JP2611346B2 - Orthodontic bracket and method of manufacturing the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an orthodontic bracket, and more particularly to an orthodontic bracket having excellent aesthetics, high strength and strong adhesion to teeth and its manufacture. About the method.

(Prior Art) In an orthodontic device for correcting an incorrect dentition, a bracket is used as a tool for connecting a wire and a band.

Brackets are used by fixing them to the tooth surface in order to apply the load caused by bending or pulling of the wire to the teeth to be corrected.However, metal brackets are often used in the past, and plastics, ceramics, etc. have recently been used. Are also being used.

Metallic materials have the advantage of excellent strength and the ability to reliably transmit the correction force of wires etc., but they have problems with aesthetics, while ceramics have good transparency and good aesthetics, but have good adhesive properties. Is said to have a problem.

Further, plastics have good aesthetics and adhesiveness and are widely used in edgewise methods and the like, but have problems in strength.

The problems with plastic brackets are that the wings are easily damaged, discolored, wire slips poorly, There is no siamese type that can be used for the motor, no torque angulation can be added, etc.

Currently, a widely used plastic bracket material is a thermoplastic resin, polycarbonate. Polycarbonate is an engineering plastic with good transparency and excellent impact resistance, but has a soft surface and mechanical strength (tensile strength, flexural strength, compressive strength)
However, since it is slightly small, it does not always exhibit a sufficient function as a correction device. Further, since the surface is soft, the surface is easily scratched by a toothbrush or the like, which causes abrasion stain (discoloration). Also, due to insufficient mechanical strength,
Not only is the wing easily damaged, but it is difficult to adopt various bracket shapes (siamese, torque undulation) required for orthodontic treatment.

Therefore, the present inventor has conducted intensive studies and produced a conventional orthodontic bracket using a so-called dental composite resin composition used for restoring a cavity of a tooth as a plastic bracket material. Obtained a bracket for orthodontics that has much better mechanical strength than that of Japanese Patent Application No. 62-2654.
No. 34 proposed.

However, the composite resin does not always have sufficient adhesiveness with the adhesive for the orthodontic bracket, and thus may be peeled off from the tooth surface when receiving an excessive fastening force by the orthodontic wire.

In addition, as the adhesive for orthodontic bracket used at the time of orthodontics, a mixed composition of methyl methacrylate monomer, 4-methacryloyloxyethyl trimellitic anhydride, polymethyl methacrylate powder, and tri-n-butylborane (TBB) (Eg "Super Bond"
(Trade name, manufactured by Sun Medical Co., Ltd.) and a mixed composition (redox system type) of a methyl methacrylate monomer, BisGMA, BPO, and a tertiary amine.

(Means for Solving the Problems) The inventors of the present invention have conducted intensive studies to solve such problems, and as a result, a dentist having both aesthetics and mechanical strength at the same time, and having improved adhesion to teeth. The bracket for orthodontics was completed.

That is, the present invention provides: (1) a composite resin A comprising a cured product of a mixture of the following (a) to (d): (a) polyfunctional methacrylate and / or polyfunctional acrylate: 40 to 80% by weight (b) monofunctional Methacrylate and / or monofunctional acrylate: 9 to 50% by weight (c) Filler: 5 to 49% by weight (d) Polymerization initiator: 0.01 to 2% by weight e) to (g) a composite resin B thin layer comprising a polymerized cured product of the mixture, (e) polyfunctional methacrylate: 5 to 24% by weight (f) monofunctional methacrylate: 0 to 24% by weight (g) silica filler: 50 (H) polymerization initiator: 0.01 to 1% by weight, and a composite resin A on the base surface
And an orthodontic bracket characterized in that the composite resin B and the thin composite resin B are mixed with each other at the boundary between them, and (2) the following (a) to (d) A composite resin A paste comprising a mixture, (a) polyfunctional methacrylate and / or polyfunctional acrylate: 40 to 80% by weight (b) monofunctional methacrylate and / or monofunctional acrylate: 9 to 50% by weight (c) filler: 5 (D) polymerization initiator: 0.01 to 2% by weight, and then a composite resin B comprising the following (e) to (g) is applied to the base forming surface of the composite resin A.
Paste (e) Multifunctional methacrylate: 5 to 24% by weight (f) Monofunctional methacrylate: 0 to 24% by weight (g) Silica filler: 50 to 90% by weight (h) Polymerization initiator: 0.01 to 1% by weight A method for producing an orthodontic bracket, comprising laminating layers and polymerizing and curing these layers.

