X-ray non-penetrating filler, dental X-ray non-penetrating filler, method for manufacturing X-ray non-penetrating filler and hardening composition for dental use

Abstract

This invention provides an X-ray non-penetrating filler capable of imparting necessary X-ray non-penetrating properties to dental curing compositions, without significantly reducing the transparency of the cured body, and enabling aesthetic restoration; a method for manufacturing the same; and a dental curing composition using the X-ray non-penetrating filler. The X-ray non-penetrating filler imparts X-ray non-penetrating properties to the curing composition and its cured body by mixing it into a curing composition containing a polymeric monomer. The filler is composed of any powder selected from the group consisting of a first powder and a second powder. The first powder contains crystalline rare-earth metal fluoride particles as the main component, and the full width at half maximum (FWHM) of the highest intensity peak originating from the crystalline rare-earth metal fluoride particles in the X-ray diffraction pattern is 0.3° or greater. The second powder is obtained by surface treatment of the first powder.

Description

Technical Field

[0001] This invention relates to X-ray non-penetrating fillers, dental X-ray non-penetrating fillers, methods for manufacturing X-ray non-penetrating fillers, and hardening compositions for dental applications. Background Technology

[0002] In dental treatment, after removing caries, a dental filling material is filled into the cavity, and then the hardened material is used to seal the cavity. Such dental filling materials are typically hardened compositions containing polymeric monomers, fillers, and polymerization initiators as main components.

[0003] Inorganic oxide fillers, especially silica-based fillers, are commonly used as fillers in this hardening composition. However, silica-based fillers have low X-ray non-penetration. Therefore, during dental X-ray or CT scans, the hardened material within the cavity is not imaged, making it difficult to determine the treatment site.

[0004] As a method to improve the X-ray non-penetrating properties of hardening compositions for dental use, the use of fillers containing atoms with large atomic numbers is known. For example, Patent Document 1 discloses "a radio-non-penetrating dental restorative material, which is a radio-non-penetrating dental material with a polymeric organic binder, a radio-non-penetrating component, and an inorganic filler used as needed as a base material, wherein the radio-non-penetrating component contains, by weight, 1 to 50 wt% of a fluoride of a rare earth metal (element number 57 to 71) of the periodic system or a mixture of such fluorides."

[0005] [Existing Technical Documents]

[0006] [Patent Documents]

[0007] Patent Document 1: Japanese Patent, Japanese Patent Publication No. 3-17803 Summary of the Invention

[0008] (The problem that the invention aims to solve)

[0009] However, when using X-ray non-penetrating fillers composed of rare earth metal fluorides, as in Patent Document 1... Figure 2 As shown, as the mixing amount increases, the transparency of the hardened body obtained when the dental hardening composition hardens decreases. Therefore, aesthetic restorations are difficult to achieve when sufficient X-ray non-penetration is desired.

[0010] Therefore, the object of the present invention is to provide an X-ray non-penetrating filler that imparts the necessary X-ray non-penetrating properties to dental hardening compositions and does not easily reduce the transparency of the hardened body, enabling aesthetic restoration. Furthermore, the object of the present invention is to provide a dental X-ray non-penetrating filler composed of the above-mentioned X-ray non-penetrating filler, a method for manufacturing the above-mentioned X-ray non-penetrating filler, and a dental hardening composition using the above-mentioned X-ray non-penetrating filler. It should be noted that in the following description, when referred to simply as "hardened body," it refers to a hardened body of a hardening composition or a dental hardening composition; however, for a hardened body obtained by hardening a polymeric monomer, it is referred to as a "hardened body of the polymeric monomer."

[0011] (A solution to the problem)

[0012] The present invention was made to solve the above-mentioned problems. The first aspect of the present invention is an X-ray non-penetrating filler that imparts X-ray non-penetrating properties to a curing composition and its cured body by mixing it into a curing composition containing a polymerizable monomer. The X-ray non-penetrating filler is characterized in that it is composed of any one of the powders selected from the group consisting of a first powder and a second powder, wherein the first powder contains crystalline rare earth metal fluoride particles as the main component, and the full width at half maximum (WWHM) of the highest intensity peak originating from the crystalline rare earth metal fluoride particles in the X-ray diffraction pattern is 0.3° or more, and the second powder is a powder obtained by surface treatment of the first powder.

[0013] In the X-ray non-penetrating filler of the above-described form (hereinafter also referred to as "the X-ray non-penetrating filler of the present invention"), preferably: the first powder is a powder containing at least one particle as the main component, selected from the group consisting of crystalline rare-earth metal fluoride particles with an average primary particle size of 1 to 500 nm as measured by electron microscopy and agglomerated particles of the crystalline rare-earth metal fluoride particles with an average primary particle size of 1 to 500 nm. Furthermore, preferably: the crystalline rare-earth metal fluoride particles are crystalline ytterbium fluoride particles. Preferably: the crystalline rare-earth metal fluoride particles contain at least one particle selected from the group consisting of crystalline lanthanum fluoride particles, crystalline cerium fluoride particles, and crystalline gadolinium fluoride particles. Preferably: the half-width at half-maximum (WWHM) is 0.77° or less. Preferably: the WWHM is 0.47° to 0.68°. Preferably: the WWHM is 0.51° to 0.59°.

[0014] The second aspect of the present invention is a dental X-ray non-penetrating filler (hereinafter also referred to as "the dental X-ray non-penetrating filler of the present invention"), characterized in that it is composed of the X-ray non-penetrating filler of the present invention.

[0015] The third aspect of the present invention is a method for manufacturing the X-ray non-penetrating filler of the present invention, characterized in that: it includes a step of mechanically and chemically treating a raw material powder containing crystalline rare earth metal fluoride particles as the main component and the peak half-width of the crystalline rare earth metal fluoride particles being less than 0.3°, thereby making the full half-width of the crystalline rare earth metal fluoride particles 0.3° or more.

[0016] In the manufacturing method described above (hereinafter also referred to as "the manufacturing method of the present invention"), it is preferable that the mechanochemical treatment is a wet bead milling treatment.

[0017] The fourth aspect of the present invention is a dental hardening composition characterized by containing a polymerizable monomer and the X-ray non-penetrating filler of the present invention.

[0018] In the above-described dental curing composition (hereinafter also referred to as "the dental curing composition of the present invention"), it is preferable that the crystalline rare earth metal fluoride particles are crystalline ytterbium fluoride particles, and the curing body of the polymeric monomer has a refractive index of 1.45 to 1.60 relative to the sodium D line at 25°C.

[0019] In addition, it is preferable to satisfy the following equation (1).

[0020] Equation (1) -0.02≤(n X -n M )≤0.1

[0021] In the above equation (1), n X The term n refers to the refractive index of the crystalline rare-earth metal fluoride particles. M This refers to the refractive index of the hardened form of the polymeric monomer.

