JP7525129B2 - Manufacturing method of dental processing blanks - Google Patents

Description

The present invention relates to a method for manufacturing a dental processing blank for cutting and processing dental prostheses such as dental crowns, partial crowns, and dentures, and in particular, a dental processing blank whose cutting portion is made of a laminate of hybrid resin layers with different color tones, etc.

Dental prostheses used in dental treatment are generally formed by casting metallic materials such as gold, silver, titanium, palladium alloys, etc., by processing non-metallic materials such as ceramics and hybrid resins, or by forming a core part from a metallic material and a surface part such as a veneer from a non-metallic material. Note that hybrid resin means a composite material in which an inorganic filler (hereinafter also referred to as "inorganic filler") is densely dispersed in a resin matrix, and is usually obtained by polymerizing and curing a paste-like polymerizable and curable composition containing a polymerizable monomer, an inorganic filler, and a polymerization initiator by applying pressure and heating, etc.

Dental prostheses made entirely of non-metallic materials have the advantage of being aesthetically pleasing and free of metal allergies. In addition, the recent development of digital image technology and computer processing technology has made processing easier, and the demand for dental prostheses is rapidly increasing. For example, as disclosed in Patent Document 1, CAD/CAM systems that use computer-aided design (CAD) and computer-aided manufacturing (CAM) technology to cut dental blanks made of non-metallic materials and form dental prostheses using CAD/CAM devices based on intraoral images are becoming more widely used. Here, the dental blank refers to a cut object (also called a mill blank) that can be attached to a cutting machine in a CAD/CAM system, and usually has a cut part and a holding part that allows it to be attached to the cutting machine. The parts to be cut are generally solid blocks formed into a rectangular or cylindrical shape, or solid disks formed into a plate or board shape, and there are also known parts to be cut made of hybrid resin.

In dental crown restoration treatment, the dental prosthesis may be required to have aesthetics such as color and appearance that are equal to or close to those of natural tissue. To ensure such aesthetics, for example, it is often not sufficient to fabricate dental processing blanks of a single color, and dental processing blanks of different colors are used. For this purpose, dental processing blanks with a multilayer structure in which multiple layers of different colors are integrated are used.

For example, Patent Document 2 proposes the following method for forming blocks for processing dental prostheses which have excellent aesthetic effects, excellent mechanical strength without special processing such as coating, can be used stably for a long period of time, are easy to process such as cutting and grinding, and do not leave bubbles inside the block. When a block is formed by overlapping multiple resin layers, the resin layers are firmly bonded to each other without a pressure step, and have a color tone close to natural and an improved aesthetic effect, with a color gradation. That is, a method for manufacturing a dental prosthesis processing block consisting of an integral combination of multiple block members is proposed, which includes the steps of preparing a mold with an inner shape corresponding to the outer shape of the block, filling the mold with a composite resin material containing a resin and an inorganic filler dispersed therein, which can form the block by a hardening process, subjecting the composite resin material to a rotational stirring process while the composite resin material is contained in the mold, and hardening the composite resin material after the stirring process by polymerization. The method includes filling the composite resin material in multiple batches, sequentially carrying out the rotational stirring process and the hardening process after each filling process, and further polymerizing and hardening the resulting hardened material after the final hardening process to form the combined body.

Patent Document 3 also proposes a dental CAD/CAM cutting block that is versatile, highly productive, and highly reproducible to the aesthetics of natural teeth, and is a dental CAD/CAM resin block in which a dentin repair resin layer and an enamel repair resin layer are laminated, and at least the dentin repair resin layer contains light diffusing particles and has a specific diffusion ratio. Patent Document 3 also describes how the composition that will become the dentin repair resin layer is filled into a mold to a specified height without trapping air bubbles, the upper surface is smoothed, and the composition is polymerized under heat and pressure, and then the composition that will become the enamel repair resin layer is additionally filled into the mold, the upper surface is smoothed, and the block is obtained by polymerizing under heat and pressure.

Furthermore, Patent Document 4 discloses a method for manufacturing a laminated mill blank that is both aesthetically pleasing and mechanically strong. This method for manufacturing a mill blank includes, for example, a step of sequentially filling a fluororesin container having a predetermined bottom area and height, which serves as a mold, with a plurality of paste-like polymerizable curable compositions each having a predetermined thickness, to obtain a pre-polymerized laminate, and then polymerizing the laminate.

Special table 2016-535610 publication International Publication No. 2009/154301 JP 2017-213394 A JP 2017-113224 A JP 2015-097854 A

The manufacturing method for a multi-layered dental machining blank (a block for machining dental prostheses or a cutting block for dental CAD/CAM) disclosed in Patent Documents 2 and 3 involves filling a mold with a hardenable composition that is the raw material for the base layer, polymerizing and hardening it to form a base layer (of a hardened body), and then filling the mold with a paste-like hardenable composition that is the raw material for the upper layer, polymerizing and hardening it to form an upper layer (of a hardened body), and this requires multiple polymerization and hardening processes that require pressurization, heating, and light irradiation. In addition, since the layers of the paste-like polymerizable and hardenable composition that are the raw material for two adjacent layers do not microscopically mix at the interface between the layers, a decrease in strength may be observed at the interface after polymerization.

In contrast, the method described in Patent Document 4 involves obtaining a (pre-polymerization) laminate (hereinafter also referred to as a "paste laminate") of the paste-like hardenable composition that serves as the raw material for each layer, before polymerization, which has the advantage that only one polymerization and hardening process is required and the interfacial strength between layers can be increased.

However, when the mass ratio of the inorganic filler to the total mass of the paste-like hardening composition (hereinafter also referred to as "inorganic filler filling rate") is high, depending on the method of laminating the paste, the boundary between layers may become disordered or air bubbles may be trapped between the layers. For example, when different types of paste-like hardening compositions are sequentially filled and laminated in one mold, even if the top surface (which will be the boundary surface) is adjusted to be flat after the first layer is filled and then the second layer is filled, the boundary between the layers may be disordered due to the flow of the paste during filling. Due to such disorder, the resulting product may have a disordered interlayer interface or may contain voids inside, resulting in reduced strength and prone to chipping during cutting.

The present invention aims to provide a method for manufacturing a dental machining blank having a cutting part made of a hybrid resin laminate in which multiple layers made of hybrid resin are laminated, which can reduce the number of times the paste-like hardenable composition that is the raw material for the hybrid resin is polymerized and hardened, and even when a paste-like hardenable composition with a high inorganic filler filling rate is used, the hybrid resin laminate that is the cutting part can be made to have each layer neatly and reliably laminated without strength loss or chipping by suppressing the occurrence of disturbances at the layer interfaces and the occurrence of voids at the internal interfaces.

The present invention solves the above-mentioned problems, and an embodiment of the present invention is a method for producing a dental machining blank having a cutting portion made of a hardened paste laminate in which a plurality of layers made of a paste-like polymerizable curable composition containing a polymerizable monomer, an inorganic filler, and a polymerization initiator are laminated, the method comprising the steps of:
A: A step of preparing a form kit comprising a plurality of form units each composed of a cylindrical body having both ends open and a columnar hollow portion formed therein, the form kit being capable of forming a connected form having a connected cylindrical body and a connected columnar hollow portion formed by connecting the cylindrical bodies and the columnar hollow portions of each form unit, respectively, by connecting the plurality of form units in the axial direction of the cylindrical bodies;
B: A step of preparing a plurality of types of paste-like polymerizable and hardenable compositions to be filled into each of the plurality of frame units prepared in the above step;
C: A step of filling the paste-like polymerizable curable composition into each of the plurality of mold units prepared in the above step to prepare a plurality of paste-filled mold units;
D: A step of sequentially connecting the plurality of paste-filled form units obtained in the above step to form the connected form, and at the same time, bonding the paste-like polymerizable curable compositions filled in the paste-filled form units in the connected columnar hollow portions to form a paste laminate, thereby obtaining a paste laminate-filled connected form;
E: a pressurizing step of pressing the paste laminate filled connected form obtained in the above step in the axial direction of the cylindrical body; and F: a hardening step of hardening the paste laminate inside the connected columnar hollow portion pressurized in the above step to form a hardened body.
The method for producing the dental machining blank is characterized in that it comprises:

In the manufacturing method of the dental machining blank of the above form (hereinafter also referred to as the "manufacturing method of the present invention"), it is preferable to prepare paste-like polymerizable hardening compositions having different color tones in the step B, and to fill each mold unit with a paste-like polymerizable hardening composition having a different color tone in the step C.

The manufacturing method of the present invention also includes cases where the formwork kit consists of two formwork units and cases where the formwork kit consists of three or more formwork units, and each of these is preferably a method as follows.

That is, when the form kit is composed of two form units, one of which is a base end form unit and the other is a tip end form unit,
In the step C, an extrusion plate having a flat contact surface that comes into contact with the paste-like polymerizable curable composition filled in the columnar cavity and for extruding the filled paste-like polymerizable curable composition from a supply-side opening that is an opening on the other side is inserted into the columnar cavity so as to be movable back and forth and detachable, thereby blocking a closing-side opening that is an opening at one end of each form unit, and then the columnar cavity is densely filled with the paste-like polymerizable curable composition, thereby producing a paste-filled base-end form unit and a paste-filled tip-end form unit in which the closing-side opening that is an opening on one side is blocked with the extrusion plate and a planar or substantially planar paste joint surface is formed at the supply-side opening that is an opening on the other side,
The step D comprises:
Da1: a step of moving an extrusion plate toward a supply side opening of at least one of the paste filled base end form unit and the paste filled tip end form unit to extrude a paste-like polymerizable curable composition and cause a part of the paste-like polymerizable curable composition to protrude from the supply side opening to form a paste joint surface having a convex curved shape; and Da2: after the step, a step of connecting both paste filled form units so that the paste joint surface of the paste filled base end form unit and the paste joint surface of the paste filled tip end form unit overlap to form a connected form, and a step of connecting the paste filled form units to form a paste laminate in the connected columnar hollow portion to form a paste laminate-filled connected form in which both end openings of the connected form are substantially blocked by the extrusion plate (hereinafter also referred to as a "two-unit lamination method").

