JP6524500B2 - Alloys and dental prostheses for baking dental porcelain excellent in oxidation resistance - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an alloy for dental porcelain baking and a dental prosthesis excellent in oxidation resistance.

  Co-Cr-based alloys such as Co-Cr-W alloys and Co-Cr-W-Mo alloys are known as dental alloys that constitute dental prostheses such as crowns, inlays, and bridges. In order to improve the aesthetics of the dental prosthesis, a dental porcelain is formed by applying and firing a paste-like porcelain raw material powder on the surface of the frame made of the above-mentioned alloy. As a result, a dental prosthesis having a color close to that of natural teeth can be obtained. The baking (also referred to as baking) of the dental porcelain is usually performed at a high temperature of about 900 to 1000 ° C. in the atmosphere. By repeating this process several times by changing the type of porcelain, a dental prosthesis having a color close to that of the natural tooth is completed.

  Since the thermal expansion coefficient of a gold alloy, which has long been used as a dental alloy, is close to the thermal expansion coefficient of the above-mentioned porcelain, the porcelain is well formed even after the above-mentioned firing. Since the said Co-Cr base alloy also has a thermal expansion coefficient substantially equivalent to the said gold alloy, it is possible to closely approach the thermal expansion coefficient of the said porcelain.

  For example, in Patent Document 1, 0 to 0.4 carbon by weight, 0.1 to 5.0 silicon by weight, as an alloy in which the difference with the thermal expansion coefficient of the ceramic formed on the metal surface is reduced. 0.01-8.0 manganese, 25-35 chromium, 1.0-8.0 molybdenum, 0.1-5.0 niobium, 0-0.3 nickel, 0-1.0 An alloy is shown containing iron, the balance cobalt, and impurities resulting from manufacturing. In addition, Patent Document 2 supports dental ceramics without containing an element at risk of carcinogenicity such as nickel, an element whose toxicity data is unknown, and an element which is easily oxidized by melting in the atmosphere such as titanium. A dental alloy material is shown which has sufficient elongation, a suitable hardness and a coefficient of thermal expansion and is also applicable to the fabrication of restorations by laser sintering. As the dental alloy material, chromium (Cr): 22.7 to 26.7% by weight, molybdenum (Mo): 5.5 to 7.5% by weight, tungsten (W): 4.0 to 6.0 weight %, Iron (Fe): 0.4 to 0.6% by weight, silicon (Si): 1.0 to 2.0% by weight, manganese (Mn): 0.2 to 0.4% by weight, carbon (C ): A dental alloy material is shown consisting of 0.08 to 0.12% by weight, the balance cobalt (Co) and traces of unavoidable impurities. Further, Patent Document 3 includes Cr: 25 to 32% by mass, W: 8 to 12% by mass, an element of Group 4a of the periodic table and / or an element of Group 5a: 0.05 to 0.4% by mass. A dental casting alloy with improved fracture strength and hardness, the remainder being Co and unavoidable impurities, is shown. These Co-Cr based alloys are attracting attention as substitutes for gold alloys due to the recent increase in gold price and the like.

  However, in the case of the above-mentioned Co-Cr base alloy, when baking at the above-mentioned high temperature, oxidation of the metal exposed part which is not covered with dental porcelain, the fitting part in the frame with dental abutment etc. advances, Oxide layer is formed. Therefore, post-processing is required to remove the oxide layer by polishing or blasting. However, when this post-processing is performed, the shape of the oxide layer removed portion may change. When the shape changes, shape mismatch, that is, a decrease in shape compatibility may occur at a portion where high dimensional accuracy is required, such as a combination surface with the abutment. On the other hand, when the above-mentioned post-processing is not performed, there is a concern about a defect due to the dropping of the oxide layer or the like. In addition, since the oxide layer is black, it is required that the color tone be thin even after the baking and be closer to a metallic color from the viewpoint of improving the aesthetics.

  Therefore, the Co-Cr-based alloy is required to suppress the formation of the oxide layer by the baking as much as possible, that is, to have excellent oxidation resistance. In addition to the tensile properties such as strength required for dental prostheses, the Co-Cr base alloy is also required to have the hot forgeability required in the disc manufacturing process.

