JPH0412974B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an orthodontic bracket, and particularly to an orthodontic bracket with excellent aesthetics and enhanced wing strength. (Prior Art and Problems to be Solved by the Invention) In an orthodontic device for correcting misaligned teeth, a bracket is used as a tool for connecting a wire and a band. Brackets are used by being fixed to the tooth surface in order to apply the load caused by bending or pulling the wire to the tooth to be corrected. Traditionally, brackets have been made of metal, but recently they have been made of plastic, ceramic, etc. are also being used. Metal ones have the advantage of being strong and can reliably transmit the orthodontic force of wires, etc.
Ceramic ceramics have good transparency and are aesthetically pleasing, but they are said to have problems with adhesion. Also, while conventional plastic ones are aesthetically pleasing, they have problems in terms of strength. Conventional plastic brackets have drawbacks such as the wing parts being easily damaged, discoloration, and wire slippage. There were various clinical problems, such as the inability to provide a device with an optical axis and grooves, and the inability to provide torque angulation. Currently, the material for plastic brackets that is widely used is polycarbonate, a thermoplastic resin. Polycarbonate has good transparency and excellent impact resistance, and is used as an engineering plastic. However, for orthodontic purposes, it does not function satisfactorily because its hardness is low and its mechanical strength (tensile strength, bending strength, compressive strength) is rather low. Due to its low hardness, its surface is easily scratched by toothbrushes and the like, causing wear and stains (discoloration). In addition, due to insufficient mechanical strength, the wing part is easily damaged as mentioned above, and although it can be used for single type brackets (those with grooves in surface view), it can be used for brackets with various other complex shapes (Siamese type). It is difficult to use it for molds, torque angulation, etc.). (Means for Solving the Problems) As a result of intensive research to solve these problems, the present inventors have made some improvements to the acrylic composite material conventionally used for prosthetics. We have developed the best material for orthodontic brackets. The present invention has been made through the development of this material, namely, an orthodontic bracket characterized by being formed from a polymerized and cured mixture of components a to d below as a bracket material. a polyfunctional methacrylate and/or acrylate: 40 to 90% by weight, b monofunctional methacrylate and/or monofunctional acrylate: 9 to 50% by weight, c filler: 1 to 30% by weight, d polymerization initiator 0.01 to 2% by weight , is. In the present invention, the polyfunctional methacrylates include ethylene glycol methacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, 2 ,2-bis[4-(2
-hydroxy-3-methacryloxypropoxy)
phenyl]propane, 2,2-bis(4-methacryloxyphenyl)propane, 2,2-bis(4
- methacryloxyethoxyphenyl)propane,
Dimethacrylates such as 2,2-bis(4-methacryloxypolyethoxyphenyl)propane and di(methacryloxyethyl)trimethylhexamethylene diurethane; trimethacrylates such as trimethylolpropane trimethacrylate and tetramethylolmethane trimethacrylate , tetramethacrylates such as tetramethylolmethanetetramethacrylate, and hexamethacrylates such as dipentaerythritol hexamethacrylate. Examples of polyfunctional acrylates include 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)propa, 2,2
- Diacrylates such as bis(4-acryloxyethoxyphenyl)propane, 2,2-bis(4-acryloxypolyethoxyphenyl)propane, di(acryloxyethyl)trimethylhexamethylene diurethane, trimethylolpropane Examples include triacrylates such as triacrylate and tetramethylolmethane triacrylate, tetraacrylates such as tetramethylolmethanetetraacrylate, and hexaacrylates such as dipentaerythritol hexaacrylate. Next, as the above monofunctional methacrylate,
Methyl methacrylate, ethyl methacrylate,
Isopropyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate,
Examples include cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, and isobornel methacrylate. Examples of monofunctional acrylates include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, and isobornel acrylate. Examples of the filler include inorganic fillers and organic fillers. Examples of the inorganic filler include fine glass powder, fine quartz powder, fine powder of alumina and other ceramics, and a preferable example is a silica filler whose surface is treated with a silane coupling agent. In addition, as the organic filler, fine particles obtained by polymerizing dimethacrylate, trimethacrylate, tetramethacrylate, hexamethacrylate, diacrylate, triacrylate, tetraacrylate, hexaacrylate, etc. and then pulverizing them, or particles obtained by pearl polymerization. Microscopic particles are preferred. As a polymerization initiator, when