Dental curable composition

Abstract

It is known to provide a hardened body that exhibits a structural color of a prescribed hue that is independent of the angle of incidence of light; [Problem] To impart X-ray non-penetrability to a hardened body without adversely affecting the appearance or transparency of a desired structural color in an "existing structural color dental curable composition" containing a polymerizable monomer and specific inorganic spherical particles; the present invention is characterized in that: a prescribed amount of an X-ray non-penetrating filler comprising organic-inorganic composite particles obtained by dispersing a prescribed amount of rare earth metal fluoride particles in a resin matrix is mixed in the "existing structural color dental curable composition"; the total width at half maximum of the rare earth metal fluoride particles derived from the maximum intensity peak of the rare earth metal fluoride particles as measured by X-ray diffraction measurement is 0.3 DEG or more, and the refractive index difference between the resin matrix and the polymerizable monomer of the "existing structural color dental curable composition" is 0.1 or less.

Description

Technical Field

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

[0002] In dental treatment, a dental filling material called dental composite resin (hereinafter referred to as CR) is filled into a cavity after caries removal, and then cured to seal the cavity. Typically, a curable composition containing a polymerizable monomer, a filler, and a polymerization initiator as main components is used as such a dental filling material.

[0003] Restorations using dental composite resin (CR) (CR restorations) are rapidly gaining popularity due to their ability to reduce the amount of tooth removal, impart a color tone comparable to natural tooth color, and ease of use. Furthermore, in recent years, CR restorations have been used not only for the restoration of anterior teeth but also for molars, which are subject to high occlusal pressure, due to their improved mechanical strength and bonding strength.

[0004] To achieve aesthetically pleasing restorations with CR, the color (hue and tone) of the tooth being restored (the tooth being restored) is typically determined (this color determination is sometimes referred to as shade taking), and CR that harmonizes with the determined color is selected for restoration. To achieve a highly aesthetic restoration that faithfully reproduces the color variations that occur with the tooth, multiple CRs of varying colors must be layered together. Furthermore, CR is typically colored by mixing pigments or dyes into the CR. However, these substances fade or discolor over time in the cured product after treatment. Consequently, discoloration may occur over time after restoration, making the appearance of the repaired area inconsistent with that of the natural tooth.

[0005] In recent years, a type of CR has been proposed and has attracted attention (see Patent Documents 1 and 2). This CR refers to the use of a filler containing spherical inorganic particles with a specific average particle size and particle size distribution, in which the refractive index of the spherical inorganic particles is greater than the refractive index of the resin portion that becomes the matrix when cured. In this way, a CR that exhibits a structural color of a specified hue is exhibited by utilizing interference or scattering of light (hereinafter, a CR that exhibits such a structural color is also referred to as a structural color system CR), wherein the specified hue is independent of the incident angle of light.

[0006] The above-mentioned structural color system CR has the following excellent characteristics: (1) Since no dye substances or pigment substances are used, it is not likely to cause the above-mentioned problem of color change over time; (2) Based on the average particle diameter of the spherical inorganic particles used, it exhibits a structural color of a specific hue that is independent of the incident angle of light. In particular, when spherical inorganic particles with an average primary particle diameter of 230 to 350 nm are used, it can be colored into yellow to red, which is the same color as dentin; (3) Since the hardened body has appropriate transparency, it is easy to blend with the color of the tooth to be restored. Without the need for complicated color matching (shadetaking) or color selection of composite resins, a composite resin can be used to repair teeth to be restored with a wide range of colors to an appearance close to that of natural teeth.

[0007] Regarding the polymerizable and curable composition constituting the above-mentioned structural color system CR, it is known that it satisfies the following conditions ① and ②, and when the following condition ③ is further satisfied, a hardened body that can more reliably exhibit the desired structural color can be provided (refer to Patent Document 2).

[0008] ① As a constituent, it contains a polymerizable monomer (A), inorganic particles (B), and a photoinitiator (C).

[0009] ② The above-mentioned inorganic particles (B) satisfy all the conditions of (②-1), (②-2), and (②-3). Among them,

[0010] Condition (②-1): It contains one or more "groups of spherical particles having identical diameter" (G-PID). Among them, the one or more "groups of spherical particles having identical diameter" (G-PID) are composed of aggregates of inorganic spherical particles having a specified average primary particle diameter in the range of 100 to 1000 nm. Each inorganic spherical particle constituting the aggregate is substantially composed of the same substance, and in the number-based particle size distribution of the aggregate, more than 90% of all the particles exist within the range of ±5% of the specified average primary particle diameter.

[0011] Condition (②-2): When the number of the one or more "groups of spherical particles having identical diameter" is set to a, each "group of spherical particles having identical diameter" is represented by G-PID m (where m is 1 when a is 1, and m is a natural number from 1 to a when a is 2 or more) in ascending order of its average primary particle diameter. When a is 2 or more, the substances of the respective particles constituting each G-PID m can be different from each other. In this case, the average primary particle diameters of the respective G-PID m differ from each other by 25 nm or more.

[0012] Condition (②-3): When the refractive index at 25 °C of the cured product of the polymerizable monomer component (A) is set to n (MX) and the refractive index at 25 °C of the inorganic spherical particles constituting each of the G-PIDs m is set to n (G-PIDm) for any n (G-PIDm) , the relationship n (MX) < n (G-PIDm) holds.

[0013] ③Regarding the cured product obtained by curing the polymerization-curable composition, when the radial distribution function g(r) is expressed by the formula: g(r) = {1 / <ρ>} × {dn / da} based on <ρ>, dn, and da, the dispersion state of the inorganic particles (B) in the cured product satisfies the following conditions (I) and (II). Here, the radial distribution function g(r) is a function representing the probability that other inorganic spherical particles exist at a location at a distance r from the center of any inorganic spherical particle dispersed in the cured product, and <ρ>, dn, and da are determined based on a scanning electron microscope image with the inner surface of the cured product as the observation plane. Here, <ρ> is the average particle density of the inorganic spherical particles in the observation plane, dn is the number of inorganic spherical particles existing 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, and da is the area of the region (da = 2πr × dr).

[0014] [Conditions that the dispersion state should satisfy]

[0015] (I) In a radial distribution function graph with the dimensionless number (r / r0) obtained by dividing r by r0 and normalizing it as the x-axis and the radial distribution function g(r) as the y-axis, which shows the relationship between r / r0 and the corresponding g(r) at this time, the closest interparticle distance r1 is a value that is more than 1 times and less than 2 times the average particle diameter r0 of the entire inorganic spherical particles dispersed in the cured product of the mixture. Here, r is the distance from the center of any inorganic spherical particle dispersed in the cured product, r0 is the average particle diameter of the entire inorganic spherical particles dispersed in the cured product, and the closest interparticle distance r1 is defined as the distance corresponding to the peak top of the peak closest to the origin among the peaks appearing in this radial distribution function graph.

[0016] (II) When using, as the next closest interparticle distance r2, the r corresponding to the peak top of the peak that is the second closest to the origin among the peaks appearing in the radial distribution function graph, the minimum value of the radial distribution function g(r) between the closest interparticle distance r1 and the next closest interparticle distance r2 is a value of 0.56 or more and 1.10 or less.

[0017] In addition, according to Patent Document 2, the colored light caused by interference in the hardened body is generated in the part where the constituent particles are regularly aggregated, and the colored light caused by scattering is generated in the part where the constituent particles are disorderly dispersed. Moreover, regarding the above condition (I), it is explained that when r1 is less than 1 times r0, there is more overlap between the particles in the plane, and when r1 exceeds 2 times r0, there are no particles near the selected central inorganic particle, and thus the short-range order disappears and the structural color is not exhibited; regarding the above condition (II), 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 is improved, not only the incident angle dependence of the light of the exhibited structural color is increased, but also the chroma of the hardened body is increased, so that it is difficult to obtain tonal harmony 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 an irregular structure, and it is difficult to obtain the target reflection performance, and thus it is difficult to exhibit the desired structural color.

[0018] In the polymerization curable composition that satisfies these conditions ① to ③ (hereinafter, also referred to as the conventional structure color system dental curable composition), when containing a plurality of spherical particle groups (G-PID) of the same particle size, each G-PID exhibits a structural color of a tone corresponding to its average primary particle size in the hardened body. Therefore, the overall color display tone can also be controlled by the combination of the mixed G-PIDs. This can be considered to be due to the following reason: when containing a plurality of G-PIDs, there is a certain difference in the size of their average primary particle sizes, and thus the inorganic spherical particles belonging to different G-PIDs do not replace each other and can be dispersed while having a short-range order structure capable of exhibiting a structural color in each G-PID.

[0019] In addition, as the filler mixed in the curable composition used as CR, including the conventional structure color system dental curable composition, inorganic oxide fillers are generally used, especially silica-based fillers. However, the X-ray non-penetrability of silica-based fillers is low. Therefore, during X-ray photography or CT photography during dental treatment, the hardened material in the cavity is not imaged, and thus it is difficult to distinguish the treatment site.

[0020] On the other hand, as a method for improving the X-ray non-penetrability of a hardened body of a curable composition used in various applications such as the curable composition used in the dental applications exemplified above, a method using a filler containing atoms with a large atomic number is known. For example, in Patent Document 3, a technique using a filler composed of rare earth metal fluorides with an atomic number of 57 to 71 is proposed.

[0021]

Prior Art Documents

[0022]

Patent Documents

[0023] Patent Document 1: Pamphlet of International Publication No. 2017 / 069274

[0024] Patent Document 2: Pamphlet of International Publication No. 2020 / 050123

[0025] Patent Document 3: Japanese Patent, Publication No. Tokukaihei 3-17803 Summary of the Invention

[0026] (Problems to be Solved by the Invention)

[0027] However, in the case of using rare earth metal fluorides as X-ray non-penetrating fillers mixed in curable compositions, as shown in FIG. 2 of Patent Document 3, as the content of rare earth metal fluorides increases, the transparency of the hardened body decreases. Therefore, in existing curable compositions using rare earth metal fluorides, in order to obtain a hardened body with high transparency, it is necessary to sacrifice X-ray non-penetrability, and thus it is difficult to obtain a hardened body with both excellent X-ray non-penetrability and transparency.

[0028] In addition, according to the research of the inventors of the present application, it has been confirmed that: in existing structural color dental curable compositions, when rare earth metal fluorides are mixed as X-ray non-penetrating fillers, not only the color tone harmony is impaired due to the above-mentioned decrease in transparency, but also sometimes an adverse effect is produced on the manifestation of the desired structural color (see Comparative Examples 2 to 5 described later).

[0029] The present invention has been completed in view of the above circumstances, and its object is to provide a dental curable composition: the hardened body has X-ray non-penetrability and can be suitably used as a structural color CR for aesthetic restoration.

[0030] (Means for Solving the Problems)

[0031] In order to solve the above problems, the dental curable composition of the present invention has the following characteristics:

[0032] The dental curable composition comprises 100 parts by mass of a polymerizable monomer, one or more "same-sized spherical particle groups" (G-PID) in a total amount of 10 to 1500 parts by mass, and a polymerization initiator. Among them, the one or more "same-sized spherical particle groups" (G-PID) are composed of an aggregate of inorganic spherical particles having a specified average primary particle diameter in 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, more than 90% of all the particle numbers are present within the range of ±5% of the specified average primary particle diameter;

[0033] When the number of the one or more "same-sized spherical particle groups" is set to a, each "same-sized spherical particle group" is represented by G-PID in ascending order of its average primary particle diameter. m (wherein when a = 1, m = 1; when a ≥ 2, m is a natural number from 1 to a). When a ≥ 2, the substances of the respective particles constituting each G-PID m can be different from each other. In this case, the average primary particle diameters of each G-PID m differ from each other by 25 nm or more;

[0034] When the refractive index of the cured product of the polymerizable monomer with respect to the sodium D line at 25°C is set to n (MX) and the refractive index of the inorganic spherical particles constituting each G-PID m with respect to the sodium D line at 25°C is set to n (G-PIDm) , for any n (G-PIDm) , the following relationship always holds:

[0035] n (MX) < n (G-PIDm) ;

[0036] The dental curable composition can provide a cured product that exhibits a structural color of a specified hue, wherein the specified hue does not depend on the incident angle of light.

[0037] An X-ray non-penetrating filler (hereinafter also referred to as a specific X-ray non-penetrating filler) containing 1 to 100 parts by mass in terms of the total mass of crystalline rare earth fluoride metal particles, wherein the X-ray non-penetrating filler is characterized in that it is composed of organic-inorganic composite particles in which a plurality of crystalline rare earth metal fluoride particles are dispersed in a resin matrix, and when the crystallinity of each of the crystalline rare earth metal fluoride particles constituting the powder formed by the crystalline rare earth metal fluoride particles is represented by the full width at half maximum (unit: °) of the maximum peak derived from the crystalline rare earth metal fluoride in the X-ray diffraction pattern obtained by X-ray diffraction measurement of the powder, the full width at half maximum of the crystalline rare earth metal fluoride particles is 0.3° or more;

[0038] The refractive index n of the cured product of the polymerizable monomer with respect to the sodium D line at 25 °C (MX) And the refractive index n of the resin material of the resin matrix constituting the organic-inorganic composite particles with respect to the sodium D line at 25 °C (F-MX) The absolute value of the difference|n (MX) -n (F-MX) |is 0 to 0.1, wherein the organic-inorganic composite particles constitute the X-ray non-penetrating filler.

[0039] In the above dental curable composition (hereinafter also referred to as the dental curable composition of the present invention), preferably: based on the total mass of the organic-inorganic composite particles, the content of the crystalline rare earth metal fluoride particles in the organic-inorganic composite particles constituting the X-ray non-penetrating filler is 60 to 90 mass%; preferably: the average particle size of the organic-inorganic composite particles is 22 μm to 70 μm. In addition, preferably: the rare earth metal fluoride particles are ytterbium fluoride particles.

[0040] Furthermore, preferably: the average primary particle size of all the "same particle size spherical particle groups" (G-PID) contained in the dental curable composition of the present invention is in the range of 230 to 350 nm.

[0041] In addition, in the dental curable composition of the present invention, preferably: other rare earth metal fluoride particles other than the rare earth metal fluoride particles mixed as the X-ray non-penetrating filler are not contained, or the content thereof is 5 parts by mass or less relative to 100 parts by mass of the polymerizable monomer.

[0042] In addition, preferably: a cured body having a contrast C of 0.20 to 0.50, which is an index of the transparency of the cured body of the dental curable composition, is provided, and the contrast C is the Y value measured with a color difference meter on a black background for a cured body sample having a thickness of 1 mm, that is, Y b And the Y value measured on a white background, that is, Yw Ratio Y b / Y w is defined.

