KR102540474B1 - Ceramics blank for multilayer-structure dental cutting processing having high color tone reproducibility - Google Patents

Abstract

The present invention provides a ceramic blank for dental cutting with a multi-layered structure close to the color of natural teeth. On the upper and lower surface layers, the E layer ( _LE , _CE ) with the lowest chroma and the C layer ( _LC , C _C ) with the highest chroma are arranged in parallel, respectively, and the M layer (L _M , C _M ) are positioned in parallel, a ceramics blank for dental cutting comprising a layer structure of four or more layers, wherein the lightness L* and chroma C* in each layer satisfy the following relationship.
L _M = ( _LE + L _C )/2 × 0.97 to 1.03
C _M = (C _E + C _C )/2×0.93 to 1.07
C _C ＞C _M ＞C _E

Description

Ceramics blank for dental cutting with multi-layered structure with high color reproducibility

The present invention is a ceramic blank for dental cutting processing having a multi-layer structure of 4 or more layers used for cutting processing by a CAD/CAM system in the dental field and having a characteristic color tone distribution in the layer structure, which is applied to zirconia plastic firing It relates to a sieve, a sintered body, and a dental prosthesis device cut and processed using the same, or a dental prosthesis device sintered after cutting.

Conventionally, in the dental treatment of crown defects, prosthetic restoration using cast crown bridges or dentures has been generally performed, and specifically, porcelain is baked on the surface of a metal frame made of a casting alloy for baking porcelain to reproduce the shape of the crown. Clinical applications of porcelain-baked crowns and bridges that combine functionality and esthetics are mentioned.

In addition, there is no worry about the development of metal allergy, and from the viewpoint of a sharp price increase depending on the market price of precious metals or from the viewpoint of aesthetics that can imitate the color tone of natural teeth, alumina, aluminosilicate glass, lithium disilicate glass, etc. are used. BACKGROUND ART A prosthetic device manufactured by a dipping method or a press method using a ceramic ingot, or so-called all-ceramics, is attracting attention, and prosthetic restoration using the device is also increasing.

In recent years, the technology of manufacturing prosthetic devices by cutting using a dental CAD/CAM system has rapidly spread, cutting blanks such as blocks or disks made of zirconia, alumina, aluminosilicate glass, and lithium disilicate glass. , it is becoming possible to easily manufacture prosthetic devices. In addition, in order to improve the machinability of zirconia, which is widely used clinically as high-strength ceramics, there is a zirconia calcined body adjusted to strength and hardness advantageous to cutting by calcining at a low firing temperature without performing until complete sintering.

Tetragonal partially stabilized zirconia containing 3 mol% yttria is put into practical use because zirconia has a flexural strength used for bridge frames of 4 units or more. Zirconia containing 3 mol% yttria includes zirconia in which a small amount of alumina is added to improve sinterability and suppress low-temperature deterioration. In addition, in order to increase light transmittance so that it can be used for molar full crowns, the use of zirconia in which the alumina content is controlled to a very small amount is also progressing. In addition, zirconia designed to have high light transmittance is also used so that the content of yttria added as a stabilizer is increased to 5 mol% to 6 mol%, so that it can be used for full crowns of front teeth.

As the color tone of zirconia, there are white zirconia and colored zirconia adjusted to a color close to the color tone of natural teeth. The color tone of natural teeth changes from the cut portion corresponding to the enamel of the tooth to the cervical portion, and the chroma C* increases. For this reason, zirconia powder having different shades corresponding to the enamel color of the incisal portion and the cervical color is layered layer by layer so as to approach the color tone of the incisal portion and the cervical portion of natural teeth. Dental cutting consisting of a multi-layer structure in which a color gradation is formed. Techniques for molding ceramics blanks for machining are also being used.

Ceramics blanks for dental cutting processing having a multi-layer structure are characterized in that layers having different color tone, light transmittance, etc. are overlapped in various thicknesses.

On the other hand, when a ceramic blank for dental cutting with a multi-layer structure is cut into a crown shape, a crown that approximates the color tone of natural teeth to some extent is obtained. It was necessary to color the crown with a stain material or the like to adjust the color tone.

Patent Literature 1 describes a method of manufacturing into the shape of a crown by providing a block body having a plurality of curved layer structures and cutting the material. In this technology, imitating the structure of a layer in the shape of a natural tooth, imitating the color tone of a layer with a cervical color or enamel color, and the like are described. However, for practical use of the technology, a high-level manufacturing technology for imparting a curved layer structure to a block body is required, and it is predicted that cost is required.

Patent Document 2 describes a block technology having a plurality of layer structures. It is characterized by imitating the alveolar color or enamel color in the color tone of each layer and curving the structure of the layer. A prosthetic device cut from a block body in the art approximates the layered structure of a natural tooth. However, the technical description of the color design of each layer in the art remains only at the imitation of cervical color or enamel color. In the design of the curved layer structure, a layer structure with a patterned curved surface is assumed in consideration of practicality. However, because of this patterned layer structure, a certain amount of multiple layers (4 to 5 layers) are required to reproduce the color tone of natural teeth, and not only layering from light to dark tones step by step, but also adding additional color tones of each layer. Regulations are needed.

