JPH11276504A - Orthodontic bracket and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the abrasion resistance, corrosion resistance, and chemical resistance by forming cutting groove sections on a base surface to be bonded to a tooth fang surface. SOLUTION: The orthodontic bracket is constituted of a base section 1, a supporting section 2, a guide groove 3, guide wing sections 4, cutting sections 5, and cutting groove sections 6, and the base section 1 forms an entire bonding surface. Since the cutting groove sections 6 are formed on opposite edges on the rectangular base 1, a metal mold can be used and the bracket can be formed from injection molding. When a frame is provided on a recess section to be formed as the bonding surface, intensity of the bracket itself can preferably be improved. Thereby a bonding area becomes smaller by the frame section, however a surface inequality of the bonding surface can be remained after polishing. A medium does not directly polish the bonding surface in a barrel polish after roughening the bonding surface with a corrosive solution. Surface roughness without uncomfortable feeling can be realized thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orthodontic bracket having excellent strength and good adhesion to teeth.

[0002]

2. Description of the Related Art Orthodontic brackets are generally formed of metal and are usually bonded directly to the teeth. Therefore,
It is important to have good adhesion between the orthodontic bracket and the teeth. Improvements have been made over time in metal brackets, and the adhesion itself has generally reached acceptable levels. In recent years, the aesthetic sensation has increased,
Ceramics are increasingly used in place of metals. However, since ceramic materials are difficult to fix to teeth, many devices have been proposed to improve the adhesive strength. A method in which an undercut is provided in the base of the bracket, or a method in which fine ceramic particles are adhered to the bonding surface on the bracket side in a green stage as described in Japanese Patent Application Laid-Open No. 5-64644, diffusion bonding is performed by firing, and unevenness is provided on the bonding surface. Has been proposed. Inadvertently providing an undercut in the bracket base improves the bonding strength but decreases the strength of the bracket itself. In addition, the surface unevenness of the bonding surface due to the fine ceramic particles has a disadvantage that the strength between the particles and the surface of the bracket is relatively smaller than the bonding strength between the particles and the tooth surface, and the particles are easily peeled off.

[0003] In addition, ceramics used for the brackets are not sufficiently strong with porcelain or ceramics called so-to-mo, and there is a high possibility that the ceramics will be damaged when tightened with a wire. Among fine ceramics, alumina,
Although mullite and the like are sometimes used, the bracket itself is complicated in shape and has a structure in which stress is easily concentrated particularly in a narrowed portion, and therefore, the bracket is often damaged. Furthermore, from the aesthetic point of view, white color is fundamental, but none of them have a very close delicate color tone and translucency to resemble teeth.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a material and structure of an orthodontic bracket which can solve the above-mentioned problems and maintain good adhesive strength with a tooth, and a method of manufacturing the same.

In recent years, ceramic brackets have been used in place of metal brackets. Ceramics have corrosion resistance and aesthetics that are not found in metals, but are difficult to mold, and the manufacturing process is complicated, so they are expensive. However, conventional ceramic brackets are mainly composed of alumina,
There has been a problem that a small impact causes a defect or a crack, or if the adhesive is weak, the chip falls off.

The present invention solves these problems and provides a bracket having excellent wear resistance, corrosion resistance, and chemical resistance.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies on orthodontic brackets free from the above-mentioned disadvantages, and as a result, have reached the following invention. That is, an orthodontic bracket that is adhered to the surface of a tooth by an adhesive and holds an orthodontic wire spanned between predetermined teeth, and has a notch in a base portion adhered to the tooth surface. An orthodontic bracket having a groove portion.

Further, in the manufacture of this bracket,
A step of firing zirconia or a composite ceramic containing zirconia in the air, a step of hot isostatic pressing and sintering in a gas atmosphere containing 1 to 20% of oxygen, and immersing in a corrosive solution after firing; The above-mentioned problem is solved by a method for manufacturing an orthodontic bracket, which comprises a step of providing undulations on a surface of a bracket base to be filled, and a step of polishing a bracket surface other than a portion provided with undulations.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In an orthodontic bracket adhered to the surface of a tooth by an adhesive, a notch groove is formed in a base portion adhered to the tooth surface, and the adhesive applied to the back surface of the base portion To be drawn by the notch groove portion, and further, the inside of the notch groove portion provided in the base portion adhered to the tooth surface is formed in a state where it is wider than the entrance diameter on the back surface side of the base portion. Or, it is preferable that the inside of the base portion has a larger diameter than the rear-side entrance of the base portion and is inclined.