[0043] In addition, it is preferable that: the mixing amount of the polymerization initiator is 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the polymerizable monomer. Further, it is preferable that: the full width at half maximum is 40° or less.

[0044] (Advantages of the Invention)

[0045] According to the present invention, the structural color dental hardenable composition of the present invention, which is obtained by mixing a specified amount of a specific X-ray non-penetrating filler into a dental hardenable composition known as a structural color CR, can impart high X-ray non-penetrability to the hardened body without impairing the excellent characteristics of the structural color CR when used as a CR. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 are X-ray contrast images of hardened bodies of the dental hardenable compositions of Example 1, 13, 19 and Comparative Example 1, 4, and aluminum materials with thicknesses of 1 mm, 2 mm, 3 mm and 4 mm. DETAILED DESCRIPTION OF THE INVENTION

[0047] The inventors of the present application conducted in-depth research to solve the problem that it is difficult to obtain a hardened body having both excellent X-ray non-penetrability and transparency in existing hardenable compositions. Among them, in the existing hardenable composition, rare earth metal fluorides are used as the main component constituting the X-ray non-penetrating filler.

[0048] As a result, it was found that: a hardenable composition mixed with a powder composed of crystalline rare earth metal fluoride particles such as crystalline ytterbium fluoride sometimes improves X-ray non-penetrability without reducing the transparency of the hardened body. Furthermore, based on such an insight, further research was conducted, and it was found that: such a phenomenon occurs when (i) the crystallinity of the crystalline rare earth metal fluoride particles is reduced by mechano-chemical treatment, and (ii) the full width at half maximum (FWHM) of the maximum intensity peak of the crystalline rare earth metal fluoride measured in X-ray diffraction measurement corresponding to the crystallite diameter as an index of crystallinity reaches a certain level or more (when the degree of crystallinity is reduced by a certain level or more), and a new X-ray non-penetrating filler composed of rare earth metal fluoride particles having such a specific crystallinity has been proposed (PCT / JP2022 / 031237).

[0049] After further research on the above X-ray non-penetrating filler, the inventors of the present application clarified that: in order to obtain sufficient X-ray non-penetrating property, a relatively large mixing amount is required. In addition, when mixed with the structural color CR, there is a tendency that the desired structural color is difficult to appear (refer to Comparative Examples 3 and 4 described later).

[0050] Furthermore, through further research, it was found that: when crystalline rare earth metal fluoride particles with a full width at half maximum (FWHM) of a certain value or more are mixed as organic-inorganic composite particles (specific X-ray non-penetrating filler) pre-compounded with an organic resin, even when the mixing amount of the rare earth metal fluoride particles is reduced, high X-ray non-penetrating property can be imparted. Moreover, even when mixed with the structural color CR, X-ray non-penetrating property can be imparted without having a great adverse effect on the appearance of the desired structural color, and thus the present invention was completed.

[0051] As described above, the dental curable composition of the present invention has an important feature in that it contains a specific X-ray non-penetrating filler. Therefore, after explaining the specific X-ray non-penetrating filler and its manufacturing method, the dental curable composition of the present invention will be described in detail.

[0052] It should be noted that in the specification of the present application, unless otherwise specified, the description of "x to y" using numerical values x and y means "x or more and y or less". In this description, when only the numerical value y has a unit, the unit also applies to the numerical value x. In addition, in the specification of the present application, the term (meth)acrylate refers to both acrylates and methacrylates. Similarly, the term (meth)acrylate refers to both acrylates and methacrylates, and the term (meth)acryloyl refers to both acryloyl and methacryloyl.

[0053] 1. Regarding the specific X-ray non-penetrating filler

[0054] (1) Outline of the specific X-ray non-penetrating filler

[0055] The specific X-ray non-penetrating filler is composed of organic-inorganic composite particles in which a plurality of crystalline rare earth metal fluoride particles are dispersed in a resin matrix. Among them, when the crystallinity of each crystalline rare earth metal fluoride particle constituting the powder formed by the crystalline rare earth metal fluoride particles is represented by the full width at half maximum (unit: °) of the maximum peak derived from the crystalline rare earth metal fluoride in the X-ray diffraction pattern obtained by performing X-ray diffraction measurement on the powder, the full width at half maximum of the crystalline rare earth metal fluoride particles is 0.3° or more.

[0056] It should be noted that the specific X-ray non-penetrating filler is usually composed only of the organic-inorganic composite particles (hereinafter also referred to as the particle main body), but may also contain admixture particles such as silica or titanium oxide (fine particles). In addition, regarding the organic-inorganic composite particles (particle main body), they can be particles subjected to physical surface treatment such as plasma treatment on their surfaces, or mechanical surface treatment through long-term friction stirring, etc., or particles subjected to coating agent treatment using a known coating agent such as silicone oil. Further, the crystalline rare earth metal fluoride particles in the organic-inorganic composite particles (particle main body) can also be particles surface-treated with a known surface treatment agent such as a silane coupling agent or a titanate coupling agent.

[0057] Generally, there is a known correlation between the full width at half maximum (FWHM) of the diffraction peak in X-ray diffraction measurement and the microcrystalline size, and it is known that the microcrystalline size is inversely proportional to the full width at half maximum. In addition, the lattice distortion also affects the full width at half maximum (FWHM), and there is a tendency for the full width at half maximum (FWHM) to increase when the lattice distortion is large. It can be considered that when the lattice distortion is large and the microcrystalline diameter is small, the fine microcrystals are oriented in various directions, resulting in a decrease in crystallinity. Therefore, the full width at half maximum can be said to be an index of the crystallinity of the rare earth metal fluoride (more specifically, the integrity of the crystal).

[0058] In the specification of this application, regarding the term "full width at half maximum" used hereinafter, unless otherwise specified, it refers to the full width at half maximum (unit: °) of the maximum peak derived from the crystalline rare earth metal fluoride in the X-ray diffraction pattern obtained by performing X-ray diffraction measurement on the powder, which represents the crystallinity of each crystalline rare earth metal fluoride particle constituting the powder formed by the crystalline rare earth metal fluoride particles.

[0059] Crystalline rare earth metal fluoride particles having a full width at half maximum of 0.3° or more, even when directly mixed in a dental curable composition without forming them into organic-inorganic composite particles in which they are combined with an organic resin, hardly reduce the transparency of the cured body of the dental curable composition (see PCT / JP2022 / 031237 and Comparative Examples 3 and 4 described later). The reason for exhibiting such an effect is inferred as follows. First, the diffuse reflection of light at the interface between the two has a greater impact on the reduction of transparency in a system in which inorganic fine particles are dispersed in a resin matrix. On the other hand, it is considered that: by the above-mentioned mechanochemical treatment, near the surface of the crystalline rare earth metal fluoride particles, it gradually becomes amorphous from the surface toward the inside. Moreover, in the case where such a phenomenon occurs, near the surface of the crystalline rare earth metal fluoride particles, a layer is formed in which the refractive index gradually decreases at a certain gradient from the inside toward the surface (hereinafter also referred to as a refractive index gradient layer). Moreover, within the formed refractive index gradient layer, there is a portion having a refractive index consistent with that of the resin matrix. From this, it can be considered that: as a whole, the proportion of reflected light decreases (the proportion of transmitted light increases), and the reduction of transparency is suppressed.

[0060] Even when a specific X-ray non-penetrating filler is used, when the polymerizable monomer of the dental curable composition satisfies the refractive index n (MX) and the refractive index n (F-MX) The absolute value of the difference |n (MX) -n (F-MX) | is in the range of 0 to 0.1, preferably 0 to 0.05, where the refractive index n (MX) is the refractive index of the cured body of the polymerizable monomer with respect to the sodium D line at 25°C, and the refractive index n (F-MX) is the refractive index of the resin material of the resin matrix constituting the organic-inorganic composite particles with respect to the sodium D line at 25°C, where the organic-inorganic composite particles constitute the specific X-ray non-penetrating filler. It is considered that this is because: the polymerizable monomer in the dental curable composition becomes the resin that forms the matrix of the cured body of the dental curable composition, and when the value of its refractive index n (F-MX) is approximate to the value of the refractive index n (F-MX) of the resin material of the resin matrix constituting the organic-inorganic composite particles, diffuse reflection of light hardly occurs on the surface of the organic-inorganic composite particles, (in other words, the resin matrix of the organic-inorganic composite particles and the resin matrix of the cured body of the dental curable composition are integrated), and thus the above-mentioned characteristics of the crystalline rare earth metal fluoride particles having a full width at half maximum of 0.3° or more are exhibited.

[0061] As described above, by making the full width at half maximum (FWHM) of the crystalline rare earth metal fluoride particles 0.3° or more, when hardening the curable composition mixed with the X-ray non-penetrating filler of the present invention, a hardened body excellent in both X-ray non-penetrability and transparency can be easily obtained. That is, even if the mixing amount of the X-ray non-penetrating filler of the present embodiment mixed in the curable composition is increased in order to improve the X-ray non-penetrability of the hardened body, a decrease in the transparency of the hardened body can be suppressed. The FWHM may be 0.3° or more, preferably 0.4° or more, and more preferably 0.5° or more. On the other hand, the upper limit value of the FWHM is not particularly limited, but is preferably 40° or less, more preferably 1° or less in practical use.

[0062] In addition, when crystalline rare earth metal fluoride particles having an FWHM of less than 0.3° are directly mixed or subjected to organic-inorganic compounding (as the same organic-inorganic composite particles as the organic-inorganic composite particles in a specific X-ray non-penetrating filler) in an amount required to impart X-ray non-penetrability, a decrease in the transparency of the hardened body cannot be avoided (see Comparative Examples 2 and 5 described later).

[0063] (2) Method for determining the full width at half maximum

[0064] The measurement of the FWHM can be determined by performing X-ray diffraction measurement on a powder sample that is the object of X-ray diffraction measurement. Specifically, by performing X-ray diffraction measurement on the powder sample in the range of २θ of 20° to 120° using an X-ray diffraction apparatus, an X-ray diffraction pattern (graph) with the horizontal axis being २θ (°) and the vertical axis being the diffraction intensity is obtained. Regarding the powder sample, it is preferable to use powder obtained by removing coarse particles by a conventional method, for example, using a sieve with a mesh of 100 μm.

[0065] Next, identify the peak in the X-ray diffraction pattern (graph) derived from the rare earth metal fluoride particles, and find the FWHM for the peak with the maximum intensity from among the multiple confirmed peaks. For example, taking the case where the material of the rare earth metal fluoride particles is YbF3 as a specific example, the peak with the maximum intensity appears as a peak derived from the (111) plane near २θ = 28.0°. Here, among the peaks observed near २θ = 28.0°, the peak width at 50% intensity (50% intensity) of the maximum intensity of the peak is obtained, and thus the FWHM is obtained. In addition, the peak width is obtained as an absolute value, which is the absolute value of the difference between the २θ value at one intersection and the २θ value at the other intersection, where the two intersections are: the convex peak line and a straight line parallel to the horizontal axis of the X-ray diffraction pattern (graph) and located at the 50% intensity position (unit deg [°]).

[0066] Regarding the full width at half maximum (FWHM) of the crystalline rare earth metal fluoride particles in the organic-inorganic composite particles (particle matrix) that constitute a specific X-ray non-penetrating filler, it can be confirmed based on the X-ray diffraction pattern obtained by powder X-ray diffraction measurement of the powder sample composed of the particle matrix. In addition, regarding the specific X-ray non-penetrating filler obtained by the manufacturing method described later, the FWHM of the crystalline rare earth metal fluoride particles in the particle matrix (since the crystallinity of the secondary raw material powder does not change or substantially does not change during the mixing or pulverization process in the preparation of the raw material composition) can also be confirmed based on the X-ray diffraction pattern obtained by powder X-ray diffraction measurement of the powder sample composed of the secondary raw material powder. Further, the FWHM of the crystalline rare earth metal fluoride particles in the specific X-ray non-penetrating filler contained in the dental hardenable composition of the present invention can also be confirmed based on the X-ray diffraction pattern obtained by powder X-ray diffraction measurement of the powder sample containing the organic-inorganic composite particles separated from these hardenable compositions or the powder sample obtained from the hardened body of these hardenable compositions.

[0067] (3) Organic-inorganic composite particles (particle matrix)

[0068] Regarding the rare earth metal fluoride particles contained in the organic-inorganic composite particles (particle matrix), as long as the FWHM is 0.3° or more, the material is not particularly limited, and known rare earth metal fluoride particles can be appropriately used. When used for various purposes, as the material of the rare earth metal fluoride particles, for example, lanthanum fluoride (LaF3), cerium fluoride (CeF3), or ytterbium fluoride (YbF3) is preferably used, and ytterbium fluoride (YbF3) is more preferably used.

[0069] In addition, when using a specific X-ray non-penetrating filler for dental applications, from the viewpoint of easily ensuring a hue or safety suitable for dental applications, the material of the rare earth metal fluoride particles is preferably lanthanum fluoride (LaF3), cerium fluoride (CeF3), or ytterbium fluoride (YbF3). Further, from the viewpoint of ensuring X-ray non-penetration, ytterbium fluoride (YbF3) is particularly preferred.

[0070] The resin material of the resin matrix constituting the organic-inorganic composite particles (particle matrix) is not particularly limited, and known resin materials can be appropriately selected. For example, (meth)acrylic resins or polyaryletherketone resins can be mentioned. In addition, in the present application specification, the (meth)acrylic resin means that, as the polymerizable monomer used in the polymerization of the (meth)acrylic resin, A polymer formed only by polymerizing (meth)acrylate monomers, or <ii>In the case of two or more polymerizable monomers containing (meth)acrylate monomers, a polymer in which the proportion of (meth)acrylate monomers in all polymerizable monomers is 50 mol% or more.

[0071] In addition, in specific X-ray non-penetrating fillers, as a preferred combination of materials constituting the organic-inorganic composite particles (particle main body), a combination of (Group A1) and (Group B) can be cited. Among them, (Group A1) the material of rare earth metal fluoride particles is selected from the group consisting of lanthanum fluoride (LaF3), cerium fluoride (CeF3), and ytterbium fluoride (YbF3), and (Group B) the resin material constituting the resin matrix is a (meth)acrylic resin; as a particularly preferred combination, a combination of (Group A2) and (Group B) can be cited. Among them, (Group A2) the material of rare earth metal fluoride particles is selected from the group consisting of ytterbium fluoride (YbF3), and (Group B) the resin material constituting the resin matrix is a (meth)acrylic resin.

[0072] In addition, the content ratio of rare earth metal fluoride particles contained in the organic-inorganic composite particles (particle main body) is not particularly limited. Based on the total mass of the organic-inorganic composite particles, it is preferably 60 mass% or more, more preferably 70 mass% or more. On the other hand, the upper limit value of the content ratio is preferably 90 mass% or less, more preferably 80 mass% or less.

