Organic-inorganic composite filler and dental hardenable composition containing said organic-inorganic composite filler

Abstract

To provide organic-inorganic composite fillers that can reduce polymerization shrinkage, increase the mechanical strength of a hardened body, and further maintain the operability and shape retention of the dental curable composition paste before curing well for a long period of time, when blended in a dental curable composition.SOLUTION: In organic-inorganic composite fillers which are composed of porous organic-inorganic composite particles consisting of a composite of an organic resin component and inorganic particles with an average primary particle size of 10 to 1500 nm and which have a cumulative pore volume of 1 to 500 nm of 0.01 to 0.30 cm3 / g, two types of organic-inorganic composite fillers each composed of (1) particles with curved surfaces at least in part and (2) particles that do not have a curved shape are mixed and used, so that the particles of above (1) and (2) co-exist as the porous organic-inorganic composite particles, further in which the content of particles with a particle diameter of 5 μm or less in all constituent particles is set to less than 15 vol%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel organic-inorganic composite filler and a dental curable composition containing the organic-inorganic composite filler. [Background technology]

[0002] Dental hardenable compositions are generally paste-like compositions containing polymerizable monomers, fillers, and polymerization initiators as their main components. The type, shape, particle size, and filling amount (rate) of the filler used affect the ease of use of the dental hardenable composition and the aesthetics and mechanical strength of the hardened product obtained by hardening.

[0003] For example, when a dental curable composition is blended with an inorganic filler having a large particle size, the mechanical strength of the cured product increases, but the surface smoothness and abrasion resistance of the cured product decrease, making it difficult to obtain a glossy finish similar to that of natural teeth. On the other hand, when a fine inorganic filler having an average particle size of 1 μm or less is blended, the surface smoothness and abrasion resistance of the cured product can be improved, but the fine inorganic filler has a large specific surface area, which significantly increases the viscosity. Furthermore, when the amount of inorganic filler blended is reduced, not only does the amount of shrinkage of the cured product increase due to polymerization shrinkage of the monomer when the dental curable composition hardens, but the mechanical strength of the cured product also decreases.

[0004] To avoid this trade-off, the use of organic-inorganic composite fillers has been proposed (see, for example, Patent Documents 1 and 2). Organic-inorganic composite fillers are composite fillers containing fine inorganic fillers in an organic resin. By using such fillers, it is possible to maintain the excellent surface smoothness and abrasion resistance of fine inorganic fillers and also reduce polymerization shrinkage. If the amount of organic-inorganic composite filler added is too high, the paste becomes rough and the paste becomes difficult to handle. However, by using the filler in combination with an inorganic filler (inorganic particles) with an average particle size of 0.1 to 1 μm, this deterioration in handleability can be prevented, resulting in a paste-like dental curable composition with excellent handleability (see Patent Document 2).

[0005] A common method for producing the organic-inorganic composite filler is to obtain a cured product by polymerizing a paste-like curable composition in which a fine inorganic filler and a polymerizable monomer are pre-kneaded, and then crushing the cured product. Dental curable compositions containing an organic-inorganic composite filler produced by this method have a problem in that they have low strength as dental curable compositions due to weak bonding at the interface between the matrix and the organic-inorganic composite filler.

[0006] As an organic-inorganic composite filler that can solve the above problems, a filler having a pore volume (wherein pores have a diameter of 1 to 500 nm) of 0.01 to 0.30 cm3 measured by mercury intrusion porosimetry is used. 3 An organic-inorganic composite filler having an aggregate gap of 0.1 / g has been proposed (see Patent Document 3). Patent Document 3 also describes that a dental curable composition containing such a porous organic-inorganic composite filler, a polymerizable monomer, and a polymerization initiator uses an organic-inorganic composite filler having aggregate gaps, and the polymerizable monomer of the curable composition penetrates and hardens by capillary action, thereby generating an anchor effect, and the organic-inorganic composite filler is held in the cured product of the curable composition with a high interlocking force, thereby improving mechanical strength. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-80013 [Patent Document 2] International Publication No. 2015 / 125470 Brochure [Patent Document 3] International Publication No. 2011 / 115007 Brochure Summary of the Invention [Problem to be solved by the invention]

[0008] The inventors of the present invention have conducted extensive studies and found that dental curable compositions containing an organic-inorganic composite filler having aggregated gaps obtained by the method of Patent Document 3 have significantly high mechanical strength and excellent abrasion resistance and aesthetics. However, detailed studies of the paste properties and workability of dental curable compositions containing an organic-inorganic composite filler obtained by the production method described in the Examples, specifically, a method in which an aqueous suspension containing dispersed inorganic primary particles is agglomerated by spray drying to produce aggregates of the inorganic primary particles, and the resulting inorganic aggregated particles are impregnated with a polymerizable monomer containing a polymerization initiator for polymerization, have revealed that the paste state before hardening is sticky, resulting in poor workability. Furthermore, when filling a Class I molar cavity or the like, the dental curable composition has poor ability to maintain the occlusal surface shape formed. In other words, there is room for improvement in the paste workability and shape retention of the dental curable composition.

[0009] In light of the above background, an object of the present invention is to provide an organic-inorganic composite filler to be blended into a dental curable composition, which can increase the mechanical strength of a cured product of the dental curable composition, has good operability and shape retention in a paste state before hardening, and can maintain good operability for a long period of time. [Means for solving the problem]

[0010] The present invention solves the above-mentioned problems, and a first aspect of the present invention is a composite of an organic resin component (A1) made of a cured product of a polymerizable monomer (a1) and inorganic particles (B1) having an average primary particle diameter of 10 to 1500 nm, the composite comprising first porous organic-inorganic composite particles (C1) having at least a partial curved surface, the composite having an integrated pore volume of pores having a diameter of 1 to 500 nm of 0.01 to 0.30 cm as measured by a nitrogen adsorption method. 3 / g; and a composite of an organic resin component (A2) made of a cured product of a polymerizable monomer (a2) and inorganic particles (B2) having an average primary particle diameter of 10 to 1500 nm, and second porous organic-inorganic composite particles (C2) having no curved shape, wherein the cumulative pore volume of pores having a diameter of 1 to 500 nm measured by a nitrogen adsorption method is 0.01 to 0.30 cm. 3 / g It is an irregular shape with no curved surface and adjacent surfaces with an angle. a second organic-inorganic composite filler (X2); The organic-inorganic composite filler is characterized in that the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) both have an average particle size of 5 to 100 μm, and the content of particles having a particle size of 5 μm or less in the first porous organic-inorganic composite particles (C1) and the second porous organic-inorganic composite particles (C2) is less than 15% by volume.

[0011] In the organic-inorganic composite filler of the above form (hereinafter also referred to as "organic-inorganic composite filler of the present invention"), it is preferable that the ratio of the mass of the second organic-inorganic composite filler (X2) to the total mass of the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) is 10 to 85 mass%.

[0012] It is also preferred that the average content of the inorganic particles (B1) in the first porous organic-inorganic composite particles (C1) is 75 to 90 mass %, and the average content of the inorganic particles (B2) in the second porous organic-inorganic composite particles (C2) is 80 to 95 mass %.

[0013] Furthermore, it is preferable that the inorganic particles (B1) and / or (B2) contain inorganic particles having X-ray contrast properties.

[0014] A second aspect of the present invention is a dental curable composition comprising 100 parts by mass of a polymerizable monomer, 200 to 600 parts by mass of a filler, and an effective amount of a polymerization initiator, wherein 30% by mass or more of the filler is the organic-inorganic composite filler of the present invention.

[0015] In the dental curable composition of the above form (hereinafter also referred to as "dental curable composition of the present invention"), it is preferable that 30 to 70 mass % of the filler is the organic-inorganic composite filler of the present invention, and the remaining filler is mainly inorganic particles having an average primary particle diameter of 10 to 1500 nm. [Effects of the Invention]

[0016] When the organic-inorganic composite filler of the present invention is used as a filler for a dental curable composition, similar to the dental curable composition blended with the porous organic-inorganic composite filler described in Patent Document 3, it not only reduces polymerization shrinkage compared to when an inorganic filler is directly blended, but also improves the surface smoothness and abrasion resistance of the cured product, and further improves the mechanical strength of the cured product by hardening the polymerizable monomer that has infiltrated into the pores of the organic-inorganic composite filler.

