and the dental curable compositions were prepared in the same manner as in Example 1. The photocatalytic systems used in each example are as follows. Example 15: Combination of CQ and DMA and HQME. (A) The proportions per 100g by weight were: CQ: 0.2 parts by mass, DMA: 0.5 parts by mass, and HQME: 0.15 parts by mass. Example 16: Combination of CQ and DMBA with HQME. CQ: 0.2 parts by mass, DMBA: 0.5 parts by mass, and HQME: 0.15 parts by mass. Example 17: Combination of CQ, DMBE, and DPIC with HQME. CQ: 0.2 parts by mass, DMBE: 0.5 parts by mass, DPIC: 0.4 parts by mass, and HQME: 0.15 parts by mass. Examples 18-24: Same as Example 17 except that the tertiary amine compound used is changed as shown in Table 11. The dental curable compositions obtained in Examples 15 and 16 were evaluated in the same manner as in Example 1. Examples 17 to 24 were evaluated in the same manner as in Example 1, except that the light irradiation time during the bending strength evaluation was changed from 30 seconds to 10 seconds. The evaluation results are shown in Table 12.

[0193] [Table 11]

[0194] [Table 12]

[0195] As can be seen from the results of Examples 15 and 16, even when DMA and DMBA are used, the dental curable composition of the present invention has a cured body that has high radiopaqueness, can be suitably used as a structural color-based CR for aesthetic restoration, and has good fluidity and moldability. As can be seen from the results of Examples 17 to 24, the dental curable composition of the present invention, which contains a photosensitizer, a tertiary amine compound, and a photoacid generator as polymerization initiators, has a cured body that has high radiopaqueness, can be suitably used as a structural color-based CR for aesthetic restoration, has good fluidity and moldability, and also has high flexural strength even when the light irradiation time is shortened.

Claims

1. A photopolymerizable and curable composition comprising a monomer component (A) consisting of one radical polymerizable monomer or a mixture of multiple radical polymerizable monomers, an inorganic filler (B), and a photopolymerization initiator (C), (1) The above (B) consists of an aggregate of inorganic spherical particles whose uniform primary particle diameter, as measured by electron microscopy, is a predetermined value within the range of 100 to 1000 nm, wherein the individual inorganic spherical particles constituting the aggregate are composed of substantially the same substance, and the aggregate contains one or more "groups of spherical particles of the same particle size" (G-PID) in which 90% or more of the total number of particles in the particle size distribution based on the number of particles are located within 5% before or after the predetermined value of the average primary particle diameter. 1) When the number of the one or more G-PIDs is a, each G-PID is ordered in ascending order of its average primary particle diameter. ｍ (However, m is 1 when a is 1, and a natural number from 1 to a when a is 2 or greater.) When expressed as such, each G-PID when a is 2 or greater ｍ The materials constituting each individual particle may be different from each other, and in that case each G-PID ｍ The average primary particle diameters differ from each other by more than 25 nm. 2) Let the refractive index with respect to the sodium D line at 25°C be n, and let the refractive index of the cured product of the monomer component (A) be n （ＭＸ） Let the refractive index of the inorganic spherical particles constituting each G - PID ｍ be n （Ｇ－ＰＩＤｍ） When it is set as such, for any n （Ｇ－ＰＩＤｍ） , n （ＭＸ） <n （Ｇ－ＰＩＤｍ） satisfies all the conditions such that the relationship holds (2) For a cured body obtained by curing the photopolymerizable composition, the radial distribution function g(r) representing the probability that another inorganic spherical particle exists at a distance r from the center of any inorganic spherical particle dispersed in the cured body is determined based on a scanning electron microscope image with the interior surface of the cured body as the observation plane, and is based on the following: the average particle density of the inorganic spherical particles in the observation plane: <ρ>, the number of inorganic spherical particles in the region between a circle at a distance r from any inorganic spherical particle in the observation plane and a circle at a distance r+dr: dn, and the area of ​​the region: da (where da = 2πr・dr). Formula: g(r)={1 / <ρ>}×{dn / da} When expressed as such, the arrangement structure of inorganic spherical particles in the hardened body is 1) The distance from the center of any inorganic spherical particle dispersed in the hardened body: r, and the average particle diameter of all inorganic spherical particles dispersed in the hardened body: r ０ Then, we divide to get a dimensionless number (r / r ０ With the x-axis and the radial distribution function g(r) as the y-axis, the r / r ０ In a radial distribution function graph showing the relationship between and the aforementioned g(r) corresponding to r at that time, the nearest neighbor particle distance: r is defined as the r corresponding to the peak top of the peak closest to the origin among the peaks appearing in the radial distribution function graph. １ However, the average particle size of all inorganic spherical particles dispersed in the hardened mixture is r ０ The condition that the value is between 1 and 2 times the given value, 2) Among the peaks appearing in the radial distribution function graph, the next nearest neighbor particle distance: r is defined as the peak top of the second closest peak from the origin. ２ In this case, the nearest neighbor particle distance: r １ and the distance between the next nearest particle: r ２ The condition is that the minimum value of the radial distribution function g(r) between and is between 0.56 and 1.

