阅读说明：本技术 牙科修复体用块体的制造方法、牙科修复体的制造方法 (Method for manufacturing block for dental restoration, and method for manufacturing dental restoration ) 是由 加藤克人 于 2019-12-20 设计创作，主要内容包括：本发明包括将低于偏硅酸锂晶体的生成温度的玻璃坯料暴露于焦硅酸锂晶体的生成温度以上且低于熔点的气氛中进行加热以使主要晶相变为焦硅酸锂的工序。(The method comprises a step of exposing a glass material having a temperature lower than the formation temperature of lithium metasilicate crystals to an atmosphere having a temperature not lower than the formation temperature of lithium disilicate crystals and lower than the melting point of lithium disilicate crystals to heat the glass material so that the main crystal phase of the glass material is changed to lithium disilicate.)

1. A method for manufacturing a block for a dental restoration, which is a method for manufacturing a block before machining for making a dental restoration is performed, wherein,

comprises a step of exposing a glass material having a temperature lower than the formation temperature of lithium metasilicate crystals to an atmosphere having a temperature not lower than the formation temperature of the lithium disilicate crystals and lower than the melting point thereof to heat the glass material so that the main crystal phase of the glass material is changed to lithium disilicate.

2. The method for manufacturing a block for a dental restoration according to claim 1, wherein the step of heating is followed by a step of slow cooling.

3. The method for manufacturing a block for a dental restoration according to claim 1 or 2, wherein the temperature of the atmosphere is 750 ℃ or more and 900 ℃ or less.

4. The method for manufacturing a block for a dental restoration according to any one of claims 1 to 3, wherein the exposure to the atmosphere is placing the glass blank in a heating device.

5. The method for manufacturing a block for a dental restoration according to any one of claims 1 to 4, wherein the block for a dental restoration contains 60 mass% or more and 80 mass% or less of SiO₂10 to 20 mass% of Li₂O and 3 to 15 mass% of Al₂O₃。

6. A method for manufacturing a dental restoration, comprising the steps of manufacturing a block for a dental restoration by the manufacturing method according to any one of claims 1 to 5, and machining the block for a dental restoration.

7. The method for manufacturing a dental prosthesis according to claim 6, wherein said machining is a cutting.

Technical Field

The present invention relates to a method for manufacturing a block for a dental restoration and a method for manufacturing 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 method for manufacturing a dental restoration block with good machinability.

Means for solving the problems

One embodiment of the present invention is a method for manufacturing a block for a dental restoration before machining for manufacturing a dental restoration, including a step of exposing a glass blank having a temperature lower than a generation temperature of lithium metasilicate crystals to an atmosphere having a temperature equal to or higher than the generation temperature of the lithium disilicate crystals and lower than a melting point of the lithium disilicate crystals and heating the glass blank to convert a main crystal phase into lithium disilicate.

The step of heating may be followed by a step of slow cooling.

In the step of heating, the temperature of the atmosphere may be 750 ℃ to 900 ℃.

The exposure to the atmosphere may be by placing the glass blank in a heating device.

The dental restoration block may contain 60 mass% to 80 mass% of SiO₂10 to 20 mass% of Li₂O and 3 to 15 mass% of Al₂O₃。

Another aspect of the present invention is a method for manufacturing a dental prosthesis, including a step of manufacturing a block for a dental prosthesis by the above-described manufacturing method and machining the block for a dental prosthesis. The machining may be a cutting process.

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.

First, a dental restoration block manufactured by one embodiment of a method for manufacturing a dental restoration block will be described. The dental restoration block (hereinafter, sometimes referred to as "block") is a prism, a cylinder, or a plate (disk), 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.

In order to produce the block of the present embodiment, the material may contain the following components.

60 to 80 mass% SiO₂、

10 to 20 mass% of Li₂O、

3 to 15 mass% of Al₂O₃。

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.

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 material of the component for adjusting the melting temperature (melting temperature adjusting 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

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 that functions as a material for forming nuclei (nucleation material) include oxides of Zr, P, and Ti (ZrO)₂、P₂O₅、TiO₂). In this case, it is preferable to contain a compound selected from ZrO₂、P₂O₅And TiO₂And the total amount thereof is 0 mass% or more and 10 mass% or less.

The material for the block may also contain known coloring materials from the viewpoint of enhancing the aesthetic quality. This may be exemplified by a selection from V₂O₅、CeO₂、Er₂O₃、MnO、Fe₂O₃、Tb₄O₇At least one of (1).

Next, a mode of a method for producing a dental prosthesis will be described. This includes the manner of the 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 heat treatment 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 a temperature lower than the production temperature of lithium metasilicate crystals, preferably 400 ℃ or lower, more preferably 100 ℃ or lower, and further preferably 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 heat treatment step is a step of heating the glass material obtained in the glass material production step at a temperature in a range of not lower than the production temperature of lithium disilicate crystals and lower than the melting point, more preferably not lower than 750 ℃ and not higher than 900 ℃.

In this step, rapid heating is preferably performed, and therefore, the glass material cooled to a temperature lower than the production temperature of lithium metasilicate crystals, preferably 400 ℃ or lower, more preferably 100 ℃ or lower, and still more preferably room temperature in the glass material production step is heated by, for example, being placed in a heating device such as a furnace, in order to be exposed to an atmosphere in which the production temperature of lithium disilicate crystals is not lower than the melting point, and more preferably 750 ℃ or higher and 900 ℃ or lower. With respect to the heating time, until the predominant crystalline phases within the glass blank become lithium disilicate. Therefore, the time period may be set to 20 minutes or more, although not limited thereto. The upper limit of the time is not particularly limited, and may be set to 6 hours or less.