JP-A-61-501784 JP, 2010-275218, A U.S. Patent Application Publication No. 2005/0232806

  The present invention has been made focusing on the above circumstances, and the object thereof is a Co-Cr base alloy for baking a dental porcelain, which has tensile properties such as good strength and hot forgeability. It is an object of the present invention to provide a dental porcelain baking alloy which is capable of suppressing oxidation due to porcelain firing as much as possible, that is, excellent in oxidation resistance. Furthermore, another object of the present invention is to provide a dental prosthesis obtained by using the dental porcelain baking alloy.

  The alloy for baking dental porcelain according to the present invention, which has solved the above problems, contains 20% or more and 40% or less of Cr (% means mass%. The same applies to chemical components hereinafter) and the Group 6 element of the periodic table. It contains 5% to 20% in total, 0% to 3% in total of Group 14 elements in the periodic table, B (boron) in 0.005% to 0.110%, and the balance is Co And the inevitable impurities.

  In a preferred embodiment of the present invention, the dental porcelain baking alloy contains, as the group 6 element, one or more elements selected from the group consisting of W and Mo.

  In a preferred embodiment of the present invention, the dental porcelain baking alloy contains Si: 0.5% or more and less than 3% and C (carbon): 0.01% or more and 0.4% as the group 14 element. It contains one or more elements selected from the group consisting of:

  In a preferred embodiment of the present invention, the dental porcelain baking alloy has metallic gloss in the color tone of the alloy surface after heat treatment at 1000 ° C. for 15 minutes in an air atmosphere.

  In a preferred embodiment of the present invention, the dental porcelain baking alloy has a thickness of less than 850 nm of an oxide layer formed on the alloy surface after heat treatment at 1000 ° C. for 15 minutes in an air atmosphere. .

  The present invention also includes dental prostheses obtained using the above-mentioned dental porcelain baking alloy.

  According to the present invention, even after the dental porcelain is baked at high temperature, oxidation is suppressed in the exposed metal portion, so that the color tone has metallic luster, and the post-processing is performed to remove the oxide layer by polishing or blasting etc. It is possible to omit or simplify the Furthermore, the dental porcelain baking alloy of the present invention has the strength necessary for a dental prosthesis, and can perform hot forging well in the manufacturing process of the dental prosthesis.

FIG. 1 is a SEM (Scanning Electron Microscope) microscopic photograph of the surface of each sample in the example. FIG. 2 shows the result of EPMA (Electron Probe MicroAnalyzer) element mapping of the compound recognized in sample No. 8. FIG. 3 is a view showing an example of XPS (X-ray Photoelectron Spectroscopy) measurement in the embodiment. FIG. 4 is a view showing the relationship between the B content and the thickness of the oxide layer formed on the alloy surface after heat treatment at 1000 ° C. for 15 minutes in the air atmosphere. FIG. 5A is a view showing the relationship between the B content and the tensile strength and the 0.2% proof stress. FIG. 5B is a view showing the relationship between the B content and the elongation.

  In order to solve the above-mentioned problems, the inventors of the present invention have conducted intensive studies under the concept of using a Co-Cr-based alloy that is not easily oxidized during high-temperature firing in the atmosphere. As a result, it has been found that particularly B may be contained in the range of 0.005% or more and 0.110% or less as an alloy element contained in the Co—Cr base alloy. Hereinafter, the dental porcelain baking alloy of the present invention will be described.

  In the dental porcelain baking alloy of the present invention, Cr: 20% or more and 40% or less, 5% or more and 6% or less of the group 6 elements in the periodic table, and 0 or less in total of the group 14 elements in the periodic table More than% and 3% or less, B is contained in 0.005% or more and 0.110% or less, and the balance is made of Co and unavoidable impurities. The dental porcelain baking alloy of the present invention is characterized in that it contains B in a specified amount as described above, on the premise that it contains Cr, which will be described later, and the elements of Group 6 and Group 14 of the periodic table. . Hereinafter, it demonstrates from the reason which prescribed | regulated B content first.