[0017] In addition, when the organic-inorganic composite filler of the present invention is used, not only can the paste properties of the dental curable composition be maintained without deterioration, with a reduced stickiness and good operability even after long-term storage, but also the shape retention can be improved when the composition is used as a dental filling material and shaped into a desired shape, such as an occlusal surface shape. Furthermore, the low proportion of fine particles of 5 μm or less can prevent the paste from becoming too dry. Furthermore, since a relatively large amount of fine inorganic particles can be added while maintaining good paste properties, polymerization shrinkage can be further reduced. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a scanning electron microscope photograph of first porous organic-inorganic composite particles (C1) having at least a part of a curved surface, which constitute the first organic-inorganic composite filler (X1) used in the present invention. [Figure 2] 1 is a scanning electron microscope photograph of second porous organic-inorganic composite particles (C2) that do not have a curved surface shape and that constitute the second organic-inorganic composite filler (X2) used in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The organic-inorganic composite filler disclosed in Patent Document 3 is produced by the above-described method, and the shape of each particle constituting the organic-inorganic composite filler is essentially the same as that of inorganic aggregated particles, i.e., approximately spherical. The present inventors conducted extensive research, suspecting that changing the shape of the organic-inorganic composite filler from approximately spherical to an irregular shape might change the paste properties. As a result, they found that when a microporous aggregate composed of a composite of an organic resin component formed from a cured product of a polymerizable monomer and the inorganic primary particles is obtained and then pulverized, the excellent characteristics of the porous organic-inorganic composite filler described in Patent Document 3 are maintained while its drawbacks are compensated for, and the handleability and shape retention of a dental curable composition (paste) containing the filler can be improved. Based on these findings, the present invention provides a porous organic-inorganic composite particle aggregate comprising a composite of an organic resin component (A) made of a cured product of a polymerizable monomer (a) and inorganic particles (B) having an average primary particle diameter of 10 to 1000 nm, wherein the cumulative pore volume of pores of 1 to 500 nm as measured by a nitrogen adsorption method is 0.01 to 0.30 cm. 3 / g, wherein the content of the inorganic particles (B) in the porous organic-inorganic composite particles is 80 to 95 mass%, and each of the porous organic-inorganic composite particles constituting the organic-inorganic composite filler has an irregular shape (hereinafter also referred to as "irregular microporous organic-inorganic composite filler"), and a dental curable composition containing the same (hereinafter also referred to as "already proposed dental curable composition") have already been proposed (Patent Application No. 2020-210301).

[0020] The present inventors further investigated the effects of the irregular microporous organic-inorganic composite filler and found that a rough feeling may occur when all of the organic-inorganic composite fillers contained in a dental curable composition are irregular microporous organic-inorganic composite fillers. Therefore, as a result of further investigations to prevent this phenomenon from occurring, they discovered that (1) when a mixed filler of the substantially spherical microporous organic-inorganic composite filler and an irregular microporous organic-inorganic composite filler disclosed in Patent Document 3 is used, the rough feeling of the paste is reduced and the filler loading rate that can be incorporated into the dental curable composition can be improved, and (2) the rough feeling tends to occur when there are a large number of fine particles. The present invention was made based on these findings.

[0021] Although the reason why the use of an irregular microporous organic-inorganic composite filler improves the workability and shape retention of the paste is unclear, it is presumed that the porous organic-inorganic composite particles have an irregular shape (not approximately spherical), preferably an irregular shape with edges, which prevents stickiness and further improves shape retention. Furthermore, the suppression of the dry feeling of the paste is thought to be due to the high content of inorganic components in the porous organic-inorganic composite particles that make up the organic-inorganic composite filler and the low amount of organic resin components that have a high affinity with the matrix monomer in the dental curable composition, as well as the suppression of absorption of the monomer by the porous organic-inorganic composite particles over time because the contact area with the monomer is small when the proportion of fine particles is very low. Incidentally, although the organic-inorganic composite filler disclosed in Patent Document 3 also contains fragmented particles that are partially broken due to impact during handling, most of the fragmented particles also have curved surfaces, and unless they are actively crushed, fine particles with a particle size of 5 μm or less are hardly generated. Therefore, when this is used alone, although the paste is less likely to have a dry feeling, it is thought that the effect of improving the paste properties described above is not obtained.

[0022] The organic-inorganic composite filler of the present invention, its manufacturing method, and dental curable composition of the present invention will be described in detail below. In this specification, unless otherwise specified, the expression "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 an expression, 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 "(meth)acrylic" means both "acrylic" and "methacrylic." Similarly, the term "(meth)acrylate" means both "acrylate" and "methacrylate," and the term "(meth)acryloyl" means both "acryloyl" and "methacryloyl."

[0023] 1. Organic-inorganic composite filler of the present invention The organic-inorganic composite filler of the present invention is composed of a mixture of the following first organic-inorganic composite filler (X1) and the following second organic-inorganic composite filler (X2), wherein the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) both have an average particle size of 5 to 100 μm, and the content of particles having a particle size of 5 μm or less in the entire first porous organic-inorganic composite particles (C1) and the second porous organic-inorganic composite particles (C2) is less than 15% by volume.

[0024] First organic-inorganic composite filler (X1): A first organic-inorganic composite filler (X1) that is a composite of an organic resin component (A1) made of a cured product of a polymerizable monomer (a1) and inorganic particles (B1) having an average primary particle diameter of 10 to 1500 nm, and that is composed of first porous organic-inorganic composite particles (C1) at least a portion of whose surfaces are curved, and that has an integrated pore volume of pores with a diameter of 1 to 500 nm of 0.01 to 0.30 cm as measured by a nitrogen adsorption method. 3 / g of organic-inorganic composite filler.

[0025] Second organic-inorganic composite filler (X2): A composite of an organic resin component (A2) made of a cured product of a polymerizable monomer (a2) and inorganic particles (B2) having an average primary particle diameter of 10 to 1500 nm, and second porous organic-inorganic composite particles (C2) having no curved shape. The cumulative pore volume of pores with a diameter of 1 to 500 nm measured by a nitrogen adsorption method is 0.01 to 0.30 cm. 3 / g of organic-inorganic composite filler.

[0026] Here, "first porous organic-inorganic composite particles (C1) having at least a portion of their surfaces curved" means porous organic-inorganic composite particles that, when observed using a scanning electron microscope, have a curved shape (spherical, approximately spherical, or doughnut-shaped, or a so-called torus shape such as a dimpled shape with depressions formed on the particle surface) whose main outer surface is composed of curved surfaces, or particles of these shapes that have been broken into fragments so that the curved shape remains on at least a portion of the outer surface (see FIG. 1). The spherical or approximately spherical particles or fragments thereof that constitute the organic-inorganic composite filler described in Patent Document 3 fall into this category. Furthermore, the "second porous organic-inorganic composite particles (C2) not having a curved shape" are porous organic-inorganic composite particles that do not correspond to the above-mentioned first porous organic-inorganic composite particles (C1), and are so-called irregular particles whose entire outer surface is basically composed of broken surfaces, preferably particles having an irregular shape with edges (see Figure 2), and the particles that constitute the above-mentioned irregular microporous organic-inorganic composite filler correspond to these.

[0027] The first porous organic-inorganic composite particles (C1) and the second porous organic-inorganic composite particles (C2) are both porous organic-inorganic composite particles composed of a composite of organic resin components (A1, A2) made of cured polymerizable monomers (a1, a2) and inorganic particles (B1, B2) having an average primary particle diameter of 10 to 1500 nm. The polymerizable monomers and inorganic particles will be described in detail when explaining the manufacturing methods for each filler, but there is no particular difference between the two particles. However, the polymerizable monomers (a1) and (a2) used as raw materials for the organic resins (A1) and (A2) may be different in type. Furthermore, the inorganic particles (B1) and (B2) having an average primary particle diameter of 10 to 1500 nm may also be different in type, and their average primary particle diameters may also be different as long as they are within the above range.

