Large area blank for prosthetic production and its manufacturing method

Abstract

The present invention discloses a large-area blank in which, in an X-ray diffraction analysis pattern using CuKα radiation, no crystalline phase peak is present within the range of 2θ10 to 70, and the crystallinity is 0.00%, but SEM analysis confirms that crystalline particles with an average particle size of 10 to 70 nm are dispersed in an amorphous SiO2-Li2O-Al2O3-based glass matrix, and the length of the major axis is at least 60 mm and the thickness is at least 6 mm. This is a workpiece that is large in area but has excellent processability, and since it can improve processability during cutting, it can reduce tool resistance and wear rate and increase tool life, and it can reduce chipping of the edges during processing. It can improve the utilization efficiency of the blank when a plurality of dental restorations are intermittently or sequentially manufactured using one blank as needed, and it can improve productivity in manufacturing dental restorations. The processed dental restorations can be manufactured into high-strength dental restorations with different transparencies through a simple process with different post-heat treatment conditions, and since dental restorations realizing various shades can be manufactured using one blank, it has the advantage of contributing to simplified logistics management.

Description

[Technical Field]

[0001] The present invention relates to a large-area blank that allows a large number of prostheses to be manufactured from a single blank, and in particular to a large-area blank that has excellent machinability, and a method for manufacturing the same. [Background technology]

[0002] Numerous patents have already been published regarding materials and methods for fabricating monolithic dental crowns using glasses containing lithium disilicate crystals. However, these conventional techniques involve forming a machinable crystalline lithium metasilicate phase, processing it, and then heat-treating it to form a high-strength lithium disilicate phase. However, this process results in shrinkage during the post-heat treatment process, which reduces dimensional accuracy and requires additional heat treatment steps. Generally, CAD / CAM-based prosthetic fabrication requires a hospital to directly machine a bulk prosthesis and then perform a one-day appointment to fit the prosthesis as quickly as possible. Therefore, the time delays associated with the heat treatment process create financial difficulties for patients and users.

[0003] In addition, existing lithium disilicate glass-ceramic materials have limitations in achieving high light transmittance and opalescence similar to those of natural teeth due to the coarse crystalline phase.

[0004] In particular, existing lithium disilicate glass-ceramics materials are primarily made into lithium metasilicate glass-ceramics, which are easy to process, and then undergo a secondary crystallization heat treatment to form lithium disilicate, which increases strength. At this point, the size of the crystalline phase is approximately 3 μm or larger, which significantly reduces processability and only achieves strength.

[0005] To solve this problem, the applicant proposed a method for manufacturing crystallized glass containing lithium disilicate crystal phase and silicate crystal phase, which has excellent processability, by adjusting the crystal size through temperature change in the primary heat treatment, and has already received a patent (Korean Patent Registration No. 10-1975548). Specifically, the present disclosure discloses a method for producing dental crystallized glass, which includes the steps of subjecting a glass composition containing 60-83 wt% SiO2, 10-15 wt% Li2O, 2-6 wt% P2O5 which acts as a nucleating agent, 1-5 wt% Al2O3 which increases the glass transition temperature and softening point and also improves the chemical durability of the glass, 0.1-3 wt% Sr which increases the softening point of the glass, 0.1-2 wt% ZnO, 1-5 wt% colorant, and 2.5-6 wt% of a mixture of alkali metal oxides Na2O and K2O which increases the thermal expansion coefficient of the glass, to a primary heat treatment at 400°C to 850°C, and then subjecting the primary heat treatment to a secondary heat treatment at 780°C to 880°C. The primary heat treatment produces nano-sized lithium disilicate and silica crystal phases of 5 nm to 2000 nm, and the translucency is adjusted by the temperature of the secondary heat treatment. Furthermore, it was confirmed that the crystallized glass obtained by the primary crystallization heat treatment has a crystalline phase size of 5 to 2000 nm, and that due to the precipitation of a silica crystalline phase in addition to the lithium disilicate crystalline phase, it is a material that can be machined in the lithium disilicate state, and that in terms of machining cutting force, it has lithium disilicate and silica crystalline phases of size 30 to 500 nm when subjected to the primary crystallization heat treatment preferably in the temperature range of 480 to 800°C.

[0006] Using this lithium disilicate glass-ceramics as a workpiece, it has been possible to improve the workability in machining performed by consumers, such as doctors and dental technicians, while providing artificial teeth with improved physical properties and aesthetics through a simple post-heat treatment. The workpiece here is typically a blank in the form of a block, which has shown favorable results in terms of machinability when used in a form in which a single prosthesis can be obtained through a single block. However, when this is actually provided as a large-area blank, for example, a large-area blank with a diameter of 60 mm or more and a thickness of 6 mm or more, there is a limit to the workability that can be achieved through machining equivalent to that of a block.

[0007] In particular, in the case of such large-area blanks, processability is an important factor in realizing the purpose for which the main consumers, artisans, require large-area blanks. If processability is not fully realized, the utilization efficiency of the large-area blanks will decrease significantly, making it difficult to achieve the purpose of increasing the area of ​​the blanks. Furthermore, if workability is reduced, large-scale craftsmen, who are the main consumers of large-area blanks, may have to replace their processing burrs more quickly, resulting in a decrease in productivity.

