Dental bulk block for cutting and manufacturing method thereof

Abstract

A dental bulk block for cutting is disclosed, which is a glass ceramic block containing a crystalline phase in an amorphous glass matrix, the crystalline phase being lithium disilicate as the main crystalline phase, with no additional crystalline phase, the crystalline phase having an average particle size of 0.01 to 1.0 μm, and a crystallinity of 25 to 45%. This has the advantages of improving processability during cutting such as CAD / CAM in a high-strength workpiece having high bending strength, thereby reducing tool resistance and wear rate and increasing tool life, reducing chipping of edges during processing, and being able to manufacture dental restorations with different transparencies through a simple process of machining the block and varying post-heat treatment conditions, thereby realizing various shades and contributing to simplified logistics management.

Description

Technical Field

[0001] The present invention relates to a dental bulk block for cutting and a method for manufacturing the same, which can achieve various transparencies while being a high-strength workpiece. The present invention is a research result carried out with the support of the project for cultivating material, component, and equipment enterprises and supporting technological self-reliance in the Kihara Technopark.

Background Art

[0002] Materials and methods for fabricating artificial teeth using glass containing lithium disilicate crystals (monolithic dental crown) are already known in many patents. However, in the known technology, the size of the crystal phase is coarse, making machining difficult immediately. For machining, a method is adopted in which a machinable crystalline lithium metasilicate crystal phase is first formed and machined, and then a heat treatment is secondly carried out to form a high-strength lithium disilicate crystal phase. In this case, the dimensional accuracy is inferior due to shrinkage in the post-heat treatment process, and there is the annoyance of adding a heat treatment process. Generally, for prosthetic processing by CAD / CAM, the bulk body must be machined directly in the hospital to fabricate the prosthesis and this must be tried on the patient as soon as possible (one-day appointment), so the time delay due to the heat treatment process adds economic difficulties to the patient and the user.

[0003] In addition, conventional lithium disilicate crystallized glass materials have limitations in achieving a high light transmittance and opalescence similar to natural teeth due to the coarse crystal phase.

[0004] In particular, the conventional lithium disilicate crystallized glass material first produces a lithium metasilicate crystallized glass with good workability for processing, and after processing, lithium disilicate is formed through a secondary crystallization heat treatment to enhance the strength. At this time, the size of the crystal phase is about 3 μm or more, and in this state, the workability is significantly inferior, and only the strong part can be realized.

[0005] In order to solve such problems, the applicant of the present application has proposed a method for manufacturing a crystallized glass containing a lithium disilicate crystal phase and a silicate crystal phase with excellent workability by adjusting the crystal size by changing the temperature of the primary heat treatment, and has already received a patent (Patent Document 1: Korean Patent No. 10-1975548). Specifically, here, 60 to 83% by weight of SiO2, 10 to 15% by weight of Li2O, 2 to 6% by weight of P2O5 serving as a nucleating agent, 1 to 5% by weight of Al2O3 increasing the glass transition temperature and softening point and enhancing the chemical durability of the glass, 0.1 to 3% by weight of SrO increasing the softening point of the glass, 0.1 to 2% by weight of ZnO, 1 to 5% by weight of a colorant, and 2.5 to 6% by weight of Na2O + K2O which is an alkali metal oxide increasing the thermal expansion coefficient of the glass. For the glass composition containing, a step of performing a primary heat treatment at 400 °C to 850 °C and a step of performing a secondary heat treatment at 780 °C to 880 °C after the primary heat treatment are included, and a lithium disilicate crystal phase and a silica crystal phase with a nano size of 5 nm to 2000 nm are generated by the primary heat treatment, and the light transmittance is adjusted by the secondary heat treatment temperature. A method for manufacturing a crystallized glass for dental use containing a silica crystal phase is disclosed.

[0006] Here, the crystallized glass obtained by the primary crystallization heat treatment has a crystal phase size of 5 to 2000 nm, and in addition to the lithium disilicate crystal phase, a silica crystal phase precipitates, so it is a material that can be machined in a lithium disilicate state. In terms of the machining cutting force, it was confirmed that the primary crystallization heat treatment was preferably performed in the temperature range of 480 to 800 °C to have a lithium disilicate and silica crystal phase with a size of 30 to 500 nm.