In addition, when the form kit is composed of three or more form units, the form units arranged at one end and the other end of the connecting form are respectively referred to as a base end form unit and a tip end form unit, and the form unit arranged between these two form units is referred to as an intermediate form unit,
In the step C, an extrusion plate having a flat contact surface that comes into contact with the paste-like polymerizable curable composition filled in the columnar cavity and for extruding the filled paste-like polymerizable curable composition from the opening on the other side is inserted into the columnar cavity so as to be freely movable back and forth and detachable, thereby closing one end opening of each frame unit, and then the columnar cavity is densely filled with the paste-like polymerizable curable composition, thereby producing a paste-filled base end frame unit, a paste-filled tip frame unit and a paste-filled intermediate end frame unit in which the closing side opening, which is the opening on one side, is closed with the extrusion plate and a planar or substantially planar paste joint surface is formed at the supply side opening, which is the opening on the other side;
The step D comprises:
Db1: A step of moving an extrusion plate toward a supply side opening of at least one of the paste-filled base end form unit and the paste-filled intermediate form unit disposed adjacent thereto to extrude a paste-like polymerizable curable composition, causing a part of the paste-like polymerizable curable composition to protrude from the supply side opening, thereby forming a paste joint surface in a convex curved shape;
Db2: after the above process, a process of overlapping the paste joint surface of the paste-filled base end form unit and the paste joint surface of the paste-filled intermediate form unit so as to overlap with each other to form a partially connected form consisting of a connected body of both form units, and inside the partially connected form, joining the paste-like polymerizable curable composition filled in both paste-filled form units to form a paste partial laminate, and then removing the extrusion plate blocking the closing side opening of the paste-filled intermediate form unit to obtain a partial paste laminate filled connected form having a planar or substantially planar paste joint surface with the closing side opening as a supply side opening of the partial connected form;
Db3: When there is no paste-filled intermediate form unit to be arranged adjacent to the partial paste laminate-filled connected form, the partial paste laminate-filled connected form obtained in the above step is used as the final partial paste laminate-filled connected form;
When there is a paste-filled intermediate form unit to be disposed adjacent to the partial paste laminate-filled connected form, the extrusion plate of the paste-filled base end form unit in the partial paste laminate-filled connected form and/or the extrusion plate of the paste-filled intermediate form unit to be disposed adjacent are moved toward the supply side opening to extrude the paste-like polymerizable curable composition until there are no more paste-filled intermediate form units to be disposed adjacent to the partial paste laminate-filled connected form, and the paste joint surface of at least one of the partial paste laminate-filled connected form and the paste-filled intermediate form unit to be disposed adjacent to the partial paste laminate-filled connected form is made convexly curved, and then the connection by overlapping the paste joint surfaces of both of them so that they overlap and the removal of the extrusion plate are repeated to obtain an extended partial paste laminate-filled connected form having a planar or substantially planar paste joint surface as a final partial paste laminate-filled connected form, in which the number of connected paste-filled intermediate form units and the number of layers of the formed paste partial laminate are increased; and Db4: a step of moving the extrusion plate of the paste-filled base end form unit and/or the extrusion plate of the paste-filled tip end form unit in the final portion paste laminate filled connected form obtained in the above step toward the supply side opening to extrude the paste-like polymerizable hardenable composition, forming a convex curved paste joint surface of at least one of the final portion paste laminate filled connected form and the paste-filled tip end form unit, and then overlapping the two paste-filled form units so that their paste joint surfaces overlap to connect the two paste-filled form units to form a connected form, and at the same time , joining the paste-like polymerizable hardenable compositions filled in the two paste-filled form units in the connected columnar hollow portion to form a paste laminate, thereby obtaining a paste laminate filled connected form in which both end openings of the connected form are substantially blocked by the extrusion plates (hereinafter also referred to as a "three or more unit stacking method").

In the two-unit lamination method and the three or more unit lamination method, it is preferable to improve the interlayer adhesion in the paste laminate and the adhesion between the paste laminate and the inner surface of the connected formwork by exuding excess paste-like polymerizable curable composition from at least a part of the connecting portion of the formwork unit in the paste laminate-filled connected formwork and/or from at least a part of the sliding contact portion between the connected columnar cavity and both of the extrusion plates by applying pressure in the step E, and further, it is preferable to apply pressure of 0.024 to 0.60 MPa for 1 to 120 minutes in the step E.

In addition, in the three or more unit stacking method, it is preferable to perform a preliminary pressurizing step in which the partial paste laminate filled connected formwork and/or the extended partial paste laminate filled connected formwork are pressurized in the axial direction of the cylindrical body at at least one timing selected from the group consisting of the timing after completion of the process Db2 and the timing after completion of the connection by overlapping, which is performed at least once in the process Db3, and before removal of the extrusion plate.

Further, in the manufacturing method of the present invention, in the step B, a plurality of types of paste-like polymerizable curable compositions each containing a thermal polymerization initiator are prepared, and the paste laminate filled joint form that has been cured in the step F (curing step) and subjected to the step E (pressurizing step) is subjected to the following steps 1 to 3:
It is preferable to carry out heating in a temperature increasing pattern in which the following steps are sequentially performed: Step 1: maintaining the temperature within the range of 30°C or higher and 45°C or lower for at least 2 hours; Step 2: maintaining the temperature within the range of more than 45°C and less than 65°C for at least 5 hours; and Step 3: maintaining the temperature within the range of more than 65°C and less than 100°C for at least 2 hours.

In the manufacturing method of the present invention, the hybrid resin laminate to be cut is obtained by polymerizing and curing a paste laminate in which multiple layers made of a paste-like polymerizable curable composition are laminated, so that the number of polymerization and curing steps can be reduced (usually to one). In addition, a form kit consisting of multiple form units that can be connected to form a connected form is used, and the form units are filled with the paste-like polymerizable curable composition (hereinafter sometimes referred to as "fluid paste") and laminated in that state. Therefore, even if a fluid paste with a high inorganic filler filling rate and low fluidity is used, defects such as disturbances and voids are unlikely to occur at the interface between the layers. Furthermore, since pressure is applied after lamination and then polymerization and curing are performed, not only can the shape of the mold be reliably transferred, but the occurrence of defects such as voids can be more highly suppressed.

In particular, by adopting a specific temperature rise pattern when polymerizing and curing under heat in the curing step F, it is possible to prevent air from entering through the joints (seams) of the formwork units in the interlocking formwork, and to prevent poor curing at the joints, regardless of the material of the formwork units used.

FIG. 2 is a diagram illustrating the lamination step in the method according to the present invention in the form of a two-unit lamination method. FIG. 2 is a perspective view showing a mold unit for forming a dental work blank. FIG. 2 is an oblique view showing an example of a filling tool used in step C in a method for manufacturing a multilayered dental working blank according to one embodiment of the present invention, showing the state before filling with a fluid paste. FIG. 11 is a plan view showing the state in which a fluid paste is filled using a filler. 13 is a plan view showing a state in which the form unit filled with the fluid paste is being removed together with the form unit retaining plate. FIG. 13 is a perspective view showing a state in which the form unit filled with the fluid paste has been detached together with the form unit retaining plate. FIG. 10 is a schematic cross-sectional view of a filling tool illustrating the state in which a form unit is filled with fluid paste. FIG. FIG. 1 is an oblique view showing an example of a lamination device used in the lamination process when manufacturing a two-layer dental machining blank by a manufacturing method for a multi-layered dental machining blank according to one embodiment of the present invention, and shows the state in which the bottom layer of the formwork unit filled with fluid paste is placed in the lamination device. FIG. 11 is a perspective view showing a state in which the filled fluid paste is protruding from a form unit arranged in the lamination device. FIG. 2 is a perspective view showing form units stacked by a stacking device. FIG. 11 is a perspective view illustrating an example of a form unit holder that holds stacked form units when the stacked form units are subjected to a hardening step. FIG. 2 is a diagram illustrating the lamination process when manufacturing a three-layered dental machining blank. FIG. 2 is a schematic perspective view showing a state in which a blank holding pin for cutting is joined to a dental machining blank having a two-layer structure. FIG. 2 is a perspective view showing an outline of a dental prosthesis for a back tooth that is machined by cutting a dental machining blank.

1. Overview of the manufacturing method of the present invention In the manufacturing method of the present invention, in order to reduce the number of polymerization and hardening treatments, preferably to one, when obtaining a hybrid resin laminate that will be the cutting portion of a dental processing blank, a paste laminate in which multiple layers made of a paste-like polymerizable and hardenable composition containing a polymerizable monomer, an inorganic filler, and a polymerization initiator are laminated is polymerized and hardened to obtain a hybrid resin laminate, and the hybrid resin laminate is characterized in that the following steps A to E are performed before performing the following step F (hardening step) in order to prevent shape defects from occurring in the obtained hybrid resin laminate and further to prevent defects such as disturbances and voids from occurring at the interfaces of each layer.

A: A form kit preparation step of preparing a form kit comprising a plurality of form units each made of a cylindrical body having both ends open and a columnar hollow portion formed therein, the plurality of form units being capable of forming a connected form having a connected cylindrical body and a connected columnar hollow portion formed by connecting the cylindrical bodies and columnar hollow portions of each of the form units, respectively, by connecting the plurality of form units in the axial direction of the cylindrical body. B: A paste-like polymerizable curable composition (fluid paste) preparation step of preparing a plurality of types of paste-like polymerizable curable compositions (hereinafter also referred to as "fluid paste") to be filled into each of the plurality of form units prepared in the above step. C: A paste-filled form unit production step of filling each of the plurality of form units prepared in the above step with the paste-like polymerizable curable composition to produce a plurality of paste-filled form units. D: A lamination process in which the multiple paste-filled formwork units obtained in the above process are sequentially connected to form the connected formwork, and the paste-like polymerizable hardener composition filled in each paste-filled formwork unit is joined within the connected columnar hollow portion to form a paste laminate, thereby obtaining a paste laminate-filled connected formwork; E: A pressurizing process in which the paste-filled connected formwork obtained in the above process is pressurized in the axial direction of the cylindrical body; F: A hardening process in which the paste laminate inside the connected columnar hollow portion pressurized in the above process is hardened to form a hardened body.