[0008] One of the reasons why the same material can differ in workability when made larger is the machining environment. When a single block is processed into a single prosthesis, wet grinding can be used. However, when making large-area blanks, multiple prostheses must be produced intermittently or sequentially from a single blank as needed. This makes it difficult to use the grinding method in the early stages of processing, and requires the use of a mill. This increases the stress on the burrs and changes the way the burrs contact the blank.

[0009] Therefore, the inventors have made great efforts to manufacture a large-area blank that is easy to process and that can easily realize a prosthesis that satisfies the mechanical characteristics and aesthetics of a prosthesis made primarily of lithium disilicate glass ceramics. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention seeks to provide a large-area blank that is excellent in workability. The present invention aims to provide a method for producing a large-area blank with excellent workability by controlling the heat treatment conditions using a specific glass composition. The present invention aims to provide a method for manufacturing a prosthesis that achieves high strength while controlling translucency by machining a large-area blank to obtain a preform, and then through subsequent heat treatment, converting lithium disilicate-based crystals into the main crystals. [Means for solving the problem]

[0011] One embodiment of the present invention provides a large-area blank having a major axis length of at least 60 mm and a thickness of at least 6 mm, in which an X-ray diffraction analysis pattern using CuKα radiation shows no crystalline phase peaks within the 2θ (degree) range of 10 to 70, indicating a crystallinity of 0.00%, but SEM analysis confirms that crystalline particles with an average particle size of 10 to 70 nm are dispersed within an amorphous SiO2-Li2O-Al2O3-based glass matrix.

[0012] In the large-area blank according to one embodiment of the present invention, the SiO-LiO-AlO glass matrix may have an amorphous bump in the X-ray diffraction analysis pattern using CuKα radiation within the range of 2θ (degrees) 21 to 22.

[0013] In the large-area blank according to the present invention, the length of the major axis may be 60 to 150 mm, and the thickness may be 6 to 20 mm.

[0014] In the large-area blank according to the present invention, the SiO2-Li2O-Al2O3-based glass matrix may contain 69.0 to 75.0% by weight of SiO2, 12.0 to 14.0% by weight of Li2O, 2.5 to 3.5% by weight of Al2O3, 0.12 to 0.22% by weight of ZnO, 1.1 to 2.7% by weight of K2O, 0.1 to 0.3% by weight of Na2O, and 2.0 to 6.0% by weight of P2O5.

[0015] Large area blanks according to the invention may have an optical transmittance of at least 80% at a wavelength of 550 nm based on a thickness of 1.2 mm.

[0016] Preferably, the large area blank may have a light transmittance of 80-90% at a wavelength of 550 nm based on a thickness of 1.2 mm.

[0017] The present invention also provides a method for producing a pre-blank of a predetermined shape having a major axis length of at least 60 mm and a thickness of at least 6 mm, comprising the steps of melting a glass composition comprising 69.0 to 75.0 wt% SiO2, 12.0 to 14.0 wt% Li2O, 2.5 to 3.5 wt% Al2O3, 0.12 to 0.22 wt% ZnO, 1.1 to 2.7 wt% K2O, 0.1 to 0.3 wt% Na2O, and 2.0 to 6.0 wt% P2O5, forming the glass composition in a mold, cooling the glass, and annealing the glass composition at a predetermined rate from 465°C to 280°C for 20 minutes to 2 hours;

[0018] and heat treating the preliminary blank in a furnace starting from a temperature of 300°C and increasing to a maximum temperature of 400 to 500°C for 1 to 24 hours.

[0019] The present invention also provides a method for manufacturing a predetermined dental restoration by machining the large-area blank according to the embodiment; and heat treating the dental restoration to adjust its translucency;

[0020] The method for manufacturing a dental restoration is provided, wherein the translucency adjusting step is at least one step selected from a high translucency adjusting step in which heat treatment is performed at a maximum temperature in the range of 790°C or more but less than 810°C for 5 to 30 minutes, a medium translucency adjusting step in which heat treatment is performed at a maximum temperature in the range of 810°C or more but less than 825°C for 5 to 30 minutes, a low translucency adjusting step in which heat treatment is performed at a maximum temperature in the range of 825°C or more but less than 845°C for 5 to 30 minutes, and a medium opacity adjusting step in which heat treatment is performed at a maximum temperature in the range of 845°C or more but less than 860°C for 5 to 30 minutes.

[0021] In the method for manufacturing a dental restoration according to another embodiment of the present invention, the high light transmittance adjusting step may be a step of achieving an average light transmittance of 45 to 55%. In the method for manufacturing a dental restoration according to another embodiment of the present invention, the intermediate translucency adjustment step may be a step of achieving an average light transmittance of 35 to 44%. In the method for manufacturing a dental restoration according to another embodiment of the present invention, the low light transmittance adjusting step may be a step of achieving an average light transmittance of 18 to 34%. In the method for manufacturing a dental restoration according to another embodiment of the present invention, the semi-translucency adjusting step may be a step of achieving an average light transmittance of 13 to 17%.