[0007] The inventors of the present invention have explored a solution that can provide artificial teeth with improved physical properties and aesthetics through a simple post-heat treatment while improving the workability in machining performed by consumers such as doctors and dentists, using the result of primary crystallization heat treatment as a workpiece, and have arrived at the idea of the present invention.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention aims to provide a dental glass ceramic block that can exhibit excellent workability during cutting processes such as CAD / CAM even in a high-strength workpiece state while enabling adjustment of the translucency of the restoration through an additional heat treatment process.

Means for Solving the Problems

[0010] One embodiment of the present invention is a glass ceramic block containing a crystal phase within an amorphous glass matrix, wherein the crystal phase has a main crystal phase of lithium disilicate, no additional crystal phase, the size of the crystal phase has an average particle size of 0.01 to 1.0 μm, and the crystallinity is 25 to 45%, and provides a dental bulk block for cutting.

[0011] The dental bulk block for cutting according to a preferred embodiment has a biaxial flexure strength based on ISO6872 of 200 to 380 MPa and a fracture toughness of 1.7 to 2.1 MPa·m 1 / 2 and can be.

[0012] The dental bulk block for cutting according to one embodiment of the present invention can achieve an average light transmittance of 40 - 50% when heat-treated in the range of 811 - 820 °C for 1 minute to 1 hour.

[0013] The dental bulk block for cutting according to another embodiment of the present invention can achieve an average light transmittance of 30 - 40% when heat-treated in the range of 821 - 850 °C for 1 minute to 1 hour.

[0014] The dental bulk block for cutting according to another embodiment of the present invention can achieve an average light transmittance of 20 - 30% when heat-treated in the range of 851 - 880 °C for 1 minute to 1 hour.

[0015] In the dental bulk block for cutting according to the present invention, the glass matrix can contain 69.0 - 75.0 wt% of SiO₂, 12.0 - 14.0 wt% of Li₂O, 2.5 - 3.5 wt% of Al₂O₃, 0.12 - 0.22 wt% of ZnO, 1.1 - 2.7 wt% of K₂O, 0.1 - 0.3 wt% of Na₂O, and 2.0 - 6.0 wt% of P₂O₅.

[0016] Further, the present invention includes melting a glass composition containing 69.0 - 75.0 wt% of SiO₂, 12.0 - 14.0 wt% of Li₂O, 2.5 - 3.5 wt% of Al₂O₃, 0.12 - 0.22 wt% of ZnO, 1.1 - 2.7 wt% of K₂O, 0.1 - 0.3 wt% of Na₂O, and 2.0 - 6.0 wt% of P₂O₅, molding and cooling in a mold, and annealing at a predetermined rate from 465 °C to 280 °C for 20 minutes to 2 hours to produce a block of a predetermined shape,

[0017] and crystallizing and heat-treating the block starting from a furnace temperature of 300 °C to a maximum temperature of 755 - 810 °C for 30 minutes to 6 hours, and provides a method for manufacturing a dental bulk block for cutting.

[0018] Further, the present invention includes manufacturing a predetermined dental restoration by processing the dental bulk block for cutting according to the above embodiment using a processing machine. comprising a step of heat-treating a dental restoration to adjust its translucency; The step of adjusting the translucency is at least one step selected from a high translucency adjustment step of heat-treating at a temperature in the range of 811 to 820 °C for 1 minute to 1 hour, an intermediate translucency adjustment step of heat-treating at a temperature in the range of 821 to 850 °C for 1 minute to 1 hour, and a low translucency adjustment step of heat-treating at a temperature in the range of 851 to 880 °C for 1 minute to 1 hour, and provides a method for manufacturing a dental restoration.

[0019] Further, the present invention provides a dental restoration obtained by the manufacturing method of the above-described embodiment, which is a glass-ceramic body containing a crystal phase in an amorphous glass matrix, wherein the crystal phase has a main crystal phase of lithium disilicate, and the additional crystal phase contains at least one crystal phase selected from cristobalite, tridymite, quartz, spodumene, virgilite, and mixtures thereof, and has a biaxial flexural strength of at least 450 MPa.