Patent Literature 3 describes a ceramic block technology for manufacturing by mixing two or more types of materials having different color tones. Specifically, as a ceramic block having a plurality of layer structures, it is characterized by producing intermediate colors by mixing two or more types of materials of different color tones, and setting it as a layer structure while changing the color tones of the intermediate colors. However, this technology does not have an appropriate color tone relationship between the layers, and it is necessary to designate an intermediate color tone in order to realize a color tone reproduction equivalent to that of a natural tooth.

Patent Literature 4 describes a molded member composed of two components having different color tones. Specifically, it consists of an alveolar color component layer and an enamel color component layer, and the shape of the interface between the respective component layers is defined in detail in a parabolic shape. By defining the interface shape as a parabola in this way, it becomes possible to give the cut prosthetic device a cervical color and enamel color structure close to natural teeth. For practical use of the technology, a method of using a mold/mold having a parabolic shape is exemplified. However, since it is necessary to mold the first layer and the second layer in this order, it is conceivable that the materials that can be used are limited, and that there are many technical problems such as difficulty in applying a uniform press pressure in molding. . In addition, there is no knowledge regarding a layer structure of three or more layers in the art.

Patent Literature 5 describes a multi-colored molded body having a layered structure. In this technology, two different color intermediate layers are provided between two main layers having different colors, and the color change of these intermediate layers is in the opposite direction to the color change direction of the main layers, and the intermediate layer has a thickness of 0.2 mm to 0.4 mm. Since it is a thin layer in mm, it is characterized in that the color change of the entire molded body is seen transitively. This is to continuously perceive the color change in the entire layer structure by using the color vision illusion of the observer. However, in the manufacture of a crown prosthetic device, in a molded article of limited thickness, providing a large number of thin layers with a thickness of 0.2 mm to 0.4 mm as an intermediate layer increases the difficulty in terms of manufacturing technology and is disadvantageous in terms of manufacturing cost. In addition, the brightness and chroma of the color tone of the enamel layer, the cervical layer, and the intermediate layer are not specified, and no specific proposal is made to obtain a color tone similar to that of natural teeth.

Patent Document 6 is a technique related to the color tone of a zirconia sintered body. Specifically, it is characterized in that the color tone of two points in the sintered body is defined respectively, and the increase/decrease tendency of the color tone change between the two points does not change. However, this technology defines the color tone at the 25% position in the surface layer of one end and the other end, and defines the color tone at the position of 45% and 55% in the middle layer. However, in order to obtain a prosthetic device closer to natural teeth, a technique having a color tone suitable for a more appropriate position is required. In particular, in the crown shape of molar teeth, a color tone higher than enamel color is required for the foveal fissure portion, and it is required to define the positional relationship of the colors of each layer.

Patent Document 7 describes a blank for cutting comprising a two-layer structure or a three-layer structure. Specifically, it is a technique to express the color tone change between layers in a transitive manner by specifying in detail the design of the curves of the interface between layers. In the color design of each layer in the art, the relationship between transparency and color tone of each layer is considered. However, regarding the design of the transparency and color tone of each layer, the concept is only described, and no clear setting has been made. That is, the design for the difference in transparency or color tone between each layer is not considered at all. This is because the technology solves the transition of color tone between layers by designing a curved line at the interface. Also in this technology, since the layer structure becomes a curved surface, various limitations arise in terms of manufacturing technology and cost.

Japanese Patent Publication No. 4-505113 International Publication No. 2002/09612 Japanese Unexamined Patent Publication No. 2004-35332 Japanese Published Patent Publication No. 2011-528597 Japanese Unexamined Patent Publication No. 2012-130798 Japanese Unexamined Patent Publication No. 2014-218389 International Publication No. 2015/051095

The foregoing prior art all relates to block-shaped coloration and layer structures cut by CAD/CAM systems. In these prior arts, since the technical details of setting the appropriate thickness of the enamel layer, the positional relationship of the intermediate layer, and color design were insufficient, ceramic blanks for dental cutting processing capable of producing dental prosthetic devices closer to natural teeth have been demanded.

In particular, in the case of molar crowns, it is required to reproduce the color tone of the occlusal surface that enters the visual field when the inside of the oral cavity is observed from the outside. Among the occlusal surfaces, the fissure area requires a color tone with a higher chroma C* than the enamel color, and a ceramic blank for dental cutting processing in which an appropriate positional relationship and an appropriate color tone design in the entire blank of the intermediate layer are required.

In addition, the color tone of the enamel portion of the crown of the anterior teeth is made on the cutting side, and the color tone of the vicinity of 1/3 of the crown is preferably approximately intermediate between the enamel color and the cervical color. Ceramics blanks for dental cutting processing in the prior art do not suggest setting an appropriate thickness of the enamel layer, the positional relationship of the intermediate layer, and color design. and ceramics blanks for dental cutting processing in which color design is specified.

In the present invention, the E layer ( _LE , _CE ) with the lowest chroma and the C layer ( _LC , _CC ) with the highest chroma are arranged in parallel on the upper and lower surface layers, respectively, and the M layer is in the middle of these two layers. (L _M , C _M ) A ceramics blank for dental cutting process consisting of a layer structure of 4 or more layers positioned in parallel, wherein the lightness L* and chroma C* in each layer satisfy the following relationship: provide blanks.

L _M = ( _LE + L _C )/2 × 0.97 to 1.03

C _M = (C _E + C _C )/2×0.93 to 1.07

C _C ＞C _M ＞C _E

The present invention provides a ceramic blank for dental cutting in which the chromaticity ( _LE , a _E , b _E ) of the E layer in the L*a*b* color system is within the following range.