A bracket for orthodontic treatment, wherein the notch groove is formed in a base portion of a bracket for guiding the wire, and the cutout groove portion is formed on an edge of a substantially rectangular base portion. This solves the conventional problem and achieves the target performance.

In particular, the bracket material is preferably made of partially stabilized zirconia having an average particle diameter of 1 μm or less or a composite ceramic containing partially stabilized zirconia, and the sintered body has a relative density of 99% or more, ie, The measured density of stabilized zirconia is 6.02.
g / cm ³ or more and the porosity is preferably 1% or less.

Hereinafter, a specific method for carrying out the present invention will be described for a case where an orthodontic bracket is manufactured from partially stabilized zirconia ceramics.

[Powder Type and Synthesis Method] Purity
9% zirconyl oxychloride and yttrium chloride solution was mixed with zirconia (ZrO ₂ ) and yttria (Y ₂ O ₃ )
Is adjusted so that the molar ratio as described above becomes 95: 5 to 98: 2. From the adjusted mixed solution, a hydrolysis method of obtaining crystalline hydrated zirconia in an autoclave set to a temperature of about 100 ° C., or neutralization by adding ammonia water or the like to lower the solubility to reduce the solubility, A zirconia precursor is obtained by a method such as a neutralization coprecipitation method in which zirconium hydroxide and yttrium hydroxide are precipitated, and then fired to obtain a high-strength zirconia powder raw material.

[Characteristics and Physical Properties of Powder] The primary particle size of the powder is affected by the sintering temperature, and when sintering is performed at 800 to 1000 ° C., the powder is distributed in the range of 0.01 to 0.2 μm. The particle size is about 0.1 μm. The secondary particle diameter is measured by a laser diffraction method, and is crushed and adjusted so as to be distributed in a range of 0.01 to 30 μm, and to have an average secondary particle diameter in a range of about 0.5 to 2 μm.

[Granulation and molding method] In addition to the binder, an appropriate amount of a dispersant, a release agent, and an antifoaming agent are added to the powder prepared above.
Prepare a slurry. The amount of the solid component in the slurry is adjusted in the range of 15 to 20% by weight based on 100 parts by weight of the powder. As the binder, a general one of wax type, acrylic type and the like is used.

The slurry is kneaded by a kneader, and a bracket is generally formed by an injection molding method. This method is most suitable for molding a small and complicated shape, and it is easy to mass-produce and reduce the cost.

The molding conditions for injection molding are 140 to 160
C. and an injection pressure of 50 to 60 kg / cm ² .

[Sintering Method] Since the bracket after injection molding contains many organic components such as a binder, it is necessary to degrease it. The degreasing conditions are preferably in the range of 350 to 800 ° C., and the heating and cooling are performed for a sufficient time so as not to cause degreasing cracks.

The compacted body after degreasing is fired in the air or in an atmosphere containing oxygen at a temperature of 1300 to 1500 ° C. for 30 minutes to 3 hours to obtain a dense sintered body. For sintering, a pressure sintering method can be used in addition to a normal atmospheric pressure sintering method.

The sintering temperature and time are set so that the average crystal grain size of ZrO ₂ is 1 μm or less, preferably 0.6 μm or less.
The sintered body density is 5.90 g / cm ³ or more and the porosity is 5%
Control is performed as follows. If the cooling rate during sintering is too slow, a large amount of monoclinic ZrO ₂ will precipitate, so it is preferable to cool at a rate of 5 ° C./min or more.

The sintered body thus obtained has an average crystal grain size of 1 μm or less and a sintered body density of 6.02 g / g.
In cm ³ or more, if the porosity is less than 1%, it can be brought into particular problem without processing step further in order to obtain the same color tone and the tooth, and re sintering by controlling the atmosphere.
The conditions for resintering may be hot isostatic pressing and sintering at 1 to 20 MPa in a gas atmosphere containing 1 to 20% oxygen.
According to this method, it is possible to obtain a very natural color tone of the tooth, and at the same time, there is an advantage that the mechanical properties such as strength and toughness are improved by being dense.

