Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/15—Compositions characterised by their physical properties
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/15—Compositions characterised by their physical properties
  • A61K6/16—Refractive index
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/15—Compositions characterised by their physical properties
  • A61K6/17—Particle size
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/80—Preparations for artificial teeth, for filling teeth or for capping teeth
  • A61K6/884—Preparations for artificial teeth, for filling teeth or for capping teeth comprising natural or synthetic resins
  • A61K6/887—Compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/20—Esters of polyhydric alcohols or phenols, e.g. 2-hydroxyethyl (meth)acrylate or glycerol mono-(meth)acrylate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/26—Esters containing oxygen in addition to the carboxy oxygen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/34—Esters containing nitrogen, e.g. N,N-dimethylaminoethyl (meth)acrylate
  • C08F220/36—Esters containing nitrogen, e.g. N,N-dimethylaminoethyl (meth)acrylate containing oxygen in addition to the carboxy oxygen, e.g. 2-N-morpholinoethyl (meth)acrylate or 2-isocyanatoethyl (meth)acrylate

Definitions

• the present invention relates to a method for producing an X-ray-opaque filling material and a method for producing a dental hardenable composition.
• CR composite resin
• the CR restoration has the advantages of being able to reduce the amount of tooth structure that needs to be removed, being able to impart a color tone equivalent to that of natural teeth, and being easy to operate.
• the mechanical strength of the hardened CR body has been improved and its adhesive strength with the tooth has been improved, it is used not only for repairing anterior teeth, but also for molar teeth, which are subject to high occlusal pressure.
• CR is usually colored by mixing it with pigments or dyes, but these substances can fade or discolor over time in the hardened body after treatment due to deterioration over time, causing discoloration over time after restoration, and the appearance of the restored area can no longer match that of the natural tooth.
• CRs have been proposed that use a filler containing spherical inorganic particles with a specific average particle size and particle size distribution, and that have a refractive index greater than that of the resin that becomes the matrix when cured, thereby producing structural colors that develop in a specific color tone independent of the angle of incidence of light due to light interference and scattering, etc.
• structural color CRs which have attracted attention
• the structural color system CR has the following excellent features: (1) it does not use dyes or pigments, so it is less likely to discolor over time; (2) it produces a structural color of a specific tone that is independent of the angle of incidence of light, depending on the average particle size of the spherical inorganic particles used; in particular, when spherical inorganic particles with an average primary particle size of 230-350 nm are used, it can be colored yellow to red, which is similar to the color of dentin; and (3) since the hardened body has a moderate transparency, it easily matches the color of the tooth to be restored, and it can be used with a single type of composite resin to restore a wide range of colors of teeth to be restored with an appearance close to that of natural teeth, without the need for complicated shade taking or shade selection of the composite resin.
• the polymerizable curable composition that constitutes the structural color system CR satisfies the following conditions (a) and (b), but it is known that when the following condition (c) is also satisfied, a cured product that more reliably exhibits the desired structural color is obtained (see Patent Document 2).
• A Contains polymerizable monomer (A), inorganic particles (B), and photopolymerization initiator (C) as constituents.
• the inorganic particles (B) are (A-1)
• the present invention is composed of an aggregate of inorganic spherical particles having a predetermined average primary particle diameter within a range of 100 to 1000 nm, and each inorganic spherical particle constituting the aggregate is substantially composed of the same substance, and includes one or more "groups of spherical particles having identical diameters" (G-PIDs) in which 90% or more of the total number of particles in the number-based particle size distribution of the aggregate is present within a range of 5% around the predetermined average primary particle diameter, (A-2) when the number of the one or more "spherical particle groups of the same diameter" is a, and each "spherical particle group of the same diameter” is expressed as G-PID m (where m is 1 when a is 1, and is a natural number from 1 to a when a is 2 or more) in order of increasing average primary particle diameter, when a is 2 or more, the substances constituting the individual particles of each G-PI
• n (MX) the refractive index at 25° C. of the inorganic spherical particles constituting each G-PID m is n (G-PIDm) , for any n (G-PIDm) , n (MX) ⁇ n (G-PIDm)
• n (MX) the refractive index at 25° C. of the inorganic spherical particles constituting each G-PID m
• the x-axis is a dimensionless number (r/ r0 ) obtained by dividing the distance from the center of any inorganic spherical particle dispersed in the cured body by the average particle size r0 of all the inorganic spherical particles dispersed in the cured body
• the y-axis is the radial distribution function g(r)
• the nearest inter-particle distance r1 which is defined as the r corresponding to the peak top of the peak closest to the origin among the peaks appearing in the radial distribution function graph, is a value that is 1 to 2 times the average particle size r0 of all the inorganic spherical particles dispersed in the cured body of the mixture.
• the colored light due to interference in the hardened body occurs in the part where the constituent particles are relatively regularly accumulated, and the colored light due to scattering occurs in the part where the constituent particles are randomly dispersed.
• the above condition (I) when r1 is less than 1 time of r0 , the overlap between the particles in the plane increases, and when r1 is more than 2 times of r0 , the particles do not exist near the selected central inorganic particle, so that the short-range order disappears and the structural color does not appear.
• the minimum value is less than 0.56
• the long-range order of the arrangement structure of the inorganic spherical particles increases, and not only does the incidence angle dependency of the light that appears increase, but the saturation of the hardened body increases, making it difficult to obtain color tone compatibility when used as a dental filling material, but when the minimum value is more than 1.10, the arrangement structure of the inorganic spherical particles becomes a random structure
• each G-PID develops a structural color in the hardened form with a color tone that corresponds to its average primary particle size, so it is also possible to control the overall color tone by combining the G-PIDs that are blended.
• inorganic oxide fillers are generally used as fillers to be mixed into hardenable compositions used as CR, including existing structural color dental hardenable compositions.
• silica-based fillers have low X-ray opacity. For this reason, the hardened material in the cavity is not imaged during X-ray or CT scan photography during dental treatment, making it difficult to identify the treatment site.
• the first powder "a powder having a full width at half maximum of 0.3° or more in the X-ray diffraction pattern obtained by X-ray diffraction measurement of a powder made of crystalline rare earth metal fluoride particles" (hereinafter also referred to as “low crystalline rare earth metal fluoride powder”), is obtained by mechanochemically treating a powder having a full width at half maximum of less than 0.3° (hereinafter also referred to as "high crystalline rare earth metal fluoride powder”).
• the full width at half maximum of the low crystalline rare earth metal fluoride powder is preferably 40° or less.
• the present invention was made in consideration of the above circumstances, and aims to provide a method for efficiently producing a radiopaque filler that, when mixed with an existing structural color dental hardenable composition (suitable as a structural color CR capable of aesthetic restoration), can impart high radiopacity to the hardened product without impairing the characteristics of the composition.
• a first aspect of the present invention is a method for producing a radiopaque filler that imparts radiopaqueness to a dental hardenable composition and a hardened product thereof by blending the radiopaque filler with a dental hardenable composition containing a polymerizable monomer, the method comprising the steps of:
• a powder or granule made of crystalline rare earth metal fluoride particles is subjected to X-ray diffraction measurement, the powder or granule having a full width at half maximum of the maximum intensity peak in an X-ray diffraction pattern obtained is less than 0.3° is defined as a "highly crystalline rare earth metal fluoride powder or granule," and the powder or granule having the full width at half maximum of 0.3° or more is defined as a "lowly crystalline rare earth metal fluoride powder or granule.”
• the X-ray impermeable filler is mainly composed of powder particles
• the amount of the secondary raw material powder particles used in the curable raw material composition preparation step is preferably 230 to 900 parts by mass per 100 parts by mass of the polymerizable monomer.
• the pressure during kneading in the hardenable raw material composition preparation process is preferably 100 to 35,000 (Pa).
• a second aspect of the present invention is Polymerizable monomer: 100 parts by mass, An X-ray impermeable filler mainly composed of powder particles having an average particle size of 3 to 110 ⁇ m as measured by a laser diffraction/scattering method, the powder particles being constituted by organic/inorganic composite particles made of a composite material in which low-crystalline rare earth metal fluoride powder particles are dispersed in a resin matrix: 1 to 100 parts by mass in terms of the total mass of the low-crystalline rare earth metal fluoride powder particles; A method for producing a dental curable composition capable of expressing a structural color of a predetermined color tone independent of the angle of incidence of light and giving a cured product having X-ray contrast properties, by mixing: one or more "spherical particle groups of the same particle size" of 10 to 1,500 parts by mass in total, the group being composed of inorganic spherical particles having a predetermined average primary particle size within a range of 100 to 1,000 nm as measured by observation under an electron
• each "spherical particle group of the same diameter” is represented by G-PID m (where m is 1 when a is 1, and is a natural number from 1 to a when a is 2 or more) in order of decreasing average primary particle diameter, and the refractive index at 25° C.
• n (G-PIDm) the materials constituting the individual particles of each G-PID m may be different from each other, In this case, the average primary particle diameters of the G-PID m differ from each other by 25 nm or more, It is preferable that the relationship n (MX) ⁇ n (G-PIDm) holds for any n (G-PIDm) .
• a new radiopaque filler can be efficiently produced that can impart high radiopacity to the hardened product without compromising the excellent characteristics of structural color CR.
• the X-ray opaque filler (low-crystalline rare earth metal fluoride powder) disclosed in Patent Document 4 has the excellent features as described above, but when the present inventors tried to blend it with structural color CR, they found that in order to obtain high X-ray opacity, it was necessary to blend a large amount of X-ray opaque filler, and in that case, it was found that it was difficult to express the desired structural color (see Reference Comparative Examples 3 and 4 described later).
