Hybrid resin blank for dental cutting and method for producing crown

Abstract

The present invention provides a hybrid resin-based blank for dental cutting having a part to be cut that has a single layer structure or a laminated structure including a layer that comprises a colorant-added structural color-based hybrid resin in which one or a plurality of types of colorants are dispersed in a resin matrix of a structural color-based hybrid resin in which inorganic particles are dispersed in the resin matrix and that expresses a structural color with a prescribed color tone, the hybrid resin-based blank for dental cutting containing 800-8000 mass ppm of the colorants relative to the total mass of the colorant-added structural color-based hybrid resin, and the proportion of the colorant, among the colorants, that have a color similar to the structural color being 70 mass% or above. The present invention also provides a method for manufacturing a crown in which the hybrid resin-based blank for dental cutting is used.

Description

[Technical Field]

[0001] The present disclosure relates to a hybrid resin-based blank for dental machining and a method for producing a crown using the same. [Background technology]

[0002] In dental treatment, the fabrication of dental restorations (dental prostheses) such as inlays, onlays, crowns, bridges, and implant superstructures has become commonplace. Computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, which utilize intraoral imaging to machine dental blanks made of nonmetallic materials, are increasingly used. Here, a dental blank refers to a workpiece (also known as a "mill blank") that can be attached to a milling machine in a CAD / CAM system. Common examples include solid blocks shaped like rectangular parallelepipeds or cylinders; solid disks shaped like plates or boards; and so on. Dental blanks often have retaining pins attached to them to secure them to the milling machine. In this specification, the term "dental blank" refers to a blank that includes a retaining pin. The body of the object to be cut (dental cutting blank body) is sometimes referred to as the part to be cut.

[0003] As a blank for dental cutting, hybrid resin blanks for dental cutting (hereinafter also referred to as "HR blanks") having a block-shaped part to be cut are often used, which are made of a resin material (also called "hybrid resin" (HR)) consisting of a hardened product of a hardenable composition containing an inorganic filler such as silica, a polymerizable monomer such as a methacrylate compound, and a polymerization initiator, in view of their high workability (cutting processability), high aesthetics, strength, etc.

[0004] To achieve a highly aesthetic restoration, it is necessary to determine the color (defined by hue, lightness, and saturation, i.e., hue and tone) of the tooth to be restored (the tooth to be restored) or the surrounding teeth, and then select an HR blank with a cut-machined portion of a color that matches the determined color. This type of color determination is sometimes referred to as "shade taking." Shade taking is typically performed using a tooth color sample called a shade guide. There are various shade guides, each with a different number of color samples and a different configuration for the holding device. Among these, the "VITA Classical" (product name), a shade guide manufactured by VITA (hereinafter also referred to as the "VITA Shade Guide"), is the most widely used (see, for example, Patent Document 1). The VITA Shade Guide consists of 16 color samples (hereinafter, a color identified by an index that combines a hue with a blended index of lightness and saturation, or an index that takes hue, lightness, and saturation into account, is also referred to as a "shade"). The color of the restoration can be determined by comparing the shade guide with the color of the restoration and the surrounding teeth. The VITA Shade Guide classifies colors into group A (reddish-brown), group B (reddish-yellow), group C (gray), and group D (reddish-gray) by lightness and represents them with symbols. The 16 shades are arranged in descending order of lightness as follows: B1 → A1 → B2 → D2 → A2 → C1 → C2 → D4 → A3 → D3 → B3 → A3.5 → B4 → C3 → A4 → C4.

[0005] HR blanks include those with a single color in which the machinable portion is composed of a single HR layer, and those with multiple HR layers of different colors (see, for example, Patent Document 2), and both are often available in a variety of basic shades, either of the 16 shades mentioned above or several selected from among them (as many as the number of basic shades). That is, in the surface color pattern of the machinable portion of an HR blank, in a single-layer HR blank, the entire surface is composed of one specific basic shade (color), while in a laminated HR blank, one of the layers constituting the laminate has a specific basic shade, and the other layers have a shade other than the basic shade and / or a color other than the 16 shades, resulting in a surface that is color-coded with multiple different colors according to the layer structure.

[0006] In addition, some single-layer HR blanks are known to exhibit so-called structural colors, which allow them to harmonize in color with natural teeth without using pigments or the like (hereinafter referred to as "structural color HR blanks"). For example, Patent Document 3 discloses "a resin-based block for dental cutting processing, which contains a resin matrix (A) and spherical fillers (B) having an average particle size in the range of 230 nm to 1000 nm, characterized in that, when measured at a thickness of 10 mm using a color difference meter, the colorimetric values of the Munsell color system for colored light against a black background and against a white background have a lightness (V) of less than 5.0 and a saturation (C) of less than 2.0, and when measured at a thickness of 1 mm using a color difference meter, the colorimetric values of the Munsell color system for colored light against a black background have a lightness (V) of less than 5.0 and a saturation (C) of 0.05 or more, and the colorimetric values of the Munsell color system for colored light against a white background have a lightness (V) of 6.0 or more and a saturation (C) of less than 2.0."

[0007] And in Patent Document 3, 90% or more of the individual particles constituting the spherical filler (B) are present within the range of ±5% of the average particle diameter. When the refractive index of the resin matrix (A) at 25°C is nP and the refractive index of the spherical filler (B) at 25°C is nF, by satisfying the condition of nP < nF, depending on the particle diameter of the spherical filler (B), colored light of a specific color tone is expressed as a structural color, and under a black background, it is clearly confirmed as a unique reflection spectrum corresponding to the colored light. However, under a white background, it shows a substantially uniform reflectance over a substantially entire range of the visible spectrum, and the light in the visible spectrum is not confirmed. In particular, those that exhibit (express) a structural color in the yellow to red color system are described as having an effect of widely harmonizing with various surrounding environments.

[0008] In addition, in the HR that exhibits a structural color used as the machined part of the structural color system HR blank (hereinafter, also referred to as "structural color system HR"), regarding the composite material (corresponding to the structural color system HR) in which inorganic particles are dispersed in the resin matrix, when the shape and particle size distribution of the inorganic particles, the relationship between the refractive index of the inorganic particles and the refractive index of the resin matrix, and the dispersion state of the inorganic particles satisfy specific conditions, it is known that a structural color of a certain color tone (hereinafter, also referred to as "specific structural color") that is not affected by the change in the incident angle of light is developed (for example, see Patent Document 4).

[0009] In addition, among the structural colors used in the dental field, in addition to the above specific structural color, there is what is known as the so-called opal effect (for example, see Patent Document 5), and an HR blank using HR obtained by blending a colorant into HR that exhibits the opal effect and adjusting the color to a specific shade is also known.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

[0011] In the case of HR blanks that have been tinted to a specific shade using a colorant, dental restorations are generally produced using HR blanks of a color (shade) selected by shade taking based on the appearance color of the HR blank before cutting.

[0012] However, when a crown, which is a dental prosthesis that covers an abutment tooth, is produced using such an HR blank that has been tinted to a specific shade using a coloring agent, the external color (shade) changes, and as a result, when the produced crown is actually attached to the patient's abutment tooth (a tooth that has been cut and shaped to fit the crown), the desired color harmony may not be achieved.

[0013] On the other hand, Patent Document 3 states that restorations that match the color of natural teeth are possible by using dental prostheses made from structural color HR blanks. However, the evaluation of color harmony in Patent Document 3 was performed on a dental prosthesis (inlay) that fit into a Class II cavity (diameter 5 mm, depth 3 mm) created in an artificial tooth for the lower right sixth molar (first molar), and color harmony for crowns was not confirmed. The inventors suspected that the above-mentioned problems might also occur with crowns made using structural color HR blanks, so they investigated the color compatibility of crowns made using structural color HR blanks and found that similar problems occurred.

