KR101316946B1 - Ceramic compositions for orthodontics brackets, orthodontics brackets manufactured using the same and preparation method thereof - Google Patents

Abstract

PURPOSE: A ceramic composition for an orthodontic bracket, the orthodontic bracket manufactured by the same, and a manufacturing method thereof are provided to improve a correction effect. CONSTITUTION: A ceramic composition for an orthodontic bracket includes alumina oxide, 1-2 wt% of magnesium oxide or its precursor, and 30-40 wt% of binder. The orthodontic bracket includes a wire insertion part, a ligation part, a tooth fixing part, and a correction hinge part. A method for manufacturing the orthodontic bracket comprises: a step of preparing composite powder by mixing alumina oxide and magnesium oxide or its precursor; a step of preparing a ceramic material by mixing the composite powder and polymer binders; a first molding step for molding the ceramic material into a bracket shape; a first heat-treatment step for heat-treating the molded product; a second molding step for molding the molded product through hot isostatic pressing; and a coating step for coating glass beads on the surface of the molded product. [Reference numerals] (AA) Step of producing composite powder; (BB) Step of producing ceramic composition; (CC) Step of firstly molding; (DD) Step of firstly heat treating; (EE) Step of secondly molding; (FF) Step of coating

Description

Ceramic composition of orthodontic brackets, orthodontic brackets prepared therefrom and a method of manufacturing the same {Ceramic Compositions for Orthodontics Brackets, Orthodontics Brackets manufactured using the same and Preparation method

The present invention relates to a ceramic composition of orthodontic brackets, orthodontic brackets and methods for producing the same.

Ceramic brackets used for orthodontics should have a certain strength when straightening with wires on the teeth and have good esthetics. Existing ceramic brackets are excellent in light transmittance and aesthetically superior, while stiffness is lowered, so that the breakage of the bracket frequently occurs during calibration, and even after the calibration, there is a problem of breaking even by a small impact. This is because the temperature is increased to 1600 ° C. or higher during the heat treatment step in the manufacture of the ceramic bracket to increase the light transmittance. That is, the polycrystalline alumina decreases in strength as the particle size increases, and this high heat treatment temperature causes the alumina particles of the bracket to grow to lower the strength. In addition, the ceramic bracket has a low friction coefficient, so that the adhesive strength is weak during the procedure, the problem of detachment from the teeth occurs. In order to solve this problem, the conventional coating on the bottom of the bracket uses spheroidized alumina, spheroidized zirconia, and spheroidized mullite, but these materials require high temperature when adhered to the bottom of the bracket, and the bracket becomes opaque after adhesion. Occurs.

An object of the present invention for solving the above problems is to provide a ceramic composition of the orthodontic bracket that can provide the orthodontic bracket with improved strength while maintaining light transmittance and aesthetics.

Another object of the present invention is to provide a bracket for orthodontics, which is made of the bracket ceramic composition and has improved adhesion to teeth.

Still another object of the present invention relates to a method for manufacturing the orthodontic bracket.

According to an aspect of the present invention,

Alumina oxide;

1 to 2 wt% of magnesium oxide or a precursor thereof based on the total weight of the alumina oxide; And

It relates to a ceramic composition of the orthodontic bracket comprising; 30 to 40% by weight of the binder based on the total weight of the alumina oxide.

Purity of the alumina oxide may be 99.99% or more, and the average particle size may be 0.3 μm or less.

The binder may be at least one of low density polyethylene, paraffin wax and stearic acid. The binder may be a mixture of low density polyethylene: paraffin wax: stearic acid = 6: 3: 1 ratio (mass).

Another object of the present invention is to provide

In the orthodontic bracket comprising a wire insertion portion, self-ligating portion, tooth fixing portion and orthodontic hinge (hinge),

The bracket is molded from the ceramic composition of claim 1 orthodontic bracket,

It relates to a dental orthodontic bracket coated with a glass bead surface of the tooth fixing.

The particle size of the glass beads may be 70 μm to 120 μm.