• the composition comprises: 100 parts by mass of a polymerizable monomer; 10 to 1,500 parts by mass of one or more "spherical particle groups of the same particle size" (G-PID) consisting of an aggregate of inorganic spherical particles having a predetermined average primary particle size within the range of 100 to 1,000 nm, the individual inorganic spherical particles constituting the aggregate being substantially composed of the same substance, and 90% or more of the total number of particles in the number-based particle size distribution of the aggregate being present within a range of 5% around the predetermined average primary particle size; and 0.01 to 0.5 parts by mass of a polymerization initiator, When the number of the one or more "spherical particle groups of the same diameter" is a, and each "spherical particle group of the same diameter” is expressed as G-PID
• n (MX) the refractive index of the inorganic spherical particles constituting each G-PID m at 25° C. to sodium d line is n (G-PIDm) , for each n (G-PIDm) , The relationship n (MX) ⁇ n (G-PIDm) is established,
• a dental hardenable composition capable of giving a hardened product exhibiting a structural color of a predetermined color tone independent of the angle of incidence of light,
• the powder is made of crystalline rare earth metal fluoride particles, and the crystallinity of the individual crystalline rare earth metal fluoride particles constituting the powder is expressed by the full width at half maximum (unit: °) of the maximum peak derived from the crystalline rare earth metal fluoride in an X-ray diffraction pattern obtained by performing X-ray diffraction measurement on the powder, and the X-ray opaque filler (hereinafter also referred to as "specific X-ray opaque filler”) is
• the dental curable composition is characterized in that the absolute value of the difference between the refractive index at 25° C. of the cured product of the polymerizable monomer (n (MX)) to sodium d line (n (F-MX)) of the resin material constituting the resin matrix of the organic-inorganic composite particles constituting the X-ray opaque filler (n(F-MX)) to sodium d line (n(F-MX)) is 0 to 0.1. is proposed.
• the specific radiopaque filler can be said to be a radiopaque filler that can impart high radiopaqueness to the cured product without impairing the characteristics of the composition when it is mixed with an existing structural color dental hardenable composition so as to satisfy the condition that the absolute value of the difference:
• a treatment liquid (treatment slurry) in which low-crystalline rare earth metal fluoride powder particles obtained after mechanochemical treatment are dispersed is dried using a rotary evaporator to obtain a powder (secondary raw material powder particles) and a polymerizable monomer are kneaded using an agate mortar.
• the hardened product obtained by hardening the obtained hardenable composition is pulverized (on a laboratory scale), and it cannot be said that a method for efficiently producing a specific radiopaque filler on an industrial scale has been established.
• the inventors therefore attempted to prepare a curable composition by obtaining a secondary raw material powder by spray drying using a spray dryer or the like, and then kneading it with a polymerizable monomer using a kneading device.
• a kneading device As a result, it became clear that when the content of low-crystalline rare earth metal fluoride powder in the organic-inorganic composite particles that make up the specific X-ray opaque filler is increased in order to impart X-ray opacity, there is a problem in that the kneaded material does not become a paste, and kneading may become impossible.
• the present invention thus solves the above-mentioned problems that are specific to spray drying using a spray dryer and kneading using a kneading device, and by carrying out the above-mentioned kneading (mixing) under a specific reduced pressure, it makes it possible to efficiently produce a specific X-ray opaque filler even in the above-mentioned cases.
• the specific radiopaque filling material is a novel material discovered by the present inventors, we will first explain the specific radiopaque filling material, and then provide a detailed explanation of the manufacturing method of this radiopaque filling material.
• the notation "x to y" using the numerical values x and y means "greater than or equal to x and less than or equal to y.” In such notations where a unit is assigned only to the numerical value y, the unit is also applied to the numerical value x.
• (meth)acrylic means both “acrylic” and “methacrylic.”
• (meth)acrylate means both “acrylate” and “methacrylate”
• (meth)acryloyl means both “acryloyl” and “methacryloyl.”
• (meth)acrylic resin means a polymer obtained by polymerizing only (meth)acrylate monomers as the polymerizable monomers used in the polymerization of the (meth)acrylic resin, or a polymer in which the proportion of (meth)acrylate monomers in the total polymerizable monomers is 50 mol % or more when two or more types of polymerizable monomers including (meth)acrylate monomers are used.
• the specific X-ray opaque filler is mainly composed of a powder or granule comprising crystalline rare earth metal fluoride particles, the powder or granule being composed of organic-inorganic composite particles in which a full width at half maximum of a maximum peak derived from the crystalline rare earth metal fluoride particles having a full width at half maximum of 0.3° or more is represented by the full width at half maximum (unit: °) of the maximum peak derived from the crystalline rare earth metal fluoride in an X-ray diffraction pattern obtained by performing X-ray diffraction measurement on the powder or granule, and the powder or granule has an average particle size of 3 to 110 ⁇ m as measured by a laser diffraction/scattering method.
• mainly composed means that the content of the organic-inorganic composite particles (hereinafter also referred to as "particle body") in the total mass of the specific X-ray opaque filler is 95% by mass or more, preferably 98% by mass or more.
• components that the specific X-ray opaque filler may contain other than the particle body include external additive particles such as silica and titanium oxide (fine particles).
• the organic-inorganic composite particles (particle body) may have a surface that has been subjected to physical surface treatment such as plasma treatment or mechanical surface treatment such as long-term friction stirring, or may have a coating agent treatment using a known coating agent such as silicone oil.
• the crystalline rare earth metal fluoride particles in the organic-inorganic composite particles (particle body) may have a surface treatment with a known surface treatment agent such as a silane coupling agent or a titanate coupling agent.
• the full width at half maximum of the diffraction peak in X-ray diffraction measurements there is a correlation between the full width at half maximum of the diffraction peak in X-ray diffraction measurements and the crystallite size, known as the Scherrer equation, and it is known that the crystallite size is inversely proportional to the full width at half maximum.
• the full width at half maximum (FWHM) is also affected by the distortion of the crystal lattice, and as the full width at half maximum (FWHM) increases and the crystal lattice distortion increases, the full width at half maximum tends to widen.
• the crystallinity decreases when the crystallite distortion is large, the crystallite diameter becomes small, and the fine crystallites are oriented in various directions, so the full width at half maximum can be said to be an index of the crystallinity (more specifically, the perfection of the crystal) of rare earth metal fluorides.
• full width at half maximum means the full width at half maximum (unit: °) of the maximum peak originating from the crystalline rare earth metal fluoride in the X-ray diffraction pattern obtained when X-ray diffraction measurement is performed on a powder material consisting of crystalline rare earth metal fluoride particles.
• Crystalline rare earth metal fluoride powders (low crystalline rare earth metal fluoride powders) with a full width at half maximum of 0.3° or more do not significantly reduce the transparency of the dental hardenable composition hardened body even when they are directly mixed into the dental hardenable composition (see PCT/JP2022/031237 and Reference Comparative Examples 3 and 4 described later).
• the reason for this effect is presumed to be as follows. First, the reduction in transparency in a system in which inorganic fine particles are dispersed in a resin matrix is largely due to the diffuse reflection of light at the interface between the two. On the other hand, it is considered that the surface vicinity of the crystalline rare earth metal fluoride particles gradually becomes amorphous from the surface toward the inside due to the mechanochemical treatment.
• a layer (hereinafter also referred to as a "refractive index gradient layer") in which the refractive index gradually decreases with a certain gradient from the inside toward the surface is formed in the surface vicinity of the crystalline rare earth metal fluoride particles. Then, the formed refractive index gradient layer includes a portion having a refractive index that matches the refractive index of the resin matrix. As a result, the proportion of reflected light decreased overall (the proportion of transmitted light increased), and it is believed that the decrease in transparency was suppressed.
• the same effect can be obtained so long as the following condition is satisfied: the absolute value of the difference between the refractive index at 25°C of the hardened product of the polymerizable monomer (n (MX)) to sodium d line at 25°C and the refractive index at 25°C of the resin material constituting the resin matrix of the organic-inorganic composite particles constituting the specific X-ray opaque filler (n ( F -MX)) is 0 to 0.1, preferably 0 to 0.05.
• the polymerizable monomer in the dental hardenable composition becomes a resin that constitutes the matrix of the hardened body of the dental hardenable composition, and when the refractive index: n (F-MX) value of the polymerizable monomer is close to the refractive index: n (F-MX) value of the resin material that constitutes the resin matrix of the organic-inorganic composite particles, diffuse reflection of light is unlikely to occur 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 hardened body of the dental hardenable composition become integrated), and the above-mentioned properties of the low-crystalline rare earth metal fluoride powder are exhibited.
• the full width at half maximum of the crystalline rare earth metal fluoride powder As described above, by setting the full width at half maximum of the crystalline rare earth metal fluoride powder to 0.3° or more, when a curable composition containing a specific X-ray opaque filler is cured, a cured body having excellent X-ray opacity and transparency can be easily obtained. In other words, even if the amount of the specific X-ray opaque filler blended in the curable composition is increased in order to increase the X-ray opacity of the cured body, a decrease in the transparency of the cured body can be suppressed.
• the full width at half maximum may be 0.3° or more, preferably 0.4° or more, and more preferably 0.5° or more.
• the upper limit of the full width at half maximum is not particularly limited, but in practical terms, it is preferably 40° or less, and more preferably 1° or less.
• crystalline rare earth metal fluoride powder particles with a full width at half maximum of less than 0.3° highly crystalline rare earth metal fluoride powder particles
• organic-inorganic composite particles similar to the organic-inorganic composite particles in the specific X-ray opaque filler in an amount required to impart X-ray opacity
• a decrease in the transparency of the cured body is unavoidable (see Reference Comparative Examples 2 and 5 described below).
• the full width at half maximum can be determined by performing X-ray diffraction measurement on a powder sample to be subjected to X-ray diffraction measurement. Specifically, an X-ray diffraction pattern (chart) is obtained in which the horizontal axis indicates 2 ⁇ (°) and the vertical axis indicates diffraction intensity by performing X-ray diffraction measurement on the powder sample in the range of 2 ⁇ from 20° to 120° using an X-ray diffraction device. It is preferable to use a powder sample from which coarse particles have been removed, for example, by using a sieve with a mesh size of 100 ⁇ m, according to a conventional method.
• the peaks originating from the rare earth metal fluoride in the X-ray diffraction pattern are identified, and the full width at half maximum of the peak having the greatest intensity among the multiple peaks confirmed is obtained.
