JPH0833650A - Dental orthodontic bracket and its production - Google Patents

Abstract

PURPOSE:To provide a dental orthodontic bracket consisting of the sintered compact of partially stabilized zirconia having an excellent aesthetic characteristic, high strength, high toughness and excellent thermal stability. CONSTITUTION:This dental orthodontic bracket consists of the sintered compact of the partially stabilized zirconia which consists essentially of ZrO2, is stabilized with one or >=2 kinds of rare earth metal oxides selected from a group consisting of Gd2O3, Yb2O3, Ho2O3 and Dy2O3 or is stabilized by this rare earth metal oxides and/or La2O3 and Y2O3 and in which the ratio of the Y2O3 in the stabilizing agents is 30 to 70mol%. The raw material powder is molded and the molding is sintered at 1200 to 1450 deg.C. Then, the bracket shaped to have the good operability approximate to the operability of a metallic bracket is thus obtd. without any restriction in design. The deterioration in the strength does not arise even if the bracket is subjected to the surface treatment for the purpose of improving the adhesive. Coloration to the color tones approximate to the color tones of the natural teeth is possible and the aesthetic characteristic is excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dentition composed of a partially stabilized zirconia sintered body which is used in orthodontics and has excellent aesthetics, high strength and high toughness, and also excellent thermal stability. The present invention relates to a straightening bracket and a method for manufacturing the same.

[0002]

2. Description of the Related Art In orthodontic treatment, when a metal arch wire is inserted and fixed in a bracket bonded to a tooth, a large stress is applied to the bracket. For this reason,
Conventionally, a metal such as stainless steel having high strength and toughness has been used as a bracket material.

However, since the color of the metal bracket is different from that of natural teeth, it is conspicuous that the bracket is mounted, and there is a drawback that the aesthetics is poor.

As a means for solving this drawback, Japanese Patent Laid-Open No.
No. 4,25,847, JP-A-64-46451, and JP-A-64-52448 disclose orthodontic brackets made of transparent ceramics. These orthodontic brackets are transparent and have good aesthetics, but the strength and toughness of the material are insufficient, and there is a problem that the brackets are easily broken during treatment.

On the other hand, as a bracket with improved strength and good aesthetics, Japanese Patent Laid-Open No. 21857/1990 discloses Y ₂ O.
_An orthodontic bracket made of a partially stabilized zirconia sintered body using ₃ , CaO, MgO and CeO ₂ as stabilizers is disclosed. Further, JP-A-3-170148 and JP-A-4-280864 disclose an orthodontic bracket made of a partially stabilized zirconia sintered body stabilized with Y ₂ O ₃ or the like. Since this type of material lacks translucency, the aesthetics are enhanced by matching the color of the material to natural teeth.

Since these partially stabilized zirconia sintered bodies are excellent in mechanical strength and toughness to some extent, it is possible to produce a bracket having practical strength. However, in the conventional bracket made of a partially stabilized zirconia sintered body, it is necessary to design the product with priority on strength in consideration of product strength, and a bracket having good operability for a doctor has not been obtained. That is, in order to make a bracket having both high operability and strength, a bracket material having not only strength but also sufficiently high fracture toughness is required.

In addition, in the orthodontic bracket, it is necessary to secure a certain degree of thermal stability in view of its manufacturing process and use conditions. For example, partially stabilized zirconia has a small adhesive force with a general orthodontic adhesive and requires some surface treatment for improving the adhesive force. For example,
When the bracket is treated with the silane coupling agent, the bracket must be heat-treated at 120 ° C. or higher.
In addition, thermal stability that does not deteriorate even when subjected to a thermal cycle that is continued for two to three years in a moist oral cavity is required at a minimum.

By the way, the mechanical properties and thermal stability of the partially stabilized zirconia sintered body generally depend on the kind and the amount of addition of the stabilizer, but also greatly change depending on the crystal grain size of the sintered body. . The partially stabilized zirconia sintered body stabilized with Y ₂ O ₃ has the advantages that it has higher mechanical strength and can be sintered at a relatively low temperature, as compared with the one stabilized with CaO, MgO, CeO ₂ . From this fact, the conventional Y ₂
The partially stabilized zirconia sintered body stabilized with O ₃ is widely used in the industrial field. However, when the zirconia sintered body stabilized with Y ₂ O ₃ is held at 100 to 300 ° C. for a long time, the strength tends to deteriorate to some extent. This deterioration in strength is related to the fact that a part of the tetragonal phase contained in the sintered body undergoes a phase transition to a monoclinic phase at 100 to 300 ° C., and the sintering is caused by local expansion accompanying the phase transition. This is due to the generation of microcracks in the conglomerate.