65.0≤L _E ≤82.0

-4.0≤a _E ≤2.0

0.0≤b _E ≤20.0

In the ceramic blank for dental cutting according to the present invention, the E layer is in the range of 15% or more to 30% or less from the surface layer of the E layer, and the M layer is greater than 15% and less than or equal to 40% from the surface layer of the E layer. A range of ceramic blanks for dental cutting processing are provided.

The present invention provides a ceramics blank for dental cutting in which the layer M is adjacent to the layer E in the above ceramics blank for dental cutting.

The present invention provides a ceramic blank for dental cutting that is a zirconia calcined body produced by firing the ceramic blank for dental cutting at 800°C to 1200°C.

The present invention provides a ceramic blank for dental cutting, which is a zirconia sintered body, produced by sintering the ceramic blank for dental cutting at 1350°C to 1600°C.

The present invention is a dental prosthetic device manufactured by cutting any of the above ceramic blanks for dental cutting using a CAD/CAM system or by sintering after cutting.

It has been found that the ceramic blank for dental cutting of the present invention is suitable for more accurately reproducing the color tone of natural teeth in a cut dental prosthesis device by clarifying the color design of the intermediate layer.

In addition, since the thickness of the enamel layer is defined, the positional relationship and color design of the intermediate layer are clarified, and the laminated molded body is fired, the color tone of the dental prosthesis device reproduces the color tone of natural teeth by cutting and sintering. found something suitable for it.

In the present invention, the E layer ( _LE , _CE ) with the lowest chroma and the C layer ( _LC , _CC ) with the highest chroma are arranged in parallel on the upper and lower surface layers, respectively, and the M layer is in the middle of these two layers. (L _M , C _M ) is a ceramic blank for dental cutting process consisting of a layer structure of 4 or more layers positioned in parallel, wherein the lightness L* and chroma C* in each layer are

L _M = ( _LE + L _C )/2 × 0.97 to 1.03

C _M = (C _E + C _C )/2×0.93 to 1.07

C _C ＞C _M ＞C _E

Satisfies the relationship of, preferably

L _M = ( _LE + L _C )/2 × 0.99 to 1.01

C _M = (C _E + C _C )/2×0.95 to 1.05

C _C ＞C _M ＞C _E

is to satisfy

In addition, in the ceramic blank for dental cutting, the chromaticity ( _LE , a _E , b _E ) according to the L*a*b* color system of the E layer is

65.0≤L _E ≤82.0

-4.0≤a _E ≤2.0

0.0≤b _E ≤20.0

is in the range of, more preferably

69.0≤L _E ≤80.0

-3.0≤a _E≤1.0

2.0≤b _E ≤15.0

is in the range of

The chromaticity (L*a*b* color system) of each layer in the ceramic blank for dental cutting of the present invention can be measured by the following method. After producing the molded body of each layer, a test body (thickness: 1.2 mm) was obtained by polishing both surfaces (#800). Chromaticity (L* value, a* value, b* value) is calculated|required by colorimetry of the test body on a white bag.

In addition, the light transmittance of each layer in the ceramic blank for dental cutting of the present invention is not particularly limited, but when the light transmittance of each layer is expressed as a contrast ratio, it is preferable that any layer is in the range of 0.55 to 0.90. , more preferably in the range of 0.65 to 0.90. The contrast ratio can be measured by the following method. After producing the molded body of each layer, a test body (thickness: 1.0 mm) was obtained by polishing both surfaces (#800). The test body is colorimetric on white and black white, and each Y value measured (Y value measured on white bag is YW and Y value measured on black white is YB),

(Contrast ratio) = YB/YW

Calculate the contrast ratio from the formula of

In addition, in the ceramic blank for dental cutting, the chromaticity (L _M , a _M , b _M ) by the L*a*b* color system of the M layer is determined by the L*a*b* color system of the C layer and the E layer. There is no particular limitation as long as the above equation considering the chromaticity is satisfied.

67.0≤L _M ≤78.0

-2.5≤a _M ≤1.0

5.0≤b _M ≤15.0

It is desirable to be in the range of

In the ceramic blank for dental cutting, the E layer is present in a range of 15% or more to 30% or less in the surface layer of the E layer, preferably in a range of 20% or more to 30% or less in the surface layer of the E layer. Further, the M layer is greater than 15% from the surface layer of the E layer and is in the range of 40% or less, preferably greater than 25% from the surface layer of the E layer and is in the range of 40% or less. That is, the thickness of the M layer itself occupied in the thickness of the entire blank becomes 25% at the maximum. The thickness of the M layer itself, which occupies a preferred thickness of the entire blank, is 10 to 15%.

Since the present invention is a ceramic blank for dental cutting comprising a layer structure of four or more layers, it includes one or more intermediate layers in addition to the E layer, the M layer, and the C layer. One or more intermediate layers may be disposed between the E layer and the M layer, or may be disposed between the M layer and the C layer. Preferably, the E layer and the M layer are adjacent to each other, and one or more intermediate layers are disposed between the M layer and the C layer.

For example, in the case of a four-layer ceramic blank for dental cutting, one layer may be disposed between the M layer and the C layer. In addition, in the case of a five-layer ceramic blank for dental cutting, two layers having different color tones may be interposed between the M layer and the C layer. The more the number of layers, the more visually beautiful the color gradation, but aesthetically sufficiently good color reproducibility is obtained in blanks laminated with 4 to 7 layers, preferably 4 to 5 layers as a whole, to reproduce the color tone of natural teeth.