A further object of the present invention is to provide

Alumina oxide; And magnesium oxide or a precursor thereof;

The composite powder; And preparing a ceramic composition of the orthodontic bracket for mixing the polymer binder;

A first molding step of molding the ceramic composition of the orthodontic bracket to have a bracket shape;

A first heat treatment step of heat-treating the bracket molded body formed after the molding step;

A second molding step of molding the bracket molded body to hot hydrostatic pressure after the heat treatment step; And

And a coating step of coating glass beads on the surface of the bracket molded body after the second molding step.

The heat treatment step is a binder removal step of removing the binder by maintaining for 1 to 8 hours at 500 ℃ to 600 ℃; And a particle densification step that is maintained at 1550 ° C. to 1580 ° C. for 30 minutes to 1 hour.

The first molding step may be injection molding at a molding pressure of 25 to 30 tons.

The second molding step may be maintained for 40 minutes to 60 minutes at a temperature of 1450 ℃ to 1530 ℃ and a pressure of 1200kg / cm ² to 1400kg / cm ² .

The coating step may be coated on the tooth fixing portion of the orthodontic bracket. In addition, the coating step may be heat-sealed glass beads by heat treatment at 700 ℃ to 1200 ℃.

The present invention can provide a ceramic orthodontic ceramic bracket with improved strength while maintaining light transmittance, and when the bracket is used to prevent the breakage of the bracket during orthodontic treatment, and prevents re-operation by breaking the bracket even after orthodontic can do. In addition, the ceramic bracket for orthodontics according to the present invention provides excellent adhesion with the teeth, thereby improving the orthodontic effect.

Figure 1 shows a flow chart for the manufacturing method of the orthodontic bracket according to an embodiment of the present invention.
Figure 2 shows an image of the orthodontic bracket according to an embodiment of the present invention.
Figure 3 shows a cycle of the first heat treatment step according to an embodiment of the present invention.
Figure 4 shows the cycle of the second forming step according to an embodiment of the present invention.
Figure 5 shows the XRD pattern of the molded article prepared according to Example 1 of the present invention. In Figure 5 (a) is a standard MgAl ₂ O ₄ , (b) is It is a molded object of Example 1.
Figure 6 shows an SEM image of the molded article prepared according to Example 1 of the present invention.
FIG. 7 shows optical photographs of brackets coated with glass beads on the bottom of the fixing part according to Example 1 and Comparative Example 3 of the present invention.

Hereinafter, the present invention will be described in more detail.

The present invention provides a ceramic composition of the orthodontic bracket, the composition comprises a high purity alumina, magnesium oxide or precursors and binders thereof. The ceramic composition of the orthodontic bracket may improve the strength of the bracket by suppressing the grain growth of the alumina during the heat treatment process by adding magnesium oxide or a precursor thereof as a grain growth inhibitor to alumina.

The high purity alumina may have a purity of 99.99% or more and an average particle size of 0.3 μm or less. Preferably the average particle size may be 0.15 to 0.3 ㎛.

The magnesium oxide or a precursor thereof is used as a grain growth inhibitor, the precursor is converted to magnesium oxide by heat treatment, it is possible to suppress the grain growth of alumina oxide during the heat treatment. The precursor may be at least one of hydroxides, ammonium, halides, acetates, nitrate compounds, and hydrates of magnesium. The magnesium oxide or a precursor thereof may be included in an amount of 1 to 2% by weight based on the total weight of the alumina oxide, preferably 1 to 1.8% by weight, more preferably 1 to 1.5% by weight. If the content of magnesium oxide or its precursor is less than 1% by weight, the particle growth of alumina may not be inhibited, and the strength may be lowered. If the content of the magnesium oxide or the precursor thereof is more than 2% by weight, magnesium oxide or its precursor may be segregated at the alumina grain boundary to reduce light transmittance. Not desirable

The binder may be included in 30 to 40% by weight, preferably 20 to 25% by weight based on the total weight of the alumina oxide. When the content of the binder is less than 30% by weight, the flowability during the molding is suppressed to cause defects, and when the content of the binder exceeds 40% by weight, the density is lowered during molding, thereby impairing the light transmittance and strength of the final ceramic bracket.

The binder may be one or more of low density polyethylene (LDPE), paraffin wax and stearic acid, preferably a mixture of low density polyethylene, paraffin wax and stearic acid. Low density polyethylene: paraffin wax: stearic acid in the mixture may be included in a ratio (mass ratio) of 6: 3: 1.