[0073] The average particle size of the organic-inorganic composite particles (particle main body) is not particularly limited. From the viewpoint of more balanced consideration of X-ray contrast and mechanical strength, it is preferably 22 to 70 μm, more preferably 24 to 55 μm. In addition, when ensuring mechanical strength is more important than X-ray contrast, the average particle size is preferably 3 to 38 μm, more preferably 8 to 25 μm. In contrast, when ensuring X-ray contrast is more important than mechanical strength, the average particle size is preferably 38 μm or more, more preferably 70 μm or more. In addition, the lower limit value is not particularly limited, but from the viewpoint of ensuring a certain degree of mechanical strength, it is preferably 110 μm or less.

[0074] 2. Manufacturing method of specific X-ray non-penetrating filler

[0075] Regarding the manufacturing method of the specific X-ray non-penetrating filler (also referred to as this manufacturing method), as long as it is a method of granulating organic-inorganic composite particles using rare earth metal fluoride particles with a full width at half maximum of 0.3° or more and a resin material or a resin material precursor (polymerizable monomer, etc.), there is no particular limitation, and a known manufacturing method of organic-inorganic composite particles can be appropriately used.

[0076] However, the full width at half maximum (FWHM) of rare earth metal fluorides generally used as X-ray non-penetrating materials or commercially available rare earth metal fluoride powders obtainable as raw material powders is usually less than 0.3° (specifically around 0.17° to 0.27°). Therefore, based on the reason that specific X-ray non-penetrating fillers can be effectively manufactured using such rare earth metal fluoride powders, this manufacturing method is preferably adopted.

[0077] That is, a manufacturing method including a secondary raw material powder preparation step, a hardening step, and a pulverization step is preferably adopted.

[0078] Among them, in the secondary raw material powder preparation step, mechanochemical treatment is performed on a primary raw material powder composed of a powder mainly composed of crystalline rare earth metal fluoride particles with a full width at half maximum of less than 0.3°, to obtain a secondary raw material powder composed of a powder mainly composed of rare earth metal fluoride particles with a full width at half maximum of 0.3° or more.

[0079] In the hardening step, a hardened product is obtained by hardening a raw material composition, where the raw material composition is obtained by mixing a polymerizable monomer as the raw material of the above resin matrix and the above secondary raw material powder.

[0080] In the pulverization step, the above hardened product is pulverized.

[0081] Hereinafter, each step of the above manufacturing method will be described. It should be noted that a step in which the hardening step and the pulverization step are combined is sometimes referred to as a granulation step.

[0082] (1) Secondary raw material powder preparation step

[0083] In the secondary raw material powder preparation step, mechanochemical treatment is performed on a primary raw material powder composed of a powder mainly composed of crystalline rare earth metal fluoride particles with a full width at half maximum of less than 0.3° to obtain a secondary raw material powder composed of a powder mainly composed of rare earth metal fluoride particles with a full width at half maximum of 0.3° or more. It should be noted that "as the main component" here means that other substances other than trace amounts of crystalline rare earth metal fluoride particles may be contained. For example, surface treatment agents or additives physically attached or chemically bonded to the surface of crystalline rare earth metal fluoride particles, and the full width at half maximum of the crystalline rare earth metal fluoride particles must be less than 0.3° or 0.3° or more.

[0084] As the primary raw material powder, rare earth metal fluorides that are usually used as X-ray non-penetrating materials can be used without particular limitation, or commercially available rare earth metal fluoride powders with a full width at half maximum (FWHM) of less than 0.3° (specifically around 0.17° to 0.27°) that can be obtained as raw material powders. For the primary raw material powder, X-ray diffraction measurement is preferably performed as needed, and the FWHM is measured in advance.

[0085] In addition, as the crystalline rare earth metal fluoride particles used as the primary raw material powder, particles with a surface coated with nano-silica or the like, or particles with a surface treated with a silane coupling agent or the like can also be used.

[0086] In the mechanochemical treatment in the secondary raw material powder preparation process, depending on the treatment conditions, if the treatment time is extended, sometimes the particles contained in the raw material powder are pulverized, and the secondary particles (aggregated particles) or primary particles are broken and the particle size becomes smaller. However, in the treatment time of about several hours, although the coarse aggregated particles are broken, the particle sizes of the primary particles or sub-micron level aggregated particles do not change significantly. Therefore, as the raw material powder, a powder with an average primary particle size of 1 to 500 nm measured by electron microscope observation is preferably used, and a powder of 5 to 300 nm is more preferably used. In addition, a powder with an average particle size of 0.1 to 0.6 μm measured by the laser diffraction scattering method capable of measuring the diameter of the aggregated particles is preferably used, and a powder of 0.1 to 0.3 μm is more preferably used. In addition, the average primary particle size is a value measured using a scanning electron microscope. Specifically, the powder is observed with an electron microscope at a magnification of 100,000 times, and the average primary particle size of 100 primary particles in the obtained observation image is used as the average primary particle size.

[0087] (2) Mechanochemical treatment

[0088] Mechanochemical treatment refers to a treatment that imparts mechanical energy to the raw material powder. Specifically, it refers to at least one treatment selected from the group consisting of mechanical grinding, pulverization, and dispersion. From the viewpoint of easily and reliably controlling the full width at half maximum (FWHM), which is the degree of crystal integrity of the rare earth metal fluoride particles after mechanochemical treatment, to a desired value, as the method of mechanochemical treatment, a wet method is preferably adopted, and a treatment method using a wet bead mill is particularly preferred. When mechanochemical treatment is carried out by the wet method, as the medium, a solvent such as water or ethanol, or a polymerizable monomer or the like can be used, but from the viewpoint of the dispersibility of the raw material powder, etc., a medium that is liquid at normal temperature (15°C to 25°C) is preferred.

[0089] Hereinafter, the mechanochemical treatment using a wet bead mill will be described in detail.

[0090] In the mechanochemical treatment using a wet bead mill, a slurry obtained by mixing a raw material powder to be subjected to mechanochemical treatment and a medium is brought into contact with a medium (beads) imparted with motion by stirring, vibration, or the like. By doing so, the raw material powder is pulverized or broken. Examples of the material of the beads used as the medium include glass, alumina, zircon, zirconia, steel, and resin. From the viewpoint of excellent abrasion resistance and less contamination, alumina or zirconia is preferred. Regarding the size of the beads used, it may be selected according to the particle diameter of the X-ray non-penetrating filler as the target, and there is no particular limitation. Usually, beads having a diameter of 0.01 mm to 0.5 mm are preferably used. In addition, beads having such a diameter are also preferred in terms of obtaining an X-ray non-penetrating filler having a particle diameter preferred when added to a dental hardenable composition.

[0091] According to its working mode, there are types such as a batch type in which the slurry and beads are directly put into the device for treatment, a circulation type in which the slurry is circulated between the container and the device, and a pass type in which the slurry passes through the device a specified number of times in a wet bead mill. These working modes can be selected according to the amount of the raw material powder used in the mechanochemical treatment. For reasons of good productivity and the ability to process a relatively large amount of raw material powder, a circulation type bead mill is preferably used.

[0092] According to the working mode such as the above-mentioned circulation type or pass type, it is necessary to separate the slurry and the beads when performing the mechanochemical treatment. Examples of the separation method of the beads include a slit type, a screen type, and a centrifugal separation type. These separation methods of the beads may be selected according to the particle diameter of the beads used, and any method can be used without particular limitation. The concentration of the slurry used for the mechanochemical treatment is preferably 50 parts by mass or less of the raw material powder relative to 100 parts by mass of the medium. If the raw material powder in the slurry exceeds 50 parts by mass, the viscosity of the slurry becomes high, and sometimes it is difficult to perform the mechanochemical treatment.

[0093] By adding a dispersant to the slurry, an increase in the slurry viscosity can be suppressed. Therefore, by adding a dispersant to the slurry, mechanochemical treatment can be performed on a slurry with a higher concentration. As the dispersant to be used, as long as it is a known surfactant, it can be used without particular limitation. For example, nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and their polymeric surfactants can be cited. Specifically, glycerol fatty acid esters and their alkylene glycol adducts, aliphatic monocarboxylates, alkylamine salts, and alkyl betaines can be cited. When mixing and granulating the mechanochemically treated raw material powder and the raw material constituting the resin matrix (resin matrix raw material), from the viewpoint of dispersibility during mixing, a cationic surfactant is preferably used.

[0094] Depending on conditions such as the working method of the wet bead mill used, the diameter of the beads, the full width at half maximum of the raw material powder, and the slurry concentration, the mechanochemical treatment conditions vary. Regarding these conditions, a preliminary experiment can be conducted using the device actually implementing the mechanochemical treatment, and after confirming the full width at half maximum of the raw material powder after mechanochemical treatment with respect to the mechanochemical treatment time, appropriate selection can be made. In addition, in the case of implementing mechanochemical treatment, the slurry during mechanochemical treatment can be appropriately sampled as needed, and the full width at half maximum can be appropriately confirmed. By doing so, a secondary raw material powder after mechanochemical treatment with a desired full width at half maximum can be obtained.

[0095] For the secondary raw material powder (mechanochemically treated rare earth metal fluoride particles) whose full width at half maximum is adjusted to 0.3° or more by mechanochemical treatment, post-treatment processes such as concentration, drying, or filtration are usually appropriately performed to obtain a raw material powder for granulation of organic-inorganic composite particles (raw material powder for granulation). It should be noted that when a polymerizable monomer is used as the medium during mechanochemical treatment, the post-treatment process can also be omitted. In this case, depending on the need, after adding other components such as a polymerization initiator to the slurry after mechanochemical treatment (a composition containing the raw material powder and the polymerizable monomer), organic-inorganic composite particles can be formed. In addition, in order to improve the affinity with the resin matrix raw material used in the granulation of organic-inorganic composite particles, the raw material powder that has undergone the mechanochemical treatment process and the post-treatment process can be surface-treated. As the surface treatment agent used in the surface treatment, compounds such as commonly used silane coupling agents or titanate coupling agents can be used.

[0096] (3) Granulation process

[0097] In the granulation of the organic-inorganic composite particles, a granulation step is carried out using a secondary raw material powder and a resin matrix raw material. The full width at half maximum (FWHM) of the secondary raw material powder may be 0.3° or more, but from the viewpoint of more stably and reliably obtaining the X-ray non-penetrating filler of the present embodiment, it is preferably 0.35° or more, and more preferably 0.4° or more. The upper limit value of the FWHM of the secondary raw material powder is not particularly limited and can be appropriately selected according to the target value of the FWHM of the X-ray non-penetrating filler to be manufactured. However, in practical use, it is preferably 40° or less, and more preferably 1° or less.

[0098] In this manufacturing method, as the granulation step of the organic-inorganic composite particles, a hardening step and a pulverization step are carried out. In the hardening step, the raw material composition is hardened to obtain a hardened product, where the raw material composition is obtained by mixing a polymerizable monomer, which is a resin matrix raw material of the organic-inorganic composite particles, and the above secondary raw material powder. In the pulverization step, the above hardened product is pulverized.

[0099] As the polymerizable monomer that is the resin matrix raw material of the organic-inorganic composite particles, known polymerizable monomers such as radical polymerizable monomers can be used, and (meth)acrylate monomers are particularly preferably used. In addition, in the granulation raw material composition, various polymerization initiators such as chemical polymerization initiators, photopolymerization initiators, and thermal polymerization initiators, or other additives can be used as needed. It should be noted that as specific examples of the polymerizable monomer, polymerization initiator, and other additives, the same substances as those used in the curable composition of the present embodiment described later can be used. It should be noted that the resin matrix constituting the organic-inorganic composite particles (particle main body) obtained by the first granulation method is composed of a material obtained by hardening the remaining components (mainly polymerizable monomers) after removing the raw material powder from the granulation raw material composition.

[0100] It should be noted that the refractive index n of the crystalline rare earth metal fluoride particles used as the first and second raw material powders with respect to the sodium D line at 25°C X , is generally in the range of 1.50 to 1.65, and in the case of crystalline ytterbium fluoride particles, it is 1.55. Therefore, the refractive index n of the resin material, which is the main component of the resin matrix constituting the organic-inorganic composite particles (particle main body), with respect to the sodium D line at 25°C (F-MX) is preferably 1.45 to 1.60. Here, "the resin material that is the main component of the resin matrix" refers to the hardened product of the polymerizable monomer (the hardened product of a composition composed only of the polymerizable monomer or the hardened product of a composition composed of the polymerizable monomer and a small amount of polymerization initiator). When n X and n (F-MX) can take approximate values as described above, the transparency improvement of the curable composition using the X-ray non-penetrating filler becomes easier.

[0101] From such a perspective, it is preferable to satisfy the following formula (1A), more preferably to satisfy the following formula (2A), and further preferably to satisfy the following formula (3A).

[0102] Formula (1A) -0.02 ≤ (n X -n (F-MX) ) ≤ 0.1

[0103] Formula (2A) 0.01 ≤ (n X -n (F-MX) ) ≤ 0.07

[0104] Formula (3A) 0 ≤ (n X -n (F-MX) ) ≤ 0.05

[0105] In addition, in the pulverization process, a known pulverization method using a ball mill or the like can be utilized. In addition, for the obtained organic-inorganic composite particles (particle main body) after pulverization, various surface treatments, coating treatments, admixture treatments, etc. can be carried out as needed.

[0106] In addition, in the case of using a thermoplastic resin such as a polyaryletherketone resin as the resin matrix of the organic-inorganic composite particles, a granulation method including at least a melt mixing process and a pulverization process is adopted to manufacture the organic-inorganic composite particles, and they are used as specific X-ray non-penetrating fillers. Among them, in the melt mixing process, a granulation raw material composition containing at least a secondary raw material powder and a thermoplastic resin is melt mixed to obtain a melt mixture, and in the pulverization process, the solidified product obtained by cooling and solidifying the melt mixture is pulverized.

[0107] At this time, in the granulation raw material composition, other additives can also be used as needed. It should be noted that as a specific example of other additives, the same additives as those used in the dental hardenable composition of the present invention described later can be utilized. In addition, as the melt mixing method of the granulation raw material composition, a known melt mixing method can be used. For example, the melt mixing method disclosed in the international publication No. 2013 / 88921 can be used. It should be noted that the resin matrix constituting the organic-inorganic composite particles (particle main body) obtained by the second granulation method is composed of the remaining components (mainly thermoplastic resin) after removing the raw material powder from the granulation raw material composition.

[0108] 3. Dental hardenable composition of the present invention

[0109] (1) Outline of the dental hardenable composition of the present invention

[0110] The main feature of the dental hardening composition of the present invention is that a specified amount of a specific X-ray non-penetrating filler is mixed in a dental hardening composition (existing structural color system dental hardening composition) used as the existing known structural color system CR.