On the other hand, the high strength and fracture toughness characteristic of the partially stabilized zirconia sintered body are due to the phase transition from the tetragonal phase to the monoclinic phase (stress-induced transformation strengthening mechanism) which occurs in the portion subjected to external stress. ) Is obtained. Therefore, if the amount of the stabilizer is reduced, the tetragonal phase becomes more unstable and stress-induced transformation easily occurs, so that the fracture toughness is improved. For example, in Japanese Patent Laid-Open No. 62-17070, Y
A partially stabilized zirconia sintered body is disclosed which has a fracture toughness value of 20 MPa√m or more when the amount of ₂ O ₃ is 2 mol% or less. However, the low Y ₂ O ₃ content is 1
A phase transition at 00 to 300 ° C. easily occurs, and a thermally stable sintered body cannot be obtained. That is, in a partially stabilized zirconia sintered body stabilized with Y ₂ O ₃ , it is difficult to achieve both high fracture toughness and thermal stability.

Further, it is known that the above-mentioned phase transition is accelerated in an environment with water or water vapor, and the strength is deteriorated even at a lower temperature (Uchida Otsurupo, Zirconia Ceramics 1).
0,157-174P (1989)).

Therefore, conventionally, in practice, Y
_{As the 2} O ₃ partially stabilized zirconia sintered body, Y ₂ O ₃
Many are practically used with the amount of 3 mol% or more and the fracture toughness value being about 6 MPa√m.

[0012]

As described above, an orthodontic bracket is required to have not only aesthetic properties but also high mechanical strength such as fracture toughness and excellent thermal stability. Conventionally, an orthodontic bracket that satisfies all such required characteristics has not been provided.

The present invention has been made in view of the above conventional circumstances, and has good aesthetics and higher mechanical strength, particularly fracture toughness, than that of a conventional partially stabilized zirconia sintered body. It is an object of the present invention to provide an orthodontic bracket that has few restrictions in terms of heat resistance and excellent thermal stability, and a method for manufacturing the same.

[0014]

A bracket for orthodontics according to claim 1 contains ZrO ₂ as a main component and Gd ₂ O ₃ and Yb.
It is characterized by comprising a partially stabilized zirconia sintered body stabilized with one or more rare earth metal oxides selected from the group consisting of ₂ O ₃ , Ho ₂ O ₃ and Dy ₂ O ₃ .

The orthodontic bracket of claim 2 is Zr.
O ₂ as a main component, Y ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O
Stabilized with one or more rare earth metal oxides selected from the group consisting of ₃ , Ho ₂ O ₃ , Dy ₂ O ₃ and La ₂ O ₃ , and a rare earth metal oxide as a stabilizer It is characterized in that it is composed of a partially stabilized zirconia sintered body in which the proportion of Y ₂ O ₃ in it is 30 to 70 mol%.

An orthodontic bracket according to a third aspect is the orthodontic bracket according to the first or second aspect, wherein the total content of the rare earth metal oxide is 1.5 to 3.0 mol%. And

An orthodontic bracket according to claim 4 is the orthodontic bracket according to any one of claims 1 to 3, further comprising ZnO as a sintering aid in an amount of 0.5 mol% or less. The average crystal grain size of tetragonal zirconia is 1 μm
It is characterized by the following.

An orthodontic bracket according to claim 5 is the orthodontic bracket according to any one of claims 1 to 4, further comprising V, Cr, Mn, Fe, and
It is characterized in that it contains 0.7 mol% or less of an oxide of one or more elements selected from the group consisting of Co, Ni, Sr, Pr, Nd, Sm, Eu, Er and Tm.

A method for manufacturing an orthodontic bracket according to claim 6 is a method for manufacturing the orthodontic bracket according to any one of claims 1 to 5, which is a chemical synthesis method or an oxide powder. It is characterized in that the raw material powder obtained by the method of mixing the above is molded, and the obtained molded body is sintered at 1200 to 1450 ° C.

The present invention will be described in detail below.