[0028] The average particle diameters of the first porous organic-inorganic composite particles (C1) and the second porous organic-inorganic composite particles (C2) must be 5 to 100 μm, more preferably 10 to 100 μm, and most preferably 10 to 70 μm, in order to ensure that the filling rate of the filler that can be incorporated into the dental curable composition is not reduced and that good paste properties can be obtained. If the average particle diameter exceeds 100 μm, the fluidity of the dental curable composition tends to decrease, and the smoothness of the paste tends to decrease. On the other hand, if the average particle diameter is less than 5 μm, the filling rate of the filler that can be incorporated into the dental curable composition tends to decrease, resulting in a decrease in the mechanical strength of the cured product and increased adhesiveness of the dental curable composition, which tends to reduce operability. In particular, if the proportion of fine particles with a particle diameter of 5 μm or less is high, the paste tends to become rough. Therefore, the proportion of fine particles having a particle diameter of 5 μm or less in the first porous organic-inorganic composite particles (C1) and the second porous organic-inorganic composite particles (C2) as a whole must be less than 15% by volume, and the proportion of fine particles having a particle diameter of 5 μm or less is preferably less than 10% by volume.

[0029] The average particle size of the organic-inorganic composite filler refers to the median diameter determined based on the particle size distribution measured by a laser diffraction-scattering method. Specifically, it refers to the median diameter determined based on the particle size distribution measured by the laser diffraction-scattering method for a sample prepared by uniformly dispersing 0.1 g of the organic-inorganic composite filler in 10 mL of ethanol.

[0030] From the viewpoints of polymerization shrinkage reduction effect, abrasion resistance, and aesthetics, the average content of inorganic particles (B1) and (B2) in the first porous organic-inorganic composite particles (C1) and the second porous organic-inorganic composite particles (C2) is preferably 75 to 95 mass%. For manufacturing reasons, the average content of inorganic particles (B1) in the first porous organic-inorganic composite particles (C1) is preferably 75 to 90 mass%, particularly 77 to 88 mass%. For manufacturing reasons, the average content of inorganic particles (B2) in the second porous organic-inorganic composite particles (C2) is preferably 80 to 95 mass%, particularly 82 to 93 mass%. These reasons are: 1) particles with an average particle size of less than 5 μm are less likely to be generated by crushing during manufacturing; 2) the removal rate of fine particles with a particle size of 5 μm or less can be reduced by classification; and 3) the average particle size can be easily controlled to a range of 10 to 100 μm, particularly 10 to 70 μm.

[0031] The average content of inorganic particles can be controlled by the ratio of the amount of polymerizable monomer to the amount of inorganic particles used during production, but can also be confirmed by burning the organic-inorganic composite filler, incinerating and removing the organic resin component consisting of the cured product of the polymerizable monomer, and then measuring the weight.

[0032] In the organic-inorganic composite filler of the present invention, the cumulative pore volume of pores of 1 to 500 nm when measured by a nitrogen adsorption method for the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) described below is 0.01 to 0.30 cm 3 / g, provided that the cumulative pore volumes of the pores of 1 to 500 nm of both materials are within this range, they may be different from each other.

[0033] When the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) described below have such an integrated pore volume, when the dental curable composition of the present invention is prepared by blending the organic-inorganic composite filler of the present invention, the strength of the cured product can be increased by an anchor effect in which the polymerizable monomer component of the dental curable composition penetrates into the pores of the first porous organic-inorganic composite particles (C1) and the second porous organic-inorganic composite particles (C2) and hardens. From the viewpoint of such an effect, the integrated pore volumes of the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) are each 0.01 to 0.20 cm3. 3 / g, especially 0.03 to 0.15 cm 3 / g is preferred.

[0034] In Patent Document 3, the total pore volume of pores with diameters of 1 to 500 nm is measured by mercury intrusion porosimetry, but the pore volume of pores with diameters in the same range can also be measured by nitrogen adsorption. Furthermore, the inventors' studies have confirmed that the pores in the (X2) filler with pore diameters of 1 to 500 nm have an extremely sharp pore distribution with a peak at around 50 nm, and that there are substantially no pores with diameters of less than 1 nm, which are difficult to measure by mercury intrusion porosimetry, or pores with diameters of more than 500 nm, which are difficult to measure by nitrogen adsorption. For this reason, the present invention employs a pore volume measured by nitrogen adsorption, which does not require the use of mercury, which requires careful handling. Specifically, the pore volume is determined by calculating the pore size distribution by the BJH method from the nitrogen adsorption isothermal adsorption curve.

[0035] The average pore diameter of the pores in the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) is not particularly limited, but is preferably 3 to 300 nm, more preferably 10 to 200 nm. Within this average pore diameter range, a porous organic-inorganic composite filler having the above-mentioned pore volume can be easily formed. Here, the average pore diameter of the pores in the organic-inorganic composite filler refers to the average pore diameter calculated from the pore volume obtained by calculating the pore size distribution using the BJH method from an isothermal adsorption curve determined by nitrogen adsorption, and the specific surface area calculated using the BET method.

[0036] When only the first organic / inorganic composite filler (X1) is blended into a dental curable composition, the composition is excellent in terms of the effect of reducing polymerization shrinkage and the abrasion resistance, aesthetics, and strength of the cured product. However, the composition may be sticky in a paste state before hardening, resulting in poor workability. Furthermore, when filling a molar Class I cavity, for example, the composition has the problem of poor ability to maintain the formed occlusal surface shape. The organic / inorganic composite filler of the present invention solves these problems related to paste properties by blending the second organic / inorganic composite filler (X2), which is an amorphous microporous organic / inorganic composite filler. From the viewpoint of a high paste property improvement effect, the second organic / inorganic composite filler (X2) in the organic / inorganic composite filler of the present invention preferably accounts for 5 to 90% by mass, particularly 10 to 85% by mass, expressed as the ratio of the mass of the second organic / inorganic composite filler (X2) to the total mass of the first organic / inorganic composite filler (X1) and the second organic / inorganic composite filler (X2).

[0037] As already explained, the particles constituting the organic-inorganic composite filler described in Patent Document 3 correspond to the first porous organic-inorganic composite particles (C1), and the cumulative pore volume of pores of 1 to 500 nm in the organic-inorganic composite filler measured by a nitrogen adsorption method is substantially 0.01 to 0.30 cm 3 / g. Therefore, the organic-inorganic composite filler described in Patent Document 3 corresponds to the first organic-inorganic composite filler (X1), and the organic-inorganic composite filler of the present invention can be suitably used as the first organic-inorganic composite filler (X1). In addition, the particles constituting the irregular microporous organic-inorganic composite filler proposed by the present inventors in Japanese Patent Application No. 2020-210301 (prior application) correspond to the second organic-inorganic composite particles (C2), and the cumulative pore volume of pores of 1 to 500 nm in the organic-inorganic composite filler measured by a nitrogen adsorption method is 0.01 to 0.30 cm 3 / g. Therefore, the irregular microporous organic-inorganic composite filler corresponds to the second organic-inorganic composite filler (X2), and the organic-inorganic composite filler of the present invention can be suitably used as the second organic-inorganic composite filler (X2).

[0038] Therefore, the manufacturing methods of the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) will be explained below based on the matters disclosed in Patent Document 3 and the matters described in the prior application.

[0039] 2. Method for producing the first organic-inorganic composite filler (X1) The first organic-inorganic composite filler (X1) can be suitably produced in accordance with the method described in Patent Document 3 by "a method comprising the steps of: immersing inorganic aggregated particles formed by aggregating primary particles of inorganic particles (B1) having an average primary particle diameter of 10 to 1500 nm in a polymerizable monomer solution containing 3 to 70 parts by mass of a polymerizable monomer (a1) and an effective amount of a polymerization initiator per 100 parts by mass of an organic solvent; removing the organic solvent from the immersed inorganic aggregated particles; and curing the polymerizable monomer impregnated in the inorganic aggregated particles by polymerization and curing."

[0040] The various raw materials used in the above method and each step will be described in detail below.

[0041] 2-1. Polymerizable monomers As the monomer (a1), any polymerizable monomer such as a radical polymerizable monomer or a cation polymerizable monomer used in conventional dental curable compositions can be used without any particular limitation. Among them, it is preferable to use a commonly used (meth)acrylate polymerizable monomer, specifically an acidic group-containing (meth)acrylate polymerizable monomer, a hydroxyl group-containing (meth)acrylate polymerizable monomer, or a monofunctional or polyfunctional (meth)acrylate polymerizable monomer not having these substituents.