The ceramic composition of the orthodontic bracket may further include an additive applicable to the orthodontic bracket, the additive is not particularly limited in the present invention.

The present invention provides a dental orthodontic bracket made of the ceramic composition of the orthodontic bracket. The orthodontic bracket may be configured in a mold structure and form known in the art, and various modifications are possible depending on the purpose of use.

According to an embodiment of the present invention, the tooth fixing bracket may include a wire inserting portion, a self-ligating portion, a tooth fixing portion, and an orthodontic hinge portion ((a) and (c) in FIG. 2). In addition, since the calibration hinge portion can be selectively used according to the calibration purpose, it can be removed from the mold structure ((b) in FIG. 2).

According to one embodiment of the invention, the surface of the tooth fixing bracket may be coated with glass beads, preferably the surface of the tooth fixing portion may be coated with glass beads. The coating of the glass beads may create an embossed roughness on the surface of the bracket to improve adhesion to the teeth and maintain light transmission of the bracket. Preferably, the particle size of the glass beads may be 70 μm to 120 μm.

The present invention provides a method for manufacturing the tooth fixing bracket. The method of manufacturing the tooth fixing bracket is applied to the ceramic composition of the orthodontic bracket according to the present invention, the particle size is reduced by inhibiting the grain growth of the alumina oxide in the manufacturing process of the bracket, the bracket through hot hydrostatic pressure molding It is possible to provide a high-strength bracket while maintaining a light transmittance and aesthetics by increasing the density of the. The manufacturing method includes a manufacturing step of the composite powder, a manufacturing step of the ceramic composition of the orthodontic bracket, the first molding step, the first heat treatment step, the second molding step and the coating step.

Preparation Step of Composite Powder

The manufacturing step of the composite powder is alumina oxide; And magnesium oxide or a precursor thereof to prepare a composite powder. The mixing is performed according to a conventional powder mixing method, more specifically, a ball mill can be used. According to one embodiment of the present invention, the ball mill may use an alumina container and an alumina ball to prevent the light transmittance of the ceramic bracket due to the incorporation of foreign matter. The ball mill time may be carried out for 10 to 15 hours at 90 to 100rpm.

Orthodontic Bracket  Steps to Prepare the Ceramic Composition

In the preparing of the ceramic composition of the orthodontic bracket, a binder is added to the composite powder and kneaded to prepare the composition. The kneading is to prepare a composition by mixing with uniform heating, and the composition is used as feedstock for injection molding in the next molding step. According to one embodiment of the present invention, by adding a binder to the composite powder can be kneaded for 30 minutes to 3 hours at 150 to 200 ℃.

First molding step

In the first molding step, the ceramic composition of the orthodontic bracket is introduced into an injection molding machine and filled in a mold to produce a bracket-shaped molded body. According to one embodiment of the invention, the temperature of the mold is maintained at 40 to 50 ℃, in order to smooth the flow of the composition, 30 tons or less, preferably It can be molded by injection molding at a molding pressure of 25 to 30 tons. If the molding pressure exceeds 30 tons, the molten composition may leak out of the mold during molding of the bracket, which may result in molding failure.

The structure of the mold can be designed according to the structure of the desired bracket, for example, it can be designed according to the size, angle, purpose of use and the like of the tooth. According to one embodiment of the present invention, it can be designed in the shape of the orthodontic bracket having a wire insertion portion, self-ligating portion, tooth fixing portion and orthodontic hinge (Fig. 2).

First heat treatment step

The first heat treatment step is a step of imparting strength of the manufactured compact, and may include a binder removal step and a particle densification step. Referring to FIG. 3, the binder removing step removes the binder while maintaining the bracket molded body at a temperature of 500 ° C. to 600 ° C. for 1 to 8 hours. In the binder removal step, the elevated temperature is within 3 ° C. per minute, preferably 1 ° C. to 3 ° C. per minute. When the elevated temperature exceeds 3 ° C., the binder may cause cracks in the product when the binder is degassed in the fine particle gap due to the rapid elevated temperature.