[Processing Method] The sintered bracket body after firing is immersed in a corrosive solution to provide undulations on the surface of the bracket base filled with the adhesive. The corrosive solution may be either an acid or a base, but hot sulfuric acid, hydrofluoric acid, aqua regia, or the like having a strong oxidizing power is suitable for shortening the treatment time.

Next, the surface of the bracket other than the bonding surface is polished. The polishing method is not particularly limited, but barrel polishing is generally performed using a crushing medium having a size that does not enter the bonding surface.

Through the above steps, the ceramic bracket of the present invention can be manufactured.

[Structure and Physical Properties of Sintered Body] The bracket made of zirconia has been described above. As a typical material of the orthodontic bracket of the present invention, in addition to zirconia, alumina-
There is a zirconia-based composite ceramic. In the alumina-zirconia composite ceramics, although not particularly limited, alumina is preferably 0.1 to 85% by weight, more preferably 15 to 80% by weight.
Alumina preferably has a higher purity, and is not particularly limited, but the purity is preferably 99.8% by weight or more. The remaining 15 to 99.9% by weight is zirconia, and zirconia contains Y as a stabilizer.
One or two kinds of ₂ O ₃ and CeO ₂ are contained in 1.5 to 5 mol% with respect to zirconia, and the average crystal grain size of zirconia is 1
It is preferable to use an alumina-zirconia ceramic material in which the average crystal grain size of alumina is 1 μm or less and 50% or more by volume of zirconia exists as a metastable tetragon at room temperature.

Also, ceramics other than alumina can be sufficiently used as composite ceramics if they contain 15 to 85% zirconia.

Preferably, the bracket material of the present invention comprises:
It is desirable that the ceramic material has a Vickers hardness of 1300 kgf / mm ² or more. Hardness is 1300
If it is less than kgf / mm ² , there is not enough hardness, so that abrasion occurs remarkably during use.

Among ceramics used in the bracket of the present invention, there is a material containing 15 to 99.9% by weight of zirconia. If the zirconia content is less than 15% by weight, the amount of zirconia that contributes to the strength improvement due to the stress-induced transformation from tetragonal to monoclinic is small, so that the material cannot achieve an important effect of strength improvement.

Alumina can be added in the range of 0.1 to 5% by weight for the purpose of improving the sinterability of zirconia.

In the material of the present invention, one or two of Y ₂ O ₃ and CeO ₂ as stabilizers are contained in zirconia in an amount of 1.5 to 5 mol% based on zirconia. If it is less than 1.5 mol%, the tetragonal crystal in zirconia will not be stabilized, and the proportion of monoclinic crystal at room temperature will increase, and high strength cannot be expected. On the other hand, if it exceeds 5 mol%, the tetragonal crystal tends to be completely stabilized, and stress-induced transformation at room temperature does not occur, and the strength does not improve. More preferably, it is desirable that Y ₂ O ₃ be contained as a stabilizer in an amount of ₂ to 3.5 mol% based on zirconia.

In the present invention, the average crystal grain size of zirconia is 1 μm or less. If the particle size exceeds 1 μm, zirconia transforms to monoclinic upon cooling, and the strength does not improve and the hardness does not increase. In addition, a preferable average crystal grain size is 0.2 to 0.8 μm, and a more preferable range of the crystal grain size is 0.2 to 0.6 μm.

In the present invention, when alumina is contained,
The average crystal grain size is preferably 1 μm or less.
If it exceeds 1 μm, the hardness decreases, the strength of the alumina substrate decreases, and the transformation of zirconia to monoclinic cannot be suppressed, resulting in a significant decrease in strength.
A more preferred average crystal grain size is 0.5 to 1.0 μm.

In the present invention, preferably, at least 50% by volume of zirconia is a metastable tetragonal crystal at room temperature. When the volume ratio of the tetragonal system is less than 50%, the strength cannot be expected to be improved by the stress-induced transformation from the tetragonal system to the monoclinic system. More preferably, 95% or more is desirable.