When the temperature is lower than the temperature at which lithium disilicate crystals are formed, lithium disilicate raw materials having lithium disilicate as a main crystal phase may not be obtained. On the other hand, when the temperature is set to a temperature not lower than the melting point of the lithium disilicate crystal, softening may occur.

Then, after the rapid heating, the heating was stopped and the mixture was cooled to room temperature, thereby obtaining a dental restoration block mainly having a crystal phase of lithium disilicate. Preferably, the cooling is performed in a furnace, and the natural cooling in the furnace is performed by slow cooling based on a slow temperature change.

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 the heat treatment step, as described above, rapid heating is required within a predetermined temperature range, but the temperature may vary as long as the temperature is within the predetermined temperature range, and the temperature does not necessarily need to be maintained constant.

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 prepare a readily processable block not having lithium disilicate as a main crystal phase (for example, a block having lithium metasilicate as a main crystal phase), machine the block, perform heat treatment after the processing to convert the main crystal phase into lithium disilicate, and then perform a step of improving strength.

In contrast, according to this embodiment, even a bulk body whose main crystal phase is lithium disilicate can be cut and ground under conditions equal to or more than those for machining a readily machinable bulk body whose main crystal phase is lithium metasilicate. 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.

The block manufactured by the manufacturing method of the present embodiment has the following structure. In FIG. 2 it is shown that the symbol A in FIG. 1 will be followed₁Cut surface of the block 10 cut by the dotted line shownA part of which is enlarged. 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.

As noted above, the predominant crystalline phase of the bulk 10 is lithium disilicate.

In addition, regarding the bulk 10, it is preferable that the ratio of the total area of crystals having a length of 0.5 μm or more among the crystals appearing in the visual field range shown in fig. 2 to the area of the visual field shown in fig. 2 (5 μm × 5 μm) is 21% or less, but it is not necessary to be 21% or less, and it is sufficient that the ratio can be reduced by the production method of the present embodiment as compared with the conventional production method. The above ratio is preferably 10% or less, and more preferably 1% or less.

It should be noted that crystals having a length of 0.5 μm or more to be extracted among the developed crystals can be limited to only crystals formed of lithium disilicate.

Thus, even if a block having a main crystal phase of lithium disilicate is produced, cutting and grinding can be performed under conditions equal to or higher than those of conventional blocks that are easy to machine (for example, blocks having a main crystal phase of lithium metasilicate). Further, according to this, for example, since the post-processing heat treatment required for the bulk body whose main crystal phase is lithium metasilicate is not required, the dental prosthesis can be produced in a state where the accuracy of the 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, at the center A₁End part A₂End part A₃The section of (A) is directed to the center B indicated by the dotted line₁With respect to the B₁Adjacent in the width W direction and from the end with respect to the full width WTwo ends B of 10% position₂And 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 portions₃Scanning electron microscope images were obtained in the fields of view of 5 μm × 5 μm 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 × 5 μm) and expressed as a percentage, the ratio is obtained for each image separately. Thus, a total of 15 individual ratios were obtained.

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

Here, it is preferable that no void is observed in the block for a dental restoration. 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 observed in a microscopic photograph at a magnification of 200 at 15 sites where the above ratio is measured.

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 with melting of a material as described above, rather than by 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 although the strength is such that the heat treatment after machining is unnecessary, the machining can be performed without causing any defects under machining conditions that are as high as or higher than those of conventional dental restoration blocks made of cutting ceramics.

Examples

In examples 1 to 7 and comparative examples 1 to 6, the components contained and the heat treatment temperature were changed, a block was prepared by the above-described manufacturing method by the melt molding method, a dental restoration was manufactured by cutting, and the machinability at this time was evaluated.

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

The blocks of examples 1 to 7, comparative examples 5 and comparative example 6 were prepared by performing a rapid heating heat treatment 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 glass material was put into a furnace preheated to the heat treatment temperature shown in table 1, and maintained at the heat treatment temperature for 30 minutes (heat treatment by rapid heating). Then, the mixture was gradually cooled to room temperature (cooling step) to obtain a block.

On the other hand, the blocks of comparative examples 1 to 4 were produced by performing a conventional heat treatment 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, and then heated to 850 ℃ for 10 minutes (heat treatment by conventional heating). Then, the mixture was gradually cooled to room temperature (cooling step) to obtain a block.

The contents of the components are shown in mass% in table 1. As is clear from table 1, the components other than the coloring material were the same in example 1 and comparative example 1, example 2 and comparative example 2, example 3 and comparative example 3, and example 4 and comparative example 4.

Table 1 shows the type of heat treatment, the heat treatment temperature in the case of rapid heating, the type of main crystal phase of the obtained bulk ("LDS" is lithium disilicate and "LS" is lithium metasilicate), the ratio (%) of crystals having a length of 0.5 μm or more obtained by the above-described method, and 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 "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.

Regarding "machinability", two types of conventional machining blocks were prepared as reference 1 and reference 2. 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 was good as compared with the blocks of reference 1 and reference 2 is represented as "good", and a block in which any one of the machining time, the wear condition of the tool, and the chipping was lower than the same as 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 addition, the "ratio" in the examples is suppressed to be lower than that in the comparative examples.

It can also be known that: in example 1 and comparative example 1, example 2 and comparative example 2, example 3 and comparative example 3, and example 4 and comparative example 4, the machinability and the ratio are greatly different from each other because the manufacturing process is different, although the components other than the coloring material are the same. In comparative example 5, lithium disilicate was not obtained as a main crystal phase, and in comparative example 6, softening occurred.

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