[0022] The present invention also provides a dental restoration obtainable by the manufacturing method of the above embodiment, the dental restoration comprising a crystalline phase in an amorphous glass matrix, wherein the crystalline phase comprises lithium disilicate as a predominant crystalline phase and at least one additional crystalline phase selected from the group consisting of cristobalite, tridymite, quartz, eucryptite, spodumene, virgilite, and mixtures thereof, and wherein the biaxial flexural strength of the dental restoration is at least 380 MPa.

[0023] In one embodiment, the dental restoration may be selected from a crown, an inlay, an onlay, and a veneer. [Effects of the Invention]

[0024] The large-area blank according to the present invention is a workpiece that is large in area yet has excellent machinability. It can improve machinability during cutting, thereby reducing tool resistance and wear rate and increasing tool life. It can also reduce chipping at the edges during machining. It can also improve blank utilization efficiency when a single blank is used to manufacture multiple dental restorations intermittently or sequentially as needed, thereby improving productivity during dental restoration manufacture. The processed dental restorations can be manufactured into high-strength dental restorations with different transparencies through a simple process with different post-heat treatment conditions. This allows dental restorations with various shades to be manufactured using a single blank, which has the advantage of contributing to simplified logistics management. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a graph showing the results of X-ray diffraction analysis of a large-area blank of the present invention. [Figure 2] 1 is a scanning electron microscope (SEM) photograph showing the microstructure and crystalline phase size of a large area blank of the present invention. [Figure 3] 1 is a graph of transmission measurements for a large area blank of the present invention. [Figure 4] 1 is a comparative graph of cutting resistance for large area blanks of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The above and additional aspects of the present invention will become more apparent through the description of preferred embodiments with reference to the accompanying drawings. The following detailed description will enable those skilled in the art to easily understand and realize the present invention through such embodiments.

[0027] One embodiment of the present invention provides a large-area blank having a major axis length of at least 60 mm and a thickness of at least 6 mm, in which an X-ray diffraction analysis pattern using CuKα radiation shows no crystalline phase peaks within the 2θ (degree) range of 10 to 70, indicating a crystallinity of 0.00%, but SEM analysis confirms that crystalline particles with an average particle size of 10 to 70 nm are dispersed within an amorphous SiO2-Li2O-Al2O3-based glass matrix.

[0028] In particular, in the large-area blank of the present invention, the amorphous SiO2-LiO-Al2O3-based glass matrix may have an amorphous bump in the range of 2θ (degrees) 21 to 22, specifically 21.9 to 22.0, in an X-ray diffraction analysis pattern using CuKα radiation.

[0029] In the above and following descriptions, X-ray diffraction analysis is defined as the results of analysis using an X-ray diffraction analyzer (D / MAX-2500, Rigaku Corporation, Japan; CuKα (40 kV, 60 mA), scanning rate: 6° / min, 2θ: 10 to 70 (degrees), Rigaku Corporation, Japan).

[0030] In the above and following descriptions, "crystallinity" can be defined as the ratio of a crystalline phase to an amorphous glass matrix, but since this can be determined by various methods, in one embodiment of the present invention, it is defined as a value automatically calculated by the X-ray diffraction analysis defined above.

[0031] The XRD analysis result graph for a large area blank according to a preferred embodiment is shown in FIG.

[0032] As shown in FIG. 1, in the case of the large-area blank according to the present invention, there is no peak of a crystalline phase in the range of 2θ10 to 70 in the X-ray diffraction analysis pattern, and the crystallinity is 0.00%. From these results, it can be predicted that no crystalline phase exists in the body due to the amorphous SiO2-Li2O-Al2O3-based glass matrix.

[0033] Generally, a variety of crystalline phases can be present in a glass composition that realizes a SiO-LiO-AlO-based glass matrix, examples of which include lithium phosphate, lithium (meta)silicate, lithium disilicate, cristobalite, tridymite, quartz, eucryptite, spodumene, virgilite, etc. In particular, the main crystalline phase can usually include lithium (meta)silicate or lithium disilicate.

[0034] However, in the case of the large-area blank according to the present invention, there are no peaks of any crystalline phase other than the amorphous peaks that can be determined by the amorphous SiO2-Li2O-Al2O3-based glass matrix, and the crystallinity related to the content of such crystalline matter is 0.00%, which suggests that the blank is made of pure amorphous glass with no crystalline matter at all. However, the large-area blank according to the present invention exhibits a different behavior from glass made only of an amorphous SiO2-Li2O-Al2O3-based glass matrix, and this difference can be confirmed by the results of SEM analysis.

[0035] FIG. 2 is an SEM image (magnification of ×100K) of a large area blank of the present invention, which clearly shows the presence of particles. From the SEM observation results shown in FIG. 2, it can be confirmed that particles with an average particle size of 10 to 70 nm are dispersed.