In the present invention, when the Vickers hardness of the sintered body is preferably 1300 kgf / mm ² or more,
The wear resistance is further improved. Vickers hardness is 1300k
If it is less than gf / mm ² , the wear resistance of the present material will be significantly reduced.

Further, the bending strength of the sintered body is 65 kgf /
mm ² or more. With a strength higher than this value, a durable bracket having high resistance to impact can be realized. More preferably, the bending strength is 80 k
gf / mm ² or more.

Further, it is preferable to use ceramics having a fracture toughness value of 4 MPa · m ^1/2 or more according to a pre-crack introduction fracture test method in accordance with JISR1607. Accordingly, a durable bracket can be provided without any accidents such as breakage or cracking even after long-term use.

Further, the sintered body is desirably a ceramic containing tetragonal zirconia substantially containing no monoclinic crystal by analyzing the crystal structure by powder X-ray diffraction.

As described above, the ceramic material in the present invention is not particularly limited as long as it is a ceramic material having strength and appropriate wear resistance. However, specific examples include partially stabilized zirconia, particularly Tetragonal zirconia, zirconia-alumina composite material, alumina, mullite and the like can be used. Alumina has high hardness, which is a measure of abrasion resistance, and is 1600 to 2000 kg.
f / mm ² , but the flexural strength is somewhat lower, around 50 kgf / mm ² . The alumina-zirconia composite material has a flexural strength of about 80 kgf / mm ^2, which is higher than that of alumina, and a hardness as high as 1400 kgf / mm ² or more, and also has abrasion resistance. The tetragonal zirconia preferably contains 1.5 to 5 mol% of solid solution Y ₂ O ₃ having an average particle diameter of 1 μm or less and has an average particle diameter of 0.5 to 2 μm. In tetragonal zirconia bending strength 100 kgf / mm ² or more, hardness is preferably used as the 1200~1400kgf / mm ^2. In the alumina-zirconia composite material (ZTA), Zr whose crystal structure is at least 50% by volume is tetragonal
O ₂ in the range of 15 to 99.9% by weight, and Al
The average particle diameter of ₂ O ₃ is preferably 1 μm or less, and the average particle diameter of ZrO ₂ is preferably 1 μm or less.

[Structure of Bracket] As shown in FIG. 1, the structure of the bracket according to the present invention comprises a base 1, a support 2,
It comprises a guide groove 3, a guide wing 4, a cut 5, and a notch 6.

The base portion refers to the entire bonding surface. The bonding surface may be a flat simple smooth surface as shown in FIG. 2, but the outer frame portion is thickened and the bonding surface is depressed as shown in FIG. It is preferable to have a rim structure. With this structure, the adhesive easily enters the concave portion, and the bonding is stabilized. Further, it is more preferable to provide a frame structure as shown in FIG. In this state, the bonding area is reduced only by the beam, but when the bonding surface is moderately roughened with a corrosive solution and barrel polishing is performed, the medium does not directly polish the bonding surface, and the surface roughness of the bonding surface is reduced. Has the advantage of being maintained after polishing. For this reason,
In addition to the sufficient strength of the bracket itself, a good adhesive strength can be obtained.

When the adhesive is applied to the bracket bonding surface and is to be bonded to the tooth, the bonding surface is curved according to the shape of the tooth, so that the entire surface of the bonding surface is completely filled with the adhesive. It is difficult to do. In particular, in a small place such as a canine and a large curvature, the adhesive cannot be filled well, and the bracket tends to fall off. Therefore, the notch groove 6 is formed in the base portion 1 adhered to the tooth surface on the base portion 1 of the bracket.
Is formed, and the adhesive applied to the back surface of the base portion is drawn by the notch groove portion 6. Thereby, the adhesive strength between the bracket and the adhesive and between the tooth and the adhesive is improved.