10. Having a short-range ordered structure that satisfies the following conditions, In a dental curing composition comprising a photopolymerizable curable composition, (3) The viscosity of the monomer component (A) at 25°C is 100 to 1000 mPa·s, (4) All of the one or more G-PIDs consist of inorganic spherical powder (b) having an average primary particle diameter in the range of 230 to 500 nm, which is composed of inorganic spherical particles whose polarity of the zeta potential measured in water is negative. 1) A part of (b) above (b1) is formulated as (B1), which consists of at least one of the group comprising primary particles (b1-1), a powder / granular material composed of aggregated particles of the primary particles (b1-2), and a composite aggregated powder / granular material (E) composed of aggregated particles of the primary particles and other inorganic particles (e), and the powder / granular material (b1-2) and the composite aggregated powder / granular material (E) may be crushed and dispersed in the dental curable composition. 2) The remainder (b2) of (b) above is a specific single G-PID ｎ (However, n is 1 when a is 1, and any one natural number from 1 to a when a is 2 or greater.) Inorganic spherical powder (b2 ｎ ) is dispersed in a resin matrix having a refractive index smaller than that of the constituent particles of the powder, (b2 ｎ A composite that does not contain (b2) other than ) and the inorganic spherical powder (b2) relative to the total mass of the composite ｎ It is included as one or more organic-inorganic composite powders (B2) composed of particles made of a composite having an average inorganic content of 30 to 95% by mass, defined by the total mass of the organic-inorganic composites, 3) The total content of (B1) and the one or more (B2) per 100 parts by mass of (A) is 150 to 300 parts by mass, and the content of the one or more (B2) in the total content is 50 to 70% by mass. (5) The (B) further comprises an X-ray opaque filler (D) comprising an aggregated X-ray opaque filler (D1) and a dispersed X-ray opaque filler (D2), 1) Both (D1) and (D2) are composed of crystalline rare earth metal fluoride particles that exhibit a positive zeta potential when measured in water, and the average primary particle size is 1 to 300 nm, and the full width at half maximum of the maximum intensity peak originating from the crystalline rare earth metal fluoride in the X-ray diffraction pattern is 0.3° or more, and the low crystalline rare earth fluoride powder (d) is used as the active ingredient. 2) The (D1) is composed of aggregated particles formed by the aggregation of primary particles constituting the low-crystalline rare-earth fluoride powder (d1) which is the active ingredient, and consists of low-crystalline rare-earth metal fluoride aggregated powder (d1-1) having an average agglutinator diameter defined as the median diameter in the volume-based particle size distribution measured by laser diffraction-scattering method of 1 to 30 μm, and the (d1-1) is included as aggregated particles in the dental curable composition. 3) The (D2) consists of primary particles (d2-2) of (d2) contained in a mixed inorganic powder (E1) having an average aggregate particle diameter of 1 to 50 μm, which is composed of non-aggregated powder (d2-1) composed of primary particles constituting the low-crystalline rare earth fluoride powder (d2) that constitutes the active ingredient, and / or aggregated particles (e1) of the primary particles constituting (d2) and at least a portion of the constituent particles of (b1-3), wherein the (D2) contains (d2-1), and when the (D2) contains (d2-1), the (d2-1) is contained in the dental curable composition in a dispersed state as primary particles, and when the (D2) contains (d2-2), the (d2-2) is contained in the dental curable composition in a dispersed state as primary particles which are the defatted product of the aggregated particles (e1). 4) The total content of (d) and the total content of (d2) per 100 mass of (A) are: (d): 30 to 75 parts by mass and (d2): 5 to 25 parts by mass. A dental hardening composition characterized by the following features.

