WO2012020810A1

WO2012020810A1 - Polyamide orthodontic bracket

Info

Publication number: WO2012020810A1
Application number: PCT/JP2011/068312
Authority: WO
Inventors: 博昭宮地
Original assignee: デンツプライ三金株式会社
Priority date: 2010-08-12
Filing date: 2011-08-10
Publication date: 2012-02-16
Also published as: JPWO2012020810A1; JP3195713U

Abstract

The present invention provides a synthetic resin bracket body (2) with improved transparency, aesthetic properties, abrasion resistance, scratch resistance, and chemical resistance. A polyamide is used as the raw material for the bracket body (2), which is formed by injection molding. A metal groove member (8) for guiding or fixing an arch wire (11) is embedded into the center of the polyamide bracket body (2) by insert molding. The polyamide is a transparent member that allows light to pass through and has a structural formula (formula 1). This polyamide has little discoloration by food, etc., and is highly transparent.

Description

Polyamide orthodontic bracket

The present invention relates to an orthodontic bracket made of polyamide. More specifically, the present invention relates to a polyamide orthodontic bracket which is made of polyamide for a bracket body used for orthodontic treatment by adhering to a tooth and has improved aesthetics and use effect.

It is well known to use orthodontic members such as brackets, buccal tubes, and bands as treatments to correct dentitions with poor alignment. This orthodontic member is directly bonded to the tooth, and gives the mechanical tension force of the wire attached to this bracket or buccal tube, that is, restoring force such as pressing, pulling back, twisting, etc. to the tooth, gradually positioning the tooth position. It is a method of orthodontics that changes.

Generally, the bracket has a groove for slidably or holding the archwire in the center of the bracket body, and wings are formed on both sleeves of the bracket body. The archwire in the groove is held and fixed via the wings by various ligating means, and the dentition is corrected over a long period of time using the elastic force of the archwire. Among such brackets, metal brackets are conventionally used frequently. This metal bracket has strength and has an advantage that the bracket can be made into a small shape.

As the metal material, a material that does not rust, such as stainless steel, nickel chrome alloy, titanium alloy or the like, is used, but the metal material is inferior in aesthetics. Something other than metal is also used, and the ceramic bracket is excellent in aesthetics, but the material is harder than the teeth, so the point is that the teeth are damaged. Plastic brackets have been developed to improve aesthetics and can be manufactured by injection molding, so that productivity is good and many types are used including transparent and translucent.

However, this plastic bracket has the disadvantage that its mechanical strength is weak and its durability is inferior, but it has the advantage of being aesthetic, economical and easy to manufacture. As other materials, ceramic materials such as alumina and zirconia are also used. The orthodontic method is to fix the bracket body to the tooth surface with an adhesive, place it through the archwire across the groove of multiple brackets, apply the external force as described above by the restoring force of this archwire, It is corrected by changing.

In recent years, brackets with higher translucency have been favored in that the brackets are inconspicuous. For this reason, there is a demand for a bracket with good light transmittance and excellent aesthetics. As the material for the bracket, acrylic resin (PMMA) may be used because of its good light transmission, but it is considered unsuitable because it has low toughness and is easily chipped, and is rarely used at present. Moreover, although the material of a bracket contains fillers, such as glass fiber, what comprises synthetic resins, such as a polyamide-type resin, is well-known (for example, refer patent document 1).

However, since these known synthetic resin materials are mixed with a filler, the light transmittance is changed for this reason, and the aesthetics are not necessarily improved after a desired transmittance is ensured. In addition, since the filler is contained, the bracket surface becomes microscopically rough, or becomes roughened due to glass filler falling off after long-term use, and adhesion of plaque, dirt, etc. is observed on the surface in this state. Or the discoloration and coloring by the capillary phenomenon to the gap between the filler and the resin may be seen, and the aesthetics are lost.