In the present invention, the main body of the orthodontic bracket is formed of a dental composite resin, and a thin layer of a composite resin B having adhesiveness to a dental adhesive is laminated on a base surface of the bracket. The reason for this is that the composite resin constitutes the bracket main body to provide excellent mechanical strength and aesthetics, and the composite resin B thin layer is formed on the base surface to provide an adhesive for the orthodontic bracket. This is for improving the adhesiveness with the adhesive.

In the present invention, it is preferable in terms of strength that the laminating interface between the composite resin B and the composite resin A be in a state where both are mixed at the time of manufacturing. It is preferable to polymerize and cure by contacting with a dense substance or a viscous substance-viscous substance contact state.

The thickness of the composite resin B thin layer may be about 0.1 mm.

Such a composite resin B is hardly compatible with a dental adhesive as it is, but when it is treated with a silane coupling agent, it becomes firmly bonded to the dental adhesive. Therefore, the bonding strength between the bracket of the present invention and the tooth is sufficiently high. It can contribute to the enhancement.

The composition of the bracket material and the composite resin B thin layer in the present invention is preferably as follows.

That is, the composite resin A of the orthodontic bracket main body is made of a polymer cured product of the following mixture of (a) to (d): (a) polyfunctional methacrylate and / or polyfunctional acrylate: 40 to 80% by weight (b ) Monofunctional methacrylate and / or monofunctional acrylate: 9 to 50% by weight (c) Filler: 5 to 49% by weight (d) Polymerization initiator: 0.01 to 2% by weight And laminated on the base surface of the orthodontic bracket The composite resin B thin layer to be used has the following (e) to
(G) a polymer cured product of the mixture, (e) polyfunctional methacrylate: 5 to 24% by weight (f) monofunctional methacrylate: 0 to 24% by weight (g) silica filler: 50 to 90% by weight (h) polymerization initiator : 0.01 to 1% by weight, and the composite resin A on the base surface and the composite resin B on the thin layer are mixed with each other at their boundary.

According to the research of the present inventor, when manufacturing a bracket having the above composition, a method of manufacturing by irradiating visible light is very advantageous.
It is preferable that the composite resin B paste is of a photopolymerization type and the polymerization and curing are performed by light irradiation.

In the above, the polyfunctional methacrylate according to the present invention includes ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, and 1,3-butanediol dimethacrylate. Methacrylate, 2,2-bis [4- (2-hydroxy-3-methacryloxypropoxy) phenyl] propane, 2,2-bis (4-methacryloxyphenyl) propane, 2,2-bis (4-methacryloxyethoxy) Dimethacrylates such as phenyl) propane, 2,2-bis (4-methacryloxypolyethoxy) propane, di (methacryloxyethyl) trimethylhexamethylene diurethane, trimethylolpropane trimethacrylate, tetramethylolmethyl Trimethacrylate such as emissions trimethacrylate, tetramethacrylate such as tetramethylolmethane Te trimethacrylate, can be mentioned hexamethylene methacrylate such as dipentaerythritol hexa methacrylate.

Further, as the polyfunctional acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,3-butanediol diacrylate, 2,2 -Bis [4- (2-hydroxy-3-acryloxypropoxy) phenyl] propane, 2,2-bis (4-acryloxyphenyl) propane, 2,2-bis (4-acryloxyethoxyphenyl) propane, 2 , 2
Diacrylates such as -bis (4-acryloxypolyethoxyphenyl) propane and di (acryloxyethyl) trimethylhexamethylene diurethane; triacrylates such as trimethylolpropane triacrylate and tetramethylolmethane triacrylate; tetramethylolmethane Examples thereof include tetraacrylates such as tetraacrylate and hexaacrylates such as dipentaerythritol hexaacrylate.