[0111] Here, the existing structural color system dental hardening composition refers to a dental hardening composition that contains a specified amount of a polymerizable monomer, an inorganic filler, and a polymerization initiator as described in the prior art, and is a dental hardening composition that, by using a filler containing spherical inorganic particles having a specific average particle size and particle size distribution, that is, one or more "same particle size spherical particle groups" (G-PID), makes the refractive index of the spherical inorganic particles greater than the refractive index of the resin part that becomes the matrix during hardening. Specifically, when the amount of the polymerizable monomer contained in the dental hardening composition is set to 100 parts by mass, the following conditions 1 to 3 are satisfied, so that a dental hardening composition that exhibits a structural color of a specified hue by light interference or scattering, etc., and the specified hue does not depend on the incident angle of light.

[0112] Condition 1: It contains one or more "same particle size spherical particle groups" (G-PID) and a polymerization initiator in a total amount of 10 to 1500 parts by mass. Among them, the one or more "same particle size spherical particle groups" (G-PID) are composed of an aggregate of inorganic spherical particles having a specified average primary particle size in the range of 100 to 1000 nm. Each inorganic spherical particle constituting the aggregate is substantially composed of the same substance, and in the number-based particle size distribution of the aggregate, more than 90% of all the particle numbers exist within the range of ±5% of the specified average primary particle size.

[0113] Condition 2: When the number of the one or more "same particle size spherical particle groups" is set to a, each "same particle size spherical particle group" is represented by G-PID m (where m is 1 when a is 1, and m is a natural number from 1 to a when a is 2 or more). When a is 2 or more, the substances of the respective particles constituting each G-PID m can be different from each other. In this case, the average primary particle sizes of the respective G-PID m differ by 25 nm or more from each other.

[0114] Condition 3: When the refractive index of the hardened body of the polymerizable monomer with respect to the sodium D line at 25 °C is set to n (MX) and the refractive index of the inorganic spherical particles constituting each G-PID m with respect to the sodium D line at 25 °C is set to n (G-PIDm) at any n (G-PIDm) all hold for n (MX) < n (G-PIDm) relationship.

[0115] Moreover, the dental curable composition of the present invention is characterized in that, in the above-described conventional structural color system dental curable composition, the following conditions 4 and 5 are further satisfied.

[0116] Condition 4: Specific X-ray non-penetrating filler: Based on the total mass conversion of the crystalline rare earth fluoride metal particles having a full width at half maximum of 0.3° or more contained in the X-ray non-penetrating filler, 1 to 100 parts by mass of a specific X-ray non-penetrating filler is further contained.

[0117] Condition 5: The refractive index n of the cured product of the polymerizable monomer with respect to the sodium D line at 25°C (MX) and the refractive index n of the resin material of the resin matrix constituting the organic-inorganic composite particles with respect to the sodium D line at 25°C (F-MX) The absolute value of the difference |n (MX) - n (F-MX) | is 0 to 0.1, wherein the organic-inorganic composite particles constitute the X-ray non-penetrating filler.

[0118] That is, by further satisfying these conditions 4 and 5, high X-ray non-penetrability can be imparted to the cured body without impairing the excellent properties of the conventional structural color system dental curable composition. The excellent properties are as follows: When used as CR, (i) since no dye substance or pigment substance is used, it is difficult to cause the problem of color change over time after treatment. (ii) Depending on the average particle diameter of the spherical inorganic particles used, a specific structural color that does not depend on the incident angle of light is exhibited. In particular, when spherical inorganic particles with an average primary particle diameter of 230 to 350 nm are used, it can be colored into yellow to red, which is the same color as dentin. Moreover, (iii) since the cured body has moderate transparency, it is easy to match the color of the tooth to be restored. Thus, without the need for complicated shade taking or color selection of composite resins, a composite resin can be used to repair teeth to be restored with a wide range of colors to an appearance close to that of natural teeth.

[0119] The dental curable composition of the present invention exhibits these characteristics because its cured form exhibits structural color development that is substantially equivalent to that of a cured form of a conventional structural color dental curable composition (also referred to as a base conventional structural color dental curable composition) that does not contain specific X-ray opaque fillers or fillers that adversely affect structural color development. This property can be confirmed by comparing the spectral reflectance ratio (SR1 / SR2) of the cured form of the dental curable composition of the present invention with that of the cured form of the base conventional structural color dental curable composition. Here, SR1 and SR2 refer to the maximum value (SR1) of the spectral reflectance in the wavelength range of 600 nm to 750 nm (yellow to red region), and the maximum value (SR2) of the spectral reflectance in the wavelength range of 400 nm to 500 nm (blue region), in a spectral reflectance curve obtained by measuring a cured product having a thickness of 1 mm obtained by curing a dental curable composition against a black background using a colorimeter. The smaller the spectral reflectance ratio, the more bluish the structural color (colored light) of the cured product, and the larger the spectral reflectance ratio, the more reddish the structural color (colored light) of the cured product.

[0120] In conventional structural color-based dental curable compositions, the average primary particle size of the mixed G-PID is typically controlled to achieve a desired structural color (desired spectral reflectance ratio: SR1 / SR2 ratio) in the cured product. For example, to achieve excellent color harmony when used to repair dentin or cavities formed from enamel to dentin, the spectral reflectance ratio is typically in the range of 0.9 to 1.5. This is because a spectral reflectance ratio of less than 0.8 weakens the yellow-red structural color (colored light), making it difficult to achieve color harmony with natural teeth with yellow-red hues, i.e., restored teeth containing dentin. Furthermore, a spectral reflectance ratio exceeding 2.0 results in a yellow-red hue in the cured product that is too strong compared to natural teeth, making it difficult to achieve good color harmony.

[0121] The dental curable composition of the present invention, which satisfies the above-mentioned conditions 4 and 5, is characterized by the fact that a specific X-ray opaque filler is mixed with a basic conventional structural color-based dental curable composition to make the cured product exhibit high X-ray opacity, but the spectral reflectance ratio is not easily changed, and the spectral reflectance ratio can be maintained at a value of, for example, 0.9 or higher even without the addition of a colorant such as a pigment.

[0122] In addition, regarding the supplementary explanation of the above item (iii), by using the dental hardenable composition of the present invention, for example, a hardened body with a contrast ratio C of 0.20 to 0.50 can be obtained, preferably a hardened body with a contrast ratio of 0.25 to 0.45. The contrast ratio C here is an index of the transparency of the hardened body of the dental hardenable composition, and it is the Y value measured with a color difference meter on a black background for a hardened body specimen with a thickness of 1 mm, namely Y b and the Y value measured on a white background, namely Y W ratio Y b / Y W defined. The smaller the contrast ratio, the higher the transparency.

[0123] When the contrast ratio of the hardened body of the dental hardenable composition of the present invention is less than 0.20, the brightness (color depth) of the hardened body in the filling part becomes lower, the transmitted light in the filling part is strong, and the colored light emitted from the hardened body becomes weak. Therefore, it can be considered that when filled into a deep cavity (such as a Class IV cavity), it is difficult to obtain the hue coordination as the effect of the present invention. On the other hand, when the contrast ratio of the hardened body exceeds 0.50, the brightness of the hardened body becomes higher, and light is difficult to penetrate to the restoration serving as the base. Therefore, the reflected light on the surface of the filling part is strong, and the colored light emitted from the hardened body becomes weak. From this, it can be considered that it is difficult to obtain the hue coordination as the effect of the present invention. That is, in order to have excellent hue coordination regardless of the depth of the cavity to be restored, the contrast ratio C of the hardened body of the hardenable composition is in the range of 0.20 to 0.50, more preferably in the range of 0.20 to 0.45.

[0124] The reason for obtaining such an effect is not necessarily clear. In addition, the present invention is not limited by any logic, but the inventors of the present application infer the following reasons. That is, regarding the fact that high X-ray contrast can be obtained with a small mixing amount of rare earth metal fluoride particles, it can be considered as follows: In the case of directly mixing rare earth metal fluoride particles, since each particle with weak (small) X-ray non-penetrability is uniformly dispersed, the overall X-ray non-penetrability becomes blurred. In contrast, by mixing as organic-inorganic composite particles, it can be uniformly dispersed (scattered) as a whole in the "region where the density of rare earth metal fluoride particles is locally high" (the region with locally high X-ray non-penetrability), so that it can be clearly recognized during image observation. In addition, regarding the fact that there is no adverse effect on the manifestation of the desired structural color when mixed in the structural color CR, it can be considered as follows: In the case of directly mixing rare earth metal fluoride particles, the particles enter between the particles of the same particle size spherical particle group (G-PID) that forms an ideal periodic structure, thus disrupting the periodic structure. On the other hand, by using rare earth metal fluoride particles as organic-inorganic composite particles, compared with the case of directly mixing rare earth metal fluoride particles, the absolute number of particles decreases, and the frequency of disrupting the periodic structure of G-PID decreases, or, through organic-inorganic compositeization, the particle size increases, making it difficult to enter between the periodic structures of G-PID. That is, it can be considered that by using rare earth metal fluoride particles as organic-inorganic composite particles, it is difficult to disrupt the periodic structure formed by G-PID, and thus no adverse effect is brought to the manifestation of the desired structural color.

[0125] (2) Regarding the existing structural color dental hardenable composition and the components of the dental hardenable composition, etc.

[0126] Regarding each component or mixing amount, etc. of the dental hardenable composition constituting the present invention, except for the point of mixing a specified amount of a specific X-ray non-penetrating filler, it is basically the same as the components and mixing amounts, etc. in the existing structural color dental hardenable composition disclosed in Patent Documents 1 to 2. Therefore, here, on the basis of a simple description of these, the dental hardenable composition of the present invention will be described.

[0127] (2-1) Polymerizable monomer

[0128] As the existing structural color dental hardenable composition and the polymerizable monomer used in the dental hardenable composition, the polymerizable monomers that can be used in the existing dental hardenable composition can be used without particular limitation, and (meth)acrylate monomers are preferably used. Specific examples of the (meth)acrylate monomers that can be preferably used include: methyl (meth)acrylate, glycidyl (meth)acrylate, 2-cyano(methyl)acrylate, polyethylene glycol mono(meth)acrylate, allyl (meth)acrylate, 2-hydroxyethyl mono(meth)acrylate, 2,2,3,3-tetrafluoropropyl methacrylate (TFM), ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate (3G), nonaethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, 2,2-bis[4-(meth)acryloyloxyethoxyphenyl]propane, 2,2-bis[4-(meth)acryloyloxypolyethoxyphenyl]propane (D-2,6E), 2,2-bis{4-[3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl}propane, 1,4-butanediol di(meth)acrylate, 1,3-hexanediol di(meth)acrylate, 1,6-bis(methacrylethyloxycarbonylamino)-2,2,4-trimethylhexane (UDMA), trimethylolpropane di(meth)acrylate, etc. These polymerizable monomers can be used in combination of two or more as appropriate.

[0129] Among these polymerizable monomers, difunctional to tetrafunctional polymerizable monomers are preferred for reasons such as high polymerizability or particularly high mechanical strength of the hardened body. From the viewpoint of the transparency of the hardened body of the hardenable composition, ethylene glycol di(meth)acrylate, 2,2-bis[4-(meth)acryloyloxyethoxyphenyl]propane, 2,2-bis{4-[3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl}propane, 1,6-bis(methacrylethyloxycarbonylamino)-2,2,4-trimethylhexane (UDMA), any one of them, or a combination of two or more of these polymerizable monomers is more preferred.

[0130] From the viewpoint of easily satisfying the above-mentioned condition 3, that is, from the viewpoint of easily satisfying the above-mentioned conditions related to the refractive index, it is preferable to set the types and amounts of the polymerizable monomers so that the refractive index of the polymerizable monomer composition (mixture) with respect to the sodium D line at 25 °C is in the range of 1.38 to 1.55. That is, in the case of using a silica-titanium group element oxide-based composite oxide whose refractive index is easily adjusted as the inorganic spherical particles, the refractive index with respect to the sodium D line at 25 °C becomes in the range of about 1.45 to 1.58 according to the content of the silica component. By setting the refractive index of the polymerizable monomer composition in the range of 1.38 to 1.55, the refractive index of the obtained hardened body can be adjusted to the range of approximately 1.40 to 1.57, thereby easily satisfying the above-mentioned conditions. In addition, the refractive index of the polymerizable monomer or the hardened body of the polymerizable monomer can be measured using an Abbe refractometer at 25 °C.

[0131] In addition, in the dental hardenable composition of the present invention, from the viewpoint of not reducing the transparency of the hardened body of the dental hardenable composition, |n (MX) -n (F-MX) | needs to be 0 to 0.1, preferably 0 to 0.07, more preferably 0 to 0.05, and particularly preferably 0 to 0.035. In order to adjust the refractive index in this way, for example, as the polymerizable monomers used in the hardenable composition and the polymerizable monomers used in the production of the resin material constituting the resin matrix of the organic-inorganic composite particles, it is preferable to use the same type of polymerizable monomer. In addition, when two or more polymerizable monomers are used in combination, it is preferable that their mixing ratios are also the same or approximate.

[0132] (2-2) Monodisperse spherical particle group: G-PID

[0133] The existing structural color dental hardenable composition and the monodisperse spherical particle group G-PID used in the dental hardenable composition refer to the following aggregate: it is composed of an aggregate of inorganic spherical particles having a specified average primary particle size in the range of 100 nm or more and 1000 nm or less (100 to 1000 nm), each inorganic spherical particle constituting the aggregate is substantially composed of the same substance, and in the number-based particle size distribution of the aggregate, more than 90% of the total number of particles exists within the range of ±5% of the above-mentioned specified average primary particle size.

[0134] The average primary particle diameter of the inorganic spherical particles referred to herein means: taking a photograph of G-PID using a scanning electron microscope, selecting 100 or more particles observed in a unit visual field of the photograph, and obtaining the average value by finding the respective primary particle diameters (maximum diameters). In addition, regarding spherical shape, a roughly spherical shape is sufficient, and it does not necessarily have to be a complete sphere. Taking a photograph of G-PID using a scanning electron microscope, measuring the maximum diameter of each particle (100 or more) in its unit visual field, and a spherical shape with an average uniformity obtained by dividing the particle diameter in the direction orthogonal to the maximum diameter by the maximum diameter of 0.6 or more, more preferably 0.8 or more is sufficient.

