Mill blank for polyurethane-based dental-cutting and producing method thereof

Abstract

To provide a mill blank for dental cutting having a part to be cut formed of a polyurethane molding capable of preparing a denture excellent in physical characteristics by a CAD / CAM system and excellent in machinability.SOLUTION: When obtaining the polyurethane molded body by causing the polyol component (I) and the diisocyanate component (II) to undergo a polyaddition such that the ratio of isocyanate groups in (II) to the total number of hydroxyl groups in (I) is 0.9 to 1.1, select the compounds constituting each component so that the indicators related to the chemical crosslinks and urethane bonds introduced into the polyurethane-namely, the average crosslinking number (NCP) and the distance between urethane groups (D), each calculated according to a specific formula-satisfy NCP=2.0 to 3.0 and D=5 to 9.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyurethane-based dental mill blank for cutting, and more particularly to a polyurethane-based dental mill blank for cutting that can be suitably used as a cutting material for producing dental prostheses by cutting using a dental CAD / CAM system. [Background technology]

[0002] In dental treatment, one method for creating dental prostheses such as inlays, crowns, bridges, and denture bases is to use a dental CAD / CAM system for machining. A dental CAD / CAM system uses a computer to design dental prostheses based on three-dimensional coordinate data, and then uses a machining machine to create the prosthesis. A variety of materials are used for machining, including glass ceramics, zirconia, titanium, and resin. In particular, organic resin dental machining materials such as polymethyl methacrylate (PMMA) resin are used for denture bases.

[0003] On the other hand, polyurethane resins are known as resins for producing denture bases. By changing the raw materials, polyurethane resins can be made to have properties ranging from lens-like to rubber-like, and therefore the production of dentures from thermoplastic polyurethane resins has long been considered (see Patent Document 1).

[0004] Furthermore, polyamide resin has the excellent characteristic of being fracture-resistant, and has been used since the 1950s as a material for prosthetic devices such as partial dentures. However, it is known that polyamide resin has poor adhesion to denture base lining materials used to repair denture bases made from polyamide resin (see Patent Document 1 and Non-Patent Document 1).

[0005] Incidentally, dental mill blanks for machining denture bases, particularly for complete dentures, are widely used commercially as "standard disks." These disk-shaped (disk-shaped or low-height cylindrical) blanks have a standardized diameter and thickness and a standardized structure (hereinafter referred to as a "disk-side holding structure or disk-side holding mechanism") on their periphery for attachment to a machining machine (see Non-Patent Documents 2 and 3). Meanwhile, machining machines also generally have disk holders (dedicated to each machine) into which "standard disks" can be set. While the specific shape of the disk holder and the specific holding mechanism for holding the standard disk vary depending on the machine, "standard disks" typically have a convex or concave portion formed on their periphery as a disk-side holding structure (mechanism) intended for holding the standard disk in the disk holder. Therefore, all standard disks have in common the fact that they have a "standard disk holding mechanism" that can hold the standard disk using (e.g., by fitting or engaging) the disk-side holding structure (mechanism). Although there is not just one type of disc-side holding structure (mechanism), the types are limited, so by providing one or two disc holders on the cutting machine, it is possible to accommodate many "standard discs."

[0006] Because the above-mentioned standard discs have a fairly large diameter, they are sometimes used to make not only complete dentures but also partial dentures and crowns, which has the advantage of allowing multiple dentures and crowns to be made at the same time. Furthermore, CAD software can be designed to avoid already-cut portions so that cutting can be performed on the uncut portions of the standard disc. Methods for reusing the uncut portions (unused portions) of partially used standard discs are also known (see Patent Documents 3 to 5). Specifically, Patent Document 3 describes a method for obtaining object placement data for a dental restoration to be cut using image data of a CAD / CAM disc on which a dental restoration has already been cut, in order to cut a new dental restoration using a CAM device from the uncut portions of the CAD / CAM disc on which a dental restoration has already been cut.

[0007] Furthermore, as a method for reusing a partially used standard disk as described above by removing it from the device and then reattaching it without causing misalignment, Patent Document 4 describes a method of providing a positioning notch in a standard disk, which is "a dental CAD / CAM workpiece that is cylindrical, the top and bottom surfaces of which are parallel to each other and perpendicular to the side surfaces, and has at least two recesses on the circumference of the cylinder, the recesses being parallel to the top and bottom surfaces in the height direction from the top and bottom surfaces of the cylinder and extending from the side surfaces of the cylinder in the central axis direction in the shape of a concentric cylinder of the cylinder, the recesses consisting of flat surfaces parallel to the top and bottom surfaces and curved surfaces of the concentric cylinder of the cylinder, the flat surfaces of the recesses intersecting with the curved surfaces at right angles," and providing a structure that fits into the notch in a holder that holds the standard disk and attaches it to the cutting process. Furthermore, as a method for removing a partially used standard disk from the device and then attaching it to another cutting device to reuse it as described above, Patent Document 5 describes a "method for arranging shape data of a dental prosthesis, comprising the steps of: attaching the workpiece to a holder that can be attached to a cutting machine and whose attachment direction to the cutting machine is physically defined; photographing the shape of the workpiece with an imaging device; and acquiring shape data of the workpiece; and arranging the shape data of the desired dental prosthesis at any position within the shape data of the workpiece." [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-249297 [Patent Document 2] Patent application No. 61-220646 [Patent Document 3] Japanese Patent Application Publication No. 2018-171312 [Patent Document 4] Patent No. 6344808 [Patent Document 5] Patent Publication No. 2020-137956 [Non-patent literature]

[0009] [Non-Patent Document 1] Kenji Fueki et al., "Clinical Application of Partial Dentures Made of Thermoplastic Resin (Non-Metal Clasp Dentures)," Journal of the Japanese Society of Prosthodontics, Vol. 4, pp. 387-408, 2013 [Non-patent document 2] YAMAKIN, KZR-CAD Denture PC & Probi PC Product Brochure, [Retrieved August 9, 2024], Internet <URL: https: / / www.yamakin-gold.co.jp / technical_support / webrequest / pdf / kzr-cad_pc.pdf> [Non-patent document 3] Zilkonzahn, Millable materials, [Retrieved August 9, 2024], Internet <URL: https: / / zirkonzahn.com / en / products / millable-materials> Summary of the Invention [Problem to be solved by the invention]

[0010] As mentioned above, by using polyurethane resin, it is possible to produce denture bases with favorable mechanical properties. However, when producing denture bases using thermoplastic polyurethane resin, injection molding is the only method used, and CAD / CAM systems have not been used due to the poor machinability of the resin.

[0011] Therefore, the first object of the present invention is to provide a mill blank for dental cutting and a method for manufacturing the same, which can be used to produce denture bases made of polyurethane resin with good physical properties using a CAD / CAM system.

[0012] A second object of the present invention is to provide a dental cutting mill blank that, when a mill blank that has been partially used and removed from the device is to be reused by attaching it to the same or a different device, can create NC data (or tool path) using CAM based on new dental prosthesis cutting shape data designed using shape data from an existing dental restoration, and can then use the disk holder dedicated to the cutting machine as is to cut a new dental prosthesis without processing the disk holder. [Means for solving the problem]