The thickness of the intermediate layer and the thickness of the C layer disposed between the M layer and the C layer are not limited. Considering the thickness of the E layer and the M layer and the thickness of the middle layer, the C layer is preferably in the range of 50% to 100% in the surface layer of the E layer, and more preferably in the range of 60% to 100% in the surface layer of the E layer. will be in That is, the thickness of C layer itself occupied by the thickness of the whole blank becomes 50% at most. The thickness of the C layer itself, which occupies a preferred thickness of the entire blank, is 30 to 40%.

In the E layer and C layer of the ceramic blank for dental cutting including four or more layers of the present invention, the E layer with the lowest chroma C* and the C layer with the highest chroma C* are arranged in parallel on the upper and lower surface layers of the blank, respectively. . On the premise that one side of layer E to layer C adapts to the lengthwise direction of the crown, the layer structure spanning layer E to layer C can be assumed to be a layer structure extending from the crown cutting portion to the cervical portion. On the other hand, natural teeth show enamel color because the cut portion is composed of only enamel in terms of structure, and since the enamel becomes thinner toward the cervical portion, the color of the cervical portion becomes darker. Thereby, in the ceramics blank for dental cutting of the present invention, the E layer can be designed in an enamel color and the C layer can be designed in a cervical color.

The relationship between the chroma C* of each layer is that the E layer has the lowest chroma C*, the C layer has the highest chroma C*, and the M layer's chroma C _M is (C _E + C _C )/2×0.93∼1.07. Therefore, the relationship is C _C > C _M > C _E. In the case of arranging the intermediate layer M2 between the M layer and the C layer, the relationship C _C ≥ C _M2 ≥ _{C M} > C _E is basic, but is not limited thereto. In addition, if the number of layers between the M layer and the C layer increases to two or three layers, a complex color tone design is obtained, but there is no problem even if the order of chroma C* is determined or partially changed. However, it is preferable that the order of the relationship between the chroma C* of the intermediate layer between the M layer and the C layer is determined.

Any materials such as zirconia, alumina, lithium disilicate glass, and aluminosilicate glass can be used for the ceramic blank for dental cutting of the present invention. Among them, it is preferable to use zirconia as a raw material.

Although the case where zirconia is selected as the raw material of the ceramic blank for dental cutting of the present invention is specifically described, it is not limited thereto.

The blank made of zirconia can be produced using any zirconia powder, such as zirconia powder containing a second element for characteristic improvement or secondary processed zirconia for moldability. For example, granular zirconia powder to which a binder suitable for press molding is provided, and zirconia powder to which no binder is added that can be manufactured by the slip casting method, and the like are exemplified.

In addition, there is no limitation at all even if oxides such as yttria (yttrium oxide), ceria (cerium oxide), carcia (calcium oxide), and magnesia (magnesium oxide) are added to the zirconia powder composition as a stabilizer. In order to ensure strength that can be used for a long period of time in the oral cavity, it is preferable to define the amount of the stabilizer so that the crystal structure is tetragonal. For example, when using yttria as a stabilizer, the content of yttria is preferably 2.5 mol% to 6 mol%. In addition, it is preferable to use zirconia powder to which 3 mol% is added when strength is important, and 4 mol% to 6 mol% is added when light transmittance is important.

Moreover, it is also preferable to use what added 0.01 mass % - 0.3 mass % of alumina (aluminum oxide) to the zirconia powder composition for the improvement of sinterability and suppression of low-temperature deterioration. However, when alumina is excessively added, the light transmittance is lowered, so it is preferable to use a zirconia powder added at 0.01% by mass to 0.25% by mass.

In addition, since the addition of silica (silicon oxide) to the zirconia powder composition affects the decrease in light transmittance, it is preferable to use a zirconia powder with a content of 0.05% by mass or less, and a zirconia powder with a content of 0.02% by mass or less. It is more preferable to use

The zirconia powder to be used may contain a pigment component for coloring. Examples of the pigment component include iron oxide, erbium oxide, cobalt oxide, manganese oxide, and prazeodymium oxide. You may use the zirconia powder which added these pigment components complexly.

In general, the C layer having high chroma C* uses a lot of zirconia powder having a higher pigment component content compared to the composition of the E layer.

The manufacturing method of the ceramic blank for dental cutting of the present invention is not particularly limited. It can be used in any form, such as using only zirconia powder, slurry in which zirconia powder is added to a solvent, or paste in which zirconia powder is bound, and molding them into a predetermined shape. .

In addition, any molding method may be used as a method for producing a molded article, and examples thereof include press molding, slip casting, injection molding, molding by stereolithography, and the like. Further, multi-stage molding, for example, CIP molding (cold constant isostatic press) may be performed after press molding as described in Examples of the present invention.

The ceramic blank for dental cutting of the present invention is used for cutting using a CAD/CAM system. In general, since the crown length of a natural tooth is 5 mm to 15 mm, the thickness of the blank of the present invention is preferably in the range of 10 mm to 20 mm to correspond to this. In addition, the shape of the blank of this invention may be any shape, such as a rectangular parallelepiped, a cylinder, and a disk, and there is no restriction|limiting. In addition, in consideration of processing with a CAD/CAM system, a gripping portion may be provided in advance so that gripping is possible. As an example, when the blank thickness direction is taken as the side surface, the shape of the blank as viewed from the top surface is a 12×16 mm rectangular parallelepiped for one tooth. In addition, as an example, the shape seen from the top of the blank is a circle of phi 98 to 100 mm for a large number of teeth.