[0135] In the existing structured color dental hardenable composition and the hardened body of the dental hardenable composition, each constituent particle of G-PID has a specific short-range ordered structure and is dispersed in the resin matrix. Thus, diffraction interference occurs according to the Bragg condition, and light of a specific wavelength is emphasized, thereby generating colored light (exhibiting structural color) with a hue corresponding to the average primary particle diameter. That is, in order to exhibit structural color, 90% (by number) or more of the inorganic spherical particles constituting G-PID need to exist within the range of plus or minus 5% of the average primary particle diameter. That is, when the ratio (%) of "the number of particles existing within the range of plus or minus 5% of the average primary particle diameter" to "the total number of particles constituting G-PID" is set as the "5% particle content rate", the 5% particle content rate needs to be 90% or more. In addition, in order to exhibit structural color with a specific hue in a wide range of blue-yellow-red systems, the average primary particle diameter of the inorganic spherical particles constituting G-PID needs to be in the range of 100 to 1000 nm. If spherical particles with an average primary particle diameter less than 100 nm are used, it is difficult to generate an interference phenomenon of visible light and it is also difficult to exhibit structural color. On the other hand, if spherical particles larger than 1000 nm are used, although the appearance of a light interference phenomenon can be expected, due to the sedimentation of the spherical particles or the reduction of the abrasiveness of the hardened body, it is not preferred.

[0136] When the average primary particle size is 230 to 800 nm, structural colors (colored light) in the yellow to red range are likely to appear. When the average primary particle size is less than 150 to 230 nm, structural colors (colored light) in the blue range are likely to appear. For the reason of showing structural colors (colored light) in the yellow to red range, which are preferred for dental filling and restorative materials, the average primary particle size of G-PID is preferably 230 - 800 nm, more preferably 240 - 500 nm, and particularly preferably 260 - 350 nm. When G-PID with an average primary particle size in the range of 230 to 260 nm is used, the resulting colored light is yellowish, which is useful for the restoration of teeth in the B series (reddish yellow) category of the dental shade guide (VITAClassical, manufactured by VITA, Germany), especially for the restoration of cavities formed from enamel to dentin. In addition, when G-PID with an average primary particle size in the range of 260 to 350 nm is used, the resulting colored light is reddish, which is useful for the restoration of teeth in the A series (tea red) category of the dental shade guide (VITAClassical, manufactured by VITA, Germany), especially for the restoration of cavities formed from enamel to dentin. Since the hue of dentin is mostly such a reddish color, in the form of only using G-PID in the range of 260 to 350 nm, the coordination for the restoration of teeth with various hues becomes widely better, so it is the most preferred. On the other hand, when only G-PID with a particle size less than 150 to 230 nm is used, as described above, the resulting colored light is blueish. For cavities formed from enamel to dentin, the color coordination with dentin is likely to become poor, but it is useful for the restoration of enamel, especially for the restoration of the incisal edge.

[0137] The existing structural color-based dental hardenable composition and the G-PID contained in the dental hardenable composition can be one kind or multiple kinds. The number a of the contained G-PID is preferably 1 to 5, particularly preferably 1 to 3, and most preferably 1 or 2. Among them, when multiple G-PIDs are contained in the inorganic particles, the average primary particle sizes of the respective G-PIDs need to differ by 25 nm or more from each other. That is, when the number of G-PIDs contained in the above inorganic particles is set as a (for example, 3), each G-PID m (where m is 1 when a is 1, and m is a natural number from 1 to a when a is 2 or more) is expressed, the substances of the respective particles constituting each G-PID m (for example, G-PID1, G-PID2, and G-PID3 when a = 3) can be different from each other. When the respective G-PIDs in this case m The average primary particle diameters are respectively set as d m When m they need to differ by more than 25 nm respectively (for example, when a = 3, |d1 - d2| ≥ 25 nm, |d2 - d3| ≥ 25 nm, and of course |d1 - d3| ≥ 25 nm). By satisfying this condition, for example, it can be considered that each G-PID is dispersed in the form of an aggregate formed by the aggregation of no more than about 20 inorganic spherical particles with a very loose binding force, etc., and thus can have a short-range ordered structure capable of exhibiting structural color and be dispersed in each G-PID. As a result, a unique structural color (corresponding to the average primary particle diameter) can be exhibited for each G-PID. In contrast, when this condition is not satisfied, it can be considered that the particle size distribution of the whole inorganic spherical particles becomes broad, and the inorganic spherical particles constituting each G-PID may displace and disperse each other, resulting in the same phenomenon as when using an aggregate of single inorganic spherical particles that does not satisfy the above particle size distribution condition of the number criterion, and thus it is difficult to exhibit structural color. When multiple G-PIDs are used, the average primary particle diameter d of each G-PID m is preferably different from each other by more than 30 nm, and more preferably by more than 40 nm. m

[0138] In addition, in the case of the existing structural color series dental hardenable composition and the dental hardenable composition containing a variety of G-PIDs, each G-PID has an extremely sharp particle size distribution, and there is a difference in the average primary particle diameter as described above. Therefore, the particle size distributions of each G-PID are not easily overlapped, and even in the case of partial overlap, the particle size distributions of each G-PID can be confirmed. That is, regarding the particle size distribution of the inorganic particles contained in the composite material of the present embodiment, in the range of 100 to 1000 nm, there are independent peaks with the same number as the number of G-PIDs contained in the composite material. Even in the case of partial overlap of a part of each peak, by performing waveform processing, the average primary particle diameter and the number criterion particle size distribution of each G-PID can be confirmed. In addition, regarding the particle size distribution of the inorganic particles contained in the present invention, for example, it can also be confirmed by performing image processing on an electron micrograph of the inner surface of the composite material of the present embodiment.

[0139] Based on the reason that the above short-range ordered structure can be easily obtained from the dispersion state of the inorganic spherical particles, the G-PID is preferably a G-PID formed by the aggregation of inorganic spherical particles with an aggregate particle diameter. For example, the average aggregate particle diameter of the G-PID is preferably in the range of 5 to 200 μm, and more preferably in the range of 10 to 100 μm. In addition, the average aggregate particle diameter of the G-PID refers to the volume statistical median diameter obtained based on the measurement results of a particle size distribution analyzer using the laser diffraction-scattering method.​

[0140] (2-3) Inorganic spherical particles constituting the G-PID

[0141] As the inorganic spherical particles constituting the G-PID, as long as the aforementioned conditions for constituting the G-PID are satisfied, their material is not particularly limited. When exemplifying materials that can be preferably used, examples include materials composed of amorphous silica, silica-titanium group element oxide composite oxide particles (such as silica-zirconia, silica-titanium dioxide, etc.), quartz, alumina, barium glass, strontium glass, lanthanum glass, fluoroaluminosilicate glass, ytterbium fluoride, zirconia, titanium dioxide, colloidal silica, etc. Among them, from the viewpoint of easily adjusting the refractive index, particles composed of silica-titanium group element oxide composite oxides are preferably used.

[0142] Here, the silica-titanium group element oxide composite oxide particles refer to the composite oxides of silica and titanium group elements (Group 4 elements of the periodic table). The refractive index with respect to the sodium D line at 25 °C can be varied within a range of about 1.45 to 1.58 according to the content of the silica component. Specific examples of the silica-titanium group element oxide composite oxide particles include silica-titanium dioxide, silica-zirconia, silica-titanium dioxide-zirconia, etc., and silica-zirconia is preferably used. The composite ratio in silica-zirconia is not particularly limited. From the viewpoints of imparting sufficient X-ray non-penetrability and making the refractive index fall within the preferred range described below, it is preferred that the content of silica is 70 to 95 mol% and the content of titanium group element oxides is 5 to 30 mol%. In addition, if in a small amount, other metal oxides other than silica and titanium group element oxides are also allowed to be combined with these silica-titanium group element oxide composite oxide particles. Specifically, it may contain alkali metal oxides such as sodium oxide and lithium oxide within 10 mol%.

[0143] The manufacturing method of such silica-titanium group element oxide composite oxide particles is not particularly limited. However, in order to obtain spherical fillers, for example, the following so-called sol-gel method is preferably adopted, that is, a mixed solution containing a hydrolyzable organosilicon compound and a hydrolyzable organotitanium group metal compound is added to an alkaline solvent, and hydrolysis is carried out to precipitate the reaction product. The inorganic spherical particles formed from these silica-titanium group element oxide composite oxides are preferably surface-treated with a silane coupling agent such as γ-methacryloxyalkyltrimethoxysilane or hexamethyldisilazane.

[0144] (2-4) Relationship between the refractive index of the cured product of the polymerizable monomer and the refractive index of the inorganic spherical particles

[0145] In the conventional structural color dental curable composition and the dental curable composition of the present invention, when the refractive index of the "cured body of the polymerizable monomer" (specifically, the cured product of the composition composed of the polymerizable monomer and a small amount of polymerization initiator) corresponding to the resin matrix in the cured body of the dental curable composition at 25°C with respect to the sodium D line is set to n (MX) , will constitute the above G-PID m The refractive index of the inorganic spherical particles with respect to the sodium D line at 25°C is n (G-PIDm) When, for any n (G-PIDm) The following relationships need to be established.

[0146] n (MX ) <n (G-PIDm )

[0147] If the above relationship is not satisfied, even if the structural color is developed, the resin matrix of the cured dental curable composition easily scatters short-wavelength light, making it difficult to confirm the developed structural color. From the perspective of visibility or vividness of the developed structural color and color harmony when used as a dental filling and restorative material, n (G-PIDm) With n (MX) The difference Δn is preferably 0.001 or more and 0.1 or less, more preferably 0.002 or more and 0.1 or less, and most preferably 0.005 or more and 0.05 or less.

[0148] As described above, by setting the refractive index of the polymerizable monomer composition with respect to the sodium D line at 25° C. in the range of 1.38 to 1.55, the refractive index (n (MX) ) is in the range of 1.40 to 1.57. In addition, as described above, the refractive index (n) of the silica-titanium group element oxide composite oxide can be adjusted by changing the content of silica. (G-PIDm) ) varies in the range of about 1.45 to 1.58. Therefore, for example, by utilizing these relationships, Δn can be easily set to the above-mentioned preferred range.

[0149] (2-5) Optimal Mixed Form of G-PID

[0150] For the reason that the above-mentioned short-range ordered structure can be obtained more simply and reliably, it is preferable that at least a part of one or more spherical particle groups of the same particle size contains a spherical particle group of the same particle size and a resin having a refractive index smaller than that of the inorganic spherical particles constituting the spherical particle group of the same particle size with respect to the sodium D line at 25°C, and is mixed as an organic-inorganic composite filler that does not contain other spherical particle groups of the same particle size other than the above-mentioned spherical particle group of the same particle size (that is, an organic-inorganic composite filler containing only a single G-PID).

[0151] Here, the organic-inorganic composite filler refers to a powder composed of a composite in which inorganic fillers are dispersed in an (organic) resin matrix, or a filler composed of aggregates in which primary particles of inorganic fillers are firmly connected to each other by an (organic) resin. In the above-mentioned preferred form, for example, in the case of containing three G-PIDs with different average primary particle sizes, namely G-PID1, G-PID2, and G-PID3, all or part of at least one of them is mixed as an "organic-inorganic composite filler containing only a single G-PID". Assuming that all of G-PID1 is mixed as an organic-inorganic composite filler containing only G-PID1 (composite filler 1) in the curable composition, only G-PID1 is contained in the composite filler 1, and a short-range ordered structure showing the structural color of G-PID1 is achieved. Therefore, even in the composite material obtained by curing the curable composition, the structural color of G-PID1 is reliably shown.

[0152] From the viewpoint of expecting such an effect and further easily adjusting the viscosity of the curable composition, it is preferable that 10 to 90%, preferably 20 to 80%, more preferably 30 to 70% of each G-PID is mixed as an "organic-inorganic composite filler containing only a single G-PID". At this time, the refractive index of the resin matrix of the organic-inorganic composite filler with respect to the sodium D line at 25°C: n' (F-MX) needs to be smaller than the refractive index of the inorganic spherical particles with respect to the sodium D line at 25°C (n (G-PIDm) ). In addition, similar to the above n (MX) , n (G-PIDm) and the difference Δn' between n' (F-MX) are preferably in the same range as the above Δn. Further, for the reason that the transparency of the cured body of the dental curable composition is not easily reduced, the refractive index n (MX) of the cured body of the above-mentioned polymerizable monomer in the dental curable composition of the present invention having a structural color system (specifically, the cured product of a composition composed of a polymerizable monomer and a small amount of polymerization initiator) with respect to the sodium D line at 25°C (F-MX) and the above n' (MX) The absolute value of the difference |n (MX) -n' (F-MX) |It needs to be 0 to 0.1.

[0153] In addition, the mixing amount of the inorganic spherical particles in the organic-inorganic composite filler is preferably 30 to 95 mass%, particularly preferably 40 to 90 mass%. In addition, the average particle diameter is not particularly limited, but from the viewpoint of making the mechanical strength of the composite material or the workability of the curable composition good, the median diameter determined based on the measurement result of a particle size distribution analyzer using the laser diffraction-scattering method is preferably 2 to 100 μm, more preferably 5 to 50 μm, and further preferably 5 to 30 μm.

[0154] (2-6) Content of G-PID

[0155] The total content of G-PID in the conventional structured color dental curable composition and the structured color dental curable composition of the present invention is 10 to 1500 parts by mass relative to 100 parts by mass of the polymerizable monomer. Based on the reason that the obtained composite material has moderate transparency and a high structural color display effect, it is preferably 50 to 1500 parts by mass, more preferably 100 to 1500 parts by mass, further preferably 100 to 450 parts by mass, and particularly preferably 150 to 400 parts by mass. In addition, when multiple G-PIDs are contained, regarding the content of each G-PID, it can be appropriately set so that the total content is within the above range in consideration of the hue of the structural color based on each G-PID and the desired hue in the composite material.

[0156] (2-7) Polymerization initiator

[0157] As the polymerization initiator used in the conventional structured color dental curable composition and the dental curable composition, the same polymerization initiator as that in the dental curable composition of the present invention can be used. Since it often hardens in the oral cavity, it is preferably a chemical polymerization initiator and / or a photo-polymerization initiator, and more preferably a photo-polymerization initiator for the reason that no mixing operation is required. These polymerization initiators can be used alone or in combination of two or more. The mixing amount of the polymerization initiator can be selected as an effective amount according to the purpose, and is usually used in a proportion of 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, further preferably 0.2 to 1.5 parts by mass, and even more preferably 0.01 to 0.5 parts by mass relative to 100 parts by mass of the polymerizable monomer.

[0158] As the photopolymerization initiator that can be preferably used, for example, there can be mentioned: benzoin alkylether, benzyl ketal, benzophenone, α-diketone, thioxanthone compound, bisacylphosphine oxide, etc. It should be noted that a reducing agent is often added to the photopolymerization initiator. As the reducing agent, aromatic amine, aliphatic amine, aldehyde, sulfur-containing compound, etc. can be exemplified. Further, according to need, a trihalomethyltriazine compound, aryl iodonium salt, etc. can also be added.

