CN115996688A

CN115996688A - Dental block and method for manufacturing same

Info

Publication number: CN115996688A
Application number: CN202180012222.3A
Authority: CN
Inventors: 林炯奉; 金容寿
Original assignee: HASS CO Ltd
Current assignee: HASS CO Ltd
Priority date: 2021-06-15
Filing date: 2021-06-15
Publication date: 2023-04-21
Also published as: AU2021451277A1; WO2022265129A1; JP2023534777A; CA3221037A1; BR112023026201A2

Abstract

The present invention discloses a dental block which is a glass ceramic block comprising a crystalline phase in an amorphous glass matrix, wherein the main crystalline phase comprises lithium disilicate, the additional crystalline phase comprises petalite (petalite), the gradient of the main crystalline phase is provided with a gradient of the main crystalline phase size relative to the depth, and a functional gradient material of which the gradient value of the main crystalline phase size is changed is free from interfaces, namely, a dental block required for cutting processing, and the dental block can be effectively used for manufacturing an artificial dental prosthesis which is aesthetically similar to natural teeth.

Description

Dental block and method for manufacturing same

Technical Field

The present invention relates to a dental block useful for manufacturing artificial teeth having structural characteristics similar to those of natural teeth, and a method for manufacturing the same, particularly to improve machinability.

Background

Crown material meansThe restorative materials for repairing damaged portions corresponding to dentin and enamel of teeth can be classified into inlays, onlays, veneers, crowns, and the like according to the applicable sites. The place where the crown material is used for restoration is the outer surface of the tooth, which is required to have high aesthetic properties, and high strength due to fracture such as abrasion or chipping (chipping) with the orthodontic tooth. Materials currently used as crown materials include leucite crystal-glass (leucite glass-ceramics), tempered porcelain or fluorapatite (Ca) ₅ (PO ₄ ) ₃ F) Crystallized glass has excellent aesthetic properties, but has a low strength of only 80 to 120MPa and has a high possibility of cracking. Therefore, research is currently being conducted to develop high-strength dental crown materials of various materials.

Lithium silicate crystal glasses were described in 1973 by Marcus P.Borom and Anna M.Turkalo (The Pacific Coast Regional Meeting, the American Ceramic Society, san Francisco, calif., october 31,1973 (Glass division, no. 3-G-73P)).

By Li ₂ O-Al ₂ O ₃ -SiO ₂ -Li ₂ O-K ₂ O-B ₂ O ₃ -P ₂ O ₅ The system glass was studied for crystal phase and strength according to various crystal nucleus formation and growth heat treatment conditions. The apparent strength of the crystal phase from low-temperature lithium metasilicate to high-temperature lithium metasilicate is 30-35 KPS, which is caused by the matrix glass, mother glass and Li ₂ SiO ₅ 、Li ₂ SiO ₃ Residual stress resulting from differences in the coefficients of thermal expansion of the phases.

Materials and methods for making artificial teeth using glasses containing lithium disilicate crystals (monolithic dental crown: monolithic crowns) are disclosed in various patents. However, the known technique is a method of forming a lithium metasilicate crystal phase (machinable crystalline: processable crystal) by performing a second heat treatment after processing and then forming a high-strength lithium metasilicate crystal phase because the crystal phase size is relatively large, and it is difficult to directly perform mechanical processing, and this method is complicated because the accuracy is lowered by a post heat treatment step and the heat treatment step is increased. The prosthesis processing usually performed by CAD/CAM is to directly process the block in a hospital and manufacture the prosthesis, and to process the patient (one-day appointment) in the fastest time, so that the time delay due to the heat treatment process causes economic difficulties for the patient and the user.

The existing lithium disilicate glass ceramic material is because its crystalline phase is coarse, and its light transmittance or opalescence (opalescence) cannot reach a height similar to that of natural teeth.

In particular, in the conventional lithium disilicate glass ceramic material, for processing, first, a lithium metasilicate (lithium metasilicate) glass ceramic having excellent processability is produced, and after processing, the glass ceramic is subjected to a secondary crystallization heat treatment to form lithium disilicate, thereby enhancing the strength, and in this state, the size of the crystal phase is about 3 μm or more, and in this state, the processability is remarkably reduced, and only the strength is enhanced.

In order to solve these problems, the present applicant has proposed a method of manufacturing a glass ceramic containing a lithium disilicate crystal phase and a silicate crystal phase with good workability by adjusting the crystal size by changing the temperature of the first heat treatment, and has obtained a patent (korean patent registration 10-1975548). Specifically, disclosed is a method for producing a glass ceramic for teeth, which comprises the steps of: will contain SiO ₂ 60 to 83 weight percent of Li ₂ O10-15 wt% and P as nucleating agent ₂ O ₅ 2 to 6 weight percent of Al which increases the glass transition temperature and glass softening point and enhances the chemical durability of the glass ₂ O ₃ 1 to 5 weight percent of SrO 0.1 to 3 weight percent, znO 0.1 to 2 weight percent, colorant 1 to 5 weight percent, and alkali metal oxide Na which increases the thermal expansion coefficient of the glass ₂ O+K ₂ A step of performing a heat treatment at a temperature of 400 to 850 ℃ on the glass composition of 5 to 6 weight percent of O2; the primary heat treatment is followed by a secondary heat treatment step at a temperature of 780 ℃ to 880 ℃. And generating a lithium disilicate crystal phase and a silicon dioxide crystal phase with the nanometer size of 5nm to 2000nm through the primary heat treatment, wherein the light transmittance of the lithium disilicate crystal phase and the silicon dioxide crystal phase is regulated through the secondary heat treatment temperature.

In addition, as the living standard of people increases, the aesthetic requirements in the field of dentistry are increasing, and not only are the aesthetic requirements of patients increasing, but also research on aesthetic repairs using various materials is increasing.

The elements of the aesthetic restorative materials currently in primary use that affect the aesthetic appearance of ceramic restorations include the appearance, surface state, transparency, color tone, etc., where transparency, among other factors, may be an important element in the successful fabrication of the restoration. While many studies and developments have been made on the mechanical and physical properties of these esthetically repaired ceramics, there are still many problems in tone coordination, and the difficulty in tone selection, particularly transparency, of the prosthesis is still great in clinical and technical aspects.