[0036] The average size of crystalline phase particles can be derived from SEM photographs. Specifically, this can be determined by the linear intercept method, in which diagonal or random lines are drawn on the SEM photograph, the number of crystalline phases that the lines pass through is divided by the length of the lines, and the result is calculated taking into account the magnification. In the above and following descriptions, the average grain size of the crystalline phase is understood to be calculated by such a method.

[0037] The large-area blank according to the present invention shows the results of comparing the X-ray diffraction analysis pattern shown in FIG. 1 with the SEM observation image shown in FIG. 2. These characteristics can be inferred in various cases. For example, this may be a state in which fine, non-stoichiometric crystalline structures with low crystallinity or amorphous structure are formed, which corresponds to the initial stage of glass crystallization. Although fine particles are observed in the SEM observation image shown in FIG. 2, no crystalline phase peaks are detected in the X-ray diffraction analysis pattern shown in FIG. 1, and it can be predicted that the crystallinity is specifically analyzed to be 0.00%. However, the mechanism for these characteristics is not limited thereto, and this unexplained mechanism is not intended to limit the technical significance of the large-area blank according to the present invention.

[0038] Due to the specific structure associated with the elucidation of the inter-arranged particles, the large-area blank of the present invention, despite its large area with specifications of at least 60 mm in major axis length and at least 6 mm in thickness, can be expected to exhibit excellent workability in machining using mill equipment, particularly in dry milling where a single large-area blank is used to cut multiple dental restorations intermittently or sequentially as needed.

[0039] In particular, as can be seen from the SEM image in Figure 2, particles with an average particle size of 10 to 70 nm are dispersed within the glass matrix, and this is an extremely fine crystalline phase, with crystal sizes 50 to 300 times smaller than those found in conventional CAD / CAM workpieces (ingots and block products, not large-area blanks), which typically have lithium metasilicate as the main crystalline phase. It can be estimated that this extremely fine crystalline phase had a significant impact on the workability of large-area blanks.

[0040] In the above and following descriptions, the shape of the large-area blank is not limited, and because there is no such shape limitation, it is described using the term "major axis" instead of the term "diameter," and when taking into account the length and thickness of the major axis, it may have an outer shape that is usually called a disk.

[0041] In a preferred embodiment of the present invention, the large-area blank has a major axis length of 60 to 150 mm and a thickness of 6 to 20 mm, which is preferable in that this reduces the occurrence of defects in machining and provides compatibility for mass processing of the blanks.

[0042] On the other hand, a large-area blank according to a preferred embodiment of the present invention has an amorphous SiO2-Li2O-Al2O3-based glass matrix specifically containing 69.0 to 75.0 wt% SiO2, 12.0 to 14.0 wt% Li2O, 2.5 to 3.5 wt% Al2O3, 0.12 to 0.22 wt% ZnO, 1.1 to 2.7 wt% K2O, 0.1 to 0.3 wt% Na2O, and 2.0 to 6.0 wt% P2O5. This large-area blank has excellent workability despite being a large-area blank, and is preferable in terms of machining the large-area blank to obtain a dental restoration, which can then be subjected to a simple heat treatment to produce a dental restoration that satisfies the desired strength and aesthetics.

[0043] Furthermore, the large-area blank according to the present invention preferably has a light transmittance of at least 80% at a wavelength of 550 nm based on a thickness of 1.2 mm, and more preferably at least 80-90% at a wavelength of 550 nm based on a thickness of 1.2 mm, because it has excellent machinability, the transmittance of the dental restoration obtained by machining can be easily controlled, and the desired aesthetics can be achieved. More specifically, the large-area blank exhibiting such light transmittance is preferably formed of extremely fine crystal particles, which then exhibit various sizes and size distributions depending on the temperature, thereby providing dental restorations with a variety of mechanical properties and light transmittance.

[0044] FIG. 3 shows a graph of the measured light transmission of a large area blank according to the present invention. Characteristically, in the case of the large-area blank obtained by the present invention, when it is processed using a processing machine, the resistance generated in the tool during processing can be significantly reduced. As a specific example, a large-area blank having the characteristics shown in Figures 1 and 2 was processed in the shape of a dental premolar using a dental processing machine (PM-5, PISTIS, Korea), and the degree of tool wear was measured. The measurement results are shown in Figure 4.

[0045] From the results in Figure 4, it was confirmed that the large-area blank of the present invention, despite its large area, had a tool life that was 75% longer than that of an existing large-area blank of the same specification made of crystallized glass with lithium disilicate as the main crystalline phase (manufactured using our own block material), and that it was machined without chipping at the edges.

