KR20070121894A - Composition for dental materials - Google Patents

Abstract

A composition for dental materials is provided to improve mechanical strength and durability of dental materials and reduce polymerization shrinking property at hardening process by enhancing wear resistance, bending strength and compression strength through addition of surface-modified carbon nanotube. A composition for dental materials comprises 1-99 parts by weight of a functional methacrylate monomer, 0-90 parts by weight of an organic or inorganic filler having an average diameter of 0.01-50 mum, 0.01-10 parts by weight of a surface-modified carbon nanotube, and a catalytic amount of a polymerization initiator for starting polymerization of the monomer, wherein the surface-modified carbon nanotube is prepared by treating the carbon nanotube surface with plasma or by introducing silane after introducing a reaction group to the surface by treating with acid, or by coating the carbon nanotube surface with a polymer having structure similar to matrix monomer.

Description

 Composite Materials Composition {Composition for Dental Materials}

The present invention relates to a dental composite material composition, and more particularly, the surface-modified carbon nanotubes are contained in a mixture of methacrylate monomers and organic and / or inorganic fillers, thereby greatly improving mechanical strength such as wear resistance. To provide a composition that can be used as photopolymerized, chemically polymerized, and double-polymerized dental composites used to prevent the caries and fissures of the caries and the restoration of caries and teeth, as a substitute for missing teeth, do.

Dental composite materials include not only dental composite filling materials for filling and restoring vortices of caries, but also crown materials, cementing materials, orthodontic materials, artificial teeth, and the like. Various studies have been conducted on composite materials.

Dental composites are a special situation in the oral cavity and, unlike ordinary materials, are demanding. That is, a humid environment close to 100% relative humidity, high occlusal pressure during chewing, rapid temperature change, close contact with biological tissues, frequent side effects such as hypersensitivity reactions, oral residence of numerous bacterial species, public The high aesthetic needs of individuals due to the development of the media are major factors.

Dental composites have different requirements depending on the area of application. For example, posterior parts require relatively high strength and high durability, and anterior parts require more aesthetic properties.

In Germany in the 1940's, a method of directly filling a vortex by using a material in which tertiary amine was added to a monomer of methacrylic acid and a benzoyl peroxide added to a polymer powder was cured at room temperature. . This method was commercialized in the US in the 1950s and used in the clinic, which is called autopolymerization resin or room temperature polymerization resin. Self-polymerizing resins are well matched with the color of hemorrhoids, but they are aesthetically pleasing, but they are not used much because of their high shrinkage during curing, poor mechanical strength, high coefficient of thermal expansion, easy discoloration and abrasion, and risks to dimensions. In 1960, Bowen RL of the US Bureau of Standardization discovered that a bifunctional viscous monomer, in which an epoxy group of an epoxy resin was ring-opened with an unsaturated organic acid, was polymerized by benzoyl peroxide and tertiary amine. GMA ", it was confirmed that the physical properties are improved when a large amount of inorganic fillers are mixed with the Bis-GMA monomers, and suggested the possibility as a dental filling resin. At present, resins having Bis-GMA as a substrate and various inorganic substances are used as a dental composite material. In 1974, a urethane dimethacrylate (UDMA) monomer was developed, which is a urethane-based material having a lower viscosity than Bis-GAM to contain more fillers.

As an example of an initial study, U.S. Patent No. 3,066,122 discloses various compositions of dental composites, but has not been widely used clinically because several disadvantages of the materials have been found when used in molar restorations. Since then, dental composites have been steadily developing, and recent dental restoration composites are generally composed of monomers, inorganic fillers, photoinitiators, catalysts, filler surface treatment agents, etc. When the radical is formed by the photoinitiator, the polymerization reaction of the monomer occurs by the generated radical to cure. For example, U. S. Patent No. 6,121, 344 suggests that a photopolymerizable composite material containing particles having an average particle diameter of 0.05 to 0.5 mu m provides excellent strength while providing a high strength and lustrous appearance, but is contained in a monomer as a matrix. It was found that the properties of the fillers did not improve the wear resistance.