[0159] In addition, as the thermal polymerization initiator that can be preferably used, for example, there can be mentioned: peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxy dicarbonate, diisopropylperoxydicarbonate; azo compounds such as azobisisobutyronitrile; boron compounds such as tributylborane, tributylboron partial oxide, sodium tetraphenylborate, sodium tetrakis(p-fluorophenyl)borate, tetraphenylboron triethanolamine salt; barbituric acid compounds such as 5-butylbarbituric acid, 1-benzyl-5-phenylbarbituric acid; sulfite salts such as sodium benzenesulfinate, sodium p-toluenesulfinate, etc.

[0160] (2-8) Specific X-ray non-penetrating filler

[0161] The specific X-ray non-penetrating filler has been described. Regarding the specific X-ray non-penetrating filler mixed in the dental curable composition of the present invention, the refractive index n of the cured product of the above-mentioned polymerizable monomer in the dental curable composition of the present invention with respect to the sodium D line at 25°C (MX) and the refractive index n of the resin material of the resin matrix constituting the organic-inorganic composite particles with respect to the sodium D line at 25°C (F-MX) The absolute value of the difference |n (MX) -n (F-MX) |It needs to be 0 to 0.1, wherein the organic-inorganic composite particles constitute the above-mentioned X-ray non-penetrating filler. When this condition is not met, the transparency of the hardened body of the structural color dental curable composition of the present invention is significantly reduced. In order to meet the above conditions, among the specific X-ray non-penetrating fillers mixed in the structural color dental curable composition of the present invention, as the polymerizable monomer that becomes the raw material of (the matrix resin), a polymerizable monomer having the same composition or an approximate composition as the polymerizable monomer in the structural color dental curable composition of the present invention is preferably used. In addition,|n (MX) -n (F-MX) |Preferably 0 to 0.07, more preferably 0 to 0.05, and particularly preferably 0 to 0.035.

[0162] From the viewpoints of the X-ray non-penetrating property, transparency, and structural color manifestation property of the hardened body, the mixing amount of the specific X-ray non-penetrating filler mixed in the dental curable composition of the present invention, in terms of the total mass conversion of the crystalline rare earth fluoride metal particles having a full width at half maximum of 0.3° or more contained in the X-ray non-penetrating filler of the present invention, is 1 to 100 parts by mass, preferably 15 to 75 parts by mass, and more preferably 28 to 80 parts by mass relative to 100 parts by mass of the above polymerizable monomer. When it is less than 1 part by mass (lower limit value), sufficient X-ray non-penetrating property cannot be obtained, and when it exceeds 100 parts by mass (upper limit value), the transparency or structural color color rendering property is significantly reduced.

[0163] (2-9) Other fillers

[0164] For the purpose of adjusting viscosity or the transparency of the cured body, etc., ultrafine particle groups (G-SFP) can be mixed in the dental curable composition of the present invention. Among them, the ultrafine particle groups (G-SFP) are aggregates composed of inorganic particles with an average primary particle size of less than 100 nm. Among them, the average primary particle size of G-SFP needs to be 25 nm or more smaller than the average primary particle size (d1) of G-PID1, which has the smallest average primary particle size among the mixed G-PIDs. When such conditions are not satisfied, it has an adverse effect on the dispersion state of the inorganic spherical particles, and it is difficult to exhibit structural color. In addition, the shape of the inorganic particles constituting G-SFP is not particularly limited, and can be amorphous or spherical. In addition, the lower limit of the average primary particle size is usually 2 nm. For the reason of having little influence on the manifestation of structural color, the average primary particle size of G-SFP is preferably 3 to 75 nm, more preferably 5 to 50 nm. In addition, for the same reason, the average primary particle size of G-SFP is preferably 30 nm or more smaller than the average primary particle size (d1) of G-PID1, more preferably 40 nm or more. As the material of the inorganic particles constituting G-SFP, the same materials as those of the inorganic spherical particles can be used without particular limitation. In addition, similarly to the inorganic spherical particles, surface treatment can also be carried out using a silane coupling agent. In a preferred form, in addition to the average primary particle size and shape, it is also basically the same as the inorganic spherical particles. Regarding the content of G-SFP, it can be appropriately determined in consideration of the viscosity of the curable composition, the transparency of the cured body (or the contrast as an index thereof), etc. Usually, it is 0.1 to 50 parts by mass, preferably 0.2 to 30 parts by mass, relative to 100 parts by mass of the polymerizable monomer.

[0165] In addition, as long as it is within the range that does not significantly hinder the effects of the present invention, the dental curable composition of the present invention can contain other rare earth metal fluoride particles other than the rare earth metal fluoride particles mixed as specific X-ray non-penetrating fillers. The mixing amount of such rare earth metal fluoride particles is preferably 5 parts by mass or less, particularly preferably 0 to 3 parts by mass, relative to 100 parts by mass of the above polymerizable monomer. In particular, the mixing amount of crystalline rare earth fluoride metal particles with a full width at half maximum of less than 0.3° is preferably 0 to 0.5 parts by mass or less. When a specific X-ray non-penetrating filler and non-composite particles with a full width at half maximum of 0.3° or more are used simultaneously, the content of crystalline rare earth fluoride metal particles with a full width at half maximum of 0.3° or more contained in the specific X-ray non-penetrating filler and the total mixing amount of the non-composite particles are preferably 0 to 100 parts by mass, particularly preferably 0 to 50 parts by mass, relative to 100 parts by mass of the above polymerizable monomer.

[0166] (2-10) Other additives, etc.

[0167] Within the range that does not impede its effects, other additives such as polymerization inhibitors and ultraviolet absorbers can be mixed in the dental hardenable composition of the present invention. As described above, the hardened body of the structural color system dental hardenable composition of the present invention exhibits structural color even without using coloring substances such as pigments. Therefore, it is not necessary to mix pigments that may change color over time in the hardenable composition of the present embodiment. However, the mixing of pigments itself is not denied, and pigments that do not impede the degree of colored light generated by interference based on spherical fillers can be mixed. Specifically, the amount of pigments that can be mixed is about 0.0005 to 0.5 parts by mass, preferably about 0.001 to 0.3 parts by mass, relative to 100 parts by mass of the polymerizable monomer.

[0168] 4. Manufacturing method of the dental hardenable composition of the present invention

[0169] The dental hardenable composition of the present invention can provide a hardened body that exhibits a specified hue of structural color independent of the incident angle of light by containing the above-described respective components in specified amounts. From the viewpoint of being able to reliably exhibit the above structural color, it is preferably prepared by the following method.

[0170] That is, it is preferable to include a mixing step of weighing and mixing all the components that are the raw materials of the dental hardenable composition of the present invention in specified amounts, and in this mixing step, it is prepared by a method of mixing under the following mixing conditions, where the mixing conditions are such that for the mixture obtained by this step, it is possible to confirm that the dispersion state of the inorganic particles in the hardened body obtained by hardening this mixture satisfies the following conditions (I) and (II).

[0171] [Conditions that the dispersion state should satisfy]

[0172] (I) In a radial distribution function graph with the dimensionless number (r / r0) obtained by dividing r by r0 and normalizing as the x-axis and the radial distribution function g(r) as the y-axis, representing the relationship between r / r0 and g(r) corresponding to r at this time, the closest interparticle distance r1 is a value that is more than 1 times and less than 2 times the average particle diameter r0 of the entire inorganic spherical particles dispersed in the hardened body of the mixture. Here, r is the distance from the center of any inorganic spherical particle dispersed in the hardened body, r0 is the average particle diameter of the entire inorganic spherical particles dispersed in the hardened body, and the closest interparticle distance r1 is defined as the distance corresponding to the peak top of the peak closest to the origin among the peaks appearing in this radial distribution function graph.

[0173] (II) When using the r corresponding to the peak top of the peak that is the second closest to the origin among the peaks appearing in the radial distribution function graph as the next closest interparticle distance r2, the minimum value of the radial distribution function g(r) between the closest interparticle distance r1 and the next closest interparticle distance r2 is a value of 0.56 or more and 1.10 or less.

[0174] Here, the radial distribution function g(r) is a well-known function as a function for obtaining the existence probability of other particles existing at a location at a distance r from an arbitrary particle, and is defined by the following formula (1).

[0175] g(r) = {1 / <ρ>} × {dn / da}…(1)

[0176] It should be noted that in the above formula (1), <ρ> represents the average particle density of the particles in the plane, dn represents the number of particles existing in the region between two circles centered on an arbitrary particle in the plane with radii r and r + dr respectively, and da represents the area of the above region, which is 2πr × dr.

[0177] The radial distribution function g(r) is generally represented by a radial distribution function graph with the x-axis (distance axis) taking the distance r and the y-axis (vertical axis) taking the g(r) value at that r {the calculation result based on the above formula (1)}, or a radial distribution function graph with the distance axis taking the dimensionless number obtained by normalizing r divided by the average particle diameter of the particles and the y-axis (vertical axis) taking the g(r) value at r corresponding to the value of the x-axis (the calculation result of the above formula).

[0178] In the above manufacturing method, for the reasons that the confirmation of <ρ> and dn is easy and reliable, it is preferable to adopt <ρ>, dn, and da (= 2πr × dr) corresponding to the value of dr used when determining the above dn, which are determined based on the scanning electron microscope image with the inner surface of the hardened body of the above mixture as the observation plane, and calculate g(r) through the above formula (1). The determination of <ρ>, dn, and da can be as follows. First, harden the above mixture, and by means of grinding the surface of the obtained hardened body, etc., expose the plane (observation plane) that can observe the dispersion state of the inorganic spherical particles inside the hardened body to the surface. Then, observe this observation plane with a scanning electron microscope and obtain a microscope image of a region containing at least 500 or more inorganic spherical particles in the plane. Then, using image analysis software (such as the free software "Simple Digitizerver3.2"), for the obtained scanning electron microscope image, find the coordinates of the inorganic spherical particles in the region. Select one coordinate of any inorganic spherical particle from the obtained coordinate data, draw a circle with a radius of r containing at least 200 or more inorganic spherical particles centered on the selected inorganic spherical particle, and count the number of inorganic spherical particles contained in this circle, whereby the average particle density <ρ> (unit: pieces / cm 2 ).

[0179] In addition, regarding dn, when representing the average particle diameter of the inorganic spherical particles by r0, set dr to have a value whose length is from r0 / 100 to about r0 / 10, take any selected inorganic spherical particle as the central particle, and count the number of inorganic spherical particles contained in the region between the circle with a radius of r from the center and the circle with the same center and a radius of r + dr, whereby dn can be determined. Further, based on the actually set length of dr, determine the area da of the region between the two circles as 2πr × dr.

[0180] Then, the dimensionless number (r / r0) obtained by dividing r by r0 and normalizing it is used as the x-axis, and the radial distribution function g(r) representing the probability that other inorganic spherical particles exist at a location at a distance r from the center of any of the above inorganic spherical particles is used as the y-axis. A graph showing the relationship between r / r0 and g(r) corresponding to r at this time is a radial distribution function graph, where r is the distance from the center of any inorganic spherical particle dispersed in the hardened body, and r0 is the average particle diameter of the inorganic spherical particles dispersed in the composite material as a whole. From the viewpoint of maintaining short-range order and easily exhibiting structural color, r1 / r0 is 1.0 to 2.0, preferably 1.0 to 1.5. In addition, from the viewpoints of exhibiting structural color and easily obtaining tonal harmony as a dental filling material, the minimum value of the radial distribution function g(r) between the closest inter-particle distance r1 and the next closest inter-particle distance r2 is a value of 0.56 to 1.10, preferably a value of 0.56 to 1.00.

[0181] To easily satisfy these conditions, in the mixing step, it is preferable to mix inorganic spherical particles (G-PID) as an organic-inorganic composite filler having a particle diameter of 5 to 50 μm, preferably 5 to 30 μm, or as agglomerated particles having a particle diameter of 5 to 200 μm, preferably 10 to 100 μm. In addition, if air bubbles are mixed in during mixing, it is not only difficult to satisfy the above conditions, but also becomes a defect in the composite material. Therefore, it is preferable to perform a defoaming treatment or the like so that no air bubbles remain at least after mixing. As a defoaming method, based on the reason that air bubbles can be removed from a high-viscosity composition in a short time, a defoaming method under reduced pressure is preferably adopted. When inorganic spherical particles are mixed while paying attention to this point, in principle, as long as sufficient stirring is performed, the above conditions are satisfied. However, even in the case where the state is judged to be uniform by a visual method, from the viewpoint of satisfying the above conditions, sometimes the stirring is not sufficient and it is difficult to confirm the end point. Therefore, it is preferable to perform the mixing step after confirming the end point by the method (a) or (b) above, or to perform the mixing step while confirming the end point.

[0182] Method (a): For a curable composition having the same or substantially the same composition as the actually manufactured curable composition, mix by changing multiple mixing conditions, and determine the mixing conditions that satisfy the above conditions (I) and (II) by investigating the radial distribution function g(r) in the hardened body of the mixture obtained during mixing under each mixing condition, and adopt the same mixing conditions as the determined mixing conditions.

[0183] Method (b): Take a sample of a part of the mixture obtained during and / or after the above mixing step, confirm whether the dispersion state of the above inorganic particles in the hardened product of the sampled mixture satisfies the above conditions (I) and (II), and continue mixing until these conditions are satisfied.

[0184] 5. Hardening method of the dental hardenable composition of the present invention

[0185] As a method for hardening the dental hardenable composition of the present invention, according to the polymerization initiation mechanism of the polymerization initiator used, a known polymerization method can be appropriately adopted. Specifically, light irradiation based on light sources such as carbon arc lamps, xenon lamps, metal halide lamps, tungsten lamps, fluorescent lamps, sunlight, helium-cadmium lasers, argon-ion lasers, etc., heating using a heating polymerizer, or a method combining them can be used without any limitation. In the case of polymerization by light irradiation, the irradiation time varies depending on the wavelength and intensity of the light source, the shape or material of the hardened body, so it can be determined in advance through preliminary experiments. In addition, when using the hardenable composition of this embodiment in dental applications, it is usually preferable to adjust the mixing ratio of various components in advance so that the irradiation time is in the range of about 5 to 60 seconds.

[0186]

Examples

[0187] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[0188] 1. Substance names and their abbreviations

[0189] (1) Polymerizable monomer

[0190] UDMA: 1,6-bis(methacrylethyloxycarbonylamino)-2,2,4-trimethylhexane

[0191] 3G: Triethyleneglycol dimethacrylate

[0192] D-2,6E: 2,2-bis(4-methacryloyloxy polyethoxyphenyl)propane

[0193] TFM: 2,2,3,3-tetrafluoropropylmethacrylate

[0194] (2) Polymerization initiator

[0195] CQ: Camphorquinone (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0196] AIBN: Azobisisobutyronitrile (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0197] (3) Additive (reducing agent)

[0198] DMBE: p-N,N-dimethyl aminobenzoate Ethyl (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0199] (4) Polymerizable monomer composition (monomer composition)

[0200] M1: A liquid composition prepared by stirring and mixing a mixture of UDMA (80 parts by mass), 3G (20 parts by mass), CQ (0.2 parts by mass), and DMBE (0.35 parts by mass) for 6 hours.