[B: 0.005% or more and 0.110% or less]
By containing B as an alloying element, the formation of the oxide layer is sufficiently suppressed, and the color tone becomes thinner and approaches metal color. Such an effect of improving the oxidation resistance of B is considered to be due to the formation of a concentrated region of B in the oxide layer, which suppresses the growth of the oxide layer, as described in the examples below. In the present invention, in order to exert the effect of B, the B content is made 0.005% or more. The B content is preferably 0.02% or more, more preferably 0.03% or more, still more preferably 0.05% or more, and still more preferably 0.075% or more. On the other hand, when the B content is excessive, borides are formed, the tensile strength is reduced and the elongation is also reduced, and furthermore, cracking tends to occur during hot forging. In addition, when the B content is excessive, borides are formed, and the amount of B present in the solid solution state in the alloy decreases, an oxide layer is easily formed. Therefore, the B content is 0.110% or less. The B content is preferably 0.10% or less.

  In addition, there exists an application example to a brazing material as a technique which added about 4 mass% B to Co-Cr base alloy. However, this adds B for the purpose of lowering the melting point of the Co-Cr base alloy, and the present invention is a technology which is different from the present invention in all of the problem, the application and the B content.

  FIG. 1 is a SEM micrograph of each of the Co-Cr based alloys manufactured in Examples described later. No. attached to each photo. Is the sample No. of the example described later. It is. No. 1 in FIG. The compound (precipitate) is shown by the arrow in the photograph of 8. Furthermore, this sample No. EPMA elemental mapping of the compound recognized in 8 was performed. The mapping was performed at an accelerating voltage of 15 kV using an X-ray microanalyzer "JXA-8430F" manufactured by JEOL. The results are shown in FIG. The field of view of FIG. 2 is different from the field of view of the SEM micrograph of FIG. From this FIG. 2, it can be seen that the above compound is mainly a compound of Cr, W and B.

  Sample No. When the B content is excessive as shown in FIG. 8, coarse compounds are precipitated as shown in FIG. 1 and the photograph of FIG. 2 above, and it is considered that the tensile properties and the hot forgeability are lowered by this compound.

  The Co-Cr base alloy of the present invention is characterized in that it contains B in the above amount, but for securing the strength as a dental prosthesis, etc., Cr, the element of group 6 and the element 14 of the periodic table Each must be included in the specified amount.

[Cr: 20% or more and 40% or less]
Cr is an element necessary for solid solution strengthening and securing corrosion resistance, and is contained by 20% or more. The Cr content is preferably 22.5% or more, more preferably 25% or more. On the other hand, since an intermetallic compound is easily formed even if the Cr content is too large and the strength may be reduced, the Cr content is 40% or less. The Cr content is preferably 35% or less, more preferably 32.5% or less.

[Group 6 elements of periodic table: 5% or more and 20% or less in total]
The Group 6 element in the periodic table also contributes to solid solution strengthening, as in the case of Cr described above. The Group 6 element is also an element that contributes to the adjustment of the thermal expansion coefficient. In order to exert these effects, the Group 6 element is contained in a total amount of 5% or more. The content refers to a single amount when one element is contained as a group 6 element, and refers to the total amount of the two or more elements when two or more elements are contained as a group 6 element. The total content of the group 6 elements is preferably 6% or more in total, more preferably 7% or more in total. On the other hand, if the above-mentioned Group 6 element is contained in excess, intermetallic compounds are easily formed. Therefore, the content of the group 6 element is 20% or less in total, preferably 15% or less in total, and more preferably 10% or less in total.

  The Group 6 element is preferably one or more elements selected from the group consisting of Mo and W. By appropriately adjusting the ratio of the content of Cr and W, an alloy exhibiting a thermal expansion coefficient close to that of a commercially available porcelain can be obtained.

[Group 14 elements of periodic table: more than 0% and up to 3% in total]
Since the Group 14 element is an element susceptible to oxidation, the inclusion of the Group 14 element suppresses the oxidation of the Co-Cr-based alloy, particularly Cr, and enhances the oxidation resistance of the Co-Cr-based alloy. be able to. Furthermore, it is also an element necessary for good casting because it contributes to the improvement of the flowability of the molten metal at the time of alloy melting. From these points of view, the group 14 elements of the periodic table are contained in total of more than 0% and 3% or less. The content refers to a single amount when one element is included as a Group 14 element, and refers to the total amount of the two or more elements when two or more elements are included as a Group 14 element. The Group 14 element is preferably one or more elements selected from the group consisting of Si and C. In particular, Si is preferred. The preferable content of the above-mentioned Group 14 element depends on the kind of the element. Hereinafter, preferable contents of Si and C will be described.