Examples of the monofunctional acrylate according to the present invention include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, and isobornel methacrylate.

Examples of the monofunctional acrylate include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, isobornel acrylate, trimethylsilylpropyl acrylate, and tris-trimethylsiloxa. Nylsilyl acrylate, trifluoromethyl acrylate and the like can be mentioned.

As fillers that can be used, there are two kinds of inorganic fillers and organic fillers. As the inorganic filler, a silica filler whose surface has been treated with a silane coupling agent is suitable. Further, as the organic filler, fine particles obtained by polymerizing dimethacrylate, trimethacrylate, tetramethacrylate, hexamethacrylate, diacrylate, triacrylate, tetraacrylate, hexaacrylate, or the like and then finely pulverizing them, or pearl-polymerized fine particles are suitable.

The polymerization initiator may be an organic peroxide or an azobis compound which is generally used when performing heat polymerization, or a combination of a peroxide and a tertiary amine when performing room temperature polymerization. it can.

In the case of photopolymerization, a combination of a peroxide and a photosensitizer or a combination of a photosensitizer and a reducing agent can be used. As the photosensitizer, an ultraviolet curable type such as benzophenones can be used, but particularly preferably,
Visible light-curable types comprising a combination of camphorquinone and a tertiary amine can be mentioned.

Here, the reasons for limiting the ranges of the respective components (a) to (d) will be described.

(A) When the amount of the polyfunctional methacrylate and / or the polyfunctional acrylate is out of the range of 40 to 80% by weight, and if the amount is less than 40% by weight, the breaking strength of the bracket wing is lowered and becomes unsatisfactory. %, The bracket wing becomes brittle and the breaking strength is lowered, and the gloss of the bracket surface is lost.

(B) The monofunctional methacrylate and / or monofunctional acrylate is out of the range of 9 to 50% by weight, less than 9% by weight of the bracket material becomes brittle, the breaking strength of the bracket wing is reduced, and 50% by weight is reduced. If it exceeds, the tensile strength of the material becomes low, and the breaking strength of the wing becomes insufficient.

(C) 5% by weight of the filler is out of the range of 5 to 49% by weight
If the amount is less than the above, the compressive strength is reduced. If the amount exceeds 49% by weight, the tensile strength of the material is reduced, and the breaking strength of the wing is reduced to an unsatisfactory level.

(D) The polymerization initiator is out of the range of 0.01 to 2% by weight,
If the amount is less than 2% by weight, unpolymerized material remains in the material, and if it exceeds 2% by weight, the material becomes brittle, and the breaking strength of the wing decreases, which is not preferable.

The component range of the composite resin B thin layer to be laminated on the bracket base is as follows: (e) The polyfunctional methacrylate is out of the range of 5 to 24% by weight, and if less than 5% by weight, the strength of the synthetic resin thin layer becomes low. If the content exceeds 24% by weight, the adhesiveness decreases.

(F) When the monofunctional methacrylate is out of the range of 0 to 24% by weight and exceeds 24% by weight, polymerization shrinkage becomes large.
Wrinkles are formed in the thin layer, and the adhesive strength is reduced.

(G) The silica filler is out of the range of 50 to 90% by weight, and if it is less than 50% by weight, the adhesiveness is reduced. If it exceeds 90% by weight, the production of a base-based kneaded product cannot be performed.

(H) when the polymerization initiator is out of the range of 0.01 to 1% by weight,
If the amount is less than this, polymerization failure occurs, and if it exceeds 1% by weight, the polymerization is too fast to foam and the thin layer becomes inhomogeneous.

 Therefore, each of the above component ranges is preferable.