In the orthodontic bracket of the present invention, Gd ₂ O ₃ , Yb ₂ O ₃ and Ho ₂ O are used as stabilizers.
1 or 2 or more rare earth metal oxides selected from the group consisting of ₃ and Dy ₂ O ₃ , or Y ₂ O ₃ and Gd ₂ O
₃ , Yb ₂ O ₃ , Ho ₂ O ₃ , Dy ₂ O ₃ and La ₂ O
One or more and selected from the group consisting of _3, the ratio of Y ₂ O ₃ of a rare earth metal oxide as a stabilizer is 3
It is used so as to be in the range of 0 to 70 mol%.

The stabilizer for the zirconia sintered body for brackets is required to have such conditions that there is almost no coloring due to addition and that the strength is not inferior to that of a general partially stabilized zirconia sintered body. It is important that the strength is not deteriorated by such a surface treatment process, but Gd ₂ O ₃ , Yb ₂
The partially stabilized zirconia sintered body using O ₃ and Dy ₂ O ₃ as a stabilizer has a milky white color and can be colored in various color tones including the color tone of natural teeth by adding a colorant described later. Further, the partially stabilized zirconia sintered body using Ho ₂ O ₃ as a stabilizer becomes a pale pink colored sintered body, and a sufficiently aesthetic material can be obtained without adding a coloring agent. Moreover, the mechanical strength is comparable to that of a general partially stabilized zirconia sintered body, and even if the composition of the stabilizer is small, it has better thermal stability than the conventional Y ₂ O ₃ stabilization system. You can get a unity.

In the present invention, the total content of the rare earth metal oxide stabilizer in the partially stabilized zirconia sintered body is preferably in the range of 1.5 to 3.0 mol%,
It is more preferably in the range of 1.7 to 2.5 mol%. If the total content of the stabilizers is less than 1.5 mol%, the phase stability of the tetragonal phase becomes poor, and the minimum thermal stability required for the bracket cannot be secured. On the other hand, when the total content of the stabilizers exceeds 3.0 mol%, on the contrary, the phase stability of the tetragonal phase becomes too good, and a sintered body having high fracture toughness cannot be obtained. Particularly, by setting the total content of the stabilizers in the range of 1.7 to 2.5 mol%, it becomes possible to achieve both good thermal stability as a bracket and high fracture toughness.

When Y ₂ O ₃ is used as the stabilizer, the proportion of Y ₂ O _{3 in} the stabilizer is in the range of 30 to 70 mol%. If the proportion of Y ₂ O ₃ exceeds 70 mol%, Gd ₂ O ₃ , Yb ₂ O ₃ , Ho ₂ O ₃ , Dy ₂ O.
_The effect of improving thermal stability cannot be expected by the combined addition of ₃ , ₃ and La ₂ O ₃ . When the proportion of Y ₂ O ₃ is less than 30 mol%, Y
_This is not preferable because the features of high strength and low temperature sinterability, which are advantages of the ₂ O ₃ stabilizing system, are impaired. That is, Y ₂ O ₃ and Y ₂ O ₃
Combined with the aforementioned specific rare earth oxide other than by 30-70 mol% ratio of Y ₂ O ₃ in the stabilizer, high strength and low temperature, which is the advantage of the Y ₂ O ₃ stabilized system Sinterability can be utilized.

In the zirconia sintered body constituting the orthodontic bracket of the present invention, the average crystal grain size of tetragonal zirconia is preferably 1 μm or less. When the average crystal grain size of tetragonal zirconia exceeds 1 μm,
There is a possibility that the phase stability of tetragonal zirconia deteriorates and the minimum thermal stability required for the bracket cannot be secured.

In the present invention, when ZnO is contained in an amount of 0.5 mol% or less as a sintering aid, the sintering temperature is about 1.
It is possible to lower the temperature by 00 ° C., and it is possible to further suppress the average crystal grain size of tetragonal crystals. Therefore, Y ₂ O
_{Even in the} raw material powder not containing ₃ , it becomes easy to secure the thermal stability. It is not preferable to add ZnO in excess of 0.5 mol% because the strength of the sintered body will decrease. Therefore, the amount of ZnO added is 0.5 mol% or less.

Further, in order to enable sintering at a temperature as low as possible, it is desirable that the raw material powder used has a specific surface area of 10 m ² / g or more.