[0042] Examples of suitable (meth)acrylate polymerizable monomers include the following: Namely, examples of acidic group-containing (meth)acrylate polymerizable monomers include (meth)acrylic acid, N-(meth)acryloyl-p-aminobenzoic acid, 2-(meth)acryloyloxybenzoic acid, 2-(meth)acryloyloxyethylphenylhydrogenphosphate, and 2-(meth)acryloyloxyethylphosphonic acid. Examples of hydroxyl group-containing (meth)acrylate polymerizable monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 2,2-bis[(3-methacryloyloxy-2-hydroxypropyloxy)phenyl]propane, 2,2-bis[4-(4-methacryloyloxy)-3-hydroxybutoxyphenyl]propane, 2,2-bis[4-(4-methacryloyloxy)-3-hydroxybutoxyphenyl]propane, and the like. Furthermore, examples of the monofunctional and polyfunctional (meth)acrylate polymerizable monomers not having the above-mentioned substituents include methyl (meth)acrylate, ethyl (meth)acrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,6-bis(methacrylethyloxycarbonylamino)trimethylhexane, and the like.

[0043] Among these polymerizable monomers, bifunctional or higher functional polymerizable monomers, more preferably bifunctional to tetrafunctional polymerizable monomers, are preferred because of their high polymerizability and the particularly high mechanical strength of the cured product, etc. These polymerizable monomers may be used alone or in combination.

[0044] When the organic-inorganic composite filler of the present invention is used as a filler for a dental curable composition, the monomer (a1) is preferably selected so that the difference between the refractive index of the cured product and the refractive index of the inorganic particles (B1) is 0.1 or less. By selecting such a polymerizable monomer, sufficient transparency can be imparted to the obtained organic-inorganic composite filler.

[0045] 2-2. Inorganic particles with an average primary particle size of 10 to 1500 nm The inorganic particles (B1) may have an average primary particle diameter of 10 to 1500 nm, preferably 10 to 1000 nm, more preferably 40 to 800 nm, and particularly preferably 50 to 600 nm. If the average primary particle diameter of the inorganic particles is less than 10 nm, it becomes difficult to form pores in the organic-inorganic composite particles. On the other hand, if the average primary particle diameter of the inorganic particles exceeds 1500 nm, when used in a dental curable composition, the polishability of the resulting cured product decreases, making it difficult to obtain a cured product with a smooth surface. Furthermore, the mechanical properties of the resulting cured product, such as bending strength, tend to decrease.

[0046] The shape of the primary particles of the inorganic particles is not particularly limited, and spherical, approximately spherical, or irregularly shaped particles can be used. From the viewpoints of excellent abrasion resistance, surface smoothness, and the ability to impart uniform pores to the organic-inorganic composite particles, spherical or approximately spherical shapes are preferred. Note that approximately spherical refers to particles with an average uniformity of 0.6 or more. The average uniformity is preferably 0.7 or more, and particularly preferably 0.8 or more. Here, the average primary particle diameter of inorganic particles refers to the number-average particle diameter determined by the following formula (average particle diameter calculation formula) based on the primary particle diameter (circle-equivalent diameter) X of n inorganic primary particles randomly selected from 30 or more particles, determined by image analysis using a scanning or transmission electron microscope and image analysis software capable of measuring at least the particle area, maximum length, and minimum width, where X for the i-th particle is Xi.

[0047]

number

[0048] Similarly, the average uniformity is a value determined for each of n inorganic primary particles by the following formula (average uniformity calculation formula), where (n) is the number of particles, (L) is the longest diameter of each particle, (B) is the shortest diameter of each particle, and (L) is the diameter in the direction perpendicular to the longest diameter of each particle, and (B) is the shortest width of each particle, and L and B of the i-th particle are Li and Bi, respectively.

[0049]

number

[0050] The material of the inorganic particles is not particularly limited, and any inorganic oxide used as a filler in conventional dental hardenable compositions can be used without particular limitation. Specifically, inorganic oxides such as amorphous silica, silica-zirconia, silica-titania, silica-titania-barium oxide, silica-titania-zirconia, quartz, alumina, titania, zirconia, and glass can be used. These inorganic oxide particles are preferably sintered at high temperatures to achieve a denser structure. A small amount of an oxide of a Group I metal of the periodic table, such as sodium, may be added to improve the densification effect achieved by high-temperature sintering. If necessary, known cation-eluting inorganic fillers for dental use, such as silicate glass and fluoroaluminosilicate glass, or metal fluorides, such as ytterbium trifluoride, may be added.

[0051] Among these inorganic oxide particles, silica-based composite oxide particles are particularly preferred because they allow for easy adjustment of the refractive index and have a large number of silanol groups on their surfaces, making them easy to modify with a silane coupling agent or the like. Furthermore, silica-zirconia, silica-titania, and silica-titania-barium oxide are preferred because they have strong X-ray contrast. Furthermore, silica-zirconia is most preferred because it can produce a cured product with superior abrasion resistance.

[0052] The inorganic particles (B1) can be suitably produced by, for example, a wet method, a dry method, a sol-gel method, etc. Among these, the sol-gel method is preferred because it is advantageous for industrially producing spherical, monodisperse fine particles, and it is also easy to adjust the refractive index and impart X-ray contrast properties. Methods for producing spherical composite inorganic oxide particles by the sol-gel method are known, for example, from JP-A-58-110414, JP-A-58-151321, JP-A-58-156524, and JP-A-58-156526.

[0053] 2-3. Soaking process In the immersion step, inorganic aggregated particles formed by aggregation of the primary particles of the inorganic particles (B1) are immersed in a polymerizable monomer solution containing 3 to 70 parts by mass of the monomer (a1) and an effective amount of a polymerization initiator per 100 parts by mass of an organic solvent. The polymerizable monomer solution may contain additives such as ultraviolet absorbers, pigments, dyes, polymerization inhibitors, and fluorescent agents to impart various functions to the organic-inorganic composite filler.

[0054] The inorganic agglomerated particles can be obtained by granulation using spray drying. Here, spray drying refers to a method in which a slurry of inorganic primary particles dispersed in a volatile liquid medium such as water is converted into fine atomized droplets using, for example, a high-speed airflow, and the atomized droplets are then contacted with a high-temperature gas to volatilize the liquid medium, thereby forming inorganic agglomerated particles by essentially concentrating the numerous inorganic primary particles dispersed within the droplets into a single agglomerated particle. The particle size and particle size distribution of the agglomerated particles are controlled depending on the spraying method and spraying conditions. The concentration of inorganic particles in the slurry is not limited as long as it can be atomized using a high-speed airflow or a disk-shaped rotor, but is generally 5 to 50% by mass. The rotation speed of the disk-shaped rotor is generally 1,000 to 50,000 rpm. Immediately drying the sprayed slurry using high-temperature air or an inert gas yields inorganic agglomerated particles with a uniform particle size. The temperature of the gas used for drying is generally 60 to 300°C. The inorganic agglomerated particles obtained by the above-mentioned spray drying may contain a small amount of the solvent used to prepare the slurry, and therefore, it is preferable to vacuum-dry the obtained inorganic agglomerated particles after spray drying.

[0055] The inorganic agglomerated particles thus obtained are then immersed in a polymerizable monomer solution containing 3 to 70 parts by mass, preferably 10 to 50 parts by mass, of a polymerizable monomer per 100 parts by mass of an organic solvent, and an effective amount of a polymerization initiator. As a result, the polymerizable monomer solution penetrates into the inorganic agglomerated particles through the agglomerated gaps of the inorganic agglomerated particles by capillary action. In this case, since the polymerizable monomer is diluted with the organic solvent, the liquid penetration by capillary action is high. As a result, the polymerizable monomer solution is filled deep into the agglomerated gaps. Note that, in order to improve wettability with the polymerizable monomer, the inorganic agglomerated particles or inorganic particles (B1) are preferably surface-treated with a hydrophobizing agent such as a silane coupling agent.

[0056] The polymerization initiator contained in the polymerizable monomer solution may be a photopolymerization initiator, a chemical polymerization initiator, or a thermal polymerization initiator. However, a thermal polymerization initiator is preferred because it can be used without constraints on the working environment, such as under light shielding or red light. Examples of thermal polymerization initiators that can be used include peroxides, azo compounds, boron compounds, and sulfinic acid salts. Azo compounds such as azobisisobutyronitrile are preferred because they are highly safe during operation and have little effect on the coloring of the organic-inorganic composite filler. The amount of polymerization initiator to be added should be an effective amount sufficient to promote polymerization, and is generally 0.01 to 30 parts by weight, preferably 0.1 to 5 parts by weight, per 100 parts by weight of the polymerizable monomer.