[0020] In one embodiment, the dental restoration can be selected from a crown, an inlay, an onlay, and a veneer.

Advantages of the Invention

[0021] The dental bulk block according to the present invention is a high-strength workpiece with high flexural strength, and can improve workability during cutting processes such as CAD / CAM. Therefore, tool resistance and wear rate can be reduced, tool life can be increased, chipping at the edge during processing can be reduced, and by machining the block and subjecting it to different post-heat treatment conditions in a simple process, dental restorations with different transparencies can be manufactured, enabling the realization of various shades and contributing to the simplification of logistics management.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0023] The above-described and additional aspects of the present invention will become more apparent by preferred embodiments described with reference to the accompanying drawings. Hereinafter, it will be described in detail so that those skilled in the art can easily understand and reproduce it by such embodiments of the present invention.

[0024] One embodiment of the present invention is a glass-ceramic block containing a crystal phase in an amorphous glass matrix, wherein the crystal phase has a main crystal phase of lithium disilicate, no additional crystal phase, the size of the crystal phase is an average particle size of 0.01 to 1.0 μm, and the crystallinity is 25 to 45%, and provides a dental bulk block for cutting.

[0025] In the above and following descriptions, the term main crystal phase can be defined as a crystal phase occupying at least 80% by weight of all crystal phases, and the term additional crystal phase can be defined as the remaining crystal phases other than the main crystal phase among all crystal phases.

[0026] The content of the crystal phase can be calculated by X-ray diffraction analysis. As an example, in a test piece composed of two polymorphs a and b, the ratio Fa of the crystal phase a is quantitatively expressed by the following formula 1.

[0027]

Equation

[0028] This value can be determined by measuring the intensity ratio of two crystal phases and obtaining the integer K. K is the absolute intensity ratio I of two pure polymorphs oa / I ob and is determined by measuring a reference material.

[0029] In the above and following descriptions, the term "main crystal phase" can be defined as being set based on the content calculated by such a method.

[0030] In the above and following descriptions, the bulk block has no shape restrictions and can include bulk bodies in various forms such as block form, disk form, ingot form, cylinder form, etc. as an example.

[0031] The XRD analysis result graph for the bulk block according to a preferred embodiment is as shown in FIG. 1.

[0032] In FIG. 1, for the dental bulk block according to an embodiment of the present invention, the main crystal phase is lithium disilicate, and only the pure lithium disilicate crystal phase precipitates in the glass matrix, and its crystallinity reaches 25 - 45%. When considering the adjustment of transparency and workability by post - heat treatment, the dental bulk block of the present invention preferably can have a crystallinity of 25 - 45%.

[0033] In the above and following descriptions, "crystallinity" can be defined as the ratio of the crystal phase to the amorphous glass matrix, but since this can be determined by various methods, in one embodiment of the present invention, it is a value automatically calculated by an X - ray diffractometer.

[0034] In the above and following descriptions, the XRD analysis is understood as the result of analysis using an X-ray diffractometer (D / MAX-2500, manufactured by Rigaku Corporation, Japan; Cu Kα (40 kV, 60 mA), scanning speed: 6° / min, 2θ: 10 - 70 (degree), manufactured by Rigaku Corporation, Japan).

[0035] Such a crystal phase can be formed into microcrystals, which have the characteristic of being able to realize various mechanical properties and light transmittance while showing various sizes and size distributions according to temperature.

[0036] Also, as an example, FIG. 2 shows a scanning electron microscope (SEM) photograph of the dental bulk block of the present invention. The size of the crystal phase is an average particle size of 0.01 - 1.0 μm, and it has the characteristic that the crystal size is reduced by about 2.5 - 40 times compared with a conventional CAD / CAM workpiece having lithium metasilicate as the main crystal phase.

[0037] The average size of the crystal phase particles can be derived from the SEM photograph obtained in this way. Specifically, by drawing a diagonal line or a random straight line on the SEM photograph and dividing the number of crystal phases passed by the straight line by the length of the straight line and considering the magnification, it can be obtained by the linear intercept method. In the above and following descriptions, the size of the crystal phase is understood to be calculated according to such a method.