• the peak width is obtained as the absolute value (unit: "deg [°]”) of the difference between the value of 2 ⁇ at one intersection point and the value of 2 ⁇ at the other intersection point at two intersection points where a convex peak line intersects with a straight line that is parallel to the horizontal axis of the X-ray diffraction pattern (chart) and at the position of 50% intensity.
• the full width at half maximum of the crystalline rare earth metal fluoride powder particles in the organic-inorganic composite particles (particle body) constituting the specific X-ray opaque filler can be confirmed based on the X-ray diffraction pattern obtained by performing powder X-ray diffraction measurement on a powder sample consisting of the particle body.
• the full width at half maximum of the crystalline rare earth metal fluoride powder particles in the particle body can also be confirmed based on the X-ray diffraction pattern obtained by performing powder X-ray diffraction measurement on a powder sample consisting of the secondary raw material powder particles (since the crystallinity of the secondary raw material powder particles does not change or does not change substantially in the mixing and grinding process when preparing the raw material composition).
• the full width at half maximum of the crystalline rare earth metal fluoride particles in the specific X-ray opaque filler contained in the dental hardenable composition of the present invention can also be confirmed based on the X-ray diffraction pattern obtained by performing powder X-ray diffraction measurement on a powder sample containing organic-inorganic composite particles separated from these hardenable compositions or a powder sample obtained from a hardened body of these hardenable compositions.
• the rare earth metal fluoride particles contained in the organic-inorganic composite particles (particle body) are not particularly limited in material, so long as the full width at half maximum is 0.3° or more, and known rare earth metal fluoride particles may be appropriately used.
• the rare earth metal fluoride is preferably lanthanum fluoride (LaF 3 ), cerium fluoride (CeF 3 ), or ytterbium fluoride (YbF 3 ). From the viewpoint of ensuring X-ray opacity, ytterbium fluoride (YbF 3 ) is particularly preferable.
• the resin material that constitutes the resin matrix of the organic-inorganic composite particles (particle body) is not particularly limited, and examples include (meth)acrylic resins and polyaryl ether ketone resins.
• n (MX) means the refractive index at 25°C for sodium d line of the hardened product of the polymerizable monomer contained in the existing structural color dental hardenable composition
• n (F-MX) means the refractive index at 25°C for sodium d line of the resin material constituting the resin matrix of the particle body.
• the average particle size of the organic-inorganic composite particles is 3 to 110 ⁇ m, preferably 8 to 100 ⁇ m.
• the average particle size refers to the median diameter measured by a laser diffraction/scattering method. If the average particle size is outside the above range, from the viewpoint of achieving a better balance between X-ray contrast and mechanical strength, the average particle size is more preferably 22 to 70 ⁇ m, particularly 24 to 55 ⁇ m. Furthermore, when emphasis is placed on ensuring mechanical strength rather than X-ray contrast, the average particle size is preferably 3 to 38 ⁇ m, more preferably 8 to 25 ⁇ m.
• the average particle size is preferably 38 ⁇ m or more, more preferably 70 ⁇ m or more.
• the upper limit is preferably 110 ⁇ m or less, more preferably 100 ⁇ m or less, from the viewpoint of ensuring a certain level of mechanical strength.
• the content of rare earth metal fluoride particles in the organic-inorganic composite particles (particle body) is 60 to 90% by mass, and more preferably 70 to 80% by mass or more, based on the total mass of the organic-inorganic composite particles.
• the manufacturing method of the X-ray-opaque filling material is as follows: a secondary raw material powder preparation step of mechanochemically treating a raw material slurry in which a primary raw material powder comprising highly crystalline rare earth metal fluoride powder having an average primary particle diameter of 1 to 500 nm as measured by electron microscope observation is dispersed in a dispersion medium to obtain a treated slurry liquid in which low-crystalline rare earth metal fluoride powder is dispersed in the dispersion medium, and removing the dispersed matter from the obtained treated slurry to obtain a secondary raw material powder comprising low-crystalline rare earth metal fluoride powder; a curable raw material composition preparation step of kneading 100 parts by mass of a polymerizable monomer and 230 to 900 parts by mass of the secondary raw material powder and grains under an absolute pressure of 1.0 to 1.0 x 10 5 (Pa) (under reduced pressure) to obtain a curable
• Secondary raw powder preparation process In the secondary raw powder preparation process, a raw material slurry in which primary raw material powder particles consisting of highly crystalline rare earth metal fluoride powder particles having an average primary particle diameter of 1 to 500 nm measured by electron microscope observation are dispersed in a dispersion medium is mechanochemically treated to obtain a treated slurry liquid in which low-crystalline rare earth metal fluoride powder particles are dispersed in the dispersion medium, and the obtained treated slurry is spray-dried to obtain secondary raw material powder particles consisting of low-crystalline rare earth metal fluoride powder particles.
• the primary raw material powder particles and secondary raw material powder particles may contain trace amounts of substances other than the crystalline rare earth metal fluoride particles, such as surface treatment agents and additives that are physically attached or chemically bonded to the surfaces of the crystalline rare earth metal fluoride particles.
• the primary raw material powder (highly crystalline rare earth metal fluoride powder), rare earth metal fluorides generally used as X-ray opaque materials and commercially available rare earth metal fluoride powders having a full width at half maximum of less than 0.3° (specifically, about 0.17° to 0.27°) can be used without any particular restrictions. It is preferable to measure the full width at half maximum of the primary raw material powder by X-ray diffraction measurement as necessary.
• the crystalline rare earth metal fluoride particles used as the primary raw powder can be particles whose surfaces have been coated with nanosilica or the like, or particles whose surfaces have been treated with a silane coupling agent or the like.
• the particles contained in the primary raw powder may be pulverized, and the secondary particles (agglomerated particles) and primary particles may be broken down, resulting in a smaller particle size.
• the primary raw powder powder with an average primary particle size measured by observation with an electron microscope of 1 to 500 nm is used, and powder with an average particle size of 5 to 300 nm is preferably used.
• powder with an average particle size of 0.1 to 1 ⁇ m, especially 0.1 to 0.6 ⁇ m, measured by a laser diffraction/scattering method that can also measure the agglomerated particle size is preferably used, and powder with an average particle size of 0.1 to 0.3 ⁇ m is more preferable.
• the average primary particle size is a value measured using a scanning electron microscope. Specifically, the powder was observed under 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 was determined.
• Mechanochemical treatment means a treatment that applies mechanical energy to the primary raw powder particles, and specifically means at least one treatment selected from the group consisting of mechanical grinding, pulverization, and dispersion. From the viewpoint of easily controlling the full width at half maximum, which is also the degree of perfection of the crystals of the mechanochemically treated rare earth metal fluoride particles, to a desired value reliably and efficiently, a wet method is adopted as the mechanochemical treatment method, and a treatment method using a wet bead mill is particularly preferable.
• a solvent such as water or alcohol, or a polymerizable monomer
• a medium that is liquid at room temperature (15°C to 25°C) is preferable.
• a slurry of the raw powder to be treated with the mechanochemical treatment and a medium is brought into contact with media (beads) that have been stirred, vibrated, or otherwise moved. This causes the raw powder to be crushed and disintegrated.
• media be used as the media can be glass, alumina, zircon, zirconia, steel, or resin, but alumina or zirconia is preferred because of their excellent wear resistance and relatively low contamination.
• the size of the beads used can be selected according to the particle size of the desired radiopaque filler, and there is no particular restriction, but it is usually preferable to use beads with a diameter of 0.01 mm to 0.5 mm. Beads with such a diameter are also suitable for obtaining an radiopaque filler with a particle size suitable for addition to a dental hardenable composition.
• wet bead mills come in a variety of types, including batch types, in which the slurry and beads are directly fed into the equipment for processing, circulation types, in which the slurry is circulated between a tank and the equipment, and pass types, in which the slurry is passed through the equipment a set number of times.
• batch types in which the slurry and beads are directly fed into the equipment for processing
• circulation types in which the slurry is circulated between a tank and the equipment
• pass types in which the slurry is passed through the equipment a set number of times.
• the concentration of the slurry used in the mechanochemical treatment is preferably 50 parts by mass or less of raw material powder per 100 parts by mass of medium. If the raw material powder in the slurry exceeds 50 parts by mass, the viscosity of the slurry will increase, and mechanochemical treatment may become difficult.
• the increase in the viscosity of the slurry can be suppressed by adding a dispersant to the slurry. Therefore, by adding a dispersant to the slurry, it is possible to mechanochemically treat a slurry with a higher concentration.
• the dispersant used can be any known surfactant without any particular restrictions, and examples of such dispersants include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and polymeric surfactants thereof. Specific examples include glycerin fatty acid esters and their alkylene glycol adducts, aliphatic monocarboxylates, alkylamine salts, and alkylbetaines.
• a cationic surfactant from the viewpoint of dispersibility during mixing.
• Mechanochemical treatment conditions vary depending on the operating method and bead diameter of the wet bead mill device used, the full width at half maximum of the raw material powder, and the concentration of the slurry. These conditions can be selected appropriately after conducting preliminary experiments using the device that will actually perform the mechanochemical treatment and checking the full width at half maximum of the raw material powder after mechanochemical treatment versus the mechanochemical treatment time. Furthermore, when mechanochemical treatment is performed, it is possible to obtain mechanochemically treated secondary raw material powder with the desired full width at half maximum by appropriately sampling the slurry during mechanochemical treatment as necessary and checking the full width at half maximum as appropriate.
• the full width at half maximum of the secondary raw powder may be 0.3° or more, but from the viewpoint of obtaining the radiopaque filler of this embodiment more stably and reliably, it is preferably 0.35° or more, and more preferably 0.4° or more.
• the upper limit of the full width at half maximum of the secondary raw powder is not particularly limited, and can be appropriately selected according to the target full width at half maximum of the radiopaque filler to be manufactured, but in practical terms, it is preferably 40° or less, and more preferably 1° or less.
• spray drying refers to the process of spraying a liquid raw material (slurry) into hot air to instantly evaporate the water and obtain a dry powder (granules).
