Dental curable composition, blank for dental-cutting work, production method for silica-based composite oxide powder body, and dental filler

Abstract

[Problem] To provide a blank that is for dental-cutting work and that has a portion to be subjected to cutting work and comprising a hybrid resin that contains spherical particles of a silica-based composite oxide, and that has a color appearance less likely to change depending on the thickness. [Solution] The present invention uses, as a portion to be subjected to cutting work, a cured body of a dental curable composition that contains, with respect to 100 parts by mass of a radical polymerizable monomer, 100-800 parts by mass of a silica-based composite oxide powder body that has an average primary particle size of 350-600 nm, that is formed of spherical particles, of a silica-based composite oxide, having a silica content of 80-92 mol% and not including silica cores, and that is obtained through control of, when depositing the silica-based composite oxide powder body by adding a basic solution to a raw material solution in which a condensable compound such as tetraethyl silicate or tetra(n-butoxy)zirconate is dissolved, solvent compositions of the respective solutions.

Description

Dental hardenable composition, dental cutting blank, method for producing silica-based complex oxide powder and dental filling material

[0001] The present invention relates to a dental curable composition, a dental cutting blank, a silica-based composite oxide powder and granules, and a dental filler.

[0002] Composite resins (hereinafter sometimes abbreviated as "CR") used in dental filling treatments are dental hardenable compositions that produce hardened products called hybrid resins (hereinafter sometimes abbreviated as "HR"). HRs are also widely used as materials for inlays, onlays, crowns, bridges, implant superstructures, and other dental prosthetic restorations.

[0003] Dental curable compositions used as raw materials for HRs are composed of compositions containing an inorganic filler such as silica, a polymerizable monomer such as a methacrylate resin, and a polymerization initiator from the viewpoints of strength, etc., and powders (inorganic powders) composed of spherical inorganic oxide particles are often used as the inorganic filler from the viewpoints of ease of cutting and polishing and high aesthetic appeal (see Patent Document 1). As fillers that are powders of spherical inorganic oxide particles, powders composed of spherical particles of silica-based composite oxides, which are inorganic oxides whose main components are at least one metal component selected from Groups I to IV of the periodic table and a silicon component, particularly silica-titanium group composite oxides such as silica-zirconia oxide, are commonly used (see Patent Documents 1 to 3).

[0004] Generally, powders and granules consisting of spherical particles of silica-based composite oxides are produced by the so-called sol-gel method, in which hydrolyzable (condensable) compounds such as silicon or various metal alkoxides are hydrolyzed and dehydrated and condensed in a basic aqueous solution. In the sol-gel method, adding only a silica raw material compound to a basic aqueous solution to form a silica core (a seed or nucleus for particle growth) and then adding a mixture of the silica raw material compound and a metal oxide raw material compound to grow a composite oxide layer around the silica core is believed to improve the particle size distribution of the resulting powder and granules (i.e., powders and granules consisting of spherical particles with a uniform particle size are obtained) (Patent Document 3). Powders and granules consisting of spherical particles of silica-titanium group-based composite oxides used as dental fillers are also often produced by this method (see, for example, Production Examples 5 and 6 of Patent Document 2).

[0005] In the field of dental cutting blanks, which have become increasingly popular in recent years with the advancement of digital technology, a hybrid resin blank for dental cutting (hereinafter, the hybrid resin blank for dental cutting may also be simply referred to as an "HR blank") is known, which has a cutting portion made of HR blended with the above-mentioned silica-titanium group composite oxide powder (see Patent Document 4). Note that the dental cutting blank refers to a dedicated cutting body (also called a mill blank) that can be attached to a cutting machine of a cutting system (CAD / CAM system) that uses computer-aided design (CAD) and computer-aided manufacturing (CAM) technology, and typically includes a block-shaped cutting portion of a predetermined shape made of a non-metallic material and a member for attaching this to the cutting machine. Then, using a CAD / CAM system, the part to be machined is machined (CAM) into the prosthetic shape designed by CAD based on digital information such as the shape of the oral cavity and the model shape, and a dental restoration of the desired shape is produced with high precision.

[0006] Incidentally, when HR is used as a dental prosthetic material, it is necessary to use a colorant such as a pigment that is toned to a color that approximates the color of natural teeth (expressed by an index consisting of a combination of a mixed index of hue, lightness, and saturation, or an index that takes hue, lightness, and saturation into consideration. Hereinafter, a color specified by such an index will also be referred to as a "shade.") from the viewpoint of aesthetics. Since the color (shade) of natural teeth varies from person to person, it is common to prepare a plurality of HR and CR products that are toned to different predetermined colors (shades), and select from among them the one that matches the color of the tooth to be restored or the color (shade) of the surrounding teeth.

[0007] Such color (shade) selection (commonly referred to as "shade taking") is generally performed using a tooth color sample called a shade guide. There are various shade guides, each designed to facilitate color determination by the number of color samples and the configuration of the retaining device that holds the color samples. The most widely used is "VITA Classical" (product name) manufactured by VITA, which consists of a total of 16 color samples and allows the color of the restored area to be determined by comparing the shade guide with the color of the restored area and surrounding teeth. In the VITA shade guide, colors from A to D are classified by lightness and represented by symbols. That is, if the 16 shades are classified into system A (reddish-brown), system B (reddish-yellow), system C (gray), and system D (reddish-gray), and arranged in order of brightness (high to low), the order is "B1 → A1 → B2 → D2 → A2 → C1 → C2 → D4 → A3 → D3 → B3 → A3.5 → B4 → C3 → A4 → C4." When HR dental materials or CR are commercialized (made into products), they are often available in the above 16 shades (the appearance color of the HR or CR hardened body) or several shades selected from among them.

[0008] Japanese Patent Publication No. 3-10603 Japanese Patent Publication No. 8-12305 Japanese Patent Publication No. 1-38044 Japanese Patent Publication No. 2017-213394

[0009] The inventors have conducted studies and confirmed that HRs prepared using silica-based composite oxide powders of silica-zirconia oxide synthesized using a sol-gel method as described in Patent Document 2 and formulated as an inorganic composition as described in Patent Document 2 have excellent mechanical strength, abrasion resistance, and surface smoothness. On the other hand, it has been found that the color tone observed visually with the toned HR may vary depending on the thickness. Specifically, it has been found that when the HR is thin in the form of a dental crown, the blue tint becomes stronger, and when the HR is thick, the red tint becomes stronger. It is well known that the appearance color of HRs changes depending on their thickness because they have a certain degree of transparency. However, it has been little recognized that the balance between the blue and red tints changes depending on the thickness.

[0010] If the color tone changes depending on the thickness of the HR, depending on the degree of this change, it will cause confusion in the shade-taking of HR dental materials and CRs offered as products. In other words, the shades available for each product must be determined by the external color of the HR (or CR hardened body) having a predetermined thickness (hereinafter also referred to as the "standard thickness"). If there is a difference between the thickness of the HR (or CR hardened body) in the actual use form (in the state processed into a prosthesis or filled state) and the standard thickness, a color difference (the degree of discrepancy in the external color) will occur depending on the size of the difference.

[0011] For example, if the shade of an HR blank with a rectangular parallelepiped cut portion measuring approximately 1.5 cm x 1.5 cm x 2 cm is determined using a standard thickness of 1 mm, using a HR that causes the above-mentioned color shift, the external color of the cut portion will be redder than the determined shade. This not only misleads users who are unaware of the above-mentioned color shift, but also leads to the misunderstanding that the product shade is incorrect. In principle, if the thickness of the main part of the actually produced prosthesis differs from the standard thickness, the desired color harmony cannot be achieved.

[0012] Therefore, the present invention aims to clarify what type of HR changes the balance of blue and red in appearance color depending on the thickness, to provide a dental hardenable composition that can give a toned HR that does not cause color shift due to the thickness, and ultimately to provide an HR blank having a machined portion made of a toned HR that does not cause color shift due to the thickness.

[0013] The present invention is intended to solve the above-mentioned problems, and a first aspect of the present invention is a dental curable composition comprising: 100 parts by mass of a radically polymerizable monomer; and 100 to 800 parts by mass of silica-based composite oxide powder and granules, which are composed of a composite oxide of silicon and a metal containing at least titanium or zirconium, and which have a silica content of 80 to 92 mol %, an average primary particle diameter of 350 to 600 nm, and are spherical particles having no internal silica core.

[0014] In the dental curable composition of the above form (hereinafter also referred to as "dental curable composition of the present invention"), the standard deviation of the average primary particle size is preferably 1.00 to 1.30.

[0015] The dental curable composition of the present invention preferably further contains a pigment.

[0016] A second aspect of the present invention is a dental cutting blank having a cuttable portion, characterized in that the dental cutting blank has a cuttable portion comprising a hardened body of a dental hardenable composition (hereinafter also referred to as the "dental cutting blank of the present invention").