[0022] (Invention Effects)

[0023] The X-ray non-penetrating filler of the present invention and the dental X-ray non-penetrating filler of the present invention, unlike existing X-ray non-penetrating fillers composed of rare earth metal fluorides, do not easily reduce the transparency of the hardened body when mixed into a curing composition containing polymeric monomers, even with increased mixing amounts. Therefore, by using the dental curing composition of the present invention containing the X-ray non-penetrating filler of the present invention, aesthetics are excellent, and treatment sites can be easily identified by X-ray imaging. Furthermore, the X-ray non-penetrating filler of the present invention is not limited to dental applications; it can simultaneously achieve transparency and X-ray non-penetrating properties in polymeric curing compositions for various applications such as adhesives or coatings. Further, according to the manufacturing method of the present invention, the X-ray non-penetrating filler of the present invention having the outstanding characteristics described above can be efficiently manufactured using readily available materials. Attached Figure Description

[0024] Figure 1 This is a graph showing the relationship between the peak half-width of crystalline rare earth metal fluoride particles contained in X-ray non-penetrating fillers and the contrast ratio of the hardened body, for Examples 1-11 and Comparative Examples 1-4.

[0025] Figure 2 This is a graph showing the relationship between the mechanochemical treatment time of the raw material powder (crystalline rare earth metal fluoride particles) used in the manufacture of X-ray non-penetrating fillers and the peak half-width of the crystalline rare earth metal fluoride particles contained in the X-ray non-penetrating fillers, for Examples 1-11 and Comparative Examples 1-4.

[0026] Figure 3 This is a graph showing the relationship between the mechanical and chemical treatment time of the raw material powder (crystalline rare earth metal fluoride particles) used in the manufacture of X-ray non-penetrating fillers and the ratio of the hardened body, for Examples 1-11 and Comparative Examples 1-4.

[0027] Figure 4 This is a graph showing the relationship between the mechanochemical treatment time of the raw material powder (crystalline rare earth metal fluoride particles) used in the manufacture of X-ray non-penetrating fillers and the average primary particle size of the crystalline rare earth metal fluoride particles contained in the X-ray non-penetrating fillers, for Examples 1-11 and Comparative Examples 1-4.

[0028] Figure 5 This is a graph showing the relationship between the refractive index of the polymeric monomer or the hardened form of the polymeric monomer and the contrast ratio of the hardened composition or the hardened form, for Examples 16-22 and Comparative Examples 7-13.

[0029] Figure 6This is a graph showing the relationship between the refractive index of the polymeric monomer or the hardened form of the polymeric monomer and the contrast ratio of the hardened composition or the hardened form, for Examples 23-29 and Comparative Examples 14-20.

[0030] Figure 7 This is a graph showing the relationship between the refractive index of the polymeric monomer or the hardened form of the polymeric monomer and the contrast ratio of the hardened composition or the hardened form, for Examples 30-36 and Comparative Examples 21-27.

[0031] Figure 8 This is a graph showing the relationship between the refractive index of the polymeric monomer or the hardened form of the polymeric monomer and the contrast ratio of the hardened composition or the hardened form, for Examples 37-43 and Comparative Examples 28-34. Detailed Implementation

[0032] In order to address the aforementioned problem of existing X-ray non-penetrating fillers formed from rare-earth metal fluorides—namely, the significant decrease in transparency of the hardened body when the amount of filler is increased when mixed into a curing composition containing polymerizable monomers—the inventors of this application conducted in-depth research. As a result, the inventors of this application accidentally discovered that when using powder obtained by prolonged mechanochemical treatment of crystalline ytterbium fluoride, a known X-ray non-penetrating filler, using a wet bead mill, the transparency of the hardened body does not easily decrease even when the amount of filler is increased. Furthermore, based on this insight, the inventors of this application conducted further research and discovered the facts shown in (i) and (ii) below, thereby completing the present invention.

[0033] (i) The crystallinity of the grains is reduced by the above-mentioned mechanochemical treatment.

[0034] (ii) The crystallinity of the grains is determined based on the full width at half maximum (FWHM) of the highest intensity peak originating from crystalline ytterbium fluoride in the diffraction pattern obtained by X-ray diffraction measurements of the aforementioned powder. Moreover, even in a state where the aforementioned powder refinement hardly occurs, an effect that prevents a decrease in transparency can be achieved when the degree of crystallinity reduction exceeds a certain level.

[0035] The reason why the X-ray non-penetrating filler of the present invention does not easily reduce the transparency of the hardened body even when the mixing amount of the X-ray non-penetrating filler relative to the above-mentioned curing composition is not necessarily clear. In addition, the present invention is not bound by any logic. However, based on the facts shown in (1) to (5) below, which were discovered by the inventors of this application, the inventors of this application infer the above reasons as follows.

[0036] (1) A relatively clear correlation was observed between the peak half-width and the transparency (contrast ratio) of the hardened body (see below). Figure 1 ).

[0037] (2) The half-width of the highest peak increases roughly proportionally to the mechanochemical treatment time (see below). Figure 2 ).

[0038] (3) No correlation was found between the average primary particle size of the powder and the transparency (contrast ratio) of the hardened body (see below). Figure 3 and Figure 4 ).

[0039] (4) The effect of preventing the reduction of transparency is not limited to the matrix resin (the hardened form of the polymeric monomer) having a specific refractive index value; rather, the above effect can be seen for matrix resins with a wide refractive index range (see below). Figures 5-8 ).

[0040] (5) In connection with (4) above, (although the refractive indices of the polymeric monomers and their cured forms are different) both the paste-like cured composition before curing and the cured form after curing exhibit the effect of preventing a decrease in transparency (see below). Figures 5-8 ).

[0041] In other words, the reasons for the effectiveness of the X-ray non-penetrating filler of the present invention can be inferred as follows. First, it can be considered that the reduced transparency in a system in which inorganic particles are dispersed in a resin matrix is ​​due to the significant effect of diffuse reflection of light at the interface between the two. On the other hand, through the aforementioned mechanochemical treatment, the area near the surface of the crystalline rare-earth metal fluoride particles gradually becomes amorphous from the surface towards the interior. Therefore, a layer (hereinafter also referred to as a "refractive index tilted layer") is formed near the surface of the crystalline rare-earth metal fluoride particles where the refractive index gradually decreases from the interior towards the surface. Moreover, the formed refractive index tilted layer includes a portion having a refractive index consistent with that of the resin matrix. In this case, the proportion of reflected light decreases (the proportion of transmitted light increases), and the reduction in transparency is suppressed.

[0042] The present invention will now be described in detail. It should be noted that, unless otherwise specified, the use of terms such as "x~y" for numerical values ​​x and y in this specification indicates "x or more and y or less". In this specification, if only the numerical value y is given a unit, that unit also applies to the numerical value x. Furthermore, in this specification, the term "(meth)propylene" refers to both "propylene" and "methpropylene". Similarly, the term "(meth)acrylate" refers to both "acrylate" and "methacrylate", and the term "(meth)acryloyl" refers to both "acryloyl" and "methacryloyl".