• slurry liquid raw material
• the secondary raw powder particles that have been through the mechanochemical treatment process and the post-treatment process may be surface-treated to improve their affinity with the resin matrix raw material used to granulate the organic-inorganic composite particles.
• Surface treatment agents that can be used for the surface treatment include commonly used compounds such as silane coupling agents and titanate coupling agents.
• curable Raw Material Composition Preparation Step 100 parts by mass of the polymerizable monomer, which is the raw material of the resin matrix, and 150 to 900 parts by mass of the secondary raw material powder are kneaded under a pressure of 1.0 to 1.0 x 10 5 (Pa) to obtain a curable raw material composition.
• the X-ray contrast can be improved more efficiently when the specific X-ray opaque filler produced by the production method of the present invention is added to a dental curable composition for the purpose of imparting X-ray contrast, so the greater the amount of the secondary raw material powder added relative to 100 parts by mass of the polymerizable monomer, the more pronounced the effect of the present invention becomes.
• the amount of the secondary raw material powder added relative to the polymerizable monomer increases, the kneading time required for the curable raw material composition preparation step becomes longer. Therefore, the amount of the secondary raw material powder added in the production method of the present invention is preferably 233 to 900 parts by mass, particularly 250 to 567 parts by mass, relative to 100 parts by mass of the polymerizable monomer.
• a known polymerizable monomer such as a radical polymerizable monomer can be used.
• a radical polymerizable monomer such as a (meth)acrylate monomer used in a dental curable composition.
• the refractive index: nX of the crystalline rare earth metal fluoride particles used as the first and second raw powders at 25°C to the sodium d line is usually in the range of 1.50 to 1.65, and in the case of the crystalline ytterbium fluoride particles, it is 1.55.
• the refractive index: n (F-MX) of the resin material that is the main component of the resin matrix constituting the organic-inorganic composite particles (particle body) at 25°C to the sodium d line is preferably 1.45 to 1.60.
• the "resin material that is the main component of the resin matrix” means a cured product of a polymerizable monomer (a cured product of a composition consisting of only a polymerizable monomer or a cured product of a composition consisting of a polymerizable monomer and a small amount of a polymerization initiator).
• nX and n (F-MX) have values close to each other as described above, it becomes easier to improve the transparency of the curable composition using an X-ray opaque filler.
• the raw material composition for granulating the hardenable raw material composition usually contains a catalytic amount of a polymerization initiator.
• a thermal polymerization initiator is suitable as the polymerization initiator, and a chemical polymerization initiator and/or a photopolymerization initiator may be used in combination. If necessary, other additives may also be used. Specific examples of the polymerizable monomer, polymerization initiator, and other additives that can be used are the same as those used in the dental hardenable composition manufacturing method described below.
• the kneading ambient pressure is less than 1.0 (Pa)
• the pressure will be so low that the polymerizable monomer and secondary raw material powder particles will scatter, making it impossible to knead the curable raw material composition
• the pressure will be so high that the polymerizable monomer will not penetrate into the secondary raw material powder particles, making it impossible to knead the curable raw material composition.
• the kneading ambient pressure be 100 to 35,000 (Pa), particularly 1,000 to 33,000 (Pa).
• Such control of the atmospheric pressure during kneading can be performed by using a kneading machine such as a planetary mixer that can perform kneading in a sealable space that is pressure-resistant, and after each raw material to be kneaded (is charged), the pressure in the space is increased to a predetermined pressure using a vacuum pump or the like, then the space is sealed and kneading is started.
• a vacuum hood and a vacuum shaft seal this can be suitably performed using a two-shaft planetary kneading device such as a planetary mixer that allows kneading in a reduced pressure state.
• the temperature during kneading is not particularly limited, but is preferably 25°C to 60°C, and more preferably 30°C to 40°C.
• the curable raw material composition is cured to obtain a lump of a composite material in which low-crystalline rare earth metal fluoride particles are dispersed in a resin matrix.
• the curable raw material composition obtained in the kneading step is preferably cured by heat treatment.
• the heating temperature is preferably 50 to 500°C, more preferably 80 to 200°C.
• the heat treatment time is preferably 10 to 500 minutes, more preferably 20 to 200 minutes.
• the aggregates are pulverized and then the particle size is adjusted so that the average particle size is 3 to 110 ⁇ m.
• the method for pulverizing the aggregates is not particularly limited, and for example, a ball mill or the like can be used.
• a ball mill is used as the pulverization method, it is preferable to use zirconia as the material of the balls used for pulverization in order to reduce contamination.
• the particle size of the zirconia balls used is preferably 1 to 100 mm, and more preferably 10 to 50 mm.
• the pulverization time in the ball mill is preferably 5 to 120 minutes, and more preferably 30 to 90 minutes.
• the particle size adjustment carried out after the above-mentioned pulverization step can be suitably carried out using a sieve with mesh sizes appropriate for the desired particle size (average particle diameter).
• the organic-inorganic composite particles (particle bodies) obtained after pulverization may be subjected to various surface treatments, coating treatments, external additive treatments, etc., as necessary.
• Dental hardenable composition manufacturing method (1) Overview of the dental hardenable composition manufacturing method
• the dental hardenable composition manufacturing method is mainly characterized in that a predetermined amount of a specific X-ray opaque filler manufactured by the present X-ray opaque filler manufacturing method is mixed into a dental hardenable composition used as a conventionally known structural color CR (existing structural color dental hardenable composition).
• the specific X-ray opaque filler is composed of organic-inorganic composite particles (particle bodies) using a resin material such that
• the existing structural color dental curable composition means a dental curable composition containing a predetermined amount of each of a polymerizable monomer, an inorganic filler, and a polymerization initiator, as already explained as the prior art, in which a filler containing spherical inorganic particles having a specific average particle size and particle size distribution, i.e., one or more "spherical particle groups of the same particle size" (G-PID), is used, and the refractive index of the spherical inorganic particles is made higher than the refractive index of the resin part that becomes the matrix when cured, specifically, when the amount of the polymerizable monomer contained in the dental curable composition is 100 parts by mass, the following conditions 1 to 3 are satisfied, and a structural color that develops in a predetermined color tone independent of the angle of incidence of light is expressed by light interference, scattering, etc.
• a filler containing spherical inorganic particles having a specific average particle size and particle size distribution
• the aggregate is made of inorganic spherical particles having a predetermined average primary particle diameter within the range of 100 to 1000 nm, and the individual inorganic spherical particles constituting the aggregate are substantially made of the same material, and the aggregate contains one or more "spherical particle groups of the same particle diameter" (G-PID) in total: 10 to 1500 parts by mass, in which 90% or more of the total number of particles in the number-based particle size distribution of the aggregate are present within a range of 5% around the predetermined average primary particle diameter; and a polymerization initiator: 0.01 to 0.5 parts by mass.
• G-PID spherical particle groups of the same particle diameter
• each "spherical particle group of the same diameter” is expressed as G-PID m (where m is 1 when a is 1, and is a natural number from 1 to a when a is 2 or more) in order of decreasing average primary particle diameter, when a is 2 or more, the materials constituting the individual particles of each G-PID m may be different from each other, and in that case, the average primary particle diameters of each G-PID m differ from each other by 25 nm or more.
• a specific X-ray opaque filler manufactured by the present X-ray opaque filler manufacturing method which is composed of 100 parts by mass of a polymerizable monomer; 10 to 1,500 parts by mass of the one or more "same particle size spherical particle groups" ( G-PID) in total; 1 to 100 parts by mass of an organic-inorganic composite particle (particle body) using a resin material such that
• the dental curable composition manufactured by the present dental curable composition manufacturing method is capable of imparting high X-ray opacity to the cured product without impairing the excellent features of existing structural color dental curable compositions, namely, "when used as a CR, (i) since no dye substance or pigment substance is used, the problem of discoloration over time after treatment is unlikely to occur, (ii) a structural color of a specific color tone independent of the angle of incidence of light is expressed depending on the average particle size of the spherical inorganic particles used, and in particular, when spherical inorganic particles having an average primary particle size of 230 to 350 nm are used, it can be colored in a yellow to red color similar to the color of dentin, and further, (iii) since the cured product has a moderate transparency, it is easy to harmonize with the color of the tooth to be restored, and therefore, it is possible to perform restoration of an appearance close to
• Such characteristics are due to the fact that the structural color expression state in the hardened product is almost equivalent to that of a hardened product of an existing structural color dental hardenable composition (also called a base existing structural color dental hardenable composition) that does not contain a specific X-ray opaque filler or a filler that adversely affects the expression of structural color.
• an existing structural color dental hardenable composition also called a base existing structural color dental hardenable composition
• Such properties can be confirmed by comparing the spectral reflectance ratio SR 1 /SR 2 of the hardened product of the dental hardenable composition obtained by the present dental hardenable composition manufacturing method and the hardened product of the base existing structural color dental hardenable composition.
• SR 1 and SR 2 refer to the maximum spectral reflectance (SR 1 ) in the wavelength range of 600 nm or more and 750 nm or less (yellow to red range) and the maximum spectral reflectance (SR 2 ) in the wavelength range of 400 nm or more and 500 nm or less (blue range) in a spectral reflectance curve measured against a black background using a color difference meter for a 1 mm-thick cured body obtained by curing the dental curable composition , and the smaller the spectral reflectance ratio, the more blue the structural color (colored light) of the cured body is, and the larger the spectral reflectance ratio, the more reddish the structural color (colored light) of the cured body is.
• the average primary particle size of the G-PID to be blended is usually controlled so that the hardened composition will exhibit a desired structural color (giving a desired spectral reflectance ratio: SR 1 /SR 2 ratio).
• the spectral reflectance ratio is usually set to a range of 0.9 to 1.5.
• the dental hardenable composition produced by this dental hardenable composition production method is made by blending a specific X-ray opaque filler into the base existing structural color dental hardenable composition to give the hardened product high X-ray opacity, yet the spectral reflectance ratio is difficult to change, and it is possible to maintain a spectral reflectance ratio of, for example, 0.9 or more even without blending a color-matching agent such as a pigment.