[0017] A third aspect of the present invention comprises the steps of: preparing a raw material solution by dissolving a condensable silicon compound and a condensable metal compound in a first solvent containing a first organic solvent; and adding the raw material solution to a basic solution containing a second solvent containing a second organic solvent and water to hydrolyze and condense the condensable silicon compound and the condensable metal compound, thereby precipitating silica-based composite oxide powder particles composed of spherical particles having a silica content of 80 to 92 mol% and comprising a composite oxide of silicon and a metal containing at least titanium or zirconium; wherein the content of methanol in the first organic solvent is 80% by mass or more; and the total content of the alcohol having an alkyl group with 3 carbon atoms and the alcohol having an alkyl group with 4 to 5 carbon atoms in the second organic solvent is 80% by mass or more, and the content of the alcohol having an alkyl group with 3 or less carbon atoms is 5 to 50% by mass; The method for producing silica-based composite oxide powder granules is characterized in that the raw material solution is added to the basic solution so that the content of the alcohol having an alkyl group having 3 to 5 carbon atoms is 65 mass% or more relative to the total mass of the first organic solvent and the second organic solvent, thereby precipitating the silica-based composite oxide powder granules having an average primary particle size of 350 to 600 nm and having no silica core inside the spherical particles.

[0018] In the manufacturing method of the above embodiment (hereinafter also referred to as the "manufacturing method of the present invention"), the raw material solution preparation step preferably includes the steps of: mixing a silicon alkoxide, methanol, water, and an acid to prepare a first composition in which a partial hydrolysate of the silicon alkoxide and / or an oligomer condensed from the partial hydrolysate is dissolved; mixing a metal alkoxide of the metal with a polar organic solvent capable of dissolving the metal alkoxide to prepare a second composition in which at least one of the metal alkoxide, its partial hydrolysate, and the oligomer condensed from the partial hydrolysate is dissolved; and mixing the first composition and the second composition to prepare the raw material solution. It is also preferable that the standard deviation of the average primary particle size is within a range of 1.00 to 1.30.

[0019] A fourth aspect of the present invention is a dental filler to be blended into a dental curable composition containing a radically polymerizable monomer, characterized in that the dental filler is composed of a composite oxide of silicon and a metal containing at least titanium or zirconium, has a silica content of 80 to 92 mol %, an average primary particle size of 350 to 600 nm, a standard deviation of the average primary particle size within a range of 1.00 to 1.30, and is a silica-based composite oxide powder granule consisting of spherical particles having no internal silica core.

[0020] In the dental filler of the above embodiment (hereinafter also referred to as "dental filler of the present invention"), the radical polymerizable monomer is a (meth)acrylic compound-based radical polymerizable monomer, and the refractive index of the spherical particles at 25°C with respect to light having a wavelength of 589 nm is n Ｆ and the refractive index of the cured product of the radical polymerizable monomer is represented by n Ｐ When expressed as: Formula: 0.01<n Ｆ -n Ｐ It is preferable that the dental filler satisfies the condition of <0.1.

[0021] The dental curable composition of the present invention is capable of providing a cured product that is excellent in strength, ease of cutting and polishing, and aesthetics, similar to conventional dental curable compositions in which silica-based complex oxide powder particles are blended with an inorganic filler. In addition, by using a silica-based complex oxide powder particle (which also constitutes the dental filler of the present invention) that satisfies specific conditions as the powder particle, the dental curable composition has the advantage of being less susceptible to the color shift that occurs due to the thickness of the cured product.

[0022] Therefore, the dental cutting blank of the present invention, which has a hardened body of the dental hardenable composition of the present invention as the cutting part, has the advantage that shade taking can be performed based on the external color tone (shade) of the cutting part, even though the cutting part contains silica-based composite oxide spherical particles, and therefore the product is less likely to feel unnatural.

[0023] Furthermore, according to the production method of the present invention, it is possible to efficiently produce silica-based composite oxide powder particles that, when blended into a dental hardenable composition, are less likely to cause color shift due to the thickness of the hardened product.

[0024] 1. Overview of the Invention The present inventors investigated the cause of the phenomenon in which the external color of a head roller varies depending on the thickness when a silica-based composite oxide powder of silica-zirconia oxide synthesized by a sol-gel method such as that described in Patent Document 2 is used for the head roller. As a result, they discovered that this phenomenon is prominent when the spherical particles constituting the silica-based composite oxide powder of silica-zirconia oxide have a core (silica core) composed only of silica components, but is less likely to occur when the powder is composed of particles composed entirely of composite oxide (also referred to as coreless particles) without such a silica core, and that when spherical particles of a silica-titanium group-based silica-based composite oxide such as silica-zirconia oxide are produced under conditions in which the titanium group-based oxide composition ratio is high and no silica core is formed, it is extremely difficult to obtain a powder composed of spherical particles with a relatively large particle size, such as an average primary particle size of 350 nm or more.

[0025] Therefore, further investigation was conducted on the conditions for producing a powder or granule composed of spherical coreless particles of a composite oxide of silica and a metal oxide, such as a silica-titanium group composite oxide, having an average primary particle diameter of 350 nm or more. As a result, the inventors discovered that the above-mentioned object can be achieved by adding a raw material solution, in which a condensable silicon compound, which is the raw material for the silica component, and a condensable metal compound, which is the raw material for the metal oxide component, are dissolved in an organic solvent (first organic solvent), to a basic aqueous solution containing aqueous ammonia and a water-soluble organic solvent (second organic solvent) to precipitate spherical powder particles, if (i) the organic solvent (first organic solvent) contained in the raw material solution is made primarily of methanol, (ii) the second organic solvent in the basic aqueous solution contains a combination of an alcohol having an alkyl group containing 1 to 3 carbon atoms and an alcohol having an alkyl group containing 4 to 5 carbon atoms, and the composition of the second organic solvent is controlled, and (iii) 65% by mass or more of the total mass of all organic solvents excluding water in the basic solution after the addition of the raw material solution (i.e., the first and second organic solvents) is the alcohol having an alkyl group containing 3 to 5 carbon atoms, thereby completing the present invention. The spherical particles constituting the silica-based composite oxide powder particles obtained by this production method of the present invention do not have a silica core inside.

[0026] The reason why the appearance color of a HR changes depending on its thickness when conventional silica-based composite oxide spherical powder particles having a silica core are used is not entirely clear, and the present invention is not bound by any theory. However, the inventors believe that the reason is as follows: When a HR has a silica core, the difference in refractive index between the silica core and the surrounding composite oxide shell is different, so that the silica core is recognized as a fine particle. When the HR is thin, so-called Rayleigh scattering occurs in transmitted light, and blue light of the incident light is scattered (hereinafter, this scattered light will also be referred to as "blue scattered light"). This results in a bluish appearance. In addition, in dental curable compositions containing silica-based composite oxide spherical powder particles having a silica core, the amounts of red and yellow pigments added are often increased to suppress the influence of the blue scattered light. In such cases, as the thickness of the cured product increases, the color tone of the pigment becomes more intense, which is thought to be one of the reasons why the color tone of the cured product appears reddish. Here, the silica core acts as a nucleus for grain growth and is a particle consisting essentially of silica. There are no particular limitations on the shape or size of the silica core, but it is typically spherical and has a particle diameter of 0.010 to 0.40 μm.

[0027] Furthermore, it is believed that the reason why large particle diameters (powder particles with a large average primary particle diameter) can be obtained without using coreless silica by controlling the type of solvent is that the condensable silicon compound and the condensable metal compound react in the raw material solution to form a soluble complex (i.e., an oligomer having both silicon atoms and metal atoms in its structure), and that the rate of particle nucleation slows down when the raw material solution is added to a basic aqueous organic solution (basic aqueous solution) (a large number of nuclei are no longer formed at once), allowing the particles to grow.

[0028] As described above, it is extremely difficult to obtain relatively large particles, such as spherical particles of silica-based titanium-based composite oxides (e.g., silica zirconia), without forming a silica core, having an average primary particle size of 350 nm or more. To the best of the inventors' knowledge, no dental filler material has been known that is composed of such large-particle silica-coreless spherical silica-titanium-based composite oxide particles. The dental curable composition of the present invention was only made possible by the manufacturing method of the present invention, which enables efficient production of the large-particle silica-coreless silica-titanium-based composite oxide particles that constitute such a dental filler (i.e., the dental filler of the present invention). Therefore, in the following section "2. Details of the Present Invention," (1) the manufacturing method of the present invention will be explained, followed by detailed descriptions of (2) the dental filler of the present invention, (3) the dental curable composition of the present invention, and (4) the dental cutting blank of the present invention.

[0029] In this specification, unless otherwise specified, the evaluation "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 a notation, when a unit is assigned only to the numerical value y, the unit also applies to the numerical value x. Furthermore, in this specification, the term "composite oxide" refers to a composite of multiple types of oxides, and each composition thereof is expressed as the ratio of the content (moles) of one specific type of oxide constituting the composite oxide to the total amount (moles) of oxides constituting the composite oxide, as the content of the specific type of oxide. Furthermore, the term "(meth)acrylic" refers to both "acrylic" and "methacrylic." Similarly, the term "(meth)acrylate" refers to both "acrylate" and "methacrylate," and the term "(meth)acryloyl" refers to both "acryloyl" and "methacryloyl."