Referring to Figure 3, the particle densification step is raised to a temperature of 1550 ℃ to 1580 ℃ after the binder removal step, and densified the particles of the molded body while maintaining at the temperature for 30 minutes to 1 hour. In the particle densification step, the elevated temperature is 10 ° C. or more per minute, and preferably 10 ° C. to 15 ° C. per minute to minimize particle growth. If the elevated temperature is less than 10 ° C., the particles may be grown by the low elevated temperature, and low strength may occur even if heat treatment is performed at the same temperature.

2nd molding step

In the second molding step, after the first heat treatment step, the molded body is subjected to hot hydrostatic pressure molding under constant heat and pressure so as to have aesthetics and translucency of the molded body.

The temperature of the hot hydrostatic pressure forming is 50 ° C to 100 ° C lower than the temperature of the particle densification step, preferably 1450 ° C to 1530 ° C, more preferably 1500 ° C to 1530 ° C. If the temperature of the hot hydrostatic molding is higher than the temperature of the particle densification step, the light transmittance of the bracket is lowered, the strength may be lowered due to grain growth. The temperature rise temperature in the hot hydrostatic pressure molding is 20 ℃ to 30 ℃, it is maintained for 40 to 60 minutes at the temperature of the hot hydrostatic pressure molding.

The hot hydrostatic molding is carried out at a pressure of 1200kg / cm ² to 1400kg / cm ² , the pressure can be boosted to 6kg / cm ² to 12kg / cm ² per minute. When the pressure is included in the above range it is possible to maintain the light transmittance while increasing the strength of the bracket.

Coating step

The coating step is coated with a glass bead on the surface of the bracket to create a roughness of the embossed shape on the surface. Coating of the glass beads may be applied to the coating method known in the present invention, in accordance with an embodiment of the present invention, after uniformly spraying the glass beads using a sieve on the bottom surface of the tooth fixing part of the bracket 600 ℃ to 700 It may be coated by heat fusion method heat treatment at ℃. Preferably the particles of the glass beads may be 70 μm to 120 μm.

Hereinafter, the present invention will be described in more detail with reference to examples. However, these examples are for illustrative purposes only, and the scope of the present invention is not limited to these examples.

 Example 1

1 kg of 6-8 mm alumina balls were put into the alumina container which has a volume of 2000 ml, 500 g (0.25 micrometer) and 5 g magnesium chloride hexahydrate, and 1 L of distilled water were added. Next, it was ball milled for 24 hours at 90-100 rpm. Next, 90 g of low density polyethylene was added to 500 g of the ball mill-finished powder, followed by primary stirring at 190 ° C. for 30 minutes. Next, 45 g of paraffin wax and 15 g of stearic acid were added thereto, followed by stirring for 1 hour to prepare a composition.

The bracket composition of Example 1 was put into a mold of an injection machine (sumitmo, 50 ° C., pressure 30 tons) to prepare a bracket molded body by injection molding. Next, the molded body was transferred to an electric furnace, heated to 1 ° C. per minute, heat treated at 600 ° C. for 8 hours, and then heated to 15 ° C. per minute, and heat treated at 1580 ° C. for 1 hour. It cooled to normal temperature, heated up 30 degreeC per minute, it heated up at 10 kg / cm <^2> per minute, and performed hot hydrostatic molding at 1500 degreeC and 1200 kg / cm <^2> for 1 hour. The mold form of the produced molded body is shown in FIG. In addition, the XRD and the scanning electron microscope (SEM) of the molded body were measured and shown in FIGS. 5 and 6.

After spraying the glass beads (Well Trading Co./MS-ML, 2g) uniformly with a sieve on the tooth fixing part of the prepared bracket, put them in an electric furnace, the temperature was raised to 5 ° C. per minute and heat-treated at 670 ° C. for 0.5 hours. The tooth fixing surface of the bracket coated by the thermal fusion method is shown in comparison with Comparative Example 3 prepared by the conventional coating method in FIG.

XRD analysis of the bracket according to Example 1 (a) it can be seen that the spinel phase is also detected in Example 1 (b) of the present invention compared to the standard spinel phase (MgAl ₂ O ₄ ) (Fig. 5).