[0014] Therefore, the first objective of the present disclosure is to suppress the change in shade that occurs when a crown is fabricated using an HR blank that has been colored to a specific shade with a colorant.The second objective of the present disclosure is to provide an HR blank that exhibits a specific structural color, as disclosed in Patent Document 3, that maintains excellent color harmony when an inlay is fabricated, and can achieve good color harmony when worn even when a crown is fabricated. [Means for solving the problem]

[0015] The hybrid resin blank (HR blank) for dental cutting processing, which is a first aspect of the present disclosure, is a hybrid resin blank (HR blank) for dental cutting processing, which has a cutting part of a single layer structure or a laminate structure including a layer made of a colorant-blended structural color hybrid resin (colorant-blended structural color HR) in which one or more colorants are further dispersed in the resin matrix of a structural color hybrid resin (structural color HR) in which inorganic particles are dispersed in a resin matrix and which exhibits a structural color of a predetermined color tone. The horizontal axis represents the wavelength of reflected light (nm) obtained by measuring a 3 mm thick sample made of structural color HR without any colorant blended therein using a color difference meter against a black background. ), and in a spectral reflectance curve with the vertical axis representing reflectance (%), the wavelength that provides the maximum reflectance due to the structural color is defined as the structural color wavelength, and the wavelength region showing a reflectance of 85% or more of the maximum reflectance is defined as A. The wavelength that provides the maximum reflectance in the spectral reflectance curve obtained by measuring the colorant with a colorimeter against a black background is defined as the color-developing wavelength of the colorant, and colorants whose color-developing wavelengths fall within wavelength region A are defined as same-color colorants, and colorants whose color-developing wavelengths fall outside wavelength region A are defined as different-color colorants. The structural color system HR contains 800 to 8,000 ppm by mass of the colorant based on the total mass of the colorant-blended structural color system, and the proportion of same-color colorants in the colorant is 70% by mass or more.

[0016] The HR blank of the present disclosure preferably has a structural color wavelength in the range of 590 to 690 nm. In particular, the colorant-blended structural color system HR preferably satisfies the condition that the ratio (MH / ML) of the maximum reflectance MH (%) in the wavelength range of 600 to 750 nm to the maximum reflectance ML (%) in the wavelength range of 400 to 500 nm in the spectral reflectance curve obtained by measuring a 1 mm thick sample with a colorimeter against a black background satisfies the condition: MH / ML>1.00.

[0017] Furthermore, the HR blank of the present disclosure preferably has either (1) a cuttable portion having a single layer structure made of a colorant-blended structural color HR, or (2) a cuttable portion having a laminated structure of 2 to 3 layers, with one end layer of the laminated structure being made of a colorant-blended structural color HR, and the other layers being made of another colorant-blended structural color HR having an appearance color different from that of the colorant-blended structural color HR constituting the end layer, a structural color HR containing no colorant, or an HR other than these.

[0018] A second aspect of the present disclosure, a method for producing a crown, includes using 3D shape data of the patient's oral cavity on which an abutment tooth has been formed, to cut the cut portion of the HR blank of the present disclosure using CAD / CAM technology, thereby producing a crown to be applied to the abutment tooth. [Effects of the Invention]

[0019] The HR blank of the present disclosure has a small difference in color tone between the appearance color before cutting and the appearance color of the crown obtained after cutting, so a crown exhibiting the desired good color harmony can be produced by shade-taking based on the appearance color of the HR blank before cutting. DETAILED DESCRIPTION OF THE INVENTION

[0020] The inventors first investigated under what circumstances the problem of "desired color harmony cannot be obtained when a crown manufactured by cutting a conventional general HR blank, in which HR that has been tinted to a specific shade with a coloring agent is used for the cut portion, is actually fitted" occurred. As a result, it became clear that a crown is a dental prosthesis that covers an abutment tooth, and has a cavity for inserting the abutment tooth. Therefore, the thickness of the crown varies depending on the size and shape of the cavity (corresponding to the size and shape of the abutment tooth), and if the thickness of the cut product obtained after cutting is thin, the external color may differ significantly from that before cutting.

[0021] The reason why it is difficult to achieve good color matching for crowns fabricated using structural color HR blanks is thought to be as follows: In inlays, where the surfaces (sides and bottom) other than the exposed top surface are bonded to natural teeth, the light that determines the appearance color includes a large amount of light that has passed through the inlay, which reflects the color of the surrounding natural teeth, in addition to light that reflects the structural color, and therefore good color harmony can be achieved, whereas crowns are only bonded to the natural teeth internally, making it difficult to achieve this effect.

[0022] Conventional HR blanks have a certain degree of transparency, and the amount of colorant blended is fixed (it cannot be changed afterward), so changes in appearance color with thickness are unavoidable. In contrast, structural color HR blanks utilize structural colors (not colorants). By using colorants in combination within a range that does not impair the color harmony of the structural color, the effects of thickness and the proportion of exposed surface on color tone can be reduced, potentially solving both the first and second problems. Based on this idea, we investigated systems incorporating colorants into structural color HR blanks. We found that reducing the amount of colorant blended increases translucency. When the thickness after cutting is, for example, 2 mm or less, the base color shows through, significantly changing the appearance color. However, by using a relatively large amount of colorant with a similar color to the structural color to be developed, the appearance color change with thickness can be suppressed.

[0023] In other words, in this disclosure, by using structural color HR as the HR that constitutes the cut part and controlling the colorant blended, the change in shade due to thickness is suppressed for a certain range of shades, thereby solving the first problem. Also, for the structural color HR blank, the colorant blended to satisfy specific conditions solves the second problem.

[0024] It should be noted that structural color HR blanks contain a relatively high amount of coloring agents, which increases the risk of discoloration over long periods of use. Furthermore, several different shades (with varying coloring agent compositions) must be prepared to accommodate a wide range of shades, necessitating shade-taking. However, the significant benefit is that a single dental cutting blank can be used for both inlays and crowns. Furthermore, even when fabricating inlays, the color-matching effect achieved by harmonizing the structural color with the surrounding color is maintained to a certain extent, enabling highly aesthetic restorations. Furthermore, structural color HR blanks, which do not contain coloring agents, have the added benefit of eliminating concerns about the user's discomfort due to the difference in their appearance from the actual shade of the patient's teeth.

[0025] Without being bound by any particular theory, the inventors of the present invention speculate as follows as to why the above-mentioned problems become apparent when a colorant is blended into a structural color HR, and why they can be prevented by toning using a large amount of a colorant of a similar color to the structural color: The difference in the color-developing mechanisms between structural color and coloration by colorants causes the thickness of the resulting color to appear to be different. Therefore, when a large amount of a different-color colorant is blended, the balance of the toning is lost when the thickness is changed by cutting, resulting in a significant change in the appearance of the color. However, when colorants of the same color are blended, the structural color may exhibit a broad peak over a relatively wide wavelength range in the spectral reflectance curve, so that even if the balance between the two is lost due to a change in thickness, the appearance of the color is not significantly affected.

[0026] The HR blank of the present disclosure and a method for producing a crown using the HR blank will be described in detail below.

[0027] In this specification, unless otherwise specified, the expression "x to y" using 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, unless otherwise specified, the refractive index refers to the refractive index at 25°C measured with the sodium D line (wavelength 589 nm).