[0030] 2. Details of the Invention (1) Manufacturing Method of the Invention (1-1) Overview The manufacturing method of the invention is a method for producing a silica-based composite oxide powder, which is a composite oxide of silicon and (one or more) metals containing at least titanium or zirconium, and has a silica (silicon oxide) content of 80 to 92 (mol %), and similarly to the production of a powder consisting of coreless spherical particles by the conventional so-called sol-gel method, the method comprises the following steps of preparing a raw material solution and precipitating a silica-based composite oxide powder. The silica content, as a silicon composition ratio, is expressed as the ratio of the silica content (mol) to the total amount (mol) of oxides constituting the composite oxide.

[0031] A raw material solution preparation step is a step of preparing a raw material solution in which a condensable silicon compound serving as a raw material for the silica component and at least one condensable metal compound serving as a raw material for the metal oxide component of the silica-based composite metal oxide constituting the target spherical particles are dissolved in a first solvent containing a first organic solvent. Here, the first solvent may contain water. Furthermore, the condensable silicon compound and the condensable metal compound may react in the raw material solution to form a soluble complex. The ratio of silicon atoms derived from the condensable silicon compound to at least one metal atom derived from the condensable metal compound contained in the raw material solution corresponds to the composition of the target silica-based composite oxide. For example, the raw material solution contains dissolved condensable compounds such as tetraethyl silicate (condensable silicon compound) and tetra(n-butoxy)zirconate (condensable metal compound). Silica-based composite oxide powder precipitation step: A step of adding the raw material solution to a basic solution in which a basic compound is dissolved in a second solvent containing water and a second organic solvent (a water-soluble organic solvent), and hydrolyzing and condensing the condensable silicon compound and the condensable metal compound, thereby precipitating silica-based composite oxide powder consisting of spherical particles.

[0032] (i) an organic solvent having a methanol content of 80% by mass or more is used as the organic solvent excluding water in the raw material solution (first organic solvent); (ii) a water-soluble organic solvent which can contain an alcohol having a short-chain alkyl group of 1 to 5 carbon atoms is used as the water-soluble organic solvent (second organic solvent), in which the total content of the alcohol having an alkyl group of 3 carbon atoms and the alcohol having an alkyl group of 4 to 5 carbon atoms is 80% by mass or more, and the content of the alcohol having an alkyl group of 3 or less carbon atoms is 5 to 50% by mass; and (iii) further, by using alcohols having an alkyl group of 3 to 5 carbon atoms to account for 65% by mass or more of the total mass of all organic solvents excluding water in the basic solution (first and second organic solvents) after the raw material solution is added, silica-based composite oxide powder particles are precipitated in the precipitation step, which are spherical particles that do not have a silica core (a core consisting only of silica) inside the particles, and the average primary particle size of the precipitated powder particles is 350 to 600 nm.

[0033] When using raw material solutions containing typical condensable silicon compounds or condensable metal compounds, the concentrations of organic substances such as alcohols produced by hydrolysis are low, and the influence of these organic substances is small, making it difficult to accurately analyze the concentrations of various alcohols in each solution. For this reason, the content of each alcohol specified in (i) to (iii) above is calculated based on the amount of organic solvent used as the solvent. The average primary particle size of the silica-based composite oxide powder (inorganic powder or inorganic filler consisting of spherical particles) in this invention refers to the average primary particle size determined by image analysis of a scanning electron microscope (SEM) image. The average primary particle size is calculated by measuring the maximum diameter (nm) of at least 30 arbitrarily selected particles based on an image (or photograph) obtained by observing a powder sample with an SEM at a magnification of 5,000 to 100,000 times so that at least 100 spherical particles whose overall shape can be confirmed are included in the field of view, and then dividing the sum by the number: n (a natural number ≧30). That is, the maximum diameter of each particle is expressed as x ｉ (where i is a natural number from 1 to n), and the average primary particle diameter is x ＡＶ When expressed as xＡＶ = (Σx ｉ ) / n. Here, commercially available image analysis software may be used to measure the maximum diameter (nm) of each particle. It is known that spherical particles obtained by the so-called sol-gel method have a uniform particle size, with extremely large particles and extremely small particles being almost absent, and this is also true in the production method of the present invention. Therefore, the average primary particle size determined by the above method can be said to represent the overall average primary particle size.

[0034] As described above, when a typical sol-gel method is employed, it is difficult to obtain large-diameter spherical particles of silica-based composite oxide without silica cores. In contrast, in the production method of the present invention, by controlling the composition of the first organic solvent in the raw material solution, the composition of the second organic solvent (the water-soluble organic solvent in the basic solution), and the mixing ratio of the raw material solution and the basic solution, the composition of all organic solvents (the first organic solvent and the second organic solvent) excluding water in the basic solution after the raw material solution is added is controlled, which presumably favorably controls the nucleation rate and particle growth rate, making it possible to efficiently obtain large-diameter spherical particles of silica-based composite oxide without silica cores.

[0035] As shown in the comparative examples described later, when the condition (i) is not satisfied and the methanol concentration in all organic solvents excluding water (first organic solvent) in the raw solution (hereinafter also referred to as the "methanol concentration in the first organic solvent of the raw solution") is less than 80 mass%, aggregation of particles is likely to occur, making it impossible to obtain particles with a high degree of uniformity. Furthermore, when the water-soluble organic solvent (second organic solvent) in the basic aqueous solution does not satisfy the condition (ii), aggregation of particles is likely to occur, making it impossible to obtain particles with a high degree of uniformity, and it is also impossible to grow particles to 350 nm or more. Furthermore, if the condition (iii) is not satisfied and the concentration of the alcohol having an alkyl group having 3 to 5 carbon atoms in all organic solvents (first organic solvent and second organic solvent) excluding water in the basic solution after the addition of the raw material solution (hereinafter also referred to as the "specific alcohol concentration in the organic solvent of the basic solution after the addition of the raw material solution") is less than 65 mass%, precipitation of core particles is promoted, the particle size of the spherical particles of silica-based composite oxide becomes small, and the particles cannot grow large, and as a result, a powder having an average primary particle size of 350 nm or more cannot be obtained. From the viewpoint of effectiveness, the methanol concentration in the first organic solvent of the raw material solution is preferably 80 to 98 mass%, and the specific alcohol concentration in the organic solvent of the basic solution after the addition of the raw material solution is preferably 65 to 85 mass%.

[0036] According to the production method of the present invention, it is possible to obtain a powder or granule comprising the spherical particles having a narrow particle size distribution (uniform particle size), for example, a standard deviation of the average primary particle size in the range of 1.00 to 1.30, or even in the range of 1.00 to 1.25. Furthermore, it is possible to obtain a powder or granule comprising spherical particles having an average shape uniformity of 0.6 to 0.7, or especially 0.8 to 0.9, which is close to a perfect sphere.

[0037] The standard deviation of the average primary particle diameter is calculated by the formula: standard deviation={(x ＡＶ +σ) / x ＡＶThe average uniformity is defined as the average ratio of the minor axis to the major axis of the spherical particles, and the major axis, which is the maximum diameter measured for the core particles of the n (a natural number of 30 or more, preferably 100 or more) spherical particles, is defined as L. ｉ The minor axis, which is the diameter perpendicular to the major axis, is B ｉ When this is done, the formula is: Average uniformity = {Σ(B ｉ / L ｉ ) / n}. Each step of the production method of the present invention will be described in detail below, including the raw materials and organic solvents used.

[0038] (1-2) Details (A) Raw Material Solution Preparation Step In the raw material solution preparation step, a raw material solution is prepared in which a condensable silicon compound serving as a raw material for the silica component, which is an oxide of silicon (not metal), and at least one condensable metal compound serving as a raw material for the metal oxide component of the silica-based composite metal oxide constituting the spherical particles of the target powder or granules are dissolved in a first solvent containing a first organic solvent. The first solvent may contain water. In the raw material solution, the condensable silicon compound and the condensable metal compound may react to form a soluble complex. Furthermore, the quantitative ratio of silicon atoms derived from the condensable silicon compound to at least one metal atom derived from the condensable metal compound contained in the raw material solution corresponds to the composition of the particles constituting the target silica-based composite oxide powder or granules.

[0039] Here, the condensable silicon compound is a compound that grows siloxane bonds three-dimensionally by condensation polymerization (composition formula: SiO ２"Condensable metal compound" refers to a compound capable of forming a silica structure (represented by the formula (I)), typically a silicon alkoxide and / or a derivative thereof. For example, in the first composition, this corresponds to a partial hydrolyzate of a silicon alkoxide formed under acidic conditions and / or an oligomer obtained by condensation of the partial hydrolyzate. Furthermore, "condensable metal compound" refers to a compound capable of growing metal atom-oxygen atom bonds three-dimensionally through condensation polymerization to form a stable oxide structure according to the type of metal atom, typically a metal alkoxide and / or a derivative thereof. For example, in the second composition, this corresponds to at least one selected from the group consisting of metal alkoxides, partial hydrolyzates thereof, and oligomers obtained by condensation of these.