• the dental curable composition produced by the dental curable composition production method can provide a cured product having a contrast ratio C of, for example, 0.20 to 0.50, preferably 0.25 to 0.45.
• the contrast ratio C is defined as the ratio Yb/Yw between Yb , which is the Y value measured against a black background using a color difference meter for a 1 mm-thick cured product sample, and Yw , which is the Y value measured against a white background, and serves as an index of the transparency of the cured product of the dental curable composition.
• the smaller the contrast ratio the higher the transparency.
• the contrast ratio of the hardened body of the dental hardenable composition is less than 0.20, the brightness (shade of color) of the hardened body at the filling site will be low, the transmitted light at the filling site will be strong, and the colored light from the hardened body will be weak. This makes it difficult to obtain the color matching effect of the present invention when filling a deep cavity (e.g., class IV cavity).
• the contrast ratio of the hardened body exceeds 0.50, the brightness of the hardened body will be high and it will be difficult for light to penetrate to the underlying restoration, so the reflected light on the surface of the filling site will be strong and the colored light from the hardened body will be weak, making it difficult to obtain the color matching effect of the present invention.
• the contrast ratio C of the hardened body of the hardenable composition is in the range of 0.20 to 0.50, and more preferably in the range of 0.20 to 0.45.
• the present invention is not limited to any theory, but the inventors presume that the reason why high X-ray contrast can be obtained with a small amount of low-crystalline rare earth metal fluoride powder is that when low-crystalline rare earth metal fluoride powder is blended as is, the individual particles, which have weak X-ray opacity (small), are uniformly dispersed, causing the overall X-ray opacity to become blurred, whereas blending it as organic-inorganic composite particles causes the "regions with locally high density of rare earth metal fluoride particles" (regions with locally high X-ray opacity) to be uniformly dispersed (scattered) throughout, making them clearly distinguishable when viewed as an image.
• the particles will get between the particles of the same particle diameter spherical particle group (G-PID) that forms an ideal periodic structure, disrupting the periodic structure.
• G-PID particle diameter spherical particle group
• the absolute number of particles is reduced compared to when the low-crystalline rare earth metal fluoride powder is mixed as is, and the frequency of disrupting the periodic structure of the G-PID is reduced.
• the particle size increases due to the organic-inorganic composite, making it less likely to get between the periodic structures of the G-PID.
• the low-crystalline rare earth metal fluoride powder into organic-inorganic composite particles it is less likely to disrupt the periodic structure formed by the G-PID, and it is thought that there is no adverse effect on the desired structural color.
• the raw materials and blending amounts, etc. used in the present dental curable composition manufacturing method are basically the same as the components and blending amounts, etc. in the existing structural color dental curable compositions disclosed in Patent Documents 1 and 2, except that a specified amount of a specific X-ray opaque filler is blended. Therefore, here, these will be briefly explained, and then the dental curable composition of the present invention will be described.
• (2-1) Polymerizable Monomer As the polymerizable monomer, any of those usable in conventional dental hardenable compositions can be used without any particular limitation, but it is preferable to use a (meth)acrylate-based monomer.
• Specific examples of (meth)acrylate-based monomers that can be suitably used include methyl (meth)acrylate, glycidyl (meth)acrylate, 2-cyanomethyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, allyl (meth)acrylate, 2-hydroxyethyl mono(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate (3G), nonaethylene glycol di(meth)acrylate, propylene ...
• polymerizable monomer examples include acrylate, dipropylene glycol di(meth)acrylate, 2,2-bis[4-(meth)acryloyloxyethoxyphenyl]propane, 2,2-bis[4-(meth)acryloyloxyethoxyethoxyphenyl]propane, 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. Two or more of these polymerizable monomers can be used in appropriate combination.
• bifunctional to tetrafunctional polymerizable monomers are preferred due to their high polymerizability and the particularly high mechanical strength of the cured body, and from the viewpoint of the transparency of the cured body of the curable composition, it is more preferable to use any one of 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), or a combination of two or more of these polymerizable monomers.
• ethylene glycol di(meth)acrylate 2,2-bis[4-(meth)acryloyloxyethoxyphenyl]propane
• the type and amount of the polymerizable monomer so that the refractive index of the polymerizable monomer composition (mixture) at 25°C for the sodium d line is in the range of 1.38 to 1.55. That is, when a silica-titanium group element oxide composite oxide, which has an easily adjustable refractive index, is used as the inorganic spherical particle, the refractive index at 25°C for the sodium d line is in the range of about 1.45 to 1.58 depending on the silica content.
• 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 about 1.40 to 1.57, making it easy to satisfy the above condition.
• the refractive index of the polymerizable monomer or the hardened body of the polymerizable monomer can be determined at 25°C using an Abbe refractometer.
• G-PID Group of spherical particles with the same particle size: G-PID
• the uniform particle diameter spherical particle group: G-PID is composed of an aggregate of inorganic spherical particles having a predetermined average primary particle diameter in the range of 100 nm or more and 1000 nm or less (100 to 1000 nm), and the aggregate is The individual inorganic spherical particles are composed of substantially the same material, and in the number-based particle size distribution of the aggregate, 90% or more of the total number of particles are within the range of 5% around the predetermined average primary particle diameter. It means the collection that is present in the range.
• the average primary particle diameter of inorganic spherical particles here means the average value obtained by taking a photograph of G-PID with a scanning electron microscope, selecting 100 or more particles observed within a unit field of view of the photograph, and determining the primary particle diameter (maximum diameter) of each.
• spherical means that it is sufficient that it is approximately spherical, and does not necessarily have to be a perfect sphere.
• a photograph of G-PID is taken with a scanning electron microscope, the maximum diameter of each particle (100 or more) within the unit field of view is measured, and the average uniformity obtained by dividing the particle diameter in the direction perpendicular to the maximum diameter by the maximum diameter is 0.6 or more, more preferably 0.8 or more.
• the average primary particle diameter of G-PID from which a suspension of primary particles is obtained by ultrasonic irradiation closely matches the particle diameter (D50p value) that is 50% cumulative from the small diameter side, which is obtained from the number particle size distribution measured for the suspension using a particle size distribution meter.
• each constituent particle of G-PID has a specific short-range order structure and is dispersed in a resin matrix, so that diffraction interference occurs in accordance with the Bragg condition, light of a specific wavelength is emphasized, and colored light of a color tone according to the average primary particle diameter is generated (structural color is expressed). That is, in order for structural color to be expressed, 90% (number) or more of the inorganic spherical particles constituting G-PID must be present within a range of 5% around the average primary particle diameter.
• the ratio (%) of the "number of particles present within a range of 5% around the average primary particle diameter" to the “total number of particles constituting G-PID" is defined as the "5% particle content”
• the 5% particle content must be 90% or more.
• the average primary particle diameter of the inorganic spherical particles constituting G-PID must be within the range of 100 to 1000 nm. When spherical particles with an average primary particle size smaller than 100 nm are used, the phenomenon of visible light interference is unlikely to occur, and structural color is also unlikely to appear.
• the average primary particle diameter is 230-800 nm, a yellow to red structural color (colored light) is likely to be produced, and when the average primary particle diameter is less than 150-230 nm, a blue structural color (colored light) is likely to be produced. Because G-PID produces a yellow to red structural color (colored light) that is preferred as a dental filling and restorative material, the average primary particle diameter is preferably 230-800 nm, more preferably 240-500 nm, and particularly preferably 260-350 nm.
• the resulting colored light is yellowish, which is useful for repairing teeth that fall into the B-type (red-yellow) category in the shade guide (VITA Classical, manufactured by VITA), and is particularly useful for repairing cavities formed from the enamel to the dentin.
• the resulting colored light is reddish, which is useful for restoring teeth in the A-type (reddish brown) category in the shade guide (VITA Classical, manufactured by VITA), and is particularly useful for restoring cavities formed from enamel to dentin.
• an embodiment using only G-PID with an average primary particle size in the range of 260 to 350 nm is most preferable because it has good compatibility with a wide range of restored teeth of various colors.
• the resulting colored light is blued, and for cavities formed from enamel to dentin, the color compatibility with the tooth structure is likely to be poor, but it is useful for restoring enamel, and is particularly useful for restoring incisal edges.
• the G-PID used may be one type or multiple types.
• the number of G-PIDs contained: a is preferably 1 to 5, particularly preferably 1 to 3, and most preferably 1 or 2.
• the average primary particle diameters of the respective G-PIDs must differ from each other by 25 nm or more.
• each G-PID is expressed as G-PID m (where m is 1 when a is 1, and is a natural number from 1 to a when a is 2 or more) in order of decreasing average primary particle diameter
• each G-PID can be dispersed in a form like an aggregate of a small number of inorganic spherical particles, not exceeding about 20, which is aggregated with a very loose binding force, and thus it is possible to disperse with a short-range ordered structure that can express a structural color for each G-PID, and as a result, it is possible to express a unique structural color (according to the average primary particle size) for each G-PID.
• the particle size distribution of the inorganic spherical particles as a whole becomes broad, and probably the inorganic spherical particles constituting each G-PID are mutually substituted and dispersed, which is probably due to the same phenomenon as when an aggregate of a single inorganic spherical particle that does not satisfy the condition of the number-based particle size distribution is used, making it difficult to express a structural color.
• the average primary particle size d m of each G-PID m differs from each other by 30 nm or more, particularly 40 nm or more.
• each G-PID has an extremely sharp particle size distribution, and since there are differences in the average primary particle diameter as described above, the particle size distributions of each G-PID are unlikely to overlap, and even if there is some overlap, it is possible to confirm the particle size distribution of each G-PID.
• G-PID is formed by agglomerating inorganic spherical particles to form an aggregate particle size.
• the average aggregate particle size of G-PID is preferably within the range of 5 to 200 ⁇ m, and more preferably within the range of 10 to 100 ⁇ m.
• the average aggregate particle size of G-PID refers to the median diameter of volume statistics obtained based on the measurement results using a particle size distribution meter using the laser diffraction-scattering method.