In the zirconia orthodontic bracket of the present invention, V, Cr, Mn, and
Fe, Co, Ni, Sr, Pr, Nd, Sm, Eu, E
One or more oxides of elements selected from the group consisting of r and Tm can be contained in an amount of 0.7 mol% or less. As described above, the bracket made of the zirconia sintered body can improve the aesthetics by providing a natural tooth-like color tone. In order to obtain a natural tooth-like color tone, SrO which develops a brown color when added to zirconia is added alone, or an oxide (Pr ₆ O ₁₁ , Fe ₂ O ₃ ,
Sm ₂ O ₃ ) and oxides (Er ₂ O ₃ , Eu ₂ O ₃ ) that develop reddish purple (Cr ₂ O ₃ ) or pink color may be added in combination. Further, in addition to the basic combination, the following oxides may be supplementarily added to further finely adjust the color tone. For example, to darken the tone, Mn
The O _2, to make any greenish _{NiO, Tm 2 O 3, V} 2 O
To add ₃ and bluish, a small amount of CoO may be added.

If the content of these colorants (the total content when two or more kinds are used in combination) exceeds 0.7 mol%,
It is not preferable because the color tone becomes too dark and the aesthetics deteriorate. Therefore, the content of the colorant is 0.7 mol% or less.

Among the colorants, SrO, Pr ₆ O ₁₁ ,
Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Er ₂ O ₃ , T
m ₂ O ₃ has a function of stabilizing tetragonal zirconia. Therefore, when containing these rare earth metal oxides as a colorant, the total of the rare earth metal oxides as the stabilizer and the content of these rare earth metal oxides for the colorant is the stabilizer. Adjust to the content.

The orthodontic bracket of the present invention as described above can be manufactured, for example, as follows. That is, first, a high-purity aqueous solution of zirconium oxychloride and 1 selected from Gd, Yb, Y, Ho, Dy, and La.
An aqueous solution of one or more rare earth metal chlorides so that the total amount of the rare earth metals is 1.5 to 3.0 mol% in terms of oxide, and the proportion of Y ₂ O ₃ in the oxide is 30 to 70 mol% is mixed and the well-known coprecipitation method, hydrolysis method,
The precipitate obtained by a chemical synthesis method such as a thermal decomposition method is dried,
After calcination at 800 to 1100 ° C., the raw material powder is obtained by crushing with a crusher such as a ball mill. The specific surface area value of this raw material powder can be adjusted by the calcination temperature, and the powder having a larger specific surface area can be obtained by calcination at a lower temperature. In addition, V, Cr, Mn, Fe, Co, Ni, Sr, Pr, N for coloring
1 selected from the group consisting of d, Sm, Eu, Er and Tm
When the oxides of one or more elements are mixed, it is sufficient to mix them at the same time as an aqueous solution of a water-soluble salt of these elements, for example, a chloride solution, at the time of mixing the aqueous solutions. Further, these colorant components may be mixed with the zirconia raw material powder as an oxide powder or as a solution of a soluble salt.

The method for producing the raw material powder for the orthodontic bracket of the present invention is not limited to the above method, and the same raw material powder can be obtained by the metal alkoxide method, the sol-gel method or the vapor phase method. Although the strength is lower than that of the above method, it is also possible to obtain a raw material powder by adding and mixing some or all components by a wet mixing method.

Then, the raw material powder thus obtained is molded by a known molding method, and after degreasing the molded body,
1200 to 1450 ° C at a heating rate of 20 to 300 ° C / hour
The temperature is raised to 40 ° C., the temperature is maintained for 30 minutes to 3 hours, sintering is performed, the temperature is cooled to 400 to 700 ° C. at a rate of 100 to 500 ° C./hour, and then naturally cooled. As a result, a sintered body having a desired composition, crystal structure, and crystal grain size can be obtained. If the sintering temperature is less than 1200 ° C, the sintering is insufficient,
Above 1450 ° C, the average crystal grain size of the tetragonal phase of the sintered body obtained for grain growth exceeds 1 μm, the phase stability deteriorates, and the minimum required thermal stability as a bracket is secured. Can not do.

In the present invention, it is more preferable that the obtained sintered body is HIP-treated in a non-reducing atmosphere. By this HIP treatment, most of the pores in the sintered body can be eliminated, which results in a bending strength of about 25%.
At the same time, the material can be made to be transparent and the aesthetics can be further improved. In this case, the HIP processing conditions are 1200 to 1450 ° C. and 700 to 2000 atm.
It is preferably 0 to 120 minutes.