In aesthetic restoration, the main factors affecting the beauty in restoring teeth are Color tone (Color), the shape and size of teeth, the arrangement state and ratio relation of teeth, light, permeability, the design of restoration, etc., and in fact, color and shape are perceived as being relatively sensitive visually.

Natural teeth are cut from the neck of the tooth, and none of the sites are the same color.

Based on these characteristics, a method for producing artificial teeth which simulate the dark color of natural teeth by using a so-called construction method has been recently disclosed.

The Build-Up method is a method of forming colored artificial teeth by stacking ceramic powder, zirconium dioxide powder or the like layer by layer, and then performing heat treatment on the artificial teeth to realize a color similar to that of natural teeth layer by layer, and the method is similar to that of the natural teeth, but the artificial teeth are beautiful and have low reproducibility and cannot be manufactured by an instant method because the artificial teeth are completely determined by the skill of a mechanic, and the artificial teeth are difficult to realize by a cutting method such as CAD/CAM.

On the other hand, when an artificial tooth is produced by a conventional block according to a cutting method such as CAD/CAM, the block itself is composed of a substance having uniform physical properties, and the artificial tooth produced by this method can be formed in a single color tone unlike a natural tooth. In particular, the artificial teeth produced by the method are aesthetically inconsistent, have a feeling of strangeness, and feel unnatural when used in the places such as incisors.

Although the transparency and workability can be adjusted by the above-mentioned method for manufacturing glass ceramics described in korean patent registration No. 10-1975548 of the applicant, the obtained glass ceramics are also a block body itself having the same physical properties, and therefore, if it is intended to obtain a deep color of natural teeth, a method of combining a plurality of finished products should be adopted. In other words, it is not easy to use the block itself directly to implement a natural-color tooth by cutting such as CAD/CAM.

By improving these problems, the present applicant has applied for registration of a dental block which can be used for manufacturing an artificial dental restoration similar to a natural tooth, and which can shorten the manufacturing time and process of the artificial dental restoration, and can increase the structural stability in terms of dispersion of force by functional gradient of mechanical properties (korean patent registration No. 10-2246195).

The present invention is a progressive block that provides an improved aesthetic appearance of the block as described above, and in particular further improves the machining efficiency. The present invention aims to provide progressive blocks with improved aesthetic properties for such blocks, in particular with further improved machining efficiency.

Disclosure of Invention

Technical problem

The purpose of the present invention is to provide a dental block that can be used for manufacturing an artificial tooth restoration material that exhibits Multi-level formulation (Multi-level) permeability and physical properties similar to those of natural teeth, and that has repeated reproducibility, without adding any additional steps by cutting such as CAD/CAM, and that is required for cutting.

The present invention aims to provide a dental block for cutting processing, which can shorten the manufacturing time and process of an artificial tooth restoration, and can be functionalized with a gradient of mechanical physical properties, and has increased structural stability in terms of force dispersion.

The present invention provides a simple method for manufacturing a dental block which can be used for cutting processing required for manufacturing an artificial tooth restoration material which exhibits multi-level permeability and physical properties similar to those of a natural tooth.

The present invention aims to provide a method for manufacturing such a dental block into a dental restoration by a processing mechanism in a simple manner.

Technical proposal

According to an embodiment of the present invention, a glass-ceramic block comprising a crystalline phase within an amorphous glass matrix, the primary crystalline phase comprising lithium disilicate and the additional crystalline phase comprising eucryptite (eucryptite); the gradient material with the main crystal phase size is provided relative to the gradient with the depth, and the gradient value change position of the main crystal phase size is free of the functional gradient material of the interface, namely the dental block is provided.

According to a preferred embodiment of the invention, the gradient of the size of the primary crystalline phase is such that its average particle size is in the range of 0.02 μm to 1.5 μm.

According to a preferred embodiment of the dental block, the light transmittance has a gradient along the depth.

According to a preferred embodiment, the gradient of light transmittance is in the range of 22 to 35% based on 550nm wavelength.

According to a preferred embodiment, the gradient of light transmittance varies along the depth within a range of 0.5 mm.

According to an embodiment of the present invention, a dental block has L along a depth according to color difference analysis ^* 、a ^* B ^* The gradient of values, the color deviation (ΔE) value, also varies over a range of 1.5mm along the depth.

According to an embodiment of the present invention, the dental block has a crystallinity of 40 to 80%.

According to a specific embodiment of the dental block, the lithium disilicate crystal phase comprises 50 to 90vol.% and the eucryptite crystal phase comprises 10 to 40vol.% based on the volume of the bulk crystal phase. According to other embodiments, it may also contain up to 5vol.% of the crystalline phase of lithium phosphate (lithium phosphate).

According to an embodiment of the present invention, the dental block has a gradient of flexural strength according to depth.

According to a preferred embodiment, the gradient of the bending strength is in the range of 210MPa to 510 MPa.

A dental block according to an embodiment of the present invention is formed with a continuous glass matrix.

According to a preferred embodiment, the glass substrate comprises SiO ₂ 69.0 to 78.0 weight percent, li ₂ 12.0 to 14.0 weight percent of O and Al ₂ O ₃ 5.5 to 10 weight percent, 0.21 to 0.6 weight percent of ZnO and K ₂ O2.0-3.5 wt% and Na ₂ 0.3 to 1.0 weight percent of O, 0.1 to 0.5 weight percent of SrO, 0.3 to 1.0 weight percent of CaO and La ₂ O ₃ 0.1 to 2.0 weight percent of P ₂ O ₅ 2.0 to 6.0 weight percent of Al ₂ O ₃ /(K ₂ O+zno) satisfies 1.2 to 2.2.

According to another embodiment of the present invention, there is provided a method of manufacturing a dental block, including: a step of producing a block of a predetermined shape, the step comprising: will contain SiO ₂ 69.0 to 78.0 weight percent, li ₂ 12.0 to 14.0 weight percent of O and Al ₂ O ₃ 5.5 to 10 weight percent, 0.21 to 0.6 weight percent of ZnO and K ₂ O2.0-3.5 wt% and Na ₂ 0.3 to 1.0 weight percent of O, 0.1 to 0.5 weight percent of SrO, 0.3 to 1.0 weight percent of CaO and La ₂ O ₃ 0.1 to 2.0 weight percent of P ₂ O ₅ 2.0 to 6.0 weight percent of Al ₂ O ₃ /(K ₂ A step of forming and cooling the glass composition having an O+ZnO) molar ratio of 1.2 to 2.2 in a mold after melting, and then slowly annealing the glass composition at a set rate within 20 minutes to 2 hours from 480 ℃ to 250 ℃;

and a step of heat-treating the block at a temperature ranging from 740 to 850 ℃ and applying a temperature gradient along the depth direction of the block to perform heat treatment.