[0040] In the raw material solution preparation step of the production method of the present invention, in order to efficiently obtain silica-based composite oxide powder particles without silica cores having an average primary particle diameter of 350 to 600 nm, it is necessary to set the methanol concentration in the organic solvent (first organic solvent) of the raw material solution to 80 mass % or more, preferably 85 to 95 mass %.

[0041] The organic solvent (other than methanol) that accounts for 20% by mass or less, preferably 10 to 18% by mass, of the total organic solvent (first organic solvent) is a polar organic solvent, specifically an alcohol such as 2-propanol, 1-butanol, 2-methyl-1-propanol, etc. The concentration of the condensable silicon compound in the raw material solution is usually 1.1 to 1.9 mol / L, preferably 1.6 to 1.8 mol / L, expressed in moles / L equivalent to silicon alkoxide.

[0042] From the viewpoints of ease of operation and ease of composition control, the raw material solution preparation step preferably includes: (a1) a step of mixing silicon alkoxide, methanol, water, and acid to prepare a first composition (silica component raw material composition) in which a partial hydrolyzate of silicon alkoxide and / or an oligomer (condensable silicon compound) formed by condensation of the partial hydrolyzate is dissolved (also referred to as a first composition preparation step); (a2) a step of mixing metal alkoxide of (one or more) metals containing at least titanium or zirconium and a polar organic solvent capable of dissolving the metal alkoxide to prepare a second composition (metal oxide component raw material composition) in which at least one (condensable metal compound) selected from the group consisting of the metal alkoxide, its partial hydrolyzate, and an oligomer (condensable silicon compound) formed by condensation of the partial hydrolyzate is dissolved (also referred to as a second composition preparation step); and (a3) ​​a step of preparing the raw material solution using the first composition and the second composition (also referred to as a raw material solution preparation step). Each of the above steps will be described in detail below.

[0043] (A1) First Composition Preparation Step In the first composition preparation step, which is a silica component raw material composition, silicon alkoxide, methanol, water, and acid are mixed to generate a condensable silicon compound in a solution. The silicon alkoxide used in this step has the formula: Si(OR) ４ (wherein R represents an alkyl group). In particular, it is preferable to use a silicon alkoxide in which R in the formula is a methyl group, an ethyl group, an isopropyl group, or a butyl group, because it is easy to control the reactivity and to obtain particles having a uniform particle size. The silicon alkoxide does not necessarily have to exist as a monomer, and may contain condensates such as dimers and trimers.

[0044] The preferred mixing method involves adding silicon alkoxide, water, and acid to methanol held in a container at 35 to 55°C under stirring. The amount of methanol is preferably such that the number of moles of silicon alkoxide per liter of methanol is 2.0 to 3.0 mol / L, particularly 2.5 to 2.9 mol / L. The order of addition is not particularly limited; water and acid may be added first, followed by silicon alkoxide, or silicon alkoxide may be added first, followed by water and acid. Water and acid may be added separately, or in the form of an aqueous acid solution. Inorganic acids such as hydrochloric acid and sulfuric acid are preferred as acids because they are easily available industrially. The molar ratio of water to silicon alkoxide is preferably in the range of 0.1 to 1, because particles having the above-mentioned average primary particle size can be produced with high productivity. The amount of acid used is such that the amount of protons released by the acid is 2.0 x 10 molar ratio relative to the silicon alkoxide. －５ ~1.0 x 10 －３ It is preferable to add an amount that satisfies the above formula. Furthermore, after the addition is complete, it is preferable to continue stirring for about 1 to 20 hours at 35 to 55°C. By carrying out the reaction under these conditions, some of the alkoxy groups in the silicon alkoxide are hydrolyzed to form -OH, and some of these groups are further dehydrated (or dealcoholized) and condensed to form a condensable silicon compound consisting of a partial hydrolyzate and / or an oligomer formed by condensation of the partial hydrolyzate.

[0045] (A2) Second Composition Preparation Step In the second composition preparation step, which is a metal oxide component raw material, alkoxides of one or more metals containing at least titanium or zirconium are mixed with a polar organic solvent capable of dissolving the metal alkoxides. In this step, preferred examples of metal alkoxides containing titanium or zirconium include Ti(OC ３ H ７ ) ４ , Ti(OC ４ H ９ ) ４ , Zr(OC ４ H ９ ) ４ The following can be mentioned:

[0046] When metal alkoxides other than titanium or zirconium-containing metal alkoxides (also referred to as other metal alkoxides) are used in combination, examples of other metal alkoxides that can be suitably used include Ba(OC ３ H ７ ) ２ , Sr(OC ３ H ７ ) ２ , Ca(OC ３ H ７ ) ２ , Al(OC ３ H ７ ) ３ Examples of the metal alkoxide include metal alkoxides of Group 2 or 13 of the periodic table, such as titanium alkoxide, zirconium alkoxide, and alkali metal alkoxides such as sodium methoxide, sodium ethoxide, lithium methoxide, and lithium ethoxide. When other metal alkoxides are used in combination, the amount can be determined appropriately depending on the purpose, but is usually 5 to 40 mol % and preferably 10 to 25 mol % based on the total moles of the titanium- or zirconium-containing metal alkoxide and the other metal alkoxide. Because neutralizing the surface acid sites with sodium ions allows for the production of spherical particles of silica-based composite oxide with few surface acid sites, it is preferable for the amount of sodium methoxide to be 8 to 25 mol %.

[0047] The polar organic solvent for dissolving the metal alkoxide is not particularly limited as long as it is a polar organic solvent that dissolves the metal alkoxide actually used, but alcohols other than methanol, such as 2-propanol, 1-butanol, and 2-methyl-1-propanol, are preferably used because they have high solubility for metal alkoxides containing titanium or zirconium. When using multiple types of metal alkoxides, the multiple types of metal alkoxides may be dissolved in a common polar organic solvent, or each may be dissolved in advance in a different polar organic solvent (if necessary) and then mixed. The polar organic solvent that serves as the solvent for the metal oxide component raw material composition may contain water, but preferably does not contain acid, and preferably does not contain water or acid (except for water that is inevitably contained as an impurity, etc.).

[0048] The concentration of the metal alkoxide contained in the metal oxide component raw material composition is usually 1.1 to 1.9 mol / liter, preferably 1.2 to 1.8 mol / liter, expressed in terms of total mol / liter of metal alkoxide.

[0049] When using another metal alkoxide, the other metal alkoxide does not necessarily have to be prepared as a metal oxide component raw material composition, and may be added directly to the mixture of the silica component raw material composition and the metal oxide component raw material composition obtained in the raw material solution preparation step.

[0050] (A3) Raw Material Solution Preparation Step In the raw material solution preparation step, the first composition (silica component raw material composition) and the second composition (metal oxide component raw material composition) are used, specifically by mixing the two compositions, to prepare a raw material solution. The method for mixing the two compositions is not particularly limited, but it is preferable to adopt a method in which the second composition is added to the first composition under stirring and mixed. The amounts of the two compositions to be mixed may be determined depending on the composition of the desired silica-based composite oxide powder (or the spherical particles that constitute it), and are prepared according to the concentrations of the first and second compositions (for example, the concentrations of the silicon alkoxide and metal alkoxide to be mixed).

[0051] During mixing, the methanol concentration in the organic solvent (first organic solvent) of the resulting raw solution must be 80% by mass or higher, preferably 85 to 95% by mass. By setting the methanol concentration at 80% by mass or higher, the condensable silicon compound (condensable silica component raw compound) and the condensable metal compound (condensable metal oxide component raw compound) probably react in the raw solution to form a soluble complex, i.e., form an oligomer having both silicon atoms and metal atoms in its structure, which is thought to suppress separation of the condensable silicon compound and the condensable metal compound during nucleation and grain growth in the precipitation step.

[0052] Since the composition of the target silica-based composite metal oxide has a silica content of 80 to 92 (mol %), if the alkoxide concentrations in both compositions are approximately the same, the methanol concentration in the first organic solvent of the raw material solution will be approximately 80 mass % or more, but if the methanol concentration after mixing the two compositions based on the composition ratio is less than 80 mass %, it can be adjusted by adding new methanol. The required amount of methanol may be calculated and added to the first composition in advance, or may be added after mixing.

[0053] After adding the condensable metal compound (and other metal alkoxides that are added directly as needed), it is preferable to stir for about 5 to 30 minutes.