When the ceramic blank for dental cutting of the present invention is made of zirconia, it is common to process it into a semi-sintered body, so the blank size is preferably enlarged taking into account the shrinkage of about 20% that occurs when it becomes a completely sintered body. Therefore, the thickness of the blank is also increased by about 20%. The size of the blank is a size that can be used in the CAD/CAM system.

In the case where a binder is contained in the zirconia powder molded in the step of obtaining a calcined body or a sintered body of the ceramic blank for dental cutting of the present invention, it is preferable to degrease the binder. It is preferable to degrease at a slow heating rate while taking time so that the shape of the molded body does not collapse from room temperature to 600 ° C.

When the ceramic blank for dental cutting of the present invention is a zirconia material, the zirconia calcined body can be obtained by firing at 800°C to 1200°C under atmospheric pressure. It is also possible to perform degreasing and calcining in a series of steps.

When the ceramic blank for dental cutting of the present invention is a sintered body of zirconia, it can be obtained by firing at atmospheric pressure at 1350°C to 1600°C. In this case, you may sinter at 1350 degreeC - 1600 degreeC at atmospheric pressure of the calcined body previously made into a calcined body.

When the ceramics blank for dental cutting of the present invention is aluminosilicate glass or lithium disilicate glass, the fired body can be obtained by firing at 700°C to 1000°C under atmospheric pressure.

The ceramic blank for dental cutting of the present invention is cut into a crown shape by a CAD/CAM system. A material that can be used as a prosthetic device in a state of being cut is finished by fine-tuning the shape as a post-process, firing a stain material in some cases, firing a glazing material to give a gloss, or polishing. When the ceramics blank for dental cutting is a plastic body, it is cut into a crown shape and sintered at the sintering temperature of the material. In the case of zirconia, it is sintered at 1350°C to 1600°C. After sintering, it is completed by performing a post-process similar to the above.

Next, a case of manufacturing a zirconia blank will be described as an example of a method for manufacturing a ceramic blank for dental cutting of the present invention.

Several types of white and colored zirconia powders are selected and mixed in an appropriate mixing ratio to obtain enamel color and cervical color. When the enamel color formulation is E color, for example, E color has a high proportion of white zirconia powder and a low proportion of colored zirconia powder containing iron oxide or erbium oxide. When the alveolar color formulation is C color, the ratio of the colored zirconia powder containing iron oxide or erbium oxide in the cervical color increases. M layer is mixed so that the ratio of E color and C color is 50:50. If the middle layer between the M layer and the C layer is one layer and the middle layer is M2 color, for example, M2 color is mixed so that the ratio of E color and C color is 25:75.

Next, E color, M color, M2 color, and C color are laminated to a predetermined thickness. For example, after filling the mold with E color, it is evenly leveled. Pressing may be performed lightly once, or the lower mold may be lowered so as to have a predetermined thickness as it is, and the M color may be filled. The powder may be filled in terms of weight, or the powder may be filled in terms of volume. In the case of volume conversion, there is also a method of filling up to the upper surface of the mold. Next, M2 color and C color are filled in the same manner as described above. After all layers are laminated, press molding is performed to obtain a molded body. The molded body may be subjected to CIP molding (cold constant isostatic pressure molding).

A calcined body is obtained by degreasing the molded body over time from room temperature to 600°C and then firing it at 800°C to 1200°C. The degreasing step may be omitted, and a calcined body may be obtained by firing in a series of steps.

The resulting calcined body is cut into a crown shape using a CAD/CAM system and sintered at 1350°C to 1600°C to obtain a dental prosthetic device.

When the sintered body sintered at 1350°C to 1600°C is cut into a crown shape using a CAD/CAM system, a dental prosthesis device can be obtained as it is.

In addition, in the said embodiment, although the calcined body and sintered body based on 4 layers of blanks were illustrated, it is not limited to 4 layers. In addition, the combination of color M and the color tone of the intermediate layer is not limited to mixing E color and color C, and color M or the color tone of the intermediate layer may be combined by original formulation.

Example

Hereinafter, the present invention will be described in more detail and specifically with reference to examples, but the present invention is not limited thereto. In this embodiment, a ceramic blank for dental cutting using zirconia powder will be described.

(Preparation of zirconia powder in each layer)

Four types of powder were used: zirconia powder (white), zirconia powder (dark brown), zirconia powder (pink), and zirconia powder (gray). E, M, C, and intermediate layers between the M and C layers were mixed to obtain desired color tone and light transmittance (contrast ratio), respectively, to obtain E, M, C, and M2 colors. In addition, the E color, M color, C color, and M2 color of Examples 1 to 5 and Comparative Examples 1 to 3 are all different in the zirconia powder or mixing ratio used.

[Example 1]

The zirconia powder used in Example 1 was a powder having an yttria content of 5.5 mol%. In the tables, numerical values in mol% are described as the yttria content of the zirconia powder used.