[0028] <Overview of HR Blank in this disclosure> The HR blank of the present disclosure has a major feature in that it uses structural color HR as the HR constituting the cuttable portion, and by blending a colorant to satisfy specific conditions, the cuttable portion is colored a predetermined shade, and the appearance color maintains this shade even when a crown is fabricated. The HR blank of the present disclosure also solves the problems specific to structural color HR blanks having a layer of structural color HR, as described in Patent Documents 4 and 5, and is characterized in that (1) by blending a specific amount of colorant to achieve color matching, it prevents the color of the base, such as an abutment tooth, from showing through and changing the appearance color when the crown is fabricated, and (2) by setting the ratio of a colorant of the same color as the structural color to be developed within a specific range in the blended colorant, it suppresses changes in appearance color due to thickness.

[0029] That is, the HR blank of the present disclosure is an HR blank having a cuttable portion of a single layer structure or a laminate structure including a layer made of a colorant-blended structural color system HR, in which inorganic particles are dispersed in a resin matrix and one or more types of colorants are further dispersed in the resin matrix of the structural color system HR that exhibits a structural color of a predetermined color tone, and in a spectral reflectance curve obtained by measuring a 3 mm thick sample made of a structural color system HR that does not contain a colorant against a black background using a color difference meter, the horizontal axis being the wavelength (nm) of reflected light and the vertical axis being the reflectance (%), the wavelength that gives the maximum reflectance derived from the structural color is The structural color system HR contains 800 to 8,000 mass ppm of a colorant based on the total mass of the colorant-containing structural color system, and the proportion of the same-color colorant in the colorant is 70 mass % or more, where the wavelength range A is the structural color wavelength, and the wavelength range B is the wavelength range that shows a reflectance of 85% or more of the maximum reflectance, and the wavelength that gives the maximum reflectance in the spectral reflectance curve obtained by measuring the colorant with a colorimeter against a black background is the color-developing wavelength of the colorant, and colorants whose color-developing wavelengths are within wavelength range A are defined as same-color colorants, and colorants whose color-developing wavelengths are outside wavelength range A are defined as different-color colorants.

[0030] Here, "colorant-free structural color HR" corresponds to the (colorant-free, dental) composite materials disclosed in Patent Documents 3-5. Specifically, it refers to a cured product of a (polymerization-curable) raw material composition used in producing a "colorant-containing structural color HR." The colorant is removed from the (polymerization-curable) raw material composition. The measurement to determine the structural color wavelength specifically refers to a spectral reflectance measurement performed on a 3 mm thick (e.g., gloss-polished) sample of the cured raw material composition against a black background using a spectrophotometer (e.g., Tokyo Denshoku Co., Ltd., "TC-1800MKII," halogen lamp: 12 V, 100 W, measurement wavelength range: 380-780 nm). Furthermore, the structural color wavelength and wavelength region A can be determined based on the spectral reflectance curve obtained in the above measurement, with the horizontal axis representing the wavelength (nm) of reflected light and the vertical axis representing reflectance (%), by reading the wavelength at which the structural color wavelength gives the maximum reflectance, and by reading the wavelength region where the reflectance is 85% or more of the maximum reflectance, for wavelength region A. Note that wavelength region A is usually a wavelength region between a wavelength shorter than the structural color wavelength at which the reflectance is 85% of the maximum reflectance, and a wavelength longer than the structural color wavelength at which the reflectance is 85% of the maximum reflectance.

[0031] Furthermore, the color-developing wavelength of a colorant can be determined by reading the wavelength at the point that gives the maximum reflectance on the spectral reflectance curve obtained by measuring the spectral reflectance in the same manner as above using a 3 mm-thick cured HR blank sample (which does not exhibit a structural color) containing the colorant alone in an amount of 2 to 10 mass % based on the total mass of the composition, against a black background.

[0032] In addition, if the reflectance peak (or pattern) derived from the colorant is known and can be distinguished from the reflectance peak (or pattern) derived from the structural color, the structural color wavelength and wavelength region A can also be determined based on the spectral reflectance curve obtained by measuring the spectral reflectance of a 3 mm thick sample made of the colorant-blended structural color system HR against a black background.

[0033] The HR blank of the present disclosure is not particularly different from a conventional HR blank except for the above-mentioned features, 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 in the shape of a rectangular parallelepiped or a cylinder, or a (solid) disk formed in the shape of a plate or board.

[0034] Furthermore, when the cuttable portion has a laminated structure including a layer made of a structural color system HR containing a colorant, it may also include a layer made of a structural color system HR containing no colorant or a layer made of a non-structural color system HR. For example, it is preferable that the cuttable portion has a laminated structure of 2 to 3 layers, with one end layer of the laminated structure being made of a structural color system HR containing a colorant, and the other layers being made of another structural color system HR containing a colorant having an appearance different from the colorant-containing structural color system HR constituting the end layer, a structural color system HR containing no colorant, or an HR other than these.

[0035] As mentioned above, HR blanks are often available in 16 shades broadly divided into group A (reddish-brown), group B (reddish-yellow), group C (gray), and group D (reddish-gray), or in a selection of several basic shades selected from these. From the viewpoint of ease of matching to each of these shades, it is preferable that the structural color wavelength be within the range of 590 to 690 nm. Furthermore, because the appearance color is less likely to change depending on the thickness after cutting when matching to these shades, it is preferable that the colorant-containing structural color HR satisfy the condition that the ratio (MH / ML) of the maximum reflectance (MH) in the wavelength range of 600 to 750 nm to the maximum reflectance (ML) in the wavelength range of 400 to 500 nm in the spectral reflectance curve obtained by measuring a 1 mm thick sample with a colorimeter against a black background is 1.00.

[0036] As mentioned above, structural color HRs include those that exhibit an opal effect, as described in Patent Document 5. Such structural color HRs are often used as materials that mimic the enamel of the incisal edge of a tooth by incorporating a small amount of colorant to achieve transparency. Even when used in dental cutting blanks, they are placed at the very edge of the laminate structure to form the incisal edge when processed into a crown. Therefore, the problem of the substrate showing through is less likely, and (due to their high transparency) the appearance color hardly changes with thickness. Meanwhile, structural color HRs that exhibit specific structural colors, as described in Patent Document 4, particularly those that develop (express) specific yellow-to-red structural colors, are sometimes incorporated with a large amount of colorant to achieve the above-mentioned shade and are used as materials for forming the region from the center to the cervical region of a crown that reflects the color of dentin. Therefore, the above-mentioned problems are more likely to become apparent, and the effects of the present invention are significant.

[0037] Therefore, in the following, we will briefly explain the structural color system HR and its raw material composition, focusing on the structural color system HR that expresses a specific structural color as a structural color system HR that does not contain a colorant, and then we will explain the HR blank of the present disclosure based on the structural color system HR.

[0038] <Structural color system HR> Patent Document 4 describes the conditions for a composite material equivalent to HR to exhibit a structural color (specific structural color) with a constant color tone that is not affected by changes in the angle of incidence of light due to light interference, etc. According to this, the following conditions I to V must be satisfied.

[0039] Condition I: The inorganic particles dispersed in the resin matrix of the cured product contain one or more "spherical particles of the same size" (G-PID).