[0043] 1. Regarding the X-ray non-penetrating packing material of the present invention

[0044] The X-ray non-penetrating filler of the present invention imparts X-ray non-penetrating properties to a curing composition and its cured form by mixing it into a curing composition containing a polymeric monomer. The polymeric monomer contained in the curing composition that imparts X-ray non-penetrating properties is not particularly limited as long as it is a polymerizable compound; commonly used polymeric monomers can be used depending on the application. For example, when the curing composition is a dental curing composition, free radical polymeric monomers commonly used in that application can be used. From the viewpoint of transparency, the polymeric monomer used in the curing composition into which the X-ray non-penetrating filler of the present invention is preferably such that the refractive index difference "n" satisfies the following condition. X -n M "Conditions within a specific range. Here, n" X The refractive index, n, refers to the refractive index of the crystalline rare-earth metal fluoride particles, which are the main component of the X-ray non-penetrating filler in this invention. M This refers to the refractive index of the hardened body of the polymeric monomer. Specifically, it is preferable to satisfy the following formula (1), more preferably to satisfy the following formula (2), and most preferably to satisfy the following formula (3). It should be noted that, regarding the crystalline rare earth metal fluoride particles after mechanochemical treatment, it is inferred that they have a refractive index tilted layer near the surface as described above. However, since the proportion of the refractive index tilted layer in the overall crystalline rare earth metal fluoride particles after mechanochemical treatment is very small, it can be considered that the presence or absence of the refractive index tilted layer has no substantial impact on the overall refractive index of the particles. In addition, the inventors of this application have confirmed that there is no substantial difference in the refractive index of the crystalline rare earth metal fluoride particles before and after mechanochemical treatment. Therefore, regardless of whether the crystalline rare earth metal fluoride particles, which are the main components of the X-ray non-penetrating filler, are mechanochemically treated, the refractive index difference “n” shown in formulas (1) to (3) remains the same. X -n M When n is the refractive index,X For convenience, the refractive index of crystalline rare earth metal fluoride particles before mechanochemical treatment was used.

[0045] Equation (1) -0.02≤ (n X - n M ≤0.1

[0046] Equation (2) -0.01≤ (n X - n M ≤0.07

[0047] Equation (3) 0≤ (n X - n M ≤0.05

[0048] The X-ray non-penetrating filler of the present invention needs to be composed of any one of the powders selected from the group consisting of a first powder and a second powder. The first powder contains crystalline rare-earth metal fluoride particles as its main component, and the half-width at the peak of its X-ray diffraction pattern is 0.3° or greater. The second powder is obtained by surface treatment of the first powder. Even with powders containing crystalline rare-earth metal fluoride particles as their main component, it is difficult to achieve the effect of preventing opacity when the half-width at the peak of its X-ray diffraction pattern is less than 0.3°. It should be noted that in the following description, the powder constituting the X-ray non-penetrating filler of the present invention is simply referred to as "powder" unless specifically distinguished between the first powder and the second powder.

[0049] In addition, components other than crystalline rare earth metal fluoride particles include: (i) substances derived from surface treatment agents such as silane coupling agents, or (ii) substances derived from coating agents such as silica, surface treatment agents such as silane coupling agents, or other trace additives used as needed in the raw material powder of the manufacturing method of the present invention described later. Furthermore, "containing crystalline rare earth metal fluoride particles as a main component" means that 85% or more of the total mass of the powder is composed of crystalline rare earth metal fluoride particles. In this case, it is preferable that 90% or more of the total mass of the powder is composed of crystalline rare earth metal fluoride particles.

[0050] The following provides a detailed description of the crystalline rare earth metal fluoride particles that constitute the main components of the above-mentioned powder and their maximum peak half-width.

[0051] 1-1. Regarding crystalline rare earth metal fluoride particles

[0052] For rare earth metal fluorides used in crystalline rare earth metal fluoride particles, lanthanum fluoride (LaF3), cerium fluoride (CeF3), ytterbium fluoride (YbF3), or gadolinium fluoride (GdF3) are preferred based on their color and safety. From the viewpoint of X-ray non-penetration, ytterbium fluoride (YbF3) is the most preferred. The crystal structure of crystalline rare earth metal fluoride particles is not particularly limited; generally, a stable crystal structure at room temperature and pressure is used depending on the type of rare earth metal fluoride. Furthermore, the refractive index of these crystalline rare earth metal fluorides relative to the sodium D line at 25°C is typically in the range of 1.50 to 1.65.

[0053] From the viewpoint of maintaining transparency and the gloss of the hardened body when mixed into a dental hardening composition, it is preferable that the first powder contains crystalline rare-earth metal fluoride particles and / or their aggregated particles with an average primary particle size of 1 to 500 nm as the main component, as measured by electron microscopy. In this case, the average primary particle size of the crystalline rare-earth metal fluoride particles is particularly preferably 5 to 300 nm. Here, the average primary particle size measured by electron microscopy refers to the average value of the particle size of 100 primary particles in the resulting image obtained by observing with a scanning electron microscope (SEM) at a magnification of 100,000x.

[0054] Furthermore, from the viewpoint of ease of handling, the average particle size (including the powder as a whole, including agglomerated particles) measured by laser diffraction scattering is preferably 0.1 to 0.6 μm, and more preferably 0.1 to 0.3 μm.

[0055] 1-2. Regarding the half-width of the highest peak

[0056] In the X-ray non-penetrating filler of the present invention, in order to obtain the effect of preventing opacity, the half-width at the highest peak, that is, the full width at half-maximum (WW) of the highest intensity peak originating from the crystalline rare-earth metal fluoride particles in the X-ray diffraction pattern of the powder, must be 0.3° or more. From the viewpoint of high anti-opaqueness effect, the half-width at the highest peak is preferably 0.4° or more, and more preferably 0.5° or more. It should be noted that the upper limit of the half-width at the highest peak is not particularly limited, but it usually does not exceed 40°. However, according to Table 1 described later, from the viewpoint of productivity (mechanical-chemical processing time) of the X-ray non-penetrating filler of this embodiment, the half-width at the highest peak is preferably 0.77° or less. In addition, from the viewpoint of more balanced consideration of the transparency of the hardened body and the productivity of the X-ray non-penetrating filler, the half-width at the highest peak is preferably 0.47° to 0.68°, and more preferably 0.51° to 0.59°.

[0057] The peak half-width in this invention can be determined by X-ray diffraction measurement of the powder that serves as the X-ray non-penetrating filler of this invention. Specifically, X-ray diffraction measurements of the sample (powder) are performed using an X-ray diffraction apparatus in the range of 2θ from 20 to 120° to obtain an X-ray diffraction pattern (Figure) with 2θ (°) on the horizontal axis and diffraction intensity on the vertical axis. In this way, peaks originating from crystalline rare-earth metal fluoride particles are obtained, and the peak with the highest intensity is determined. For example, in the case where the material of the crystalline rare-earth metal fluoride particles is YbF3, the peak corresponding to the crystal plane (111) that appears near 2θ = 28.0° is the peak with the highest intensity. Then, the peak width at which the intensity reaches 50% of the maximum intensity (50% intensity) of the peak with the highest intensity is obtained as the peak half-width. Here, peak width is the absolute value (unit: deg[°]) of the difference between 2θ at the two intersection points formed by the straight line parallel to the horizontal axis of the X-ray diffraction pattern (Figure) and the peak line at the 50% intensity position. It should be noted that, during measurement, it is preferable to use powder after removing coarse particles, such as a sieve with a mesh size of 100 μm, as the measurement sample.