On the other hand, U.S. Patent No. 6,030,606 discloses ethoxylate bisphenol A dimethacrylate 6 (Bis-EMA6), urethane dimethacrylate (UDMA), 2,2-bis- (4 as monomer components of dental composite materials. -(2-hydroxy-3-methacryloyloxypropoxy) phenyl) propane (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA), etc. are used to increase the molecular weight of the monomer in the existing monomer composition. By improving the physical properties, but this is only a limited application of facts well known in the art, it was confirmed that the improvement of physical properties by the improvement of the filler is not provided.

Recently, U.S. Patent No. 6,898,948 introduces nano-sized silica particles using a sol-gel method into dental materials to achieve physical properties such as mechanical strength, but the content to be introduced into a high viscosity dental monomer composition is limited. The disadvantage is that you have to use excess to achieve this.

Therefore, an object of the present invention is to solve the problems of the prior art and the technical problems that have been requested from the past.

That is, an object of the present invention, by further containing a surface-modified carbon nanotubes in a mixture containing a methacrylate monomer and an organic and / or inorganic filler, the polymerization shrinkage at the time of curing, mechanical strength and the like can be improved It is to provide a composition.

Dental composite composition according to the present invention for achieving this object,

1 to 99 parts by weight of a functional methacrylate monomer;

0 to 90 parts by weight of organic and / or inorganic fillers having an average particle diameter of 0.01 to 50 μm;

0.01 to 10 parts by weight of surface modified carbon nanotubes; And,

A catalytic amount of a polymerization initiator for initiating the polymerization of the monomer;

It is composed to include.

Preferred examples of the functional methacrylate monomer used in the present invention are MMA derivatives, which include Bis-GMA (2,2-bis- (4- (2-hydroxy-3-methacryloyloxyprop). Foxy) phenyl) propane), TEGDMA (triethylene glycol dimethacrylate), UDMA (urethane dimethacrylate), Bis-EMA (ethoxylate bisphenol A dimethacrylate), polyethylene glycol dimethacrylate ( PEGDMA), glycerol dimethacrylate (GDMA), and the like, but are not limited thereto, and in some cases, may be used in the form of a mixture of two or more thereof.

The content of the monomer is, as described above, 1 to 99 parts by weight based on 100 parts by weight of the total composition, if the content is 1 parts by weight or less, it is difficult to mix with inorganic fillers, etc., the content of the filler is less than 99 parts by weight Mechanical strength is reduced, which is undesirable.

Preferred examples of the inorganic filler used in the present invention include amorphous synthetic silica, crystalline natural silica, barium aluminum silicate, kaolin, talc and the like, and radiopaque glass powders such as strontium aluminum silicate. It is not limited, and in some cases, may be used in the form of a mixture of two or more thereof. In general, the inorganic filler is hydrophilic and incompatible with the hydrophobic functional methacrylate monomer, so that the inorganic filler can be treated with a silane coupling agent to enhance affinity with the monomer. Specific examples of the silane coupling agent as the hydrophobic surface treating agent of the inorganic filler are known in the art, and thus description thereof is omitted.

The organic filler used in the present invention may be prepared in the form of a powder by synthesizing the monomer constituting the matrix of the composition of the present invention or a monomer having compatibility therewith by bulk polymerization, emulsion polymerization, suspension polymerization or the like, and having an average particle diameter of 0.01 to What was granulated to 50 micrometers can be used.

The inorganic fillers and / or organic fillers, if desired, may not be included in the composition of the present invention and may completely replace its role as a filler (filler) with the surface modified carbon nanotubes described below. Preferably, the inorganic filler and / or the organic filler is contained in 10 to 85 parts by weight based on the total weight of the composition.

The average particle diameter of the inorganic filler and / or organic filler is preferably 0.01 to 50 μm, as described above, and when smaller than 0.01 μm, uniform dispersion in the composition may be difficult due to cohesion between the particles. On the contrary, if it is larger than 50 μm, the texture of the composite material is reduced, and thus the workability is difficult to be applied to the tooth by the operator, and when the large particles are lost due to wear after curing, the glossiness may be reduced. Not.

Carbon nanotubes (CNT) used in the present invention was discovered by Iijima of NEC, Japan in 1991, and has a structure in which graphite is rolled in a cylinder form having a diameter of 1 to 100 nm, and strong sharing between carbons. It is a material that has high mechanical strength by bonding and exhibits very good mechanical properties due to its high Young's modulus and high aspect ratio. Using these characteristics, research on CNT-polymer composites using carbon nanotubes as nano reinforcing materials in polymer resins having excellent versatility and moldability is being actively conducted. In addition, since carbon nanotubes are made of carbon and have a very low mass as compared to their physical properties, carbon nanotubes can be said to have advantages that are much better than expected to improve mechanical properties of dental structural materials by other additives.