carrying out thermal polymerization, commonly used organic peroxides and azobis compounds are used, and when carrying out thermopolymerization, for example, peroxides and tertiary amines are used. It will be done. Moreover, when photopolymerizing, a peroxide and a photosensitizer can be used. As the photosensitizer, those for UV curing such as benzophenones can be used, but those for visible light curing such as camphorquinone are particularly preferred. At this time, it goes without saying that a tertiary amine or the like may be added as a polymerization accelerator. Here, the reason for limiting the range of the amount of each component a to d in the present invention is as follows. a The content of polyfunctional methacrylate and/or acrylate is outside the range of 40 to 90% by weight, and if it is less than 40% by weight, the fracture strength of the bracket wing will decrease and become unsatisfactory, and if it exceeds 90% by weight, This is not preferable because the bracket wing becomes brittle and the breaking strength is reduced. b. Monofunctional methacrylate and/or monofunctional acrylate is out of the range of 9 to 50% by weight, and if it is less than 9% by weight, the bracket material becomes brittle and the fracture strength of the bracket wing decreases,
If it exceeds 50% by weight, the tensile strength of the material decreases and the breaking strength of the wing becomes insufficient. c If the filler content is outside the range of 1 to 30% by weight and is less than 1% by weight, the compressive strength of the material will decrease;
If it exceeds 30% by weight, the tensile strength of the material decreases and the breaking strength of the wing decreases to an unsatisfactory level. d The polymerization initiator is outside the range of 0.01 to 2% by weight,
If it is less than 0.01% by weight, unpolymerized matter will remain in the material, and if it exceeds 2% by weight, the material will become brittle and the breaking strength of the wing will decrease, which is undesirable. Therefore, the above ranges of the amounts of each component of the present invention are preferable. Furthermore, more preferable ranges are a. 50 to 80% by weight of polyfunctional methacrylate and/or acrylate, b. 15 to 45% by weight of monofunctional methacrylate and/or monofunctional acrylate, and c. 1 to 20% by weight of filler.
Weight%, d. The polymerization initiator is comprised of 0.01 to 2% by weight. Next, a method for manufacturing the orthodontic bracket of the present invention will be explained. The orthodontic bracket is formed by machining (cutting, polishing, etc.) the polymerized plastic material.
or a method of polymerizing and curing within a molding frame. Examples of the mold include metal, ceramic, glass, and resin molds, and in the case of thermal polymerization or room temperature polymerization, metal, ceramic, and glass molds can be used. In addition, when forming by photopolymerization, it is preferable to use a mold made of glass, translucent ceramic, or translucent resin. The obtained polymeric resin material according to the present invention is significantly superior to conventional polycarbonate materials in terms of various mechanical properties. In particular, the Brinell hardness is about twice that of polycarbonate, the compressive strength is about five times as high, and the tensile strength and bending strength are also 30 to 40% higher. The breaking strength, which will be explained later, has increased by 30-50%. Because of these excellent mechanical properties, the orthodontic bracket of the present invention is of unprecedented quality. With polycarbonate brackets, the hardness is not high enough, so the ligation wire gets wedged into the surface of the bracket during straightening work, making it difficult for the wire to slide.However, the bracket of the present invention prevents the wire from getting wedged into the surface. Since there is no slippage, smooth gliding is guaranteed. Furthermore, since the surface is less likely to be scratched by a toothbrush, no surface stains occur. Since the bracket can sufficiently withstand various stress loads during installation, it will not be damaged or destroyed even after long-term use. (Examples) Next, the present invention will be explained in detail using some examples and comparative examples. Example 1: 38 parts by weight of methyl methacrylate, 52 parts by weight of 2,2-bis(4-methacryloxypolyethoxyphenyl)propane, 10 parts by weight of Aerosil R927 (fine silica powder manufactured by Nippon Aerosil Co., Ltd.), 0.3 parts by weight of benzoyl peroxide. After thoroughly stirring a mixture consisting of parts by weight, vacuum defoaming was performed to completely remove air bubbles in the mixture. The mixture is poured into a cavity 4 formed inside the upper mold 1 and side mold 2 of the stainless steel mold shown in FIG.
After pouring into the mold and pushing the lower mold 3 in, the mold is clamped from above and below by square-shaped plate springs 5 and 5'.