Photographing the bracket according to Example 1 using a scanning electron microscope (SEM) it can be seen that the average ceramic particle size constituting the bracket within 2μm (Fig. 6).

[Example 2]

A bracket was manufactured in the same manner as in Example 1, except that 7.5 g of magnesium chloride hexahydrate was added.

[Example 3]

A bracket was manufactured in the same manner as in Example 1, except that 10 g of magnesium chloride hexahydrate was added.

Comparative Example 1

A bracket was manufactured in the same manner as in Example 1, except that 15 g of magnesium chloride hexahydrate was added.

Comparative Example 2

The bracket was prepared in the same manner as in Example 1 without the addition of magnesium chloride hexahydrate.

Configuration Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Alumina oxide
(g) 500 500 500 500 500 Magnesium chloride
(g) 5 7.5 10 15 - bookbinder
(g) 150 150 150 150 150

 [Comparative Example 3]

Using a spheroidized alumina instead of glass beads and to a coated and heat treated at 1200 ℃ was prepared except the bracket in the same manner as in Example 1.

 [Comparative Example 4]

The bracket was manufactured in the same manner as in Example 1, except that the bracket was manufactured without a hot hydrostatic pressure forming step.

[Comparative Example 5]

The bracket was manufactured in the same manner as in Example 1 except that the hydrostatic pressure was formed at 1650 ° C.

The physical properties of the prepared brackets were measured as follows.

(1) sintered density

The prepared bracket was dried in a thermostat at 110 ± 5 ° C. for 3 hours, and the weight when the weight was constant was set to dry weight W1 (g). The weight was measured accurately to 0.01 g. The dry weight bracket was immersed in distilled water, boiled for 3 hours or more, cooled to room temperature, and then immersed again in water to measure the weight W2 (g) in water. The weight was measured accurately to 0.01 g. Based on the measured values, using the Archimedes principle, the density was calculated using the following equation.

(2) hardness

Using a micro-Vickers hardness tester MVK-HVL manufactured by MITUTOYO Co., Ltd., a load of 9.8 N was applied, and the hardness of the diamond indentation was measured.

(3) strength

The push-pull gauge was used to hook the wire to the bracket's calibration hinge and to apply a force in the horizontal direction to measure the strength of the bracket when it was cut.

(4) light transmittance

A spectrophotometer was used to illuminate the light source on the bottom of the bracket and to measure the brightness of the light at the bracket body through the detector to compare the light transmittance.

(5) Particle size analysis of the molded body

Particle size was measured by photographing the microstructure of the ceramic constituting the bracket using a scanning electron microscope (SEM).

Configuration Example
One Example 2 Example 3 Comparative Example 1 Comparative Example
2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Sintered Density
(g / cm ³⁾ 3.98 3.96
3.94
3.75
3.80
3.98
3.68
3.98
Hardness (HV) 2040 2010 1980 1920 1950 2040 1950 1980 Strength (kgf) 3.4 3.0 2.8 2.2 2.4 3.4 1.8 2.0 Transmittance (%) 85 83 80 60 70 60 40 88

Looking at Table 2, it can be seen that applying the magnesium chloride hexahydrate according to the present invention, the bracket prepared by hot hydrostatic pressure shows excellent results compared to the comparative example in hardness, strength and light transmittance. In particular, when the magnesium chloride hexahydrate exceeds or does not contain 2% by weight (Comparative Example 1 and Comparative Example 2), it can be confirmed that the light transmittance is sharply reduced. In addition, when the surface of the bracket is coated with the conventional spheroidized alumina, it can be seen that the light transmittance is lower than that of the bracket of the present invention. This is because the use of spherical alumina increases the heat fusion temperature and induces grain growth, compared to the case of surface coating with glass beads.

The present invention can provide a bracket for orthodontics with high strength while showing excellent light transmittance and aesthetics. In addition, by coating the surface of the bracket with glass beads to improve the adhesion to the teeth, compared with the conventional coating using a ceramic oxide, such as spherical alumina, it is possible to lower the thermal fusion temperature, and to prevent the lowering of the light transmittance due to the coating.