Furthermore, a more preferable range is the bracket body.
(A) polyfunctional methacrylate and / or polyfunctional acrylate is 50 to 80% by weight, (b) monofunctional methacrylate and / or monofunctional acrylate is 15 to 45% by weight, (c) filler is 7 to 20% by weight, d) The polymerization initiator is composed of 0.01 to 2% by weight, and in the composite resin B thin layer laminated on the bracket base surface, (e) 5 to 20% by weight of polyfunctional methacrylate, (f) monofunctional methacrylate 5 to 20% by weight, (g) 60 to 85% by weight of a silica filler, and (h) 0.01 to 1% by weight of a polymerization initiator.

Examples of the method for molding the bracket body of the present invention include a method of processing (cutting, polishing, etc.) a polymerized plastic material, and a method of polymerizing and curing a raw material mixture such as a monomer and a prepolymer in a molding mold. However, the latter method of polymerizing and curing in a molding die frame is preferable in that the bracket body and the composite resin B thin layer can be molded simultaneously.

Examples of the molding mold that can be used in the present invention include metal, ceramic, glass, and resin. When performing heat polymerization or room temperature polymerization, a metal, ceramic, or glass mold can be used. When performing photopolymerization, a glass, resin, or translucent ceramic mold can be used.

(Examples) Next, the present invention will be described in detail with some examples and comparative examples.

Example 1: A paste (paste for bracket body constitution) 18 parts by weight of methyl methacrylate, 52 parts by weight of 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, 10 parts by weight of Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.) After thoroughly stirring a mixture of 20 parts by weight of glass powder, 0.3 parts by weight of benzoyl peroxide and 0.3 parts by weight of N, N-dimethyl-p-toluidine, the mixture was subjected to vacuum degassing to completely remove bubbles in the mixture. The paste was used.

B paste (paste for forming a composite resin thin layer) Methyl methacrylate 2 parts by weight 2,2-bis (p-2'-hydroxy-3-methacryloxypropoxyphenylpropane) 13 parts by weight Glass powder 85 parts by weight Camphorquinone 0.3 parts by weight After sufficiently stirring the mixture of 0.3 parts by weight or more of benzoyl peroxide, the mixture was subjected to vacuum degassing to completely remove bubbles in the mixture to obtain a B paste.

As shown in FIG. 1, A is first introduced into a gap 6 formed inside a lower mold 3 and a side mold 4 of a split mold made of polypropylene.
After supplying a sufficient amount of paste to constitute the bracket main body, and then press-fitting a small amount of B paste onto the upper part, the upper mold 5 is inserted, and both molds are tightened from above and below with a spring 7 and pressurized. It was placed in a visible light irradiator α-light (manufactured by Morita Tokyo Seisakusho), and the A and B pastes in the mold were irradiated with light for 10 minutes.

The breaking strength of the wing of the obtained bracket (see FIG. 2) was measured as follows.

First, a porcelain liner M (Dental silane coupling agent manufactured by Sun Medical Co., Ltd.) is applied to the base surface of the bracket 1, and then, as shown in FIG. 3, the bracket 1 is attached with a super bond 11 (adhesive manufactured by Sun Medical Co., Ltd.). ,
The resin 13 is adhered to the surface of the enamel part of the bovine tooth 12 in which the base is embedded, attached to the steel holder 8, and the wing part is pulled from above with the grab-like holding claw 9 and pulled. The load when the wing was broken or deformed was measured by an Instron universal testing machine.

As a result of the measurement, the breaking strength was 14.2 kg, and there was no peeling of the bonded surface.

 In addition, it was excellent in aesthetics because of the similar color to the teeth.

Example 2: A paste (paste for bracket body composition) Methyl methacrylate 18 parts by weight, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane 52 parts by weight, Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.) 20 parts by weight, Trimethylolpropane trimethacrylate 10 parts by weight, camphorquinone 0.1 parts by weight, henzoyl peroxide 0.3 parts by weight After sufficiently stirring the above mixture, vacuum degassing is performed to completely remove bubbles in the mixture, and paste A did.