[0201] FM1: A liquid composition prepared by stirring and mixing a mixture of UDMA (80 parts by mass), 3G (20 parts by mass), and AIBN (1 part by mass) for 6 hours.

[0202] FM2: A liquid composition prepared by stirring and mixing a mixture of D-2,6E (100 parts by mass) and AIBN (1 part by mass) for 6 hours.

[0203] FM3: A liquid composition prepared by stirring and mixing a mixture of D-2,6E (50 parts by mass), 3G (50 parts by mass), and AIBN (1 part by mass) for 6 hours.

[0204] FM4: A liquid composition prepared by stirring and mixing a mixture of D-2,6E (20 parts by mass), 3G (80 parts by mass), and AIBN (1 part by mass) for 6 hours.

[0205] FM5: A liquid composition prepared by stirring and mixing a mixture of UDMA (70 parts by mass), TFM (30 parts by mass), and AIBN (1 part by mass) for 6 hours.

[0206] FM6: A liquid composition prepared by stirring and mixing a mixture of UDMA (40 parts by mass), TFM (60 parts by mass), and AIBN (1 part by mass) for 6 hours.

[0207] The refractive indices of the hardening component M1 and FM1 - FM6 before and after hardening, measured by the method described below, are shown in Table 1.

[0208] [Table 1]

[0209]

[0210] In the monomer composition M1 shown in Table 1, the content of the polymerization initiator is 0.2 parts by mass relative to 100 parts by mass of the monomer.

[0211] (5) Crystalline rare earth metal fluoride particles

[0212] YbF3-40: Ytterbium fluoride (manufactured by Sukgyung Corporation) having the following characteristics

[0213] Average primary particle size: 40 nm

[0214] Average secondary particle size: 0.6 μm

[0215] Refractive index: 1.55

[0216] It should be noted that these physical property values are measured by the method described below.

[0217] (6) Spherical particle group of the same particle size (G-PID)

[0218] PF-1: A substance obtained by surface-treating spherical silica-zirconia particles (composition: SiO2 / ZrO2 / Na2O = 89.8 / 9.0 / 1.2 (mol%)) having the following characteristics with a silane coupling agent (3-(trimethoxysilyl)propyl methacrylate-3-(methacryloyloxy)propyl trimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.)).

[0219] Average primary particle size: 260 nm

[0220] Refractive index: 1.515

[0221] Uniformity: 0.90

[0222] 5% particle content: 92%

[0223] Here, the uniformity refers to the ratio (D2 / D1) of the maximum diameter D1 of the spherical particles and the particle diameter D2 in the direction orthogonal to the maximum diameter D1. In addition, the average primary particle size and the refractive index are measured by the method described below.

[0224] 2. Measurement and evaluation method of the above physical property values related to raw materials

[0225] (1) Measurement of refractive index

[0226] (1-1) Refractive index of monomer composition M1 and FM1 to FM6 (before curing)

[0227] Regarding the refractive indices of M1 and FM1 to FM6 (before hardening), they were measured using an Abbe refractometer (DR-A1-Plus, manufactured by ATAGO CO., LTD.) as the refractive indices with respect to the sodium D line at 25°C.

[0228] (1-2) Refractive indices of monomer composition M1 and FM1 to FM6 (after hardening)

[0229] After filling the monomer composition into the through-holes (diameter 7 mm, through-hole length 0.5 mm) provided on the mold, the two opening parts of the through-holes were sealed while being pressed with a polyester film. Then, in M1, for the curable component M1 filled in the through-hole, it was irradiated with light for 30 seconds using a halogen-type dental light irradiator (Demetron LC, manufactured by sybron) with a light intensity of 500 mW / cm 2 to cure it. In addition, in M2, instead of light irradiation, a nitrogen gas pressure thermal polymerization device POLINA (manufactured by TOWA Giken Co., Ltd.) was used, and it was heated at 100°C for 30 minutes under nitrogen gas pressure to cure it. Then, for the hardened products of M1 and FM1 to FM6 taken out from the mold, the refractive indices were measured according to the same procedure as (1-1).

[0230] (1-3) Refractive indices of rare earth metal fluoride particles and G-PID

[0231] In a constant temperature room at 25°C, 1 g of the powder to be measured was suspended in 50 mL of anhydrous toluene in a 100 mL sample bottle. While stirring the resulting suspension with a stirrer, 1-bromotoluene was added drop by drop little by little, and the refractive index of the suspension when it became most transparent was measured according to the same procedure as (1-1).

[0232] (2) Average primary particle size of rare earth metal fluoride particles

[0233] Regarding the average primary particle size of rare earth metal fluoride particles, it was determined according to the following procedure using a scanning electron microscope. First, a measurement sample was prepared by fixing the rare earth metal fluoride particles on a specimen stage with carbon paste and then performing a conductive treatment (platinum evaporation). Then, using an electron microscope (JSM-7800FPRIME, manufactured by JEOL Ltd.), the measurement sample was observed at a magnification of 100,000 times, and the average particle size of 100 primary particles in the obtained observation image was determined as the average primary particle size.

[0234] (3) Measurement of the average secondary particle size of rare earth metal fluoride particles

[0235] It is obtained by measuring the particle size distribution and following the steps below. First, a suspension was prepared by suspending 0.1 g of powder (rare earth metal fluoride particles) in 10 mL of ion-exchanged water. Next, while irradiating the suspension with ultrasonic waves, the particle size distribution was measured using a particle size distribution analyzer (LS13-320, manufactured by BECKMAN COULTER) to obtain a volume particle size distribution. Then, the particle diameter (D50v value) at which 50% is accumulated from the small-diameter side of the volume particle size distribution was taken as the average secondary particle diameter of the rare earth metal fluoride particles.

[0236] (4) Average primary particle diameter of G-PID

[0237] It is obtained by measuring the particle size distribution and following the steps below. First, a suspension was prepared by suspending 0.1 g of powder (G-PID) in 10 mL of ion-exchanged water. Next, while irradiating the suspension with ultrasonic waves, the particle size distribution was measured using a particle size distribution analyzer (LS13-320, manufactured by BECKMAN COULTER) to obtain a number particle size distribution. Then, the particle diameter (D50p value) at which 50% is accumulated from the small-diameter side of the number particle size distribution was taken as the average primary particle diameter.

[0238] 3. Preparation of X-ray non-penetrating filler

[0239] (1) Mechanochemical treatment of crystalline rare earth metal fluoride particles

[0240] The mechanochemical treatment of crystalline rare earth metal fluoride particles was carried out according to the steps below. First, a slurry was prepared by mixing 855 g of ion-exchanged water and 45 g of crystalline rare earth metal fluoride particles. Next, using a circulating wet bead mill SC50 (manufactured by Mitsui Mining Co., Ltd.), 100 g of zirconia beads (diameter: 0.3 mm) were used as the medium, and the slurry was dispersed at a rotational speed of 3,000 rpm. The dispersion treatment conditions at this time are shown in Table 2.

[0241] Using a rotary evaporator, the slurry after dispersion treatment was concentrated at a bath temperature of 50 °C, and thus a powder was obtained. Under vacuum, the powder was dried at 80 °C for 15 hours, and thus mechanically chemically treated rare earth metal fluoride particles were obtained. For the rare earth metal fluoride particles with a dispersion treatment time of 0 minutes (the crystalline rare earth metal fluoride particles YbF3-40 itself) F-1, and the mechanically chemically treated rare earth metal fluoride particles F-3 to F-6, the average primary particle diameter was measured by the method described in 2.(2), and the full width at half maximum S was measured by the method shown below. The results are shown together in Table 2.

[0242] Method for measuring the full width at half maximum S: For the powder (rare earth metal fluoride particles) to be subjected to X-ray diffraction measurement, coarse particles were removed by a sieve, and thus a measurement sample was prepared. Next, the measurement sample was filled in the sample stage of an X-ray diffractometer (Smartlab, manufactured by Rigaku Corporation), and X-ray diffraction measurement was performed, and thus an X-ray diffraction pattern (graph) with the horizontal axis being 2θ (°) and the vertical axis being the diffraction intensity was obtained. Here, as the X-ray for X-ray diffraction measurement, CuKα ray was used. Since the rare earth metal fluoride particles were YbF3, the full width at half maximum was determined for the peak (the peak observed around 2θ = 28°) based on the (111) plane of the peak with the maximum intensity. In addition, by changing the measurement powder to the X-ray non-penetrating filler described later, the full width at half maximum C of the X-ray non-penetrating filler can be determined by the same method.

[0243] [Table 2]

[0244]

[0245] (2) Preparation of the raw material composition, and hardening and pulverization treatment

[0246] <Production Example 1>

[0247] Weigh 25 parts by mass of the monomer composition FM 1 and 75 parts by mass of the rare earth metal fluoride particles F-3, and mix them using an agate mortar to prepare a paste-like raw material composition. Then, using a nitrogen-pressurized heat polymerization apparatus POLINA (manufactured by TOWA Giken Co., Ltd.), heat this raw material composition at 100 °C for 30 minutes under nitrogen pressure to thermally harden it and obtain a hardened product. Place the obtained hardened body and zirconia balls (diameter: 25 mm) into a zirconia pot and perform a rotational pulverization treatment for 60 minutes to obtain a pulverized product of the hardened product. For this pulverized product, use a stainless steel sieve with a mesh size of 45 μm to remove coarse particles from the pulverized product, thereby obtaining the X-ray non-penetrating filler CF-1. Measure the average particle diameter and the full width at half maximum C of the X-ray non-penetrating filler CF-1. The results are shown in Table 3.

[0248] In addition, regarding the average particle diameter of the X-ray non-penetrating filler, it is obtained by measuring the particle size distribution and following the steps below. That is, first, prepare a suspension by suspending 0.1 g of powder (X-ray non-penetrating filler) in 10 mL of ethanol. Then, while irradiating this suspension with ultrasonic waves, perform particle size distribution measurement using a particle size distribution analyzer (LS13-320, manufactured by BECKMAN COULTER) to obtain a volume particle size distribution. Then, take the particle diameter (D50v value) at which 50% is accumulated from the small-diameter side of the volume particle size distribution as the average particle diameter of the X-ray non-penetrating filler. In addition, the full width at half maximum C is measured by the same method as the full width at half maximum S.

[0249] <Production Examples 2 to 22>

[0250] Except for changing the types of the monomer composition and the rare earth metal fluoride particles used in the preparation of the raw material composition as shown in Table 3, and further appropriately changing the mixing amount of the rare earth metal fluoride particles, the pulverization time, and / or the mesh size of the sieve, X-ray non-penetrating fillers CF-2 to CF-4, RCF-1, CF-1a to CF-1i, CF-1-50 to 90w, and CF-1FM2 to FM6 are obtained in the same manner as in Production Example 1. Measure the average particle diameter and the full width at half maximum C of these X-ray non-penetrating fillers. The results are shown in Table 3.

[0251] [Table 3]

[0252]

[0253] <Examples 1 to 27 and Comparative Examples 1 to 5>

[0254] (1) Preparation of the curable composition

[0255] After adding an X-ray non-penetrating filler (16 parts by mass) and G-PID: PF-1 (64 parts by mass) to the monomer composition M1 (20 parts by mass), the mixture was obtained by mixing using an agate mortar. Further, the mixture was degassed under vacuum to remove air bubbles, thereby obtaining a paste-like curable composition. In addition, when preparing the curable composition, by changing the type of X-ray non-penetrating filler as shown in Table 4, the curable compositions of Examples 1 to 27 and Comparative Examples 1 to 5 were prepared.

[0256] (2) Evaluation of the cured body

[0257] For each curable composition obtained by the above method, the X-ray contrast, transparency, spectral reflectance ratio, and flexural strength of its cured body were measured, and the dispersion state (radial distribution function) of the inorganic spherical particles was evaluated. The measurement methods and evaluation methods for the above physical properties are as follows. In addition, the evaluation results are shown in Table 5.

[0258] (2-1) Measurement method of X-ray contrast

[0259] The X-ray contrast of the cured body of the curable composition was measured according to the following steps. First, after filling the through-hole (diameter 15 mm, through-hole length 1.0 mm) provided in the polytetrafluoroethylene mold with the curable composition, both ends of the through-hole were sealed while being pressed with a polypropylene film. Then, light irradiation was performed in a state where a dental light irradiator (TOKUSO POWER LIGHT, manufactured by Tokuyama Corporation) was arranged in close contact with the surface of the polypropylene film sealing the opening of the through-hole. The positions of light irradiation were: 5 positions on one opening side of the through-hole (1 position at the center of the through-hole and 4 positions in the inner part compared to the outer edge of the through-hole), and 5 positions on the other opening side of the through-hole (1 position at the center of the through-hole and 4 positions in the inner part compared to the outer edge of the through-hole). Then, by performing light irradiation for 20 seconds at each light irradiation position, a cured body was obtained. For the obtained cured body, the thickness was confirmed using a micrometer. Then, the cured body with a thickness within 1.0 mm ± 0.1 mm was used as the test piece for the measurement of X-ray contrast.

[0260] Next, an X-ray film (ultra-high sensitivity dental X-ray film, manufactured by Kodak) was placed on a lead plate with a thickness of 2.0 mm. Further, a test piece and an aluminum step wedge (Step wedge) with five levels of thickness (thickness: 1.0 ± 0.01 mm, 2.0 ± 0.01 mm, 3.0 ± 0.01 mm, 4.0 ± 0.01 mm, 5.0 ± 0.01 mm) were placed on the X-ray film. Then, from a height position 40 cm above the surface of the X-ray film, the test piece and the step wedge were irradiated with X-rays using an X-ray irradiation device (PANPAS-E, manufactured by YOSHIDA). The irradiation conditions at this time were tube voltage: 60 kVp, irradiation time: 0.3 seconds. Then, the X-ray film was developed and printed on photographic paper. Next, the optical densities of the test piece image and the step wedge image on the photographic paper were measured. Then, a standard line was made based on the five levels of thickness of the step wedge and the optical densities corresponding to these five levels of thickness. Based on this standard line, the thickness of the step wedge (i.e., aluminum material) at which the optical density of the test piece was the same as the optical density of the step wedge was obtained. Then, when the optical density shown by the aluminum material with a thickness of 1 mm was used as a reference (100Al%), the obtained thickness of the aluminum material was converted into a value of Al% as an evaluation index for X-ray contrastability.