  When the above Si is contained, the Si content is preferably 0.5% or more and less than 3%. The lower limit of the Si content is more preferably 1.0% or more, still more preferably 1.25% or more. On the other hand, when the Si content is excessive, it is difficult to ensure good hot forgeability, so the Si content is preferably less than 3%, more preferably 2% or less, and still more preferably 1.8. % Or less.

  When C is contained, the C content is preferably 0.01% or more and 0.4% or less because of the same upper and lower limit reasons as in the case of Si. The lower limit of the C content is more preferably 0.015% or more, and still more preferably 0.020% or more. The upper limit of the C content is more preferably 0.35% or less, and still more preferably 0.30% or less. In the case where W is contained as the above-mentioned Group 6 element and C is used as the above-mentioned Group 14 element, it is preferable to reduce the above-mentioned C content in the above-mentioned range. This is because the formation of hard tungsten carbide tends to lower the hot forgeability and the like.

The dental alloy of the present invention contains the above-described elements, with the balance being Co and unavoidable impurities. As inevitable impurities, including Miuru Mn, Ga, Nb, N, and Fe and the like.

(Dental prosthesis)
In the present invention, a dental prosthesis obtained by using the above-described dental porcelain baking alloy, specifically, an alloy frame before the porcelain baking and a surface obtained by baking the dental porcelain on the surface of the alloy frame are obtained. Ceramic coverings are included. Examples of the dental prosthesis include crowns, inlays, onlays, copings, dentures and the like.

(Method for manufacturing dental porcelain baking alloy and dental prosthesis)
The method for producing the dental porcelain baking alloy of the present invention is not particularly limited, and the alloy may be melted so as to satisfy the above-mentioned component composition and may be cast by a generally practiced method.

  Moreover, as a dental prosthesis, the following method may be mentioned to manufacture the above-mentioned alloy frame. First of all, precision casting is mentioned as a method conventionally used. In the method, a molten alloy is poured into a mold and cast to manufacture.

  Moreover, the following manufacturing methods are also mentioned in recent years. After an ingot is manufactured by casting, it is hot forged to eliminate casting defects and improve strength, and a disc is manufactured. Using the disk, it is a method of manufacturing an alloy frame of a complicated shape using milling, additive manufacturing, etc., utilizing a CAD / CAM system. The hot forging may be performed, for example, under the conditions of a temperature of 1000 to 1250 ° C. and a pressing pressure of 100 to 10000 t. In the embodiment to be described later, since the sample size is small, an air hammer with a maximum press pressure of 125 kgf is used.

  After the precision casting or after the ingot production, as shown in the examples to be described later, the homogeneous heat treatment may be performed as necessary.

  Porcelain baking is performed using the above-mentioned alloy frame, and the conditions may be those generally used. The said porcelain can also use a commercially available thing. Firing conditions depend on the porcelain to be used, but for example, atmospheric atmosphere, temperature: 940 to 960 ° C., time: 1 to 2 minutes can be mentioned. In the present invention, in order to evaluate the thickness and color tone of the oxide layer after heat treatment, heat treatment at 1000 ° C. for 15 minutes is performed as firing conditions more severe than the above-described firing conditions.

  In the case of the alloy of the present invention, the above-mentioned baking is simulated, and oxidation is suppressed even when heat treatment is performed at 1000 ° C. for 15 minutes in the air atmosphere. The color tone of the alloy surface before baking exhibits metallic luster. In the alloy of the present invention, since the oxidation by baking is suppressed as described above, the color tone of the alloy surface does not change to gray black, and the metallic gloss is maintained. In the present invention, the color tone before and after heat treatment is thus judged by the presence or absence of metallic gloss, and the hue is not particularly limited. The hue varies depending on the type of alloying element contained in the alloy, and may exhibit a green color or a pink color as in the following examples.