Further, when the outer frame portion of the bracket is thickened and the bonding surface is depressed by providing a rim,
The adhesive penetrates into the recessed portion, and the bonding surface is easily stabilized. However, if the adhesive part of the bracket is hollow, it becomes difficult for the adhesive to enter the corners when the viscosity of the adhesive is high, and there is sufficient adhesion between the adhesive and the bracket due to the presence of air. As a result, no strength is obtained. To improve this,
It is desirable to provide appropriate surface irregularities on the bonding surface of the bracket so that the adhesive can be easily engaged with the bracket. In order to make the bonding surface uneven, a method of etching with a corrosive liquid or heat treatment is simple and desirable. However, chemical etching with a corrosive liquid is more preferable because the surface state is sharp and a good state is obtained.

Further, an undercut-shaped cut groove having an appropriate size is provided in the rim portion, so that the engagement between the adhesive and the bracket is enhanced, and the adhesive strength can be improved. The undercut is formed such that the inside of the notch groove 6 provided in the base portion bonded to the tooth surface is wider than the entrance diameter on the back surface side of the base portion, or the inside of the base portion is formed in the base portion 1. It is characterized in that it has a larger diameter than the back side entrance and is inclined. Further, the cut groove allows the air contained therein to escape to the outside when the adhesive is filled, that is, has a role of releasing air. It is very easy to provide the cut groove in the rim portion in this way, and the adhesive strength between the adhesive and the bracket can be improved.

In particular, if the notched grooves 6 are formed at the opposite edges of the rectangular base, the die can be worked, and a bracket having an undercut rim is formed at the time of injection as shown in FIG. You. 5 shows a mold for injection molding the bracket of FIG. 5. The hatched portion corresponds to the mold. The powder slurry is injected from the upper or lower mold of the combined mold as shown. The important thing in this figure is that if an undercut portion is provided in the base portion of the bracket, the lower mold punch does not come out downward, so it must be designed to slide in a manner perpendicular to the paper surface.

Further, by providing a frame in the concave portion serving as the bonding surface, the strength of the bracket itself can be improved, which is more preferable. In this state, the bonding area is reduced only in the frame part, but when the bonding surface is appropriately roughened with a corrosive liquid and then barrel polished, the medium does not directly polish the bonding surface, and the surface unevenness of the bonding surface is reduced. It has the advantage of being maintained after polishing.

These shapes may be processed after sintering. However, sintered ceramics have extremely high hardness, and it is difficult to process micron-order products on small products such as brackets. It is desirable to process. For example, in the case of using injection molding, a cut groove 6 may be provided in the rim portion of the mold so as to be undercut, or a cut groove 6 having the above-described shape may be provided after injection molding.

After such processing, the surface is polished, and the surface roughness is adjusted to be not more than 0.2 μm in center line average roughness. With this level of surface roughness, a surface state close to natural teeth without a sense of discomfort can be realized. The surface roughness may be measured by using a stylus or a laser or other optical system phase difference.However, if the detection accuracy is limited, an atomic force microscope or a scanning electron microscope with multiple detectors may be used. A method of measuring the surface roughness by using a microscope is preferable because it enables highly accurate measurement with good reproducibility.

[0048]

[Methods for measuring physical properties] The density, porosity, average crystal grain size, Vickers hardness, and tetragonal crystal ratio of zirconia contained in the bracket material were determined as follows.

(1) Density The density was determined by the Archimedes method.

(2) Porosity The porosity of alumina-zirconia ceramics
With the theoretical density of zirconia being 6.10 g / cm ³ and that of alumina being 3.99 g / cm ³ , the theoretical density of the composite ceramic was determined by the compounding ratio, and the value of the Archimedes method previously determined was divided by the value of the theoretical density. I asked for it.

(3) Average Crystal Particle Size The average particle size is determined by polishing the zirconia surface, etching the surface, and measuring the etched surface with a scanning electron microscope.
The number average diameter of the circle-equivalent diameter of the crystal grains was determined by image processing in a 2,000 to 20,000-fold photograph.

(4) Flexural strength The flexural strength was measured in accordance with the JIS R 1601 three-point flexural strength test method.

(5) Vickers Hardness The Vickers hardness is the diagonal length of an indentation formed when a ceramic surface is carefully mirror-polished and a Vickers indenter is pressed into the ceramic surface with a load P [kgf]. ], The following formula Hv [kgf / m
m ² ] = 1.85437 × P / d ^2. After measuring 7 points, the average value of 5 points excluding the highest value and the lowest value was obtained.