[0058] Generally, it is known that there is a well-known correlation between the full width at half maximum (WWHM) of diffraction peaks and crystallite size in X-ray diffraction, as stated by the Scherrer equation: crystallite size is inversely proportional to the WWHM. Furthermore, lattice distortion also affects the WWHM, with a tendency for larger lattice distortion to increase it. It can be considered that larger lattice distortion leads to smaller crystallite diameters and the orientation of finer crystals in various directions, thus increasing amorphousness. Therefore, the WWHM of the highest peak can be considered an indicator of the crystallinity of rare-earth metal fluorides.

[0059] As described below, X-ray diffraction measurements were performed on commonly used rare-earth metal fluoride X-ray non-penetrating fillers or (crystalline) rare-earth metal fluorides that can be obtained as reagents. The peak half-width was less than 0.3° (0.17–0.27°). Therefore, it can be said that the average crystallite diameter of the crystalline rare-earth metal fluoride particles constituting the X-ray non-penetrating filler of this invention is significantly reduced, and the overall crystallinity is slightly decreased.

[0060] Furthermore, based on the research of the inventors of this application, (i) the facts shown in (1) to (5) above have been confirmed, and (ii) in the mechanochemical processing of the manufacturing method of the present invention, in a system where the primary particle size is inherently small and remains almost unchanged even with extended processing time, the half-maximum width of the peak increases with the length of processing time. Therefore, it is believed that the crystallinity within the particles is likely to be non-uniform. However, it is difficult, and practically impossible, to analyze the state of the microcrystals or the state of lattice distortion of the individual crystalline rare earth metal fluoride particles constituting the powder that constitutes the X-ray non-penetrating filler of the present invention. Therefore, in the present invention, the half-maximum width of the peak is used as an index of averaged crystallinity to determine the X-ray non-penetrating filler of the present invention. Furthermore, based on these circumstances, the X-ray non-penetrating filler of the present invention can also be said to be the X-ray non-penetrating filler obtained by the manufacturing method of the present invention.

[0061] 2. Regarding the manufacturing method of the present invention

[0062] The manufacturing method of the present invention is a method for manufacturing the X-ray non-penetrating filler of the present invention, characterized in that it includes: a process of mechanically and chemically treating a raw material powder containing crystalline rare earth metal fluoride particles as the main component and having a peak half-width of less than 0.3°, so that the peak half-width becomes 0.3° or more.

[0063] As described above, the peak half-width at half-maximum (WWHM) of rare-earth metal fluoride X-ray non-penetrating fillers or (crystalline) rare-earth metal fluoride powders that are commonly used in the prior art are typically less than 0.3°. Therefore, such powders can be used as raw material powders without particular limitations. When there are concerns about the low crystallinity of the raw material powder, it is preferable to perform X-ray diffraction measurements on the raw material powder to confirm that the peak half-width is less than 0.3° before use. Furthermore, commercially available crystalline rare-earth metal fluoride powders for X-ray non-penetrating fillers also include powders surface-coated with nano silica or surface-treated with silane coupling agents, etc. In the manufacturing method of the present invention, these powders can also be used directly as raw material powders. In the mechanochemical processing described later, depending on the conditions, if the processing time of the raw material powder is extended, particle pulverization occurs, and secondary particles (agglomerated particles) or primary particles are broken down, thereby reducing the particle size of the raw material powder. However, during the mechanochemical treatment lasting approximately several hours, the particle size of the raw material powder did not change significantly. Therefore, the average primary particle size of the raw material powder (similar to the powder constituting the X-ray non-penetrating filler of the present invention), as measured by electron microscopy, is preferably 1–500 nm, particularly preferably 5–300 nm. Furthermore, the average particle size measured by laser diffraction scattering is preferably 0.1–0.6 μm, particularly preferably 0.1–0.3 μm.

[0064] In the manufacturing method of the present invention, the above-mentioned raw material powder is subjected to mechanochemical treatment, thereby making the peak half-width at half-maximum of 0.3° or more. Here, mechanochemical treatment refers to the treatment that imparts mechanical energy to the raw material powder, and refers to at least one of mechanical grinding, pulverizing, and dispersing. From the perspective of being able to reliably and effectively control the crystallinity of crystalline rare earth metal fluoride powders (or particles) to the desired crystallinity, wet processing is preferred as the mechanochemical treatment method, and processing using a wet bead mill is particularly preferred. When performing mechanochemical treatment by wet processing, solvents such as water or ethanol, polymerizable monomers, etc., can be used as the medium. However, from the viewpoint of the dispersibility of X-ray non-penetrating fillers or their addition to dental compositions, a medium that is liquid at room temperature (15°C to 25°C) is preferred.

[0065] The manufacturing method of the present invention will be described in detail below, taking the processing using a wet bead mill as an example.

[0066] In the mechanochemical processing using a wet bead mill, a slurry is brought into contact with a medium (beads) that is subjected to motion through stirring or vibration. The slurry is a mixture of the raw material powder to be processed and the medium. This process pulverizes or breaks down the raw material powder. Examples of materials for the beads used as the medium include glass, alumina, zircon, zirconia, steel, or resin. Alumina or zirconia are preferred due to their excellent wear resistance and low contamination. The size of the beads used is selected based on the particle size of the target X-ray non-penetrating filler, and there are no particular limitations, but beads with a diameter of 0.01 mm to 0.5 mm are generally preferred. This allows for the acquisition of X-ray non-penetrating fillers with a particle size suitable for addition to dental hardening compositions.

[0067] Depending on their operating method, wet bead mills can be categorized into batch type, circulating type (where the slurry and beads are directly fed into the device for processing), pass type (where the slurry circulates between the container and the device), and through type (where the slurry passes through the device a predetermined number of times). The choice of operating method depends on the amount of raw material powder used in the mechanochemical process. Circulating bead mills are preferred due to their high productivity and ability to process relatively large quantities of raw material powder.

[0068] Based on the aforementioned circulating or through-process operating methods, it is necessary to separate the slurry and beads during mechanochemical processing. Examples of bead separation methods include slit separation, screen separation, and centrifugal separation. These methods can be selected based on the particle size of the beads used, and any method can be used without particular restriction. The concentration of the slurry used for mechanochemical processing is preferably 50 parts by mass or less of the raw material powder relative to 100 parts by mass of the medium. If the raw material powder in the slurry exceeds 50 parts by mass, the viscosity of the slurry becomes high, sometimes making mechanochemical processing difficult.

[0069] By adding a dispersant to the slurry, the increase in slurry viscosity can be suppressed. Therefore, by adding a dispersant to the slurry, a higher concentration of slurry can be mechanically treated. As for the dispersant used, any known surfactant commonly used in the dispersion treatment of fillers can be used without particular restriction. Examples include: nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and their polymeric surfactants. Specifically, examples include: glycerol fatty acid esters and their alkylene glycol adducts, aliphatic monocarboxylate salts, alkylamine salts, and alkyl betaines. When preparing a dental curable composition using mechanically treated raw material powder (crystalline rare earth metal fluoride particles with a peak half-width of 0.3° or higher), from the viewpoint of the dispersibility of the mechanically treated raw material powder in the dental curable composition, a cationic surfactant is preferred as the dispersant.