[0040] G-PID refers to a group of inorganic spherical particles having a predetermined average primary particle diameter in the range of 100 to 1000 nm, where the individual inorganic spherical particles constituting the group are composed of substantially the same material, and in the number-based particle size distribution of the group, 90% or more of the total particles are present within a 5% range around the predetermined average primary particle diameter. The average primary particle diameter of inorganic spherical particles here refers to the average primary particle diameter (maximum diameter) of at least 30 particles observed within a unit field of view of a G-PID photographed with a scanning electron microscope. Furthermore, the term "spherical" refers to a particle that is approximately spherical, but does not necessarily need to be a perfect sphere. Specifically, the G-PID is photographed with a scanning electron microscope, and the maximum diameters of at least 30 particles observed within a unit field of view of the photograph are measured. The average uniformity, calculated by dividing the particle diameter in the direction perpendicular to the maximum diameter by the maximum diameter, is 0.6 or more, preferably 0.8 or more.

[0041] The structural color system HR in Patent Document 4 expresses a structural color of a color tone according to the average primary particle diameter of the G-PID, and in order to express a yellow to red structural color, preferably a specific structural color with a structural color wavelength in the range of 590 to 690 nm, it is said that it is necessary to contain G-PID with an average primary particle diameter of 230 to 800 nm.

[0042] Condition II: When the number of G-PIDs contained in inorganic particles is a, each G-PID is sorted in order of the smallest average primary particle diameter. m (However, m is 1 when a is 1, and is a natural number between 1 and a when a is 2 or more.) When a is 2 or more, each G-PID m The materials constituting the individual particles may be different from each other, and in this case, each G-PID m The average primary particle diameters of the particles differ from each other by 25 nm or more.

[0043] Condition III: The refractive index of the resin matrix is n (MX) and each G-PID m The refractive index of the inorganic spherical particles that make up the(G-PIDm) When (G-PIDm) Also, n (MX) <n (G-PIDm) The relationship is established.

[0044] From the viewpoint of visibility and clarity of the structural color, (G-PIDm) and n (MX) The difference between Δn(=n (G-PIDm) -n (MX) ) is any n (G-PIDm) The refractive index n of the resin matrix is preferably 0.001 to 0.1, more preferably 0.002 to 0.1, and even more preferably 0.005 to 0.05. (MX) is, for example, in the range of 1.40 to 1.57, and the refractive index n (G-PIDm) is, for example, in the range of 1.45 to 1.58.

[0045] Condition IV: A function representing the probability that other inorganic spherical particles are present at a point a distance r away from the center of any inorganic spherical particle dispersed in a composite material, which is determined based on a scanning electron microscope image in which the internal surface of the composite material is used as the observation plane, where <ρ> is the average particle density of the inorganic spherical particles in the observation plane, and where dn is the number of inorganic spherical particles present in the region between a circle at a distance r from any inorganic spherical particle in the observation plane and a circle at a distance r+dr from the inorganic spherical particle in the observation plane, and da is the area of the region (where da = 2πr dr), and is expressed by the following formula (1): g(r)={1 / <ρ>}×{dn / da} ···(1) When the function defined by g(r) is the radial distribution function, the arrangement structure of the inorganic spherical particles that make up all of the G-PID in the resin matrix has a short-range ordered structure that satisfies the following conditions 1 and 2. [Condition 1] In a radial distribution function graph showing the relationship between r / r0 and g(r) corresponding to r at that time, the x-axis is the dimensionless number (r / r0) obtained by dividing the distance r from the center of any inorganic spherical particle dispersed in the composite material by the average particle diameter r0 of all inorganic spherical particles dispersed in the composite material, and the y-axis is the radial distribution function g(r), the nearest inter-particle distance r1, defined as the r corresponding to the peak top of the peak closest to the origin among the peaks appearing in the radial distribution function graph, is between 1 and 2 times the average particle diameter r0 of all inorganic spherical particles dispersed in the composite material. [Condition 2] When r corresponding to the peak top of the second-nearest peak from the origin among the peaks appearing in a radial distribution function graph is defined as the next nearest interparticle distance: r2, the minimum value of the radial distribution function: g(r) between the nearest interparticle distance: r0 and the next nearest interparticle distance: r2 is a value between 0.56 and 1.10.

[0046] Condition V: It is possible to include "ultrafine particle group" (G-SFP), which is an aggregate of inorganic particles with an average primary particle diameter of less than 100 nm. In this case, the average primary particle diameter of G-SFP must be at least 25 nm smaller than the average primary particle diameter of G-PID1.

[0047] The average primary particle diameter of inorganic particles referred to here means the average value of the primary particle diameter (maximum diameter) of each of 30 or more particles selected from a unit field of view of a photograph of G-SFP taken with a scanning electron microscope.

[0048] <Raw material composition for structural color HR> Patent Document 4 describes that a cured product (a composite material equivalent to HR) satisfying conditions I to V is a curable composition that contains 100 parts by mass of a polymerizable monomer, 10 to 1500 parts by mass of one or more uniform particle diameter spherical particles (G-PID), and 0.01 to 10 parts by mass of a polymerization initiator, and may optionally contain 0.1 to 50 parts by mass of an ultrafine particle group (G-SFP), and that the curable composition can be produced by mixing the components by the mixing method shown in (a) or (b) below and curing the resulting curable composition. (a) A method in which a curable composition having the same or substantially the same composition as the curable composition to be actually produced is mixed in advance under a plurality of different mixing conditions, and the radial distribution function g(r) of the cured product of the mixture obtained when mixed under each mixing condition is examined to determine the mixing conditions that satisfy conditions 1 and 2, and then the same mixing conditions as the determined mixing conditions are adopted. (b) A method in which a portion of the mixture obtained during and / or after the mixing process is sampled, and the dispersion state of the inorganic particles in the hardened product of the sampled mixture is confirmed to satisfy conditions 1 and 2, and mixing is continued until these conditions are satisfied.

[0049] Hereinafter, among the curable compositions prepared by such a method to give a cured product satisfying conditions I to V, those that do not contain a colorant will also be referred to as "colorant-free specific structural color HR raw material composition."

[0050] Furthermore, Patent Document 4 also describes that, because this makes it easier for the cured body (composite material) to have the above-mentioned short-range ordered structure, it is preferable that at least a portion of one or more uniform-particle-size spherical particle groups (G-PID) comprise one type of uniform-particle-size spherical particle group and a resin whose refractive index is smaller than that of the inorganic spherical particles that make up the one type of uniform-particle-size spherical particle group, and that the G-PID be blended as an organic-inorganic composite filler that does not contain any uniform-particle-size spherical particle groups other than the one type of uniform-particle-size spherical particle group (i.e., an organic-inorganic composite filler that contains only a single uniform-particle-size spherical particle group), or that the G-PID be blended as aggregated particles with a particle size of 5 to 200 μm, in which the inorganic spherical particles are aggregated.

[0051] On the other hand, Patent Document 5 describes that a dental composite restorative material containing (A) 100 parts by mass of a polymerizable monomer, (B) 100 to 400 parts by mass of spherical silica-based particles having an average particle size in the range of 0.1 to 0.5 μm and a standard deviation of the particle size distribution of 1.30 or less, (C) 50 to 450 parts by mass of an organic-inorganic composite filler in which the silica-based particles are dispersed in an organic resin matrix, and (D) 0.01 to 10 parts by mass of a polymerization initiator, wherein the difference in refractive index between the cured product of the polymerizable monomer (A) and the organic-inorganic composite filler (C) is 0.1 or less and the refractive index of the cured product of the polymerizable monomer (A) is greater than the refractive index of the silica-based particles, exhibits a good opal effect.

[0052] Patent Documents 4 and 5 also provide detailed explanations of the components that make up the raw material composition, namely, the polymerizable monomer, the inorganic particles or silica-based particles, and the polymerization initiator.