(6) Tetragonal zirconia ratio The tetragonal zirconia ratio was determined by 2θ = 30.2 when the material surface was carefully mirror-polished and analyzed by X-ray diffraction.
The integrated intensity T (111) of the diffraction peak of the tetragonal (111) plane appearing near ° and the integrated intensity M (11) of the diffraction peak of the monoclinic (111) plane appearing near 2θ = 28.2 °.
1) and the monoclinic (11) appearing near 2θ = 31.5 °
From the integrated intensity M (111 ⁻ ) of the diffraction peak on the 1 ⁻ ) plane, the following equation is obtained: T (111) / ΔT (111) + M (111) + M (1)
11 ⁻ )｝ × 100 [% by volume]. Incidentally, 1 ^- represents -1.

(7) Adhesive strength After the bovine tooth enamel whose surface has been finished with a No. 600 grindstone is treated with phosphoric acid, it is washed with water and dried. Next, an adhesive is applied to the portion on the bonding surface of the bracket, and pressed against the enamel surface for 30 minutes. 500 heat cycles from 0 ° C to 80 ° C
After repeating 0 times, a shear test was performed to evaluate the adhesive strength. The shear test method is to fix the enamel plate on a jig,
0.2m after contacting the upper punch with the bracket on the testing machine
Lower at a speed of m / min. The adhesive strength is calculated from the load when the bracket comes off and the area of the adhesive part. The unit is kgf / cm ² . In particular, as typical adhesives, “Banavia” 21 manufactured by Kuraray Co., Ltd. and “Super Bond C & B” manufactured by Sun Medical Co., Ltd. are often used, but other adhesives may be used as appropriate.

[0056]

The present invention will be specifically described below with reference to the following examples. However, the present invention is not limited to this.

Example 1 A solution of 99.9% pure zirconium oxychloride and yttrium chloride was converted to zirconia and yttria.
A mixture is prepared so as to have a molar ratio of 97.25: 2.75, and aluminum chloride is further added thereto so as to be 0.5% by weight in terms of Al ₂ O ₃ . From the prepared mixed solution, crystalline hydrated zirconia to be a zirconia precursor was obtained in an autoclave set at 95 ° C. This is 8
It is fired at 00 ° C. to obtain a powder raw material having an average particle diameter of 0.12 μm.

In addition, 100 parts by weight of powder solids
18 parts by weight of a wax binder was added and kneaded using a kneader, followed by injection molding. An inverted tapered pin was provided on the bracket outer frame of the mold so that a cutout groove was formed in the molded body, and the structure was formed of the above-described rim and frame.

The molded body was degreased at 500 ° C.
After firing at 400 ° C for 1 hour, 1400 ° C for 1 hour, 2 hours
By hot isostatic pressing under an argon gas atmosphere containing 5% of oxygen at 000 atm, a density of 6.08 g /
A dense sintered body having cm ³ and a porosity of 0.3% was obtained. After this was corroded with a 40% hydrofluoric acid solution, it was finally finished to a mirror surface with a maximum roughness of 0.03 μm by barrel polishing.

[0060] The average crystal grain size of the ZrO _2: proportion of tetragonal 0.3 [mu] m ZrO _2: 100 vol% Vickers hardness: the surface roughness of 1350kgf / mm ² sintered body was measured by an atomic force microscope.
The average surface roughness was 5.4 nm and the maximum roughness was 76 nm. The surface of the observed ball has a width of 0.5
μm or more, depth 0.35 μm or more, length 10 μ
m or more was not found.

The crystal structure of the sintered body was analyzed by powder X-ray diffraction.
Was zirconia.

The adhesive used for the adhesion test was "Super Bond C &B" manufactured by Sun Medical. The measurement result of the adhesive strength was 206 ± 55 kgf / cm ² . Since the adhesive strength of the conventional type is at a level of 150 kgf / cm ² , the strength is improved by 30% or more.