[0070] The mechanochemical processing conditions vary depending on the operating mode of the wet bead milling apparatus used, the bead diameter, the peak half-width of the raw material powder, and the slurry concentration. These conditions can be assessed by conducting preliminary experiments using the actual apparatus used for mechanochemical processing, and confirming the peak half-width of the raw material powder after mechanochemical processing relative to the processing time. Furthermore, when manufacturing X-ray non-penetrating fillers, the processed slurry should be sampled as needed to appropriately confirm the peak half-width. In this way, X-ray non-penetrating fillers containing crystalline rare-earth metal fluoride particles with the desired peak half-width as the main component can be reliably manufactured.

[0071] For raw material powders (mechanically treated crystalline rare earth metal fluoride particles) with a peak half-width of 0.3° or higher obtained through mechanochemical treatment, concentration, drying, and filtration are typically performed to obtain the X-ray non-penetrating filler of this invention. It should be noted that when using polymerizable monomers as a medium in wet processing, these operations can be omitted and the filler can be used directly. Furthermore, to improve affinity with various polymerizable monomers and their polymers, the obtained X-ray non-penetrating filler can be surface-treated. Commonly used compounds such as silane coupling agents or titanate coupling agents can be used as surface treatment agents.

[0072] 3. Regarding the dental hardening composition of the present invention

[0073] As described above, the X-ray non-penetrating filler of the present invention is particularly useful as a filler mixed in dental curing compositions (i.e., dental X-ray non-penetrating filler). In addition to the X-ray non-penetrating filler of the present invention, the dental curing composition also contains polymerizable monomers and polymerization initiators.

[0074] As a polymerizable monomer, the known polymerizable monomers used in this application can be used without restriction. Specific examples include: methyl meth acrylate, glycidyl meth acrylate, 2-cyanomethyl meth acrylate, polyethylene glycol monometh acrylate, allyl meth acrylate, 2-hydroxyethyl monometh acrylate, ethylene glycol dimeth acrylate, diethylene glycol dimeth acrylate, triethylene glycol dimeth acrylate, nonaethylene glycol dimeth acrylate, propylene glycol dimeth acrylate, and dipropylene glycol dimeth acrylate. di(meth)acrylate), 2,2-bis[4-(meth)acryloyloxyethoxyphenyl]propane, 2,2-bis[4-(meth)acryloyloxyethoxyphenyl]propane, 2,2-bis{4-[3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl}propane, 1,4-butanediol di(meth)acrylate, 1,3-hexanediol di(meth)acrylate3-Hexanediol di(meth)acrylate, urethane di(meth)acrylate, trimethylolpropane di(meth)acrylate, and other (meth)acrylate monomers.

[0075] Polymerizable monomers can be used alone or in combination of two or more. However, as mentioned above, from the viewpoint of the transparency of the resulting hardened body, the polymerizable monomers preferably satisfy the following condition: the difference in refractive index "n X -n M "The conditions are within a specific range. Specifically, it is preferable to satisfy equation (1), more preferably to satisfy equation (2), and most preferably to satisfy equation (3). The refractive index of the hardened body of the polymeric monomer can be adjusted by combining a variety of polymeric monomers. The aforementioned known polymeric monomers can be mixed in any ratio."

[0076] The amount of the X-ray non-penetrating filler of the present invention mixed in the dental curing composition of the present invention is not particularly limited as long as the dental curing composition becomes a paste, but it is generally preferred to be in the range of 1 to 80 parts by weight relative to 100 parts by weight of the dental curing composition, and more preferably in the range of 3 to 70 parts by weight. Furthermore, from the viewpoint of imparting X-ray non-penetrating properties and various physical properties (e.g., mechanical strength or hardness) to the cured body, the amount of the X-ray non-penetrating filler mixed is further preferably 10 to 40 parts by weight relative to 100 parts by weight of the dental curing composition. Additionally, from the viewpoint of imparting X-ray non-penetrating properties to the cured body, it is preferable to mix 1 to 400 parts by weight of the X-ray non-penetrating filler relative to 100 parts by weight of the polymerizable monomer.

[0077] As polymerization initiators, chemical polymerization initiators, photopolymerization initiators, or thermal polymerization initiators that are capable of polymerizing polymerizable monomers can be used without particular restrictions.

[0078] Regarding the mixing amount of polymerization initiator, there is no particular limitation as long as it is sufficient to initiate polymerization; generally, it is in the range of 0.001 to 10 parts by mass relative to 100 parts by mass of polymerizable monomer. From the viewpoint of polymerization rate and various physical properties of the resulting hardened body (e.g., weather resistance or hardness), it is preferable to mix 0.05 to 5 parts by mass based on the above-mentioned standard.

[0079] The type of polymerization initiator mentioned above can be selected according to the intended use of the dental curing composition. When the dental curing composition is a dental filling material that hardens in the oral cavity, a photopolymerization initiator is preferred. When the dental curing composition is a mill blank used to cut and utilize a pre-hardened block in a dental clinic or laboratory, a thermal polymerization initiator is preferred.

[0080] Examples of photopolymerization initiators include benzoin alkyl ethers, benzyl ketals, benzophenones, α-diketones, thioxanthone compounds, and bisacylphosphine oxides. It should be noted that reducing agents are often added to photopolymerization initiators. Examples of reducing agents include aromatic amines, aliphatic amines, aldehydes, and sulfur-containing compounds. Furthermore, trihalomethyltriazine compounds and aryl iodonium salts may be added as needed.

[0081] In addition to the components described above, the dental curing composition of the present invention may also contain other components known as components of dental curing compositions, especially dental filling and restorative materials. Examples of such components include fillers other than the X-ray non-penetrating filler of the present invention, polymerization inhibitors, ultraviolet absorbers, dyes, antistatic agents, pigments, fragrances, organic solvents, and thickeners, as well as other known additives.

[0082] As other fillers, any of the organic or inorganic fillers mixed in the dental curing composition can be incorporated. Examples of organic fillers include particles composed of organic polymers such as polymethyl methacrylate, polyethyl methacrylate, methyl methacrylate-ethyl methacrylate copolymer, cross-linked polymethyl methacrylate, cross-linked polyethyl methacrylate, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, acrylonitrile-styrene copolymer, and acrylonitrile-butadiene-styrene copolymer.

[0083] Specifically, examples of inorganic fillers include inorganic particles such as quartz, silicon dioxide, alumina, silicon dioxide-titanium dioxide, silicon dioxide-zirconium oxide, lanthanum glass, barium glass, strontium glass, and metal oxides.

[0084] The particle size and shape of these other fillers are not particularly limited. Spherical or amorphous particles with an average particle size of 0.001 μm to 100 μm, which are commonly used as dental materials, can be used appropriately depending on the purpose. In addition, the refractive index of these other fillers is not particularly limited. The refractive index in the range of 1.4 to 2.6, which is common in fillers of dental hardening compositions, can be used without restriction.

