阅读说明：本技术 牙科修复体用块体 (Block for dental restoration ) 是由 加藤克人 秋山茂范 东利彦 于 2020-01-09 设计创作，主要内容包括：牙科修复体用块体为柱状或板状,主要晶相为焦硅酸锂,并且,在将牙科修复体用块体的切断面的一部分放大后的视野内进行观察时,放大后的视野内存在的具有0.5μm以上的长度的晶体所占的面积的总和相对于放大后的视野的面积的比率为21％以下。(The dental restoration block has a columnar or plate shape, has a main crystal phase of lithium disilicate, and has a ratio of a total area occupied by crystals having a length of 0.5 [ mu ] m or more present in a magnified visual field to an area of the magnified visual field of 21% or less when observed in the visual field in which a part of a cut surface of the dental restoration block is magnified.)

1. A dental restoration block which is used before machining for producing a dental restoration, wherein,

the block for dental restoration is columnar or plate-shaped, has a main crystal phase of lithium disilicate, and,

when observed in a field of view in which a part of a cut surface of the block for a dental restoration is enlarged, a ratio of a total sum of areas occupied by crystals having a length of 0.5 μm or more present in the enlarged field of view to an area of the enlarged field of view is 21% or less.

2. The block for a dental restoration as set forth in claim 1, wherein the ratio is 1% or less.

3. The block for dental restoration according to claim 1 or 2, wherein 60 mass% or more and 80 mass% or less of SiO is contained₂10 to 20 mass% of Li₂3 to 15 mass% of Al₂O₃And 4.2 to 10 mass% of P₂O₅。

4. The block for dental restoration according to claim 1 or 2, wherein 60 mass% or more and 80 mass% or less of SiO is contained₂10 to 20 mass% of Li₂3 to 15 mass% of Al₂O₃And 5 to 10 mass% of P₂O₅。

5. The block for a dental restoration as set forth in any one of claims 3 or 4, wherein an oxide of at least one element selected from the group consisting of Na, K, Ca, Sr, Ba, Mg, Rb, Cs, Fr, Be, and Ra is contained.

6. The block for a dental restoration as set forth in any one of claims 3 to 5, wherein at least one of oxides of Ti and Zr is contained.

7. The method of any one of claims 3 to 6A block for dental restoration, comprising V₂O₅、CeO₂、Er₂O₃、MnO、Fe₂O₃And Tb₄O₇At least one of (1).

8. The block for a dental restoration according to any one of claims 1 to 7, wherein the machining is a cutting machining.

9. The block for a dental restoration according to any one of claims 1 to 8, wherein an area occupied by voids in a cut surface is 2% or less on average.

10. The block for a dental restoration according to any one of claims 1 to 9, wherein the granular material of the coloring material is not observed in a micrograph in which a magnification of a cross section is 200 times.

Technical Field

The present invention relates to a block for a dental restoration.

Background

With the recent development of CAD/CAM (computer aided design/computer aided manufacturing) technology, in the manufacture of a dental prosthesis, the shape of the designed dental prosthesis is processed by digital data converted into a predetermined form, and the data is transmitted to a machining device, whereby the machining device automatically performs machining such as cutting and grinding based on the data to manufacture the dental prosthesis. Thereby, the dental restoration can be provided promptly.

Such a dental prosthesis is required to have basic functions as a dental prosthesis, i.e., strength, hardness, chemical durability against the intra-oral environment, and aesthetic properties (color tone, texture) similar to those of natural teeth.

In addition, the dental prosthesis has complicated unevenness, and it is important to machine a complicated shape in a short time without causing defects such as chipping. By making such a material that can be processed in a short time, a dental prosthesis can be produced more quickly.

Patent document 1 discloses a dental restorative material containing a predetermined component, whereby the basic function and the machinability are improved.

Documents of the prior art

Patent document

Patent document 1: international publication No. WO2016/031399

Disclosure of Invention

Problems to be solved by the invention

The invention provides a dental restoration block with good machinability.

Means for solving the problems

One embodiment of the present invention is a dental restoration block before machining for producing a dental restoration, wherein the dental restoration block has a columnar or plate shape, a main crystal phase is lithium disilicate, and a ratio of a total sum of areas occupied by crystals having a length of 0.5 μm or more present in a magnified visual field to an area of the magnified visual field is 21% or less when observed in the visual field in which a part of a cut surface of the dental restoration block is magnified.