• the inorganic spherical particles constituting G-PID are not particularly limited in material as long as they satisfy the above-mentioned conditions for constituting G-PID.
• materials that can be suitably used include amorphous silica, silica-titanium group element oxide composite oxide particles (silica-zirconia, silica-titania, etc.), quartz, alumina, barium glass, strontium glass, lanthanum glass, fluoroaluminosilicate glass, ytterbium fluoride, zirconia, titania, colloidal silica, etc.
• silica-titanium group element oxide composite oxide particles sica-zirconia, silica-titania, etc.
• quartz alumina
• barium glass strontium glass
• lanthanum glass fluoroaluminosilicate glass
• ytterbium fluoride zirconia
• titania colloidal silica, etc.
• the silica-titanium group element oxide composite oxide particles refer to a composite oxide of silica and an oxide of a titanium group element (group 4 element of the periodic table), and the refractive index for sodium d-line at 25°C can be changed in the range of about 1.45 to 1.58 depending on the content of silica.
• Specific examples of silica-titanium group element oxide composite oxide particles include silica-titania, silica-zirconia, and silica-titania-zirconia, but it is preferable to use silica-zirconia.
• the composite ratio in silica-zirconia is not particularly limited, but from the viewpoint of imparting sufficient X-ray opacity and setting the refractive index in the preferred range described below, it is preferable that the silica content is 70 to 95 mol% and the titanium group element oxide content is 5 to 30 mol%. It should be noted that these silica-titanium group element oxide composite oxide particles can also be composites of metal oxides other than silica and titanium group element oxides, as long as the amount is small. Specifically, alkali metal oxides such as sodium oxide and lithium oxide may be contained in an amount of up to 10 mol%.
• the method for producing such silica-titanium group element oxide composite oxide particles is not particularly limited, but in order to obtain spherical fillers, for example, the so-called sol-gel method is preferably used, in which 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 a reaction product.
• These inorganic spherical particles made of silica-titanium group element oxide composite oxides are preferably surface-treated with a silane coupling agent such as ⁇ -methacryloyloxyalkyltrimethoxysilane or hexamethyldisilazane.
• n (MX) ⁇ n (G-PIDm) If the above relationship is not satisfied, even if a structural color is expressed, light of short wavelengths is likely to be scattered in the resin matrix in the hardened product of the dental hardenable composition, making it difficult to confirm the expressed structural color.
• the difference ⁇ n between n (G-PIDm) and n (MX) is set to 0. It 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.
• the refractive index (n (MX) ) of the cured product that becomes the resin matrix can be set in the range of 1.40 to 1.57.
• the refractive index (n (G-PIDm) ) of the silica-titanium group element oxide composite oxide can be changed in the range of about 1.45 to 1.58 by changing the silica content. Therefore, for example, by utilizing these relationships, ⁇ n can be easily set in the suitable range.
• an organic-inorganic composite filler that does not contain uniform-particle-size spherical particle groups other than the one type of uniform-particle-size spherical particle group (i.e., an organic-inorganic composite filler that contains only a single G-PID).
• the organic-inorganic composite filler means a powder consisting of a composite in which an inorganic filler is dispersed in an (organic) resin matrix, or a filler consisting of an aggregate in which primary particles of an inorganic filler are bound together by an (organic) resin.
• the organic-inorganic composite filler for example, when three types of G-PIDs having different average primary particle sizes, namely G-PID 1 , G-PID 2 , and G-PID 3 , are contained, all or a part of at least one of them is blended as an "organic-inorganic composite filler containing only a single G-PID".
• G-PID 1 is blended in the curable composition as an organic-inorganic composite filler containing only G-PID 1 (composite filler 1), only G-PID 1 is contained in the composite filler 1, and a short-range ordered structure that exhibits the structural color of G-PID 1 is realized, so that the structural color of G-PID 1 is reliably exhibited even in a composite material obtained by curing the curable composition.
• the refractive index at 25°C of the resin matrix of the organic-inorganic composite filler for the sodium d line: n '(F-MX) must be smaller than the refractive index at 25°C of the inorganic spherical particles for the sodium d line (n (G-PIDm) ).
• ⁇ n' which is the difference between n (G-PIDm) and n '(F-MX)
• ⁇ n' is preferably in the same range as the ⁇ n described above.
• the refractive index at 25°C of the hardened body of the polymerizable monomer in the structural color dental hardenable composition of the present invention (specifically, the hardened body of a composition consisting of a polymerizable monomer and a small amount of polymerization initiator) at sodium d line: n (MX) and the absolute value of the difference between n'( F-MX) and n'(F-MX) ,
• , must be 0 to 0.1.
• the amount of inorganic spherical particles mixed into the organic-inorganic composite filler is preferably 30 to 95% by mass, and particularly preferably 40 to 90% by mass.
• the average particle size is not particularly limited, but from the viewpoint of improving the mechanical strength of the composite material and the operability of the curable composition, the median size determined based on the results of measurements using a particle size distribution meter using a laser diffraction-scattering method is preferably 2 to 100 ⁇ m, more preferably 5 to 50 ⁇ m, and even more preferably 5 to 30 ⁇ m.
• the total amount of G-PID used is 10 to 1500 parts by mass relative to 100 parts by mass of the polymerizable monomer. It is preferably 50 to 1500 parts by mass, more preferably 100 to 1500 parts by mass, because the resulting composite material has appropriate transparency and is highly effective in expressing a structural color.
• the content of each G-PID may be appropriately set so that the total content falls within the above range, taking into consideration the color tone of the structural color due to each G-PID and the desired color tone of the composite material.
• (2-7) Polymerization initiator As the polymerization initiator in the dental curable composition of the present invention, since the composition is often cured in the oral cavity, it is preferable to use a chemical polymerization initiator and/or a photopolymerization initiator, and it is more preferable to use a photopolymerization initiator because there is no need for a mixing operation. These polymerization initiators may be used alone, but two or more types may be mixed and used.
• the amount of the polymerization initiator to be blended may be selected according to the purpose, and is usually 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the polymerizable monomer.
• photopolymerization initiators examples include benzoin alkyl ethers, benzil ketals, benzophenones, ⁇ -diketones, thioxanthone compounds, and bisacylphosphine oxides.
• a reducing agent is often added to the photopolymerization initiator. Examples of reducing agents include aromatic amines, aliphatic amines, aldehydes, and sulfur-containing compounds. Furthermore, trihalomethyltriazine compounds, aryliodonium salts, and the like can also be added as necessary.
• thermal polymerization initiators include peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxydicarbonate, and diisopropylperoxydicarbonate; azo compounds such as azobisisobutyronitrile; boron compounds such as tributylborane, tributylborane partial oxide, sodium tetraphenylborate, sodium tetrakis(p-fluorophenyl)borate, and triethanolamine tetraphenylborate; barbituric acids such as 5-butylbarbituric acid and 1-benzyl-5-phenylbarbituric acid; and sulfinic acid salts such as sodium benzenesulfinate and sodium p-toluenesulfinate.
• peroxides such as benzoyl peroxide,
• the specific X - ray opaque filler must be 0 to 0.1. If this condition is not satisfied, the transparency of the cured product of the structural color dental hardenable composition of the present invention is significantly reduced.
• the specific X-ray opaque filler to be mixed with the structural color dental hardenable composition of the present invention has the same composition or a similar composition as the polymerizable monomer in the structural color dental hardenable composition of the present invention as the raw material (matrix resin) of the polymerizable monomer. It is more preferable that
• the amount of the specific X-ray opaque filler used is 1 to 100 parts by mass, preferably 15 to 75 parts by mass, per 100 parts by mass of the polymerizable monomer, calculated as the total mass of the low-crystalline rare earth metal fluoride powder, from the viewpoint of the X-ray opacity, transparency and structural color expression of the cured product. If the amount is less than 1 part by mass (lower limit), sufficient X-ray opacity cannot be obtained, and if the amount is more than 100 parts by mass (upper limit), transparency and structural color expression are significantly reduced.
• G-SFP ultrafine particles
• d 1 average primary particle diameter of G-PID 1
• the shape of the inorganic particles constituting the G-SFP is not particularly limited, and may be amorphous or spherical.
• the lower limit of the average primary particle diameter is usually 2 nm.
• the average primary particle diameter of the G-SFP is preferably 3 to 75 nm, more preferably 5 to 50 nm, because it has little effect on the expression of structural color.
• the average primary particle diameter of G-SFP is preferably 30 nm or more smaller than the average primary particle diameter (d 1 ) of G-PID 1 , more preferably 40 nm or more smaller.
• the material of the inorganic particles constituting G-SFP the same as that of the inorganic spherical particles can be used without any particular limitation.
• G-SFP may be appropriately determined taking into consideration the viscosity of the curable composition, the transparency of the cured body (or the contrast ratio serving as an index thereof), and the like, but is usually 0.1 to 50 parts by mass, and preferably 0.2 to 30 parts by mass, relative to 100 parts by mass of the polymerizable monomer.
• rare earth metal fluoride particles other than the rare earth metal fluoride particles blended as the specific X-ray opaque filler may be included.
• the blending amount of such rare earth metal fluoride particles is preferably 5 parts by mass or less, and more preferably 0 to 3 parts by mass, relative to 100 parts by mass of the polymerizable monomer.
• the blending amount of crystalline rare earth fluoride metal particles having a full width at half maximum of less than 0.3° is preferably 0 to 0.5 parts by mass or less.
• the content of the crystalline rare earth fluoride metal particles having a full width at half maximum of 0.3° or more contained in the specific X-ray opaque filler and the total blending amount of the non-composite particles is 0 to 100 parts by mass, more preferably 0 to 50 parts by mass, relative to 100 parts by mass of the polymerizable monomer.
• additives such as polymerization inhibitors and ultraviolet absorbers can be added within a range that does not impair the effects of the present invention.
• the hardened product of the dental curable composition obtained exhibits structural color without using coloring substances such as pigments. Therefore, although there is no particular need to add a pigment that may discolor over time, the addition of a pigment is not denied, and a pigment may be added to the extent that it does not interfere with colored light due to interference from the spherical filler.