[0085] Regarding the mixing amount of other fillers in the dental hardening composition of the present invention, there is no particular limitation as long as the dental hardening composition becomes a paste. However, when the dental hardening composition is used as a dental filling and restorative material, the total amount of X-ray non-penetrating filler and other fillers relative to 100 parts by weight is preferably 25 to 400 parts by weight, more preferably 40 to 250 parts by weight.

[0086] The hardening composition incorporating the X-ray non-penetrating filler of the present invention is not limited to the dental applications described above, but can be used in adhesives, coatings, optical materials, etc., and is particularly suitable as a dental filling and restorative material.

[0087] The method for manufacturing the dental curing composition of the present invention is not particularly limited, and a known method for manufacturing curing compositions may be appropriately employed. Specifically, (i) in the case of photopolymerizable dental curing compositions, a predetermined amount of the X-ray non-penetrating filler, polymerizable monomer, polymerization initiator, and other mixed components constituting the dental curing composition of the present invention are weighed and mixed in the dark, or (ii) in the case of thermally polymerizable dental curing compositions, at room temperature or low temperature, and these are mixed to prepare a paste-like dental curing composition. The dental curing composition of the present invention thus manufactured is stored under light-proof conditions, at room temperature, or at low temperature before use. In the case of chemically polymerizable dental curing compositions, the two or more components that generate active species through mixing are physically separated, and the manufacturing and storage are carried out in the same manner as the above-described photopolymerizable or thermally polymerizable dental curing compositions.

[0088] As a method for curing the dental curing composition of the present invention, any known polymerization method can be appropriately employed according to the polymerization initiation mechanism of the polymerization initiator used. Specifically, as a curing means, light irradiation based on light sources such as carbon arc lamps, xenon lamps, metal halide lamps, tungsten lamps, fluorescent lamps, sunlight, helium-cadmium lasers, argon ion lasers, etc., or heating using a heating polymerizer, or a combination of these methods, can be used without any limitations. When the dental curing composition is polymerized by light irradiation, since the irradiation time varies depending on the wavelength or intensity of the light source and the shape or material of the hardened body, it can be determined in advance through preliminary experiments. However, it is generally preferable to adjust the mixing ratio of the various components contained in the dental curing composition so that the irradiation time is in the range of about 5 to 60 seconds.

[0089]

Example

[0090] The present invention will be specifically described below through examples, but the present invention is not limited to these examples in any way.

[0091] First, the substances and their abbreviations used as raw materials for the prepared curing compositions in the examples and comparative examples will be explained, as well as the evaluation methods for the above-mentioned raw materials and the prepared curing compositions.

[0092] 1. Substances and their abbreviations

[0093] 1-1. Polymerizable monomers

[0094] UDMA: 1,6-Bis(methacrylethyloxycarbonylamino)-2,2,4-trimethylhexane

[0095] 3G: Triethylene glycol dimethacrylate

[0096] BisGMA: 2,2-Bis[4-[2-hydroxy-3-(methacryloyloxy)propyloxy]phenyl]propane

[0097] D-2.6E: 2,2-Bis[4-(methacryloxyethoxy)phenyl]propane

[0098] 1-2. Polymerization initiator

[0099] CQ: Camphorquinone (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0100] DMBE: Dimethyl benzoic acid ethyl (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0101] 1-3. Packing

[0102] (1) Crystalline rare earth metal fluoride particles (raw material powder)

[0103] As the raw material (raw material powder) for X-ray non-penetrating filler, crystalline rare earth metal fluoride particles as shown below were used.

[0104] RF1: YbF3-40 (ytterbium fluoride with an average primary particle size of 40 nm, an average secondary particle size of 0.6 μm, and a refractive index of 1.55, manufactured by Sukgyung Corporation)

[0105] RF2: YbF3-100 (ytterbium fluoride with an average primary particle size of 100 nm, an average secondary particle size of 0.6 μm, and a refractive index of 1.55, manufactured by Sukgyung Corporation)

[0106] RF3: YbF3-200 (ytterbium fluoride with an average primary particle size of 200 nm, an average secondary particle size of 0.6 μm, and a refractive index of 1.55, manufactured by Treibacher).

[0107] RF4: YbF3-300 (ytterbium fluoride with an average primary particle size of 300 nm, an average secondary particle size of 0.6 μm, and a refractive index of 1.55, manufactured by Treibacher).

[0108] RF5: LaF3 (lanthanum fluoride with an average primary particle size of 400 nm, an average secondary particle size of 0.6 μm, and a refractive index of 1.58, manufactured by Fujifilm and Koden Pharmaceutical Co., Ltd.)

[0109] RF6: CeF3 (Cerium fluoride with an average primary particle size of 350 nm, an average secondary particle size of 0.7 μm, and a refractive index of 1.63, manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.)

[0110] RF7: GdF3 (Gadolinium fluoride with an average primary particle size of 390 nm, an average secondary particle size of 0.6 μm, and a refractive index of 1.62, manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.)

[0111] It should be noted that the average primary particle size, average secondary particle size, and refractive index are values ​​determined based on the evaluation method described later.

[0112] 2. Various evaluation methods

[0113] 2-1. Measurement of average primary particle size

[0114] The average primary particle size of the crystalline rare-earth metal fluoride particles constituting the X-ray non-penetrating filler was determined using a scanning electron microscope according to the following steps. First, a measurement sample was prepared by fixing the X-ray non-penetrating filler onto a sample stage using carbon paste and then performing a conductive treatment (platinum vapor deposition). Next, the measurement sample was observed at 100,000x magnification using an electron microscope (JSM-7800F PRIME, manufactured by Nippon Egis Corporation), and the average particle size of 100 primary particles in the resulting image was determined as the average primary particle size. The average primary particle size of the raw material powder was also determined using the same procedure.

[0115] 2-2. Measurement of average secondary particle size

[0116] The average secondary particle size of the crystalline rare-earth metal fluoride particles constituting the X-ray non-penetrating filler was determined by particle size distribution measurement using the following steps: First, a suspension was prepared by suspending 0.1 g of powder (X-ray non-penetrating filler) in 10 mL of ion-exchanged water. Next, while the suspension was subjected to ultrasonic irradiation, the particle size distribution was measured using a particle size analyzer (LS13-320, manufactured by Beckman Coulter) to obtain the particle size volume distribution. Then, the particle size (D50v value) accumulated from the smallest diameter side of the particle size volume distribution was taken as the average secondary particle size of the crystalline rare-earth metal fluoride particles constituting the X-ray non-penetrating filler. Additionally, the average secondary particle size of the raw material powder was determined using the same procedure.

[0117] 2-3. Measurement of Refractive Index

[0118] 2-3-1. Refractive index n0 of polymerizable monomers

[0119] The refractive index n0 of the polymeric monomer used in the preparation of the curable composition was measured at 25°C relative to the sodium D line using an Abbe refractometer (DR-A1-Plus, manufactured by ATAGO Corporation).