Example 2 70% by weight of alumina powder having an average particle diameter of 0.3 μm and purity of 99.8%, and 30% by weight of zirconia powder having an average particle diameter of 0.1 μm containing 3 mol% of yttria were used. At a ratio, using a medium stirring type mill, wet mixing and pulverization in pure water for 3 hours to adjust the average aggregate particle size to 0.6 μm,
17 parts by weight of an acrylic binder was added to 100 parts by weight of the solid content of the powder, and kneaded with a kneader to obtain a mixed powder.

Next, a bracket having a predetermined shape is manufactured by injection molding. An inverted tapered pin is provided on the outer frame of the mold so that a cutout groove is formed in the molded body,
The structure includes the rim and the frame described above.

The molded body was degreased at 500 ° C.
After firing at 550 ° C for 1 hour, 1500 ° C for 1 hour, 2 hours
By hot isostatic pressing under an argon gas atmosphere containing 5% oxygen at 000 atm, a density of 4.54 g /
A dense sintered body having cm ³ and a porosity of 0.4% was obtained. After this was corroded with a 40% hydrofluoric acid solution, it was finally finished to a mirror surface with a maximum roughness of 0.05 μm by barrel polishing.

The above molded product was heated at 1550 ° C.
After sintering for a time, an alumina-zirconia composite ceramics bracket was obtained.

[0067] The average crystal grain size of the Al ₂ O _3: an average crystal grain size of 0.8 [mu] m ZrO _2: proportion of tetragonal 0.5 [mu] m ZrO _2: 100 vol% Vickers hardness: adhesion of 1710kgf / mm for ² adhesion test The agent used was "Super Bond C &B" manufactured by Sun Medical. The measurement result of the adhesive strength was 166
It was ± 44 kg / cm ² . Conventional adhesive strength is 15
Since the level is 0 kg / cm ² , the strength is 10%
Improvement was seen.

[0068]

According to the present invention, metal has abrasion resistance, corrosion resistance, chemical resistance, and aesthetic feeling that are not found in metal, and since it has excellent mechanical strength, there is no occurrence of chipping or cracking due to impact.
A ceramic bracket that does not fall off because of its excellent adhesive strength can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an orthodontic bracket according to the present invention.

FIG. 2 is a schematic view showing an example in which a base portion of the orthodontic bracket of the present invention has a simple smooth surface.

FIG. 3 is a schematic view showing an example in which a base portion of the orthodontic bracket of the present invention is in a depressed state.

FIG. 4 is a schematic view showing an example of the orthodontic bracket of the present invention in which a beam is applied in a state where the base portion is depressed.

FIG. 5 is a schematic view showing an example of manufacturing the orthodontic bracket of the present invention by an injection molding method.

[Explanation of symbols]

 1: Base part 2: Support part 3: Guide groove 4: Guide wing part 5: Notch part 6: Notch groove part

Claims (6)

[Claims] Claims: 1. An adhesive is attached to the surface of a tooth by an adhesive,
An orthodontic bracket for holding an orthodontic wire bridged between predetermined teeth, the orthodontic bracket having a cutout groove in a base portion adhered to a tooth surface. bracket. 2. A cut-out groove provided in a base portion bonded to a tooth surface is formed so as to be wider than an entrance diameter on a back surface side of the base portion, or an inside of the base portion is formed in a base portion. The orthodontic bracket according to claim 1, wherein the bracket has a larger diameter than the rear side entrance and is inclined. 3. The base according to claim 1, wherein the base has a rectangular shape, and has a cutout groove at an edge thereof.
An orthodontic bracket according to item 1. 4. The orthodontic bracket according to claim 1, wherein the bracket is made of zirconia or a composite ceramic containing zirconia having an average particle diameter of 1 μm or less. 5. The orthodontic bracket according to claim 1, wherein the relative density of the composite ceramic is 99% or more and the porosity is 1% or less. 6. A step of firing zirconia or a composite ceramic containing zirconia in the air, a step of hot isostatic pressing and sintering in a gas atmosphere containing 1 to 20% of oxygen, and a step of post-firing corrosion. Manufacturing a bracket for orthodontic treatment, comprising: immersing in an aqueous solution to form undulations on a surface of a bracket base to be filled with an adhesive; and polishing a surface of the bracket other than the portions provided with undulations. Method.