Carbon nanotubes may be prepared by arc-discharge, laser vaporization, plasma enhanced chemical vapor deposition, thermal chemical vapor deposition, or the like.

There are some prior arts for incorporating such carbon nanotubes into dental materials. For example, US Pat. No. 6,872,403 discloses a technique of applying carbon nanotubes to dental prosthetic materials by dispersing carbon nanotubes in MMA monomer using ultrasonic waves and mixing them with PMMA powder. However, the above technique is complicated in the manufacturing method, the ultrasonic wave directly applied to the monomer may cause deterioration of the monomer, there is no consideration of surface modification, it is difficult to secure a uniform dispersion of carbon nanotubes without entanglement, the scope of application Is limited to less than 5%.

On the other hand, there are some problems in the inclusion of carbon nanotubes in the dental composite material, the most serious of them is the difficulty of dispersion. That is, since the carbon nanotubes are particles having a very high tendency to aggregate with each other, when directly injected into the matrix monomer, dispersion is difficult, and thus it is difficult to exhibit the desired mechanical properties in the present invention.

In this regard, the present invention proposes to perform a surface modification before dispersion to the matrix monomers. Surface modification of the carbon nanotubes can be largely divided into a method of oxidizing the surface (oxidation surface modification method) and a method of not oxidizing the surface (non-oxidation surface modification method).

First, the oxidation surface modification method may be divided into a gas phase oxidation method and a liquid phase oxidation method. Among them, the vapor phase oxidation method using gas or gas phase oxidation using air or oxygen is generally simple in the surface modification process, whereas the treatment temperature is high. Carbonization can occur, causing severe degradation and weight loss. Therefore, the surface modification by plasma is more preferable as the gas phase oxidation surface modification method, and the plasma surface modification method has the advantages of the least damage to the physical properties of the reinforcement itself, less external contamination, and almost no by-products. There is a disadvantage that is required.

The liquid phase oxidation reforming method is advantageous to improve the interfacial bonding force by providing an active site easily on the surface with less etching effect than the gas phase oxidation reforming method. For example, a method of improving affinity with the monomer by a silane treatment step described above after treating with an acid or the like and introducing a reactive group such as a hydroxyl group or an acidic group to the surface is particularly preferable. A detailed example of this can be found in Example 1 below.

As the non-oxidation surface modification method, preferably, the surface of the carbon nanotubes may be considered to be coated with a polymer having a structure similar to that of the matrix monomer. Polymer coating method is a method of mixing a molten polymer and carbon nanotubes, a method of mixing the solution polymer and carbon nanotubes to evaporate the solvent and then powderized, bulk polymerization after mixing with the monomer, emulsion polymerization, suspension polymerization, The method of wrapping to predetermined thickness is possible using superposition | polymerization methods, such as dispersion polymerization. A detailed example of this can be found in Example 2 below.

The content of the surface-modified carbon nanotubes, as described above, based on 100 parts by weight of the total composition of 0.01 to 10 parts by weight, if the content is less than 0.01 parts by weight can improve the mechanical properties of the object of the present invention It is not preferable to add more than 10 parts by weight of carbon nanotubes in consideration of the superior performance and price compared to other materials.

The carbon nanotubes contained in the dental composite composition of the present invention cause various effects. First, in the curing reaction, the double bond of the methacrylate monomer is changed into a single bond polymer to suppress polymerization shrinkage and shrinkage. Dissipate shrinkage stress generated during This improves the bond between the finally obtained composite material and the teeth and reduces the leakage of margins to block secondary caries. In addition, internal crack formation is suppressed through shrinkage stress dispersion, thereby improving mechanical strength. Due to the high surface energy of the carbon nanotubes, due to the high miscibility with the matrix resin, abrasion resistance is rapidly increased to secure durability required for dental materials.

The reaction for polymerizing (curing) the composition of the present invention may be variously performed according to the type of catalyst used, such as a cation forming mechanism, an anion forming mechanism, a radical forming mechanism, and the like. The double radical forming mechanism is most commonly used. According to these polymerization mechanisms, the polymerization reaction can be carried out by photopolymerization reaction, chemical polymerization reaction, double polymerization reaction and the like.