Fixed. After holding it in a constant temperature bath at 80° C. for 2 hours to polymerize and harden the contents of the mold, the obtained molded product bracket was taken out from the mold. The mold shown in FIG. 1 is a split mold and consists of an upper mold 1, side molds 2, and lower mold 3, and is provided with a cavity 4 in which a bracket is formed. The extracted Siamese type bracket had a wing breakage strength of 10.5 kg, was translucent, and had excellent aesthetics. The fracture strength of the wing was tested by holding the entire wing in a steel holder as shown in Figure 2 (a box-shaped holder 6 was provided at the bottom, and a cubic block 8 was inserted into the holder). , and a grab-like clamping claw 7 is disposed above.The bottom of the bracket is attached to a cubic block 8 with strong adhesive, and the bracket is vertically mounted using an Instron universal testing machine. This was done by pulling. The breaking strength of the wing was defined as the load at which the wing broke or deformed. Example 2: 45 parts by weight of cyclohexylmethyl methacrylate, 40 parts by weight of 2,2-bis(P-2'-hydroxy-3'-methacryloxypropoxyphenyl)propane, 4,8-di(methacryloxymethylene)tricyclo[ 5,2,1,0 ^2,6 ] Decane 10 parts by weight,
After thoroughly stirring a mixture consisting of 5 parts by weight of Aerosil R927 (manufactured by Nippon Aerosil Co., Ltd.) and 0.5 parts by weight of lauroyl peroxide, a bracket was manufactured in the same manner as in Example 1. The fracture strength of the resulting Siamese-type bracket wing was tested using the same testing machine as in Example 1, and was 11.1 kg, indicating that it was translucent and had excellent aesthetics. Ta. Example 3: 5 parts by weight of fine powder of trimethylolpropane trimethyl methacrylate polymer, 40 parts by weight of methyl methacrylate, 10 parts by weight of KAYARAD-DPCA60 (pentaerythritol hexamethacrylate type polyfunctional acrylate manufactured by Nippon Kayaku), 2,2- After thoroughly stirring a mixture consisting of 45 parts by weight of bis(4-methacryloxydiethoxyphenyl)propane, 0.5 parts by weight of benzoyl peroxide, and 0.2 parts by weight of camphorquinone, vacuum defoaming was performed to remove the air in the mixture. Air bubbles were completely removed. The mixture was then mixed with a compound of the same type as shown in FIG.
Pour it into a transparent polypropylene mold, clamp and fix the mold from the top and bottom with cross-sectional springs, and then place it on the turntable of a visible light irradiator (made by Morita Tokyo Manufacturing Co., Ltd.) for 15 minutes. Light irradiation was performed. The fracture strength of the wing of the obtained Siamese type bracket was 11.7 kg, and it was also excellent in aesthetics due to its translucence. Comparative Example: A polycarbonate bracket having the same shape as in Example 1 was produced by injection molding, and the breaking strength of the wing was measured. When the wing of the polycarbonate Siamese type bracket was subjected to a tensile load of 4.2 kg using the testing apparatus used in Example 1, it was significantly deformed at 4.2 kg, making it unusable clinically. Table 1 shows the mechanical properties of the bracket materials provided in each of the above Examples and Comparative Examples. As is clear from the results shown in the table, the bracket material of the present invention has hardness, tensile strength, bending strength,
It can be seen that the compressive strength is significantly superior to the polycarbonate bracket material of the comparative example.

[Table] *However, the units of tensile strength, bending strength, and compressive strength are MPa.
(Effect of the invention) As mentioned above, the orthodontic bracket of the present invention has the following features:
Compared to conventional plastic (polycarbonate) brackets, they have considerably greater breaking strength, so they can be used for Siamese type or torque brackets for front teeth, which could not be manufactured due to their low mechanical strength. It is now possible to manufacture and provide . In addition, since it has excellent mechanical properties such as tensile strength, bending strength, and compressive strength, the size of the bracket can be made small. This has the advantage of significantly reducing the sense of discomfort. In addition, since it is translucent, it has good aesthetics and is also highly hard, so the orthodontic wire slides easily and the surface is not stained by damage caused by toothbrushes or the like. Therefore, there is no need to worry about not only initial strength but also breakage or surface staining due to long-term wearing.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a mold for manufacturing an orthodontic bracket according to an embodiment of the present invention, and Fig. 2 is a holder for measuring the breaking strength of the wing of an orthodontic bracket and the held bracket. shows a side view. 1...Top mold, 2...Side mold, 3...Lower mold, 4...
Gap portion, 5...plate spring, 6...presser, 7...
Clamping claw, 8...Block letters.

Claims (1)

[Scope of Claims] 1. A bracket for bridge repair, characterized in that it is formed by molding a polymerized and cured mixture of components a to d below as a bracket material. a polyfunctional methacrylate and/or acrylate: 40 to 90% by weight, b monofunctional methacrylate and/or monofunctional acrylate: 9 to 50% by weight, c filler: 1 to 30% by weight, d polymerization initiator 0.01 to 2% by weight . 2. The orthodontic bracket according to claim 1, wherein the filler is silica fine particles whose surface has been treated with a silane coupling agent. 3. The orthodontic bracket according to claim 1, wherein the filler is fine particles of crosslinked resin. 4. The orthodontic bracket according to any one of claims 1 to 3, wherein the polymerization initiator comprises a peroxide and a tertiary amine. 5. The orthodontic bracket according to any one of claims 1 to 3, wherein the polymerization initiator comprises a peroxide and a photosensitizer.