[0013] The present invention solves the above-mentioned problems, and a first aspect of the present invention is a dental cutting mill blank having a cutting portion made of a polyurethane resin molded body, The polyurethane resin is prepared by mixing a polyol component (I) consisting of at least one polyol compound and a diisocyanate component (II) consisting of at least one diisocyanate compound, (1) The total number of hydroxyl groups (—OH) contained in the polyol component (I): N OH {=Σ(M (n) ×N OH(n) )} the total number of isocyanate groups (—N═C═O) contained in the diisocyanate component (II): N NCO {=Σ(M (m) ×N NCO(m) )} ratio:N NCO / N OH The condition is that the value is between 0.9 and 1.1. (2) Regarding the polyol component (I) used in the polyaddition reaction, the number of types of polyol compounds constituting the component is defined as n, and the number of moles of each type is defined as M (n) and the number of hydroxyl groups in one molecule is N OH(n) With respect to the diisocyanate component (II) used in the polyaddition reaction, the number of types of diisocyanate compounds constituting the component is defined as m, and the number of moles of each type is defined as M (m) The number of isocyanate groups in one molecule: 2 is N NCO(m) When Formula: NCP ={Σ(M (n) ×N OH(n) )+Σ(M (m) ×N NCO(m) )} / (ΣM (n) +ΣM (m) ) The average number of crosslinking points in the polyurethane resin is represented by N CP is 2.0 to 3.0, and (3) Regarding the polyol component (I) used in the polyaddition reaction, the number of types of polyol compounds constituting the component is defined as n, and the number of moles of each type is defined as M (n) In all combinations of selecting two hydroxyl groups from all hydroxyl groups contained in one molecule, the number of atoms constituting the main chain among the divalent organic groups intervening between the two hydroxyl groups selected in each combination is calculated and added up, and the sum is defined as the number of combinations {where α is the number of hydroxyl groups contained in one molecule}. α The average inter-OH distance of various polyol compounds is defined as the value divided by {C2=α·(α-1) / 2}. OH(n) year, Regarding the diisocyanate component (II) used in the polyaddition reaction, the number of types of diisocyanate compounds constituting the component is defined as m, and the number of moles of each type is defined as M (m) The average NCO distance of various diisocyanate compounds is defined as the number of atoms in the divalent organic group that has the smallest number of atoms constituting the main chain between two isocyanate groups contained in one molecule, and is defined as d NCO(m) When Formula: D = {Σ(M (n) ×d OH(n) )+Σ(M (m) ×d NCO(m) )} / (ΣM (n) +ΣM (m) ) The distance between urethane groups is expressed as: D is 5 to 9. The dental mill blank is characterized in that the polyurethane resin is obtained by polyaddition so as to satisfy all of the above.

[0014] In the above-described dental cutting mill blank (hereinafter also referred to as "the mill blank of the present invention"), the polyol component (I) is represented by the following general formula (1-a):

[0015] [ka]

[0016] In the formula, L is a hydrogen atom, a methyl group, or an ethyl group; a, which represents the number of methylene units, is an integer of 0 to 3, and multiple a's present in a molecule may be different from each other; R is a simple bond or a group represented by the following formula:

[0017] [ka]

[0018] (In the formula, x is an integer of 2 to 4, r is an integer of 1 to 6, R1 is a hydrogen atom or a methyl group, and multiple R1s may be different from each other.) It is a divalent group represented by the following formula: and 5 to 25 mol % of a diol compound containing a radical polymerizable group in the molecule.

[0019] It is also preferable to use a cutting machine equipped with a disk holder capable of holding a "standard disk," which is a cylindrical or disc-shaped mill block having a predetermined diameter and thickness and having a convex or concave portion formed on its outer periphery, to produce a mill block having an outer shape that is a standard disk used in CAD / CAM systems, and to provide a marker for confirming the mill blank installation position (hereinafter also referred to as a "confirmation marker") in the area near the outer periphery of its upper surface.

[0020] A second aspect of the present invention is a method for producing a mill blank of the present invention, comprising: As a manufacturing process of the machined portion, a raw material composition preparation step of preparing a raw material composition containing a mixture of a polyol component (I) comprising a polyol compound and a diisocyanate component (II) comprising a diisocyanate compound, the mixture satisfying all of the conditions (1) to (3) above; and a polyaddition step of casting the raw material composition and then carrying out a polyaddition reaction to obtain a polyurethane resin molded product; The method for manufacturing a mill blank for dental cutting is characterized by comprising the steps of:

[0021] In the production method of the above embodiment (hereinafter also referred to as "the production method of the present invention"), in the raw material composition preparation step, the polyol component (I) is a polyol represented by the following general formulas (1-a) and (1-b):

[0022] [ka]

[0023] In the formula, L is a hydrogen atom, a methyl group, or an ethyl group, and when a plurality of Ls are present in a molecule, the plurality of Ls may be different from each other; a, which represents the number of methylene units, is an integer of 0 to 3, and the plurality of as present in a molecule may be different from each other; R is a simple bond or a group represented by the following formula:

[0024] [ka]

[0025] (In the formula, x is an integer of 2 to 4, y is an integer of 2 to 6, r is an integer of 1 to 6, R1 is a hydrogen atom or a methyl group, and multiple R1s may be different from each other.) It is a divalent group represented by the following formula: "Polyol compounds having 3 or 4 hydroxyl groups in the molecule" represented by the formula: The following general formula (1-c)

[0026] [ka]

[0027] In the formula, b is an integer of 3 to 5, R has the same meaning as R in the general formulae (1-a) and (1-b), and X is a group represented by the following formula:

[0028] [ka]

[0029] (However, R 11 is an alkyl group having 1 to 3 carbon atoms. When b is 4, at least one of X is not a hydrogen atom, and when b is 5, both of X are not hydrogen atoms, and multiple Xs may be different from each other.} "Polyol compound having 3 to 5 hydroxyl groups in the molecule" A specific polyol compound (I) comprising at least one compound selected from the group consisting of s It is preferable to use a material containing 40 to 100 mol % of

[0030] Furthermore, in the above-mentioned preferred embodiment, the polyol component (I) is the specific polyol compound (I) consisting of at least one compound selected from "polyol compounds having three hydroxyl groups in the molecule" represented by the general formula (1-a). s It is preferable to use a composition comprising 75 to 95 mol % of a diol compound having a radical polymerizable group in the molecule and 5 to 25 mol % of a diol compound having a radical polymerizable group in the molecule. [Effects of the Invention]

[0031] According to the present invention, there are provided a mill blank for dental cutting that can be used to produce a denture base made of polyurethane resin having good physical properties using a CAD / CAM system, and a method for producing the same. [Brief explanation of the drawings]

[0032] [Figure 1]This figure shows a plan view (a-1) and a side view (a-2) of a typical standard disk 1a having a convex portion on the outer periphery, and a plan view (b-1) and a side view (b-2) of a typical standard disk 1b having a concave portion on the outer periphery. [Figure 2] This figure shows a schematic front view (a-1), side view and cross-sectional view (a-2) of a full-periphery compatible disc holder for holding the standard disc 1a shown in Figure 1, and a schematic cross-sectional view (a-3) of the disc holder when the standard disc 1a is held therein; a schematic front view (b) of a semi-periphery compatible disc holder for holding the standard disc 1a; and a schematic front view (c-1) of a full-periphery compatible disc holder for holding the standard disc 1b shown in Figure 1, and a schematic cross-sectional view (c-2) of the disc holder when the standard disc 1b is held therein. [Figure 3] The figures are top and side views of a preferred embodiment of the mill blank of the present invention, with the left-hand figure (A) showing an embodiment having three convex confirmation markers and the right-hand figure (B) showing an embodiment having three concave placement confirmation markers. DETAILED DESCRIPTION OF THE INVENTION

[0033] As mentioned above, polyurethane resins used as denture base materials are thermoplastic, and therefore, when cut, the resin itself melts due to the heat generated during cutting, which can easily cause problems such as seizure on the cutting bar and poor accuracy of the cut product. Therefore, despite its excellent physical properties, polyurethane resins have rarely been used as cutting materials. The present inventors conducted research, thinking that introducing crosslinks into polyurethane resins to make them thermosetting could improve their cutting properties. As a result, they found that, although the introduction of crosslinks could improve cutting properties, there were problems with adhesion to lining materials, etc. Therefore, the inventors focused on the relationship between the crosslinking state of polyurethane resins and adhesiveness and conducted various studies. As a result, they found that if the number of functional groups in the raw material polyol is reduced to significantly lower the chemical crosslink density, not only is sufficient adhesiveness not obtained, but machinability also deteriorates; that if the distance between OH groups in the raw material polyol or the distance between NCO groups in the raw material diisocyanate is changed to vary the physical crosslinking state (by hydrogen bonding of hard segments, etc.), the controlled adhesiveness can be improved; and that if the raw material polyol and raw material diisocyanate are polyadded so as to reduce chemical crosslinking and increase physical crosslinking while satisfying all of the above conditions (1) to (3), both adhesiveness and machinability can be achieved, which led to the completion of the present invention.