[0261] Furthermore, in order to obtain X-ray contrast images, for the test pieces of Example 1, 13, 19 and Comparative Example 1, 4 prepared, and aluminum materials (thicknesses 1, 2, 3, 4 mm), a desktop X-ray penetration inspection device (μB 1300, manufactured by Matsuoka Precision Co., Ltd.) was used to observe the X-ray contrast images. The X-ray irradiation conditions at this time were tube voltage: 55 kV, tube current: 0.30 mA. The observed images were input into dedicated image input software (μRayVision, manufactured by Matsuoka Precision Co., Ltd.), and the X-ray contrast images were saved as digital images. The X-ray contrast images (digital images) obtained by this method are shown in Figure 1 .

[0262] (2-2) Measurement method of transparency

[0263] The transparency of the cured body of the curable composition was measured according to the following steps. First, the curable composition was filled into a hole (diameter: 0.7 cm, through-hole length: 0.1 cm) provided in a polyacetal mold, and both ends of the through-hole were sealed while being pressed with a polypropylene film. Next, a dental light irradiator (TOKUSO POWER LIGHT, manufactured by Tokuyama Corporation) was placed at a position 0.5 cm away from the opening surface of the hole, and light irradiation was performed for 20 seconds to obtain a cured body. For the obtained cured body, the thickness was confirmed using a micrometer. Then, the cured body with a thickness within 1.0 mm ± 0.1 mm was used as the cured body for transparency evaluation. Next, for this cured body, the Y value (the value related to luminance among the three stimulus values in the XYZ colorimetric system defined in JIS Z8701) was measured using a color difference meter (SE7700, manufactured by Nippon Denshoku Industries Co., Ltd.) against a black background and a white background. Then, the contrast C calculated by the following formula was used as an index for transparency evaluation. It should be noted that the closer the value of the contrast C is to 1, the more opaque the material is, and the closer the value is to 0, the more transparent the material is.

[0264] Formula C = Yb / Yw

[0265] Here, in the formula, Yb refers to the Y value when measuring the cured body against a black background, and Yw refers to the Y value when measuring the cured body against a white background.

[0266] (2-3) Method for measuring the spectral reflectance ratio (SR1 / SR2 against a black background)

[0267] The spectral reflectance ratio of the cured body of the curable composition was determined according to the following steps. First, for the cured body used in the transparency evaluation, the spectral reflectance in the wavelength range of 380 nm to 780 nm was measured against a black background using a color difference meter (SE7700, manufactured by Nippon Denshoku Industries Co., Ltd.). Then, the spectral reflectance ratio R was calculated based on the following formula.

[0268] Formula R = SR1 / SR2

[0269] Here, in the formula, SR1 refers to the maximum value of the reflectance in the wavelength region of yellow to red (600 nm to 750 nm), and SR2 refers to the maximum value of the reflectance in the wavelength region of blue (400 nm to 500 nm).

[0270] (2-4) Method for measuring the flexural strength

[0271] The flexural strength of the hardened body was measured according to the following steps. First, a curable composition was filled into a through-hole (length: 25 mm, width: 2 mm, through-hole length: 2 mm) provided in a stainless-steel mold, and both ends of the through-hole were sealed while being pressed with a polypropylene film. Next, light irradiation was performed in a state where a dental light irradiator (TOKUSO POWER LIGHT, manufactured by Tokuyama Corporation) was arranged in close contact with the surface of the polypropylene film sealing the opening of the through-hole. The positions of the light irradiation were: three positions on one opening side of the through-hole (one position at the center of the through-hole and two positions at the inner parts compared to the outer edges at both ends in the length direction of the through-hole), and three positions on the other opening side of the through-hole (one position at the center of the through-hole and two positions at the inner parts compared to the outer edges at both ends in the length direction of the through-hole). Then, light irradiation was performed for 20 seconds at each light irradiation position, thereby obtaining a hardened body. For the obtained hardened body, the size and shape were adjusted to a length of 25 mm ± 2 mm, a width of 2 mm ± 0.1 mm, and a thickness of 2 mm ± 0.1 mm using #1500 water-resistant sandpaper. Then, the hardened body with the adjusted size and shape was used as a test piece for measuring the flexural strength. The test piece was mounted on a precision universal testing machine (autograph AG5000D, manufactured by Shimadzu Corporation), and the three-point bending fracture strength was measured under the conditions of a support distance of 20 mm and a crosshead speed of 1 mm / minute, obtaining a load-deflection curve. Then, the flexural strength was calculated according to the following formula.

[0272] Formula: σB = (3PS) / (2WB 2 )

[0273] Here, the symbols in the formula respectively represent:

[0274] σB: flexural strength (Pa), P: load (N) at the fracture of the test piece, S: support distance (m), W: width (m) of the test piece, B: thickness (m) of the test piece.

[0275] (2 - 5) Evaluation method for the dispersion state (radial distribution function) of inorganic spherical particles

[0276] The dispersion state (radial distribution function) of the inorganic spherical particles in the curable composition was evaluated through the following steps. For the cured body produced in the same manner as the evaluation of the above transparency, using an ion milling device (IM4000, manufactured by Hitachi, Ltd.), cross-section milling was performed under the conditions of 2 kV and 20 minutes, and this was used as the observation plane. Then, after preparing a measurement specimen in which this cured body was fixed to the specimen stage using carbon paste and the observation plane was subjected to conductive treatment (platinum evaporation). Next, the measurement specimen was observed with an electron microscope (JSM-7800FPRIME, manufactured by JEOL Ltd.) at a magnification of 10,000 times. For 1,000 inorganic spherical particles in the obtained observation image, using image analysis software (e.g., "Simple Digiizer ver3.2" free software), the coordinates in the observation image were obtained. Arbitrarily select one coordinate of an inorganic spherical particle from the obtained coordinate data. With the selected inorganic spherical particle as the center, draw a circle with a radius of t that contains at least 200 or more inorganic spherical particles, find the number of spherical particles contained in the circle, and calculate the average particle density <ρ> (unit: number / cm 2 ). dr is a value around r0 / 100 to r0 / 10 (r0 represents the average primary particle diameter of the inorganic spherical particles), and the number of particles dn contained in the region between the circle with a distance r from the central inorganic spherical particle and the circle with a distance r + dr, and the area da of the region were obtained. Using the values of <ρ>, dn, and da obtained in this way, through the following formula

[0277] g(r) = {1 / <ρ>} × {dn / da}

[0278] the radial distribution function g(r) was obtained. Then, a graph showing the relationship between the radial distribution function and r / r0 (r represents an arbitrary distance from the center of the circle, and r0 represents the average primary particle diameter of the inorganic spherical particles) was created, and based on the obtained graph, it was evaluated whether the following conditions (I) and (II) were satisfied (〇) or not satisfied (×).

[0279] (I) The closest inter-particle distance r1 is a value of 1 times or more and 2 times or less the average particle diameter r0, where the closest inter-particle distance r1 is defined as: r corresponding to the peak top of the peak closest to the origin in the radial distribution function graph.

[0280] (II) The minimum value of the radial distribution function g(r) between the next nearest-neighbor particle distance r2 and the nearest-neighbor particle distance r1 is a value of 0.56 or more and 1.10 or less, where the next nearest-neighbor particle distance r2 is defined as: r corresponding to the peak top of the peak that is the second closest to the origin in the radial distribution function graph.

[0281] [Table 4]

[0282]

[0283] [Table 5]

[0284]

[0285] Comparative Example 1 is an example of a base existing structural color dental hardening composition, which is prepared such that the spectral reflectance shows 1.16, so that excellent color tone coordination (structural color in the yellow to red region) is shown when used as a CR for repairing dentin or a cavity formed from enamel to dentin, but since no X-ray non-penetrating filler is mixed, sufficient X-ray contrast is not shown.

[0286] From the results of Comparative Examples 2 to 4, it can be seen that when crystalline rare earth metal fluoride particles are mixed without organo-inorganic compounding, although the X-ray contrast is improved, as described above, the crystalline rare earth metal fluoride particles enter between G-PIDs and hinder the formation of a periodic structure, not satisfying Condition I in the radial distribution function evaluation (compared with the value of Comparative Example 1 without crystalline rare earth metal fluoride particles), and the spectral reflectance ratio is low.

[0287] From the results of Comparative Example 5, it can be seen that when crystalline rare earth metal fluoride particles with a full width at half maximum of less than 0.3° are organo-inorganic compounded and mixed, the X-ray contrast and flexural strength are improved, satisfying Conditions I and II in the radial distribution function evaluation. However, due to light refraction or scattering between the crystalline rare earth metal fluoride particles and the matrix, compared with the case where no crystalline rare earth metal fluoride particles are mixed (Comparative Example 1), the hardened body becomes opaque and the spectral reflectance ratio decreases.

[0288] From the results of Examples 1 to 4, 22 to 27, it can be seen that when crystalline rare earth metal fluoride particles with a full width at half maximum of 0.3° or more are organo-inorganic compounded and mixed (specific X-ray non-penetrating filler is mixed), similar to Comparative Example 5, the X-ray contrast and flexural strength can be improved, and further, the decrease in the spectral reflectance ratio can be suppressed, thereby maintaining a high spectral reflectance ratio.

[0289] From the results of Examples 5 to 13, it was found that: the smaller the particle size of the X-ray non-penetrating filler to be mixed, the lower the X-ray contrast and the higher the flexural strength. However, the particle size of the X-ray non-penetrating filler has no effect on the evaluation of transparency, spectral reflectance ratio, and radial distribution function.

[0290] From the results of Examples 14 to 18, it was found that: the larger the refractive index difference between the resin matrix of the organic-inorganic composite particles constituting the X-ray non-penetrating filler to be mixed and the cured product of the monomer composition, the slightly less transparent the cured product, and the spectral reflectance ratio slightly decreases. However, it shows transparency and spectral reflectance ratio within the range not impairing the structural color system CR characteristics. In addition, the X-ray contrast and flexural strength are improved, and Conditions I and II in the radial distribution function evaluation are satisfied. These compositions have the characteristics of the structural color system CR.

[0291] From the results of Examples 19 to 21, it was found that: the lower the content of the crystalline rare earth metal fluoride particles in the organic-inorganic composite particles constituting the X-ray non-penetrating filler to be mixed, the lower the X-ray contrast and the more transparent the cured product. And the higher the content, the higher the X-ray contrast and the more opaque the cured product. However, the content of the crystalline rare earth metal fluoride particles in the organic-inorganic composite particles constituting the X-ray non-penetrating filler has no effect on the evaluation of spectral reflectance ratio or radial distribution function.< / ii>

Claims

1. A dental hardening composition, characterized in that, the dental hardening composition is composed of 100 parts by mass of a polymerizable monomer, one or more "same-particle-size spherical particle groups" (G-PID) in a total amount of 10 to 1500 parts by mass, and a polymerization initiator, wherein the one or more "same-particle-size spherical particle groups" (G-PID) are composed of an aggregate of inorganic spherical particles having a specified average primary particle size in the range of 100 to 1000 nm, each inorganic spherical particle constituting the aggregate is substantially composed of the same substance, and in the number-based particle size distribution of the aggregate, more than 90% of the total number of particles exists within a range of ±5% of the specified average primary particle size; When the number of the one or more "spherical particle groups of the same particle size" is set to a, each "spherical particle group of the same particle size" is represented by G-PID in ascending order of its average primary particle size m When expressed, the substances of the respective particles constituting each G-PID when a is 2 or more m can be different from each other. In this case, the average primary particle sizes of the respective G-PIDs m differ from each other by 25 nm or more. Here, when a is 1, m is 1, and when a is 2 or more, m is a natural number from 1 to a; When the refractive index of the cured product of the polymerizable monomer with respect to the sodium D line at 25°C is set to n (MX) and the refractive index of the inorganic spherical particles constituting each of the G-PIDs m with respect to the sodium D line at 25°C is set to n (G-PIDm) for any n (G-PIDm) the following holds n (MX) <n (G-PIDm) relationship; the dental hardening composition can provide a hardened body that exhibits a specified color tone of structural color, wherein the specified color tone is independent of the incident angle of light; it contains 1 to 100 parts by mass of an X-ray non-penetrating filler in terms of the total mass of the crystalline rare-earth fluoride metal particles, and the X-ray non-penetrating filler is characterized in that it is composed of organic-inorganic composite particles in which a plurality of crystalline rare-earth metal fluoride particles are dispersed in a resin matrix. When the crystallinity of each crystalline rare-earth metal fluoride particle constituting the powder formed by the crystalline rare-earth metal fluoride particles is represented by the full width at half maximum of the maximum peak derived from the crystalline rare-earth metal fluoride in the X-ray diffraction pattern obtained by performing X-ray diffraction measurement on the powder, the full width at half maximum of the crystalline rare-earth metal fluoride particles is 0.3° or more, where the unit of the full width at half maximum is °; The refractive index n of the cured product of the polymerizable monomer with respect to the sodium D line at 25°C (MX) and the refractive index n of the resin material of the resin matrix constituting the organic-inorganic composite particles with respect to the sodium D line at 25°C (F-MX) The absolute value of the difference|n (MX) -n (F-MX) |is 0 to 0.1, where the organic-inorganic composite particles constitute the X-ray non-penetrating filler.

2. The dental hardening composition according to claim 1, characterized in that, based on the total mass of the organic-inorganic composite particles, the content of the crystalline rare-earth metal fluoride particles in the organic-inorganic composite particles constituting the X-ray non-penetrating filler is 60 to 90 mass%.

3. The dental hardening composition according to claim 1, characterized in that, the average particle size of the organic-inorganic composite particles constituting the X-ray non-penetrating filler is 22 to 70 μm.

4. The dental hardening composition according to claim 1, characterized in that, the rare-earth metal fluoride particles are ytterbium fluoride particles.

5. The dental hardening composition according to claim 1, characterized in that, the average primary particle size of all the "same-particle-size spherical particle groups" (G-PID) contained therein is in the range of 230 to 350 nm.

6. The dental hardening composition according to claim 1, characterized in that, it does not contain other rare-earth metal fluoride particles other than the rare-earth metal fluoride particles mixed as the X-ray non-penetrating filler, or, relative to 100 parts by mass of the polymerizable monomer, the content thereof is 5 parts by mass or less.

7. The dental hardening composition according to claim 1, characterized in that, Provided is a cured body having a contrast C, which is an index of transparency of a dental hardenable composition, of 0.20 to 0.

50. The contrast C is defined as the ratio Y b measured using a color difference meter on a black background for a cured body sample having a thickness of 1 mm, which is Y w to the Y value b / Y w measured on a white background.

8. The dental hardening composition according to claim 1, characterized in that, The mixing amount of the polymerization initiator is 0.01 to 0.5 parts by mass relative to 100 parts by mass of the polymerizable monomer.

9. The curable composition for dental use according to claim 1, wherein the full width at half maximum is 40° or less.

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