According to a preferred embodiment of the method for producing a dental block, in the step of performing heat treatment, the upper layer portion of the block is performed at a temperature ranging from 800 to 850 ℃, and the lower layer portion of the block is performed at a temperature ranging from 740 to 760 ℃.

According to a preferred embodiment, the heat treatment step is carried out in a gradient heat treatment furnace (furnace) at an operating temperature of 800 to 1,000 ℃ for 1 to 40 minutes.

According to an embodiment of the present invention, there is provided a method of manufacturing a dental restoration, including: a step of manufacturing a predetermined dental restoration by machining the dental block according to the above-described embodiment with a machining machine; and polishing (polishing) or glazing (glazing) the dental restoration.

According to a preferred embodiment of the method of manufacturing a dental restoration, the glazing is performed at a temperature of 730 to 820 ℃ for 30 seconds to 10 minutes.

According to a preferred further embodiment of the method of manufacturing a dental restoration, the glazing is subjected to a heat treatment of at least 825 ℃ for adjusting the light transmittance of the finished dental restoration. Preferably, the glazing is carried out at a temperature of at least 825 ℃ for a period of 1 to 20 minutes.

Advantageous effects

The dental block according to the present invention is useful for manufacturing an artificial tooth restoration material having repeated reproducibility, which exhibits Multi-level light transmittance and physical properties similar to those of natural teeth, without adding any additional process by cutting such as CAD/CAM, and can be manufactured by a simple method using a glass composition having a specific combination by gradient heat treatment, by shortening the manufacturing time and process of the artificial tooth restoration, and by functionally increasing structural stability in terms of dispersion of force by gradient of mechanical physical properties.

Drawings

FIG. 1 is a graph of the X-ray diffraction results of a block of the present invention;

FIG. 2 is a scanning electron microscope (Scanning Electron Microscope, SEM) photograph showing the fine structure and crystal phase size of the block of the present invention at different depths;

FIG. 3 is a graph of visible light transmittance measurements for 1.5mm thick slice specimens of the blocks of the present invention;

FIG. 4 is a comparative chart of cutting resistance (cutting resistance) for the block of the present invention;

FIG. 5 is a schematic view showing a method for producing a dental block according to the present invention;

FIG. 6 is a graph illustrating the primary crystal phase particle size at different depths of a bulk obtained in accordance with an embodiment of the present invention;

fig. 7 is a graph showing the variation of biaxial bending strength (biaxial flexure strength) for different depths of the resulting block according to an embodiment of the present invention.

Detailed Description

Technical solutions in the embodiments of the present invention will be described in detail and clearly with reference to the accompanying drawings in the embodiments of the present invention, but the described embodiments are some embodiments of the present invention, not all embodiments. The embodiments are convenient for those of ordinary skill in the art to understand and reproduce.

The dental block of the present invention is a glass ceramic block containing a crystal phase in an amorphous glass matrix, and includes a functional gradient material having a main crystal phase of lithium disilicate and eucryptite (eucryptite) as an additional crystal phase, a gradient of the main crystal phase with respect to depth, and no interface at a point where a gradient value of the main crystal phase changes.

According to the above and the following description, the term of the main crystal phase is defined as a crystal phase of at least 50 weight percent of the bulk crystal phase, and the additional crystal phase is defined as the remaining crystal phase of the bulk crystal phase excluding the main crystal phase.

The content of the crystal phase can be calculated by X-ray diffraction, and as an example, the ratio Fa of the crystal phase a in a specimen composed of two multi-shaped a and b can be quantitatively represented by the following formula 1.

< formula 1>

This value can be obtained by measuring the intensity ratio of two crystal phases and obtaining an integer K. K is the absolute intensity ratio I of 2 pure polymorphisms _oa /I _ob， The measurement is carried out by measuring a standard substance.

According to the above and the following descriptions, the term of the main crystal phase can be defined as: the content calculated by these methods is set as a reference.

The expression "gradient with respect to depth of the main crystal phase size" means that the result of graphically displaying the main crystal phase size along the depth of the bulk shows that there is a gradient in the change in the main crystal phase size. Further, the main crystal phase size is shown in a gradient (gradient) form with respect to the bulk depth.

The "gradient value change point of the main crystal phase size" refers to a point at which the gradient value of the change of the main crystal phase size actually changes when the main crystal phase size along the depth of the bulk is graphically represented. The term "actual change" as used herein means single data, and may mean a change, but may include a change actually occurring according to the value distribution.

The expression "no interface exists at the point where the gradient value of the main crystal phase changes" means that no significant boundary surface showing interlayer separation exists at the point where the gradient value of the main crystal phase changes at the depth of the bulk. Further, the bulk is in a continuous form with no interface along the depth, having a gradient of the main crystal phase size.

The "functionally graded material (Functionally Gradient Material, FGM)" refers to a material in which the properties of the constituent material generally change continuously from one surface to the other surface. In the present invention, there is practically no interface, but the properties of the constituent materials are continuously changed, so that an expression form called a functionally graded material is used.

The block is not limited in shape according to the above and the following descriptions, and may include, for example, blocks in various forms such as a block form, a disk form, an ingot form, and a cylinder form.

According to the block of the invention, the primary crystalline phase comprises lithium disilicate, and the eucryptite is included as an additional crystalline phase, which may include lithium phosphate as other additional crystalline phases.

A graph of X-ray diffraction (X-ray diffraction analysis, XRD) analysis results of a block according to a preferred embodiment of the invention is illustrated in fig. 1.

In fig. 1, the dental block according to an embodiment of the present invention has a main crystal phase of lithium disilicate. Further, as an additional crystal phase, a main peak appears at 2θ=19.8, 25.7 (degrees), and the like, which can be explained as eucryptite (jcpds#12-0709).