[0034] The mechanism by which both machinability and adhesiveness are achieved is not entirely clear, but the present inventors speculate as follows: In other words, in the polyurethane obtained by polyaddition so as to satisfy all of the above conditions (1) to (3), chemical crosslinks and physical crosslinks coexist, resulting in an appropriate crosslinking state that can prevent sticking to the cutting bar and does not inhibit the impregnation of polymerizable monomer components in the backing layer material, etc., and thus makes it possible to achieve both machinability and adhesiveness.

[0035] The mill blank of the present invention and the manufacturing method of the present invention will be described in detail below. In this specification, unless otherwise specified, the notation "x to y" using the numerical values ​​x and y means "greater than or equal to x and less than or equal to y." In such notation, when a unit is assigned only to the numerical value y, the unit also applies to the numerical value x. Furthermore, in this specification, the term "(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."

[0036] 1. Mill Blank of the Present Invention The mill blank of the present invention is a dental mill blank for cutting, having a cutting part made of a polyurethane resin molded body, characterized in that the polyurethane resin has a specific crosslinked structure in which chemical crosslinks and physical crosslinks coexist. Since it is practically impossible to identify the crosslinked structure by analysis, in the present invention, it is specified as a manufacturing condition of the polyurethane resin.

[0037] That is, the polyurethane resin constituting the cuttable portion of the mill blank of the present invention (hereinafter also referred to as "the polyurethane") is a polyurethane resin obtained by polyaddition reaction of a polyol component (I) consisting of at least one polyol compound with a diisocyanate component (II) consisting of at least one diisocyanate compound, in such a manner as to satisfy all of the following conditions (1) to (3):

[0038] Condition (1): The total number of hydroxyl groups (—OH) contained in the polyol component (I): N OH {=Σ(M (n) ×N OH(n) )} the total number of isocyanate groups (—N═C═O) contained in the diisocyanate component (II): N NCO {=Σ(M (m) ×N NCO(m) )} ratio:N NCO / N OH should be 0.9 to 1.1. Condition (2) Regarding the polyol component (I) used in the polyaddition reaction, the number of types of polyol compounds constituting the component is n, and the number of moles of each type is M (n) and the number of hydroxyl groups in one molecule is N OH(n) With respect to the diisocyanate component (II) used in the polyaddition reaction, the number of types of diisocyanate compounds constituting the component is defined as m, and the number of moles of each type is defined as M (m) The number of isocyanate groups in one molecule: 2 is N NCO(m) When Formula: N CP ={Σ(M (n) ×N OH(n) )+Σ(M (m) ×N NCO(m) )} / (ΣM (n) +ΣM (m) ) The average number of crosslinking points in the polyurethane resin is represented by N CP will be 2.0 to 3.0. Condition (3) Regarding the polyol component (I) used in the polyaddition reaction, the number of types of polyol compounds constituting the component is n, and the number of moles of each type is M (n) In all combinations of selecting two hydroxyl groups from all hydroxyl groups contained in one molecule, the number of atoms constituting the main chain among the divalent organic groups intervening between the two hydroxyl groups selected in each combination is calculated and added up, and the sum is defined as the number of combinations {where α is the number of hydroxyl groups contained in one molecule}. α The average inter-OH distance of various polyol compounds is defined as the value divided by {C2=α·(α-1) / 2}. OH(n) year, Regarding the diisocyanate component (II) used in the polyaddition reaction, the number of types of diisocyanate compounds constituting the component is defined as m, and the number of moles of each type is defined as M (m) The average NCO distance of various diisocyanate compounds is defined as the number of atoms in the divalent organic group that has the smallest number of atoms constituting the main chain between two isocyanate groups contained in one molecule, and is defined as d NCO(m) When Formula: D = {Σ(M (n) ×d OH(n) )+Σ(M (m) ×d NCO(m) )} / (ΣM (n) +ΣM (m) ) The distance between urethane groups: D is 5 to 9.

[0039] The condition (1) is a condition for the polyol component (I) and the diisocyanate component (II) to undergo a stoichiometric polyaddition reaction in the correct amount to form a polyurethane resin, and N NCO / N OH Ideally, it is set to 1.0, but if it is within ±0.1, preferably within ±0.05, there is no problem even if unreacted compounds remain.

[0040] The above conditions (2) and (3) define the crosslinking state of the polyurethane resin (a state in which chemical crosslinking and physical crosslinking are mixed), with condition (2) defining the state of chemical crosslinking and condition (3) defining the state of physical crosslinking.

[0041] First, to explain the condition (2), chemical crosslinking is introduced by using a polyol compound having three or more hydroxyl groups in one molecule. When a high molecular weight polyurethane is obtained by polyaddition of 1 mol of polyol component (I) with an amount of diisocyanate component (II) that provides a stoichiometrically balanced amount of isocyanate groups with the amount of hydroxyl groups in the polyol, chemical crosslinking is introduced into the polyurethane when an amount (number) of urethane bonds {-NHC(=O)O-} exceeding 2 mol is formed (since the hydroxyl groups or isocyanate groups at both ends can be ignored). Average number of crosslinking points: N CP is an index of this, and is a compound obtained by mixing a polyol component (I) consisting of only a diol compound and a diisocyanate component (II) with N NCO / N OH In the case of polyurethanes consisting of chain molecules (without chemical crosslinks) obtained by polyaddition so that N = 1.0, CP = 2, and when chemical crosslinks are introduced, the value exceeds 2, and the larger this value is, the greater the amount of chemical crosslinks introduced.

[0042] For example, N OH = 3 glycerol tripropoxylate (GTP) and N NCO = 2 xylylene diisocyanate (XDI) NCO / N OH When polyaddition is carried out so that N = 1.0, 3 moles of XDI are used for 2 moles of GTP. Therefore, the average number of crosslinking points in the polyurethane obtained by polyaddition is N CP =(3×2+2×3) / (2+3)=2.4.

[0043] N when forming this polyurethane CP The value may be 2.0 to 3.0, but is preferably 2.3 to 2.6.

[0044] Next, regarding condition (3), physical crosslinks are formed by hydrogen bonding between urethane bonds that form hard segments, but the state of their formation is affected by the chain length between the urethane bonds. If the chain length is too short, chemical crosslink formation becomes difficult and reactivity is limited, while if the chain length is too long, aggregation of the urethane bonds is unlikely to occur, making it difficult to form physical crosslinks. The distance between urethane groups: D represents the average chain length.

[0045] For example, when polyaddition of 2 mol of GTP and 3 mol of XDI is carried out as above, there are 3 C2 = 3 × 2 / 2 = 3 distances between OH groups in GTP, and the distances between the OH groups are 8, 8, and 9, so d OH On the other hand, the d of XDI is calculated as 8.3. NCO is 5.0, the distance between urethane groups is D = {(2 × 8.3) + (3 × 5.0)} / (2 + 3) = 6.32.

[0046] When forming the present polyurethane, D may be 5-9, but is preferably 5-7.

[0047] The fact that this polyurethane has a chemically crosslinked structure can also be confirmed by the fact that it does not have a glass transition point (Tg) within a temperature range of at least 100°C or less.

[0048] Here, the glass transition point (Tg) is a parameter that represents the thermal properties of a polymer, and the polymer transitions from a flexible structure like a rubber elastic body to a hard elastic body like glass at the Tg. The glass transition point is generally measured using a differential scanning calorimeter (DSC). In the present invention, a resin molded body to be measured is heated from 20°C to 100°C at a heating rate of 10°C / min in a nitrogen atmosphere using DSC, and then cooled. From the point where the temperature reaches 20°C, the temperature is again raised to 100°C at a heating rate of 10°C / min. This process yields a DSC curve for the polymer. The glass transition point is determined as the temperature at which a line extending the low-temperature baseline intersects with a tangent to the stepwise change in the curve obtained when the temperature is again raised.

[0049] Because this polyurethane has a chemically crosslinked structure, when the above measurement is performed, there is no step-like change in temperature within the measurement range of 20 to 100°C. This prevents seizure on the cutting bar and poor accuracy. In addition, deformation or size change of the obtained mill blank is also suppressed, which is advantageous when providing a marker to confirm the installation position of the mill blank for measurement, as described below.