The above-mentioned publicly known document does not describe specific characteristics etc. for the bracket characteristics by using polyamide. Even if brackets are manufactured with plastics of general conventional materials, they have satisfactory characteristics that are necessary as brackets in terms of strength and adhesion to the tooth surface when mounting the archwire when viewed as a bracket configuration. Is not obtained. In addition, the desired transparency, abrasion resistance, scratch resistance, and chemical resistance have not been obtained.

On the other hand, the present applicant has proposed a bracket having a polycarbonate main body in which a stainless steel groove member for guiding or fixing an archwire is embedded (see, for example, Patent Document 2). Since the groove member made of stainless steel is embedded in the synthetic resin body made of polycarbonate, the groove member which is a metal member will not be detached from the bracket body, but the metal and the resin are strongly fixed to each other. preferable.

For this reason, in order to strengthen this fixation, this bracket is manufactured by inserting a groove member made of stainless steel into an injection mold and injecting polycarbonate. The groove member is a portion where the archwire is guided and directly contacts. For this reason, even if the orthodontic force of the metal arch wire is added along with the orthodontics, it must be resistant to wear and the like. Since the archwire and the groove member are brought into contact with each other and are relatively moved, only the archwire guide portion of the bracket body is made of metal so as to enhance its wear resistance.

っても Even if the bracket body is polycarbonate, it is a bracket with a certain effect, but due to the influence of the filler, it is difficult to lack aesthetics. Moreover, the polycarbonate generally used is a trace amount, but contains environmental hormones in the raw material, and when used as a bracket, there is a safety problem and there is a difficulty in this point as well, which is not preferable. . On the other hand, in general engineering resins, which are general thermoplastic resins, polycarbonate (PC) is an amorphous resin and polyamide (PA) is known as a crystalline resin.

Among them, polyamide (PA) has excellent transparency, wear resistance and scratch resistance, and has no advantage of containing environmental hormones. As described above, a bracket using this polyamide (PA) has also been proposed, but it is a filler-containing one, and the transparency is slightly lowered by mixing this filler. Furthermore, regarding the joining of metal and general-purpose engineering resin, although it is not an application example in a bracket, it is also known that a crystalline resin exhibits an excellent fixing function with a metal (for example, see Patent Document 3). .

JP 2009-72588 A JP-A-9-989888 JP 2009-298144 A

From the above background, it is a crystalline resin for a bracket that has good transparency, excellent aesthetics, high productivity, can be manufactured by injection molding, and has good fixing performance with a metal member such as stainless steel. We focused on applying polyamide (PA). There are various characteristics of polyamide, and the following characteristics can be cited as characteristics corresponding to orthodontics.

Polyamide has properties such as optically high transparency, strength, lack of chipping and mechanical stability, low shrinkage, wear resistance, and good scratch resistance. Furthermore, this material is said to be suitable for producing an injection molded product having high productivity and high thermal and mechanical stress. Taking advantage of such advantages, the present invention is applied to a bracket that can be securely adhered to the tooth surface and can be orthodontic stably for a long period of time. There is also a need for a bracket that is wear resistant to the archwire, is strong and has an improved ligation effect. Furthermore, a bracket that can be firmly bonded to the tooth surface is also required.

The present invention has been made based on the above technical background, and achieves the following object.
An object of the present invention is to provide a polyamide orthodontic bracket having a bracket body made of polyamide and having transparency, abrasion resistance, scratch resistance, chemical resistance and the like.

Another object of the present invention is to provide a polyamide orthodontic bracket with a ligating effect enhanced by embedding a stainless steel groove member for guiding or fixing an arch wire in the bracket body to reinforce the bracket. It is in.
Still another object of the present invention is to provide a polyamide orthodontic bracket which can be easily manufactured by injection molding, and has a structure in which unevenness is provided on an adhesive surface to enhance the adhesive effect.

In order to achieve the above object, the present invention employs the following means.
The polyamide orthodontic bracket of the present invention 1
In the bracket (1) composed of a synthetic resin body having slots (12, 21) for guiding or fixing the archwire (11),
The synthetic resin body (2) is a member molded from a polyamide material and having a mounting surface (9) to the tooth surface,
The polyamide is a transparent member that transmits light,

It has the following structural formula.