[0038] By satisfying such crystal size and crystallinity, the dental bulk block for cutting has a biaxial flexure strength of 200 - 380 MPa and a fracture toughness of 1.7 - 2.1 MPa·m based on ISO6872 1 / 2It can reach this, which generally meets physical properties improved by 10 - 15% compared to conventional CAD / CAM workpieces with lithium metasilicate as the main crystal phase, and thereby can exhibit the advantage of reducing chipping at the edge during processing by about 30% or more.

[0039] Characteristically, in the case of the dental bulk block obtained by the present invention, the resistance generated in the tool during processing can be significantly reduced when using a processing machine. As a specific example, it is a glass - ceramic block containing a crystal phase in an amorphous glass matrix as shown in FIGS. 1 and 2. With a size of 12×14×18 mm, the cutting time was measured while rotating at 250 RPM using a low - speed cutting machine (ISOMET low speed saw, manufactured by Buehler, Germany) and a diamond electroplated wheel (2514485H17, manufactured by Norton, USA). Then, the cutting time was measured for the most common lithium disilicate - based block (conventional lithium disilicate) (Rosetta SM, manufactured by HASS Corp), zirconia - reinforced lithium disilicate - based bulk block (Zirconia reinforced lithium disilicate, Celtra Duo, manufactured by DentsplySiron), and lithium aluminosilicate - reinforced lithium disilicate bulk block (LAS reinforced lithium disilicate, Nice, manufactured by Straumann) in the same way.

[0040] The cutting resistance (%) was calculated from the respective cutting time values obtained in this way. Specifically, taking the cutting time obtained for a general lithium disilicate block as 100%, the cutting time was converted into a relative percentage and calculated as each cutting resistance value. The results are shown in FIG. 3.

[0041] From the results of Fig. 3, the cutting resistance was the highest for general lithium disilicate blocks, followed by LAS (lithium alumino silicate) crystallized glass and zirconia-reinforced crystallized glass, and the block according to the present invention was the lowest. From such results, it can be confirmed that the glass-ceramic block of the present invention is the most machinable.

[0042] As described above, a glass-ceramic block containing a crystal phase in an amorphous glass matrix according to the present invention, wherein the crystal phase has a main crystal phase of lithium disilicate, no additional crystal phase, the size of the crystal phase is an average particle size of 0.01 to 1.0 μm, and the crystallinity is 25 to 45% can have the characteristic of being able to variously realize mechanical properties and light transmittance while the crystal phase shows various sizes and size distributions according to temperature.

[0043] As an example, a dental bulk block for cutting according to an embodiment of the present invention can achieve an average light transmittance of 40 to 50% when heat-treated in the range of 811 to 820 °C for 1 minute to 1 hour. When having such high translucency, it may be useful as an inlay or onlay, but is not limited thereto.

[0044] A dental bulk block for cutting according to another embodiment of the present invention can achieve an average light transmittance of 30 to 40% when heat-treated in the range of 821 to 850 °C for 1 minute to 1 hour. When satisfying such medium translucency, it may be useful for coloring applications, but is not limited thereto.

[0045] According to another embodiment of the present invention, a dental bulk block for cutting can achieve an average light transmittance of 20 to 30% when heat-treated in the range of 851 to 880 °C for 1 minute to 1 hour. When having such a low translucency, it may be useful for applications such as posterior crowns, but is not limited thereto.

[0046] The light transmittance in the above and following descriptions was measured using a UV-visible spectrometer (UV-2401PC, manufactured by Shimadzu Corporation, Japan).

[0047] To measure the light transmittance of the dental bulk block according to the present invention, the surface of the test piece was wiped clean with ethanol and measured using a UV-visible spectrometer (UV-2401PC, manufactured by Shimadzu Corporation, Japan). At this time, the measurement wavelength range was 300 to 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 in the entire wavelength range.

[0048] The graph of the change in the light transmittance of the bulk block by heat treatment temperature measured by such a method is as shown in FIG. 4.

[0049] On the other hand, in the dental bulk block for cutting according to the present invention, the glass matrix can contain 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.