B paste (paste for forming a synthetic resin thin layer) Di (methacryloxyethyl) trimethylhexanediurethane 35 parts by weight Triethylene glycol dimethacrylate 10 parts by weight Quartz powder 55 parts by weight, camphorquinone 0.3 parts by weight N, N-dimethyl-p -Toluidine 0.3 part by weight After sufficiently stirring the above mixture, the mixture was subjected to vacuum degassing to completely remove air bubbles in the mixture to obtain a B paste.

As shown in FIG. 1, A is first introduced into a gap 6 formed inside a lower mold 3 and a side mold 4 of a split mold made of polypropylene.
The paste is supplied in a sufficient amount to constitute the bracket body, then the B paste is press-fitted in a thin layer amount thereon, the upper mold 5 is inserted, and both molds are tightened from above and below with a spring 7 and pressurized. It was placed in a visible light irradiator α-light (manufactured by Morita Tokyo Seisakusho), and the A and B pastes in the mold were irradiated with light for 10 minutes.

The breaking strength of the wing of the obtained bracket (see FIG. 2) was measured as follows.

After applying a porcelain liner M (Dental silane coupling agent, manufactured by Sun Medical Co., Ltd.) to the base surface of the bracket 1, as shown in FIG. 3, the bracket 1 is attached with a super bond 11 (adhesive manufactured by Sun Medical Co., Ltd.). resin
At 13 the base is adhered to the surface of the enamel part of the buried tooth 12, which is attached to a steel holder 8, and the wing part is hooked and pulled by a grab-like holding claw 9 from above. The load when the wing was broken or deformed was measured by an Instron universal testing machine.

As a result of the measurement, the breaking strength was 14.2 kg, and there was no peeling of the bonded surface.

 In addition, it was excellent in aesthetics because of the similar color to the teeth.

Comparative Example 1: This is one in which a thin layer made of B paste is not formed on the bracket main body, that is, it corresponds to only the bracket main body in Example 1.

As shown in FIG. 1, a sufficient amount of A paste is press-fitted into the gap 6 formed inside the lower mold 3 and the side mold 4 of the polypropylene split mold to constitute the bracket body, and then the upper mold Then, both molds are tightened with springs 7 from above and below and pressurized, and then put into a visible light irradiator α-light (manufactured by Morita Tokyo Seisakusho), and the A and B pastes in the molds are Light irradiation was performed for minutes. The obtained bracket was adhered to the enamel surface of bovine teeth in the same manner as in Example 1, and the breaking strength of the bracket was measured. As a result, this fracture strength is 1
It was 3.4 kg.

Comparative Example 2: A polycarbonate bracket having a uniform composition having the same shape as the gap portion 4 shown in FIG. 2 was produced by an injection molding method, and adhered to the enamel surface of the bovine tooth in the same manner as in Example 1. Was measured for breaking strength. As a result, the wing of the polycarbonate bracket had a breaking strength of 4.2 kg and was significantly deformed, and could not be used clinically.

Comparative Example 3: After a commercially available ceramic bracket (manufactured by Unitech) was adhered to the bovine tooth enamel surface in the same manner as in Example 1, the breaking strength of the bracket wing was measured. More peeled off.

From the above, since the bracket of the present invention has high mechanical strength and high adhesive strength with the teeth, the breaking strength of the bracket wing can be three times that of the conventional examples of Comparative Examples 2 and 3. I understand.

Furthermore, as shown in Table 1 below, the bracket material of the present invention is significantly superior in hardness, tensile strength, bending strength and compressive strength to the polycarbonate bracket material of the comparative example. understood.

Furthermore, it can be seen from the test results shown below that the orthodontic bracket according to the present invention is sufficiently satisfactory in improving the adhesive strength to teeth. That is,
The compressive shear bond strength of the obtained brackets of the examples and comparative examples was measured as follows.