The polyamide orthodontic bracket of the present invention 2 is the present invention 1,
The slot (12, 21) is embedded in the synthetic resin main body (2) with a groove member (8) made of stainless steel.
The polyamide orthodontic bracket of the present invention 3 is the

present invention

1 or 2,
The polyamide has a light transmittance of 92% or more and does not contain a filler.

The polyamide orthodontic bracket of the present invention 4 is the

present invention

1 or 2,
The synthetic resin main body mounting surface is characterized by having an uneven adhesive surface on the tooth surface side.
The polyamide orthodontic bracket of the present invention 5 according to the present invention 2,
The bracket (1) is characterized in that the metal groove member is inserted into an injection mold and the polyamide constituting the synthetic resin body is injected and integrally molded.

The polyamide orthodontic bracket of the present invention is a tooth having transparency, abrasion resistance, abrasion resistance, chemical resistance, etc. by making use of the characteristics of polyamide having a specific material and making the bracket body polyamide. It became the bracket for column correction. In addition, by embedding a stainless steel groove member for guiding or fixing the archwire in the bracket body, the bracket is strengthened and the ligation effect is enhanced. Further, the bracket can be easily manufactured by injection molding, and the adhesive surface is provided with irregularities so as to enhance the effect of adhesion to the tooth surface.

FIG. 1 is an external view of a bracket showing Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view of a mold for manufacturing the bracket. FIG. 3 is a detailed cross-sectional view of the part A of FIG. FIG. 4 is a cross-sectional view of a bracket showing another embodiment. FIG. 5 is an external view showing an orthodontic bracket according to Embodiment 2 of the present invention. FIG. 6 is a diagram showing the light transmittance of each wavelength of polyamide. FIGS. 7A to 7E are photographs showing the external appearance showing the results of the solution penetration test of Trogamide CX7233 and other materials.

[Embodiment 1]
(Bracket configuration)
Next, the configuration of the orthodontic bracket according to the first embodiment of the present invention will be described with reference to the drawings. The present invention is applied to all orthodontic brackets, and the type of bracket to be applied is not specified. The type is not limited and is applicable to orthodontic brackets in general. As a representative example of the first embodiment, an example applied to a twin bracket (hereinafter referred to as “bracket 1”) will be described. As shown in FIG. 1, the bracket 1 has a bracket body 2 made of polyamide and is composed of two sets of wings. The wings are composed of

right wings

3 and 4 and

left wings

5 and 6.

A groove member 8 made of a metal plate material is embedded in a slot 7 having a U-shaped cross section, which is a through groove provided in the horizontal direction at the center of the bracket body 2. The groove member 8 is embedded in the central portion of the bracket body 2 so as to cross both wings. The bracket body 2 is made of polyamide (PA) which is a thermoplastic and crystalline resin. The bonding surface 9 of the bracket body 2 is a surface to be bonded to the tooth surface.

The adhesive surface 9 has a curved surface along the tooth surface. The bonding surface 9 has an uneven shape to increase the surface area, thereby increasing the bonding area to which the adhesive is applied. In FIG. 1, the shape of the bonding surface is an undercut, that is, a dent shape in which the dent dent is larger than the surface. However, the shape of the bonding surface 9 is not limited to this shape, and may be another uneven shape. For example, the uneven surface 10 having a narrow valley as shown in FIG. 4 may be used.

Although not shown, the uneven surface of the bonding surface may be drawn in a pattern such as a grid, a spiral, or a circular groove when viewed on a plane. Adhesives are called orthodontic adhesives (bonding materials). Generally, the surface of the tooth is etched as a pre-bonding treatment to make it easier to attach the bracket. We are processing. After this etching process, an adhesive is applied to the adhesive surface of the bracket and pressed and attached. In the case of this example, a shape process corresponding to this is applied to the bracket adhesive surface by molding.