Claims (18)

Alumina oxide;
1 to 2 wt% of magnesium oxide or a precursor thereof based on the total weight of the alumina oxide; And
Includes; 30 to 40% by weight of the binder based on the total weight of the alumina oxide;
The precursor is a ceramic of the orthodontic bracket, characterized in that at least one of hydroxide (ammonium), ammonium (halmon), halide (acetate), nitrate compound and hydrate thereof of magnesium Composition.
The method of claim 1,
The ceramic composition of the orthodontic bracket, characterized in that the purity of the alumina oxide is 99.99% or more, the average particle size is 0.3㎛ or less.
The method of claim 1,
The binder is a ceramic composition of the orthodontic bracket, characterized in that at least one of low density polyethylene, paraffin wax and stearic acid.
The method of claim 3,
The binder is a ceramic composition of the orthodontic bracket, characterized in that the mixture consisting of a low density polyethylene: paraffin wax: stearic acid = 6: 3: 1 ratio (mass ratio).
delete In the orthodontic bracket comprising a wire insertion portion, self-ligating portion, tooth fixing portion and orthodontic hinge (hinge),
The bracket is molded from the ceramic composition of claim 1 orthodontic bracket,
Brackets for orthodontics, characterized in that the surface of the tooth fixing portion is coated with glass beads.
The method according to claim 6,
The particle size of the glass bead is orthodontic bracket, characterized in that 70 μm to 120 μm.
Alumina oxide; And magnesium oxide or a precursor thereof;
Preparing a ceramic composition of the orthodontic bracket for mixing the composite powder and the polymer binder;
A first molding step of molding the ceramic composition of the orthodontic bracket to have a bracket shape;
A first heat treatment step of heat-treating the bracket molded body formed after the molding step;
A second molding step of molding the bracket molded body to hot hydrostatic pressure after the heat treatment step; And
After the second forming step comprises a coating step of coating a glass bead on the surface of the bracket molded body,
Preparation of the orthodontic bracket, characterized in that the precursor is at least one of hydroxide (hydroxide), ammonium (ammonium), halide (halide), acetate (acetate), nitrate compound and hydrate thereof of magnesium Way.
9. The method of claim 8,
The purity of the alumina oxide is 99.99% or more, and the average particle size is 0.3㎛ or less manufacturing method of the orthodontic bracket.
9. The method of claim 8,
The ceramic composition of the orthodontic bracket is based on the total weight of the alumina oxide;
1 to 2% by weight magnesium oxide or precursor thereof; And
30 to 40% by weight of the binder; manufacturing method of the orthodontic bracket comprising a.
9. The method of claim 8,
The binder is a low density polyethylene, paraffin wax and stearic acid manufacturing method of the orthodontic bracket, characterized in that at least one of.
9. The method of claim 8,
The binder is a low-density polyethylene: paraffin wax: stearic acid = 6: 3: the manufacturing method of the orthodontic bracket, characterized in that the mixture consisting of a ratio (mass ratio).
9. The method of claim 8,
The heat treatment step is a binder removal step of removing the binder by maintaining the bracket molded body at 500 ℃ to 600 ℃ for 1 to 8 hours; And
And densifying the particles for 30 minutes to 1 hour at 1550 ° C. to 1580 ° C. after the binder removal step.
9. The method of claim 8,
The first molding step is a manufacturing method of the orthodontic bracket, characterized in that for performing injection molding at a molding pressure of 25 to 30 tons.
9. The method of claim 8,
The second molding step is a manufacturing method of the orthodontic bracket, characterized in that maintained for 40 minutes to 60 minutes at a temperature of 1450 ℃ to 1530 ℃ and a pressure of 1200kg / cm ² to 1400kg / cm ² .
16. The method of claim 15,
In the second forming step, the temperature is 1500 ℃ to 1530 ℃ manufacturing method of the orthodontic bracket, characterized in that.
9. The method of claim 8,
The coating step is a manufacturing method of the orthodontic bracket, characterized in that the coating on the tooth fixing portion of the orthodontic bracket.
9. The method of claim 8,
The coating step is a heat treatment at 700 ℃ to 1200 ℃ manufacturing method of the orthodontic bracket, characterized in that the heat-sealed glass beads.

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