The dental block of an embodiment of the invention disclosed herein is one in which, in addition to eucryptite, as an additional crystalline phase, the dominant peak occurs at 2θ=22.18, 22.9 degrees, which may be defined as the dominant peak in lithium phosphate (lithium phosphate, JCPDS #15-0760, 2θ= 22.3,23.1).

As described above and below, XRD analysis is understood to mean analysis by an X-ray diffractometer (D/MAX-2500,Rigaku,Japan;Cu K. Alpha. (40 kV,60 mA), scanning speed: 6 DEG/min, 2. Theta.: 10 to 60 (degree), rigaku, japan).

The eucryptite is prepared by using LiAlSiO ₄ Expressed lithium aluminum silicate (LAS for short) crystalline phase, with other LAS series spodumene (LiAlSi) ₂ O ₆ ) Orthoclate (LiAlSi) ₃ O ₈ ) Or petalite (LiAlSi) ₄ O ₈ ) Compared to the residual thermal stress, it has the property of lower cutting resistance to the working tool. If such a crystal phase is contained, the tool wear rate is lower and the tool resistance is reduced as compared with the case of containing only lithium disilicate, so that the cutting efficiency can be improved, the consumption of the milling tool can be minimized, and the occurrence of chipping (chipping phenomenon) during the machining can be minimized.

These crystal phases constituting the bulk of the present invention have the property that crystallites can be formed and various mechanical properties and light transmittance can be achieved while exhibiting different sizes and size distributions depending on temperature.

And has a gradient of the size of the main crystal phase with respect to depth, so that the block can realize gradual light transmittance and mechanical properties with respect to depth. In particular, since there is no interface at the point where the gradient value of the main crystal phase changes, it is not necessary to process the material by bonding between layers, and the problem of layer separation occurring during cutting can be solved. Due to these functional gradients, artificial dental prostheses can be provided which increase the structural stability in terms of the dispersion of forces.

According to the block of the present invention, a gradient of the size of the main crystal phase thereof can be achieved in the range of 0.02 μm to 1.5 μm in average particle diameter.

As an example, fig. 2 shows a Scanning Electron Microscope (SEM) photograph of a dental block according to the present invention, fig. 2 shows a scanning electron microscope photograph of a lower layer portion (20 mm deep portion) of the block on the left side, fig. 2 shows a scanning electron microscope photograph of a middle portion (10 mm deep) of the block on the center, and fig. 2 shows a scanning electron microscope photograph of an upper layer portion (0.5 mm deep) of the block on the right side.

The average size of the crystal phase particles can be derived from the electron scanning microscope photograph obtained as described above, specifically, by drawing a diagonal line or an arbitrary straight line on the scanning electron display microscope photograph, dividing the number of crystal phases passing through the straight line by the length of the straight line, and then obtaining the number from the magnification by a truncated line method (linear intercept method).

From the above and the following descriptions, it is understood that the size of the crystal phase can be calculated by the following method.

The block of the present invention is a functionally graded material which is suitable for cutting processing such as CAD/CAM processing under the same processing conditions, and therefore, in view of machinability, the graded average particle diameter of the main crystal phase size is preferably in the range of 0.02 μm to 1.5 μm from the viewpoint of clinically achievable transmissivity of an artificial tooth restoration material or the like.

The dental block of the present invention has a gradient of the size of the main crystal phase as described above, and thus has a gradient of light transmittance with respect to depth.

In particular, the gradient of the crystal size is in the range of 22 to 35% based on the wavelength of 550nm, considering the range of the average particle diameter.

The light transmittance was measured by an ultraviolet-visible spectrophotometer (UV-2401 PC, shimadzu, japan) according to the above and the following descriptions.

As described above, since the dental block of the present invention has no interface at the point where the gradient value of the main crystal phase size changes, the gradient of the light transmittance changes within a range of 0.5mm with respect to the depth, and it can be actually confirmed that the gradient also changes within a range of 1.5mm with respect to the depth.

In order to measure the light transmittance at each inclined position, the dental block of the present invention was cut in the depth direction of reduced transparency by about 1.5mm, and then the surface of the sample was wiped clean with alcohol, and then measured using an ultraviolet-visible spectrophotometer (UV-2401 PC, shimadzu, japan). In this case, the measurement wavelength range was 300 to 800nm, and the slit width was 2.0nm. As can be seen from the results of FIG. 3, there was a difference in transmittance for the 1.5mm thick slice specimens.

Each sample in fig. 3 corresponds to a sample of a different depth in table 1 below.

[ Table 1 ]

Specimen numbering	Depth (mm)
		1	1.5
2	3.0
		3	4.5
4	6.0

This result shows that the light transmittance also varies within a depth of 1.5mm, and further, the transmittance gradient is still exhibited at this thickness. The result is a clear indication that the dental block of the present invention is indeed a functionally graded material.

When a dental crown or other restorative body is used, the thickness of the restorative body is the thickest at the position corresponding to the bridge-head fort, and it is predicted that the light transmittance of the restorative body can still be shown to be aesthetically outstanding within the thickness range.

On the other hand, the dental block of the present invention also has a gradient in coloration, specifically a gradient value of L x, a in color difference analysis with respect to depth ^* B ^* Values. As described above, the dental block of the present invention has no interface at the point where the gradient value of the main crystal phase size changes, and it can be confirmed from these angles that the color deviation (Δe) also changes within the range of 1.5mm in depth.

For the correct measurement, transfer and reproduction of the color, a corresponding color standard is established, and thus a color system (color system) is established. Various color systems have emerged, with the CIE lxab color space (CIELAB color space) specified by the international lighting association (CIE Commission International de L' Eclairage) in 1976 being the most widely used and being used up to now. Wherein L represents luminance (lightness), a and b represent chromaticity coordinates (chromaticity coordinates). The values in the coordinates are shown to be brighter as L increases and darker as L decreases, +a represents red, +b represents yellow, and-b represents blue.