  Further, the oxidation of the alloy of the present invention is suppressed, so that the thickness of the oxide layer formed on the alloy surface after the heat treatment is suppressed to less than 850 nm. The thickness of the oxide layer is preferably 800 nm or less, more preferably 700 nm or less, still more preferably 650 nm or less, still more preferably 600 nm or less, particularly preferably 500 nm or less.

  EXAMPLES Hereinafter, the present invention will be more specifically described by way of examples. However, the present invention is of course not limited by the following examples, and appropriate modifications may be made as long as the present invention can be applied to the purpose. Of course, implementation is also possible, and all of them are included in the technical scope of the present invention.

  Eight Co-Cr based alloys having the chemical composition shown in Table 1 were produced. In addition, No. 1 of Table 1 1, 7 and 8 are comparative examples in which the B content is out of the specified range. Specifically, an ingot having a diameter of 30 mm and 1 kg satisfying the chemical composition shown in Table 1 was melted by high frequency induction melting. It was then subjected to homogeneous heat treatment at 1200 ° C. for 6 hours in vacuum. Thereafter, the sample was heated to 1150 ° C., and hot forged to a 15 mm square using an air hammer (maximum press pressure 125 kgf) to obtain a test material.

  The hot forgeability is evaluated as good (OK) when the hot forging can be favorably performed without the occurrence of cracks, and the case where a crack occurs during the hot forging is inferior to the hot forgeability It was evaluated as (NG). The results are shown in Table 2 below.

  Furthermore, while using the said test material, while evaluating the tension test in the following way, the heat processing which simulated porcelain firing was performed in the following way, and oxidation resistance and color tone were evaluated.

(Tensile test)
Using the above-mentioned test material, a test piece having a length between marks of 10.5 mm and a cross-sectional area of a mark portion of 2 mm × 1 mm was prepared and subjected to a tensile test to measure 0.2% proof stress, tensile strength and elongation. Each sample No. At least three of the above test pieces were prepared and measured, and the average value was determined.

(Evaluation of oxide thickness and color after heat treatment)
The above-described sample material was subjected to heat treatment at 1000 ° C. for 15 minutes in the air atmosphere to simulate porcelain firing. Then, the thickness of the oxide layer formed on the surface of the test material after the atmospheric heat treatment was measured by XPS. In detail, it measured using KRATOS AXIS Ultra DLD and using the monochromatized Al K alpha ray. The analysis range is 300 μm × 700 μm, and XPS measurement is performed while sputtering with argon ions, and the thickness of the oxide layer is determined in terms of SiO ₂ from the obtained element profile.

  In detail, the thickness of the oxide layer was determined by the following method. The method of obtaining the thickness of the oxide layer from the above-mentioned element profile will be described using the XPS result illustrated in FIG. In the elemental concentration distribution measurement by XPS in FIG. 3 described above, the depth from the surface to the intersection point of the broken line (Co2pM) indicating the Co concentration and the dotted line (O1s) indicating the oxygen concentration is shown in FIG. It was defined as the thickness of The case where the thickness of the oxide layer was less than 850 nm was accepted, and the case where the thickness of the oxide layer was 850 nm or more was rejected.

  In addition, the surface of the test material after the atmospheric heat treatment was visually observed to evaluate the color tone. In this example, “metallic-lustrous green color” was accepted, and the others were rejected.

  The results are shown in Table 2.

  The figure which arranged the relationship between B content and the thickness of an oxide layer using the result of said Table 1 and Table 2 is shown in FIG.

  Moreover, the figure which arranged the relationship between B content, 0.2% proof stress, and tensile strength using the result of said Table 1 and Table 2 is shown to FIG. 5A, and the figure which arranged the relationship between B content and elongation Is shown in FIG. 5B.

  The following can be understood from FIGS. First, from FIG. 4, when the B content is less than 0.005%, the oxide layer after the atmospheric heat treatment becomes thicker, and when the B content exceeds 0.110%, the thickness of the oxide layer also increases. I understand. On the other hand, when the B content is in the specified range, that is, in the range of 0.005% to 0.110%, it can be seen that the thickness of the oxide layer is suppressed to less than 850 nm.