It is common to polymerize and harden a paste-like polymerizable hardening composition by applying pressure and heat to obtain a hybrid resin. In addition, a method is also known in which the paste-like polymerizable hardening composition is filled into a mold made of a material other than metal and equipped with a means for equalizing the pressure inside and outside in order to prevent the inclusion of air bubbles or the occurrence of cracks during polymerization, and then the mold is pressurized to a predetermined pressure as a whole and then heated for polymerization (see Patent Document 5). However, in step E (hardening step) of the method of the present invention, there is no particular need to apply pressure, and in step E (pressurizing step), it is sufficient to apply pressure only in a predetermined direction, and there is no particular need to apply pressure to the entire mold.

1-2. Feature 1 of the manufacturing method of the present invention: mold The manufacturing method of the present invention is similar to the method described in Patent Document 4 in that a paste laminate is formed inside a mold and then polymerized and cured to form a hybrid resin laminate, but it differs in the mold (step A) and the method of forming the paste laminate (steps C and D) used, and also in that a predetermined pressure is applied before polymerization and curing (step E).

That is, the method of the present invention is characterized in that a form kit consisting of a plurality of form units that can be connected to each other to form a connected form is used, each form unit is filled with a paste-like polymerizable curable composition to form a "paste-filled form unit", and these are connected to obtain a "paste laminate-filled connected form" in which a paste laminate is filled in the connected form. As a result, even if a fluid paste with a high inorganic filler filling rate and low fluidity is used, defects such as disturbances and voids are unlikely to occur at the interface between each layer. Furthermore, the manufacturing method of the present invention is characterized in that the "paste laminate-filled connected form" is pressed in the axial direction (stacking direction) of the cylindrical body before hardening, which not only ensures that the shape of the mold can be reliably transferred, but also makes it possible to more highly suppress the occurrence of defects such as voids. Therefore, dental processing blanks having a cutting portion made of a hybrid resin laminate with excellent appearance can be efficiently manufactured.

If the formwork units used are made of resin, slight air infiltration or poor curing may occur at the joints of the formwork units in the linked formwork during polymerization and hardening. However, by adopting a specific heating pattern when polymerizing and hardening under heat, such air infiltration and poor curing can be prevented.

1-3. Feature 2 of the manufacturing method of the present invention: Lamination method In the manufacturing method of the present invention, in step C, one end opening (closing side opening) of the form unit is blocked with an extrusion plate, and then a paste-like polymerizable curable composition (fluid paste) is filled in, and a "paste-filled form unit" is obtained in which the surface of the fluid paste exposed from the other end opening (supply side opening) of the form unit (this surface is a surface that joins with the fluid paste filled in the other "paste-filled form unit" to be connected in step D, and therefore this exposed surface is also called the "paste joining surface") is planar or substantially planar and forms the same plane or substantially the same plane as the supply opening end surface, and in step D, when connecting the "paste-filled form units", it is preferable to adopt a method in which the paste joining surface of at least one of the two connected "paste-filled form units" is made into a convex curved surface that is slightly convex from the supply side opening, and then the paste joining surfaces are joined together (hereinafter also referred to as the "convex curved surface method").

When the convex surface contact method is used, contact begins at the convex surface present in the center of the paste contact surface, and the contact area gradually expands in the circumferential direction along the curved surface, so not only are defects such as air bubbles less likely to occur, but even if they do occur, they are pushed out in the circumferential direction and do not remain inside. Furthermore, even if air bubbles or the like remain near the periphery of the contact interface, they are expelled to the outside during the pressurization process, so the effect of preventing defects such as disturbances in the interface between each layer and voids can be achieved to an extremely high level.

When using the convex curved surface method, process D differs slightly between the two-unit lamination method and the three or more unit lamination method, and is as shown below.

<<Step D (Lamination Step) in the Two-Unit Lamination Method>>
A process including the following steps Da1 and Da2: Da1: a process of moving an extrusion plate toward a supply side opening of at least one of the paste filled base end form unit and the paste filled tip end form unit to extrude a paste-like polymerizable curable composition and cause a part of the paste-like polymerizable curable composition to protrude from the supply side opening to form a paste joint surface having a convex curved shape; and Da2: a process of connecting both paste filled form units after the above process so that the paste joint surface of the paste filled base end form unit and the paste joint surface of the paste filled tip end form unit overlap to form a connected form, and joining the paste-like polymerizable curable compositions filled in both paste filled form units within the connected columnar hollow portion to form a paste laminate, thereby obtaining a paste laminate filled connected form in which both end openings of the connected form are substantially blocked by the extrusion plate.

<<Step D (Lamination Step) in Three or More Unit Lamination Method>>
Step Db1 includes the following steps Db1 to Db4: a step of moving an extrusion plate toward a supply side opening of at least one of the paste-filled base end form unit and the paste-filled intermediate form unit arranged adjacent thereto to extrude a paste-like polymerizable curable composition, causing a part of the paste-like polymerizable curable composition to protrude from the supply side opening, and forming a paste joint surface in a convex curved shape:
Db2: after the above process, a process of overlapping the paste joint surface of the paste-filled base end form unit and the paste joint surface of the paste-filled intermediate form unit so as to overlap with each other to form a partially connected form consisting of a connected body of both form units, and inside the partially connected form, joining the paste-like polymerizable curable composition filled in both paste-filled form units to form a paste partial laminate, and then removing the extrusion plate blocking the closing side opening of the paste-filled intermediate form unit to obtain a partial paste laminate filled connected form having a planar or substantially planar paste joint surface with the closing side opening as a supply side opening of the partial connected form;
Db3: When there is no paste-filled intermediate form unit to be arranged adjacent to the partial paste laminate-filled connected form, the partial paste laminate-filled connected form obtained in the above step is used as the final partial paste laminate-filled connected form;
When there is a paste-filled intermediate form unit to be disposed adjacent to the partial paste laminate-filled connected form, the extrusion plate of the paste-filled base end form unit in the partial paste laminate-filled connected form and/or the extrusion plate of the paste-filled intermediate form unit to be disposed adjacent are moved toward the supply side opening to extrude the paste-like polymerizable curable composition until there are no more paste-filled intermediate form units to be disposed adjacent to the partial paste laminate-filled connected form, and the paste joint surface of at least one of the partial paste laminate-filled connected form and the paste-filled intermediate form unit to be disposed adjacent to the partial paste laminate-filled connected form is made convexly curved, and then the connection by overlapping the paste joint surfaces of both of them so that they overlap and the removal of the extrusion plate are repeated to obtain an extended partial paste laminate-filled connected form having a planar or substantially planar paste joint surface as a final partial paste laminate-filled connected form, in which the number of connected paste-filled intermediate form units and the number of layers of the formed paste partial laminate are increased; and Db4: a process in which the extrusion plate of the paste filled base end form unit and/or the extrusion plate of the paste filled tip end form unit in the final portion paste laminate filled connected form obtained in the above process are moved toward the supply side opening to extrude the paste-like polymerizable hardenable composition, so that the paste joint surface of at least one of the final portion paste laminate filled connected form and the paste filled tip end form unit is made convexly curved, and then the two paste filled form units are overlapped so that their paste joint surfaces overlap to connect the two paste filled form units to form a connected form, and within the connected columnar hollow portion, the paste-like polymerizable hardenable composition filled in both paste filled form units is joined to form a paste laminate, thereby obtaining a paste laminate filled connected form in which both end openings of the connected form are substantially blocked by the extrusion plates.

Below, a method and an apparatus for manufacturing a multi-layered dental blank according to a preferred embodiment of the present invention will be described with reference to the drawings.

2. Regarding the "two-unit lamination method" In the two-unit lamination method, a form kit consisting of a base end form unit and a tip end form unit is used. In the step C (paste-filled form unit preparation step), for each of the base end form unit and the tip end form unit, an extrusion plate having a flat contact surface that comes into contact with the paste-like polymerizable curable composition filled in the columnar cavity and for extruding the filled paste-like polymerizable curable composition from the supply side opening, which is the opening on the other side, is inserted into the columnar cavity so as to be freely movable forward and backward and detachable, and the closed side opening, which is the opening at one end of each form unit, is then densely filled with the paste-like polymerizable curable composition in the columnar cavity, thereby preparing a paste-filled base end form unit and a paste-filled tip form unit in which the closed side opening, which is the opening on one side, is blocked by the extrusion plate, and a planar or substantially planar paste joint surface is formed in the supply side opening, which is the opening on the other side;
The step D includes the following steps Da1 and Da2.

Step Da1: For at least one of the paste-filled base end form unit and the paste-filled tip end form unit, the extrusion plate is moved toward the supply side opening to extrude the paste-like polymerizable hardenable composition, causing a portion of the paste-like polymerizable hardenable composition to protrude from the supply side opening, thereby forming a paste joint surface in the shape of a convex curved surface.

Step Da2: After the above step, both paste-filled formwork units are connected so that the paste joint surface of the paste-filled base end formwork unit overlaps with the paste joint surface of the paste-filled tip end formwork unit to form a connected formwork, and the paste-like polymerizable curable composition filled in both paste-filled formwork units is joined in the connected columnar cavity to form a paste laminate, thereby obtaining a paste-laminated connected formwork in which both end openings of the connected formwork are substantially blocked with extrusion plates.

In the "two-unit lamination method," a first paste-like polymerizable hardening composition and a second paste-like polymerizable hardening composition, each having a different color tone, are filled into the base end mold unit and the tip end mold unit, respectively, to produce a dental machining blank 1 having a cutting portion made of a two-layer hybrid resin laminate with a first layer 1a and a second layer 1b, each having a different color tone, as shown in FIG. 13. A blank holding pin 2 is joined to this dental machining blank 1, which is then fixed to a cutting device of a CAD/CAM system via the blank holding pin 2, and is cut into a dental prosthesis 10, as shown in FIG. 14.