[0054] (B) Precipitation Step In the precipitation step, the raw material solution is added to a basic solution containing a second organic solvent (water-soluble organic solvent) that is miscible with water, water, and a basic compound, and spherical particles are precipitated by nucleation and particle growth to obtain silica-based composite oxide powder granules made of a silica-based composite oxide of the desired composition and having an average primary particle size of 350 to 600 nm. In this case, in order to efficiently obtain silica-based composite oxide powder particles having an average primary particle size of 350 to 600 nm, the water-soluble organic solvent (second organic solvent) used in the basic solution contains an alcohol having a short-chain alkyl group having 1 to 5 carbon atoms, and the total content of the alcohol having an alkyl group having 3 carbon atoms and the alcohol having an alkyl group having 4 to 5 carbon atoms is 80 mass% or more, preferably 85 mass% or more, and the content of the alcohol having an alkyl group having 3 or less carbon atoms is 5 to 50 mass%, preferably 6 to 40 mass%, and further, 65 mass% or more of the total mass of all organic solvents (first and second organic solvents) excluding water in the basic solution after the raw material solution is added is made up of the alcohol having an alkyl group having 3 to 5 carbon atoms (hereinafter simply referred to as "specific alcohol").

[0055] In order to satisfy the above conditions, the water-soluble organic solvent (second organic solvent) used in preparing the basic solution must be a combination of an alcohol having an alkyl group containing 3 or less carbon atoms and an alcohol having an alkyl group containing 4 to 5 carbon atoms. The water-soluble organic solvent may contain a water-soluble organic solvent other than an alcohol having an alkyl group containing 1 to 5 carbon atoms, but typically contains an alcohol having a short-chain alkyl group containing 1 to 5 carbon atoms, preferably contains a specific alcohol together with methanol and / or ethanol, and more preferably consists solely of the specific alcohol (i.e., it is more preferable that the second organic solvent is a specific alcohol). Suitable specific alcohols include 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, and 1-pentanol.

[0056] As the basic compound used in the basic solution, ammonia and sodium hydroxide are preferably used, and ammonia (water) is particularly preferably used. The concentration of the basic component (basic compound) in the basic mixed solution is preferably in the range of 15 to 20 mol %, and the concentration of water is preferably in the range of 15 to 25 mass %.

[0057] In the precipitation step, usually, only the raw material solution is added to the basic solution without adding any other solution or solvent than the raw material solution. Therefore, the amount of the basic solution to be used may be such that the concentration of the specific alcohol in the organic solvent of the basic solution after the addition of the raw material solution is 65% by mass or more, depending on the amount of the specific alcohol in the basic solution, the amount of the raw material solution to be added, and the amount and composition of the organic solvent in the raw material solution. An excess amount may be used, but it is preferable to calculate the amount to achieve a predetermined concentration and use that amount.

[0058] The method for adding the raw material solution to the basic solution in the precipitation step is not particularly limited, but a method in which the hydrolyzable raw material solution is continuously added little by little to the basic mixed solution being stirred with a stirring blade, a stirrer, or the like is preferred, as this makes it easier to obtain particles with a uniform particle size.

[0059] In the precipitation step, the average primary particle size can be controlled by the temperature of the basic solution and the dropwise addition time of the raw material solution. That is, from the viewpoint of improving the uniformity of the particle size, the temperature of the basic solution is preferably set to 35 to 55°C, and the higher the temperature, the smaller the particle size can be. The longer the dropwise addition time of the raw material solution, the better the particle shape tends to be, and the longer the dropwise addition time, the larger the particle size can be. Taking the above into consideration, it is possible to produce powder particles having an average primary particle size of 350 to 600 nm with good productivity, so it is preferable to set the temperature of the reaction tank to 40 to 50°C and the dropwise addition time to 1 to 9 hours.

[0060] After the precipitation step is completed, the precipitated powder or granules may be recovered by decantation or filtration and then dried.

[0061] (C) Other Steps In the production method of the present invention, a calcination step may be carried out in which the powder or grain is calcined in order to remove the solvent from the powder or grain and reduce the hydroxyl groups on the particle surface. In this case, the calcination temperature is preferably set to 700 to 1500°C, since this results in powder or grain having a denser crystal structure.

[0062] In addition, to improve the affinity between the silica-based composite oxide powder and the organic matrix of the dental curable composition, the particles may be subjected to a silane coupling treatment. Any known silane coupling agent may be used for the silane coupling treatment without any restrictions. Furthermore, in order to reduce the influence of strong acid sites on the particle surface, the surface may be coated with silica.

[0063] (2) Dental Filler of the Present Invention The silica-based composite oxide powder having an average primary particle size of 350 to 600 nm and consisting of spherical particles of silica-based composite oxide obtained by the production method of the present invention is suitably used as a dental filler.

[0064] In the dental filler of the present invention, the average primary particle diameter of the silica-based composite oxide powder (corresponding to the average particle diameter of the powder) is 350 to 600 nm, so that when used in combination with inorganic particles having an average particle diameter of less than 100 nm, the inorganic filler loading rate increases, and the strength of the cured product is improved. If the average particle diameter is below 350 nm, stringiness and stickiness may easily occur when mixed with a polymerizable monomer to form a composition, making it difficult to incorporate into the composition at a high loading rate. Furthermore, if the average particle diameter exceeds 600 nm, polishing properties may be reduced. From the viewpoint of obtaining higher strength, the average particle diameter is preferably 350 to 550 nm.

[0065] The individual spherical particles constituting the dental filler of the present invention may be approximately spherical, but are not necessarily perfect spheres. Generally, the average uniformity is 0.6 or more, preferably 0.8 or more.

[0066] The silica-based composite oxide constituting the dental filler of the present invention can impart preferable X-ray opacity to a dental hardenable composition and can adjust the refractive index to a preferable value. By blending the metal oxide in the above range, the refractive index of the resulting silica-based composite oxide powder can be adjusted to the range of 1.50 to 1.58.

[0067] Furthermore, the dental filler of the present invention is preferably used as a filler for a dental hardenable composition containing a radically polymerizable monomer component, wherein the radically polymerizable monomer component is a (meth)acrylic compound such as: Ｆ The refractive index of the cured (meth)acrylic compound at 25°C with respect to light having a wavelength of 589 nm is expressed as n Ｐ When expressed as: 0.01<n Ｆ -n Ｐ It is preferable to use the composition as a filler for a dental hardenable composition in which the radical polymerizable monomer component is constituted (only) by a (meth)acrylic compound, and which gives a hardened product satisfying the above condition of <0.1.

[0068] When the dental filling material of the present invention is used with such a dental curable composition, color shift is unlikely to occur even if the thickness of the cured product changes. For example, when a 1 mm-thick cured product sample: A and a 3 mm-thick cured product sample: B are prepared from a uniform cured product of a curable composition comprising 100 parts by mass of the (meth)acrylic compound, 200 parts by mass of the dental filling material of the present invention, and a photopolymerization initiator in an amount necessary for curing, and when each of them is measured using a color difference meter, the spectral reflectance of sample A at a wavelength of 450 nm is R Ａ and the spectral reflectance of sample B is R Ｂ When this is the case, the formula is: 0.8≦(R Ｂ / R Ａ ) < 2.0.

[0069] (3) Dental Curable Composition of the Present Invention (3-1) Overview The dental curable composition of the present invention comprises 100 parts by mass of a radically polymerizable monomer and 100 to 800 parts by mass of a silica-based composite oxide powder comprising spherical particles of silica-based composite oxide having an average primary particle diameter of 350 to 600 nm, the silica-based composite oxide being a composite oxide of silicon and one or more metals including at least titanium or zirconium, the silica-based composite oxide having a silica content of 80 to 92 mol %, defined as the ratio of the silica content (moles) to the total oxide content (moles) constituting the silica-based composite oxide, and the silica-based composite oxide spherical particles having no core (silica core) comprised solely of silica. By satisfying these conditions, it is possible to suppress color shifts (i.e., a change in the external color tone from blue to red) in the cured product due to differences in thickness upon curing.

[0070] The powder consisting of spherical particles of silica-based composite oxide is produced by the production method of the present invention, and the silica-based composite oxide powder corresponds to the dental filler of the present invention, as already explained in detail. Therefore, here, the other components constituting the dental curable composition of the present invention will be mainly explained.

[0071] (3-2) Details (A) Radically Polymerizable Monomer The radically polymerizable monomer may be any of (meth)acrylic compound-based radically polymerizable monomers such as (meth)acrylic compounds that can be used in dental curable compositions; and cationically polymerizable monomers such as epoxies and oxetanes; but it is preferable to use a (meth)acrylic compound. Examples of suitable polymerizable monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid, N-(meth)acryloylglycine, N-(meth)acryloylaspartic acid, N-(meth)acryloyl-5-aminosalicylic acid, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and the like. p) acrylate, 2,2-bis[(3-methacryloyloxy-2-hydroxypropyloxy)phenyl]propane, 2,2-bis(4-methacryloyloxyphenyl)propane, 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, and the like.