  From FIG. 4, in order to make the oxide layer thinner, for example, to have a thickness of 650 nm or less, it is preferable that the lower limit of the B content be 0.01% or more, and the upper limit be 0.10% or less. Recognize. Further, from FIG. 4, it is preferable to set the lower limit of B content to 0.02% or more, for example, to 580 nm or less, for example, to set the lower limit of B content to 0.03% or more, to be 550 nm or less. Is found to be more preferable.

  Note that FIG. 3 is an example in which the B amount is within the specified range, and in the oxide layer of FIG. 3, a slight unevenness is observed in the line indicating the B amount. This seems to mean that a B-enriched region is formed in the oxide layer. The reason why the thickness of the oxide layer is reduced by containing a specified amount of B is considered that B is combined with the oxide to form the B-enriched region, thereby suppressing the growth of the oxide.

  Next, FIG. 5A shows that when the B content exceeds 0.110%, the tensile strength decreases, and when the B content is about 0.30%, the tensile strength decreases significantly. It can be seen from FIG. 5A that, in the example of the present invention in which the B content is 0.110% or less, a tensile strength of 1200 MPa or more, in particular, a tensile strength of 1300 MPa or more can be secured. Moreover, FIG. 5A shows that 0.2% proof stress is substantially constant irrespective of B content.

  It can be seen from FIG. 5B that when the B content exceeds 0.110%, the elongation sharply decreases. When the B content is about 0.30%, the elongation is a few% and is very small. From FIG. 5B, in the example of the present invention in which the B content is 0.110% or less, the elongation is 30% or more, and when the B content is 0.10% or less, the elongation is 40% or more, particularly 45% or more We see that we can achieve it.

  As shown in Table 2, when the B content exceeds 0.110%, cracking was also observed during hot forging. On the other hand, when the B content was 0.110% or less, hot forging could be performed well.

  In addition, as shown in Table 2, the No. 1 in which the B content is insufficient. In the case of No. 1, the color tone of the alloy surface loses metallic luster due to the above-mentioned atmospheric heat treatment and changed to gray black. On the other hand, No. 1 in which the B content is excessive. 7 and No. Even in the case of No. 8, the alloy surface after the atmospheric heat treatment had a color tone with a slight loss of metallic gloss. On the other hand, when the specified amount of B was contained, the metallic gloss was maintained even after the atmospheric heat treatment.

  From the above results, no. As described in 2 to 6, particularly when the specified amount of B is contained, the film exhibits good tensile properties and hot forgeability, and the color tone maintains metallic gloss even after atmospheric heat treatment at 1000 ° C. for 15 minutes, and It can be seen that the formation of an oxide layer after heat treatment can also be suppressed.

  In addition, according to this example, the thickness of the oxide layer formed after baking at a high temperature is remarkably reduced by containing a specified amount of B as an alloy element of a Co-Cr base alloy, especially with a Group 14 element. Also, it is understood that high aesthetics and high form compatibility with other parts can be obtained even if post processing such as removal of the oxide layer is simplified or omitted.

Claims (6)

22.5% or more and 35% or less of Cr (% means mass%. The same applies to chemical components hereinafter),
W is 5 % or more and 15% or less,
0.5% or more and less than 3% of Si,
0.01% or more and 0.4% or less of C,
B (boron) is included at 0.005% or more and 0.085% or less,
An oxidation-resistant dental porcelain baking alloy characterized in that the balance is made of Co and unavoidable impurities.   The dental porcelain baking alloy according to claim 1, wherein the color tone of the alloy surface after heat treatment at 1000 ° C for 15 minutes in an air atmosphere has metallic luster.   The dental porcelain baking alloy according to claim 1 or 2, wherein the thickness of the oxide layer formed on the alloy surface after heat treatment at 1000 ° C for 15 minutes in an air atmosphere is less than 850 nm.   The hot forging material for dental porcelain baking using the alloy in any one of Claims 1-3.   The hot forging material for dental porcelain baking according to claim 4, wherein the hot forging material has a tensile strength of 1200 MPa or more and an elongation of 30% or more.   The dental prosthesis using the dental porcelain baking alloy according to any one of claims 1 to 3 or the hot forging material for dental porcelain baking according to any one of claims 4 or 5.