(Preparation of samples for measuring color tone and contrast ratio)

After filling 2 g of the E color zirconia mixed powder into a φ20 mold, press molding was performed at a pressure of 10 kN for 1 minute. After performing press molding, CIP molding was performed for 1 minute at a pressure of 200 MPa. The degreasing of the press-formed body was heated up to 500°C at a heating rate of 50°C/hour, and cooled to room temperature at a temperature-decreasing rate of 100°C/hour after mooring for 2 hours. After degreasing, the temperature was raised to 1450°C at a temperature increase rate of 100°C/hour, and after mooring for 2 hours, it was left to cool in the furnace to obtain a sintered body. The sintered body for M color and C color was also manufactured in the same process.

The thickness of the obtained sintered body was adjusted using a flat polishing machine, and final polishing was performed with a #800 diamond polishing stone. Two types of round plates were prepared, one with a final thickness of 1.2 mm (for color tone measurement) and one with a final thickness of 1.0 mm (sample for contrast ratio measurement).

(Hue and contrast ratio measurement)

The color tone was measured using a spectrophotometer (CM-3500d: Konica Minolta), and the chromaticity (L*, a*, b*) of white color was measured using a 1.2 mm sample. For the measurement of the contrast ratio, a Y value (YW) measured on a white bag and a Y value (YB) measured on a black bag were measured using a sample having a thickness of 1.0 mm, and YB/YW was taken as the contrast ratio.

Chroma C* is calculated from the chromaticity (L*, a*, b*) of each layer, and if (L _M , C _M ) of the M layer satisfies the following relationship, it is “conforming”, otherwise it is not satisfied. Indicated as "unsuitable".

L _M = ( _LE + L _C )/2 × 0.97 to 1.03

C _M = (C _E + C _C )/2×0.93 to 1.07

C _C ＞C _M ＞C _E

From the colorimetric results of the E layer, when the chromaticity (L*, a*, b*) was within the following range, it was indicated as “acceptable” as the chromaticity of the E layer, and “unacceptable” when it was out of the range.

65.0≤L _E ≤82.0

-4.0≤a _E ≤2.0

0.0≤b _E ≤20.0

Table 1 shows the measurement results of color tone of E color, M color, and C color, chromaticity, and contrast ratio measurement results of Example 1. In addition, it was shown whether the (L _M , C _M ) of the M layer and the chromaticities (L*, a*, b*) of the E layer were suitable from the measurement results.

From the measurement results of color tone of E color, M color, and C color in Example 1, it was confirmed that the (L _M , C _M ) of the M layer and the chromaticities (L*, a*, b*) of the E layer were suitable. .

(Manufacture of ceramic blanks for dental cutting)

A zirconia blank having a four-layer structure was manufactured using the zirconia mixed powder of each layer prepared in Example 1. A mold of φ20 was first filled with E-color zirconia mixed powder to a thickness of 15% of the entire blank, and pressed at a pressure of 1 kN for 15 seconds. Thereafter, M color zirconia mixed powder was filled to a thickness of 25%, and pressed at a pressure of 1 kN for 15 seconds. Filling and pressing were performed in the same way for the intermediate layer between the M color and the C color, and finally, the C color zirconia mixture powder was filled to a thickness of 35%, and press molding was performed at a pressure of 10 kN for 1 minute. The obtained press-formed body having a four-layer structure was subjected to CIP molding at a pressure of 200 MPa for 1 minute. After CIP molding, the temperature was raised to 500 ° C at a temperature rising rate of 60 ° C / hour, moored for 2 hours, heated to 1000 ° C at a temperature rising rate of 60 ° C / hour, moored for 2 hours, cooled in a furnace to obtain a zirconia calcined body, It was used as a ceramic blank for dental cutting.

In the tables in Examples and Comparative Examples, the thickness of the ceramic blank for dental cutting was described as a ratio of the entire thickness of the blank to the surface layer of the E layer as a starting point. Since the surface layer of the E layer is 0% and the surface layer of the C layer is 100%, for example, if the thickness of the E layer is 30% of the thickness of the entire blank, the thickness of the E layer is expressed as 0 to 30%.

The thickness of the M layer was expressed as the thickness of the uppermost surface (the surface close to the E layer) and the lowermost surface (the surface farther from the E layer) of the M layer, starting from the surface layer of the E layer. In Example 1, since the uppermost surface of the M layer is located at 15% of the surface layer of the E layer and the lowermost surface of the M layer is located at 40% of the surface layer of the E layer, the thickness of the M layer is expressed as 15 to 40%. The thickness of the layer itself was 25% of the entire blank. In addition, the number of laminated layers is expressed as the total number of layers, and in Example 1, it is expressed as 4 because it is a blank having a 4-layer structure.

(Evaluation of color reproducibility of prosthetic devices)

A mounting pin for processing was bonded to a ceramic blank for dental cutting processing, which is a zirconia plastic body, and cut using a dental CAD/CAM cutting machine DWX-50 (Roland) to manufacture a crown of the lower right first molar tooth. The processed crown was heated up to 1450° C. at a heating rate of 5° C./min, held for 2 hours, and then allowed to cool in a furnace to obtain a crown, which is a dental prosthetic device for color reproducibility evaluation.

The manufactured crown was visually observed to evaluate color reproducibility (enamel color and cervical color expression) as a dental prosthetic device. The evaluation of color reproducibility was indicated by ○: good color reproducibility, x: poor color reproducibility.

The dental prosthetic device cut and sintered by the CAD/CAM system exhibited the same appearance as a natural tooth from the E layer to the C layer, and had excellent color reproducibility.

[Example 2]

The zirconia powder used in Example 2 was a powder having an yttria content of 5.5 mol%.