[0120] 2-3-2. The refractive index n of a polymer (a hardened body of polymeric monomers) M

[0121] The polymeric monomers used in the preparation of the curing composition (containing trace amounts of polymerization initiator for curing treatment (0.2 wt% camphorquinone and 0.35 wt% N,N-dimethyl-terephthalate)) are filled into the through-holes (7 mm in diameter and 0.5 mm in length) provided in the mold, and then sealed while pressing the openings on both sides of the through-holes with a polypropylene film. Then, the polymeric monomers filled in the through-holes are subjected to light at a intensity of 500 mW / cm². 2 The material was hardened by irradiation with a halogen-type dental light irradiator (Demetron LC, manufactured by Sybron) for 30 seconds. Then, the refractive index n of the hardened polymeric monomer, removed from the mold, was measured following the same procedure as in 2-3-1. M .

[0122] 2-3-3. Refractive index n of crystalline rare earth metal fluoride particles X

[0123] In a constant temperature chamber at 25°C, 1 g of crystalline rare-earth metal fluoride particles were suspended in 50 mL of anhydrous toluene in a 100 mL sample vial. While stirring the suspension with a stir bar, 1-bromotoluene was added dropwise. The refractive index of the suspension at its most transparent state was measured following the same procedure as in section 2-3-1. The obtained value was taken as the refractive index n of the crystalline rare-earth metal fluoride particles. X Furthermore, as mentioned above, the refractive index n of the crystalline rare-earth metal fluoride particles after mechanochemical treatment... X The refractive index of the crystalline rare earth metal fluoride particles before mechanical and chemical treatment is used instead.

[0124] 2-4. Evaluation of the transparency (contrast ratio) of the curing composition and the cured body

[0125] The curing compositions prepared in each example and comparative example were filled into a polyacetal mold with an inner diameter of 0.7 cm and a depth of 0.1 cm. This mold was used as a sample when evaluating the transparency of the curing composition. Alternatively, when evaluating the transparency of the cured body, the curing composition was filled into the mold in the same manner as described above, and the body was cured by irradiation with a dental light irradiator (TOKUSO POWER LIGHT, manufactured by TOKUYAMA Co., Ltd.) at a distance of 0.5 cm for 20 seconds. The resulting material was used as a sample. Regarding the evaluation of transparency, the Y-value of each sample was measured against a black and white background using a colorimeter (SE7700, manufactured by Nippon Denshoku Co., Ltd.), and the transparency (contrast ratio: Yb / Yw) was calculated using the following formula.

[0126] Yb / Yw = Y value against a black background (Yb) / Y value against a white background (Yw)

[0127] 3. Manufacturing of X-ray Non-penetrating Fillers

[0128] As X-ray non-penetrating fillers, crystalline rare earth metal fluoride particles (YbF3-40, YbF3-100, YbF3-200, YbF3-300, LaF3, CeF3, and GdF3) listed as raw material powders in 1-3(1) and powders after mechanical chemical treatment of these raw material powders were used. Table 1 shows: abbreviations for X-ray non-penetrating fillers in the examples and comparative examples, abbreviations for crystalline rare earth metal fluoride particles (raw material powders themselves or powders after mechanical chemical treatment of the raw material powders) used in the manufacture of X-ray non-penetrating fillers, mechanical chemical treatment time of the raw material powders, average primary particle size (for mechanically treated raw material powders, the value after mechanical chemical treatment), 2θ of the highest peak and half-width of the highest peak, and refractive index n. X .

[0129] In addition, the mechanochemical treatment was carried out using a wet bead mill SC50 (manufactured by Mitsui Mining Co., Ltd.). Then, using 100g of φ0.3mm zirconia beads as the medium, a slurry containing 5.0 parts by mass of crystalline rare earth metal fluoride particles mixed with 100 parts by mass of ion-exchanged water was dispersed at 3000 rpm. The types of crystalline rare earth metal fluoride particles used in the dispersion treatment and the treatment time are shown in Table 1. Furthermore, in the measurement of the peak half-width, a measurement sample was obtained by removing coarse particles from the raw material powder or the powder after mechanochemical treatment using a 100μm mesh sieve. This measurement sample was then placed on the sample stage of an X-ray diffraction apparatus (Smartlab, manufactured by Rigaku Co., Ltd.), and X-ray diffraction measurements were performed, resulting in an X-ray diffraction pattern (Figure) with 2θ (°) on the horizontal axis and diffraction intensity on the vertical axis. Here, the 2θ and peak half-width (deg: °) shown in Table 1 are values ​​related to the peak of the crystal plane (111) on the X-ray diffraction pattern (Figure).

[0130] [Table 1]

[0131]

[0132] 4. Examples and Comparative Examples

[0133] Example 1

[0134] A liquid composition was prepared by adding 0.2 parts by mass of CQ and 0.35 parts by mass of DMBE as polymerization initiators to 100 parts by mass of polymerizable monomers consisting of 80 parts by mass of UDMA and 20 parts by mass of 3G, and stirring for 6 hours. F1, an X-ray non-penetrating filler, was added to this liquid composition at 150 parts by mass (60 wt%) relative to 100 parts by mass of polymerizable monomers. The mixture was then mixed using an agate mortar, and the resulting mixture was degassed under vacuum to remove air bubbles, thereby obtaining a paste-like curable composition. The transparency (contrast ratio) of the cured body of the obtained curable composition was evaluated. The results are shown in Table 2.

[0135] [Table 2]

[0136]

[0137] Examples 2-15, Comparative Examples 1-6

[0138] Except for changing the polymerizable monomers and X-ray non-penetrating fillers mixed in Example 1 to the materials shown in Table 2, curable compositions of Examples 2-15 and Comparative Examples 1-6 were prepared in the same manner as in Example 1. The transparency (comparative ratio) of the cured bodies of the obtained curable compositions was then evaluated. The results are shown in Table 2.

[0139] As shown in Table 2, in Comparative Examples 1-6, where the peak half-width of the X-ray non-penetrating filler used was less than 0.3°, the resulting hardened bodies were relatively opaque (high contrast ratio, 0.63-0.70). On the other hand, in Examples 1-15, which used X-ray non-penetrating fillers containing crystalline rare-earth metal fluoride particles with a peak half-width of 0.3° or more after undergoing mechanochemical treatment, hardened bodies with good transparency (contrast ratio: 0.06-0.43) were obtained. Furthermore, for each hardened body, as the value of the peak half-width increased, the transparency of the hardened body increased (contrast ratio decreased).

[0140] Examples 16-22, Comparative Examples 7-13

[0141] Except for changing the composition of the polymerizable monomers mixed in Example 2 as described in Table 3, curable compositions of Examples 16-22 were prepared in the same manner as in Example 2. Similarly, except for changing the composition of the polymerizable monomers mixed in Comparative Example 1 as described in Table 3, curable compositions of Comparative Examples 7-13 were prepared in the same manner as in Comparative Example 1. The transparency of the obtained paste-like curable compositions and their cured forms was then evaluated. The results are shown in Table 3.