[0053] Examples of the polymerizable monomer include methyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid, N-(meth)acryloylglycine, 2-(meth)acryloyloxybenzoic acid, 6-(meth)acryloyloxyethylnaphthalene-1,2,6-tricarboxylic acid anhydride, 13-(meth)acryloyloxytridecane-1,1-dicarboxylic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide, N, (Meth)acrylic monomers such as N-(dihydroxyethyl)(meth)acrylamide, 2,2-bis[methacryloyloxyphenyl]propane, 2,2-bis[(3-methacryloyloxy-2-hydroxypropyloxy)phenyl]propane, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,6-bis(methacrylethyloxycarbonylamino)trimethylhexane, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, and neopentyl glycol dimethacrylate; and vinyl monomers such as p-vinylbenzoic acid are preferably used. In this specification, the term "(meth)acrylate" refers to both "acrylate" and "methacrylate." The same applies to terms such as "(meth)acrylic acid," "(meth)acryloyl," and "(meth)acrylamide."

[0054] As these polymerizable monomers, a plurality of types of polymerizable monomers are usually used in order to adjust the physical properties of the cured product. In this case, the types and amounts of the polymerizable monomers are set so that the refractive index of the mixture of polymerizable monomers is in the range of 1.38 to 1.55, which is the above-mentioned n (MX) <n (G-PIDm) It is desirable from the viewpoint that the following condition can be easily satisfied. The refractive index of the polymerizable monomer or the cured product of the polymerizable monomer can be determined using an Abbe refractometer.

[0055] The inorganic spherical particles constituting G-PID and the inorganic particles constituting G-SFP, as well as the silica-based particles, may be made of amorphous silica or silica-titanium group element oxide composite oxides (silica-zirconia, silica-titania, etc.). The composite ratio of the silica-titanium group element oxide composite oxide is not particularly limited, but a preferred ratio is, for example, 70 to 95 mol% silica and 5 to 30 mol% titanium group element oxide. These inorganic particles may be surface-treated with a silane coupling agent.

[0056] Suitable polymerization initiators include thermal polymerization initiators such as peroxides (e.g., benzoyl peroxide, p-chlorobenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxydicarbonate, diisopropylperoxydicarbonate, etc.); azo compounds (e.g., azobisisobutyronitrile); boron compounds (e.g., tributylborane, tributylborane partial oxide, sodium tetraphenylborate, sodium tetrakis(p-fluorophenyl)borate, triethanolamine tetraphenylborate, etc.); barbituric acids (e.g., 5-butylbarbituric acid, 1-benzyl-5-phenylbarbituric acid, etc.); and sulfinic acid salts (e.g., sodium benzenesulfinate, sodium p-toluenesulfinate, etc.). These polymerization initiators may be used alone or in combination. It is also possible to combine multiple initiators with different polymerization methods.

[0057] The raw material composition may also contain other additives such as a polymerization inhibitor and an ultraviolet absorber, provided that the effects of the composition are not impaired.

[0058] <Colorant-containing structural color HR and its raw material composition> The colorant-blended structural color HR that constitutes at least one layer of the cuttable portion of the single-layer or multilayer structure of the HR blank of the present disclosure is a structural color HR (not containing a colorant) blended with a specific amount of a specific colorant, and is obtained by curing a raw material composition for a colorant-blended structural color HR, in which a specific amount of a specific colorant is blended with a raw material composition (for the structural color HR). Therefore, the components and composition other than the colorant are as explained in the section <Raw material composition for the structural color HR>, and there are no particular changes.

[0059] To explain the specific colorant and the specific blending amount, the specific colorant refers to a colorant containing 70% or more by mass of a same-color colorant (less than 30% by mass of a different-color colorant), which is a colorant present within wavelength region A determined based on the structural color wavelength and the reflectance at that wavelength. The specific blending amount refers to an amount that is 800 to 8,000 ppm by mass based on the total mass of the colorant-blended structural color system HR. If the proportion of same-color colorants in the blended colorants is less than 70% by mass, the appearance color is likely to change depending on the thickness after cutting. Furthermore, if the blending amount of the colorant is less than 800 ppm by mass, the color of the base material will show through after cutting, making the appearance color more likely to change. If the blending amount is more than 8,000 ppm by mass, the color derived from the colorant before cutting will be too strong, making shade-taking based on the appearance color difficult. From the perspective of effectiveness, the blending amount of the colorant is preferably 900 to 6,000 ppm by mass, and more preferably 2,000 to 3,500 ppm by mass. Furthermore, the colorants of the same color family may be a mixture of different types. Furthermore, in a spectral reflectance curve obtained by measuring a 1 mm thick sample against a black background using a color difference meter, it is preferable that the ratio (MH / ML) of the maximum reflectance MH (%) in the wavelength range of 600 to 750 nm to the maximum reflectance ML (%) in the wavelength range of 400 to 500 nm satisfies the condition MH / ML > 1.00, and more preferably MH / ML > 1.20.

[0060] Pigments and / or dyes are preferably used as colorants. Representative examples of pigments include inorganic pigments, such as titanium oxide, zinc oxide, zirconium oxide, zinc sulfide, aluminum silicate, calcium silicate, carbon black, iron oxide, copper chromite black, chromium oxide green, chrome green, violet, chrome yellow, lead chromate, lead molybdate, cadmium titanate, nickel titanium yellow, ultramarine blue, cobalt blue, bismuth vanadate, cadmium yellow, and cadmium red. While inorganic pigments are also inorganic particles, their amount is minimal compared to the amount of G-PID or G-SFP, and therefore does not affect the amount of these particles. Organic pigments, such as monoazo pigments, diazo pigments, diazo condensation pigments, perylene pigments, and anthraquinone pigments, can also be used. Examples of dyes include red dyes such as KAYASET RED G and KAYASET RED B (both manufactured by Nippon Kayaku Co., Ltd.); yellow dyes such as KAYASET Yellow 2G and KAYASET Yellow GN (both manufactured by Nippon Kayaku Co., Ltd.); and blue dyes such as KAYASET Blue N, KAYASET Blue G and KAYASET Blue B (both manufactured by Nippon Kayaku Co., Ltd.). Considering color stability in the oral cavity, it is preferable to use water-insoluble pigments rather than water-soluble dyes.

[0061] These colorants are classified into same-color colorants and different-color colorants according to the wavelength of color they emit and are blended.

[0062] In addition, because of its moderate transparency and high structural color development effect, it is preferable to use a colorant-containing raw material composition for specific structural color HR, which is a colorant-containing raw material composition for specific structural color HR, in which a specific amount of a specific colorant is blended with a colorant-free raw material composition for specific structural color HR. In this case, if G-SFP is not included, the amount of G-PID is preferably 100 to 900 parts by mass, more preferably 150 to 700 parts by mass, per 100 parts by mass of polymerizable monomer. Furthermore, if G-SFP is included, it is preferable to use an amount obtained by subtracting the amount of G-SFP from the above-mentioned amount.

[0063] Furthermore, from the viewpoint of ease of color matching to shades A to D, the structural color wavelength is preferably 550 to 770 nm, and more preferably 590 to 690 nm. Therefore, the average primary particle diameter of the G-PID is preferably 230 to 800 nm, more preferably 240 to 500 nm, and even more preferably 260 to 350 nm. Furthermore, the number a of G-PIDs contained is preferably 1 to 3, and more preferably 1 or 2. When at least a portion of these G-PIDs is blended as an organic-inorganic composite filler, the average particle diameter of the organic-inorganic composite filler is preferably 2 to 100 μm, more preferably 5 to 50 μm, and even more preferably 5 to 30 μm, from the viewpoint of improving the mechanical strength of the cured body and the handleability of the curable paste.