Here, the "main crystal phase" refers to a crystal phase in which the crystal precipitation ratio is the largest among crystal phases observed by analysis using an X-ray diffraction apparatus. The same applies below.

The ratio may be set to 1% or less.

The above dental restoration block may contain 60 mass% to 80 mass% of SiO₂10 to 20 mass% of Li₂3 to 15 mass% of Al₂O₃And 4.2 to 10 mass% of P₂O₅The method (1) is as follows.

The above dental restoration block may contain 60 mass% to 80 mass% of SiO₂10 to 20 mass% of Li₂3 to 15 mass% of Al₂O₃And 5 to 10 mass% of P₂O₅The method (1) is as follows.

Further comprises an oxide of at least one element selected from the group consisting of Na, K, Ca, Sr, Ba, Mg, Rb, Cs, Fr, Be and Ra.

At least one of oxides of Ti and Zr may also be included.

May further comprise a compound selected from V₂O₅、CeO₂、Er₂O₃、MnO、Fe₂O₃And Tb₄O₇At least one of (1).

The machining may be cutting.

The dental restoration block may be configured such that an average area occupied by the voids in the cut surface is 2% or less.

The above dental restoration block may be configured such that no granular coloring material is observed in a micrograph of a cut surface at a magnification of 200.

Effects of the invention

According to the present invention, a dental restoration block having excellent machinability can be obtained.

Drawings

Fig. 1 is an external perspective view of a block 10 for a dental restoration.

Fig. 2 is an enlarged view of a part of the cut surface to show the crystal.

Fig. 3 is a diagram for explaining a method of measuring the contrast ratio.

Fig. 4 is another diagram for explaining a method of measuring the contrast ratio.

Detailed Description

Specific embodiments will be described below. However, the present invention is not limited to these embodiments.

A dental restoration block according to one embodiment (hereinafter, sometimes referred to as "block") is a columnar or plate-like (disc-like) block such as a prism or a cylinder, and a dental restoration is produced by deforming and cutting the block by machining such as cutting or grinding. In the case of manufacturing a dental prosthesis by cutting, a prism or a plate (disk) shape may be made. Prismatic blocks are mostly used primarily for cutting out a single dental restoration, while plate-like blocks are sometimes used for cutting out multiple dental restorations from one block.

Fig. 1 shows an external perspective view of a block 10 as a prism. In the case of a prism, the width W, the depth D, and the height H may be set to ranges of 10mm to 35mm, respectively. On the other hand, in the case of a plate-shaped block, the thickness may be in the range of 10mm to 35 mm.

This makes it easy to manufacture the dental prosthesis by cutting.

The block 10 of the present embodiment shown in fig. 1 has the following structure. In FIG. 2 it is shown that the symbol A in FIG. 1 will be followed₁A broken line is shown to show a partially enlarged view of a cut surface of the block 10. This figure is an enlarged view in a field of view having a longitudinal direction (width direction) of 5 μm and a lateral direction (depth direction) of 5 μm. Such a map can be obtained by Scanning Electron Microscope (SEM) images.

The predominant crystalline phase of the bulk 10 is lithium disilicate. Here, the "main crystal phase" refers to a crystal phase in which the crystal precipitation ratio is the largest among crystal phases observed by analysis using an X-ray diffraction apparatus.

In addition, regarding the bulk 10, when crystals having a length of 0.5 μm or more are extracted from among the respective crystals appearing in the visual field range shown in fig. 2, the total of the areas of the extracted crystals is a ratio of 21% or less with respect to the area (5 μm × 5 μm) of the visual field shown in fig. 2. This ratio is preferably 10% or less, and more preferably 1% or less.

Thus, even if a bulk body having lithium disilicate as a main crystal phase is produced, cutting and grinding can be performed under conditions equal to or higher than those for processing a bulk body made of a material which is easy to process (for example, lithium metasilicate as a main crystal phase). Further, according to this, for example, heat treatment after machining which is necessary for a bulk body having lithium metasilicate as a main crystal phase is not necessary, and therefore, a dental prosthesis can be produced in a state where the accuracy of machining is maintained without changing the shape.