The photopolymerization reaction is carried out by a photopolymerization initiator activated by visible light to initiate a polymerization reaction of monomers. Representative examples of the photopolymerization initiator are α-diketone-based carbonyl compound photopolymerization initiators and acylphosphine oxide photopolymerization initiators. Etc. Photopolymerization initiators typically use hydrogen donors as cocatalysts and mainly work with tertiary amine based catalysts. Specific examples of the photopolymerization initiators and cocatalysts are known in the art, and a description thereof is omitted herein.

The chemical polymerization reaction is performed using two kinds of paste reaction systems, namely, a first paste containing a peroxide such as benzoyl peroxide, and a second paste containing an aromatic tertiary amine such as dimethyl toluidine. When the paste is mixed, radicals are formed to initiate polymerization.

The double polymerization reaction is initiated by two kinds of paste reaction systems in which a catalyst is formulated so as to induce the photopolymerization reaction and the chemical polymerization reaction at the same time.

Since the polymerization initiator for such a polymerization reaction may be included in the composition within a range that does not affect the physical properties of the product while inducing a polymerization reaction, the "catalyst amount" refers to this content range, the type and content of other components of the composition And may vary depending on the type of catalyst.

Other well-known compounds may be added to the composition of the present invention within the scope of not impairing the effects of the invention, and examples of such materials include polymerization inhibitors, antioxidants, colorants, and fluorine additives.

Hereinafter, the contents of the present invention will be described in detail with reference to examples and comparative examples, but the application scope of the present invention is applied to the dental composite material, and only for the purpose of showing detailed application examples of the present invention. The example applied to a composite material is demonstrated below. Thus, the scope of the present invention is not limited thereto.

Example  One: Silane  Coated Carbon Nanotube Fabrication

Iljin Nanotech's multi-wall nanotubes (MWCNT) prepared by CVD were used. The MWCNTs used were 10-25 nm in diameter, 10-50 μm in length, and had an aspect ratio of 1000. In order to remove impurities that may be present on the surface of CNTs, washing was repeated two to three times with distilled water, followed by vacuum drying at about 80 ° C. for at least 24 hours. The washed CNTs were treated with 35% phosphoric acid for 24 hours, washed with distilled water, and reacted with a hydroxyl group on the surface with a silane treatment solution prepared in advance, and lyophilized to prepare S-CNT.

Example  2: with polymer Applied  Carbon nanotube manufacturing

The surface-modified and purified SWCNT with nitric acid is used. 0.5 phr of SWCNT was added to distilled water, followed by ultrasonic dispersion while stirring with a stirrer. At the time of dispersion, the temperature of the outer jacket was 10 degreeC. First, 0.1 phr of PVOH is completely dissolved in distilled water as a stabilizer. Then, 20 phr of methyl methacrylate, 0.1 phr of ethylene glycol dimethacrylate and 0.1 weight ratio of AIBN to monomer are added and dispersed, followed by 60 ° C. The reaction was carried out for 12 hours to obtain a new bead form of CNT-polymer composite (W-SWCNT) in which SWCNT was coated with a polymer.

Example  3: Photopolymerization  Preparation of Restorative Composite Materials

To the composition of Table 1, to prepare a photopolymeric composite composite composition according to the present invention.

The compressive strength measured according to the ADA standard for the cured product of the composition was 350 ± 20 MPa, the polymerization shrinkage measured by the Watt shrinkage tester was 2.1 ± 0.1%. Watt shrinkage was measured according to the method of Dental Materials, Oct 1991, pgs 281-286. Wear was measured using a 3-body wear level meter. Abrasion was measured according to the method of J Den Res 76 (7): 1405-1411, july, 1997. 50,000 times of reciprocation was carried out with a pressure of 70 N between the composite and the tooth under abrasive, and the changed height was measured by profilometry. The measurement result was 20 ± 5 μm. The hardness was measured by using a Schimadzu microhardness tester to measure the length of the diamond-shaped indentation formed by applying a load of 25 kgf to the specimen for 15 seconds. The calculated fine hardness was 150 ± 7 Kg / mm ² .