For color measurement of the dental block of the present invention according to the type of inclined position, after cutting about 1.5mm in the depth direction of reduced transparency, the surface of the sample was wiped clean with alcohol, and then analyzed with an ultraviolet-visible spectrophotometer (UV-2401 PC, shimadzu, japan). The measurement wavelength range was 380-780nm, and the slit width was 2.0nm. After setting a reference line (baseline) using the base sample, the reflectance of the sample is measured to determine L ^* a ^* b ^* Color system. Measured L ^* a ^* b ^* The value is an average value used after repeating three times to reduce the error. The Δe of the color difference was obtained by using these three values. The Δe values of the two samples are 0, which indicates no chromatic aberration, and the values corresponding to 0 to 2 indicate chromatic aberration (, which is very small very slight difference); a value of 2 to 4 indicates a distinction of a color difference capable of perceiving (notify) color difference; the values of 4 to 6 represent easy (appdifferential) discrimination of color differences. Values of 6 to 12 indicate large chromatic aberration (mux), and values of 12 or more indicate very large chromatic aberration (very mux).

As a glass ceramic block having a crystal phase in an amorphous glass matrix as shown in fig. 1 to 2, a main crystal phase including lithium disilicate as a crystal phase, a supplementary crystal phase including eucryptite as a gradient having a main crystal phase size with respect to depth, and a dental block as a gradient functional material having no interface at a gradient value change point of the main crystal phase size, it can be seen from the results shown in table 2 below that a color deviation (Δe) of 1.4 to 1.6 occurs with respect to depth on a slice specimen having a thickness of 1.5mm, and the results as described above indicate that the color deviation (Δe) also changes within a range of 1.5mm with respect to depth, and further, it is considered that a gradient shadow (gradient shade) of different colors appears at the thickness. Clearly, this result clearly shows from another aspect that the dental block of the present invention does belong to functionally graded materials.

[ Table 2 ]

Specimen numbering	Depth (mm)	L ^*	a ^*	b ^*	ΔE
						1	0.31	69.8	-1.68	9.51
2	0.62	70.50	-1.81	10.80	1.47
						3	0.93	71.40	-1.95	12.10	1.58
4	1.24	73.00	-2.10	12.02	1.60

The dental block of the present invention also has a gradient of flexural strength along the depth. In particular, from the aspect of the gradient of the crystal size described above, the gradient of the bending strength may be in the range of 210MPa to 510MPa depending on the range of the average particle diameter.

On the other hand, the dental block of the present invention is preferably 40 to 80% in terms of crystallinity from the viewpoint of functional gradient capable of realizing various physical properties as described above and processing efficiency.

In the description and the following description, the "crystallinity" means a ratio of a crystal phase to an amorphous glass substrate, and may be achieved by various methods, and in one embodiment of the present invention, is a value automatically calculated by an X-ray diffractometer.

As described above, the dental block of the present invention is a glass ceramic in which a crystal phase is precipitated in a continuous amorphous glass matrix, or a functionally graded material in which a crystal phase including a main crystal phase including lithium disilicate, an additional crystal phase including eucryptite has a gradient of a main crystal phase size with respect to depth, and an interface does not exist at a point where a gradient value of the main crystal phase size changes.

Preferably, the crystalline phase is a lithium disilicate crystalline phase comprising 50 to 90vol.%, based on the bulk crystalline phase volume, and the additional crystalline phase, i.e. the eucryptite crystalline phase, comprises 10 to 40vol.%, when lithium phosphate is included as the additional crystalline phase, it is preferably present in an amount of at most 5vol.%.

As described above, the eucryptite crystal phase has an effect of improving machinability in glass ceramics including lithium disilicate as a main crystal phase, but the content thereof excessively increases, rather, the strength thereof decreases. The content of eucryptite in the crystalline phase is thus preferably 10 to 40vol.% based on the volume of the bulk crystalline phase, in terms of processability and strength.

As described above and below, the term "continuous glass matrix" means that there is no interlayer interface in the glass matrix, and the composition of the glass matrix may be defined as the same in the entire block.

Preferred glass substrates are, in particular, those comprising SiO ₂ 69.0 to 78.0 weight percent, li ₂ 12.0 to 14.0 weight percent of O and Al ₂ O ₃ 5.5 to 10 weight percent, 0.21 to 0.6 weight percent of ZnO and K ₂ O2.0-3.5 wt% and Na ₂ 0.3 to 1.0 weight percent of O, 0.1 to 0.5 weight percent of SrO, 0.3 to 1.0 weight percent of CaO and La ₂ O ₃ 0.1～2.0 weight percent and P ₂ O ₅ 2.0 to 6.0 weight percent of Al ₂ O ₃ /(K ₂ O+zno) may satisfy 1.2 to 2.2.

The glass composition is used for crystal formation, crystal nucleus formation and crystal growth heat treatment are carried out to precipitate crystal phase in the amorphous glass matrix, and the temperature for crystal nucleus growth of the glass matrix is 500-850 ℃. Further, nucleation starts from a minimum of 500 ℃, and as the temperature increases, crystals grow, which exhibits the lowest light transmittance at a maximum of 850 ℃ when used as an artificial tooth. Further, the transmittance gradually decreases from the temperature of crystal growth to 850 ℃ at maximum, but from these crystal growth considerations, if this can be achieved in one block, multiple gradients (multi-gradients) of natural teeth can be simulated.

The natural teeth are not only one tooth per se, but all teeth have various light transmittance, and the gradual change of the natural teeth can be fully realized by realizing the light transmittance change caused by the heat treatment temperature on one block.

From these points of view, the present invention provides a method of manufacturing a dental block comprising passing a dental block comprising SiO ₂ 69.0 to 78.0 weight percent, li ₂ 12.0 to 14.0 weight percent of O and Al ₂ O ₃ 5.5 to 10 weight percent, 0.21 to 0.6 weight percent of ZnO and K ₂ O2.0-3.5 wt% and Na ₂ 0.3 to 1.0 weight percent of O, 0.1 to 0.5 weight percent of SrO, 0.3 to 1.0 weight percent of CaO and La ₂ O ₃ 0.1 to 2.0 weight percent of P ₂ O ₅ 2.0 to 6.0 weight percent of Al ₂ O ₃ /(K ₂ Melting a glass composition having an O+ZnO) molar ratio of 1.2 to 2.2, molding and cooling the glass composition in a mold, and annealing the glass composition at a set speed from 480 ℃ to 250 ℃ for 20 minutes to 2 hours to produce a block of a predetermined shape;

and a step of heat-treating the block at a temperature ranging from 740 to 850 ℃ and applying a temperature gradient with respect to the depth direction of the block.