[0050] As described above, the mill blank of the present invention has a cutting portion made of a molded article of polyurethane resin having a specific crosslinked structure, but this crosslinked structure is specified by the manufacturing method, and it can also be said that the mill blank of the present invention is manufactured by the manufacturing method of the present invention described below.

[0051] 2. Manufacturing method of the present invention The manufacturing method of the present invention is a method for manufacturing the mill blank of the present invention, and is characterized in that it includes, as a manufacturing process for the cuttable portion, a raw material composition preparation process for preparing a raw material composition containing a mixture of a polyol component (I) made of a polyol compound and a diisocyanate component (II) made of a diisocyanate compound, the mixture satisfying all of the conditions (1) to (3) above; and a polyaddition process for casting the raw material composition and then carrying out a polyaddition reaction to obtain a polyurethane resin molded product.

[0052] Each component used as a raw material and each step will be described below.

[0053] <Polyol component (I)> The polyol component (I) undergoes a polyaddition reaction with the diisocyanate component (II) to form a polyurethane resin in which units in which both components are bonded by urethane bonds are linked. The polyol component (I) may be any polyol compound that satisfies the above conditions (2) and (3). However, because it is easy to satisfy these conditions, a specific polyol compound (I) consisting of at least one compound selected from the group consisting of "polyol compounds having 3 or 4 hydroxyl groups in the molecule" represented by the following general formulas (1-a) and (1-b) and "polyol compounds having 3 to 5 hydroxyl groups in the molecule" represented by the following general formula (1-c) is preferred. s ) is preferably contained in an amount of 40 to 100 mol %, and the specific polyol compound (I) is composed of at least one compound selected from "polyol compounds having three hydroxyl groups in the molecule" represented by the following general formula (1-a): s It is particularly preferable to use a composition comprising 75 to 95 mol % of a diol compound having a radical polymerizable group in the molecule and 5 to 25 mol % of a diol compound having a radical polymerizable group in the molecule.

[0054] [ka]

[0055] In the above formulas (1-a) and (1-b), L represents a hydrogen atom, a methyl group, or an ethyl group. Furthermore, a, which represents the number of methylene units, is an integer of 0 to 3, and multiple a's present in a molecule may be different from each other. Furthermore, R represents a simple bond or a divalent group represented by the following formula:

[0056] [ka]

[0057] In the above formula, x represents an integer of 2 to 4, y represents an integer of 2 to 6, and r represents an integer of 1 to 6. R1 represents a hydrogen atom or a methyl group, and multiple R1s may be different from each other.

[0058] In the general formula (1-c), b represents an integer of 3 to 5, and R has the same meaning as R in the general formulas (1-a) and (1-b). X represents any atom or group represented by the following formula, and when b is 4, at least one of X is not a hydrogen atom, and when b is 5, both of X are not hydrogen atoms, and multiple Xs may be different from each other.

[0059] [ka]

[0060] In addition, R in the above formula 11 represents an alkyl group having 1 to 3 carbon atoms.

[0061] Examples of the compound represented by the formula (1-a) include glycerin, trimethylolpropane, glycerol tripropoxylate, and trimethylolpropane ethoxylate. Examples of the compound represented by the formula (1-b) include pentaerythritol, pentaerythritol tetrapropoxylate, and ε-caprolactone-modified pentaerythritol. Examples of the compound represented by the formula (1-c) include diglycerin, diglycerin monoacetyl, polyoxyethylene polyglyceryl ether, and triglycerol di(meth)acrylate.

[0062] The specific polyol compound (I) that can be particularly suitably used in the present invention s Specific examples of the alkyl acrylates include glycerol tripropoxylate, trimethylolpropane ethoxylate, pentaerythritol tetrapropoxylate, and triglycerol di(meth)acrylate.

[0063] The specific polyol compound (I) constituting the polyol component (I) s As the polyol compound other than the specific polyol compound (I s Any compound other than the above having two or more hydroxyl groups in the molecule can be used without particular limitation. Diol compounds having a radical polymerizable group are preferred because they are expected to chemically bond with the backing material, etc., and to improve adhesion. Examples of such diol compounds include trimethylolpropane mono(meth)acrylate, glycerol mono(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether, and acid ((meth)acrylic acid or vinylbenzoic acid) ring-opened products of bisphenol A diglycidyl ether. Among these, it is preferred to use at least one selected from the group consisting of glycerol mono(meth)acrylate and (meth)acrylic acid ring-opened products of bisphenol A diglycidyl ether.

[0064] That is, in the production method of the present invention, the polyol component (I) is a specific polyol compound (I) consisting of at least one compound selected from the group consisting of glycerol tripropoxylate, trimethylolpropane ethoxylate, pentaerythritol tetrapropoxylate, and triglycerol di(meth)acrylate. s and 5 to 25 mol% of a diol compound having a radical polymerizable group, which is made of at least one compound selected from the group consisting of trimethylolpropane mono(meth)acrylate, glycerol mono(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether, and acid ((meth)acrylic acid or vinylbenzoic acid) ring-opening products of bisphenol A diglycidyl ether.

[0065] <Diisocyanate component (II)> The diisocyanate component (II) is a compound having two isocyanate groups per molecule. Examples of compounds that can be suitably used as the diisocyanate component (II) include 1,3-bis(isocyanatomethyl)cyclohexane, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and m-xylylene diisocyanate. These compounds can be used alone or in combination. The diisocyanate component (II) preferably contains m-xylylene diisocyanate.

[0066] <Other ingredients> The raw material composition may contain, within the limits that do not impair the effects of the present invention, a monool having a radical polymerizable group, a monoisocyanate having a radical polymerizable group, a catalyst that promotes the polyaddition of polyurethane (hereinafter also referred to as a "urethane polymerization catalyst"), a pigment, a fluorescent agent, an ultraviolet absorber, an antioxidant, a pigment, an antibacterial material, an X-ray contrast agent, and the like, and the amounts added may be determined appropriately depending on the purpose.

[0067] Examples of monomolecules having a radical polymerizable group that can be used include hydroxyalkyl(meth)acrylates (hydroxyethyl(meth)acrylate, etc.), hydroxyalkylene glycol(meth)acrylate, etc., and specific examples of monoisocyanates having a radical polymerizable group that can be used include isocyanatoethyl(meth)acrylate, isocyanatoethyloxyethyloxy(meth)acrylate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate, etc.

[0068] Suitable urethane polymerization catalysts include tin catalysts such as dibutyltin diacetate and dibutyltin dilaurate, amine catalysts such as triethylenediamine, and zirconium acetylacetonate.

[0069] <Raw material composition preparation process> The raw material composition that serves as the raw material for the polyurethane can be produced by determining the composition and amount of the polyol component (I) and the diisocyanate component (II) so as to satisfy the above conditions (1) to (3), and then mixing the required amounts of each component.

[0070] In this case, the composition and amount of the polyol component (I) and the diisocyanate component (II) are determined by first determining the composition of the diisocyanate component (II), and then determining the number of types of diisocyanate compounds: m, the number of moles of each type: M, (m) Average NCO distance of various diisocyanate compounds: d NCO(m) It is preferable to determine the composition of the polyol component (I) after determining the above. s ) and determine the compound that is the main component of the compound, and the number of hydroxyl groups in that compound: N OH and the average inter-OH distance d OH(n) After checking the above, other specific polyol compounds (I s ) and specific polyol compounds (I s ) for polyol compounds other than these N OH and d OH(n)It is preferable to determine the composition so as to satisfy the above conditions (2) and (3) by checking the above. After determining the composition of the polyol component (I) and the diisocyanate component (II) in this manner, the amounts of both components to be used can be determined so as to satisfy the above condition (1).

[0071] Regarding the polyol component (I), from the viewpoint of being able to obtain a dental cutting mill blank with excellent adhesiveness, it is preferable that the polyol component (I) contains two or more types of polyols and that the maximum d OH(n) and the minimum d OH(n) The difference between these is preferably 10 to 20, more preferably 10 to 15, and most preferably 12 to 15.

[0072] The method for mixing the components is not particularly limited, and a method of stirring and mixing using a magnetic stirrer, stirring blades, centrifugal mixer, or the like is preferably used.