2-1. Step A (form kit preparation step), form unit, and extrusion plate In step A (form kit preparation step), a form kit is prepared that is made up of a plurality of form units each made up of a cylindrical body with both ends open and a columnar cavity formed therein, and that can form a connected form having a connected cylindrical body and a connected columnar cavity formed by connecting the cylindrical body and the columnar cavity of each form unit, respectively, by connecting the plurality of form units in the axial direction of the cylindrical body. The connected form, form unit, and extrusion plate used when filling the fluid paste will be described with reference to Figures 1 to 3.

Figure 1 is a diagram illustrating the lamination process for joining two layers when manufacturing a dental machining blank 1 having a two-layer structure. The first layer 1a and the second layer 1b are each formed by a first form unit 3, which is a base end form unit, and a second form unit 4, which is a tip end form unit. That is, each of the first form unit 3 and the second form unit 4 is filled with a fluid paste (first and second paste-like polymerizable hardenable compositions) P of different types of dental hardenable compositions.

When the thicknesses of the first layer 1a and the second layer 1b are equal, the same formwork unit is used for the first formwork unit (base end formwork unit) 3 and the second formwork unit (tip end formwork unit) 4 that form the first layer 1a and the second layer 1b. Even if the thicknesses are different, the basic structure of these formwork units 3 and 4 is the same, so the first formwork unit 3 will be described below with reference to Figure 2.

As shown in FIG. 2, the first formwork unit 3 is a cylindrical body having a columnar hollow portion, and the openings at both ends of the cylindrical body are the closing side opening 3b and the supply side opening 3c. The closing side opening 3b accommodates an extrusion plate 3a having a flat contact surface that is slidable in the axial direction of the cylindrical body within the hollow portion of the first formwork unit 3. As shown in FIG. 1(C), the closing side opening 4b of the second formwork unit 4 accommodates an extrusion plate 4a. These extrusion plates 3a and 4a are positioned at the closing side openings 3b and 4b when the formwork units 3 and 4 are filled with fluid paste P, and the closing side openings 3b and 4b are closed. The fluid paste P is supplied from the supply side openings 3c and 4c on the opposite side to the closing side openings 3b and 4b, as described below, and filled into the formwork units 3 and 4.

When the generatrix of the columnar cavity of the first formwork unit 3 and the second formwork unit 4 are aligned and connected, a connected columnar cavity is formed. In other words, the first formwork unit (base end formwork unit) 3 and the second formwork unit (tip end formwork unit) 4 constitute a formwork kit, and this formwork kit is prepared in the preparation process. Note that it is possible to produce blanks of any shape by making the formwork unit shape match the desired blank shape, in addition to the block shape shown in the figure.

In addition, the figure shows the first formwork unit 3 and the second formwork unit 4 with columnar hollow portions of the same shape, but the shape of the hollow portions may be columnar so long as a connected columnar hollow portion is formed when the generatrix is aligned and connected; for example, one or both may be cylindrical, or even a truncated pyramid or truncated cone-shaped connected columnar hollow portion. The inner surface of the columnar hollow portion may also be given a structure for fixing and positioning a blank holding pin, a structure for fixing to a cutting device, or a shape for providing other functionality.

Materials that can be used for the cylindrical body of the formwork unit include metal materials such as aluminum or aluminum alloy, stainless steel, iron, and brass, and plastic materials with thermosetting or thermoplastic properties such as polypropylene, polyethylene, polyurethane, POM, PEK, PEKK, and PEEK. However, it is preferable to use thermoplastic or thermosetting resins with a heat resistance of 100°C or higher because they are easy to mold and can be used when heat polymerization is performed in step F.

2-2. Step B (fluidity paste preparation step) and fluidity paste In step B (fluidity paste preparation step), a plurality of types of paste-like polymerizable hardenable compositions (fluidity pastes) are prepared to be filled into the plurality of form units prepared in the previous step, specifically, a first paste-like polymerizable hardenable composition (for filling the base end form unit) and a second paste-like polymerizable hardenable composition (for filling the tip end form unit) having different color tones are prepared.

Here, the paste-like polymerizable curable composition (fluid paste) means a paste-like polymerizable curable composition containing a polymerizable monomer, an inorganic filler, and a polymerization initiator. These materials can be used without any particular restrictions as long as they can be used as materials for dental hybrid resins. For example, a (meth)acrylic acid-based polymerizable monomer can be used as the polymerizable monomer, and a thermal polymerization initiator can be used as the polymerization initiator. The inorganic filler filling rate of the fluid paste is preferably 60 to 99 wt%, more preferably 65 to 97 wt%, and even more preferably 70 to 95 wt%. Although the fluidity decreases when the inorganic filling rate is set to 60% or more, a dental blank having excellent physical properties as a dental prosthesis can be obtained. The color tone of the paste, and therefore the color tone of the hybrid resin, which is the hardened product thereof, can be adjusted by blending coloring substances such as pigments and dyes. In addition, in order to achieve the desired properties of the blank, any optional components may be added to the above. Examples include polymerization inhibitors, chain transfer agents, fluorescent agents, ultraviolet absorbers, antioxidants, antibacterial agents, and X-ray contrast agents, but other additives known for use in dental blanks can also be used.

Prior to producing the dental blank 1, it is preferable to subject the flowable paste to a vacuum to degas it and remove any air bubbles.

2-3. Step C (paste-filled form unit preparation step) and filling tool In the step C (paste-filled form unit preparation step), the first paste-like polymerizable curable composition (first fluid paste) is filled into a base end form unit, and the second paste-like polymerizable curable composition (second fluid paste) is filled into a tip end form unit to prepare a paste-filled base end form unit and a paste-filled tip end form unit. At this time, for each of the base end frame unit and the tip end frame unit, an extrusion plate having a flat contact surface that comes into contact with the paste-like polymerizable curable composition filled in the columnar cavity and for extruding the filled paste-like polymerizable curable composition from the supply side opening, which is the opening on the other side, is inserted into the columnar cavity so as to be freely movable forward and backward and detachable, and the closed side opening, which is the opening at one end of each frame unit, is then densely filled with the paste-like polymerizable curable composition in the columnar cavity, and further, it is important that the closed side opening, which is the opening on one side, is blocked by the extrusion plate, and a planar or substantially planar paste joint surface is formed on the supply side opening, which is the opening on the other side. Here, the planar paste joint surface means one that constitutes the same plane as the supply opening end surface, and the substantially planar paste joint surface means one that constitutes substantially the same plane as the supply opening end surface. In addition, "substantially" means that the step with the supply opening end surface is negligible, for example, ±500 μm or less, particularly ±300 μm or less.

(1) Filling Tool Step C can be suitably carried out using a filling tool described below. That is, Fig. 3 to Fig. 7 show a filling tool 5 used when filling the form units 3 and 4 with the fluid paste P. As shown in Fig. 3, the filling tool 5 includes a holding plate 5a for holding the form units 3 and 4, a substantially U-shaped positioning block 5b for receiving and positioning the holding plate 5a, and a filling plate 5c on which the positioning block 5b is attached to a support surface 5c1.

The retaining plate 5a is provided with a form unit storage section 5d that stores the form units 3 and 4. This form unit storage section 5d is formed by a through hole provided in the retaining plate 5a.

In this embodiment, a structure in which a single form unit storage section 5d is formed on the holding plate 5a is described, but the arrangement is not limited to this, and multiple units may be aligned in a straight line or around a circle, or arranged in a matrix. These arrangements can be designed as appropriate to suit the convenience of the filling device.

It is also preferable to give the holding plate 5a and/or the form unit housing section 5d a shape that takes into account positioning and the convenience of pre- and post-processing, and it is sufficient to design it appropriately according to the desired blank shape and the convenience of its arrangement.

On the other hand, the positioning block 5b is fixed on the support surface 5c1 of the filling plate 5c as shown in FIG. 3. The U-shaped inner part of the positioning block 5b has a structure corresponding to the outer shape of the holding plate 5a, and the holding plate 5a is held in this U-shaped inner part. Note that the shape is not limited to the shape shown in the figure, and it is preferable to design the shape according to the shape of the holding plate 5a and the convenience of the device, and it is sufficient to design it appropriately so that the holding plate 5a can be easily removed and fixed.

For example, it is not limited to a U-shape, but can also be a V-shape or use a sliding member such as a rail. Furthermore, a single holding plate 5a can be formed with multiple formwork unit storage sections 5d, and the positioning block 5b can be shaped to hold this holding plate 5a. It is also possible to have a structure in which the positioning block 5b is divided into a pair, and it is also preferable to change the mounting position of this positioning block 5b relative to the filling plate 5c so that the holding state of the holding plate 5a can be adjusted.

The filling plate 5c is provided with a filling nozzle 5e with an opening provided on the support surface 5c1. As shown in Figures 3, 6, and 7(A), a paste flow path 5c2 is formed toward the opening of the filling nozzle 5e. The shape of the flow path may be straight without a slope, but as shown in Figure 7(B), it may be a pyramidal or conical paste flow path 5c3 with the opening of the filling nozzle 5e as the upper base. It is preferable to design it appropriately so as to avoid any inconvenience, taking into account the properties of the fluid paste and the desired blank shape. The opening of the filling nozzle 5e is not limited to the circular shape shown in the figure, and both the opening area and shape can be set appropriately. For example, it can be the same shape as the opening of the formwork unit. The filling nozzle 5e is also arranged at a position corresponding to the through hole of the formwork unit storage section 5d of the holding plate 5a held by the positioning block 5b. Therefore, the fluid paste P of the curable composition extruded from an extrusion device (not shown) flows through the paste flow path 5c2 and is supplied from the filling nozzle 5e into the form units 3 and 4 housed in the form unit housing section 5d.