[0072] As the radical polymerizable monomer component, generally, multiple types of radical polymerizable monomers are used. In this case, it is preferable to determine the type and amount of polymerizable monomers so that the absolute value of the difference in refractive index between the organic matrix and the spherical particles of silica-based composite oxide in the cured product obtained by curing the dental curable composition of the present invention is within 0.1, from the viewpoint of reducing light scattering due to the difference in refractive index between the organic matrix and the spherical particles of silica-based composite oxide, thereby making the transparency of the cured product closer to that of natural tooth tissue. Specifically, the refractive index of the spherical particles of silica-based composite oxide constituting the silica-based composite oxide powder and granules at 25°C for light with a wavelength of 589 nm is n Ｆ The refractive index of the cured product of the radical polymerizable monomer of the (meth)acrylic compound at 25°C with respect to light of a wavelength of 589 nm is expressed as nＰ When expressed as: 0.01<n Ｆ -n Ｐ It is preferable to use a radical polymerizable monomer made of a (meth)acrylic compound that gives a cured product satisfying the condition <0.1.

[0073] (B) Silica-based composite oxide powder consisting of spherical particles The silica-based composite oxide powder is used in the dental filler of the present invention. The content of the silica-based composite oxide powder may be in the range of 100 to 800 parts by mass per 100 parts by mass of the radical-polymerizable monomer component, but from the viewpoint of ensuring a suitable range of fluidity of the curable composition, it is preferably 100 to 600 parts by mass, and more preferably 200 to 500 parts by mass.

[0074] (C) Polymerization initiator As the polymerization initiator, any known polymerization initiator can be used without any particular limitation. Among them, it is preferable to use a photopolymerization initiator or a thermal polymerization initiator.

[0075] As the photopolymerization initiator, a combination of a photosensitizing compound and a tertiary amine is preferred. Among them, as the photosensitizing compound, α-diketones such as camphorquinone, 9,10-phenanthrenequinone, benzyl, diacetyl, acetylbenzoyl, 2,3-pentadione, 2,3-octadione, 4,4′-dimethoxybenzyl, and acenaphthenequinone are preferred, and as the tertiary amine compound, N,N-diethyl-p-toluidine, methyl p-(N,N-dimethyl)aminobenzoate, ethyl p-(N,N-dimethyl)aminobenzoate, triethanolamine, and N-methyldiethanolamine are preferred.

[0076] Preferred thermal polymerization initiators include peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxydicarbonate, and diisopropylperoxydicarbonate. Suitable thermal polymerization initiators include 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. These polymerization initiators may be used alone or in combination of two or more.

[0077] (D) Other Additives The curable composition of the present invention is preferably used after blending a colorant, such as a pigment commonly used in dental applications, to achieve a desired color tone of the cured product. When using silica-based composite oxide powders having a silica core, it was necessary to blend a pigment component to counteract the effect of blue scattered light from the particles, depending on the thickness of the cured product during use. However, the curable composition of the present invention does not require blending a pigment component for such a purpose, and the desired (toned) color tone is less likely to change depending on the thickness of the cured product. The blend amount of the colorant, such as a pigment, is typically 800 to 8,000 ppm by mass, based on the total mass of the dental curable composition. When a cured product of the curable composition of the present invention is used as the cutting portion of a dental cutting blank, it is preferable to provide a selection of compositions that are toned to achieve the color tone of the cured product in several shades selected from the 16 shades listed above.

[0078] Furthermore, other additives such as a polymerization inhibitor and an ultraviolet absorber may be contained within the range that does not impair the effects of the present invention.

[0079] (4) Dental cutting blank of the present invention The dental cutting blank of the present invention is characterized in that by using a hardened product of the dental hardenable composition as the part to be cut (i.e., by having a part to be cut that includes a hardened product of the dental hardenable composition of the present invention), the change in appearance color between the blank form and the form after cutting is suppressed.

[0080] Apart from the above-mentioned features, the blank of the present invention is not particularly different from a conventional HR blank, and may have a holding member such as a holding pin for fixing to a cutting machine as needed. The shape and size of the part to be cut are also not particularly limited, and may be a (solid) block formed into a rectangular parallelepiped or cylindrical shape, or a (solid) disk formed into a plate or board shape.

[0081] Furthermore, it is sufficient that at least a portion of the part to be machined is composed of a hardened product of the dental hardenable composition of the present invention, and for example, it may have a so-called laminated structure in which another HR blank is laminated on a hardened product of the dental hardenable composition of the present invention.

[0082] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0083] 1. Examples, Comparative Examples, and Reference Examples Related to the Production of Silica-Based Complex Oxide Powder Abbreviations for compounds used in the production of silica-based complex oxide powder are shown below. <Condensable silicon compound> (also referred to as Si oxide raw material) TES: tetraethyl silicate <Condensable metal compound> (also referred to as metal oxide raw material) TBZ: tetra(n-butoxy)zirconate TiPT: tetra(isopropoxy)titanate NaOMe: sodium methoxide <(Water-soluble) first and second organic solvents> MeOH: methanol Alcohol having an alkyl group with 3 carbon atoms (also referred to as C3 alcohol) IPA: 2-propanol Alcohol having an alkyl group with 4 carbon atoms (also referred to as C4 alcohol) NBA: 1-butanol IBA: 2-methyl-1-propanol TBA: 2-methyl-2-propanol

[0084] Example 1 [Production and Evaluation of Silica-Based Composite Oxide Powder F1] (I) Production of Silica-Based Composite Oxide Powder F1 10 g of 0.05% by mass hydrochloric acid water and 300 g of TES (manufactured by Colcoat Co., Ltd.), a Si oxide raw material, were dissolved in 400 g of MeOH and mixed at 40°C for 4 hours to hydrolyze, thereby preparing a first composition (abbreviated as "Si raw material solution" in Table 1). Subsequently, 80 g of TBZ (manufactured by Nippon Soda Co., Ltd.), a metal oxide raw material, and 50 g of IBA, a C4 alcohol serving as a water-soluble organic solvent, were mixed to prepare Solution 1, which is a second composition (abbreviated as "metal raw material solution" in Table 1). The second composition was then added to the first composition and stirred for 10 minutes to obtain a mixed solution. To this solution, 9 g of a methanol solution (Solution 2) with a NaOMe concentration of 28% by mass was further added with stirring to prepare a raw material solution. Next, 320 g of 25% by mass aqueous ammonia was added to 100 g of IPA (C3 alcohol) and 700 g of IBA (C4 alcohol) placed in a 3 L glass reaction vessel equipped with a stirrer. The previously prepared raw material solution was then added to the basic solution over 6 hours while maintaining the temperature of the reaction vessel at 45°C. After the addition was completed, stirring was continued for 30 minutes to obtain silica-based composite oxide powder. The powder was then recovered by suction filtration and dried under reduced pressure at 80°C to obtain a white powder. The powder was calcined at 800°C for 4 hours, and the resulting powder was designated silica-based composite oxide powder F1 (hereinafter sometimes referred to as particles F1).

[0085] The conditions for the above method are summarized in Table 1. The values ​​in the raw material column in Table 1 represent the amount (unit: g) of each raw material used. As shown in Table 1, the methanol content in the organic solvent (first organic solvent) in the raw material solution was 89.0% by mass, the total content of alcohols having an alkyl group with 3 carbon atoms and alcohols having an alkyl group with 4 to 5 carbon atoms contained in the water-soluble organic solvent (second organic solvent) in the basic solution was 100% by mass, the content of alcohols having an alkyl group with 3 or fewer carbon atoms was 12.5% ​​by mass, and the content of alcohols having an alkyl group with 3 to 5 carbon atoms in all organic solvents (first and second organic solvents) excluding water in the basic solution after the raw material solution was added was 67.6% by mass. Note that "↑" in the table means "same as above."

[0086] (II) Evaluation of Silica-Based Composite Oxide Powder F1 The average primary particle size, standard deviation of particle size, average uniformity, and refractive index of the silica-based composite oxide powder F1 (particles F1) obtained by the above method were evaluated by the methods described below. The results are shown in Table 2.

[0087] <Methods for measuring average primary particle diameter, standard deviation of particle diameter, and average uniformity of silica-based composite oxide powder particles> Average primary particle diameter of silica-based composite oxide powder particles: x ＡＶ The maximum diameter (nm) of each particle is determined by processing a photograph of the powder taken at a magnification of 5,000 to 100,000 times using a scanning electron microscope (XL-30S, manufactured by Philips) using image analysis software (IP-1000PC, manufactured by Asahi Kasei Engineering Co., Ltd.) and randomly selecting n particles (where n is a natural number of 30 or more) from 100 or more particles observed within a unit field of view. ｉ (The unit is nm. i is a natural number from 1 to n.) and the sum: Σx ｉ From the following formula x ＡＶ = (Σx ｉ ) / n

[0088] The standard deviation of the average primary particle diameter was calculated as follows: For the 30 or more spherical particles in the SEM image used to determine the average primary particle diameter, the maximum diameter x of each particle was calculated as follows: ｉ and average primary particle diameter x ＡＶ The sum of the squares of the differences between (Σ(x ＡＶ -x ｉ ) ２ ) from the following formula σ = [{Σ(x ＡＶ -x ｉ ) ２} / n] １／２ The standard deviation σ (nm) of particle diameter was calculated using the following formula: Standard deviation value = {(x ＡＶ +σ) / x ＡＶ} The standard deviation was calculated by the following formula.