[0073] During mixing, it is preferable to control the temperature to prevent an unintended reaction. In particular, if the temperature becomes too high, there is a risk of the reaction proceeding too rapidly, so it is preferable to control the temperature to 10 to 40°C, more preferably 10 to 30°C.

[0074] In this step, a solvent or the like may be used to dissolve the raw material components. However, because a removal step is required and residual solvents can adversely affect the physical properties of the polyurethane, it is preferable not to use a solvent and to make either the polyol component (I) or the diisocyanate component (II) liquid, and it is more preferable to make both of them liquid.

[0075] The mixture thus prepared is preferably subjected to a degassing treatment before polyaddition to remove any bubbles contained therein. As a degassing method, a known method can be used, such as pressure degassing, vacuum degassing, centrifugal degassing, etc.

[0076] In the subsequent polyaddition step, a urethane polymerization catalyst may be blended into the raw material composition to efficiently promote polyaddition. Furthermore, when adding optional components according to the purpose, it is preferable to mix them in this mixing step. At this time, it is preferable to mix components that require a long-term dispersion treatment with the polyol component (I) in advance.

[0077] The ratio of the amounts of the components (I) and (II) in the mixture may be such that the condition (1) is satisfied.

[0078] <Heavy addition process> The raw material composition obtained in the mixing step is cast into a mold and subjected to a polyaddition reaction to form polyurethane, thereby obtaining a mill blank for dental cutting work. The method for producing the mill blank for dental cutting work of the present invention by subjecting the raw material composition to a polyaddition reaction is not particularly limited.

[0079] The mold used for casting is not particularly limited, and a rectangular pillar, a cylinder, a square plate, or a disk-like mold may be used as appropriate depending on the shape envisioned for each product form. The size of the mold may be such that the product after polyaddition will have the envisioned shape as is, taking into account factors such as shrinkage, or it may be larger to allow for processing after polyaddition. The material of the mold is also not particularly limited, but it is preferable to use a mold made of a resin such as polyethylene or polypropylene from the viewpoints of suppressing side reactions and demolding ease.

[0080] The method for injecting the mixture into the mold is not particularly limited, and any known method can be used. In order to prevent air bubbles from being mixed in during mixing, pressure casting or vacuum casting is preferred.

[0081] The cast mixture is heated to initiate a polyaddition reaction and cure. Because heat is generated during polymerization, it is preferable to control the temperature (curing temperature) during heating. Specifically, in order to ensure that polymerization and curing proceed at an industrially acceptable rate, prevent distortion or cracks in the cured product due to rapid reaction progress, and minimize monomer degradation, it is preferable to control the temperature so that it does not exceed 120°C, and more preferably below 100°C.

[0082] When the polyaddition reaction is carried out by heating, it is preferable to apply pressure to prevent voids due to bubbles from being formed in the cured product. There are no limitations on the method of applying pressure, and mechanical pressure or pressure using a gas such as nitrogen may be used.

[0083] After being removed from the mold, the hardened body obtained by the polyaddition reaction may be subjected to post-treatments or processing such as heat treatment to relieve residual stress, cutting to modify the shape to a required shape or a more user-friendly shape, polishing, etc., as necessary. A dental mill blank for cutting is made by attaching a fixture such as a pin for holding it in a CAD / CAM device or by processing it into a disk shape.

[0084] The dental cutting mill blank of the present invention can be used for resin materials for dental crowns, resin materials for dental bases, orthodontic materials, and mouthguard materials, and is particularly suitable for use in resin materials for dental bases.

[0085] 3. Shape of the mill blank of the present invention As mentioned above, "standard discs" are widely used commercially in dental cutting mill blanks, and cutting machines are generally equipped with disc holders (dedicated to each cutting machine) into which such "standard discs" can be set. Therefore, the mill blank of the present invention is preferably provided as a "standard disc." Furthermore, when the dental cutting mill blank of the present invention is a standard disc, it is particularly preferable that a marker for confirming the mill blank mounting position (confirmation marker) is provided in the region of the upper surface near the outer periphery.

[0086] The standard disc, the disc holder for the standard disc (also simply referred to as the disc holder), and the standard disc with a confirmation marker will be described in detail below with reference to the drawings.

[0087] <Standard disk> As shown in Figure 1, a "standard disk" 1 is a disk-shaped (disk-like) dental mill block made of denture base material and having a predetermined diameter and thickness used for making (full) denture bases. The disk body has a disk-like (disk-like: low-height cylindrical) shape with a predetermined diameter and thickness, and a disk-side holding structure (mechanism) 3 consisting of a convex portion 3a or a concave portion 3b is formed on the outer periphery of the disk body. Here, for example, the predetermined diameter in Non-Patent Documents 1 and 2 is 94 to 95 mm, and the predetermined thickness is approximately 15 to 40 mm, such as 16 mm or 35 mm. The predetermined diameter refers to the diameter of the circular top and bottom surfaces of the disk (low-height cylindrical) of the disk body.

[0088] A plan view and a side view of a typical standard disk 1a having a convex disk-side holding mechanism (mechanism) are shown in Figure 1 (a-1) and (a-2). The (disk-side) holding mechanism 3 of the standard disk 1a is made up of a continuous strip-shaped convex portion 3a formed in the center of the height direction of the outer periphery 2 (side surface) of the disk body, which is the disk itself, and which has a predetermined width (corresponding to the length in the height direction) and thickness (corresponding to the difference between the radius of the outer periphery of the convex portion and the radius of the outer periphery of the disk).

[0089] Next, Figures 1(b-1) and (b-2) show a plan view and a side view of a typical standard disk 1b having a concave (disk-side) holding mechanism 3. The standard disk 1b has a disk-like (low-height cylinder) disk body with a plurality of holding mechanisms formed on the outer periphery 2 (side) of the disk body, which is cut out from the top (and / or bottom) downward (and / or upward) (the cutouts are columnar, frustum-shaped, or cone-shaped). In the figure, three columnar recesses 3b (six in total, top and bottom) are formed at equal intervals on the top and bottom sides, each roughly semicircular and with a height of about 1 / 4 the thickness of the standard disk.

[0090] <Disc holder> As shown in Figure 2, the disc holder 4 is a fixture or jig used to set a "standard disc" 1, which is standardly equipped on cutting machines used to make complete dentures using a CAD / CAM system. Although the specific form may differ depending on the device, they all have in common the fact that they have a standard disc holding mechanism that can hold the standard disc 1 using the disc side holding structure (mechanism) 3 (for example, by fitting or engaging), and more specifically, that they have a disc holding frame 5 equipped with a standard disc holding mechanism 6 consisting of a recess 6a or a protrusion 6b that fits or engages with the protrusion 3a or recess 3b that is the disc side holding structure (mechanism) 3.

[0091] The disc holder 4 corresponding to the standard disc 1a has a standard disc holding mechanism 6 consisting of a recess 6a that fits or engages with the protrusion 3a, which is the disc-side holding structure (mechanism) 3. Fig. 2(a-1) shows a plan view of the disc holder 4a having such a holding mechanism, Fig. 2(a-2) shows a side view and a cross-sectional view of Fig. 2(a-1), and Fig. 2(a-3) shows the disc holder 4a holding the standard disc 1a. The disc holder 4a has an upper fixing plate 7 and a lower fixing plate 8, each of which has a circular hole (holding hole) formed in the center with a diameter corresponding to the diameter of the disc body of the standard disc 1a, and a cylindrical wall member 9 for forming the recess 6a that forms the standard disc holding mechanism 6. The disc holder 4a has a basic structure in which the upper fixing plate 7 and the lower fixing plate 8 are arranged parallel to each other across the cylindrical wall member 9 so that the centers of the holding holes are aligned, and can be fixed using screws or the like. When these plates are fixed, they form the disc holding frame 5.

[0092] The cylindrical wall member 9 is a cylindrical wall that corresponds to the outer periphery of the protrusion 3a of the standard disc 1a, and is positioned so that its center coincides with the center of the holding hole, and a recess 6a is formed by the inner circumferential surface of the cylindrical wall member 9, the lower surface of the upper fixing plate 7 (which protrudes like a visor into the disc holding frame 5), and the upper surface of the lower fixing plate 8. Then, as shown in Figure 2(a-3), the protrusion 3a, which is the (disc-side) holding mechanism 3, is housed in the recess 6a, and the standard disc 1a is held by the disc holder 4a.