That is, the application area of the bonding adhesive accompanying the bonding is increased. Further, the required performance of the bonding adhesive is that the orthodontic treatment period can be maintained for a long time, and it is easily detached from the tooth surface after the treatment is completed. In the case of the bracket of the present invention, use of polyamide is effective in forming a fine uneven surface by molding because it has a low shrinkage rate and good moldability.

As described above, the bracket 1 basically has a structure in which the bracket main body 2 serving as a base is made of synthetic resin, and a metal groove member (SUS304 is used in this example) 8 is embedded in the slot 7. . Taking advantage of such characteristics, this synthetic resin was identified as polyamide. The reason why the groove portion of the bracket is made of a metal groove member is that it is metal, so that it has good wear resistance and takes advantage of long-term use. Furthermore, there is an advantage that it is made of metal and fits well with the archwire.

Polyamide (PA) has a light transmittance of 92% in this example (actual value by “Trogamide” and “TROGAMID” (registered trademark) products described later), which is almost the same as that of acrylic. Therefore, since the light transmittance is good, there is an effect of excellent aesthetics when used for a bracket. The groove member 8 has a U-shaped cross section, and the center thereof is a groove member slot 12 for guiding or fixing the arch wire 11 (two-dot chain line).

There are various methods for ligating the arch wire 11 to the groove member slot 12. For example, although not shown, the arch wire 11 is wound with a ring-shaped polyurethane rubber or silicon rubber through a wing, and the arch wire 11 fitted into the slot is pressed. Tighten and tighten the winding. The arch wire 11 is stainless steel, but cobalt chrome alloy, titanium nickel alloy, etc. are also used. The cross section is round, square, rectangular or the like. Gold plating may be applied to improve aesthetics. In addition to the ring shape, the rubber has a chain type, and a wire-like attachment wire may be used in addition to the rubber.

(Bracket injection molding method)
Next, an injection molding method for manufacturing the bracket 1 of the embodiment will be described. FIG. 2 is a cross-sectional view showing an example of a mold configuration in which the groove member 8 is inserted in a cavity state before injection. A runner 14 and a gate port 15 are provided in the fixed mold 13, a gate 17 is provided in the movable mold 16, and a synthetic resin injected into the gate 17 from the runner 14 through the gate port 15, that is, polyamide Thus, the bracket 1 is formed. The surface of the groove member 8 is preferably subjected to a treatment such as etching or sand blasting in advance in order to form irregularities on the surface in order to improve the bondability with the polyamide.

2 is a portion showing the bracket 1, but FIG. 3 is an enlarged cross-sectional view of the portion A, showing the bracket 1 as viewed from the direction B in FIG. Although details are omitted, the groove member 8 is inserted and fixed in advance in the mold before being injected into the cavity of the movable mold 16. The cavity is formed along the shape of the bracket body 2. When polyamide is injected from the gate 17, the groove member 8 is surrounded and filled on the joining surface side, and the groove member 8 and the bracket body 2 are integrated to form the bracket 1.

In addition, the mold is shown in FIG. 2 as an example. However, the mold is not limited to the structure shown in the figure. For example, the mold is formed in a state where runners, gates, and molded products are connected as in the case of the plastic model by changing the dividing plane. A mold method may be used. The groove member 8 and the polyamide are bonded to a metal and a synthetic resin, but can be firmly bonded by applying the technique shown in Patent Document 3 as described above. This technique performs chemical etching on the metal surface to make the bonded metal surface have a roughness on the order of microns.

This is a technology for injecting and bonding a crystalline resin composition to the surface formed into an ultra-fine concavo-convex shape to integrate a metal and a synthetic resin. For example, when such a joining method is adopted, that is, when the injection is performed on the surface subjected to the etching treatment for improving the adhesiveness before the insert, the joining between the groove member 8 and the polyamide is strengthened. The possibility that the groove member 8 is detached from the bracket body 2 is eliminated even during the period of use, and stable use is possible. There is no precedent in which polyamide is applied in the form of joining the groove member 8 to the bracket body 2. However, it has been proved that the safety of using polyamide in the oral cavity is not hindered by “Luctone FRS” (trade name) as described in Examples below.