Such a ratio is obtained as follows.

Taking the block 10 shown in fig. 1 as an example, the center a is obtained in the maximum direction (in the example of fig. 1, the height direction)₁And two end portions A at positions 10% from the end face with respect to the total height H₂And end part A₃Three cut surfaces at (c). FIG. 3 shows the center A of the three cut surfaces₁The cut surface of (d).

Then, for center A₁End part A₂End part A₃Each cut surface of (A) is directed to a center B indicated by a dotted line₁With respect to the B₁Two end portions B adjacent to each other in the width W direction and at a position of 10% from the end portion with respect to the full width W₂And relative to the center B₁Two end portions B adjacent to each other in the direction of the depth D and at positions 10% of the total depth D from the end portions₃Images obtained by scanning electron microscopy were obtained in 5 μm × 5 μm fields as shown in fig. 2. Thus, 5 images and 15 images were obtained for each cut surface. An example of the obtained image is shown in the upper part of fig. 4.

Next, as shown in the lower part of fig. 4, crystals having a length of 0.5 μm or more (a portion shown in the lower part of fig. 4) among the crystals appearing in each image were extracted, and the total sum S of the areas of the crystals was obtained. Then, the sum S of the areas is divided by the visual field area S of the image₀(5 μm. times.5 μm) and expressed in percentage, the ratio (S/S) was obtained for each image separately₀X 100%). Thus, a total of 15 individual ratios were obtained.

Then, the average of these individual ratios is calculated and used as the ratio.

The ratio obtained as described above can be set to 21% or less.

The block of the present embodiment may be constituted by containing the following components. And, its main crystal phase is lithium disilicate.

60 to 80 mass% SiO₂、

10 to 20 mass% of Li₂O、

3 to 15 mass% of Al₂O₃、

4.2 to 10 mass% of P₂O₅。

The above components are as follows.

SiO₂When the content of (b) is less than 60% by mass or exceeds 80% by mass, it is difficult to obtain a homogeneous mass. More preferably 65% by mass or more and 75% by mass or less.

Li₂When the content of O is less than 10 mass% or exceeds 20 mass%, it is difficult to obtain a homogeneous mass and machinability tends to decrease. More preferably 12% by mass or more and 18% by mass or less.

Al₂O₃When the content of (b) is less than 3% by mass, lithium disilicate precipitates as a main crystal phase, but machinability tends to be lowered. On the other hand, if it exceeds 15 mass%, the main crystal phase is not lithium disilicate, and the strength tends to decrease. More preferably 3% by mass or more and 7% by mass or less.

P₂O₅When the content of (b) is less than 4.2% by mass, crystals having a length of 0.5 μm or more tend to increase, and there is a possibility that machinability may be lowered. Preferably 5% by mass or more. On the other hand, if the content exceeds 10% by mass, the block tends to be devitrified and it becomes difficult to obtain a transparent block.

Further, the dental restoration block may contain the following components in addition to the above components. However, as is clear from the fact that the components shown here are contained in an amount of 0 mass%, they do not necessarily need to be contained, and any of them may be contained.

The content of the component for adjusting the melting temperature may be 0% by mass or more and 15% by mass or less. This makes it possible to adjust the melting temperature appropriately in the production described later. The content of each component may be more than 15% by mass, but the improvement of the effect is limited. Specific examples of the melting temperature control material include oxides of Na, K, Ca, Sr, Ba, Mg, Rb, Cs, Fr, Be, and Ra. Further preferably, the following is mentioned.

Na₂O: 2.8% by mass or less

K₂O: 10 mass% or less

CaO: 3% by mass or less

SrO: 10 mass% or less

BaO: 10 mass% or less

MgO: 3% by mass or less

Rb₂O: 2.8% by mass or less

Cs₂O: 2.8% by mass or less

Fr₂O: 2.8% by mass or less

BeO: 3% by mass or less

RaO: 10 mass% or less

In addition, the first and second substrates are,the crystal nucleus-forming component may be contained in a total amount of 0 to 10 mass%. This enables efficient generation of nuclei for forming lithium disilicate crystals. However, even if the compound is contained in an amount exceeding the above range, the improvement of the effect is limited, and therefore, the content is set to 10% by mass or less. Examples of the compound functioning as a crystal nucleus-forming material include oxides of Zr and Ti (ZrO)₂、TiO₂). In this case, it is preferable to contain a compound selected from ZrO₂And TiO₂And the total amount thereof is 0 mass% or more and 10 mass% or less.