As described above, the glass composition may exhibit characteristics in which light transmittance of the material varies according to a heat treatment temperature range, and if the heat treatment applied to the block is constant, transmittance is constant, but the heat treatment applied to the block has a temperature gradient, multiple gradation of physical properties or transmittance may be exhibited in one block.

A block in the form of a block is used as a machining work such as CAD/CAM machining, and a block having a more gradual transmittance and strength is produced by applying temperature gradient heating to the depth direction when the block is heat-treated.

The conventional crystallized glass is coarse, has a high transmittance and a high strength, and is difficult to process, compared with the conventional crystallized glass, and the glass composition used in the present invention is capable of forming crystallites, and exhibits various physical properties and light transmittance while exhibiting various size and size distribution depending on temperature.

The "step of applying a temperature gradient with respect to the depth direction of the block for heat treatment" means that a temperature gradient that increases in order from the lower end to the upper end with respect to the depth direction of the block may be applied, or a temperature gradient in the form of a temperature difference may be allowed to be partially set. The temperature gradient method is selected such that the natural tooth characteristics of the patient of the artificial tooth prosthesis are changed according to the need, or the natural characteristics of the tooth portion of the prosthesis are changed according to the need.

However, in view of ordinary natural teeth, it is preferable that the heat treatment temperature gradient is such that the temperature gradient is applied in a gradually rising manner from the lower end to the upper end with respect to the depth of the block.

According to a preferred embodiment, in the step of performing the heat treatment, the upper portion of the block is applied at a temperature ranging from 800 to 850 ℃ and the lower portion of the block is applied at a temperature ranging from 740 to 760 ℃, for which the step of actually performing the heat treatment is preferably performed at an operating temperature ranging from 800 to 1,000 ℃ for a time ranging from 1 minute to 40 minutes in a gradient heat treatment furnace.

When the above-described glass composition is used in the heat treatment method of the present invention, it is possible to simulate the structural characteristics of natural teeth that the transmittance of the dental neck is low, and the transmittance is high as the glass composition is closer to the incised ridge. Therefore, as in the conventional method, it is not necessary to perform additional characterization (characterization) in the preparation of the prosthesis, and therefore it is economically advantageous.

The present invention is characterized in that a functionally graded material having a gradient of mechanical properties, particularly flexural strength, is used in accordance with a microstructure difference along a heat treatment depth, and thus is very similar to the characteristics of natural teeth.

The dental restoration produced by using the dental block obtained according to the present invention is expected to be significantly improved in terms of workability, and as a specific example, in one embodiment of the present invention, there is provided a method for producing a dental restoration comprising: a step of manufacturing a predetermined dental restoration by machining the dental block by a machining machine; and polishing or glazing.

As described above and below, dental restorations naturally include crowns, inlays, onlays, veneers, abutments and the like.

The glazing may be carried out at a temperature of 730 to 820 ℃ for 30 seconds to 10 minutes, and may be carried out as a conventional finishing heat treatment step, with substantially no change in transmittance after heat treatment. Glazing is generally performed within a range that does not change the inherent transmissivity of the block, and surface microcracks are relieved (surface sizing) during glazing heat treatment, so that the strength is increased by more than 50%.

However, according to a particular embodiment, in the method of manufacturing a dental restoration using the block of the present invention, glazing may be used to adjust the transmissivity of the finished dental restoration by a heat treatment of at least 825 ℃. Further, after the machined block is fabricated into a dental restoration, glazing may be used to reduce transmission and thereby adjust brightness in a final finishing step.

When a dental restoration is manufactured by machining a block by a machining side or a user side, there is a possibility that transmittance may be unintentionally increased, and in such a case, a normal lithium disilicate block needs to be passed through again: discarding the processed corresponding block, reusing the block, performing a predetermined heat treatment, and processing the block meeting the transmittance requirement into a dental restoration. However, since the block of the present invention is a special block having a fine crystal phase, it can exhibit a property that the transmittance can be adjusted according to the heat treatment temperature, and therefore, the processed product processed into the dental restoration does not need to be reworked, and the transmittance can be easily adjusted again through a step of glazing under predetermined conditions in the final finishing step. Further, color change teeth (color tooth) occurring during the process of processing the dental restoration can be easily masked by glazing.

Glazing for this purpose is preferably carried out at a temperature of at least 825 ℃ for a period of from 1 minute to 20 minutes.

In particular, according to a specific example, the dental block obtained according to the present invention is a glass ceramic block having a crystal phase in an amorphous glass base as shown in fig. 1 to 2, wherein the crystal phase is a main crystal phase including lithium disilicate, the additional crystal phase includes eucryptite, and a gradient having a main crystal phase size with respect to depth is provided, and a dental block (this development) is a functionally graded material having no interface at a gradient value change point of the main crystal phase size, and the cutting time is measured while rotating at a rotation speed of 250RPM by a slow cutter (ISOMET low speed saw, buehler, germany) and a electroplated diamond grinding wheel (2514485 h17, norton, usa) at a size of 12×14×18 mm. And the cutting time was measured on the most common final heat treatment of lithium disilicate blocks (conventional lithium disilicate) (Rosetta SM, HASS Corp), zirconia-reinforced lithium disilicate blocks (central Duo, dentsply siron) and aluminum lithium silicate-reinforced lithium disilicate blocks (Nice, straumann company) using the same method.

The cutting resistance (cutting resistance,%) was calculated from each of the cutting time values obtained as described above, specifically, the cutting time of a conventional lithium disilicate block was taken as 100%, and then the cutting time was converted in relative percentage, which was calculated as each of the cutting resistance values.

The results are shown in the graph of FIG. 4.

According to the results of fig. 4, the cutting resistance of the conventional lithium disilicate block is highest, followed by the cutting resistance of LAS (lithium aluminum silicate) crystallized glass, zirconia-reinforced crystallized glass, which is remarkably low. From these results, it can be predicted that the glass-ceramic block of the present invention is most machinable because it contains a complementary crystalline phase, eucryptite.