In order to process an orthodontic bracket from the obtained sintered body, a usual grinding method using a diamond grindstone or the like can be used. However, since partially stabilized zirconia has poor workability, it is processed into a bracket shape at the stage of calcining before sintering, or it is formed into a bracket shape by a die molding method, an extrusion molding method, an injection molding method, or the like. It is desirable to form a close compact and sinter it.

[0036]

[Function] As a stabilizer, Gd ₂ O ₃ , Yb ₂ O ₃ , Ho
By using one or more selected from the group consisting of ₂ O ₃ and Dy ₂ O ₃ , dentition having excellent aesthetics, high mechanical strength such as fracture toughness, and excellent thermal stability. An orthodontic bracket is obtained.

Further, Y ₂ O ₃ and Gd ₂ are used as stabilizers.
O ₃ , Yb ₂ O ₃ , Ho ₂ O ₃ , Dy ₂ O ₃ and La ₂
Y ₂ occupying in the rare earth metal oxide as a stabilizer in combination with one or more selected from the group consisting of O ₃
When the proportion of O ₃ is 30 to 70 mol%, Y ₂ O
It is possible to obtain an orthodontic bracket excellent in aesthetics, mechanical strength, and thermal stability while effectively obtaining the effects of high strength and low temperature sintering by using ₃ .

Further, when ZnO is contained in an amount of 0.3 mol% or less as a sintering aid, low temperature sintering becomes possible,
It is possible to obtain an orthodontic bracket having a crystal particle diameter of 1 μm or less and having excellent thermal stability.

Further, V, Cr, Mn, Fe, Co, N
By containing at least 0.7 mol% in total of one or more oxides selected from the group consisting of i, Sr, Pr, Nd, Sm, Eu, Er and Tm, the aesthetic property is further improved. An enhanced orthodontic bracket can be obtained.

[0040]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Example 1 An aqueous solution containing a predetermined amount of ZrOCl ₂ and GdCl ₃ dissolved therein was added to p.
H10 was added dropwise to ammonia water, the generated precipitate was filtered, washed with water, and then dried at 120 ° C. The dried powder was lightly crushed in a mortar and then calcined at 850 ° C. for 2 hours to obtain a powder having a specific surface area of 19 m ² / g. A predetermined amount of SrCO _{3 as a} coloring component and ZnCO ₃ as a sintering aid were added to the calcined powder, and the mixture was mixed in a ball mill for 24 hours with ethanol as a dispersion medium, and the mixed slurry was dried and then crushed in a mortar. A raw material powder was obtained. Next, this raw material powder was molded into a bracket shape and a test piece shape for measuring physical properties by an injection molding method, and was degreased. Then, in an electric furnace, the temperature was raised to the temperature shown in Table 4 at a heating rate of 100 ° C./hour, sintered at that temperature for 2 hours, and cooled to about 600 ° C. at a temperature lowering rate of 300 ° C./hour. After cooling naturally, a sintered body having a bracket shape and a test piece shape for measuring physical properties was obtained.

For test pieces for measuring physical properties, in air, 2
Heat treatment was performed at 00 ° C. for 10 hours, and thermal stability was evaluated from changes in bending strength (JIS R1601) before and after the heat treatment. Also, the crystal grain size and fracture toughness value K _1C (JIS
R1601 by IF method) was measured, and the results are shown in Table 5. On the other hand, the bracket-shaped sintered body was barrel-polished to give gloss, and its color tone was observed.
It was shown to.

Examples 2 to 30 and Comparative Examples 1 to 28 Types and amounts of stabilizers and colorants, ZnO as a sintering aid
Table 1 shows the addition amounts of the above, and the sintering temperature is shown in Table 5
A sintered body was obtained in the same manner as in Example 1 except that the temperature was set to 8, and the crystal grain size, bending strength, fracture toughness and color tone were examined, and the results are shown in Tables 5-8.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

[Table 4]

[0048]

[Table 5]

[0049]

[Table 6]

[0050]

[Table 7]

[0051]

[Table 8]

As is clear from the above results, the sintered bodies according to the examples show a high bending strength of 780 to 1340 MPa and a very high fracture toughness of 8.1 to 13.4 MPa √m, and more than 200 in air. Even after the heat treatment at 10 ° C. for 10 hours, there was almost no decrease in strength. Further, by barrel-polishing the bracket-shaped sintered body, it was possible to obtain a bracket having a gloss and a highly aesthetic color tone shown in Tables 5 and 6.