[0050] The glass composition that constitutes such a glass matrix causes a crystal phase to precipitate in the amorphous glass matrix through nucleation and crystal growth heat treatment for crystallization. However, for the above-described glass matrix, the temperature at which nucleation and crystal growth occur corresponds to 500°C to 880°C. That is, nucleation begins at least at 500°C, and crystal growth occurs while the temperature is rising. This crystal growth exhibits the lowest light transmittance when used as an artificial tooth at a maximum of 880°C. That is, the light transmittance gradually decreases from the temperature at which crystals grow to a maximum of 880°C. When paying attention to such crystal growth, after causing crystal growth to an extent that satisfies workability enabling machining while satisfying high strength, machining is performed using one obtained bulk block. Then, if the transparency can be adjusted by varying the heat treatment conditions and taking into account the required trial fitting position and the color specific to the patient's teeth, ultimately, it can contribute to the simplification of logistics management.

[0051] Natural teeth have various transparencies not only for each individual tooth but also for all teeth, and the required transparency (translucency) can vary depending on the patient and the trial fitting position. Therefore, if such a change in transparency due to the heat treatment temperature can be variously realized as needed using one bulk block, it is possible to provide artificial teeth that satisfy various aesthetic requirements using a small number of workpieces.

[0052] From such a perspective, the present invention includes melting a glass composition containing 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, molding and cooling in a mold, and annealing at a predetermined rate from 465°C to 280°C for 20 minutes to 2 hours to produce a block having a predetermined shape.

[0053] And a step of subjecting the block to a crystallization heat treatment at a furnace temperature starting from 300°C to a maximum temperature of 755 to 810°C for 30 minutes to 6 hours, and provides a method for manufacturing a dental bulk block for cutting.

[0054] In a 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.

[0055] As the glass composition, Li2CO3 can also be added instead of Li2O, and carbon dioxide (CO2), which is the carbon (C) component of Li2CO3, is discharged as a gas during the glass melting process and escapes. Also, K2CO3 and Na2CO3 can be added instead of K2O and Na2O, respectively, in the alkali oxides, and carbon dioxide (CO2), which is the carbon (C) component of K2CO3 and Na2CO3, is discharged as a gas during the glass melting process and escapes.

[0056] Mixing uses a dry mixing process, and as the dry mixing process, a ball milling process or the like can be used. Considering the ball milling process specifically, the starting materials are loaded into a ball milling machine, and the ball milling machine is rotated at a constant speed to mechanically crush and uniformly mix the starting materials. The balls used in the ball milling machine can be balls made of ceramic materials such as zirconia and alumina. The sizes of the balls can be all the same or at least two or more sizes of balls can be used. Considering the target particle size, the size of the balls, the milling time, the rotational speed per minute of the ball milling machine, etc. are adjusted. As an example, considering the particle size, the size of the balls can be set in the range of about 1 mm to 30 mm, and the rotational speed of the ball milling machine can be set in the range of about 50 to 500 rpm. Ball milling is preferably carried out for 1 to 48 hours considering the target particle size and the like. By ball milling, the starting materials are crushed into fine-sized particles, having a uniform particle size and being uniformly mixed.

[0057] Put the mixed starting materials into a melting furnace, heat the melting furnace containing the starting materials to melt the starting materials. Here, melting means that the starting materials change into a substance state with the viscosity of a liquid state rather than a solid state. The melting furnace preferably consists of a substance with a low contact angle in order to have a high melting point while suppressing the phenomenon that the melt adheres, and for this purpose, it is preferably made of a substance such as platinum (Pt), DLC (diamond-like-carbon), chamotte, etc., or a melting furnace whose surface is coated with a substance such as platinum (Pt) or DLC (diamond-like-carbon).