• a pigment may be added in an amount of about 0.0005 to 0.5 parts by mass, preferably about 0.001 to 0.3 parts by mass, per 100 parts by mass of the polymerizable monomer.
• the method for producing a dental hardenable composition includes a mixing step in which all of the raw material components are weighed out and mixed in predetermined amounts.
• the mixing step it is preferable that the mixture obtained in the mixing step is prepared by a method in which mixing conditions are adopted that have been confirmed to satisfy the following conditions (I) and (II) in the dispersion state of the inorganic particles in the hardened body obtained by hardening the mixture.
• the x-axis is a dimensionless number (r/ r0 ) obtained by dividing the distance from the center of any inorganic spherical particle dispersed in the cured body by the average particle size r0 of all the inorganic spherical particles dispersed in the cured body
• the y-axis is the radial distribution function g(r)
• the nearest inter-particle distance r1 which is defined as the r corresponding to the peak top of the peak closest to the origin among the peaks appearing in the radial distribution function graph, is a value that is 1 to 2 times the average particle size r0 of all the inorganic spherical particles dispersed in the cured body of the mixture.
• the radial distribution function g(r) is a well-known function for calculating the probability of the presence of another particle at a point a distance r away from any given particle, and is defined by the following formula (1).
• ⁇ > represents the average particle density of the particles in the plane
• dn represents the distance between two circles having radii r and r+dr, each of which has a center on an arbitrary particle in the plane.
• da represents 2 ⁇ r ⁇ dr, which is the area of the region.
• the radial distribution function g(r) is generally represented by a radial distribution function graph with distance r on the x-axis (distance axis) and the value of g(r) at r (the calculation result from the above formula (1)) on the y-axis (vertical axis), or by a radial distribution function graph with a dimensionless number normalized by dividing r by the average particle diameter of the particles on the distance axis and the value of g(r) at r corresponding to the x-axis value (the calculation result from the above formula) on the y-axis (vertical axis).
• ⁇ >, dn, and da can be determined as follows. First, the mixture is hardened, and a plane (observation plane) on which the dispersion state of the inorganic spherical particles inside the hardened material can be observed is exposed on the surface by means of polishing the surface of the obtained hardened material.
• the observation plane is observed by a scanning electron microscope, and a microscopic image of a region containing at least 500 inorganic spherical particles in the plane is obtained. Then, the obtained scanning electron microscope image is used to obtain the coordinates of the inorganic spherical particles in the region using image analysis software (for example, "Simple Digitizer ver. 3.2" free software).
• image analysis software for example, "Simple Digitizer ver. 3.2" free software.
• the average particle density ⁇ > (unit: particles/cm2) can be determined by selecting one coordinate of any inorganic spherical particle from the obtained coordinate data, drawing a circle with a radius of distance r centered on the selected inorganic spherical particle and including at least 200 inorganic spherical particles, and counting the number of inorganic spherical particles included within the circle .
• dr when the average particle diameter of the inorganic spherical particles is represented by r0 , dr is set so that its length is about r0 /100 to r0 /10, and one arbitrarily selected inorganic spherical particle is taken as the central particle, and dn can be determined by counting the number of inorganic spherical particles contained within the region between a circle whose radius is the distance r from the center and a circle of radius r+dr having the same center as the circle. Furthermore, da, which is the area of the region between the two circles, is determined as 2 ⁇ r ⁇ dr based on the length of dr that is actually set.
• the x-axis is a dimensionless number (r/r 0 ) obtained by dividing the distance r from the center of any inorganic spherical particle dispersed in the hardened body by the average particle diameter r 0 of all inorganic spherical particles dispersed in the composite material
• the y-axis is a radial distribution function g(r ) representing the probability that other inorganic spherical particles are present at a point distant by a distance r from the center of any inorganic spherical particle.
• the radial distribution function graph shows the relationship between r/r 0 and g(r) corresponding to r at that time.
• r 1 /r 0 is 1.0 to 2.0, preferably 1.0 to 1.5.
• the minimum value of the radial distribution function g(r) between the nearest interparticle distance r 1 and the next nearest interparticle distance r 2 is a value of 0.56 to 1.10, preferably a value of 0.56 to 1.00.
• the mixing step it is preferable to mix the inorganic spherical particles (G-PID) as an organic-inorganic composite filler having a particle diameter of 5 to 50 ⁇ m, preferably 5 to 30 ⁇ m, or as aggregated particles having a particle diameter of 5 to 200 ⁇ m, preferably 10 to 100 ⁇ m.
• G-PID inorganic spherical particles
• a defoaming method it is preferable to adopt a method of defoaming under reduced pressure because it is possible to remove air bubbles in a short time even from a composition with high viscosity.
• inorganic spherical particles are mixed while paying attention to such points, in principle, the above conditions will be satisfied if sufficient stirring is performed, but even if it is judged to be in a uniform state by visual inspection, the stirring may be insufficient from the viewpoint of satisfying the above conditions, and it is difficult to determine the end point. Therefore, it is preferable to carry out the mixing step after determining the end point by the above method (a) or (b) or while determining the end point.
• a known polymerization means may be appropriately adopted according to the polymerization initiation mechanism of the polymerization initiator used. Specifically, light irradiation by a light source such as a carbon arc, a xenon lamp, a metal halide lamp, a tungsten lamp, a fluorescent lamp, sunlight, a helium cadmium laser, an argon laser, heating using a heating polymerization device, or a combination of these methods may be used without any restrictions.
• a light source such as a carbon arc, a xenon lamp, a metal halide lamp, a tungsten lamp, a fluorescent lamp, sunlight, a helium cadmium laser, an argon laser, heating using a heating polymerization device, or a combination of these methods may be used without any restrictions.
• the irradiation time varies depending on the wavelength and intensity of the light source, and the shape and material of the cured body, so it may be determined in advance by preliminary experiments.
• the curable composition of this embodiment is used for dental purposes, it is generally preferable to adjust the blending ratio of various components so that the irradiation time is in the range of about 5 to 60 seconds.
• Polymerizable monomer UDMA 1,6-bis(methacrylethyloxycarbonylamino)-2,2,4-trimethylhexane
• 3G Triethylene glycol dimethacrylate.
• 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.
• M2 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.
• the refractive indices of the curable components M1 and M2 before and after curing, measured according to the method described below, are shown in Table 1.
• ⁇ Average primary particle diameter 40nm
• ⁇ Average secondary particle diameter 0.6 ⁇ m
• Refractive index 1.55
• the full width at half maximum of the peak (111) plane (peak observed around 2 ⁇ 28°) having the greatest intensity of YbF3 in X-ray diffraction measurement: 0.17°
• the surface was treated with an agent (methacrylic acid-3-(trimethoxysilyl)propyl-3-(methacryloyloxy)propyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.)).
• ⁇ Average primary particle diameter 260nm Refractive index: 1.515
• Uniformity 0.90 ⁇ 5% particle content: 92%
• the uniformity refers to the ratio (D2/D1) of the maximum diameter D1 of a spherical particle to the particle diameter D2 in a direction perpendicular to the maximum diameter D1.
• the average primary particle diameter and the refractive index are expressed by The value was measured according to the method described below.
• the average primary particle diameter of rare earth metal fluoride particles and G-PID was determined using a scanning electron microscope according to the following procedure. First, a measurement sample was prepared by fixing rare earth metal fluoride particles or G-PID on a sample stage with carbon paste and then subjecting it to conductive treatment (platinum vapor deposition). Next, this measurement sample was observed at a magnification of 100,000 times with an electron microscope (JSM-7800F PRIME, manufactured by JEOL Ltd.), and the average particle diameter of 100 primary particles in the obtained observation image was determined as the average primary particle diameter. In addition, for G-PID, the average uniformity was determined based on the primary particles (100 particles) in the obtained observation image.
• the average secondary particle size of rare earth metal fluoride particles was determined by particle size distribution measurement in the following procedure. 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 this suspension with ultrasonic waves, a particle size distribution measurement was performed using a particle size distribution meter (LS13-320, manufactured by BECKMAN COULTER) to obtain a volumetric particle size distribution. Then, the particle size (D50v value) that is 50% cumulative from the small diameter side of the volumetric particle size distribution was determined as the average secondary particle size of the rare earth metal fluoride particles.
• LS13-320 particle size distribution meter
• the number particle size distribution was obtained by particle size distribution measurement in the following procedure. First, a suspension was prepared by suspending 0.1 g of powder (G-PID) in 10 mL of ion-exchanged water. Next, while irradiating this suspension with ultrasonic waves, particle size distribution was measured using a particle size distribution meter (LS13-320, manufactured by BECKMAN COULTER) to obtain the number particle size distribution. Then, the particle size (D50p value) at 50% cumulative from the small diameter side of the number particle size distribution was obtained, and it was in good agreement with the average primary particle size obtained by observation with an electron microscope.
• a particle size distribution meter LS13-320, manufactured by BECKMAN COULTER
• Reference Examples (Reference Examples 1 to 13 and Reference Comparative Examples 1 to 5)
• small amounts of the specific radiopaque filler and other radiopaque fillers (which do not need to be manufactured using this radiopaque filler manufacturing method) were prepared using the above-mentioned raw materials, and these were evaluated, as well as the preparation and evaluation of hardenable compositions containing these radiopaque fillers.
• the slurry after dispersion was concentrated using a rotary evaporator at a bath temperature of 50°C to obtain a powder. This powder was dried under vacuum at 80°C for 15 hours to obtain mechanochemically treated rare earth metal fluoride powder.
• the average primary particle size was measured by the method described in 2.
• Measurement method of full width at half maximum S A measurement sample was prepared by removing coarse particles from the powdered material to be subjected to X-ray diffraction measurement using a sieve. Next, the measurement sample was filled into the sample stage of an X-ray diffraction device (Smartlab, manufactured by Rigaku Corporation) and X-ray diffraction measurement was performed to obtain an X-ray diffraction pattern (chart) with the horizontal axis representing 2 ⁇ (°) and the vertical axis representing diffraction intensity.