Example  4

In the composition of Table 1, except that S-CNT was added in 0.1 parts by weight, a composition was prepared in the same manner as in Example 3.

The compressive strength measured according to the ADA standard for the cured product of the composition was 400 ± 20 MPa, the polymerization shrinkage measured by the Watt shrinkage rate meter was 2.1 ± 0.1%. The wear degree measured by the 3-body wear level gauge was 9 ± 5 μm. The microhardness measured with a microhardness meter was 150 ± 7 Kg / mm ² .

Example  5: Photopolymerization  Preparation of dental heating sphere material composition

To the composition shown in Table 2 below, a photopolymerizable dental heat curing material composition according to the present invention was prepared.

The microhardness measured by the microhardness meter for the composition was 50 ± 4 Kg / mm ² .

Comparative Example 1

In the composition of Table 1, the composition was prepared in the same manner as in Example 3 except that CNT was not included.

The compressive strength of the cured product of the composition according to the ADA standard was 300 ± 20 MPa, the polymerization shrinkage measured by a watt shrinkage measuring instrument was 2.6 ± 0.1%.

The wear degree measured by the 3-body wear level gauge was 50 ± 10 μm.

Comparative Example 2

 In the composition of Table 2, the composition was prepared in the same manner as in Example 5, except that CNT was not included.

The microhardness measured by the microhardness meter for the composition was 10 ± ² Kg / mm ² .

Comparative Example 3

 In the composition of Table 1, the composition was prepared in the same manner as in Example 3 except for including the surface-modified CNT.

As CNTs were not surface modified, coagulation was remarkable in the dispersion process. The compressive strength of the cured product according to the ADA standard was 310 ± 20 MPa, and the polymerization shrinkage measured by the Watt shrinkage meter was 2.4 ± 0.1. It was%.

The wear degree measured by the 3-body wear level gauge was 40 ± 10 μm.

[Comparative Example 4]

In the composition of Table 2, the composition was prepared in the same manner as in Example 5 except for including CNTs without surface modification.

Since the CNTs were not surface-modified, the aggregation phenomenon was remarkable in the dispersion process, and the microhardness of the composition was 15 ± 2 Kg / mm ² .

As described above, the dental composite composition of the present invention includes a surface-modified carbon nanotube, the polymerization shrinkage is reduced, less marginal leakage, resistance to deformation, mechanical strength, such as compressive strength, flexural strength is improved In addition, the wear resistance, surface hardness, etc. is increased durability can be used widely throughout the dental material.

Claims (6)

1 to 99 parts by weight of a functional methacrylate monomer; 0 to 90 parts by weight of organic and / or inorganic fillers having an average particle diameter of 0.01 to 50 μm; 0.01 to 10 parts by weight of surface modified carbon nanotubes; And A catalytic amount of a polymerization initiator for initiating the polymerization of the monomer; Dental composite material composition comprising The method of claim 1, The functional methacrylate monomers include Bis-GMA (2,2-bis- (4- (2-hydroxy-3-methacryloyloxypropoxy) phenyl) propane), TEGDMA (triethylene glycol di Methacrylate), UDMA (urethane dimethacrylate), Bis-EMA (ethoxylate bisphenol A dimethacrylate), polyethylene glycol dimethacrylate (PEGDMA) and glycerol dimethacrylate (GDMA) At least one monomer selected from the group; The inorganic filler is at least one filler selected from the group consisting of amorphous synthetic silica, crystalline natural silica, barium aluminum silicate, kaolin, talc, and radiopaque glass powders; The organic filler is a composition characterized in that it is prepared in the form of a powder after synthesizing the monomer of the composition and / or monomers compatible with the bulk polymerization, emulsion polymerization, suspension polymerization and the like.   The composition of claim 2, wherein the inorganic filler and the carbon nanotubes are treated with a silane coupling agent to increase affinity with the monomers. The composition of claim 1, wherein the carbon nanotube is modified on its surface by an oxidized surface modification method or a non-oxidized surface modification method. The method of claim 4, wherein the oxidation surface modification method is characterized in that the surface of the carbon nanotubes are treated with plasma, or a silane is introduced into the surface after introducing a reactive group to the surface by acid treatment. The method of claim 4, wherein the non-oxidation surface modification method is characterized in that the surface of the carbon nanotubes are coated with a polymer having a structure similar to the matrix monomers.