[0142] [Table 3]

[0143]

[0144] As shown in Table 3, in the examples (or comparative examples) using the same X-ray non-penetrating filler, the refractive indices of the polymeric monomer and the hardened polymeric monomer are different depending on the composition of the polymeric monomer. However, when comparing examples and comparative examples with the same polymeric monomer composition, it was confirmed that in Examples 16-22, which used X-ray non-penetrating filler F 1-3h with a peak half-width of 0.3° or more, the contrast ratio of the hardened composition to the hardened body was lower and the transparency was improved compared to Comparative Examples 7-13, which used X-ray non-penetrating filler RF 1 with a peak half-width of less than 0.3°.

[0145] Examples 23-29, Comparative Examples 14-20

[0146] Except for changing the X-ray non-penetrating fillers used to F5-3h (LaF3) and RF5 (LaF3), the curable compositions of Examples 23-29 and Comparative Examples 14-20 were prepared in the same manner as in Examples 16-22 and Comparative Examples 7-13. The transparency of the resulting paste-like curable compositions and their cured forms was then evaluated. The results are shown in Table 4.

[0147] [Table 4]

[0148]

[0149] As shown in Table 4, when comparing examples and comparative examples with the same polymerizable monomer composition in the LaF3 system, it was also confirmed that the examples had higher transparency (lower comparison ratio) than the curing compositions and their cured forms.

[0150] Examples 30-36, Comparative Examples 21-27

[0151] Except for changing the X-ray non-penetrating fillers used to F6-3h (CeF3) and RF6 (CeF3), the curable compositions of Examples 30-36 and Comparative Examples 21-27 were prepared in the same manner as in Examples 16-22 and Comparative Examples 7-13. The transparency of the resulting paste-like curable compositions and their cured forms was then evaluated. The results are shown in Table 5.

[0152] [Table 5]

[0153]

[0154] As shown in Table 5, when comparing the examples and comparative examples with the same polymerizable monomer composition in the CeF3 system, it was also confirmed that the examples had higher transparency (lower comparison ratio) than the curing compositions and their cured forms.

[0155] Examples 37-43, Comparative Examples 28-34

[0156] Except for changing the X-ray non-penetrating fillers used to F7-3h (GdF3) and RF7 (GdF3), the curable compositions of Examples 37-43 and Comparative Examples 28-34 were prepared in the same manner as in Examples 16-22 and Comparative Examples 7-13. The transparency of the resulting paste-like curable compositions and their cured forms was then evaluated. The results are shown in Table 6.

[0157] [Table 6]

[0158]

[0159] As shown in Table 6, when comparing examples with the same polymerizable monomer composition in the GdF3 system with comparative examples, it was also confirmed that the examples had higher transparency (lower comparative ratio) than the curing compositions and their cured forms.

[0160] 5. Evaluation of X-ray contrast imaging

[0161] The curing compositions of each embodiment were tested according to ISO 13116-2014. As a result, the cured articles obtained from the curing compositions of any embodiment all exhibited X-ray non-penetration exceeding that of aluminum with the same thickness as the cured article. Therefore, it was confirmed that the cured articles obtained from the curing compositions of any embodiment all possess sufficient non-penetration relative to X-rays. It should be noted that the practical X-ray non-penetration required for dental materials must exhibit X-ray non-penetration to approximately the same degree as or greater than that of aluminum with the same thickness as the cured article. Here, the mixing amount of the X-ray non-penetrating filler of the present invention, exhibiting X-ray non-penetration to approximately the same degree as that of aluminum with the same thickness as the cured article, is approximately 3 to 10 parts by weight relative to 100 parts by weight of the curing composition.

[0162] Furthermore, the curing compositions of the various embodiments described above are suitable for use as dental curing compositions. Additionally, for reference, various graphs based on the experimental data shown in Tables 1 to 6 are presented in... Figures 1 to 8 middle.

Claims

1. An X-ray non-penetrating filler that imparts X-ray non-penetrating properties to a curing composition and its cured form by incorporation into a curing composition containing a polymerizable monomer. The X-ray non-penetrating filler is characterized in that... The X-ray non-penetrating filler is composed of any powder selected from the group consisting of the first powder and the second powder, wherein... The first powder is obtained by mechanical and chemical treatment of raw material powder and has a full width at half maximum (WWHM) of 0.3° or more and 0.77° or less. The raw material powder contains 85% or more of crystalline rare earth metal fluoride particles as the main component, and the full width at half maximum (WWHM) of the highest intensity peak originating from the crystalline rare earth metal fluoride particles in the X-ray diffraction pattern is less than 0.3°. The second powder is obtained by surface treatment of the first powder.

2. The X-ray non-penetrating packing material according to claim 1, characterized in that, The first powder is a powder containing at least one particle as the main component from a group consisting of crystalline rare earth metal fluoride particles with an average primary particle size of 1 nm to 500 nm as measured by electron microscopy and aggregated particles of the crystalline rare earth metal fluoride particles with an average primary particle size of 1 nm to 500 nm.

3. The X-ray non-penetrating packing material according to claim 1 or 2, characterized in that, The crystalline rare earth metal fluoride particles are crystalline ytterbium fluoride particles.

4. The X-ray non-penetrating packing material according to claim 1 or 2, characterized in that, The crystalline rare earth metal fluoride particles include at least one particle selected from the group consisting of crystalline lanthanum fluoride particles, crystalline cerium fluoride particles, and crystalline gadolinium fluoride particles.

5. The X-ray non-penetrating packing material according to claim 1 or 2, characterized in that, The half-width is 0.47° to 0.68°.

6. The X-ray non-penetrating packing material according to claim 1 or 2, characterized in that, The half-width is 0.51° to 0.59°.

7. A dental X-ray non-penetrating filler, characterized in that, It is composed of the X-ray non-penetrating filler as described in any one of claims 1 to 6.

8. A method for manufacturing an X-ray non-penetrating filler, comprising the method for manufacturing the X-ray non-penetrating filler according to any one of claims 1 to 6. The method for manufacturing the X-ray non-penetrating filler is characterized in that, include: The process of performing mechanochemical treatment on raw material powder to make the full width at half maximum (WWHM) of the raw material powder greater than 0.3°, wherein the raw material powder contains crystalline rare earth metal fluoride particles as the main component, and the full width at half maximum (WWHM) of the highest peak originating from the crystalline rare earth metal fluoride particles in the X-ray diffraction pattern is less than 0.3°.

9. The method for manufacturing the X-ray non-penetrating filler according to claim 8, characterized in that, The mechanochemical treatment is a wet bead milling process.

10. A dental hardening composition, characterized in that, It comprises a polymerizable monomer and an X-ray non-penetrating filler according to any one of claims 1 to 6.

11. The dental hardening composition according to claim 10, characterized in that, The crystalline rare-earth metal fluoride particles are crystalline ytterbium fluoride particles. The hardened form of the polymeric monomer has a refractive index of 1.45 to 1.60 relative to the sodium D line at 25°C.

12. The dental hardening composition according to claim 10 or 11, characterized in that, It satisfies the following equation (1). Equation (1) -0.02≤(n) X -n M ≤0.1 In the above equation (1), n X The term n refers to the refractive index of the crystalline rare-earth metal fluoride particles. M This refers to the refractive index of the hardened form of the polymeric monomer.

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