[0064] The colorant-containing structural color HR raw material composition can be prepared by kneading and degassing predetermined amounts of the above-mentioned components. In particular, kneading using a kneading device such as a planetary stirrer is preferred because it allows for kneading in a short time to produce a hardened product in a dispersed state that satisfies conditions 1 and 2, and also facilitates scale-up production. Furthermore, degassing under reduced pressure is preferred because it allows for the removal of air bubbles in a short time, even from a highly viscous composition.

[0065] The colorant-blended structural color HR raw material composition thus obtained can be polymerized and cured by the action of a polymerization initiator to produce a colorant-blended structural color HR. When a thermal polymerization initiator is used, the polymerization temperature is preferably 70 to 150°C, more preferably 80 to 130°C, because this allows the polymerization to proceed sufficiently while preventing discoloration due to heat, and a high-strength colorant-blended structural color HR can be obtained.

[0066] <Method for manufacturing HR blanks according to the present disclosure> The HR blank of the present disclosure can be suitably produced by casting polymerization of a colorant-containing structural color HR raw material composition, particularly a colorant-containing specific structural color HR raw material composition, regardless of whether the cut processing portion has a single-layer structure or a laminated structure.

[0067] That is, the HR blank of the present disclosure is produced by the following steps (i) to (iii): (i) a step of mixing 100 parts by mass of a polymerizable monomer, 10 to 1500 parts by mass of one or more uniform particle diameter spherical particles (G-PID), 0.01 to 10 parts by mass of a polymerization initiator, and, if necessary, 0.1 to 50 parts by mass of an ultrafine particle group (G-SFP) by the mixing method shown in (a) or (b) above to prepare a colorant-free raw material composition for specific structural color HR; (ii) A 3 mm thick sample made of structural color system HR, which is a hardened product of a raw material composition for specific structural color system HR that does not contain a colorant, is measured with a color difference meter against a black background. In the spectral reflectance curve, the horizontal axis represents the wavelength (nm) of reflected light and the vertical axis represents reflectance (%). The wavelength that gives the maximum reflectance due to the structural color is defined as the structural color wavelength, and the wavelength region showing a reflectance of 85% or more of the maximum reflectance is defined as A. For the colorant, the wavelength that gives the maximum reflectance in the spectral reflectance curve obtained by measuring with a color difference meter against a black background is defined as A. a step of blending a colorant, the colorant having a ratio of the same color colorant of 70 mass % or more, with a colorant-free raw material composition for specific structural color HR, so that the content is 800 to 8,000 mass ppm based on the total mass of the colorant-free raw material composition for specific structural color HR and the colorant, wherein the colorant wavelength is the color development wavelength of the colorant, and colorants whose color development wavelengths are within wavelength region A are defined as same-color colorants and colorants whose color development wavelengths are outside wavelength region A are defined as different-color color colorants; and (iii) a step of subjecting the colorant-containing specific structural color HR raw material composition to cast polymerization; It is particularly preferred to produce the polymerizable compound by a method comprising the steps of:

[0068] Here, cast polymerization refers to the process of filling a mold of a predetermined shape with a polymerizable and curable composition, followed by polymerization and curing. The volume of the mold can be selected appropriately depending on the desired shape. Similarly, the shape of the mold can be prismatic, cylindrical, rectangular, disc-like, or any other irregular shape, and is not particularly limited. During polymerization, pressure can be applied with an inert gas such as nitrogen, if necessary. A mold having the same or substantially the same shape as the part to be machined is prepared, and the curable raw material compositions that will form each layer are sequentially filled to a predetermined thickness inside the mold, followed by polymerization and curing. The resulting bulk body (HR laminate) can be used as the part to be machined as is, or it can be filled into a mold of a larger size to produce a bulk body, which can then be punched or machined to form the part to be machined. Known techniques can be used for the filling method, and there are no particular limitations. For example, the mold can be filled by injection, extrusion, pressing, or the like.

[0069] The mold may be made of a material such as metal, ceramic, or resin depending on the purpose, and it is preferable to use a material that has a higher heat resistance than the polymerization temperature to be carried out. Examples of mold materials include SUS, high-speed tool steel, aluminum alloy, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and polystyrene (PS).

[0070] The obtained bulk body can be subjected to post-processing such as heat treatment, polishing, cutting, attachment of a holder, and printing, as needed. Furthermore, if necessary, a holding pin can be attached to secure the dental cutting blank to a cutting machine. The shape of the holding pin is not particularly limited as long as it can secure the dental cutting blank to the cutting machine, and it may not be provided depending on the shape of the dental cutting blank and the requirements of the machine. Examples of materials for the holding pin include stainless steel, brass, and aluminum. The method of securing the holding pin to the part to be cut (dental cutting blank body) is not limited to adhesive bonding, and can also be methods such as fitting or screwing. The adhesive method is also not particularly limited, and various commercially available adhesives such as isocyanate-based, epoxy-based, urethane-based, silicone-based, and acrylic-based adhesives can be used.

[0071] <How to make a crown> The HR blank of the present disclosure has a small difference in color tone between its appearance before cutting and its appearance after cutting to a thin thickness, making it suitable for use in producing crowns.

[0072] The method for producing the crown is not particularly limited, and it is preferable to produce a crown to be applied to the abutment tooth by, for example, using 3D shape data of the patient's oral cavity in which the abutment tooth has been formed, cutting the cut portion of the HR blank of the present disclosure using CAD / CAM technology.

[0073] After cutting, the shape may be further modified using a dental engineering tool or the surface may be polished. If necessary, the color tone may be adjusted using a penetrating colorant or a clarifying liquid. [Example]

[0074] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0075] 1. Hybrid resin raw materials The raw materials and physical properties of the hybrid resins used in the examples and comparative examples are described below.

[0076] (1) Polymerizable monomer component As the polymerizable monomer component, M1, a polymerizable monomer mixture having the composition shown in Table 1, was used. The abbreviations in the polymerizable monomer column in the table represent the following compounds, and the numbers in parentheses represent the parts by mass used. UDMA: 1,6-bis(methacrylethyloxycarbonylamino)trimethylhexane 3G: Triethylene glycol dimethacrylate

[0077] The refractive index before curing (M1) and after curing (cured product) were measured using an Abbe refractometer (manufactured by Atago Co., Ltd.) in a thermostatic chamber at 25°C. The cured product sample was prepared by adding 0.2 mass% of camphorquinone (CQ), 0.3 mass% of ethyl pN,N-dimethylaminobenzoate (DMBE), and 0.15 mass% of hydroquinone monomethyl ether (HQME) as photopolymerization initiators to 100 mass% of the polymerizable monomer mixture M1, uniformly mixing the mixture, placing it in a mold with a 7 mm diameter x 0.5 mm through-hole, pressing polyester films onto both sides, and then irradiating the mixture with a light intensity of 500 mW / cm. 2 The specimen was cured by irradiating it with light for 30 seconds using a halogen-type dental light irradiator (Cybron, "Demetron LC"), and then removed from the mold. When the cured specimen was set in the Abbe refractometer, a solvent (bromonaphthalene) that did not dissolve the specimen but had a higher refractive index than the specimen was dropped onto the specimen to ensure close contact between the specimen and the measurement surface.