As shown in FIG. 4, a porcelain liner M (a silane coupling agent manufactured by Sun Medical Co., Ltd.) is applied to the base surface of the bracket 1, and then a super bond 11 (a dental adhesive manufactured by Sun Medical Co., Ltd.) is applied to the base surface of the bracket 1. )
Is applied to the surface of the enamel part of the bovine tooth 12 whose base is embedded with an acrylic resin 13, and the compressive stress in the direction of the arrow by the pressing piece 14 is applied to the bracket body 1 by an Instron universal testing machine. Then, the load when the base of the bracket and the enamel of the bovine tooth were peeled was measured to determine the compression shear adhesive strength.

From this result, it can be understood that the bracket of the present example is particularly excellent in compressive shear adhesive strength as an index of its adhesiveness.

Therefore, the orthodontic bracket of the present invention does not peel off from the tooth surface even under the strong tightening force of the wire during orthodontics.

(Effects of the Invention) As described in the embodiments and the like, the orthodontic bracket provided by the present invention has a breaking strength several times larger than that of the conventional one in the wing portion, and has the same strength as the tooth. Has a sufficiently satisfactory adhesive strength, and has a milky white translucent color and has excellent aesthetics.

Therefore, conventional products could not be manufactured due to low mechanical strength. Siamese type and with torque can also be manufactured, and there is no danger of peeling off from the tooth surface even if an excessive tightening force is applied by wires during orthodontics.

In addition, since the mechanical properties such as tensile strength, bending strength, and compressive strength are excellent, the size of the bracket can be made small.
The discomfort in the patient's mouth is significantly reduced.

Further, since the surface hardness is significantly larger than that of the conventional product, no damage or dirt is caused by a toothbrush or the like.

Not only the initial strength but also the risk of breaking and surface dirt due to wearing for a long time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a molding form of an orthodontic bracket according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the orthodontic bracket, and FIG. 3 is a breaking strength of a wing of the orthodontic bracket. FIG. 4 is an explanatory view of a method of measuring the compression shear strength of the bracket, and FIG. 4 is an explanatory view of a method of measuring the compressive shear adhesive strength of the bracket. 1: Bracket body, 2: Bracket base, 3: Lower type, 4: Side type,
5: Upper die, 6: Void, 7: Spring, 8: Holder, 9: Nail, 11: Adhesive, 12: Bovine, 13: Resin,

Claims (3)

(57) [Claims] 1. A composite resin A comprising a cured product of a mixture of the following (a) to (d): (a) polyfunctional methacrylate and / or polyfunctional acrylate: 40 to 80% by weight (b) monofunctional methacrylate and / or Alternatively, monofunctional acrylate: 9 to 50% by weight (c) Filler: 5 to 49% by weight (d) Polymerization initiator: 0.01 to 2% by weight On the base surface of the orthodontic bracket composed of: (G) a composite resin B thin layer comprising a polymerized cured product of the mixture, (e) polyfunctional methacrylate: 5 to 24% by weight (f) monofunctional methacrylate: 0 to 24% by weight (g) silica filler: 50 to 90% by weight % (H) polymerization initiator: 0.01 to 1% by weight, and the composite resin A on the base surface
And the thin composite resin B are mixed with each other at a boundary portion thereof. 2. A composite resin A paste comprising a mixture of the following (a) to (d) in a mold: (a) polyfunctional methacrylate and / or polyfunctional acrylate: 40 to 80% by weight (b) monofunctional Methacrylate and / or monofunctional acrylate: 9 to 50% by weight (c) Filler: 5 to 80% by weight (d) Polymerization initiator: 0.01 to 2% by weight After supply, the base forming surface of the composite resin A, Composite resin B consisting of (e) to (g) below
Paste (e) Multifunctional methacrylate: 5 to 24% by weight (f) Monofunctional methacrylate: 0 to 24% by weight (g) Silica filler: 50 to 90% by weight (h) Polymerization initiator: 0.01 to 1% by weight A method for producing an orthodontic bracket, comprising laminating layers and polymerizing and curing these layers. 3. The method for producing an orthodontic bracket according to claim 2, wherein the composite resin is of a photopolymerization type, and the polymerization curing is performed by light irradiation.