According to one embodiment of the present invention, the method comprises the steps of first including SiO ₂ 69.0 to 78.0 weight percent, li ₂ 12.0 to 14.0 weight percent of O and Al ₂ O ₃ 5.5 to 10 weight percent, 0.21 to 0.6 weight percent of ZnO and K ₂ O2.0-3.5 wt% and Na ₂ 0.3 to 1.0 weight percent of O, 0.1 to 0.5 weight percent of SrO, 0.3 to 1.0 weight percent of CaO and La ₂ O ₃ 0.1 to 2.0 weight percent of P ₂ O ₅ 2.0 to 6.0 weight percent of Al ₂ O ₃ /(K ₂ O+zno) may satisfy a glass composition weight, mixing, of 1.2 to 2.2.

Al ₂ O ₃ When added to silicate glass, the glass enters tetrahedral coordination sites (tetrahedral sites), and functions as a glass former (glass former), which increases viscosity and reduces ion migration (mobility). In contrast, K ₂ O and ZnO, caO, na ₂ O is the mobility of ions which reduces the viscosity and increases the mobility of ions. It is predicted that the more ion mobility increases, the more preferential the alignment growth of eucryptite. And the increase of migration of ZnO or the like increases the mobility of ions, wherein if SiO ₂ In excess of the minor (minor) crystalline phase such as eucryptite and the main crystalline phase, i.e. pyrosilicic acidLithium is precipitated together in the glass matrix. From these angles, al ₂ O ₃ /(K ₂ O+zno) in a molar ratio of 1.2 to 2.2, is preferred for providing the block of the invention comprising eucryptite as a supplemental crystalline phase.

Li may be added as a glass composition ₂ CO ₃ To replace Li ₂ O，Li ₂ CO ₃ Carbon (C) component (C), namely carbon dioxide (CO) ₂ ) Is discharged in a gas form in the glass melting step. And K can also be added into the alkali oxide ₂ CO ₃ 、Na ₂ CO ₃ Respectively replace K ₂ O and Na ₂ O，K ₂ CO ₃ 、Na ₂ CO ₃ Carbon (C) component (C), namely carbon dioxide (CO) ₂ ) Is discharged in a gas form in the glass melting step.

The mixing is performed by a dry mixing process, and as the dry mixing process, a ball milling (ball milling) process or the like may be used. Specifically, the ball milling process is to mechanically crush and uniformly mix starting materials by rotating a ball mill at a certain speed after the starting materials are charged into the ball mill. The balls used in the ball mill may be formed of a ceramic material such as zirconium dioxide or aluminum oxide, and the balls may all have the same size or at least two or more kinds of balls may be used. The size of the ball, the ball milling time, the rotational speed per minute of the ball mill, and the like are adjusted according to the particle size as a target. As an example, considering the particle size, the ball size is set in the range of about 1mm to 30mm, and the rotation speed of the ball mill may be set in the range of about 50 to 500 rpm. The ball milling is preferably performed for 1 to 48 hours according to the targeted particle size and the like. After ball milling, the starting materials are crushed into fine particles, and the particles are uniformly mixed while having uniform sizes.

The mixed starting materials are placed in a melting furnace, and the melting furnace filled with the starting materials is heated to melt the starting materials. Here, melting means that the starting material is changed to a liquid state having viscosity, i.e., a non-solid state. The melting furnace is preferably formed of a material having a small contact angle in order to suppress the sticking of the melt, and is preferably formed of a material such as platinum (Pt), diamond-like carbon (diamond-like carbon), or refractory clay (chamotte), or is coated with a material such as platinum or diamond-like carbon (diamond-like carbon).

The melting is preferably carried out at a temperature of 1,400 to 2,000 ℃ for 1 to 12 hours at normal pressure. At a melting temperature below 1,400 ℃, the starting materials will not melt as much, and at a melting temperature exceeding 2,000 ℃, the energy requirements consumed will be excessive and the economy will be reduced, so that it is preferable to melt at a temperature in the above range. Moreover, when the melting time is too short, the melting of the starting material is insufficient, and when the melting time is too long, the energy consumption is too large, and the economical efficiency is lowered. The temperature rising rate of the melting furnace is preferably about 5 to 50 ℃/min, and when the temperature rising rate of the melting furnace is too low, the time required is too long and productivity is lowered, and when the temperature rising rate of the melting furnace is too high, the temperature is rapidly increased, so that the volatilization amount of the starting material is increased, and the physical properties of crystallized glass are adversely affected, so that the temperature of the melting furnace is preferably raised at the temperature rising rate within the above range. The melting is preferably performed under an oxidizing atmosphere such as oxygen or air.

To obtain crystallized glass for teeth that meets the desired morphology and size, the melt is poured into a prescribed molding die. The molding die is formed of a material having a high melting point and a high strength, and preferably having a low contact angle in order to suppress the adhesion of glass melt, and is formed of a material such as graphite (graphite) or carbon (carbon), and is preferably preheated to 200 to 300 c in order to prevent thermal shock, and then the melt is poured into the molding die.

The melt loaded in the molding die is molded and cooled, and after the cooling process, it is preferable to go through a step of slowly annealing (annealing) at a set rate for a period of 20 minutes to 2 hours from 480 ℃ to 250 ℃. As described above, by the annealing step, the stress deviation in the molded article is reduced, preferably, no stress is present, and further, in the crystallization step thereafter, the size control of the crystal phase and the improvement of the homogeneity of the crystal distribution can be favorably affected, thereby finally obtaining the desired functionally graded material.

Here, the set speed means that the annealing is preferably sufficiently slow at 2.3 to 14 ℃/min.

As described above, the molded article obtained by the slow annealing process is transferred to a crystallization heat treatment furnace, and a desired crystallized glass is produced by nucleation and crystallization growth.

Fig. 5 shows a modeling method of applying a temperature gradient to perform crystallization heat treatment according to the present invention, in which a temperature gradient is applied in the depth direction when a crystallization heat treatment is performed to a block of a block type or an ingot type, the upper end is subjected to heat treatment at a high temperature and the lower end is subjected to heat treatment at a low temperature.

The step of applying a temperature gradient to perform the heat treatment is not limited to a specific apparatus and method, but may be performed in a gradient heat treatment furnace (furnace), for example, and the operation temperature is preferably 900 to 1,100 ℃ in consideration of the heat treatment temperature.