[0078] [Table 1]

[0079] (2) Group of spherical particles with the same particle size (G-PID) According to the method disclosed in the examples of Patent Document 4, spherical fillers made of a composite oxide having a molar ratio of SiO2 / ZrO2 / Na2O of 89.8 / 9.0 / 1.2 were prepared by a sol-gel method, and surface treatment was performed with γ-methacryloyloxypropyltrimethoxysilane to prepare G-PID1 to G-PID6 listed in Table 2.

[0080] (3) Irregular inorganic filler The amorphous inorganic filler F1 (amorphous silica-zirconia particles) shown in Table 2 was prepared by the method described in JP-A-2-132102, JP-A-3-197311, etc., by dissolving an alkoxysilane compound in an organic solvent, adding water to the solution to partially hydrolyze it, and then adding an alkoxide of another metal to be composited and an alkali metal compound to hydrolyze it to produce a gel-like substance, and then drying the gel-like substance and, if necessary, pulverizing and firing it.

[0081] [Table 2]

[0082] The average primary particle size, average uniformity, particle proportion within ±5% [proportion (%) of the number of particles present within a 5% range around the average primary particle size in the number-based particle size distribution to the total number of particles], and refractive index shown in Table 2 are values measured according to the method described in the examples of Patent Document 4.

[0083] That is, the average primary particle diameter means a value obtained by processing a photograph of powder taken with a scanning electron microscope (magnification: 5000 to 100000 times) using image analysis software, measuring the primary particle diameters (maximum diameters) of 30 or more particles observed within a unit field of view, and dividing the sum by the number of particles.

[0084] The average uniformity refers to the sum of the ratios (Bi / Li) of the major axis (Li) of the 30 or more particles to the minor axis (Bi), which is the diameter perpendicular to the major axis, divided by the number of particles.

[0085] The particle ratio within ±5% means a value calculated according to the following formula. Particle ratio within ±5% (%) = (N1 / N0) x 100 N1: The number of particles within a particle size range of 5% around the average primary particle size within a unit field of view of a scanning electron microscope photograph N0: Total number of particles within a unit field of view of a scanning electron microscope photograph

[0086] The refractive index refers to the refractive index at 25°C relative to the sodium D line, measured by the immersion method, in which 1-bromotoluene is added as a droplet to a dispersion liquid using anhydrous toluene as a dispersion medium to make the liquid transparent.

[0087] (3) Organic-inorganic composite filler Organic-inorganic composite fillers CF1 and CF2 were prepared using G-PID2 and G-PID5, respectively, as shown in Table 2, as follows. First, a dispersion of 100 g of G-PID2 or G-PID5 in 200 g of water was obtained using a circulation mill, SC Mill (manufactured by Nippon Coke Engineering Co., Ltd.). Next, a separately prepared mixture of 4 g of γ-methacryloyloxypropyltrimethoxysilane, 0.003 g of acetic acid, and 80 g of water (pH 4) was added to the dispersion and mixed until uniform. After that, the dispersion was gently mixed and fed onto a rotating disk at high speed for spray drying to granulate. The resulting powder was then vacuum dried at 60°C to obtain roughly spherical aggregates. Next, 50 g of the aggregates were immersed in a polymerizable monomer solution containing 10 g of polymerizable monomer mixture M1, 0.025 g of azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and 5.0 g of methanol as an organic solvent. After thorough stirring, the organic solvent was removed, and the polymerizable monomer mixture was polymerized and cured by heating for 1 hour under conditions of a reduced pressure of 10 hPa and 100°C. This procedure yielded organic-inorganic composite fillers CF1 and CF2 that were approximately spherical and had an average particle size of 10 μm.

[0088] (4) Ultrafine particles (G-SFP) As the G-SFP, Reolosil QS-102 (average primary particle diameter: 12 nm, manufactured by Tokuyama Corporation) was used.

[0089] (5) Polymerization initiator A thermal polymerization initiator consisting of benzoyl peroxide (BPO) was used.

[0090] (6) Coloring agent Colorants G1 to G6 were prepared and used by mixing the three pigments shown below, R (red), Y (yellow), and B (blue), in the mass ratios shown in Table 3. The color-developing wavelength of each pigment was determined by reading the wavelength at the point giving the maximum reflectance on the spectral reflectance curve obtained by measuring the spectral reflectance of a 3 mm-thick cured HR blank sample (which does not exhibit structural color) containing 2 to 10 mass% of each colorant alone, based on the total mass of the composition, against a black background. R: Red pigment (Pigment Red 166), color wavelength: 680 nm Y: Yellow pigment (Pigment Yellow 95), color wavelength: 590 nm B: Blue pigment (Pigment Blue 60), color wavelength: 430 nm

[0091] In Table 3, the proportion of each colorant is expressed in ppm by mass, which means the mass ppm relative to the total mass of the colorant-blended structural color system HR prepared in the Examples and Comparative Examples described below. Furthermore, the "reference shade" in Table 3 refers to the VITA Shade Guide shade corresponding to the HR blank used in the Examples and Comparative Examples described below (each of which contains only one of G1 to G6 blended according to the above). In other words, the compositions (ppm by mass) of G1 to G6 are determined so that the HR blank used in the Examples and Comparative Examples described below, which contains only one of these blends, will have the reference shade.

[0092] [Table 3]

[0093] 2. Examples and Comparative Examples Example 1 (1) Preparation of structural color system HR containing colorants 20 parts by weight of polymerizable monomer mixture M1 and 1.0 part by weight of BPO were mixed, followed by the addition of 80 parts by weight of G-PID1, 1 part by weight of G-SFP, and the colorant G4 (ppm, as listed in Table 3). The mixture was then mixed using a planetary mixer until uniform, forming a paste. The resulting paste was vacuum degassed and then filled into a mold cavity with a cylindrical cavity having a roughly rectangular shape with a thickness of 14.5 mm and a cross section of 14.5 mm x 18 mm. The paste was then pressurized with nitrogen at 0.4 MPa in a pressure vessel and placed in a heating device at 90 °C. The mixture was then heated in this state for 15 hours to polymerize and harden. It was then cooled to room temperature at a cooling rate of 20 °C / min and removed from the mold to obtain a block-shaped colorant-blended structural color HR (cured product) corresponding to the shape of the cavity.

[0094] (2) Measurement of structural color wavelength and confirmation of the content ratio of the same color and different color colorants A block-shaped cured product of colorant-free structural color system HR (hereinafter also referred to as "base structural color system HR") was obtained in the same manner as in the preparation of the colorant-blended structural color system HR described above (1), except that colorant G4 was not added. From the resulting block-shaped cured product, rectangular plates with a thickness of 3 mm and a main surface measuring 12 mm x 14 mm were cut and polished to prepare solid samples for structural color wavelength measurement. The spectral reflectance of this solid sample for structural color wavelength measurement was measured using a spectrophotometer (Tokyo Denshoku Co., Ltd., "TC-1800MKII," halogen lamp: 12 V, 100 W, measurement wavelength range: 380-780 nm) against a black background using black carbon tape, and a spectral reflectance curve was obtained. The wavelength at which the reflectance reached its maximum was read from the resulting spectral reflectance curve, and the structural color wavelength was determined to be 670 nm. Furthermore, the wavelength range A showing a reflectance of 85% or more of the maximum reflectance was determined to be in the range of 590-750 nm. From these results, it was confirmed that in the colorant-blended structural color system HR of Example 1, Y and R are colorants of the same color, B is a colorant of a different color, and the proportion of colorants of the same color in the colorants is 71% by mass.