The dental restoration block may further contain a known colorant from the viewpoint of enhancing aesthetic quality. This may be exemplified by a selection from V₂O₅、CeO₂、Er₂O₃、MnO、Fe₂O₃、Tb₄O₇At least one of (1).

Here, it is preferable that no voids are observed in the block for dental restorations. However, since the influence of a few voids is considered to be small, it is preferable that the area occupied by voids in the observation range of 60 μm in the longitudinal direction (width direction) × 60 μm in the lateral direction (depth direction) is 2% or less on average at 15 sites where the above ratio is measured.

Preferably, the colored material is not visually observed in 15 portions at which the above ratio is measured in a photomicrograph at a magnification of 200.

These voids and particles may form an interface with the base material, thereby affecting machinability. In addition, the presence of the granular substance of the coloring material may also cause color unevenness of the dental restoration.

Such a block for a dental restoration can be reliably realized by molding by melting of a material as described later, instead of powder molding.

The dental restoration block and the dental restoration manufactured by processing the same can have basic functions as a dental restoration, that is, strength, hardness, chemical durability to the oral cavity environment, and aesthetic properties (color tone and texture) similar to those of natural teeth. In addition, the machinability is improved, and the ceramic block can be machined without causing defects under machining conditions of the same degree or more as those of conventional ceramic blocks for cutting, although the ceramic block has such strength that heat treatment after machining is not necessary.

Next, an example of a method of manufacturing a dental prosthesis will be described. Included herein is a method of making a block for a dental restoration. The manufacturing method of the present embodiment includes a melting step, a glass material manufacturing step, a nucleation step, a heat treatment step, a cooling step, and a processing step.

In the melting step, the components described above are melted at 1100 ℃ to 1600 ℃. Thereby, a molten glass for a dental restoration block can be obtained. In order to obtain sufficiently uniform properties, the melting is preferably performed for several hours.

The glass material producing step is a step of obtaining a glass material having a shape close to the shape of the dental restoration block. The molten glass obtained in the melting step is poured into a mold and cooled to room temperature, thereby obtaining a glass material. This cooling is performed by a slow temperature change in order to prevent deterioration and cracking of the material.

The nucleation step is a step of heating the glass material obtained in the glass material production step and maintaining the temperature at 400 ℃ to 600 ℃ for a predetermined time. Thereby, nuclei for generating crystals are formed. The time for maintenance is preferably 10 minutes or longer, as long as sufficient nucleation can be formed. The upper limit of the time is not particularly limited, and may be set to 6 hours or less.

The heat treatment step is a step of heating the glass material without cooling and maintaining the glass material at 800 ℃ or higher and 1000 ℃ or lower for a predetermined time. Thus, a lithium disilicate material having a main crystal phase of lithium disilicate can be obtained. The time for the maintenance is preferably 1 minute or more, and more preferably 3 minutes or more. The upper limit of the time is not particularly limited, and may be set to 3 hours or less.

In the nucleation step and the heat treatment step, the temperature needs to be maintained within a predetermined temperature range as described above, but the temperature does not necessarily need to be maintained at a constant temperature as long as the temperature is within the predetermined temperature range. That is, the temperature rise can be continued.

The heat treatment step may be provided with an intermediate step having a different temperature. That is, the glass material is heated without cooling after the nucleation step before being maintained at 800 ℃ or higher and 1000 ℃ or lower as described above, and is maintained at 600 ℃ or higher and 800 ℃ or lower for a predetermined time. Thus, crystals were produced, and an intermediate was obtained. The time for this is preferably 10 minutes or more. The upper limit of the time is not particularly limited, and may be set to 6 hours or less. The heating maintained at 800 ℃ or higher and 1000 ℃ or lower as described above may be performed without cooling after the intermediate process.

The cooling step is a step of cooling the lithium disilicate material obtained in the heat treatment step to room temperature. Thus, the lithium disilicate material becomes a block for dental restorations, and can be supplied to a machining process.