[0046] Meanwhile, as described above, the large-area blank according to the present invention may have a glass matrix containing 69.0 to 75.0 wt% SiO, 12.0 to 14.0 wt% LiO, 2.5 to 3.5 wt% AlO, 0.12 to 0.22 wt% ZnO, 1.1 to 2.7 wt% KO, 0.1 to 0.3 wt% NaO, and 2.0 to 6.0 wt% PO. The glass composition constituting such a glass matrix undergoes a crystal nucleation and crystal growth heat treatment to precipitate a crystalline phase within the amorphous glass matrix. The temperature at which the crystal nuclei and crystal growth occur for the above-described glass matrix falls within the range of 400°C to 880°C. That is, crystal nuclei begin to form at a minimum of 400°C, and crystal growth occurs as the temperature rises. This crystal growth reaches a maximum of 880°C, which exhibits the lowest optical transparency when used as an artificial tooth. In other words, since the translucency gradually decreases from the crystal growth temperature up to a maximum of 880°C, if we take this crystal growth behavior into consideration, we can obtain a bulk block by growing crystals that have high strength while also having workability that allows machining. Then, we can use one of the obtained bulk blocks to machine it, and then adjust the transparency by various post-heat treatment conditions to take into account the required trial position or the unique color of the patient's teeth. This will ultimately contribute to simplifying logistics management.

[0047] Since natural teeth, not only individual teeth but all teeth, have different translucencies, and the required translucency varies depending on the patient and the trial position, if it were possible to achieve various changes in transparency depending on the heat treatment temperature using a single bulk block, it would be possible to provide artificial teeth that meet various aesthetic requirements using a small amount of work.Furthermore, in the case of a large-area blank that can produce many artificial teeth from a single blank, it would of course contribute greatly to simplifying logistics management.

[0048] From this perspective, the present invention provides a method for manufacturing a large-area blank, comprising the steps of melting a glass composition containing 69.0 to 75.0 wt% SiO2, 12.0 to 14.0 wt% Li2O, 2.5 to 3.5 wt% Al2O3, 0.12 to 0.22 wt% ZnO, 1.1 to 2.7 wt% KO2O, 0.1 to 0.3 wt% Na2O, and 2.0 to 6.0 wt% PO5, forming the glass composition in a mold, cooling the glass composition, and annealing the glass composition from 465°C to 280°C at a predetermined rate for 20 minutes to 2 hours, thereby producing a blank having a predetermined shape with a long axis length of at least 60 mm and a thickness of at least 6 mm, and heat-treating the blank in a furnace starting at a temperature of 300°C and increasing to a maximum temperature of 400 to 500°C for 1 to 24 hours.

[0049] In one specific embodiment of the present invention, first, a glass composition containing 69.0 to 75.0 wt% of SiO2, 12.0 to 14.0 wt% of Li2O, 2.5 to 3.5 wt% of Al2O3, 0.12 to 0.22 wt% of ZnO, 1.1 to 2.7 wt% of K2O, 0.1 to 0.3 wt% of Na2O, and 2.0 to 6.0 wt% of P2O5 is weighed and mixed.

[0050] Li2CO3 may be added to the glass composition instead of Li2O, and carbon dioxide (CO2), which is the carbon (C) component of Li2CO3, is released as a gas and escapes during the glass melting process. Also, K2CO3 and Na2CO3 may be added to the alkali oxides instead of K2O and Na2CO3, respectively, and carbon dioxide (CO2), which is the carbon (C) component of K2CO3 and Na2CO3, is released as a gas and escapes during the glass melting process.

[0051] The mixing is performed using a dry mixing process, which may be a ball milling process. Specifically, the starting materials are loaded into a ball milling machine, which rotates at a constant speed to mechanically pulverize and uniformly mix the starting materials. The balls used in the ball milling machine may be made of ceramic materials such as zirconia or alumina, and the balls may all be the same size or may have at least two different sizes. The ball size, milling time, and ball mill rotation speed per minute are adjusted based on the target particle size. For example, the ball size may be set to a range of approximately 1 mm to 30 mm, and the ball mill rotation speed may be set to a range of approximately 50 to 500 rpm. The ball milling is preferably performed for 1 to 48 hours, based on the target particle size. The starting materials are pulverized into fine particles with a uniform particle size and uniform mixing.

[0052] The mixed starting materials are placed in a melting furnace, which is then heated to melt the starting materials. Melting refers to the process of converting the starting materials from a solid state to a viscous liquid state. The melting furnace is preferably made of a material that has a high melting point, high strength, and a low contact angle to prevent the molten material from sticking together. For this reason, the melting furnace is preferably made of a material such as platinum (Pt), diamond-like carbon (DLC), or chamotte, or is coated with a material such as platinum (Pt) or diamond-like carbon (DLC).

[0053] Melting is preferably carried out at 1,400 to 2,000°C under normal pressure for 1 to 12 hours. If the melting temperature is below 1,400°C, the starting materials may not yet be melted. If the melting temperature is above 2,000°C, excessive energy consumption is required, which is uneconomical. Therefore, melting within the above-mentioned temperature range is preferred. Furthermore, if the melting time is too short, the starting materials may not be fully melted, while if the melting time is too long, excessive energy consumption is required, which is uneconomical. The temperature rise rate of the melting furnace is preferably approximately 5°C / min to 50°C / min. However, if the temperature rise rate of the melting furnace is too slow, it takes too long and productivity decreases. If the temperature rise rate of the melting furnace is too fast, the sudden temperature rise may increase the amount of volatilization of the starting materials, resulting in poor physical properties of the crystallized glass. Therefore, it is preferable to raise the temperature of the melting furnace at a rate within the above-mentioned range. Melting is preferably carried out in an oxidizing atmosphere such as oxygen (O2) or air.