[0057] Examples of the organic solvent contained in the polymerizable monomer solution include halogenated organic solvents, hydrocarbon compounds, alcohol compounds, ether compounds, and ketone compounds, and methanol, ethanol, acetone, dichloromethane, etc. are preferably used.

[0058] An example of a method for infiltrating the polymerizable monomer solution into the inorganic agglomerated particles is a method of immersing the inorganic agglomerated particles in the polymerizable monomer solution. The immersion is preferably carried out at room temperature and normal pressure. The mixing ratio of the inorganic agglomerated particles and the polymerizable monomer solution is preferably 30 to 500 parts by mass, more preferably 50 to 200 parts by mass, of the polymerizable monomer solution per 100 parts by mass of the inorganic agglomerated particles. After mixing, if the mixture is allowed to stand, it is preferably left for 30 minutes or more, and more preferably for 1 hour or more. To promote the penetration of the polymerizable monomer solution into the gaps between the agglomerated particles, the mixture may be subjected to shaking and stirring, centrifugal stirring, pressurization, decompression, or heating.

[0059] 2-4. Organic solvent removal process and hardening process In the organic solvent removal step, the organic solvent is removed from the polymerizable monomer solution that has filled the agglomeration gaps. In removing the organic solvent, substantially all of the organic solvent (usually 95% by mass or more) that has infiltrated into the agglomeration gaps of the inorganic agglomerated particles is removed by heat drying, vacuum drying, vacuum freeze drying, or the like. Visually, removal should be continued until no coagulated particles sticking together are visible and a fluidized powder is obtained.

[0060] After removing the organic solvent, polymerization and curing are carried out according to the polymerization initiator used. When thermal polymerization is carried out, the polymerization temperature varies depending on the polymerization initiator used, so an optimal temperature may be selected as appropriate. Generally, the polymerization temperature is 30 to 170°C, preferably 50 to 150°C.

[0061] 3. Method for producing the second organic-inorganic composite filler (X2) The second organic-inorganic composite filler (X2) can be suitably produced by a method including the following slurrying step, drying step, hardening step, and pulverizing step.

[0062] (1) Slurrying step: A step of mixing inorganic particles (B2) having an average primary particle size of 10 to 1500 nm and a polymerizable monomer (a2) in the presence of an organic solvent so that the proportion of the mass of the inorganic particles to the total mass of the two is 80 to 95 mass %, to obtain a slurry in which components insoluble in the organic solvent are uniformly dispersed; (2) drying step: a step of removing the organic solvent from the slurry to obtain an agglomerate consisting of a mixture of the polymerizable monomer component (a2) and the inorganic particles (B2); (3) curing step: a step of polymerizing and curing the polymerizable monomer component (a2) contained in the aggregates to obtain a microporous aggregate comprising a composite of the organic resin component (A2) formed from a cured product of the polymerizable monomer (a2) and the inorganic particles (B2); (4) Pulverization step: pulverizing the aggregated microporous body powder The crushing process is embodied.

[0063] In the above method, the polymerizable monomer (a2) and inorganic particles (B2) can be the same as the polymerizable monomer (a1) and inorganic particles (B1). The organic solvent can be the same as that used in the immersion step 2-3. It is also preferable to incorporate an effective amount of the same polymerization initiator as that used in the immersion step 2-3 in the slurry step. Furthermore, additives such as ultraviolet absorbers, pigments, dyes, polymerization inhibitors, and fluorescent agents may be incorporated to impart various functions to the organic-inorganic composite filler.

[0064] In the above (1), the inorganic particles (B2), which have been surface-treated as necessary, and the polymerizable monomer (a2) are mixed in the presence of an organic solvent in a blending ratio such that the mass ratio of the inorganic particles (B2) to the total amount of both is 80 to 95 mass%, preferably 82 to 93 mass%, depending on the inorganic filling particle content of the target organic-inorganic composite filler, to obtain a slurry in which components insoluble in the organic solvent are uniformly dispersed.

[0065] When inorganic particles (B2) are surface-treated with a silane coupling agent by the spray drying method and then heated and dried at a temperature of 120°C or higher, they become roughly spherical agglomerated particles. However, by forming a uniform slurry from the surface-treated and heated particles in the presence of an organic solvent under appropriate conditions, the agglomerated particles are broken down, and the individual inorganic particles (B2) come into even contact with and are wetted by the polymerizable monomer (a2), resulting in a homogeneous agglomerated mass after the drying step. The amount of organic solvent used in the slurrying step may be any amount sufficient to obtain a homogeneous slurry. However, because a homogeneous slurry can be obtained and drying can be performed efficiently, the amount of organic solvent used in the slurrying step is preferably 20 to 500 parts by weight, particularly 30 to 100 parts by weight, per 100 parts by weight of the total mass of inorganic particles (B2) and polymerizable monomer (a2).

[0066] The mixing for forming a slurry may be carried out in one step or in multiple steps. However, because it is easy to obtain a uniform slurry, the inorganic particles (B2) and the polymerizable monomer component (a2) are mixed so that the proportion of the mass of the inorganic particles in the total mass of both is 80 to 95 mass %, and a wet slurry in which the polymerizable monomer component (a2) is attached to the surface of the inorganic particles (B2) is formed. powder It is preferable to carry out the process in two steps: a first step of obtaining a mixed powder consisting of the insoluble components; and a second step of mixing the mixed powder with an organic solvent to obtain a slurry in which the insoluble components are uniformly dispersed in the organic solvent.

[0067] In this case, it is preferable to use a mixer for the mixing in the first step from the viewpoint of uniformity. For example, a rocking mixer or a planetary mixer that mixes using a stirring blade can be used. Furthermore, as a mixing method in the second step, shaking stirring, ultrasonic stirring, or stirring and mixing using a kneader can be suitably used.

[0068] In the drying step (2), the organic solvent is removed from the slurry to obtain an agglomerate consisting of a mixture of the polymerizable monomer component (a2) and the inorganic particles (B2). In this drying step, the individual particles of the inorganic particles (B2) are interconnected using the polymerizable monomer component (a2) as a binder to form the agglomerate, and pores (open to the outside) are formed between the particles. The organic solvent is preferably removed until substantially all of the organic solvent (usually 95% by mass or more) is removed, resulting in a visually lumpy solid. The organic solvent removal method is not particularly limited as long as it is capable of achieving such removal. However, from the viewpoint of desired pore formation, reduced-pressure drying (or vacuum drying) is preferred, in which drying is performed under reduced pressure of 0.01 to 50 hectopascals, particularly 0.1 to 10 hectopascals.

[0069] The polymerization and curing in the curing step (3) may be carried out by selecting a suitable method depending on the type of polymerization initiator used. The polymerized and cured product (agglomerated microporous body) obtained by polymerization and curing is pulverized in the pulverization step (4) to produce the organic-inorganic composite filler of the present invention. Pulverization can be carried out using a vibrating ball mill, a bead mill, a jet mill, or the like. Furthermore, classification may be carried out using a sieve, an air classifier, or a water elutriation classifier, as necessary. As described above, the first organic-inorganic composite filler (X1) contains few first porous organic-inorganic composite particles (C1) with a particle diameter of 5 μm or less, and most of the particles with a particle diameter of 5 μm or less contained in the organic-inorganic composite filler of the present invention are second porous organic-inorganic composite particles (C2). Therefore, the amount of particles with a diameter of 5 μm or less contained in the organic-inorganic composite filler of the present invention is reduced depending on the content of the first organic-inorganic composite filler (X1), and the content can be made less than 15% by volume without any special classification.

[0070] 4. Dental hardenable composition of the present invention The dental curable composition of the present invention is a dental curable composition comprising 100 parts by mass of a polymerizable monomer, 200 to 600 parts by mass of a filler, and an effective amount of a polymerization initiator, wherein 30% by mass or more of the filler is the organic-inorganic composite filler of the present invention.

[0071] If the filler content is outside the above range, the strength of the cured product will be low, and if the organic-inorganic composite filler of the present invention accounts for less than the above lower limit, at least one of the effects of reducing polymerization shrinkage, improving strength, and improving paste properties will not be obtained. From the viewpoint of these effects, the filler content per 100 parts by mass of polymerizable monomer is preferably 100 to 800 parts by mass, particularly 200 to 600 parts by mass.