[0093] When the standard disc 1a is to be held and fixed in the disc holder 4a, the upper fixing plate 7 is removed, and the standard disc 1a is placed on the upper surface of the lower fixing plate 8 with the lower surface of the convex portion 3a in contact with the upper surface of the lower fixing plate 8, and then the upper fixing plate 7 is attached, and the upper fixing plate 7, lower fixing plate 8, and cylindrical wall member 9 are fixed (for example, with screws). Although not shown, at least one of the upper fixing plate 7 and the lower fixing plate 8 may be composed of two or more parts that can rotate or slide, and a spring mechanism or the like may be used to temporarily widen the holding hole and return to its original position, thereby allowing the standard disc to be attached or detached. Furthermore, although not shown, the disc holder 4 has a mechanism that allows it to be detachably attached to a cutting machine in accordance with the structure of the cutting machine.

[0094] The disc holder 4a is an example of a disc holder compatible with the standard disc 1a, and although the upper and lower fixing plates 7 and 8 are shown in the figure as having the same rectangular outer shape, they may be different shapes, or may have a circular or polygonal outer shape, for example. The cylindrical wall member 9 may be formed by cutting a cylindrical wall member vertically along its circumference and dividing it into multiple pieces, each with an arc-shaped cross section, and arranging the pieces at intervals. Furthermore, the disc holder 4a may be divided into two pieces, as in the disc holder 4b shown in Figure 2(b).

[0095] The disc holder 4 corresponding to the standard disc 1b has a standard disc holding mechanism 6 consisting of a protrusion 6b that fits or engages with the recess 3b, which is the disc-side holding structure (mechanism) 3. Fig. 2(c-1) shows a disc holder 4c having such a holding mechanism, and Fig. 2(c-2) shows the state in which the disc holder 4c holds a standard disc 1b.

[0096] When the standard disc 1b is to be held and fixed in the disc holder 4c, the upper fixing plate 7 is removed, and the standard disc 1b is placed in the holding hole so that its underside is flush with the underside of the lower fixing plate, and then the three convex parts 6b attached to the lower fixing plate 8 are inserted into the three concave parts 3b formed on the underside (bottom) of the standard disc 1b, and then the three convex parts 6b attached to the upper fixing plate 7 are inserted into the three concave parts 3b formed on the top side of the standard disc 1b, thereby fixing (for example, with screws) the upper fixing plate 7, the lower fixing plate 8, and the cylindrical wall member 9. Also, the convex parts 6b attached to the upper fixing plate and the lower fixing plate may be slid and fixed with screws, for example.

[0097] <Cutting using a standard disc> In cutting a standard disk using a CAD / CAM system, data (e.g., shape data in three-dimensional xyz coordinates (hereinafter also referred to as "disk coordinates") with an arbitrarily determined specific point on the standard disk as the origin, hereinafter also referred to as "CAM data") is created on a PC within the standard disk, forming a drawing of the dental prosthesis to be manufactured. Based on this, CAM creates NC data (e.g., position data (hereinafter also referred to as "tool path data") in three-dimensional xyz coordinates (hereinafter also referred to as "machine coordinates") with an arbitrarily determined specific point on the cutting machine as the origin) for controlling the movement of the milling bur of the cutting machine. The milling bur and / or the disk holder holding the standard disk are moved according to the tool path data to perform the cutting process. Since the tool path data is created based on the CAM data when the disk holder holding the standard disk is set in a predetermined position on the cutting machine (hereinafter also referred to as the "set position"), the relative positional relationship between the machine coordinates and the disk coordinates is fixed to the relative positional relationship in the above state.

[0098] When cutting an unused standard disc, the machinable area of ​​the standard disc is a point-symmetric cylindrical shape (thickness smaller than diameter), so misalignment due to the disc's circumferential rotation (hereinafter referred to as "rotational misalignment") is not a problem. Furthermore, since the position of the disc set in the machine coordinate system is assumed to be nearly constant (unchanged from when the CAM data was created), the x- and y-axes do not need to be aligned as long as the origin of the disc coordinate system matches the origin of the disc coordinate system in the CAM data used to create the tool path data. Furthermore, even if planar and / or vertical misalignment (hereinafter referred to as "gap misalignment") occurs due to "play" when the standard disc is held in the disc holder and when the disc holder holding the standard disc is set in the set position, this misalignment is small. Since CAM data is typically created with a reserve space reserved to account for such slight misalignment, the milling burr will not cut off the actual standard disc. Therefore, the disc can be held in the holder or set in the set position without any special considerations, and cutting can begin.

[0099] <Standard disc with confirmation marker and re-cutting process using this> When a standard disk (hereinafter also referred to as a "reused disk") that has been removed from a device using a portion of the standard disk is to be reused by mounting it on the same or a different device, it is necessary to create CAM data (reused CAM data) so that the target dental prosthesis can be cut out from the cutting-machinable area of ​​the reused disk, and then create tool path data (reused tool path data). It is more convenient to use the CAM data (initial CAM data) of a machined product that was previously used in cutting, as described in Patent Document 3, rather than creating the reused CAM data and reused tool path data based on newly acquired video data, as described in Patent Document 5.

[0100] The mill blank of the present invention is preferably a standard disk with a confirmation marker, i.e., a marker for confirming the mill blank mounting position (confirmation marker) in the region near the outer periphery of the top surface of the standard disk, because this allows new dental prostheses to be cut using a disk holder dedicated to the cutting machine as is (without processing the disk holder) based on the reused CAM data created in this way. A method of reuse using a standard disk with a confirmation marker will be described below.

[0101] As described above, when performing the initial cutting process using a standard disk, no special consideration is required. However, when reusing a disk, the cuttable area of ​​the reused disk obtained by cutting the disk during the initial cutting process while allowing for slight gap deviations may deviate from the planned cutting area in the reused CAM data. Therefore, in order to create and use reused CAM data and reused tool path data using the initial CAM data, it is necessary to satisfy the following conditions: during the initial cutting process, the actual cutting position corresponds exactly to the cutting position in the disk coordinates of the initial CAM data, and the shape data of the cuttable area in the disk coordinates of the reused disk matches the reused CAM data.

[0102] Furthermore, when a new cutting process is performed (at the time of reuse), the rotational misalignment and clearance misalignment may cause cutting to be performed outside the intended cutting area, which may result in a dental prosthesis not having the desired shape being obtained. To avoid such problems, it is necessary to align not only the origin of the disk coordinates but also the directions of the x-axis and y-axis for the disk coordinates in the device coordinates of the reused tool path data and the disk coordinates in the device coordinates when the disk is actually set in the device coordinates. To perform more precise correction, it is also necessary to detect any deviation related to the tilt of the xy plane, and if any deviation is detected, to create corrected reused tool path data in which the deviation related to the tilt has been corrected.

[0103] When using a standard disk with a confirmation marker, the initial tool path data created using the initial CAM data incorporates the position information of the confirmation marker, and further, the confirmation marker is formed in an area near the outer edge of the top surface of the standard disk (not covered by the disk holder). Therefore, with an unused disk set in the set position, the position of the confirmation marker can be detected to detect any deviation from the marker position in the initial CAM data. Therefore, the above condition can be satisfied by performing cutting based on the corrected initial tool path data obtained by correcting the initial tool path data using the corrected initial CAM data corrected based on the detected deviation.

[0104] Similarly, with the reused disk set in the set position, the position of the confirmation marker is detected to detect any deviation from the marker position in the reused CAM data, and the reused tool path data is corrected using the reused CAM data corrected based on the detected deviation, and cutting is performed based on the obtained corrected reused tool path data, thereby ensuring that cutting is performed within the cutting area of ​​the reused disk.