[0054] The melt is poured into a mold to obtain the desired shape and size of dental crystallized glass. The mold is preferably made of a material that has a high melting point, high strength, and a low contact angle to prevent the glass melt from sticking to it. For this purpose, the mold is preferably made of a material such as graphite or carbon, and is preferably preheated to 200 to 300°C to prevent thermal shock before pouring the melt into the mold.

[0055] As the molten material in the mold is shaped and cooled, it is preferable to carry out an annealing step after the cooling process, in which the temperature is gradually reduced from 465°C to 280°C for 20 minutes to 2 hours at a predetermined rate, preferably 1.5°C / min to 10°C / min.

[0056] This slow cooling step reduces stress variations within the molded product, preferably eliminating stress, which can have a desirable effect on controlling the size of the crystalline phase and improving the uniformity of the crystal distribution in the subsequent crystallization step.

[0057] The molded product (a preliminary blank with a major axis length of at least 60 mm and a thickness of at least 6 mm) that has undergone this slow cooling process is transferred to a crystallization heat treatment furnace for nucleation and crystal growth to produce the desired crystallized glass.

[0058] The crystallization heat treatment is carried out by heating the blank in a furnace starting at 300°C and increasing the maximum temperature to 400-500°C for 1-24 hours. As a result, an X-ray diffraction analysis pattern using CuKα radiation shows no crystalline phase peaks within the 2θ10-70 range, indicating a crystallinity of 0.00%, but SEM analysis confirms that crystalline particles with an average particle size of 10-70 nm are dispersed within an amorphous SiO2-Li2CO-Al2O3-based glass matrix, resulting in a large-area blank with a major axis length of at least 60 mm and a thickness of at least 6 mm.

[0059] In this case, the heat treatment is performed for 1 to 24 hours starting from a furnace temperature of 300°C and increasing to a maximum temperature of 400 to 500°C. If the temperature range is higher or the heat treatment time is longer, the machinability of the resulting large-area blank may decrease and the light transmittance may fall outside the desired range, which is undesirable.

[0060] As described above, in the X-ray diffraction analysis pattern using CuKα radiation according to the present invention, no crystalline phase peaks are present within the 2θ range of 10-70°, and the crystallinity is 0.00%. However, SEM analysis confirms that crystalline particles with an average particle size of 10-70 nm are dispersed within an amorphous SiO2-Li2O-Al2O3-based glass matrix. Large-area blanks with a major axis length of at least 60 mm and a thickness of at least 6 mm have the property that the crystalline phase exhibits various sizes and size distributions depending on the temperature, thereby realizing diverse mechanical properties and optical transparency.

[0061] The large-area blank obtained by this method can exhibit different optical transparency properties depending on the temperature range of the heat treatment.

[0062] Large-area blanks are used as workpieces for machining such as CAD / CAM processing. Conventional glass-ceramics generally have coarse crystal sizes, making it difficult to control translucency, and are strong and difficult to process. In contrast, the large-area blanks of the present invention contain extremely fine crystals, which can exhibit various sizes and size distributions depending on the temperature, resulting in various physical properties and transparency. Taking these factors into consideration, large-area blanks are manufactured from a single glass composition, and the resulting large-area blanks are then machined, and the transparency of the resulting product can be controlled depending on the heat treatment conditions.

[0063] However, in the case of the large-area blank according to the present invention, since it is designed with processability in mind, it is preferable that the realization of various mechanical properties and optical transparency is carried out after the blank is fabricated into a dental restoration.

[0064] From this perspective, the present invention provides a method for manufacturing a dental restoration, comprising the steps of manufacturing a predetermined dental restoration by cutting the large-area blank according to one embodiment, and heat-treating the dental restoration to adjust its translucency, wherein the step of adjusting the translucency is at least one step selected from a high translucency adjusting step of heat-treating at a maximum temperature of 790°C or more but less than 810°C for 5 to 30 minutes, a medium translucency adjusting step of heat-treating at a maximum temperature of 810°C or more but less than 825°C for 5 to 30 minutes, a low translucency adjusting step of heat-treating at a maximum temperature of 825°C or more but less than 845°C for 5 to 30 minutes, and a semi-translucency adjusting step of heat-treating at a maximum temperature of 845°C or more but less than 860°C for 5 to 30 minutes.

[0065] For example, after a large-area blank is machined to obtain a desired dental restoration, a high translucency adjustment step is performed in which the restoration is heat-treated for 5 to 30 minutes at a maximum temperature of 790°C or higher but lower than 810°C, achieving an average light transmittance of 45 to 55%. Dental restorations with such high translucency may be useful as inlays or onlays, but are not limited to these.

[0066] A large-area blank according to another embodiment of the present invention can achieve an average light transmittance of 35 to 44% through an intermediate translucency adjustment step in which the blank is heat-treated for 5 to 30 minutes at a maximum temperature of 810°C or higher but lower than 825°C. Dental restorations that satisfy this medium translucency may be useful for coloring applications, but are not limited thereto.