• X-ray diffraction pattern chart
• CuK ⁇ rays were used as the X-rays for the X-ray diffraction measurement.
• the full width at half maximum C of the X-ray opaque filler can be obtained in the same manner.
• the obtained cured product and zirconia balls (diameter: 25 mm) were put into a zirconia pot and subjected to a rotary pulverization process for 60 minutes to obtain a pulverized product of the cured product.
• the pulverized product was removed from the pulverized product using a stainless steel sieve with a mesh size of 45 ⁇ m to obtain a radiopaque filler CF-1 (a specific radiopaque filler).
• the average particle size and full width at half maximum C of the radiopaque filler CF-1 were measured. The results are shown in Table 3.
• CF-1 to CF-4 and CF-1a to CF-1i other than RCF-1 obtained in Production Example 5 are specific X-ray impermeable fillers.
• the average particle size of the radiopaque filler was determined by particle size distribution measurement using the following procedure. That is, first, a suspension was prepared by suspending 0.1 g of powder (radiopaque filler) in 10 mL of ethanol. Next, while irradiating this suspension with ultrasound, particle size distribution measurement was performed using a particle size distribution analyzer (LS13-320, manufactured by BECKMAN COULTER) to obtain a volumetric particle size distribution. The particle size (D50v value) that is 50% cumulative from the small diameter side of the volumetric particle size distribution was determined as the average particle size of the radiopaque filler. The full width at half maximum C was measured in the same manner as the full width at half maximum S. The results are also shown in Table 3.
• the X-ray contrast of the cured product of the curable composition was measured by the following procedure. First, the curable composition was filled into a through hole (diameter 15 mm, through hole length 1.0 mm) provided in a polytetrafluoroethylene mold, and then both ends of the through hole were sealed while being pressed with a polypropylene film. Next, light was irradiated in a state in which a dental light irradiator (TOKUSO POWER LIGHT, manufactured by Tokuyama Corporation) was placed so as to be in close contact with the surface of the polypropylene film sealing the through hole opening.
• a dental light irradiator TOKUSO POWER LIGHT, manufactured by Tokuyama Corporation
• the positions of light irradiation were 5 positions (1 position at the center of the through hole and 4 positions inside the outer edge of the through hole) on one opening side of the through hole, and 5 positions (1 position at the center of the through hole and 4 positions inside the outer edge of the through hole) on the other opening side. Then, light irradiation was performed for 20 seconds at each light irradiation position to obtain a cured product. The thickness of the obtained cured product was confirmed using a micrometer. The cured product having a thickness of 1.0 mm ⁇ 0.1 mm was used as a test piece for measuring X-ray contrast properties.
• an X-ray film (ultra-sensitive dental X-ray film, Kodak) was placed on a 2.0 mm thick lead sheet, and then a test piece and an aluminum step wedge with five different thicknesses (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.
• the test piece and the step wedge were irradiated with X-rays from a height of 40 cm from the surface of the X-ray film using an X-ray irradiator (PANPAS-E, YOSHIDA).
• the irradiation conditions were tube voltage: 60 kVp, irradiation time: 0.3 seconds.
• the X-ray film was then developed and printed on photographic paper.
• the optical density of the test piece image and the step wedge image on the photographic paper were then measured.
• a calibration curve was created based on the five thicknesses of the step wedge and the optical densities corresponding to these five thicknesses, and the thickness of the step wedge (i.e., the aluminum material) at which the optical density of the test piece coincided with the optical density of the step wedge was determined based on this calibration curve.
• the aluminum material thickness thus determined was converted to Al%, and used as an evaluation index for X-ray contrast, assuming that the optical density of an aluminum material with a thickness of 1 mm is the standard (100 Al%).
• the transparency of the cured product of the curable composition was measured by the following procedure. 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 product. The thickness of the obtained cured product was confirmed using a micrometer.
• TOKUSO POWER LIGHT manufactured by Tokuyama Corporation
• the cured product with a thickness of 1.0 mm ⁇ 0.1 mm was used as the cured product to be used for evaluating transparency.
• the Y value (a value related to brightness among the tristimulus values of the XYZ color system specified in JIS Z8701) of this cured product was measured using a color difference meter (SE7700, manufactured by Nippon Denshoku Co., Ltd.) under a black background and a white background.
• the contrast ratio C calculated by the following formula was used as an index of transparency for evaluation. Note that the closer the contrast ratio C value is to 1, the more opaque the material is, and the closer the contrast ratio C value is to 0, the more transparent the material is.
• Formula C Yb / Yw
• Yb means the Y value when the cured product is measured against a black background
• Yw means the Y value when the cured product is measured against a white background.
• the spectral reflectance ratio of the cured product of the curable composition was determined by the following procedure. First, the spectral reflectance of the cured product used for the evaluation of transparency was measured in the wavelength range of 380 nm to 780 nm against a black background using a color difference meter (SE7700, manufactured by Nippon Denshoku Co., Ltd.). Then, the spectral reflectance ratio R was calculated based on the following formula.
• SR1 means the maximum reflectance in the yellow to red wavelength region (600 nm to 750 nm)
• SR2 means the maximum reflectance in the blue wavelength region (400 nm to 500 nm).
• the bending strength of the cured body was measured by the following procedure. First, a through hole (length 25 mm, width 2 mm, through hole length 2 mm) provided in a stainless steel mold was filled with a curable composition, and both ends of the through hole were sealed while being pressed with a polypropylene film. Next, light was irradiated in a state in which a dental light irradiator (TOKUSO POWER LIGHT, manufactured by Tokuyama Corporation) was placed so as to be in close contact with the surface of the polypropylene film sealing the opening of the through hole.
• TOKUSO POWER LIGHT manufactured by Tokuyama Corporation
• the positions of light irradiation were three positions on one opening side of the through hole (one position in the center of the through hole and two positions inside the outer edges of both ends of the through hole in the length direction) and three positions on the other opening side (one position in the center of the through hole and two positions inside the outer edges of both ends of the through hole in the length direction). Then, light irradiation was performed for 20 seconds at each light irradiation position to obtain a cured body. The obtained cured product was adjusted with #1500 waterproof abrasive paper to have dimensions of 25 mm ⁇ 2 mm in length, 2 mm ⁇ 0.1 mm in width, and 2 mm ⁇ 0.1 mm in thickness.
• the adjusted dimensions and shape of the cured product were used as a test piece for measuring bending strength.
• the test piece was attached to a precision universal testing machine (Autograph AG5000D, manufactured by Shimadzu Corporation) and the three-point bending strength was measured under the conditions of a branch distance of 20 mm and a crosshead speed of 1 mm/min, to obtain a load-deflection curve.
• the bending strength was then calculated based on the following formula.
• the dispersion state (radial distribution function) of inorganic spherical particles in the curable composition was evaluated by the following procedure.
• cross-section milling was performed using an ion milling device (IM4000, manufactured by Hitachi, Ltd.) at 2 kV for 20 minutes to obtain an observation plane.
• IM4000 ion milling device
• the cured body was fixed on a sample stage with carbon paste, and a measurement sample was prepared in which the observation plane was subjected to a conductive treatment (platinum vapor deposition).
• this measurement sample was observed at a magnification of 10,000 times using an electron microscope (JSM-7800F PRIME, manufactured by JEOL Ltd.), and the coordinates in the observation image were obtained for 1,000 inorganic spherical particles in the obtained observation image using image analysis software (Simple Digiizer ver. 3.2, free software).
• One coordinate of an inorganic spherical particle was arbitrarily selected from the obtained coordinate data, and a circle was drawn with a radius of distance t, which includes at least 200 inorganic spherical particles, centered on the selected inorganic spherical particle, and the number of spherical particles included in the circle was determined, and the average particle density ⁇ > (unit: particles/cm 2 ) was calculated.
• dr is a value of about r 0 /100 to r 0 /10 (r 0 indicates the average primary particle diameter of the inorganic spherical particles), and the number dn of particles included in the region between the circle at the distance r from the central inorganic spherical particle and the circle at the distance r + dr, and the area da of the region were calculated.
• the nearest interparticle distance: r1 which is defined as the r corresponding to the peak top of the peak that is closest to the origin among peaks appearing in a radial distribution function graph, is a value that is 1 to 2 times the average particle size: r0 .
• the minimum value of the radial distribution function g(r) between the next nearest interparticle distance r2 which is defined as the r corresponding to the peak top of the second nearest peak from the origin among the peaks appearing in a radial distribution function graph, and the nearest interparticle distance r1 , is a value of 0.56 or more and 1.10 or less.
• Comparative Reference 1 is an example of a dental hardenable composition based on an existing structural color, and is formulated to have a spectral reflectance of 1.16 so as to show excellent color compatibility (expressing a structural color in the yellow to red range) when used as a CR for restoring cavities formed in dentin or from enamel to dentin, but does not show sufficient X-ray contrast because it does not contain a radiopaque filler.
• Comparative Example 1 is an example in which kneading was performed under atmospheric pressure without reducing pressure.
• the polymerizable monomer did not penetrate into the secondary raw material powder particles, and the mixture did not become a paste, so the curable raw material composition could not be kneaded.
• Comparative Example 2 when the degree of vacuum was high, the powder and polymerizable monomer were scattered during reduction in pressure, so the curable raw material composition could not be kneaded.
• the curable raw material composition could be kneaded.
• the obtained curable raw material composition was cured using a nitrogen pressure heat polymerization apparatus (Poliner, manufactured by Towa Giken Co., Ltd.) to form a mass, which was then heated under nitrogen pressure at 100°C for 30 minutes to form a mass, and the obtained hardened body and zirconia balls (diameter: 25 mm) were placed in a zirconia pot and subjected to a rotary grinding treatment for 60 minutes to obtain a pulverized hardened body. The pulverized body was then removed from the pulverized body using a stainless steel sieve with a mesh size of 45 ⁇ m to obtain a powder (X-ray opaque filler) having an average particle size shown in Table 7.
• a nitrogen pressure heat polymerization apparatus Poly, manufactured by Towa Giken Co., Ltd.

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