[0095] (3) Check MH / ML From the block-shaped colorant-blended structural color system HR (cured product) obtained in (1) above, a rectangular plate with a thickness of 1 mm and a main surface of 12 mm x 14 mm was cut out, polished to a high gloss, and measured using a colorimeter against a black background. The ratio (MH / ML) of the maximum reflectance ML (%) in the wavelength range of 400 to 500 nm to the maximum reflectance MH (%) in the wavelength range of 600 to 750 nm in the obtained spectral reflectance curve was calculated to be 1.13.

[0096] (4) Color compatibility evaluation of structural color system HR containing colorants A block-shaped colorant-blended structural color system HR (cured product) was used as Sample 1, and the following appearance color comparisons were performed. Next, rectangular plates with a thickness of 2 mm and a main surface measuring 12 mm x 14 mm were cut from the colorant-blended structural color system HR and polished to a high gloss to create solid samples (Sample 2), and the following appearance color comparisons were performed. The appearance comparisons were performed by arranging each sample against a black background and the "A3" VITA Shade Guide, which corresponds to colorant G4, and visually comparing the appearance color. Color compatibility was evaluated according to the following criteria. Sample 1 was rated "A," and Sample 2 was rated "B." -Evaluation criteria- A: The color tone matches well with the VITA Shade Guide. B: The color tone is similar to the color tone of the VITA Shade Guide. C: The shade is similar to the shade in the VITA Shade Guide, but the fit is not good. D: The shade does not match the shade in the VITA Shade Guide.

[0097] <Examples 2 to 19 and Comparative Examples 1 to 13> In Examples 2 to 19 and Comparative Examples 1 to 13, pastes (raw material compositions for base structural color system HR) were prepared in the same manner as in Example 1, except that the type and amount of inorganic particles (or inorganic particles and organic-inorganic composite filler) shown in the inorganic particles column of Tables 4 and 5 (expressed as parts by mass relative to 20 parts by mass of polymerizable monomer mixture M1) were used instead of G-PID1 (80 parts by mass) used in Example 1. As shown in the footnotes of Tables 4 and 5, the parenthesized figures indicating the amount of organic-inorganic composite filler indicate the amount (parts by mass) of the organic-inorganic composite filler, and the amount (parts by mass) of inorganic particles contained in the organic-inorganic composite filler was 80% of that figure. Furthermore, the structural color wavelength and wavelength region A were measured using the resulting pastes (raw material compositions for base structural color system HR) in accordance with (2) of Example 1. The results are also shown in Tables 4 and 5.

[0098] In each example, a block-shaped colorant-blended structural color system HR (cured product) was prepared in the same manner as in Example 1, except that the type and amount of colorant shown in Tables 6 and 7 was blended into the raw material composition of the base structural color system HR obtained as described above, and measurements and evaluations were carried out in the same manner as in Example 1. The results are shown in Tables 6 and 7. Note that in the color compatibility evaluation shown in Tables 6 and 7, "before cutting" indicates the results corresponding to Sample 1, and "after cutting" indicates the results corresponding to Sample 2. In addition, as the VITA shade guide to be used for comparing appearance color, a shade guide of the reference shade (shown in Table 3) for each colorant was used depending on the colorants (G1 to G6) used.

[0099] [Table 4]

[0100] [Table 5]

[0101] [Table 6]

[0102] [Table 7]

[0103] As shown in Tables 6 and 7, Examples 1 to 19, which used inorganic particle compositions with structural color wavelengths of 590 to 690 nm, showed good color matching before and after cutting. In all of Examples 1 to 19, the proportion of colorants of the same color in the colorant was 70 mass% or more, and the MH / ML value was 1.00 or more.

[0104] In contrast, in Comparative Examples 1 to 9, which used inorganic particle compositions with structural color wavelengths of less than 590 nm or more than 690 nm, the proportion of different-color colorants in the colorant was greater than 30% by mass, and the color compatibility evaluation after cutting was "C" or "D" in all cases. In particular, Comparative Examples 2 and 4 to 9 exhibited a bluish structural color and had short structural color wavelengths, resulting in the proportion of same-color colorants being less than 30% by mass (the proportion of different-color colorants being more than 70% by mass), and furthermore, the MH / ML value was significantly below 1, and therefore the color compatibility evaluation after cutting was "D."

[0105] In addition, in Comparative Examples 10 to 13, which used HR blanks (normal HR blanks that do not exhibit structural color) made with amorphous filler F1 as inorganic particles, the change in appearance color with the change in sample thickness was significant, and a discrepancy was observed between the color compatibility evaluations before and after cutting. For example, in Comparative Example 10, the color compatibility evaluation before cutting was "A," but the evaluation after cutting deteriorated to "D."

Claims

1. A dental hybrid resin blank for cutting has a cutting portion of a single layer structure or a laminate structure including a layer made of a colorant-blended structural color hybrid resin that is toned to a specific shade selected from a total of 16 shades of tooth color samples, namely, A series (A1, A2, A3, A3.5, A4), B series (B1, B2, B3, B4), C series (C1, C2, C3, C4), and D series (D2, D3, D4), in which inorganic particles are dispersed in a resin matrix and one or more types of colorants are further dispersed in the resin matrix of the structural color hybrid resin that exhibits a predetermined structural color tone, A 3 mm thick sample made of the structural color hybrid resin containing no colorant is measured with a color difference meter against a black background, and the spectral reflectance curve is obtained with the horizontal axis representing the wavelength (nm) of reflected light and the vertical axis representing reflectance (%). The wavelength that gives the maximum reflectance derived from the structural color is defined as the structural color wavelength, and the wavelength region showing a reflectance of 85% or more of the maximum reflectance is defined as A. Regarding the colorant, the wavelength at which the maximum reflectance is obtained in a spectral reflectance curve obtained by measurement using a color difference meter against a black background is defined as the color emission wavelength of the colorant, and colorants whose color emission wavelength is within the wavelength region A are defined as same-color colorants, and colorants whose color emission wavelength is outside the range of wavelength region A are defined as different-color colorants. A hybrid resin blank for dental cutting processing, containing 800 to 8000 mass ppm of colorant based on the total mass of the colorant-blended structural color hybrid resin, and the proportion of the same color colorant in the colorant is 70 mass % or more.

2. The hybrid resin-based blank for dental cutting according to claim 1, wherein the structural color wavelength is in the range of 590 to 690 nm.

3. The hybrid resin blank for dental cutting described in claim 2, wherein the colorant-blended structural color hybrid resin satisfies the condition that the ratio (MH / ML) of the maximum reflectance MH (%) in the wavelength range of 600 to 750 nm to the maximum reflectance ML (%) in the wavelength range of 400 to 500 nm in the spectral reflectance curve obtained by measuring a 1 mm thick sample with a color difference meter against a black background is MH / ML > 1.

00.

4. 2. The hybrid resin blank for dental cutting according to claim 1, wherein the cutting portion has a single layer structure made of the colorant-containing structural color hybrid resin.

5. 2. The hybrid resin blank for dental cutting according to claim 1, wherein the cutting portion has a laminated structure of 2 to 3 layers, one end layer of the laminated structure is made of the colorant-blended structural color hybrid resin, and the other layers are made of another colorant-blended structural color hybrid resin having an appearance color different from the colorant-blended structural color hybrid resin constituting the one end layer, a structural color hybrid resin not blended with a colorant, or a hybrid resin other than these.

6. A method for producing a crown, comprising: using 3D shape data of the patient's oral cavity on which an abutment tooth has been formed, and cutting the cutting portion of the hybrid resin-based blank for dental cutting described in claim 1 using CAD / CAM technology to produce a crown to be applied to the abutment tooth.

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