Preparation of a sample for measuring color tone and contrast ratio and measurement of color tone and contrast ratio were carried out in the same process as in Example 1.

From the measurement results of color tone of E color, M color, and C color in Example 2, it was confirmed that the (L _M , C _M ) of the M layer and the chromaticity (L*, a*, b*) of the E layer were suitable. .

(Manufacture of ceramic blanks for dental cutting)

It was carried out in the same production method as in Example 1, but the E color zirconia powder was filled to a thickness of 30% of the entire blank, and the M color zirconia powder was filled to a thickness of 10% of the entire blank. In addition, the intermediate layer between the M color and the C color was made into two layers, and a zirconia calcined body having a five-layer structure as a whole.

(Evaluation of color reproducibility of prosthetic devices)

The evaluation method was carried out in the same process as in Example 1.

The dental prosthetic device cut and sintered by the CAD/CAM system exhibited the same appearance as a natural tooth from the E layer to the C layer, and exhibited excellent color reproducibility.

[Example 3]

The zirconia powder used in Example 3 was a powder having an yttria content of 5.5 mol%.

Preparation of a sample for measuring color tone and contrast ratio and measurement of color tone and contrast ratio were carried out in the same process as in Example 1.

From the measurement results of color tone of E color, M color, and C color in Example 3, it was confirmed that the (L _M , C _M ) of the M layer and the chromaticities (L*, a*, b*) of the E layer were suitable. .

(Manufacture of ceramic blanks for dental cutting)

It was carried out in the same production method as in Example 1, but the E color zirconia powder was filled to a thickness of 30% of the entire blank, and the M color zirconia powder was filled to a thickness of 10% of the entire blank. In addition, the intermediate layer between the M color and the C color was made into two layers, and a zirconia calcined body having a five-layer structure as a whole.

(Evaluation of color reproducibility of prosthetic devices)

The evaluation method was carried out in the same process as in Example 1.

The dental prosthetic device cut and sintered by the CAD/CAM system exhibited the same appearance as a natural tooth from the E layer to the C layer, and had excellent color reproducibility. Compared to Example 2, since the E color and C color saturation C* was high, the entire crown was dark in tone.

[Example 4]

The zirconia powder used in Example 4 was a powder having an yttria content of 3.0 mol%.

Preparation of a sample for measuring color tone and contrast ratio and measurement of color tone and contrast ratio were carried out in the same process as in Example 1.

From the measurement results of color tone of E color, M color, and C color in Example 4, it was confirmed that the (L _M , C _M ) of the M layer and the chromaticities (L*, a*, b*) of the E layer were suitable. .

(Manufacture of ceramic blanks for dental cutting)

It was carried out in the same manufacturing method as in Example 1.

(Evaluation of color reproducibility of prosthetic devices)

The evaluation method was carried out in the same process as in Example 1.

The dental prosthetic device cut and sintered by the CAD/CAM system exhibited the same appearance as a natural tooth from the E layer to the C layer, and had excellent color reproducibility. Compared to Example 1, the E color and C color contrast ratios were higher, so the entire crown had an opaque color tone compared to Example 1.

[Example 5]

The zirconia powder used in Example 5 was a powder having an yttria content of 3.0 mol%.

Preparation of a sample for measuring color tone and contrast ratio and measurement of color tone and contrast ratio were carried out in the same process as in Example 1.

From the measurement results of color tone of E color, M color, and C color in Example 5, it was confirmed that the (L _M , C _M ) of the M layer and the chromaticity (L*, a*, b*) of the E layer were suitable. .

(Manufacture of ceramic blanks for dental cutting)

It was carried out in the same production method as in Example 1, but the E color zirconia powder was filled to a thickness of 30% of the entire blank, and the M color zirconia powder was filled to a thickness of 10% of the entire blank. In addition, the intermediate layer between the M color and the C color was made into two layers, and a zirconia calcined body having a five-layer structure as a whole.

(Evaluation of color reproducibility of prosthetic devices)

The evaluation method was carried out in the same process as in Example 1.

The dental prosthetic device cut and sintered by the CAD/CAM system exhibited the same appearance as a natural tooth from the E layer to the C layer, and had excellent color reproducibility. Compared to Example 1, the E color and C color contrast ratio was higher, so the entire crown was more opaque than Example 1 and had a lighter color tone than Example 4.

[Comparative Example 1]

The zirconia powder used in Comparative Example 1 was a powder having an yttria content of 5.5 mol%.

Preparation of a sample for measuring color tone and contrast ratio and measurement of color tone and contrast ratio were carried out in the same process as in Example 1.

From the measurement results of color tone of E color, M color, and C color in Comparative Example 1, C _M of M layer was small, and C _M = (C _E + C _C )/2 × 0.93 to 1.07 could not be satisfied. It was confirmed that the chromaticities (L*, a*, b*) of the E layer were suitable.

(Manufacture of ceramic blanks for dental cutting)

It was carried out in the same manufacturing method as in Example 1, but the E color zirconia powder was filled to a thickness of 35% of the total blank, and the M color zirconia powder was filled to a thickness of 15% of the total blank. In addition, the intermediate layer between the M color and the C color was made into one layer, and it was made into a zirconia calcined body having a four-layer structure as a whole.

(Evaluation of color reproducibility of prosthetic devices)

The evaluation method was carried out in the same process as in Example 1.