[0072] As the polymerizable monomer, any polymerizable monomer used for the intended purpose can be used without any limitations. Usually, the same polymerizable monomer as that used in producing the organic-inorganic composite filler of the present invention can be used. However, it is not necessary to use the same polymerizable monomer as that actually used in the organic-inorganic composite filler of the present invention, and it may be different.

[0073] Polymerization initiators used for the intended application can be used without limitation. Generally, photopolymerization is often adopted as a means for curing (polymerizing) dental curable compositions due to its ease of use. For the above reasons, it is preferable to use a photopolymerization initiator as the polymerization initiator in the dental curable composition of the present invention. Preferred photopolymerization initiators include, for example, benzoin alkyl ethers, benzil ketals, benzophenones, α-diketones, thioxanthone compounds, and bisacylphosphine oxides. A reducing agent is often added to the photopolymerization initiator. Examples of reducing agents include aromatic amines, aliphatic amines, aldehydes, and sulfur-containing compounds. Furthermore, trihalomethyltriazine compounds, aryliodonium salts, and the like can also be added as needed. The polymerization initiator is generally blended in an amount of 0.01 to 10 parts by mass per 100 parts by mass of the polymerizable monomer.

[0074] The filler may contain other fillers, such as inorganic fillers or other organic-inorganic composite fillers, as long as the content of the organic-inorganic composite filler of the present invention is 30% by mass or more. From the viewpoints of the aesthetic quality of the cured product and the effect of reducing polymerization shrinkage, it is preferable that the main portion of the other fillers be inorganic particles having an average primary particle diameter of 10 to 1,500 nm. The inorganic particles can be the same as those described in (B1) and (B2) above. However, it is not necessary to use the same inorganic particles as those actually used in the organic-inorganic composite filler of the present invention; they can be different. Note that the main portion means that the other filler accounts for 90% by mass or more, preferably 95% by mass or more, of the other filler. It can also contain amorphous fine fillers, etc., blended as trace components for the purpose of imparting thixotropy to the paste or for thickening it.

[0075] Furthermore, the dental curable composition of the present invention may contain known additives, such as polymerization inhibitors, pigments, ultraviolet absorbers, and fluorescent agents, within the range that does not significantly impair the effects of the composition. [Example]

[0076] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0077] 1. Raw materials and their abbreviations The various raw materials used in the examples and comparative examples and their abbreviations are listed below.

[0078] (1) Polymerizable monomer 3G: Triethylene glycol dimethacrylate GMA: 2,2-bis[(3-methacryloyloxy-2-hydroxypropyloxy)phenyl]propane UDMA: 1,6-bis(methacrylethyloxycarbonylamino)-2,2-4-trimethylhexane · HD: 1,6-hexanediol dimethacrylate.

[0079] (2) Inorganic particles (inorganic fillers) F-1: Spherical silica-zirconia particles produced by the sol-gel method (average particle size of primary particles: 200 nm, average uniformity of primary particles: 0.95) F-2: Spherical silica-zirconia particles manufactured by the sol-gel method (average particle size of primary particles: 400 nm, average uniformity of primary particles: 0.95) F-3: Silica-titania particles produced by the sol-gel method (average particle size of primary particles: 70 nm, average uniformity of primary particles: 0.95) F-4: Irregular silica-zirconia particles produced by the sol-gel method (average particle size of primary particles: 1000 nm) F-5: Spherical ytterbium trifluoride particles (average primary particle size: 50 nm) The average particle size of primary particles refers to the number-average particle size calculated from the average particle size calculation formula based on the primary particle diameter (circle-equivalent diameter) X obtained by taking a photograph of powder at 5,000 to 100,000 times magnification using a scanning electron microscope (Philips, "XL-30S"), processing the photographed image using image analysis software ("IP-1000PC", product name; Asahi Kasei Engineering Corporation) and counting the number of particles (30 or more) observed within a unit field of view of the photograph. The average uniformity refers to a value calculated from the maximum diameter of each particle, the major axis (L) and the minor axis (B), using the average uniformity calculation formula.

[0080] (3) Polymerization initiator AIBN: Azobisisobutyronitrile CQ: Camphorquinone ·DMBE: Ethyl N,N-dimethyl-p-benzoate.

[0081] 2. Evaluation method for organic-inorganic composite fillers (1) Method for measuring the average particle size of organic-inorganic composite fillers 0.1 g of organic-inorganic composite filler was dispersed in 10 ml of ethanol and irradiated with ultrasound for 20 minutes. The median diameter of the volume statistics was determined using a particle size distribution analyzer (LS230, Beckman Coulter) based on the laser diffraction-scattering method and the optical model "Fraunhofer."

[0082] Furthermore, from the particle size distribution obtained when measuring the average particle diameter (particle size), the volumetric abundance ratio (fine particle abundance ratio) was determined for the range of 0.04 μm to 5.0 μm.

[0083] (2) Method for measuring pore volume and average pore diameter of organic-inorganic composite filler 0.1 g of organic-inorganic composite filler was placed in a sample cell, and pretreatment was performed by evacuation at 120°C for 3 hours using a pretreatment device ("VacuPrep 061" manufactured by Shimadzu Corporation). Nitrogen adsorption isotherms were then measured using a gas adsorption pore size distribution analyzer ("TriStar II3020" manufactured by Shimadzu Corporation) with nitrogen as the adsorption gas and liquid nitrogen as the refrigerant. The cumulative pore volume in the pore diameter range of 1 to 500 nm was then calculated using the BJH method. The average pore diameter was calculated from the pore volume and the specific surface area calculated by the BET method.

[0084] 3. Production Examples of the First Organic-Inorganic Composite Filler (X1) (Production Examples 1 to 4) Manufacturing Example 1 100 g of inorganic filler F-1 was added to 200 g of water, and a dispersion of the inorganic filler was obtained using a circulation mill, SC Mill. Next, γ-methacryloyloxypropyltrimethoxysilane and acetic acid were added to water and stirred to obtain a homogeneous solution with a pH of 4. This solution was added to the inorganic particle dispersion and mixed uniformly. The dispersion was then mixed while colliding with atomizing air at the nozzle tip of a spray dryer (Spray Dryer "NL-5", manufactured by Okawahara Chemical Engineering Co., Ltd.) to form fine particles. The spray pressure was 0.08 MPa, the drying temperature was 230 °C, and the mixture was spray-dried. The spray-dried inorganic powder was then vacuum-dried at 120 °C for 18 hours to obtain inorganic agglomerated particles. Next, 80 g of the inorganic agglomerated particles were immersed in a polymerizable monomer solution prepared by mixing 12.0 g of GMA as polymerizable monomers, 8.0 g of 3G, 0.08 g of AIBN as a polymerization initiator, and 80 g of ethanol as an organic solvent. After thorough stirring, the mixture was allowed to stand for 1 hour after confirming that it had become a slurry.

[0085] The mixture was dried in a rotary evaporator under reduced pressure of 10 hectopascals and heated to 40°C (using a hot water bath) for 1 hour while stirring to remove the organic solvent. After the organic solvent was removed, a smooth powder was obtained. The powder was stirred in a rotary evaporator and heated for 2 hours under conditions of a vacuum of 10 hectopascals and heating conditions of 100°C (using an oil bath), to polymerize and harden the polymerizable monomer in the powder. The resulting organic-inorganic composite filler was approximately spherical, with an average particle size of 20 μm, and no particles of 5 μm or less were observed in the particle size distribution. The cumulative pore volume in the 1-500 nm range determined by nitrogen adsorption was 0.04 cm. 2 / g, and the average pore diameter was 48 nm. As shown in Figure 2, it was confirmed that this corresponds to the X1) filler having a curved surface.

[0086] Production Examples 2 and 4 The organic-inorganic composite fillers were obtained in the same manner as in Production Example 1, except that the types of polymerizable monomer components to be blended into the organic-inorganic composite fillers and the blending amounts of the inorganic filler and polymerizable monomer component were changed as shown in Table 1, and the physical properties of each of the organic-inorganic composite fillers were evaluated in the same manner as in Production Example 1. The results are also shown in Table 1.