2. The dental curable composition according to claim 1, which provides a cured body that exhibits a predetermined structural color regardless of the angle of incidence of light.

3. The dental curable composition according to claim 1, wherein the inorganic spherical particles (b) consist of a silica-based inorganic compound.

4. The average value of the total mass of the non-aggregated particles (d2-2) relative to the total mass of the inorganic spherical particles (b1-3) contained in each of the mixed aggregated particles (e1) constituting the mixed inorganic powder (E1) is within the range of 20 to 300 parts by mass. The dental curable composition according to claim 1.

5. The dental curable composition according to claim 1, wherein the content of the photopolymerization initiator (C) per 100 parts by mass of (A) is 0.01 to 10 parts by mass, and (C) contains 0.01 to 3.0 parts by mass of a tertiary amine compound (F) containing an aromatic amine compound containing a dimethylamino group per 100 parts by mass of (A).

6. A method for producing the dental curable composition described in claim 1, The process includes a kneading step of kneading the monomer component (A); the powder (b1-1) and / or the powder (b1-2); the one or more organic-inorganic composite powder (B2); the non-aggregated powder (d2-1) and / or the mixed inorganic powder (E1); the low-crystallinity rare-earth metal fluoride aggregated powder (d1-1); and the photopolymerization initiator (C). In the kneading step, the amounts of each component (B2), (d1-1), and the photopolymerization initiator (C) relative to 100 parts by mass of (A) are set to: (B2): 75 to 210 parts by mass, (d1-1): 5 to 70 parts by mass, and (C): 0.01 to 10 parts by mass, and further, The amounts of (b1-1) and / or (b1-2), and (d2-1) and / or (E1) relative to 100 mass of (A) are as follows: If (E1) is not included, the total amount of (b1-1) and (b1-2) shall be 45 to 150 parts by mass, and (d2-1) shall be 5 to 25 parts by mass. When incorporating (E1), the total amount of (b1-3) contained in (b1-1), (b1-2), and (E1) shall be 45 to 150 parts by mass, and the total amount of (d2-2) contained in (d2-1) and (E1) shall be 5 to 25 parts by mass. The method characterized by the above.

7. A manufacturing method according to claim 6, comprising the above (E1), The kneading step is a first kneading step in which (A) 100 parts by mass is mixed with (E1) or (E1) and (d2-1) in such a way that the total amount of (d2-1) and (d2-2) contained therein is a predetermined amount of (d2), and kneaded to obtain a paste in which (d2-1) and (d2-2) are uniformly dispersed as primary particles, The manufacturing method, comprising a second kneading step of adding a predetermined amount of (d1-1) to the paste obtained in the first kneading step, and kneading in a manner that does not disintegrate the aggregated particles constituting (d1-1).

8. A dental composite resin comprising the dental curable composition according to claim 1, wherein the contrast ratio T, defined by the ratio of Yb (Yb value measured under a black background) to Yw (Yw value measured under a white background) using a colorimeter, is 0.20 to 0.50 for a 1 mm thick cured sample, which serves as an indicator of the transparency of the cured body of the dental curable composition, is obtained.

9. The dental composite resin according to claim 8, wherein the "flow value," defined by the diameter of paste spread (mm) after 0.1 g of dental hardening composition is dispensed onto a glass plate and left to stand horizontally in a 37°C incubator for 2 minutes, is 3.0 to 8.0 (mm), and the "sag value," defined by the distance the paste moves (mm) after 0.03 g of dental hardening composition is dispensed onto a glass plate and left to stand vertically in a 37°C incubator for 1 minute, is 0.0 to 2.0 (mm).

10. The dental composite resin according to claim 8, which provides a hardened body in which the X-ray contrast (%Al) of the hardened body sample, calculated from the brightness when a 1 mm thick hardened body sample and an aluminum step wedge are observed using a tabletop X-ray transmission inspection device, is 200 to 300 (%Al).

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