[0089] Furthermore, the average uniformity was calculated as follows: For each of the n (a natural number of 30 or more) spherical particles, the long diameter, which is the maximum diameter measured, was taken as L ｉ The minor axis, which is the diameter perpendicular to the major axis, is B ｉ When the ratio of the two in each particle (B ｉ / L ｉ ) sum (Σ(B ｉ / L ｉ )) from the following formula: Average uniformity = {Σ(B ｉ / L ｉ ) / n} to determine the average uniformity.

[0090] <Refractive index of silica-based composite oxide spherical particles: n Ｆ The refractive index of the particles constituting the silica-based composite oxide powder was measured by the immersion method using an Abbe refractometer (manufactured by Atago Co., Ltd.) (measurement wavelength: 589 nm). That is, in a thermostatic chamber at 25°C, 1 g of silica-based composite oxide powder was dispersed in 50 mL of anhydrous toluene in a 100 mL sample bottle. While stirring this dispersion with a stirrer, 1-bromotoluene was added dropwise little by little, and the refractive index of the dispersion at the point when the dispersion became most transparent was measured: n Ｆ The obtained value was taken as the refractive index of the spherical particles of silica-based composite oxide.

[0091] Examples 2 to 5 and 7 and Comparative Examples 1 to 4 [Production and Evaluation of Silica-Based Composite Oxide Powders F2 to F5 and F7 to F11] Silica-based composite oxide powders F2 to F5 and F7 to F11 (hereinafter sometimes referred to as particles F7 to F11, respectively) were obtained in the same manner as in Example 1, except that the raw materials and their amounts were changed as shown in Table 1. The obtained silica-based composite oxide powders were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0092] Example 6 [Production and Evaluation of Silica-Based Composite Oxide Powder F6] A silica-based composite oxide powder was synthesized in the same manner as in Example 1, except that the raw materials and their amounts were changed as shown in Table 1. The powder was then recovered by suction filtration and dried under reduced pressure at 80°C to obtain a white powder. The powder was calcined at 700°C for 4 hours, and the resulting powder was designated silica-based composite oxide powder F6. The obtained silica-based composite oxide powder F6 (hereinafter sometimes referred to as particles F6) was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0093] Reference Example 1 [Production and Evaluation of Silica-Based Composite Oxide Powder F12 Having a Silica Core Structure] 10 g of 0.05% by mass hydrochloric acid water and 270 g of TES (manufactured by Colcoat Co., Ltd.) were dissolved in 400 g of MeOH and mixed at 40°C for 4 hours for hydrolysis to obtain a first composition (silica component raw material composition). Subsequently, 80 g of TBZ (manufactured by Nippon Soda Co., Ltd.) and 50 g of IBA were mixed to obtain a second composition (metal oxide component raw material composition). The second composition was then added to the first composition and stirred for 10 minutes. Subsequently, 9 g of the above-mentioned methanol solution containing 28% by mass of NaOMe was further added to the resulting mixed solution while stirring to obtain a raw material solution. Next, 700 g of IBA and 100 g of IPA were filled into a 3 L glass reaction vessel equipped with a stirrer, and 320 g of 25% by mass aqueous ammonia solution was added to prepare an ammoniacal alcohol solution. While maintaining the temperature of the reaction vessel at 45°C, 30 g of TES was added to this solution and stirred for 30 minutes to form silica core particles in the reaction vessel. The previously prepared starting solution was added to this over 6 hours while maintaining the temperature of the reaction vessel at 45°C. After the addition was completed, stirring was continued for 30 minutes to obtain silica-based composite oxide powder particles. The powder particles were then recovered by suction filtration and dried under reduced pressure at 80°C to obtain a white powder. The powder was calcined at 800°C for 4 hours, and the resulting powder was designated silica-based composite oxide powder particles F12 (hereinafter, sometimes referred to as particles F12). The obtained silica-core-containing silica-based composite oxide powder particles F12 were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0094]

[0095]

[0096] For particles F1 to F7 produced by the production method of the present invention, the standard deviation value is within 1.30 and the average uniformity satisfies the requirement for a substantially spherical shape, indicating little adhesion and aggregation between particles. In contrast, silica-based composite oxide powders F8 and F9, which were produced under conditions that did not satisfy the requirements for the production method of the present invention, showed a large variation in the standard deviation value and a large average uniformity. This indicates that adhesion between particles occurred. Furthermore, silica-based composite oxide powders F10 and F11, which were produced under conditions that did not satisfy the requirements for the production method of the present invention, were substantially spherical, but had an average primary particle diameter that did not reach 350 nm.

[0097] 2. Examples and Comparative Examples Related to Dental Hardenable Compositions (Uncolored) The abbreviations for the compounds used in preparing the dental hardenable compositions are shown below: UDMA: 1,6-bis(methacrylethyloxycarbonylamino)trimethylhexane Bis-GMA: 2,2-bis[(3-methacryloyloxy-2-hydroxypropyloxy)phenyl]propane 3G: triethylene glycol dimethacrylate CQ: camphorquinone DMBE: ethyl p-(N,N-dimethyl)aminobenzoate HQME: hydroquinone monomethyl ether.

[0098] In preparing the dental curable compositions, monomer compositions (also referred to as matrices) M1 to M3 having the formulations shown in Table 3 were prepared in advance and used. The silica-based composite oxide granules F1 to F12 used in preparing the dental curable compositions were all surface-treated with γ-methacryloyloxypropyltrimethoxysilane to make the surface hydrophobic, and then added to and mixed with the matrix. The refractive indices before and after curing in Table 3 were measured as follows.

[0099] <Measurement of refractive index before curing> Measurement was carried out in a thermostatic chamber at 25°C using an Abbe refractometer (manufactured by Atago Co., Ltd.) (measurement wavelength: 589 nm).

[0100] <Refractive index after curing: n ＰMeasurement of > Each monomer composition was mixed with 0.2% by mass of camphorquinone, 0.3% by mass of ethyl p-(N,N-dimethyl)aminobenzoate, and 0.15% by mass of hydroquinone monomethyl ether to form a homogenous mixture, which was then placed in a mold having a hole of 7 mmφ×0.5 mm, and polyester films were pressed onto both sides of the mixture. Thereafter, a light intensity of 500 mW / cm was applied. ２ The sample was cured by irradiating it with light for 30 seconds using a halogen-type dental light irradiator ("Demetron LC", manufactured by Cybron Co., Ltd.), and then removed from the mold to prepare a cured sample. When the sample was set in an Abbe refractometer (manufactured by Atago Co., Ltd.), a solvent (bromonaphthalene) that did not dissolve the sample but had a higher refractive index than the sample was dropped onto the sample in order to bring the sample into close contact with the measurement surface, and the refractive index was measured to be the same as that before curing: n Ｐ Measurements were carried out.

[0101]

[0102] Example 8 [Preparation and Evaluation of Dental Curable Composition CR1] Under red light, 0.6 parts by weight of CQ, 1.0 part by weight of DMBE, and 0.15 parts by weight of HQME were added to 100 parts by weight of matrix M1 and mixed to prepare a uniform polymerizable monomer composition. 200 parts by weight of silica-based composite oxide powder F1 (surface-treated) was weighed into a mortar, and the above polymerizable monomer composition was gradually added under red light and thoroughly kneaded with a pestle to prepare a uniform curable paste. This paste was then degassed under reduced pressure to remove air bubbles, producing dental curable composition CR1. The spectral reflectance of the obtained CR1 was measured based on the evaluation method described below. The composition and evaluation results are shown in Table 4.

[0103] <Method for measuring the spectral reflectance of the cured product of the dental curable composition> The prepared dental curable composition CR1 was placed in a mold having holes of 7 mm diameter, 1 mm thickness, and 3 mm, and polyester films were pressed onto both sides. ２The specimens were cured by irradiating them with light for 30 seconds using a halogen-type dental light irradiator ("Demetron LC", manufactured by Cybron Co.), then removed from the mold and the surfaces were mirror-polished to obtain 1 mm thick cured specimens, Sample A, and 3 mm thick cured specimens, Sample B. The spectral reflectance of the specimens was measured using a spectrophotometer (manufactured by Tokyo Denshoku Co., Ltd., "TC-1800MKII", halogen lamp: 12V 100W, measurement wavelength range 380 to 780 nm) against a black background using black carbon tape, to obtain a spectral reflectance curve. The spectral reflectance R at a wavelength of 450 nm was read from the spectral reflectance curve, and R Ｂ / R Ａ (The subscript R indicates the name of the hardened sample) was determined.