[0087] Manufacturing Example 3 100 g of inorganic filler F-1 was added to 200 g of water, and a dispersion of the inorganic filler was obtained using a circulation mill, SC Mill. Next, γ-methacryloyloxypropyltrimethoxysilane and acetic acid were added to water and stirred to obtain a homogeneous solution with a pH of 4. This solution was added to the inorganic particle dispersion and mixed uniformly. The dispersion was then fed onto a rotating disk at high speed while being mixed, and dried by spray drying. The spray dryer used was a spray dryer equipped with a rotating disk and atomized by centrifugal force (Spray Dryer "TSR-2W", manufactured by Sakamoto Giken Co., Ltd.). The disk rotation speed was 10,000 rpm, and the spray drying temperature was 200°C. The spray-dried inorganic powder was then vacuum-dried at 120°C for 18 hours to obtain inorganic agglomerated particles. Next, 85 g of the inorganic agglomerated particles were immersed in a polymerizable monomer solution prepared by mixing 9.0 g of GMA and 6.0 g of 3G as polymerizable monomers, 0.06 g of AIBN as a polymerization initiator, and 80 g of ethanol as an organic solvent. After thorough stirring, the mixture was allowed to stand for 1 hour after confirming that it had become a slurry.

[0088] The mixture was dried in a rotary evaporator under reduced pressure of 10 hectopascals and heated to 40°C (using a hot water bath) for 1 hour while stirring to remove the organic solvent. After the organic solvent was removed, a smooth powder was obtained. The powder was heated for 2 hours under conditions of a vacuum of 10 hectopascals and heating conditions of 100°C (using an oil bath) while stirring in a rotary evaporator, to polymerize and harden the polymerizable monomer in the powder. The obtained organic-inorganic composite filler was approximately spherical, with an average particle diameter of 50 μm, and no particles of 5 μm or less were observed in the particle size distribution. The cumulative pore volume in the 1-500 nm range determined by nitrogen adsorption was 0.10 cm. 2 / g, and the average pore diameter was 50 nm.

[0089] 4. Production Examples of the Second Organic-Inorganic Composite Filler (X2) (Production Examples 5 to 13) Manufacturing Example 5 Slurrying process: Surface treatment of inorganic particles: 100 g of inorganic filler F-1 was added to 200 g of water, and a dispersion of the inorganic filler was obtained using a circulation mill, SC Mill. Next, γ-methacryloyloxypropyltrimethoxysilane and acetic acid were added to water and stirred to obtain a homogeneous solution with a pH of 4. This solution was added to the inorganic particle dispersion and mixed uniformly. The dispersion was then fed onto a rotating disk at high speed while mixing, and dried by spray drying. Spray drying was performed using a spray dryer equipped with a rotating disk and atomizing by centrifugal force (Spray Dryer "TSR-2W", manufactured by Sakamoto Giken Co., Ltd.), with a disk rotation speed of 10,000 rpm and a spray drying temperature of 200°C. The spray-dried inorganic powder was then vacuum-dried at 80°C for 18 hours. First step: To 90 g of the obtained powder (inorganic agglomerated particles), a polymerizable monomer mixture prepared in advance by mixing 6.0 g of GMA and 4.0 g of 3G as polymerizable monomers and 0.04 g of AIBN as a polymerization initiator was added, and the mixture was mixed for 30 minutes using a planetary mixer (manufactured by Inoue Seisakusho) with the stirring blade rotation speed of 7 to 10 rpm to obtain a mixed powder. Second step: 40 g of ethanol was added as an organic solvent to the above mixed powder, and further mixed to obtain a uniform slurry with high fluidity.

[0090] Drying, curing and grinding processes: The slurry was vacuum dried at 25°C using a vacuum dryer, and after ethanol was distilled off, it was heated at 100°C for 2 hours using a vacuum dryer to polymerize and harden the polymerizable monomer, yielding a cake-like white solid. This hardened product was then pulverized in a vibration ball mill (zirconia ball diameter: 5 mm) for 30 minutes, and the pulverized product was sieved to remove particles larger than 100 μm.

[0091] The average particle size of the obtained crushed organic-inorganic composite filler was 37 μm, the volumetric proportion of particles of 5 μm or less in the particle size distribution was 13.5%, and the cumulative pore volume in the 1 to 500 nm range determined by the nitrogen adsorption method was 0.15 cm 2 The average pore size was 62 nm. The shape of each particle constituting the obtained organic-inorganic composite filler was confirmed by scanning electron microscopy. 2 As shown in Fig. 1, it was confirmed that the particles were of irregular shape (X2) filler, which does not have a curved surface and has adjacent surfaces with angles.

[0092] Preparation Examples 6 to 10, 12 and 14 The organic-inorganic composite fillers were obtained in the same manner as in Production Example 5, except that the type of inorganic filler blended in the organic-inorganic composite filler, the type of polymerizable monomer component, and the blending amounts of the inorganic filler and polymerizable monomer component were changed as shown in Table 1, and the physical properties of each were measured in the same manner as in Production Example 5. The results are also shown in Table 1.

[0093] Manufacturing Example 11 76 g of inorganic agglomerated particles F-1 surface-treated with γ-methacryloyloxypropyltrimethoxysilane obtained in the same manner as in Production Example 5 and 19 g of inorganic filler F-5 were added to a polymerizable monomer mixture prepared in advance by mixing 3.0 g of GMA and 2.0 g of 3G as polymerizable monomers, and 0.02 g of AIBN as a polymerization initiator, and the mixture was mixed for 30 minutes using a planetary mixer (manufactured by Inoue Seisakusho) with the stirring blade rotation speed of 7 to 10 rpm to obtain a mixed powder.

[0094] To the above mixed powder, 40 g of ethanol was added as an organic solvent, and the mixture was further mixed to obtain a homogeneous slurry with high fluidity. The above slurry was vacuum dried at 25°C using a vacuum dryer, and after the ethanol was distilled off, it was heated at 100°C for 2 hours using a vacuum dryer to polymerize and harden the polymerizable monomer, thereby obtaining a cake-like white solid. Next, this cured product was pulverized in a vibration ball mill (zirconia ball diameter: 5 mm) for 30 minutes, and the pulverized product was sieved to remove particles of 100 μm or larger. The average particle size of the resulting crushed organic-inorganic composite filler was 35 μm, and the volumetric proportion of particles of 5 μm or smaller in the particle size distribution was 9.0%. The cumulative pore volume in the 1-500 nm range determined by nitrogen adsorption was 0.09 cm. 2 / g, and the average pore diameter was 35 nm.

[0095] Manufacturing Example 13 A cake-like white solid was obtained in the same manner as in Production Example 5, with the type of inorganic filler to be blended in the organic-inorganic composite filler, the type of polymerizable monomer component, and the blending amounts of the inorganic filler and polymerizable monomer component, as well as the slurrying step, drying step, and curing step in the production process. Next, this cured product was pulverized in a vibration ball mill (zirconia ball diameter: 5 mm) for 120 minutes, and the pulverized product was passed through a sieve with 100 μm openings to remove particles of 100 μm or larger. The physical properties of the obtained crushed organic-inorganic composite filler were measured in the same manner as in Production Example 5. The results were that the average particle size was 37 μm, the proportion of particles of 5 μm or smaller in the particle size distribution on a volume basis was 20.2%, and the cumulative pore volume was 0.09 cm. 2 / g and the average pore diameter was 37 nm.

[0096] 5. Other manufacturing examples of organic-inorganic composite fillers (comparative manufacturing examples) Comparative manufacturing example To 75 g of the inorganic agglomerated particles of F-1, surface-treated with the same γ-methacryloyloxypropyltrimethoxysilane as in Production Example 5, 15.0 g of GMA as polymerizable monomers, 10.0 g of 3G, and 0.10 g of AIBN as a polymerization initiator were added a polymerizable monomer mixture prepared in advance. The mixture was mixed for 30 minutes using a planetary mixer (manufactured by Inoue Seisakusho) at a stirring blade rotation speed of 7 to 10 rpm to prepare a paste-like mixture. This paste-like mixture was degassed under reduced pressure and then polymerized and cured at 100°C for 2 hours. The cured product was pulverized in a vibration ball mill (zirconia ball diameter: 5 mm) for 30 minutes, and particles larger than 100 μm were removed by sieving. The resulting organic-inorganic composite filler was amorphous, had an average particle size of 45 μm, and no pores were observed when measured by nitrogen adsorption.

[0097] [Table 1]

[0098] 6. Examples and Comparative Examples Examples 1 to 12 and Comparative Examples 1 to 4 Using each organic-inorganic composite filler shown in Table 1, those corresponding to the organic-inorganic composite filler composition of the present invention were prepared as Examples, and those not corresponding to the same were prepared as Comparative Examples.