By the heat treatment with a temperature gradient, a gradient of light transmittance to high transmittance (high transmittance) and a gradient of bending strength to low strength (low flexural strengh) are exhibited from the high temperature portion to the low temperature portion. The reason for this is that the crystal size in the crystallized glass can be adjusted according to the temperature. The crystalline phases generated after the heat treatment with a temperature gradient are a main crystalline phase including lithium disilicate and an additional crystalline phase including eucryptite, and may have a size gradient of the main crystalline phase having an average particle diameter of 0.02 μm to 1.5 μm after the generation.

In addition, the results of the analysis of the particle size of the bulk obtained according to the present invention as a function of depth are shown in fig. 6.

The results of measuring the flexural strength change with depth of the block obtained according to the present invention are shown in fig. 7.

The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may be modified or replaced by equivalent modifications, which do not depart from the scope of the technical solutions described in the embodiments of the present invention.

Industrial utilization

The present invention relates to a dental block and a method for manufacturing an artificial tooth having similar structural characteristics to natural teeth, and more particularly, to an improved machinability.

The dental block according to the present invention can be used for manufacturing an artificial tooth restoration material having repeated reproducibility, which exhibits Multi-level light transmittance and physical properties similar to those of natural teeth, without adding any additional process by cutting such as CAD/CAM, and can be manufactured by a simple method using a glass composition having a specific combination by gradient heat treatment, by shortening the manufacturing time and process of the artificial tooth restoration, and by functionally increasing the structural stability in terms of dispersion of force by the gradient of mechanical physical properties.

Claims

1. A dental block, characterized in that,

as a glass ceramic block containing a crystalline phase in an amorphous glass matrix,

the primary crystal phase of the crystalline phases comprises lithium disilicate, and the additional crystalline phases comprise eucryptite (eucryptite);

the gradient material with the main crystal phase size along the depth does not exist at the gradient value change point of the main crystal phase size.

2. The dental block of claim 1, wherein the dental block comprises a dental implant,

the gradient of the size of the main crystal phase is such that the average particle diameter thereof is in the range of 0.02 μm to 1.5. Mu.m.

3. The dental block of claim 1, wherein the dental block comprises a dental implant,

the light transmittance has a gradient along the depth.

4. A dental block according to claim 3, wherein,

the gradient of light transmittance is in the range of 22 to 35% based on 550nm wavelength.

5. A dental block according to claim 3, wherein,

the gradient of light transmittance also varies along the depth within 0.5 mm.

6. The dental block of claim 1, wherein the dental block comprises a dental implant,

along the depth with L according to color difference analysis ^* 、a ^* B ^* The gradient of values, the color deviation (ΔE) value, also varies over a range of 1.5mm along the depth.

7. The dental block of claim 1, wherein the dental block comprises a dental implant,

the crystallinity is 40 to 80%.

8. The dental block according to claim 1 or claim 7, wherein the dental block comprises,

the lithium disilicate crystalline phase comprises 50 to 90vol.% and the eucryptite crystalline phase comprises 10 to 40vol.% based on the volume of the bulk crystalline phase.

9. The dental block of claim 1, wherein the dental block comprises a dental implant,

the bending strength has a gradient along the depth.

10. The dental block of claim 9, wherein the dental block comprises a dental implant,

the gradient of the bending strength is in the range of 210MPa to 510 MPa.

11. The dental block of claim 1, wherein the dental block comprises a dental implant,

dental blocks are formed from a continuous glass matrix.

12. Dental block according to claim 1 or 11, characterized in that,

the glass matrix comprises SiO ₂ 69.0 to 78.0 weight percent, li ₂ 12.0 to 14.0 weight percent of O and Al ₂ O ₃ 5.5 to 10 weight percent, 0.21 to 0.6 weight percent of ZnO and K ₂ O2.0-3.5 wt% and Na ₂ 0.3 to 1.0 weight percent of O, 0.1 to 0.5 weight percent of SrO, 0.3 to 1.0 weight percent of CaO, and La ₂ O ₃ 0.1 to 2.0 weight percent of P ₂ O ₅ 2.0 to 6.0 weight percent of Al ₂ O ₃ /(K ₂ O+zno) satisfies 1.2 to 2.2.

13. A method of manufacturing a dental block, comprising:

a step of producing a block of a predetermined shape, the step comprising: will contain SiO ₂ 69.0 to 78.0 weight percent, li ₂ 12.0 to 14.0 weight percent of O and Al ₂ O ₃ 5.5 to 10 weight percent, 0.21 to 0.6 weight percent of ZnO and K ₂ O2.0-3.5 wt% and Na ₂ 0.3 to 1.0 weight percent of O, 0.1 to 0.5 weight percent of SrO, 0.3 to 1.0 weight percent of CaO and La ₂ O ₃ 0.1 to 2.0 weight percent of P ₂ O ₅ 2.0 to 6.0 weight percent of Al ₂ O ₃ /(K ₂ A step of forming and cooling the glass composition having an O+ZnO) molar ratio of 1.2 to 2.2 in a mold after melting, and then slowly annealing the glass composition at a set rate within 20 minutes to 2 hours from 480 ℃ to 250 ℃;

14. The method of manufacturing a dental block according to claim 13, wherein,

in the step of performing the heat treatment, an upper layer portion of the block is applied at a temperature range of 800 to 850 ℃ and a lower layer portion of the block is applied at a temperature range of 740 to 760 ℃.

15. The method of manufacturing a dental block according to claim 13 or claim 14,

the heat treatment step is carried out in a gradient heat treatment furnace at an operating temperature of 800 to 1,000 ℃ for 1 to 40 minutes.

16. A method for producing a dental restoration, characterized by comprising the steps of,

comprising the following steps: a step of machining the dental block required for the cutting process according to claim 1 by a machining machine to manufacture a predetermined dental restoration; and

polishing or glazing the dental restoration.

17. The method of manufacturing a dental block according to claim 16, wherein,

glazing is carried out at a temperature of 730 to 820 ℃ for 30 seconds to 10 minutes.

18. The method of manufacturing a dental block according to claim 16, wherein,

glazing is a heat treatment at least 825 c for adjusting the light transmittance of the finished dental restoration.

19. The method of manufacturing a dental block according to claim 18, wherein the glazing is performed for 1 to 20 minutes at a temperature of at least 825 ℃.