[Embodiment 2]
The orthodontic bracket 1 according to the first embodiment described above has the metal groove member 8 embedded in the slot 7. However, in the case of a bracket that does not require a large correction force, the metal groove member 8 may not be provided. FIG. 5 is an external view showing the orthodontic bracket 20 according to the second embodiment of the present invention. The orthodontic bracket 20 is an orthodontic bracket that does not have the metal groove member 8. The bracket body 2 is the same as the polyamide (PA) described above, and the slot 21 formed integrally with the bracket body 2 guides the archwire 11. The orthodontic bracket 20 is easy to manufacture and does not have the metal groove member 8, so the number of parts is small and the manufacturing cost is low. Further, since the bracket body 2 is made of a transparent material and does not have the metal groove member 8, there is an advantage that the transparency becomes higher during orthodontic treatment.

Hereinafter, examples of the present invention will be described. The polyamide that is the bracket body 2 used in the first embodiment is as follows. Polyamide (PA): The product name used was Trogamide CX7323 ("TROGAMID" is a registered trademark), and the manufacturer used was Daicel-Evonik Ltd, Tokyo Japan. This Trogamide CX7323 (ISO 1874 designation: PA PACM12) is a product called transparent nylon, and is a microcrystalline polyamide. It is a material that does not scatter visible light and is transparent and excellent in UV resistance like glass. It has excellent chemical resistance and stress crack resistance, and has good creep properties and warpage resistance.

The characteristics of Trogamide CX7323 are as follows according to the manufacturer's data. That is, this property is the same transparency as glass (high light transmittance) and its durability, excellent chemical resistance and stress crack resistance, excellent ultraviolet resistance, and stability of mechanical properties due to low water absorption, High dimensional stability, well-balanced mechanical properties, high impact resistance (good even at low temperatures), high level of dynamic strength (ideal for components pressed from the inside), wear resistance, scratch resistance , High glass transition temperature, low shrinkage and low anisotropy, good moldability, and the like. FIG. 6 is a diagram showing the light transmittance of each wavelength, the horizontal axis shows the wavelength of light, and the vertical axis shows the light transmittance of substantially 2 mm of the 2 mm plate material of Trogamide CX7323. The average light transmittance in this wavelength region is approximately 92%.

The structural formula of Torogamide CX7323 is as follows.

As a product using Trogamide CX7233, the present applicant has commercialized "Lushitone FRS" (manufactured by Dentsu Ply Sankin Co., Ltd.) as a denture material. This product uses trogamamide CX7323 as a high grade microcrystalline polyamide among thermoplastic polyamide resins. Trogamide CX7323 does not contain a filler in order to ensure transparency (high light transmittance). It has a proven record as a molded product of “denture making material” applied to dentures that do not use metal clasps. Trogamide CX7323 is not affected by the oral environment even when used for dental treatment, and safety and durability have been confirmed. Features include a supple fit and avoids the risk of metal allergy because no metal clasp is used. Furthermore, it has high aesthetics, is highly safe and can be used for a long time. Stainless steel (SUS304) was used as the metal groove member.

The injection molding conditions for the bracket body of this example are as follows.
Injection pressure: 78 to 157 MPa (800 to 1600 kg / cm ² )
Nozzle temperature during injection: 260-310 ° C
Mold temperature: 40-80 ℃