The machining step is a step of machining the obtained block for a dental restoration into the shape of the dental restoration. The machining method is not particularly limited, and cutting, grinding and the like can be exemplified. Thereby, a dental prosthesis can be obtained.

The processing can be performed with excellent productivity. That is, heretofore, a dental restoration block having lithium disilicate as a main crystal phase has been difficult to cut efficiently due to insufficient machinability. Therefore, it is necessary to process a block of a material that is easy to process and does not contain lithium disilicate as a main crystal phase (for example, a block containing lithium metasilicate as a main crystal phase), convert the block into lithium disilicate by further heat treatment, and then perform a step of improving strength.

In contrast, according to this embodiment, even a bulk body having lithium disilicate as a main crystal phase can be cut and ground under conditions equal to or higher than those of machining using a material that is easy to machine. Further, since heat treatment is not required after machining, the dental prosthesis can be produced while maintaining the accuracy of machining without changing the shape.

Examples

In examples 1 to 10 and comparative examples 1 to 4, a block body having lithium disilicate as a main crystal phase was prepared by a manufacturing method based on the melt molding method described above while changing the contained components, and a dental prosthesis was manufactured by cutting to evaluate machinability.

The blocks in each example were produced as follows.

In each example, the materials shown in table 1 were mixed in the proportions and melted at 1300 ℃ for 3 hours to obtain molten glass (melting step). Next, the obtained molten glass is poured into a mold and cooled to room temperature to prepare a glass material (glass material preparation step). Then, the obtained glass material was heated and maintained at 650 ℃ for 60 minutes (nucleation step). This was further heated and maintained at 850 ℃ for 10 minutes to prepare a lithium disilicate raw material having a main crystal phase of lithium disilicate (heat treatment step). Then, the mixture was gradually cooled to room temperature (cooling step) to obtain a block.

The resulting block was a rectangular parallelepiped with a width W of 14mm, a depth D of 12mm and a height H of 18 mm.

The contents of the components are shown in mass% in table 1. Table 1 shows the ratio (%) of the crystals having a length of 0.5 μm or more obtained by the above-described method, and the machinability. The blank column in the item of the components in table 1 indicates 0 mass%.

The main crystal phase is set as: among the observed crystal phases, the crystal phase having the highest crystal precipitation ratio was measured by an X-ray diffraction apparatus (Empyrean (registered trademark); manufactured by SPECTRIS K.K.) and quantitatively analyzed by the Rittwoeld method. The bulk in both the present example and the comparative example was lithium disilicate as the main crystal phase.

The "ratio" is the ratio of the above-mentioned crystals having a length of 0.5 μm or more, and is the area ratio (%) obtained by the above-mentioned method.

As for the "machinability", two types of conventional machining blocks were prepared as reference 1 and reference 2 for evaluation. Respectively, as described below.

(reference 1) is a bulk body having lithium metasilicate as a main crystal phase and containing SiO in a proportion of 72.3 mass%₂And 15.0 mass% of Li₂O, Al in a proportion of 1.6 mass%₂O₃。

(reference 2) is a block containing a crystal phase of lithium metasilicate and a crystal phase of lithium disilicate at substantially the same ratio, and SiO is contained at a ratio of 56.3 mass%₂And Li in a proportion of 14.7 mass%₂O, Al in a proportion of 2.1 mass%₂O₃。

In the examples and comparative examples, the block bodies of reference 1 and reference 2 were evaluated for machining time, tool wear, and chipping degree in the machining by a ceramic machining machine (CEREC (registered trademark) MC XL; manufactured by Sirona digital Systems Co., Ltd.). A block in which any one of the machining time, the wear condition of the tool, and the chipping is good as compared with the blocks of reference 1 and reference 2 is set to "good", a block in which any one of the machining time, the wear condition of the tool, and the chipping is particularly good is set to "good", a block in which any one of the machining time, the wear condition of the tool, and the chipping is equal to "equal", and a block in which any one of the machining time, the wear condition of the tool, and the chipping is lower than equal to the block of reference 1 and reference 2 is represented as "bad".

As can be seen from table 1, the dental restoration block according to the example had good machinability, although the main crystal phase was lithium disilicate. In both examples and comparative examples, the block had the required strength. The voids and the particulate matter also satisfy the above-described preferable conditions.

Description of the symbols

10 Block for dental restoration