[0067] A large-area blank according to another embodiment of the present invention can achieve an average light transmittance of 18 to 34% through a low translucency adjustment step in which the blank is heat-treated for 5 to 30 minutes at a maximum temperature of 825°C or higher but lower than 845°C. Such low translucency may be useful for applications such as posterior crowns, but is not limited thereto.

[0068] A large-area blank according to another embodiment of the present invention can achieve an average light transmittance of 13 to 17% through a translucency adjustment step in which the blank is heat-treated at a maximum temperature in the range of 845°C to 860°C for 5 to 30 minutes. Dental restorations with such translucency (medium opacity) may be useful for applications such as, but not limited to, restoring discolored teeth. In the above and following descriptions, the light transmittance was measured using a UV-visible spectrometer (UV-2401PC, Shimadzu Corporation, Japan).

[0069] To measure the light transmittance of the large-area blank and dental restoration according to the present invention, the surface of the specimen was wiped clean with ethanol and measured using a UV-visible spectrometer (UV-2401PC, Shimadzu Corporation, Japan). The measurement wavelength range was 300-800 nm, and the slit width was 2.0 nm. The average light transmittance can be defined as the average value of the light transmittance values ​​over the entire wavelength range. In the above and following descriptions, the light transmittance can be defined as a value based on a specimen thickness of 1.2 mm.

[0070] The dental restorations according to the present invention can be machined and then heat-treated to achieve the various light transmittances described above, allowing a large number of dental restorations to be produced from a single blank. Furthermore, dental restorations with low to high translucency (including intermediate opacity) can be produced, making it possible to realize more than 80 different shades. The resulting dental restorations can be provided in trial positions or with various transparency settings tailored to the patient. This makes it possible to provide dental restorations that can withstand the occlusal forces of molars while achieving a variety of transparencies and improving aesthetics.

[0071] According to the present invention, through this manufacturing method, a dental restoration can be obtained, which is a glass-ceramic body comprising a crystalline phase in an amorphous glass matrix, wherein the crystalline phase comprises a primary crystalline phase of lithium disilicate and at least one additional crystalline phase selected from the group consisting of cristobalite, tridymite, quartz, eucryptite, spodumene, virgilite, and mixtures thereof, and has a biaxial flexural strength of at least 380 MPa.

[0072] In the above and following descriptions, the term "main crystalline phase" is defined as a crystalline phase that accounts for at least 80% by weight of the total crystalline phase, and the term "additional crystalline phase" can be defined as the remaining crystalline phase of the total crystalline phase that is not the main crystalline phase.

[0073] The content of the crystalline phase can be calculated by X-ray diffraction analysis. For example, in a specimen consisting of two polymorphic phases a and b, the ratio F of the crystalline phase a is a is quantitatively expressed by the following equation 1.

[0074] TIFF0007813491000001.tif26166

[0075] This value can be determined by measuring the intensity ratio of the two crystalline phases and obtaining a constant, K, which is the absolute intensity ratio, I, of the two pure polymorphic forms. oa / I ob and is determined by measuring a standard substance. In the above and following descriptions, the term "main crystalline phase" can be defined as being set based on the content calculated by this method. The biaxial flexure strength here is the biaxial flexure strength based on ISO6872.

[0076] In order to confirm the change in biaxial bending strength depending on the heat treatment conditions, test specimens with a diameter of 11.9 mm and a thickness of 1.18 mm were prepared from the large-area blanks described above, and then post-heat treated them under different heat treatment conditions to obtain different test specimens. The biaxial bending strength of each test specimen was measured according to ISO 6872, and the results are shown in Tables 1 to 4 below.

[0077] In Tables 1 to 4 below, for the specimens classified by heat treatment conditions, HT indicates a specimen obtained by heat treatment for 5 to 30 minutes at a maximum temperature of 790°C or more but less than 810°C, MT indicates a specimen obtained by heat treatment for 5 to 30 minutes at a maximum temperature of 810°C or more but less than 825°C, LT indicates a specimen obtained by heat treatment for 5 to 30 minutes at a maximum temperature of 825°C or more but less than 845°C, and MO indicates a specimen obtained by heat treatment for 5 to 30 minutes at a maximum temperature of 845°C or more but less than 860°C.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] [Table 4]

[0082] As shown in Tables 1 to 4, in the case of the large-area blank according to the present invention, the strength can be controlled depending on the conditions of the post-heat treatment after cutting, and it can be seen that such strength can satisfy the appropriate level for dental restorations.

[0083] In the above and following description, the dental restoration may be selected from, but is not limited to, a crown, an inlay, an onlay, and a veneer.

[0084] The present invention has been described with reference to one embodiment shown in the drawings, but this is by way of example only, and various modifications and equivalent alternative embodiments will be apparent to those skilled in the art. [Industrial Applicability]

[0085] The present invention relates to a large-area blank that allows a large number of prostheses to be manufactured from a single blank, and in particular to a large-area blank that has excellent machinability, and a method for manufacturing the same.