[0104] Examples 9, 10, 14 and Comparative Example 5 Dental curable compositions CR2, 3, 7, and 8 were produced and evaluated in the same manner as in Example 8, except that the silica-based composite oxide powder particles shown in Table 4 were used. The compositions and results are shown in Table 4. In the table, "↑" means "same as above."

[0105] Examples 11 and 13: Under red light, 0.6 parts by mass of CQ, 1.0 part by mass of DMBE, and 0.15 parts by mass of HQME were added to 100 parts by mass of matrix M2 and mixed to prepare a uniform polymerizable monomer composition. 200 parts by mass of the silica-based composite oxide powder shown in Table 4 was weighed into a mortar, and the polymerizable monomer composition was gradually added under red light and thoroughly kneaded with a pestle to prepare a uniform curable paste. This paste was then degassed under reduced pressure to remove air bubbles, producing dental curable compositions CR4 and CR6, which were evaluated in the same manner as in Example 8. The composition and evaluation results are shown in Table 4.

[0106] Example 12: Under red light, 100 parts by weight of matrix M3 were mixed with 0.6 parts by weight of CQ, 1.0 part by weight of DMBE, and 0.15 parts by weight of HQME to prepare a uniform polymerizable monomer composition. 200 parts by weight of silica-based composite oxide powder F5 was weighed into a mortar, and the polymerizable monomer composition was gradually added under red light. The mixture was thoroughly kneaded with a pestle to prepare a uniform curable paste. This paste was then degassed under reduced pressure to remove air bubbles, producing dental curable composition CR5, which was then evaluated in the same manner as in Example 8. The composition and evaluation results are shown in Table 4.

[0107]

[0108] As shown in Table 4, the ratio of spectral reflectance R of CR1 to CR7, which uses silica-based composite oxide particles F1 to F7 that do not have a silica core structure, is Ｂ / R Ａ The value of R is 0.8 or more and less than 2.0, which indicates that the influence of blue scattered light is small. Ｂ / R Ａ is greater than 2.0, and it is clear that blue scattered light is exhibited.

[0109] 3. Examples and Comparative Examples Related to Dental Cutting Blanks (HR Blanks) The abbreviations for the polymerization initiators and pigments used in preparing the HR blanks are as follows: BPO: benzoyl peroxide R: red pigment (Pigment Red 166) Y: yellow pigment (Pigment Yellow 95) B: blue pigment (Pigment Blue 60)

[0110] Example 15: 20 parts by mass of matrix M1 and 1.0 part by mass of BPO were mixed, followed by the addition of 80 parts by mass of silica-based composite oxide powder F1, and the mixture was mixed using a planetary mixer until uniform. A colorant prepared by mixing 650 ppm by mass of R, 1800 ppm by mass of Y, and 1000 ppm by mass of B was added to 100 parts by mass of the paste, and a colored paste was prepared in a thickness of 1 mm, toned to an A3 shade on the VITA shade guide. The colored paste was vacuum degassed and then filled into a mold cavity having a cylindrical cavity with a thickness of 14.5 mm and a cross section of 14.5 mm x 18 mm, and then pressurized with nitrogen at 0.4 MPa in a pressure vessel and placed in a heating device at 90 ° C. The mixture was heated in this state for 15 hours to polymerize and harden, and then cooled to room temperature at a cooling rate of 20°C / min. The mixture was then removed from the mold to obtain a block-shaped colored HR (hardened product) corresponding to the cavity shape.

[0111] Plate-shaped test pieces with thicknesses of 1 mm and 3 mm and a main plane measuring 14.5 mm x 18 mm were cut from the colored HR, and the main plane was gloss-polished to prepare test pieces for visual evaluation. The test pieces for visual evaluation were placed next to an "A3" VITA shade guide against a black background, and the color compatibility was evaluated visually according to the following evaluation criteria. The results are shown in Table 5.

[0112] <Evaluation Criteria> A: The color tone matches well with the VITA Shade Guide. B: The color tone is similar to the VITA Shade Guide. C: The color tone is similar to the VITA Shade Guide, but the compatibility is poor. D: The color tone does not match with the VITA Shade Guide.

[0113] Examples 16 to 21 Colored HR (cured product) was produced in the same manner as in Example 15, except that the matrix and silica-based composite oxide powder particles used were changed to those shown in Table 5, and evaluations were carried out in the same manner as in Example 15. The results are shown in Table 5.

[0114] Comparative Example 6: 20 parts by weight of matrix M1 and 1.0 part by weight of BPO were mixed, followed by the addition of 80 parts by weight of F12, and the mixture was mixed using a planetary mixer until uniform to form a paste. A colorant prepared by mixing 850 ppm by weight of R, 2000 ppm by weight of Y, and 900 ppm by weight of B was added to 100 parts by weight of the paste, and a colored paste was prepared by toning the paste to a VITA Shade Guide A3 shade at a thickness of 1 mm. The colored paste was polymerized in the same manner as in Example 15 to produce a colored HR (cured product), which was then evaluated in the same manner as in Example 15. The results are shown in Table 5.

[0115]

[0116] As shown in Table 5, Examples 15 to 21, which satisfy the conditions of the present invention, exhibit good color matching with the VITA shade guide at both 1 mm and 3 mm thicknesses. In contrast, Comparative Example 6 exhibited good color matching with the VITA shade guide at a 1 mm thickness, but at a 3 mm thickness, it appeared to have higher saturation (stronger color) than the VITA shade guide, and its color matching was inferior to that of the Examples.

Claims

1. A step of preparing a raw material solution by dissolving a condensable silicon compound and a condensable metal compound in a first solvent containing a first organic solvent; A step of adding the raw material solution to a basic solution containing a second solvent containing a second organic solvent and water, and hydrolyzing and condensing the condensable silicon compound and the condensable metal compound to precipitate a silica-based composite oxide powder composed of a composite oxide of silicon and a metal containing at least titanium or zirconium, and consisting of spherical particles having a silica content of 80 to 92 mol%; comprising; in the first organic solvent, the methanol content is 80% by mass or more; in the second organic solvent, the total content of an alcohol having an alkyl group with 3 carbon atoms and an alcohol having an alkyl group with 4 to 5 carbon atoms is 80% by mass or more, and the content of an alcohol having an alkyl group with 3 or less carbon atoms is 5 to 50% by mass; By adding the raw material solution to the basic solution so that the content of the alcohol having an alkyl group with 3 to 5 carbon atoms is 65% by mass or more with respect to the total mass of the first organic solvent and the second organic solvent, the average primary particle diameter is 350 to 600 nm, and the silica-based composite oxide powder having no silica core inside the spherical particles is precipitated, characterized in that; A method for producing a silica-based composite oxide powder.

2. The step of preparing the raw material solution is; A step of preparing a first composition in which a partial hydrolyzate of the silicon alkoxide and / or an oligomer obtained by condensation of the partial hydrolyzate is dissolved by mixing a silicon alkoxide, methanol, water, and an acid; A step of preparing a second composition in which at least one of the metal alkoxide, its partial hydrolyzate, and an oligomer obtained by condensation of the partial hydrolyzate is dissolved by mixing the metal alkoxide of the metal and a polar organic solvent that dissolves the metal alkoxide; A step of mixing the first composition and the second composition to prepare the raw material solution; comprising; The method for producing a silica-based composite oxide powder according to Claim 1.

3. The standard deviation value of the average primary particle diameter is in the range of 1.00 to 1.30; The method for producing a silica-based composite oxide spherical powder according to Claim 1 or 2.

4. It is composed of a composite oxide of silicon and a metal containing at least zirconium, has a silica content of 80 to 92 mol%, an average primary particle diameter of 350 to 600 nm, and a standard deviation value of the average primary particle diameter within the range of 1.00 to 1.30, and is a silica-based composite oxide powder composed of spherical particles having no silica core inside. A dental filling material formulated in a dental curable composition containing a radically polymerizable monomer.

5. The radically polymerizable monomer is a (meth)acrylic compound-based radically polymerizable monomer, Let n represent the refractive index of the spherical particles with respect to light at 25°C and a wavelength of 589 nm. Ｆ When the refractive index of the cured product of the radically polymerizable monomer is represented by n Ｐ then, Formula: 0.01 < n Ｆ -n Ｐ < 0.1 satisfying The dental filling material according to claim 4.

6. Radically polymerizable monomer: 100 parts by mass, and It is composed of a composite oxide of silicon and a metal containing at least zirconium, has a silica content of 80 to 92 mol%, an average primary particle diameter of 350 to 600 nm, and is a silica-based composite oxide powder composed of spherical particles having no silica core inside: 100 to 800 parts by mass A dental curable composition containing the same.

7. The standard deviation value of the average primary particle diameter is 1.00 to 1.30 The dental curable composition according to claim 6.

8. Further containing a pigment The dental curable composition according to claim 6 or 7.

9. Having a machined part containing a cured body of the dental curable composition according to any one of claims 6 to 8 A dental blank for cutting.