[0058] Melting is preferably carried out at a normal pressure of 1400 - 2000 °C for 1 - 12 hours. When the melting temperature is less than 1400 °C, the starting materials may not be melted yet. When the melting temperature exceeds 2000 °C, excessive energy consumption is required and it is not economical. Therefore, it is preferable to melt at a temperature within the above-mentioned range. Also, when the melting time is too short, the starting materials cannot be melted sufficiently. When the melting time is too long, excessive energy consumption is required and it is not economical. The heating rate of the melting furnace is preferably about 5 - 50 °C / min. However, when the heating rate of the melting furnace is too slow, it takes a long time and the productivity is poor. When the heating rate of the melting furnace is too fast, the volatilization amount of the starting materials increases due to a rapid temperature rise, and there is a possibility that the physical properties of the crystallized glass are not good. Therefore, it is preferable to raise the temperature of the melting furnace at a heating rate within the above-mentioned range. Melting is preferably carried out in an oxidizing atmosphere such as oxygen (O2) or air.

[0059] Pour the melt into a forming mold defined to obtain crystallized glass for dental cusp with a desired shape and size. The forming mold preferably consists of a substance with a high melting point while having a large strength and a low contact angle in order to suppress the phenomenon that the glass melt adheres. For this purpose, it is made of a substance such as graphite or carbon, and it is preferably preheated at 200 - 300 °C to prevent thermal shock and then pour the melt into the forming mold.

[0060] Since the melt in the forming mold is formed and cooled, it is preferable to go through a step of slow cooling (annealing) at a predetermined rate of 20 minutes to 2 hours from 465 °C to 280 °C after the cooling process. The predetermined rate at this time is preferably 1.6 °C / min to 10 °C / min.

[0061] Going through such a slow cooling step can reduce the stress deviation in the formed article, preferably making the stress non-existent, and can preferably affect the size control of the crystal phase and the improvement of the homogeneity of the crystal distribution in the subsequent crystallization step. Transfer the formed article that has gone through such a slow cooling process to a crystallization heat treatment firing furnace to cause nucleation and crystal growth to produce the target crystallized glass.

[0062] At this time, the crystallization heat treatment is carried out starting from a furnace temperature of 300 °C to a maximum temperature of 755 - 810 °C for 30 minutes to 6 hours, whereby a bulk block containing a crystal phase having only pure lithium disilicate as the crystal phase and the crystal size of 0.01 - 1.0 μm can be obtained.

[0063] The dental bulk block obtained by such a method can exhibit the characteristic that the light transparency of the material varies depending on the heat treatment temperature range.

[0064] In the case of a bulk-shaped block, it is used as a workpiece for machining such as CAD / CAM machining. However, conventional crystallized glass generally has a coarse crystal size, making it difficult to adjust the light transmittance, and is also strong in strength and difficult to machine. In contrast, the block of the present invention contains microcrystals, which can show various sizes and size distributions according to the temperature, and the physical properties and transparency can appear in various ways respectively. Therefore, after manufacturing a block from one glass composition reflecting such points, the transparency according to the heat treatment conditions can be controlled after machining the obtained block.

[0065] In this regard, the present invention includes a step of manufacturing a predetermined dental restoration by processing a dental bulk block for cutting according to the above-described embodiment using a processing machine, and a step of heat-treating the dental restoration to adjust translucency. The step of adjusting translucency includes at least one step selected from a high translucency adjustment step of heat-treating at a temperature in the range of 811 to 820 °C for 1 minute to 1 hour, an intermediate translucency adjustment step of heat-treating at a temperature in the range of 821 to 850 °C for 1 minute to 1 hour, and a low translucency adjustment step of heat-treating at a temperature in the range of 851 to 880 °C for 1 minute to 1 hour. The present invention provides a method for manufacturing a dental restoration.

[0066] By exhibiting the characteristics as shown in FIG. 4, the dental restoration according to the present invention can obtain a dental restoration having a low translucency to a high translucency (including an intermediate opacity) through one block, thereby realizing more than 80 different shades.

[0067] The dental restoration thus obtained is a glass-ceramic body containing a crystal phase in an amorphous glass matrix. The crystal phase has a main crystal phase of lithium disilicate, and the additional crystal phase can include at least one crystal phase selected from cristobalite, tridymite, quartz, spodumene, virgilite, and mixtures thereof. It has a biaxial flexural strength of at least 450 MPa and can provide various dental restorations with adjusted transparency according to the position or patient as described above. Thereby, it is possible to provide a tooth restoration with improved aesthetics by realizing various transparencies while withstanding the occlusal force of the molar region.