[0105] In addition, corrections from initial CAM data to corrected initial CAM data and corrections from reused CAM data to corrected reused CAM data can be made by (1) aligning the origin and the directions of the x- and y-axes of the disk coordinates in the device coordinates of the CAM data before correction with the disk coordinates in the device coordinates when the disk is actually set in the device coordinates, without taking the tilt deviation into consideration, if possible, and (2) aligning the xy plane and then aligning the origin and the directions of the x- and y-axes of the disk coordinates in the device coordinates of the CAM data before correction with the disk coordinates in the device coordinates when the disk is actually set in the device coordinates, if possible.

[0106] As a detector (measuring device) for detecting the position of the confirmation marker, a photographing device such as a camera or a contact sensor such as a touch probe (or milling bur) can be suitably used. Some cutting machines are equipped with such detectors, so in that case, the detector that comes with the machine can be used. Also, if a cutting machine that does not come standard with the above detector is used, a separately prepared detector can be used.

[0107] The confirmation marker may be any marker whose position can be detected with high accuracy visually (image information) or tactilely (contact information), but it is preferable that it has a symmetrical planar or three-dimensional shape with a center, because the central position can be identified with high accuracy from the outer shape. The number of confirmation markers may be one or more, but is preferably one to five. When there are multiple confirmation markers, the shapes of the markers may be different from each other, and numbers or symbols may be written around each marker to distinguish them from each other.

[0108] For reasons of ease of detecting not only rotational misalignment but also misalignment due to tilt of the disc top surface, the number of confirmation markers is the minimum required to identify the plane, at least three, preferably three to five, and most preferably three, and the shape of the confirmation markers is preferably a cone or pyramid-shaped convex or concave portion of the same height, whose apex can be detected with high precision by a contact sensor. In particular, it is preferable that three confirmation markers of this shape are arranged around the periphery of the top surface at a predetermined interval (for example, so as to be the apexes of an isosceles triangle).

[0109] The region near the outer edge on the top surface of a standard disc with a verification marker refers to a band-shaped region along the circumferential direction whose width (radial length) from the outer edge of the top surface toward the center of the top surface is 10 mm or less, and preferably refers to a region whose width is 3.0 to 5.0 mm. 3A and 3B show standard discs 10a and 10b with confirmation markers, which correspond to such preferred embodiments. 10a represents a standard disc with confirmation markers, in which three confirmation markers 10a2, each consisting of a regular square pyramidal convex portion with a side length of 2.0 to 4.0 mm, preferably 2.5 to 3.0 mm, are arranged in an area 10a1 near the outer periphery of the top surface of standard disc 1a shown in FIG. 1A-1, so as to form the vertices of an isosceles triangle with an apex angle of 60°. 10b represents a standard disc with confirmation markers, in which three confirmation markers, each consisting of a regular square pyramidal concave portion, are arranged in an area 10b1 near the outer periphery of the top surface of standard disc 1a. When the confirmation markers are arranged to form the vertices of an isosceles triangle, vertex 1, which forms the vertex angle, can be identified separately from the other two vertices forming the base angles. Therefore, the confirmation marker arranged at vertex 1 can be used as a reference for holding the disc in the disc holder or for making the adjustments. [Example]

[0110] EXAMPLES In the following, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0111] First, all materials used in each example and comparative example will be described below.

[0112] (1) Specific polyol compound (I s ) GTP: glycerol tripropoxylate (molecular weight: 266, number of hydroxyl groups: N OH :3, average OH distance d OH :8.3) PETP: Pentaerythritol tetrapropoxylate (molecular weight: 426, number of hydroxyl groups: N OH :4, average OH distance d OH :10.5) TMP: Trimethylolpropane (molecular weight: 134, number of hydroxyl groups: N OH :3, average OH distance d OH :3.0) TMPE: Trimethylolpropane ethoxylate (molecular weight: 450, number of hydroxyl groups: N OH :3, average OH distance d OH :17.4) TGDM: Triglycerol dimethacrylate (molecular weight: 386, number of hydroxyl groups: N OH :3, average OH distance d OH :6.3).

[0113] (2) Specific polyol compound (I s ) Polyols other than GMA: Glycerol monomethacrylate (molecular weight: 160, number of hydroxyl groups: N OH :2, average OH distance d OH :2.0).

[0114] (3) Diisocyanate component (II) XDI: m-xylylene diisocyanate (molecular weight: 188, number of isocyanate groups N NCO :2, the average distance between NCOs is d NCO :5.0).

[0115] Example 1 6.3 g of GTP, a polyol, and 0.7 g of GLM, another diol, were mixed using a magnetic stirrer, and then 7.5 g of XDI, a diisocyanate, was added and stirred at room temperature for 1 hour. The average number of crosslinking points of the polyurethane produced from these raw materials, N CP The ρ was 2.63, and the distance D between urethane groups was 7.18. After confirming that the mixed solution (raw material composition) was homogeneous, it was filled into a 12 x 15 x 100 (mm) mold and subjected to a polyaddition reaction under nitrogen pressure (0.3 MPa) at 60°C for 24 hours, followed by 80°C for 15 hours, to prepare a polyurethane molded product. The resulting polyurethane molded product was demolded and subjected to the following evaluations.

[0116] (Evaluation of polyurethane molded products) 1. Confirmation of the existence of a glass transition temperature (Tg) The glass transition temperature Tg of the polyurethane resin constituting the obtained polyurethane molded article was evaluated as follows.

[0117] Using a DSC8230 (Rigaku), the temperature was raised from 20°C to 100°C at a rate of 10°C / min under a nitrogen atmosphere, then lowered, and from the 20°C point, the temperature was raised again to 100°C at a rate of 10°C / min, and a DSC curve of the polyurethane component was obtained during this process. Since no step-like change was observed on the obtained DSC curve, it was determined that no Tg was present.

[0118] 2. Evaluation of Adhesion The adhesiveness of the resulting polyurethane molded article was evaluated as follows.

[0119] The resulting polyurethane molded body was cut using a low-speed diamond cutter (Buehler) and then trimmed into a 12 mm x 15 mm x 3 mm rectangular column using P800 waterproof abrasive paper to obtain test specimens. After washing and drying, two layers of double-sided tape with a 3 mm diameter hole were attached to define the adhesion area. A wax sheet with an 8 mm diameter hole was then attached on top of the tape. The resulting hole was filled with Hikari Liner (Tokuyama Dental), a light-curing, powder-liquid denture base hard lining material mixed at a specified ratio, and pressed against a PET sheet. The specimen was then left in an incubator at 37°C for 5 minutes. The specimen was then exposed to light for 5 minutes using a dental laboratory photopolymerization device (Portalite, Tokuyama Dental). After removing the wax sheet from the resulting specimen, it was immersed in 37°C water for 18 hours. After polishing the Hikari Liner surface of the test specimen, a SUS attachment was attached using Alteco adhesive.

[0120] Five test pieces were mounted on an autograph (Shimadzu Corporation) and subjected to a tensile test under the conditions of an adhesion area of ​​φ3 mm and a tensile speed of 2 mm / min. The results showed that the adhesive had an adhesive stress of 12.7 MPa.

[0121] The test pieces were then inspected visually for any fractures at the adhesive interface. The number of pieces where the Hikari Liner cured body remained on the surface of the polyurethane cured body was counted, and the percentage was evaluated as the adherend fracture rate. The result was an 80% adherend fracture rate.

[0122] 3. Evaluation of bending strength The flexural strength of the resulting polyurethane molded article was evaluated as follows.

[0123] The polyurethane molded body was cut using a low-speed diamond cutter (Buehler) and then polished to a prism shape of 1.2 mm × 4.0 mm × 14.0 mm using P2000 waterproof abrasive paper to obtain a test specimen. The test specimen was mounted on an autograph (Shimadzu Corporation) and subjected to a three-point bending test under the conditions of a support distance of 12.0 mm and a crosshead speed of 1.0 mm / min.

[0124] The bending strength BS was calculated using the following formula (1). Ten test pieces were prepared for each example and comparative example, and the average value was used as the bending strength of the polyurethane molded product. As a result, it was shown that the polyurethane molded product had a bending strength of 171 MPa.