(2) Specific filling method using a filling tool A specific filling method using the filling tool 5 will be described. First, the first frame unit (base end frame unit) 3 is held in the frame unit housing portion 5d of the holding plate 5a of the filling tool 5. Next, as shown in FIG. 4, the holding plate 5a holding the first frame unit (base end frame unit) 3 is held by the positioning block 5b so as to fit inside the U-shape of the positioning block 5b. In this state, the filling nozzle 5e arranged on the support surface 5c1 is positioned opposite the cavity of the first frame unit (base end frame unit) 3. Then, before starting to fill the fluid paste P, the extrusion plate 3a is inserted into the columnar cavity of the frame unit so that its contact surface contacts the support surface 5c1. Then, the first paste-like polymerizable curable composition (fluid paste) P is filled into the first frame unit (base end frame unit) 3 through the paste flow path 5c2 by an injection device (not shown) connected below the filling plate 5c. As the amount of fluid paste P filled increases, the extrusion plate 3a located at the supply side opening 3c of the first formwork unit 3 is gradually pushed up and moves toward the closing side opening 3b, as shown in Fig. 7. When the extrusion plate 3a has moved to the closing side opening 3b, a predetermined amount of fluid paste P is filled into the first formwork unit 3. In order to avoid oversupply of the fluid paste P at this time, the supply can be stopped when the filling amount reaches a predetermined amount, or the position of the extrusion plate 3a can be detected and the supply can be stopped when the extrusion plate 3a reaches a predetermined position.

The first form unit 3, which has been filled with a predetermined amount of fluid paste P and has become a paste-filled form unit, is detached from the positioning block 5b together with the holding plate 5a. At this time, as shown in Figures 5 and 6, the holding plate 5a is moved so as to be guided along the inner wall surface of the U-shape of the positioning block 5b and pulled out from the open side of the U-shape, and the lower surface of the holding plate 5a is moved so as to scrape against the support surface 5c1 of the filling plate 5c, and the holding plate 5a is detached from the filling plate 5c. By the holding plate 5a scraping against the support surface 5c1 in this way, a planar paste joint surface Pa is formed on the surface of the fluid paste P as shown in Figure 1 (A). Then, by separating it from the holding plate after detaching it from the filling tool 5, a paste-filled base end form unit, which is a "paste-filled form unit" in which the surface of the fluid paste (paste joint surface) exposed from the supply side opening of the form unit is planar or substantially planar and forms the same plane as the supply opening end surface, can be produced.

The second formwork unit (tip formwork unit) 4 can also be filled with fluid paste P in the same manner to produce a paste-filled tip formwork unit with a planar paste joint surface Pa as shown in Figure 1 (C).

2-4. Step D (Lamination Step) and Lamination Device In step D (lamination step), first, for at least one of the paste-filled base end form unit 3 and the paste-filled tip end form unit 4, the extrusion plate is moved toward the supply side opening to extrude the paste-like polymerizable curable composition, and a part of the paste-like polymerizable curable composition is protruded from the supply side opening to make the paste joint surface a convex curved surface (step Da1), and then, both paste-filled form units are connected so that the paste joint surface of the paste-filled base end form unit 3 and the paste joint surface of the paste-filled tip end form unit 4 overlap to form a connected form, and in the connected columnar cavity, the paste-like polymerizable curable composition filled in both paste-filled form units is joined to form a paste laminate, and a "paste laminate filled connected form" in which both end openings of the connected form are substantially blocked by the extrusion plate is obtained (step Da2).

(1) Lamination device The above step D can be suitably performed using a lamination device described below. That is, Figs. 8 to 10 show a lamination device 6 used in the lamination step of laminating the fluid paste P filled in the paste-filled first form unit (paste-filled base end form unit) 3 and the paste-filled first form unit (paste-filled tip form unit) 4. It is preferable to appropriately design the structure of the lamination device in consideration of productivity and efficiency. As long as it is possible to stack the paste-filled form units 3 and 4 while maintaining their positions, the holding structure and arrangement are not limited to those using pins as shown in the figures. A plurality of units may be aligned in a straight line or around a circle, or a larger number of units may be arranged in a matrix.

As shown in FIG. 8, the stacking device 6 mainly comprises a holding plate 6a on which the paste-filled formwork units 3 and 4 are placed and held, and a push-up plate 6b that overlaps with the lower surface of the holding plate 6a.

The holding plate 6a is provided with a set of four positioning pins 6a1 as a holding structure for each of the formwork units 3 and 4. The positioning pins 6a1 face the side surfaces of the first formwork units 3 and 4 to regulate the positions of the paste-filled first formwork unit (paste-filled base end formwork unit) 3 and the paste-filled first formwork unit (paste-filled tip formwork unit) 4. Note that the positioning pins 6a1 located between adjacent paste-filled formwork units 3 and 4 are common to the holding structures of the adjacent paste-filled formwork units 3 and 4 in the examples of Figures 8 to 10. The holding structure is not limited to the structure shown in the figure, and is preferably a structure that can adequately hold the formwork units 3 and 4 in accordance with their shapes, such as a square column, flat plate, L-shaped angle, rail-shaped, etc., in addition to pins and cylinders.

Figure 8 shows the paste-filled first formwork unit (paste-filled base end formwork unit) 3 placed on the retaining plate 6a, and the paste-filled second formwork unit (paste-filled tip end formwork unit) 4 is placed on this paste-filled first formwork unit 3, as described below. It is also possible to place the paste-filled second formwork unit 4 on the retaining plate 6a and stack the paste-filled first formwork unit 3 on this paste-filled second formwork unit 4.

In addition, a through hole 6a2 that penetrates the holding plate 6a is provided in the center of the area where the paste filling formwork units 3 and 4 are located and is surrounded by four positioning pins 6a1 that position the paste filling formwork units 3 and 4.

The push-up plate 6b is provided with a push-up rod 6b1 that can be inserted into and removed from the through hole 6a2. When the holding plate 6a and the push-up plate 6b are stacked, the tip of the push-up rod 6b1 protrudes from the top surface of the holding plate 6a to an extent sufficient to perform the function described below. The dimensions, shape, and arrangement of the through hole 6a2 and the push-up rod 6b1 can be designed as appropriate to suit the desired shape of the blank and the circumstances of the arrangement when held by the holding plate 6a.

(2) Specific lamination method using lamination device A specific lamination method using the lamination device 6 will be described. First, the paste-filled first frame unit (paste-filled base frame unit) 3 is disposed at a position regulated by the positioning pin 6a1 of the holding plate 6a of the lamination device 6, with the closing side opening 3b facing the upper surface of the holding plate 6a, as shown in FIG. 8. In this embodiment, the first frame unit 3 is disposed at the lowermost layer in the vertical direction. Next, as shown in FIG. 1(A), the push-up rod 6b1 of the push-up plate 6b is inserted into the through hole 6a2 of the holding plate 6a, and the push-up plate 6b is brought close to the holding plate 5a. When the push-up plate 6b is overlapped with the holding plate 6a, the tip of the push-up rod 6b1 protrudes from the upper surface of the holding plate 6a and pushes up the extrusion plate 3a disposed in the first frame unit 3. As a result, as shown in FIG. 1(B) and FIG. 9, a part of the fluid paste P filled in the first frame unit 3 protrudes from the supply side opening 3c, and a convex curved paste joint surface Pa is formed. At this time, the amount of protrusion of the push-up rod 6b1 may be determined so that the fluid paste P protrudes to a position where it does not overflow or spill out of the first formwork unit 3.

As shown in FIG. 1(C), the supply side opening 4c is opposed to the supply side opening 3c of the paste-filled first form unit (paste-filled base end form unit) 3 with the paste joint surface Pa of the fluid paste P protruding, and the paste-filled second form unit (paste-filled tip form unit) 4 is pressed against the paste-filled first form unit (paste-filled base end form unit) 3. As a result, as shown in FIG. 1(D) and FIG. 10, both paste-filled form units are overlapped to form a connected form, and the paste-like polymerizable curable composition filled in both paste-filled form units is joined in the connected columnar cavity to form a paste laminate, and a "paste laminate-filled connected form" is obtained in which both end openings of the connected form are substantially blocked by the extrusion plate.

At this time, when the paste-filled second formwork unit (paste-filled tip formwork unit) 4 is stacked, the paste joint surface Pa of the fluid paste P protruding from the supply side opening 3c of the paste-filled first formwork unit (paste-filled base end formwork unit) 3 is pushed in by the paste joint surface Pa of the fluid paste P in the paste-filled second formwork unit (paste-filled tip formwork unit) 4, so the push-up rod 6b1 is lowered in advance to a position where it does not protrude from the upper surface of the holding plate 6a. This allows the fluid pastes P to be smoothly combined when both paste-filled formwork units are stacked. Moreover, since the paste joint surface Pa of the fluid paste P in the first formwork unit 3 protrudes, it is possible to prevent air from being mixed in between the paste joint surface Pa of the fluid paste P in the second formwork unit 4. Therefore, these fluid pastes can be reliably integrated. This allows the formation of a two-layer paste laminate with a regular interface inside the connecting formwork.

2-5. Step E (pressurizing step) and pressurizing device In step E (pressurizing step), the paste-filled interlocking form obtained in the previous step is pressed in the axial direction (stacking direction) of the cylindrical body.

In order to improve the interlayer adhesion of the fluid paste P bonded within the connected first formwork unit 3 and second formwork unit 4, and the adhesion between the paste P and the inner surface of the connected formwork, a process of applying pressure in the axial direction of the connected formwork units is carried out. There are no particular restrictions on the device used for applying pressure, but a method of applying pressure using a pressure part with a surface parallel to the closed side opening 3b or 4b of the connected formwork units is preferred.