[0068] In the above and following descriptions, the dental restoration can be selected from a crown, inlay, onlay, and veneer, but is not limited thereto.

[0069] The present invention has been described with reference to one embodiment shown in the drawings, which is merely exemplary, and various modifications and other equivalent embodiments are possible for those having ordinary knowledge in the art.

Industrial Applicability

[0070] The present invention relates to a dental bulk block for cutting and a method for manufacturing the same, which can achieve various transparencies while being a high-strength workpiece.

[0071] The dental bulk block according to the present invention is a high-strength workpiece with high flexural strength, and can improve the workability during cutting such as CAD / CAM. Therefore, it can reduce the tool resistance and wear rate, increase the tool life, reduce the chipping of the edge part during processing, and manufacture dental restorations with different transparencies by a simple process of machining the block and varying the post-heat treatment conditions, thereby achieving various shades and contributing to the simplification of logistics management.

Claims

1. A glass-ceramic block containing a crystal phase within an amorphous glass matrix, wherein the crystal phase has a main crystal phase of lithium disilicate and no additional crystal phase, the size of the crystal phase has an average particle size of 0.01 to 1.0 μm, the degree of crystallinity is 25 to 45%, and the amorphous glass matrix contains 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. A dental bulk block for cutting, characterized by the above.

2. The biaxial flexure strength based on ISO 6872 is 200 to 380 MPa, and the fracture toughness is 1.7 to 2.1 MPa·m １／２ is The dental bulk block for cutting according to Claim 1.

3. When heat-treated in the range of 811 to 820 °C for 1 minute to 1 hour, an average light transmittance of 40 to 50% is achieved. The dental bulk block for cutting according to Claim 1.

4. When heat-treated in the range of 821 to 850 °C for 1 minute to 1 hour, an average light transmittance of 30 to 40% is achieved. The dental bulk block for cutting according to Claim 1.

5. When heat-treated in the range of 851 to 880 °C for 1 minute to 1 hour, an average light transmittance of 20 to 30% is achieved. The dental bulk block for cutting according to Claim 1.

6. SiO ２ 69.0 to 75.0 wt%, Li ２ O 12.0 to 14.0 wt%, Al ２ O ３ 2.5 to 3.5 wt%, ZnO 0.12 to 0.22 wt%, K ２ O 1.1 to 2.7 wt%, Na ２ O 0.1 to 0.3 and P ２ O ５ A step of melting a glass composition containing 2.0 to 6.0 wt%, molding and cooling it in a mold, and annealing it at a predetermined rate from 465 °C to 280 °C for 20 minutes to 2 hours to produce a block of a predetermined shape, The method for manufacturing a dental bulk block for cutting, comprising the step of subjecting the block to a crystallization heat treatment starting from a furnace temperature of 300 °C to a maximum temperature of 755 to 810 °C for 30 minutes to 6 hours. Characterized by the above.

7. Manufacturing a predetermined dental restoration by processing the dental bulk block for cutting according to Claim 1 using a processing machine, and heat-treating the dental restoration to adjust the light transmittance, wherein the step of adjusting the light transmittance is at least one step selected from a high light transmittance adjustment step of heat-treating in the range of 811 to 820 °C for 1 minute to 1 hour, an intermediate light transmittance adjustment step of heat-treating in the range of 821 to 850 °C for 1 minute to 1 hour, and a low light transmittance adjustment step of heat-treating in the range of 851 to 880 °C for 1 minute to 1 hour. Characterized by the above.

8. A glass-ceramic body containing a crystal phase within an amorphous glass matrix, The crystalline phase includes a main crystalline phase of lithium disilicate, and an additional crystalline phase includes at least one crystalline phase selected from cristobalite, tridymite, quartz, spodumene, virgilite, and mixtures thereof. The amorphous glass matrix includes 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. The biaxial flexural strength is at least 450 MPa. A dental restoration characterized by the above.

9. The dental restoration is selected from a crown, an inlay, an onlay, and a veneer. The dental restoration according to claim 8.

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