In the dental prosthetic device cut and sintered by the CAD/CAM system, the chroma C _M of the M layer is small, deviates from the relationship of (C _E + C _C )/2×0.93 to 1.07, and the position of the M layer is In 35% to 50%, the color tone seen from the occlusal surface of the premolars was all enamel color, and the reproducibility of the color tone of natural teeth was poor.

[Comparative Example 2]

The zirconia powder used in Comparative Example 2 was a powder having an yttria content of 5.5 mol%.

Preparation of a sample for measuring color tone and contrast ratio and measurement of color tone and contrast ratio were carried out in the same process as in Example 1.

From the measurement results of E color, M color, and C color tone in Comparative Example 2, CM of _M layer was small, and CM = (C _E + C _C ) / 2 × 0.93 to 1.07 could not be satisfied. It was confirmed that the chromaticities (L*, a*, b*) of the E layer were suitable.

(Manufacture of ceramic blanks for dental cutting)

It was carried out in the same manufacturing method as in Example 1, but the E color zirconia powder was filled to a thickness of 25% of the total blank, and the M color zirconia powder was filled to a thickness of 15% of the total blank. In addition, the intermediate layer between the M color and the C color was made into one layer, and it was made into a zirconia calcined body having a four-layer structure as a whole.

(Evaluation of color reproducibility of prosthetic devices)

The evaluation method was carried out in the same process as in Example 1.

In the dental prosthetic device cut and sintered by the CAD/CAM system, the chroma C _M of the M layer is small, deviates from the relationship of (C _E + C _C )/2×0.93 to 1.07, and the position of the M layer is 25 Although it was % to 40%, the color tone seen from the occlusal surface of the premolar teeth was all enamel color, and the reproducibility of the color tone of natural teeth was poor.

[Comparative Example 3]

The zirconia powder used in Comparative Example 3 was a powder having an yttria content of 3.0 mol%.

Preparation of a sample for measuring color tone and contrast ratio and measurement of color tone and contrast ratio were carried out in the same steps as in Example 1.

From the measurement results of color tone of E color, M color, and C color in Comparative Example 3, C _M of M layer was small, and C _M = (C _E + C _C )/2 × 0.93 to 1.07 could not be satisfied. It was confirmed that the chromaticities (L*, a*, b*) of the E layer were suitable.

(Manufacture of ceramic blanks for dental cutting)

It was carried out in the same production method as in Example 1, but the E color zirconia powder was filled to a thickness of 30% of the entire blank, and the M color zirconia powder was filled to a thickness of 10% of the entire blank. In addition, the intermediate layer between the M color and the C color was made into two layers, and a zirconia calcined body having a five-layer structure as a whole.

(Evaluation of color reproducibility of prosthetic devices)

The evaluation method was carried out in the same process as in Example 1.

In the dental prosthetic device cut and sintered by the CAD/CAM system, the chroma C _M of the M layer is small and deviates from the relationship of (C _E + C _C )/2×0.93 to 1.07, so the occlusal surface of the small molars The color tone seen in was all enamel color, and the reproducibility of the color tone of natural teeth was poor.

The present invention is a ceramic blank for dental cutting, which has a multilayer structure of four or more layers and has a characteristic color tone distribution in the layer structure, which is used for cutting by a CAD/CAM system in the field of dentistry. It can be used for blocks and disks for manufacturing calcined bodies, sintered bodies, and dental prosthetic devices cut using them.

Claims (7)

On the upper and lower surface layers, the E layer ( _LE , _CE ) with the lowest chroma and the C layer ( _LC , C _C ) with the highest chroma are arranged in parallel, respectively, and the M layer (L _M , C _M ) is a ceramic blank for dental cutting processing consisting of a layer structure of 4 or more layers positioned in parallel,
The lightness L* and chroma C* in each layer satisfy the following relationship:
L _M = ( _LE + L _C )/2 × 0.97 to 1.03
C _M = (C _E + C _C )/2×0.93 to 1.07
C _C ＞C _M ＞C _E ,
The M layer is adjacent to the E layer, and the thickness of the E layer is in the range of 15% or more to 30% or less with respect to the thickness of the entire dental cutting ceramics blank starting from the surface layer of the E layer, and the thickness of the M layer is E It is in the range of more than 15% and less than 40% with respect to the thickness of the entire ceramics blank for dental cutting, starting from the surface layer of the layer,
A ceramic blank for dental cutting, characterized in that the chromaticity (L _M , a _M , b _M ) of the M layer by the L*a*b* color system is within the following range:
67.0≤L _M ≤78.0
-2.5≤a _M ≤1.0
5.0≤b _M ≤15.0. According to claim 1,
A ceramic blank for dental cutting characterized in that the chromaticity ( _LE , a _E , b _E ) of the E layer by the L*a*b* color system is within the following range:
65.0≤L _E ≤82.0
-4.0≤a _E ≤2.0
0.0≤b _E ≤20.0. delete delete According to claim 1 or 2,
A ceramic blank for dental cutting, characterized in that it is a zirconia calcined body produced by firing the ceramic blank for dental cutting at 800°C to 1200°C. According to claim 1 or 2,
A ceramic blank for dental cutting, characterized in that it is a zirconia sintered body produced by sintering the ceramic blank for dental cutting at 1350°C to 1600°C. A dental prosthetic device characterized in that it is manufactured by cutting with a CAD/CAM system using the ceramic blank for dental cutting according to claim 1 or 2, or by sintering after cutting.