[Penetration test into turmeric solution]
In order to test the dyeing resistance of Torogamide CX7323, a penetration test was conducted by immersion in a high-concentration turmeric solution used for food. FIGS. 7 (a) to 7 (e) are photographs showing the external appearance showing the results of the solution penetration test of Trogamide CX7323 and other materials. FIG. 7A shows the results of immersion of trogamide CX7233, the left side of the photograph is before the test, and the right side is the appearance after the test. The whole does not change in a transparent state before and after the test, and changes slightly to yellow after the test.
However, the test method and material conditions are as follows.
1) Turmeric: Trade name “S & B Special Sb Curry Can 37g”, manufactured by Sb Foods Co., Ltd. (Head office: Tokyo, Japan)
2) Immersion concentration: 1 wt% aqueous solution 3) Immersion temperature: 37 ± 2 ° C
4) Immersion time: 7 days

In order to compare the colorability of Torogamide CX7323 and other materials, other materials generally used as dental materials were subjected to comparative tests under the same immersion conditions. FIG. 7B shows the results of immersion of polyacetal. The left side of the photograph is before the test, and the right side is the appearance after the test. This polyacetal was colored yellow, which is a turmeric color. However, polyacetal was manufactured by Polyplastics Co., Ltd. (head office: Tokyo, Japan), and Duracon (registered trademark) M90 was used. FIG.7 (c) is the immersion result of the polycarbonate containing glass filler, the left side of the photograph is before the test, and the right side is the appearance after the test. However, as the polycarbonate containing glass filler, a general-purpose product marketed in Japan was used. This polycarbonate with glass filler was non-uniformly colored light yellow, which is a turmeric color. FIG. 7 (d) shows the results of immersion in zirconia (zirconium dioxide, chemical formula: ZrO ₂ ). The left side of the photograph is before the test, and the right side is the appearance after the test. However, for zirconia, zirconia TZ (trade name) manufactured by Tosoh Corporation (head office location: Tokyo, Japan) was used. In this zirconia, no color change due to turmeric was observed.

FIG. 7E shows the results of immersion of aluminum oxide (Al ₂ O ₃ ). The left side of the photograph is before the test, and the right side is the appearance after the test. However, as aluminum oxide, low soda easily sintered alumina AES-11 (trade name) manufactured by Sumitomo Chemical Co., Ltd. (head office: Tokyo, Japan) was used. This aluminum oxide was colored turmeric yellow or light yellow inhomogeneously.
[Consideration of penetration test results]
From the above test results, at least general polyacetal and aluminum oxide change to yellow and cannot be used as a bracket material. Further, this aluminum oxide is not transparent and is not optimal as a material for the bracket of the present invention. General polyamide is not optimal as a bracket of the present invention because it has low colorability but is not transparent. Zirconia was not optimal as a material for the bracket of the present invention because no coloring was observed but it was not transparent.

DESCRIPTION OF SYMBOLS 1 ... Bracket 2 ... Bracket

main body

3, 4, 5, 6 ... Wing 7 ... Slot 8 ... Groove member 9 ... Adhesion surface 10 ... Groove member slot 11 ... Arch wire 12 ... Groove member slot 13 ... Fixed side metal mold 16 ... Movable Side mold

Claims

In the bracket (1) composed of a synthetic resin body having slots (12, 21) for guiding or fixing the archwire (11),
The synthetic resin body (2) is a member molded from a polyamide material and having a mounting surface (9) to the tooth surface,
The polyamide is a transparent member that transmits light,

An orthodontic bracket made of polyamide having the following structural formula:
In the orthodontic bracket made of polyamide according to claim 1,
The orthodontic bracket made of polyamide, wherein the slot (12, 21) is embedded in the synthetic resin main body (2) with a groove member (8) made of stainless steel.
In the orthodontic bracket made of polyamide according to claim 1 or 2,
The polyamide orthodontic bracket has a light transmittance of 92% or more in visible light and does not contain a filler.
In the orthodontic bracket made of polyamide according to claim 1 or 2,
The orthodontic bracket made of polyamide, wherein the mounting surface of the synthetic resin main body has an uneven adhesive surface on the tooth surface side.
In the orthodontic bracket made of polyamide according to claim 2,
The bracket (1) is made of a polyamide which is integrally formed by injecting the metal groove member into an injection mold and injecting the polyamide constituting the synthetic resin body. Orthodontic bracket.