For example, a form unit holding device 7, an example of which is shown in FIG. 11, can be used. The form unit holding device 7 is preferably used as a jig when subjecting the paste-filled connected form to process F (hardening process), and includes a pair of holding frames 7a, 7b that receive the form units 3, 4 of the paste-filled connected form. The pair of holding frames 7a, 7b are each formed in a shape that can hold the outer shape of the form unit in cross section, and are attached upright to the bottom plate 7c with their open sides facing each other. The paste-filled connected form can be held inside the holding frames 7a, 7b. A pressing block 7d that presses the paste-filled connected form against the bottom plate 7c is detachably attached to the upper part of the holding frames 7a, 7b. The pressing block 7d is fixed by a fixing means having a combination of bolts 7e and nuts 7f or other structure. As shown in FIG. 11, in addition to fixing a set of paste-filled connected form, it is also possible to fix a plurality of paste-filled connected form in a straight line or in a plane. When applying pressure using such a form unit holding device 7, pressure can be applied by tightening the nuts 7f, or by using a hydraulic press or the like to the paste-filled linked form held by the holding frames 7a and 7b without using the nuts 7f, via the unfixed pressing block 7d.

During pressure application, excess fluid paste P is exuded from at least a portion of the connecting portion of the connecting formwork unit and/or from at least a portion of the sliding contact portion between the connecting columnar cavity portion and the extrusion plates 3a and 4a, thereby efficiently improving the interlayer adhesion of the fluid paste P and the adhesion between the paste P and the inner surface of the connecting formwork. If the adhesion between the paste P and the inner surface of the connecting formwork is insufficient, a gap will be generated between the paste P and the inner surface of the connecting formwork, increasing the possibility that gases present in the atmosphere during polymerization or impurities present in the atmosphere will enter the paste P. As a result, there is an increased possibility that the aesthetics of the layer interface or surface properties of each layer of the hybrid resin laminate obtained after polymerization and hardening will be reduced, so this pressure application process is effective in improving the aesthetics of the hardened body.

The pressure applied to the interlocking formwork is preferably 0.024 to 0.60 MPa, more preferably 0.072 to 0.48 MPa, and even more preferably 0.12 to 0.36 MPa. In addition, the time for applying pressure to the interlocking formwork is preferably 1 to 120 minutes, more preferably 3 to 100 minutes, and even more preferably 5 to 60 minutes. In addition to the above pressure application conditions, it is preferable to apply pressure so that the time from when the pressure application part of the pressure application device or jig comes into contact with the interlocking formwork unit and pressure application begins until the maximum pressure is reached and the final pressure is reached is short. The time should be 120 seconds or less, but 60 seconds or less is preferable, and 30 seconds or less is even more preferable.

The interlocking formwork unit that has been pressurized in this manner is then subjected to process F (hardening process) while being fixed, for example, by a formwork unit holding device 7.

2-6. Step F (hardening step) and polymerization device In step F (hardening step), the paste laminate inside the connected columnar hollow portion of the paste-filled connected formwork pressurized in the previous step is hardened. The hardening at this time is performed by adopting a polymerization hardening method according to the type of polymerization initiator used, and the polymerization conditions may be appropriately determined according to the type of polymerization initiator used. From the viewpoint of being able to reliably polymerize a large number of paste-filled connected formworks, it is preferable to use a thermal polymerization initiator as the polymerization initiator and perform heat polymerization.

According to the inventors' research, when heat polymerization is carried out using resin-made formwork units, specifically thermoplastic resin or thermosetting resin with a heat-resistant temperature of 100°C or higher, it has been found that, depending on the heating conditions, slight air infiltration and poor curing can be observed at the joints of the formwork units in the linked formwork.

To prevent the occurrence of such a phenomenon, it is preferable to perform the hardening in step F (hardening step) by heating the paste laminate filled connected formwork that has been subjected to step E (pressurizing step) in a temperature increase pattern that sequentially performs steps 1 to 3 below.

Step 1: Maintaining a temperature within the range of 30°C or higher and 45°C or lower for at least 2 hours. Step 2: Maintaining a temperature within the range of 45°C or higher and 65°C or lower for at least 5 hours. Step 3: Maintaining a temperature within the range of 65°C or higher and 100°C or lower for at least 2 hours.

The holding time in each step may be any time that satisfies the above conditions, but for step 2, the longer the holding time within a certain range, the greater the effect, and it is preferable to set it to 8 to 90 hours, especially 10 to 80 hours. For step 3, it is preferable to set it to 2 to 20 hours, especially 3 to 18 hours. For step 1, it is preferable to set it to 2 to 10 hours, especially 2 to 7 hours. In the above steps, it is not necessary to keep the temperature constant during the holding time, and it is preferable to have a gradient in which the temperature gradually increases in the initial stage. For heating with such a heating pattern, it is possible to appropriately set a program that raises the temperature at a constant rate until a specified temperature is reached and holds the temperature, or a program that sets an initial temperature and a final temperature and performs gradient control between them, and these programs can also include a temperature lowering process as long as it is within a specified temperature range. Furthermore, for each step, these control methods may be used alone or in combination.

The mechanism by which the above-mentioned phenomenon, which can occur when using a resin formwork unit, is suppressed by adopting the above-mentioned heating pattern is not entirely clear, but it is believed that this is because the resin is now able to deform uniformly in response to the polymerization shrinkage during polymerization. This effect can be obtained regardless of whether or not the above-mentioned step E (pressurization step) is performed. In other words, even if step E is not performed (even if there is no effect from pressurization), a certain degree of effect of preventing slight air intrusion and poor curing can be obtained.

Because the effect of adopting the above-mentioned heating pattern is significant, when performing heat polymerization using the above-mentioned heating pattern, it is preferable to use the following resins as the resin mold unit with a heat resistance of 100°C or higher. That is, thermoplastic resins such as polypropylene, high-density polyethylene, polyacetal, and polycarbonate, thermosetting resins such as polyimide, polyamide, phenol, and melamine resin, and various (super) engineering plastics such as PEEK, PTFE, PEK, and PEKK are used, and general-purpose resins such as polypropylene and high-density polyethylene are preferable in terms of price and ease of handling during molding. These resins can be selected appropriately based on the ease of handling during manufacturing and the ease of pouring the fluid paste.

There are no restrictions on the atmosphere during curing, but it is preferable to heat the material in an inert gas atmosphere such as nitrogen to prevent color changes due to oxidation deterioration. There are no restrictions on the equipment used for the treatment as long as it can heat the cured material to the desired temperature, but in general, forced convection ovens are preferable to natural convection ovens because they provide a more uniform internal temperature. There are also no restrictions on the method for creating an inert gas atmosphere, but for example, a separate airtight container for containing the cured material may be used, or the oven itself may have an airtight structure to replace the internal atmosphere. Even if the oven is not airtight, a method of continuously flowing atmospheric gas may be used.

The pressure during curing may be normal pressure, but it is preferable to apply pressure of 0.1 MPa to 0.9 MPa, preferably 0.2 MPa to 0.6 MPa. Such thermal polymerization under pressure can be carried out using a heatable pressure vessel such as a pressure oven or autoclave.

The hardened two-layer fluid paste P is then removed from the mold units 3 and 4, and post-processing such as removing burrs and polishing to smooth the surface, surface preparation, printing, and heat treatment is carried out as necessary to produce the cut part consisting of a two-layer hybrid resin laminate.

Although an example of obtaining a hybrid resin laminate having a two-layer structure by the two-unit lamination method has been described above, it is also possible to obtain a hybrid resin laminate having a three-layer structure by the two-unit lamination method. For example, in the step B, in addition to the first and second fluid pastes, a third fluid paste is prepared, and in the step C, when preparing the paste-filled formwork unit, the first or second fluid paste is not fully filled in at least one of the formwork units, but is filled so that a certain thickness of unfilled portion remains, and the third fluid paste is filled in this unfilled portion, and the steps from D onwards are performed in the same manner, thereby obtaining a hybrid resin laminate having a three-layer structure. When filling with the third fluid paste, it is preferable to first make the surface of the fluid paste layer that serves as the base flat before carrying out the filling. If the layer thickness of the third fluid paste is thin, it is possible to prevent disturbances and defects from occurring at the lamination interface by filling the third fluid paste carefully after doing so. The third fluid paste may also be made into a sheet shape of the same thickness as the unfilled portion and filled in the unfilled portion. This method can also be applied to the three-unit lamination method described below, making it possible to obtain a hybrid resin laminate with more layers than the number of formwork units used.

2-7. Manufacturing of a dental blank using a hybrid resin laminate made of a hardened body obtained in the F step as a cutting part If necessary, as shown in FIG. 13, a blank holding pin 2 is bonded with an adhesive or the like to a cutting part made of a hybrid resin laminate of a two-layer structure obtained in the F step, and a dental blank 1 for cutting a dental prosthesis 10 as shown in FIG. 14 is produced. There is no particular restriction on the blank holding pin as long as it has a shape that allows the blank to be fixed to a cutting machine, and it may not be provided depending on the shape of the blank and the requirements of the processing machine. The blank holding pin is made of stainless steel, brass, aluminum, etc. The method of fixing the blank holding pin to the dental cutting resin material does not depend on the above-mentioned adhesion, and may be a method of fitting, screwing, etc., and there is no particular restriction on the above-mentioned adhesion method, and various commercially available adhesives such as isocyanate-based, epoxy-based, urethane-based, silicone-based, and acrylic-based adhesives can be used.

3. Regarding the "three or more unit lamination method" In the embodiment described in the above section 2, a "two-unit lamination method" (I) was described in which a form kit consisting of two form units is used, and each form unit is filled with one type of paste-like polymerizable curable composition to manufacture a dental machining blank 1 having a cut part consisting of a hybrid resin laminate having a two-layer structure. Here, a "three or more unit lamination method" is described, which is a method of manufacturing a dental machining blank 1 having a cut part consisting of a hybrid resin laminate having a laminate structure of three or more layers by using a form kit consisting of three or more form units, that is, a form kit having a base end form unit, a tip form unit, and at least one intermediate form unit disposed between these two form units, and filling each form unit with one type of paste-like polymerizable curable composition.