On the other hand, those which deviate from the preferred composition of the present invention (Comparative Examples 1 to 9, 11 to 17, 19 to 21, 23)
25, 27, 28) have low fracture toughness, or
Bending strength is significantly reduced by heat treatment at 200 ° C. for 10 hours in air, and thermal stability is low. Further, the color tone of the sintered body is completely different from that of natural teeth, and the aesthetics is not sufficient. Furthermore,
Even if it satisfies the preferred composition of the present invention, if the sintering temperature is too high (Comparative Examples 10, 18, 22, 26),
Thermal stability is significantly impaired.

Example 31 The bracket obtained in Example 4 was subjected to HIP treatment for 30 minutes at 1300 ° C. and 2000 atm using argon gas containing 5% oxygen as a pressure medium. Next, an alcohol solution containing 0.1% of a commercially available silane coupling agent (γ-methacryloxypropyltrimethoxysilane) was applied to the adhesive surface of the bracket and dried at 120 ° C. for 2 hours with a dryer. . This bracket was adhered to an acrylic pedestal with a straightening adhesive, and after 24 hours, the adhesive strength was measured by a tensile test. As a result, the bracket not treated with the silane coupling agent was peeled off at 2 kg, whereas the bracket treated with the silane coupling agent was peeled off at 23 kg. No reduction in the strength of the bracket due to the silane coupling treatment was observed.

[0055]

As described in detail above, the orthodontic bracket of the present invention is made of a partially stabilized zirconia sintered body having higher mechanical strength, especially fracture toughness than the conventional zirconia sintered body. Without any restrictions on
It is possible to obtain a bracket with a shape close to that of a metal bracket and having good operability. Furthermore, since the material is excellent in thermal stability, strength deterioration does not occur even if surface treatment is performed to improve adhesive strength. Further, since it is possible to make the color tone closer to that of natural teeth as compared with metal, it is possible to obtain a bracket having excellent aesthetics.

Such an orthodontic bracket of the present invention can be easily and efficiently manufactured by the method of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Ayuzawa 5-6-25 Kachi, Okayama City, Okayama Prefecture (72) Inventor Ryo Nakayama 957-5 Ouchi, Kurashiki City, Okayama Prefecture (72) Takashi Hino Bizen Okayama Prefecture 1931 Ibe, Ichi

Claims (6)

[Claims] 1. Gd ₂ O ₃ , Y containing ZrO ₂ as a main component
a partially stabilized zirconia sintered body stabilized with one or more rare earth metal oxides selected from the group consisting of b ₂ O ₃ , Ho ₂ O ₃ and Dy ₂ O _3. Braces for orthodontics. 2. ZrO ₂ as a main component, Y ₂ O ₃ and G
d ₂ O ₃ , Yb ₂ O ₃ , Ho ₂ O ₃ , Dy ₂ O ₃ and L
stabilized with rare earth metal oxides with one or more selected from the group consisting of a ₂ O _3, and the ratio of Y ₂ O ₃ accounts for the rare earth metal oxide as a stabilizer is 30
An orthodontic bracket comprising a partially stabilized zirconia sintered body of 70 mol%. 3. The orthodontic bracket according to claim 1 or 2, wherein the total content of the rare earth metal oxide is 1.5 to.
An orthodontic bracket characterized by being 3.0 mol%. 4. The orthodontic bracket according to any one of claims 1 to 3, further comprising Zn as a sintering aid.
An orthodontic bracket containing O in an amount of 0.5 mol% or less and having an average crystal grain size of tetragonal zirconia of 1 μm or less. 5. The orthodontic bracket according to claim 1, further comprising V, as a coloring agent.
Cr, Mn, Fe, Co, Ni, Sr, Pr, Nd, S
An orthodontic bracket containing 0.7 mol% or less of an oxide of one or more elements selected from the group consisting of m, Eu, Er and Tm. 6. A raw material powder obtained by a chemical synthesis method or a method by mixing oxide powders is molded, and the molded body thus obtained is
The method for manufacturing an orthodontic bracket according to any one of claims 1 to 5, wherein sintering is performed at 200 to 1450 ° C.