[0086] The large-area blank according to the present invention is a workpiece that is large in area yet has excellent machinability. It can improve machinability during cutting, thereby reducing tool resistance and wear rate and increasing tool life. It can also reduce chipping at the edges during machining. It can also improve blank utilization efficiency when a single blank is used to manufacture multiple dental restorations intermittently or sequentially as needed, thereby improving productivity in the manufacture of dental restorations. The processed dental restorations can be manufactured into high-strength dental restorations with different transparencies through a simple process with different post-heat treatment conditions. Therefore, dental restorations with various shades can be manufactured using a single blank, which has the advantage of contributing to simplified logistics management.

Claims

1. In the X-ray diffraction analysis pattern using CuKα rays, there is no peak of a crystalline phase within the range of 2θ (degrees) 10 to 70, and the crystallinity is 0.00%, but in the analysis by SEM, crystalline particles with an average particle size of 10 to 70 nm are present in the amorphous SiO ２ -Li ２ O-Al ２ O ３ It was confirmed that the nanoparticles were dispersed in the glass matrix. a major axis length of at least 60 mm and a thickness of at least 6 mm; The amorphous SiO 2 —Li 2 O—Al 2 O 3 based glass matrix contains 69.0 to 75.0 wt % of SiO 2 , 12.0 to 14.0 wt % of Li 2 O, 2.5 to 3.5 wt % of Al 2 O 3 , 0.12 to 0.22 wt % of ZnO, 1.1 to 2.7 wt % of K 2 O, 0.1 to 0.3 wt % of Na 2 O, and 2.0 to 6.0 wt % of P 2 O 5 . A large area blank characterized by:

2. SiO ２ -Li ２ O-Al ２ O ３ The glass matrix has an amorphous bump in the X-ray diffraction pattern in the range of 2θ (degrees) 21 to 22 in a CuKα ray diffraction analysis pattern. The large area blank of claim 1 .

3. The length of the major axis is 60 to 150 mm, and the thickness is 6 to 20 mm. The large area blank of claim 1 .

4. 1.2 mm thickness, light transmittance at wavelength of 550 nm is at least 80% The large area blank of claim 1 .

5. The light transmittance is 80-90% at a wavelength of 550 nm based on a thickness of 1.2 mm.

5. The large area blank according to claim 1 or 4.

6. A method for manufacturing a large-area blank according to claim 1, comprising: SiO ２ 69.0-75.0% by weight, Li ２ O12.0-14.0% by weight, Al ２ O ３ 2.5-3.5% by weight, ZnO 0.12-0.22% by weight, K ２ O1.1-2.7% by weight, Na ２ O 0.1 to 0.3 wt % and P ２ O ５ 2.0-6.0 wt. % of a glass composition, melting the glass composition in a mold, forming and cooling the glass composition in a mold, and annealing the glass composition at a predetermined rate from 465°C to 280°C for 20 minutes to 2 hours to produce a blank of a predetermined shape having a major axis length of at least 60 mm and a thickness of at least 6 mm; and heat treating the blank in a furnace for 1 hour to 24 hours starting at a temperature of 300°C and increasing to a maximum temperature of 400-500°C. A method for manufacturing a large-area blank.

7. A step of manufacturing a predetermined dental restoration by machining the large-area blank according to claim 1; and heat treating the dental restoration to adjust its translucency; The step of adjusting the translucency is a high translucency adjusting step of performing heat treatment at a maximum temperature of 790°C or higher and lower than 810°C for 5 minutes to 30 minutes; an intermediate translucency adjusting step of heat treating the substrate at a maximum temperature of 810°C or higher but lower than 825°C for 5 to 30 minutes; A low translucency adjusting step of heat treating the substrate at a maximum temperature of 825°C or higher and lower than 845°C for 5 to 30 minutes; and and a semi-permeability adjusting step in which the glass is heat-treated at a maximum temperature in the range of 845°C to 860°C for 5 to 30 minutes. A method for manufacturing a dental restoration, comprising:

8. The high light transmittance adjustment step is a step to achieve an average light transmittance of 45-55%. A method for producing a dental restoration according to claim 7.

9. The intermediate translucency adjustment step is a step to achieve an average light transmittance of 35-44%. A method for producing a dental restoration according to claim 7.

10. The low light transmittance adjustment step is a step to achieve an average light transmittance of 18 to 34%. A method for producing a dental restoration according to claim 7.

11. The semi-translucent adjustment step is a step to achieve an average light transmittance of 13 to 17%. A method for producing a dental restoration according to claim 7.

12. A glass-ceramic body obtained by the manufacturing method according to any one of claims 7 to 11, comprising a crystalline phase in an amorphous glass matrix, The crystalline phase comprises a main crystalline phase being lithium disilicate, and an additional crystalline phase comprising at least one crystalline phase selected from cristobalite, tridymite, quartz, eucryptite, spodumene, virgilite, and mixtures thereof; Biaxial bending strength is at least 380 MPa A dental restoration characterized by:

13. The dental restoration is selected from crowns, inlays, onlays and veneers.

13. A dental restoration according to claim 12.

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