As mentioned above, the "three or more unit lamination method" is not significantly different from the "two unit lamination method" (I) except that step D includes steps Db1 to Db4. In addition, the difference in step D is summarized as follows: the extrusion plate that blocks one opening of the "paste laminate filled connected form" obtained in the "two unit lamination method" (I), in which both end openings of the connected form are substantially blocked by the extrusion plate, is removed to form a "partial paste laminate filled connected form", and a "paste filled form unit" is connected (laminate) on top of it. This is a connection (lamination) ⇒ "paste filled form unit" is created by one extrusion plate ⇒ connection (lamination) of the "paste filled form unit" and the "paste filled form unit" is obtained by repeating the operation of the above as many times as the number of intermediate form units. Therefore, the "three or more unit lamination method" will be described with reference to FIG. 12 for the case where the number of intermediate form units is one (the above operation is performed only once). FIG. 12 is a diagram that explains the lamination process when manufacturing a three-layered dental machining blank 1, and corresponds to FIG. 1.

When manufacturing a dental machining blank 1 having a three-layer structure, a first end frame unit (base end frame unit) 21 having an extrusion plate 21a and a second end frame unit (tip end frame unit) 22 having an extrusion plate 22a are prepared, similar to the base end frame unit 3 and tip end frame unit 4 described above. Between the first end frame unit 21 and the second end frame unit 22, an intermediate frame unit 23 is arranged. These three frame units 21 to 23 are connected to form a connected frame. In addition, the columnar cavities of each of these frame units 21 to 23 are connected to form a connected kit having connected columnar cavities. Note that the intermediate frame unit 23 does not have extrusion plates corresponding to the extrusion plates 21a and 22a. In other words, layers with different colors, etc. are formed in each of the first end frame unit 21, the second end frame unit 22, and the intermediate frame unit 23.

Then, in the same manner as described above, each of the form units 21 to 23 is filled with the fluid paste using the filler 5, and a paste-filled form unit is produced by each of the form units 21 to 23.

The process of stacking these form units 21 to 23 will be described with reference to FIG. 12. First, the first end form unit 21 is placed on the holding plate 6a of the stacking device 6, and the intermediate form unit 23 is stacked on the first end form unit 21. In this state, when the push-up plate 6b is brought close to the holding plate 6a and the upper end of the push-up rod 6b1 inserted in the through hole 6a2 is caused to protrude from the upper surface of the holding plate 6a, the push-up plate 21a of the first end form unit 21 is pushed up, as shown in FIG. 12(A). As a result, the fluid paste P in the first end form unit 21 protrudes upward, and further, the fluid paste P in the intermediate form unit 23 protrudes upward. Therefore, the upper surface of the part of the intermediate form unit 23 where the fluid paste P protrudes upward becomes the paste joint surface Pa. In addition, prior to stacking the intermediate form unit 23 on the first end form unit 21, it is preferable to push up the fluid paste P in the first end form unit 21 to form a paste joint surface Pa having a convex curved shape, etc., and then stack the fluid paste P in the intermediate form unit 23 on this, since air will not get mixed in between the paste joint surface Pa of the fluid paste P in the first end form unit 21 and the paste joint surface Pa of the fluid paste P in the intermediate form unit 23.

Next, as shown in Fig. 12(B) and Fig. 12(C), the extrusion plate of the intermediate form unit 23 stacked on the first end form unit 21 is removed to form a "partial paste laminate filled connected form", and then the second end form unit 22 is placed on top of it and pressed. At this time, as shown in Fig. 12(B), the push-up plate 6b is separated from the holding plate 6a to a position where the push-up rod 6b1 does not protrude from the upper surface of the holding plate 6a. In this state, the second end form unit 22 is pressed against the intermediate form unit 23. Therefore, as shown in Fig. 12(C), the fluid paste P in the first end form unit 21 and the fluid paste P in the intermediate form unit 23 are integrated, and further, the fluid paste P in the intermediate form unit 23 and the fluid paste P in the second end form unit 22 are integrated. This results in a three-layer structure with a regular interface.

The "paste laminate filled connected form" obtained in this way, that is, the form units 21 to 23 with a three-layer structure, are held in the form unit holding device 7 shown in FIG. 11, pressurized, and then hardened. This causes the fluid pastes P to become integrated and harden, forming a dental machining blank 1 with a three-layer structure.

Next, the hardened three-layer fluid paste is removed from the mold units 21-23, and post-processing such as removing burrs and polishing is performed as necessary to obtain a three-layered dental machining blank 1.

Then, by adhering a blank holding pin 2 to the manufactured dental machining blank 1 with adhesive or the like as shown in FIG. 13, the dental machining blank 1 is produced for cutting the dental prosthesis 10 as shown in FIG. 14.

Although FIG. 12 illustrates a dental machining blank 1 having a three-layer structure, when manufacturing a dental machining blank 1 having a four or more layer structure, a dental machining blank 1 having the desired layer structure can be manufactured by adding intermediate form units similar to intermediate form unit 23.

In addition, in this embodiment, the manufacturing equipment is described as including the filling tool 5, the stacking device 6, and the form unit holding device 7, but the equipment used in the filling process, stacking process, and hardening process is not limited to equipment having these structures.

The fluid pastes forming each layer can be of different colors and can have the properties required for a dental prosthesis 10 to be used in a missing tooth, allowing for a structure having layers with different properties.

Materials used in the manufacturing equipment can be appropriately selected and used according to the application. Examples include metal materials such as aluminum or aluminum alloys, stainless steel, iron, and brass; thermosetting or thermoplastic plastic materials such as polypropylene, polyethylene, urethane, POM, PEK, PEKK, and PEEK; elastomer materials such as silicone rubber; and ceramic materials. However, it is preferable to appropriately select well-known materials in addition to those described above according to the physical properties required for the parts to be used and the precision required for the parts.

In addition, it is preferable to perform post-processing of the device components as necessary. Post-processing such as polishing and surface treatment can improve the durability and functionality of the components.

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

Example 1
First, formwork units were prepared consisting of a base end formwork unit (first formwork unit) and a tip end base end formwork unit (second formwork unit) made of polypropylene, each of which had the same shape and had an internal columnar hollow portion measuring 18.5 mm x 15 mm x 9.5 mm (Step A).

Next, 20 parts by mass of a polymerizable monomer composition component consisting of 25% by mass of triethylene glycol dimethacrylate and 75% by mass of 1,6-bis(methacrylethyloxycarbonylamino)trimethylhexane, 80 parts by mass of inorganic filler, and 0.4 parts by mass of benzoyl peroxide, a thermal polymerization initiator, were mixed using a planetary mixer until uniform, and then vacuum degassed to prepare a fluid paste. As the inorganic filler, a mixture of equal parts by mass of spherical silica zirconia with an average particle size of 0.2 microns and spherical silica zirconia with an average particle size of 10 microns (both of which were surface-treated with γ-methacryloyloxypropyltrimethoxysilane) was used. The fluid paste thus obtained was divided into two, and different types of pigments were blended and kneaded to prepare a first fluid paste and a second fluid paste with different color tones (Step B).

An extrusion plate measuring 18.3 mm x 14.8 mm x 2.0 mm was inserted into each of the columnar hollows of the first and second formwork units so that it could be moved back and forth and attached and detached to block one end opening of each formwork unit, and then the first formwork unit was filled with the first fluid paste and the second formwork unit was filled with the second fluid paste using the filling device 5 shown in Figure 7 (A) (Step C), and then a paste laminate filled connected formwork was obtained using the method shown in Figure 1 using the stacking device 6 shown in Figure 8 (Step D).

The paste laminate filled interlocking formwork obtained in this manner was set in the formwork unit holding device 7 shown in Figure 11, and a pressure of 0.024 MPa was applied in the axial direction of the interlocking formwork for 5 minutes without tightening the nuts, to perform a pressure treatment (Step E).

Then, the set nuts were tightened to the form unit holding device 7 to fix the paste laminate filled connected form, and the form was heated, polymerized, and cured at normal pressure using an oven. The heating was performed using a temperature rise pattern of 2 hours at 40°C, 5 hours at 55°C, and two consecutive periods at 80°C (Process F).

After cooling to room temperature, the connected formwork was removed from the formwork unit holding device and the hardened body (hybrid resin laminate) inside was taken out. The layer interfaces and the surfaces of each layer of the resulting hybrid resin laminate were visually evaluated and rated according to the following criteria. The condition of the layer interfaces was rated B (almost no interface disturbance) and the overall air infiltration was rated 1 (roughness of the surface occurred, but acceptable).

Evaluation criteria for the state of the layer interface:
A: No interfacial disturbance at all. B: Almost no interfacial disturbance. C: Some interfacial disturbance is observed but is acceptable. D: Some interfacial disturbance is observed and falls below the acceptable range. E: The interfacial disturbance is extremely noticeable and falls significantly below the acceptable range.

Air infiltration rating criteria:
10: No air intrusion, and the surface is glossy. 5: No air intrusion, but the gloss is poor. 1: Some surface roughness has occurred, but it is tolerable. 0: Air has intruded, and the surface is significantly rough.
The evaluation criteria 6 to 9 are intermediate between the evaluation criteria 5 and 10, with the higher numerical value indicating a state closer to 10, and the evaluation criteria 2 to 4 are intermediate between the evaluation criteria 1 and 5, with the higher numerical value indicating a state closer to 5.

Comparative Example 1
A hybrid resin laminate was manufactured in the same manner as in Example 1, except that step E (pressurizing step) was not performed, and the condition of the layer interface was evaluated, resulting in an evaluation of E (interface disorder was extremely noticeable and significantly below the acceptable range).

Examples 2 to 15
A hybrid resin laminate was manufactured and evaluated in the same manner as in Example 1, except that the pressing conditions in step E (pressing step) were changed as shown in Table 1, and the heating conditions in step F (curing step) were changed to Step 1: 5 hours at 40°C, Step 2: 30 hours at 45-65°C, and Step 3: 15 hours at 80°C. The results are shown in Table 1. In the table, "↑" means "same as above."

Examples 16 to 28
A hybrid resin laminate was produced and evaluated in the same manner as in Example 1, except that the holding temperature and holding time conditions in each step in the process F (polymerization process) were changed as shown in Table 1. The results are shown in Table 1.