[0125] BS=3PS / 2WB 2 Formula (1) P: bending load at maximum point (N), S: distance between supports (12.0 mm), W: width (measured at approximately 4.0 mm), B: thickness (measured at approximately 1.2 mm) Examples 2 to 10, Comparative Examples 1 to 2 A raw material composition having the composition shown in Table 1 was prepared and subjected to cast polymerization, and other than this, a polyurethane molded article was produced and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0126] Comparative Example 3 Pellets of Biotone (manufactured by Denken High Dental Co., Ltd.), a commercially available polyamide material, were dried at 100°C for 15 hours, then filled into a 30 x 15 x 2 (mm) mold, heated to 300°C, and pressed using a hot press (Imoto Manufacturing Co., Ltd.). After cooling, the mold was released to obtain a cured product. A 15 x 15 x 2 (mm) shape was cut and polished to obtain a test piece. The adhesion was then evaluated using the same procedure as in Example 1. The results are shown in Table 2.

[0127] [Table 1]

[0128] [Table 2] [Explanation of symbols]

[0129] 1 standard disc 1a Standard disk with a convex portion 3a formed on the outer periphery 2 1b Standard disk with recess 3b formed on outer periphery 2 2 Outer circumference of standard disc 3 Disc side holding structure (mechanism) 3a Convex part 3b recess 4 Disc Holder 4a Circular disc holder for holding standard disc 1a 4b Arc-shaped disc holder for holding standard disc 1a 4c Circular disc holder for holding standard disc 1b 5 Disc holder frame 6 Standard disc retention mechanism 6a (fitting or engaging with the protrusion 3a) 6b (fitting or engaging with recess 3b) 7 Upper fixing plate 8 Lower fixing plate 9 Cylindrical members 10a, 10b Standard disc with confirmation marker 10a1, 10b1: Areas near the outer periphery of the upper surface 10a2 Convex marker for checking the mill blank mounting position 10b2 Convex marker for checking the mill blank mounting position

Claims

1. A dental cutting mill blank having a cutting part made of a polyurethane resin molded body, The polyurethane resin is prepared by mixing a polyol component (I) comprising at least one polyol compound and a diisocyanate component (II) comprising at least one diisocyanate compound, (1) The total number of hydroxyl groups (—OH) contained in the polyol component (I): N ＯＨ {=Σ(M （ｎ） ×N ＯＨ（ｎ） ))}, the total number of isocyanate groups (—N═C═O) contained in the diisocyanate component (II): N ＮＣＯ {=Σ(M （ｍ） ×N ＮＣＯ（ｍ） )} ratio: N ＮＣＯ / N ＯＨ is between 0.9 and 1.1, (2) Regarding the polyol component (I) used in the polyaddition reaction, the number of types of polyol compounds constituting the component is defined as n, and the number of moles of each type is defined as M （ｎ） and the number of hydroxyl groups contained in one molecule is N ＯＨ（ｎ） With respect to the diisocyanate component (II) used in the polyaddition reaction, the number of types of diisocyanate compounds constituting the component is m, and the number of moles of each type is M （ｍ） The number of isocyanate groups contained in one molecule: 2 is N ＮＣＯ（ｍ） When Formula: N ＣＰ = {Σ(M （ｎ） × N ＯＨ（ｎ） )+ Σ(M （ｍ） × N ＮＣＯ（ｍ） )} / (ΣM （ｎ） + ΣM （ｍ） ) The average number of crosslinking points in the polyurethane resin represented by: N ＣＰ is between 2.0 and 3.0, and (3) Regarding the polyol component (I) used in the polyaddition reaction, the number of types of polyol compounds constituting the component is defined as n, and the number of moles of each type is defined as M （ｎ） In all combinations in which two hydroxyl groups are selected from all hydroxyl groups contained in one molecule, the number of atoms constituting the main chain is determined for the divalent organic group intervening between the two hydroxyl groups selected in each combination, and the sum of these atoms is calculated and calculated to determine the number of combinations {when the number of hydroxyl groups contained in one molecule is α, α C ２ The average inter-OH distance of various polyol compounds is defined as the value obtained by dividing the average inter-OH distance by d ＯＨ（ｎ） year, Regarding the diisocyanate component (II) used in the polyaddition reaction, the number of types of diisocyanate compounds constituting the component is defined as m, and the number of moles of each type is defined as M （ｍ） The average NCO distance of various diisocyanate compounds is defined as the number of atoms constituting the main chain of the divalent organic group intervening between two isocyanate groups contained in one molecule, and is defined as d ＮＣＯ（ｍ） When Formula: D = {Σ(M （ｎ） × d ＯＨ（ｎ） ) + Σ(M （ｍ） × d ＮＣＯ（ｍ） )} / (ΣM （ｎ） + ΣM （ｍ） ) The distance between urethane groups represented by the formula: D is 5 to 9.

1. A mill blank for dental cutting, comprising a polyurethane resin obtained by polyaddition of the above components in such a manner that all of the above requirements are satisfied.

2. The polyol component (I) is represented by the following general formula (1-a): 【Chemical 1】 In the formula, L is a hydrogen atom, a methyl group, or an ethyl group; a, which represents the number of methylene units, is an integer of 0 to 3, and multiple a's present in a molecule may be different from each other; R is a simple bond or a group represented by the following formula: 【Chemistry 2】 (wherein x is an integer from 2 to 4, r is an integer from 1 to 6, and R １ is a hydrogen atom or a methyl group, and there are multiple R １ may be different from each other.) It is a divalent group represented by the following formula: and 5 to 25 mol % of a diol compound having a radical polymerizable group in the molecule, The dental cutting mill blank according to claim 1 .

3. A milling machine equipped with a disc holder capable of holding a "standard disc," which is a cylindrical or disc-shaped mill blank for dental milling with a predetermined diameter and thickness and a convex or concave portion formed on the outer periphery, has an outer shape that is a standard disc used in CAD / CAM systems, and is provided with a marker on the upper surface near the outer periphery for confirming the mill blank mounting position.

2. The dental cutting mill blank according to claim 1.

4. 2. A method for manufacturing a dental cutting mill blank according to claim 1, comprising: As a manufacturing process of the machined portion, a raw material composition preparation step of preparing a raw material composition comprising a mixture of a polyol component (I) comprising a polyol compound and a diisocyanate component (II) comprising a diisocyanate compound, the mixture satisfying all of the conditions (1) to (3) above; and a polyaddition step of casting the raw material composition and then carrying out a polyaddition reaction to obtain a polyurethane resin molded product; A method for manufacturing a mill blank for dental cutting, comprising:

5. In the raw material composition preparation step, As the polyol component (I), The following general formulas (1-a) and (1-b) 【Chemistry 3】 In the formula, L is a hydrogen atom, a methyl group, or an ethyl group, and when a plurality of Ls are present in a molecule, the plurality of Ls may be different from each other; a, which represents the number of methylene units, is an integer of 0 to 3, and the plurality of as present in a molecule may be different from each other; R is a simple bond or a group represented by the following formula: 【Chemistry 4】 (wherein x is an integer from 2 to 4, y is an integer from 2 to 6, r is an integer from 1 to 6, and R １ is a hydrogen atom or a methyl group, and there are multiple R １ may be different from each other.) It is a divalent group represented by the following formula: "Polyol compounds having 3 or 4 hydroxyl groups in the molecule" represented by the formula: The following general formula (1-c) 【Chemistry 5】 In the formula, b is an integer of 3 to 5, R has the same meaning as R in the general formulae (1-a) and (1-b), and X is a group represented by the following formula: 【Chemistry 6】 (However, R １１ is an alkyl group having 1 to 3 carbon atoms. When b is 4, at least one of X is not a hydrogen atom, and when b is 5, both of X are not hydrogen atoms, and multiple Xs may be different from each other. "Polyol compound having 3 to 5 hydroxyl groups in the molecule" A specific polyol compound (I) comprising at least one compound selected from the group consisting of ｓ ) is used containing 40 to 100 mol %; 3. The method for manufacturing a mill blank for dental cutting according to claim 2.

6. The polyol component (I) is the specific polyol compound (I) consisting of at least one compound selected from "polyol compounds having three hydroxyl groups in the molecule" represented by the general formula (1-a). ｓ ): 75 to 95 mol % and a diol compound containing a radical polymerizable group in the molecule: 5 to 25 mol %. The method for manufacturing a mill blank for dental cutting according to claim 4.

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