[0099] For the organic-inorganic composite filler composition used in the examples, X1 filler and X2 filler were mixed in advance in the blending ratio shown in Table 2, and the proportion of particles of 5 μm or less in the particle size distribution was determined in the same manner as in Production Example 1.

[0100] Using these organic-inorganic composite filler compositions, dental curable compositions of each example were prepared as follows. That is, 0.20 parts by mass of CQ and 0.35 parts by mass of DMBE were completely dissolved as a polymerization initiator in a polymerizable monomer consisting of 60 parts by mass of GMA and 40 parts by mass of 3G. The resulting solution was then mixed in a mortar with inorganic filler F-1 and each organic-inorganic composite filler in the proportions shown in Table 2 until uniform, and the mixture was degassed to prepare a paste-like dental curable composition of each example.

[0101] The dental curable compositions thus obtained were evaluated for their workability in a paste state, shape retention, and bending strength in a cured form by the methods described below. The results are shown in Table 3.

[0102] (1) Evaluation of the operability of dental hardenable compositions in a paste state The paste properties of the dental curable compositions before hardening were evaluated based on the following criteria from the viewpoint of ease of handling. A rating of ○ was given for those with little stickiness, ◎ for those with particularly little stickiness, and × for those with paste properties that were very sticky and difficult to handle. Furthermore, a rating of ○ was given for those with little roughness, ◎ for those with particularly little stickiness, and × for those with paste properties that were very sticky and difficult to handle. The evaluation was carried out immediately after the dental curable compositions were prepared and after they had been stored at 37°C for 6 months.

[0103] (2) Evaluation of paste shape retention The shape retention of the dental hardenable composition paste before hardening was evaluated using the following method. A hard resin tooth with a Class I cavity (4 mm in diameter, 2 mm in depth) reproduced in the center of the occlusal surface of the lower right tooth, tooth number 6, was filled with the hardenable composition, and the occlusal surface shape was imparted to the filled paste. The hard resin tooth filled with the dental hardenable composition was then placed in an incubator at 50°C for 20 minutes, and evaluation was performed to determine whether the imparted shape was maintained. A slight change in the imparted shape was evaluated as ○, no change at all was evaluated as ◎, and the shape was not maintained as ×. Evaluations were performed immediately after the dental hardenable composition was prepared and after storage at 37°C for 6 months.

[0104] (3) Bending strength evaluation The dental curable composition paste was filled into a stainless steel mold using a filler, and in this state, the mold was pressed with polypropylene and exposed to a visible light irradiator, Power Light (manufactured by Tokuyama Dental Corporation; light output density 700 mW / cm). 2 The specimen was then irradiated three times for 30 seconds from one side using a 1500mm waterproof abrasive paper, with the specimen adhered to polypropylene in different locations so that the entire specimen was exposed to light. The specimen was then irradiated three times for 30 seconds from the other side, with the specimen adhered to polypropylene, to obtain a cured specimen. The cured specimen was then trimmed into a 2 x 2 x 25 mm rectangular column using #1500 waterproof abrasive paper. This specimen was then mounted on a Shimadzu Autograph AG5000D testing machine, and the three-point bending fracture strength was measured at a support distance of 20 mm and a crosshead speed of 1 mm / min. Five specimens were evaluated, and the average value was taken as the bending strength. A load-deflection curve was obtained.

[0105] Formula: σ B =(3PS) / (2WB 2 ) The bending strength was calculated. The symbols above are, respectively, σ B : Bending strength (Pa), P: Load at fracture of specimen (N), S: Distance between supports (m), W: Width of specimen (m), B: Thickness of specimen (m).

[0106] (4) Shrinkage rate A 7 mm thick stainless steel (SUS) split mold with a through hole of 3 mm diameter was formed, and a SUS plunger of just under 3 mm diameter and 4 mm height was inserted with some looseness into the mold to close one opening of the through hole and adjust the depth of the hole to 3 mm. Next, the dental hardenable composition was filled into the hole, and then the upper end of the hole was pressed with a polypropylene film. Next, a visible light irradiator, Power Light (manufactured by Tokuyama Dental Corporation; light output density 700 mW / cm), was placed under the center of the glass top plate of the glass stand. 2 ) was installed. The SUS split mold was placed on the center of the glass top plate of this glass stand, with the side with the polypropylene film facing downwards. A probe capable of measuring minute needle movements was then brought into contact with the top surface of the SUS plunger. In this state, the dental hardenable composition was polymerized and hardened using a visible light irradiator, and the shrinkage rate (%) 3 minutes after the start of irradiation was calculated from the vertical movement distance of the probe.

[0107] [Table 2]

[0108] [Table 3]

[0109] As can be seen from the results of Examples 1 to 12, dental curable compositions containing the organic-inorganic composite filler composition of the present invention exhibit high bending strength in the cured form, are less sticky and rough in the paste state, and exhibit good shape retention. Furthermore, there is very little change in operability and shape retention due to long-term storage. Furthermore, there is very little shrinkage during polymerization.

[0110] As can be seen from the results of Comparative Example 1, the dental curable composition containing only the porous curved organic-inorganic composite filler (X1) as the organic-inorganic composite filler was very sticky in a paste state, and had a large change in operability and shape retention over long-term storage.In addition, the shrinkage rate during polymerization was large.

[0111] As can be seen from the results of Comparative Example 2, the dental curable composition containing only the porous amorphous organic-inorganic composite filler (X2) having a high proportion of fine particles as the organic-inorganic composite filler was less sticky in a paste state, but was more rough and had a large shrinkage rate during polymerization.

[0112] As can be seen from the results of Comparative Examples 3 and 4, dental curable compositions containing non-porous (non-porous) crushed organic-inorganic composite fillers are less sticky in a paste state and have relatively good shape retention, but after long-term storage, they become too dry and difficult to use. In addition, the bending strength of the cured product is low.

Claims

1. a first porous organic-inorganic composite particle (C1) comprising a composite of an organic resin component (A1) made of a cured product of a polymerizable monomer (a1) and inorganic particles (B1) having an average primary particle diameter of 10 to 1,500 nm, at least a portion of whose surfaces are curved, and an integrated pore volume of pores with a diameter of 1 to 500 nm measured by a nitrogen adsorption method of 0.01 to 0.30 cm ３ / g of a first organic-inorganic composite filler (X1); and The present invention is directed to a method for producing a cured product of a polymerizable monomer (a2) comprising a composite of an organic resin component (A2) and inorganic particles (B2) having an average primary particle diameter of 10 to 1,500 nm, and comprising second porous organic-inorganic composite particles (C2) that do not have a curved shape, the cumulative pore volume of pores with a diameter of 1 to 500 nm being 0.01 to 0.30 cm as measured by a nitrogen adsorption method. ３ / g, and a second organic-inorganic composite filler (X2) having an irregular shape with no curved surface and adjacent faces having an angle; The first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2) both have an average particle size of 5 to 100 μm, and the content of particles having a particle diameter of 5 μm or less in the first porous organic-inorganic composite particles (C1) and the second porous organic-inorganic composite particles (C2) is less than 15% by volume; An organic-inorganic composite filler characterized by:

2. The organic-inorganic composite filler according to claim 1, wherein the second organic-inorganic composite filler (X2) is 10 to 85 mass% relative to the total mass of the first organic-inorganic composite filler (X1) and the second organic-inorganic composite filler (X2).

3. the average content of the inorganic particles (B1) in the first porous organic-inorganic composite particles (C1) is 75 to 90 mass %, The organic-inorganic composite filler according to claim 1 or 2, wherein the average content of the inorganic particles (B2) in the second porous organic-inorganic composite particles (C2) is 80 to 95 mass%.

4. The organic-inorganic composite filler according to claim 1, wherein the inorganic particles (B1) and / or (B2) contain inorganic particles having X-ray contrast properties.

5. 1. A dental curable composition comprising 100 parts by mass of a polymerizable monomer, 200 to 600 parts by mass of a filler, and an effective amount of a polymerization initiator, wherein 30% by mass or more of the filler is the organic-inorganic composite filler according to claim 1.

6. 6. The dental curable composition according to claim 5, wherein 30 to 70 mass% of the filler is the organic-inorganic composite filler according to claim 1, and the remainder of the filler is mainly inorganic particles having an average primary particle size of 10 to 1,500 nm.

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