Examples 29 to 31
In these examples, the layer interface disorder was improved by including the pressurization process, but the use of a resin mold unit and the temperature rise conditions in the curing process were not optimal, so air intrusion into the entire surface through the gaps in the mold unit and curing failure occurred. That is, these are examples in which a hybrid resin laminate was manufactured in the same manner as in Example 1, except that the holding temperature and holding time conditions in each step in step F (polymerization process) were changed as shown in Table 3. The results of evaluations performed in the same manner as in Example 1 are shown in Table 3.

REFERENCE SIGNS LIST 1 dental processing block 1a first layer 1b second layer 2 blank holding pin 3 first form unit 3a push plate 3b closing side opening 3c supply side opening 4 second form unit 4a push plate 4b closing side opening 4c supply side opening 5 filling tool 5a holding plate 5a1 protrusion 5b positioning block 5b1 step 5c filling plate 5c1 support surface 5c2 paste flow path 5c3 paste flow path 5d form unit storage section 5e filling nozzle 6 stacking device 6a holding plate 6a1 positioning pin 6a2 through hole 6b push-up plate 6b1 push-up rod 7 form unit holding device 7a, 7b holding frame 7c bottom plate 7d pressing block 10 dental prosthesis 21 first end form unit 22 Second end form unit 23 Intermediate form unit 21a Extrusion plate 22a Extrusion plate P Fluid paste Pa Paste joining surface

Claims (8)

A method for producing a dental machining blank having a cutting portion made of a hardened paste laminate in which a plurality of layers made of a paste-like polymerizable curable composition containing a polymerizable monomer, an inorganic filler, and a polymerization initiator are laminated, comprising:
A: A step of preparing a form kit comprising a plurality of form units each composed of a cylindrical body having both ends open and a columnar hollow portion formed therein, the form kit being capable of forming a connected form having a connected cylindrical body and a connected columnar hollow portion formed by connecting the cylindrical bodies and the columnar hollow portions of each form unit, respectively, by connecting the plurality of form units in the axial direction of the cylindrical bodies;
B: A step of preparing a plurality of types of paste-like polymerizable and hardenable compositions to be filled into each of the plurality of frame units prepared in the above step;
C: A step of filling the paste-like polymerizable curable composition into each of the plurality of mold units prepared in the above step to prepare a plurality of paste-filled mold units;
D: A step of sequentially connecting the plurality of paste-filled form units obtained in the above step to form the connected form, and at the same time, bonding the paste-like polymerizable curable compositions filled in the paste-filled form units in the connected columnar hollow portions to form a paste laminate, thereby obtaining a paste laminate-filled connected form;
E: a pressurizing step of pressing the paste laminate filled connected form obtained in the above step in the axial direction of the cylindrical body; and F: a hardening step of hardening the paste laminate inside the connected columnar hollow portion pressurized in the above step to form a hardened body.
including,
A method for producing the dental machining blank, comprising the steps of: The method for manufacturing a dental machining blank according to claim 1, wherein in step B, paste-like polymerizable and hardening compositions having different color tones are prepared, and in step C, each mold unit is filled with a paste-like polymerizable and hardening composition having a different color tone. When the form kit is composed of two form units, one of which is a base end form unit and the other is a tip end form unit,
In the step C, for each of the base end form unit and the tip end form unit, an extrusion plate having a flat contact surface that comes into contact with the paste-like polymerizable curable composition filled in the columnar cavity and for extruding the filled paste-like polymerizable curable composition from the supply side opening, which is the opening on the other side, is inserted into the columnar cavity so as to be movable forward and backward and detachable, thereby blocking the closed side opening, which is an opening at one end of each form unit, and then the columnar cavity is densely filled with the paste-like polymerizable curable composition, thereby producing a paste-filled base end form unit and a paste-filled tip end form unit in which the closed side opening, which is the opening on one side, is blocked with the extrusion plate and a planar or substantially planar paste joint surface is formed at the supply side opening, which is the opening on the other side;
The step D comprises:
Da1: a step of moving an extrusion plate toward a supply side opening of at least one of the paste-filled base end form unit and the paste-filled tip end form unit to extrude a paste-like polymerizable curable composition and cause a part of the paste-like polymerizable curable composition to protrude from the supply side opening, thereby forming a paste joint surface in a convex curved shape; and Da2: a step of connecting both paste-filled form units after the step so that the paste joint surface of the paste-filled base end form unit and the paste joint surface of the paste-filled tip end form unit overlap each other to form a connected form, and connecting the paste-like polymerizable curable compositions filled in both paste-filled form units in the connected columnar hollow portion to form a paste laminate, thereby obtaining a paste laminate-filled connected form in which both end openings of the connected form are substantially blocked by the extrusion plate;
including,
A method for producing a dental machining blank according to claim 1 or 2. When the form kit is composed of three or more form units, the form units arranged at one end and the other end of the connecting form are respectively called a base end form unit and a tip end form unit, and the form unit arranged between these two form units is called an intermediate form unit,
In the step C, an extrusion plate having a flat contact surface that comes into contact with the paste-like polymerizable curable composition filled in the columnar cavity and for extruding the filled paste-like polymerizable curable composition from the opening on the other side is inserted into the columnar cavity so as to be freely movable back and forth and detachable, thereby closing one end opening of each frame unit, and then the columnar cavity is densely filled with the paste-like polymerizable curable composition, thereby producing a paste-filled base end frame unit, a paste-filled tip frame unit and a paste-filled intermediate end frame unit in which the closing side opening, which is the opening on one side, is closed with the extrusion plate and a planar or substantially planar paste joint surface is formed at the supply side opening, which is the opening on the other side;
The step D comprises:
Db1: A step of moving an extrusion plate toward a supply side opening of at least one of the paste-filled base end form unit and the paste-filled intermediate form unit disposed adjacent thereto to extrude a paste-like polymerizable curable composition, causing a part of the paste-like polymerizable curable composition to protrude from the supply side opening, thereby forming a paste joint surface in a convex curved shape;
Db2: after the above process, a process of overlapping the paste joint surface of the paste-filled base end form unit and the paste joint surface of the paste-filled intermediate form unit so as to overlap with each other to form a partially connected form consisting of a connected body of both form units, and inside the partially connected form, joining the paste-like polymerizable curable composition filled in both paste-filled form units to form a paste partial laminate, and then removing the extrusion plate blocking the closing side opening of the paste-filled intermediate form unit to obtain a partial paste laminate filled connected form having a planar or substantially planar paste joint surface with the closing side opening as a supply side opening of the partial connected form;
Db3: When there is no paste-filled intermediate form unit to be arranged adjacent to the partial paste laminate-filled connected form, the partial paste laminate-filled connected form obtained in the above step is used as the final partial paste laminate-filled connected form;
When there is a paste-filled intermediate form unit to be disposed adjacent to the partial paste laminate-filled connected form, the extrusion plate of the paste-filled base end form unit in the partial paste laminate-filled connected form and/or the extrusion plate of the paste-filled intermediate form unit to be disposed adjacent are moved toward the supply side opening to extrude the paste-like polymerizable curable composition until there are no more paste-filled intermediate form units to be disposed adjacent to the partial paste laminate-filled connected form, and the paste joint surface of at least one of the partial paste laminate-filled connected form and the paste-filled intermediate form unit to be disposed adjacent to the partial paste laminate-filled connected form is made convexly curved, and then the connection by overlapping the paste joint surfaces of both of them so that they overlap and the removal of the extrusion plate are repeated to obtain an extended partial paste laminate-filled connected form having a planar or substantially planar paste joint surface as a final partial paste laminate-filled connected form, in which the number of connected paste-filled intermediate form units and the number of layers of the formed paste partial laminate are increased; and Db4: a step of moving the extrusion plate of the paste-filled base end form unit and/or the extrusion plate of the paste-filled tip end form unit in the final portion paste laminate filled connected form obtained in the above step toward the supply side opening to extrude the paste-like polymerizable hardenable composition, forming a convex curved paste joint surface of at least one of the final portion paste laminate filled connected form and the paste-filled tip end form unit, and then overlapping the two paste joint surfaces so that they overlap to connect both paste filled form units to form a connected form, and at the same time , joining the paste-like polymerizable hardenable compositions filled in both paste filled form units in the connected columnar hollow portion to form a paste laminate, thereby obtaining a paste laminate filled connected form in which both end openings of the connected form are substantially blocked by the extrusion plate;
including,
A method for producing a dental machining blank according to claim 1 or 2. By applying pressure in the step E, excess paste-like polymerizable curable composition is exuded from at least a part of the connecting portion of the form unit in the paste laminate-filled connected form and/or from at least a part of the sliding contact portion between the connecting columnar hollow portion and both of the extrusion plates, thereby improving interlayer adhesion in the paste laminate and adhesion between the paste laminate and the inner surface of the connected form.
A method for producing a dental working blank according to claim 3 or 4. The method for manufacturing a dental machining blank according to claim 5, wherein the pressurization in step E (pressurization step) is performed by applying a pressure of 0.024 to 0.60 MPa for 1 to 120 minutes. The method for manufacturing the dental machining blank according to claim 4, further comprising a preliminary pressurizing step of pressurizing the partial paste laminate filled connecting form and/or the extended partial paste laminate filled connecting form in the axial direction of the cylindrical body at at least one timing selected from the group consisting of the timing after the completion of the step Db2 and the timing after the completion of the connection by overlapping, which is performed at least once in the step Db3, and before the removal of the extrusion plate. In the step B, a plurality of types of paste-like polymerizable curable compositions each containing a thermal polymerization initiator are prepared;
The paste laminate filled joint form that has been hardened in the step F (hardening step) and subjected to the step E (pressurizing step) is subjected to the following steps 1 to 3:
Step 1: maintain the temperature within the range of 30°C to 45°C for at least 2 hours; Step 2: maintain the temperature within the range of 45°C to 65°C for at least 5 hours; Step 3: maintain the temperature within the range of 65°C to 100°C for at least 2 hours.
A method for producing a dental processing blank according to any one of claims 1 to 7.