JPH0157082B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composite restorative material, particularly a composite restorative material suitable for dental use. More specifically, wear resistance,
The present invention relates to a composite restorative material that has excellent smoothness, high surface hardness, and is easy to polish. Currently, bisphenol A glycidyl methacrylate (addition product of bisphenol A and glycidyl methacrylate, hereinafter abbreviated as Bis-GMA) is used as a composite restorative material, such as a dental composite restorative material, which is said to have relatively small polymerization shrinkage. Generally, a large amount of glass beads or pulverized quartz with a particle diameter of several micrometers is mixed with the acrylic monomer liquid as the main component, and a polymerization initiator that decomposes at room temperature is added to polymerize and harden in the oral cavity. It is used in many ways. Because the above-mentioned restorative materials use optically transparent inorganic powder as a filler, they suffer from shrinkage and transparency during polymerization compared to resin-based restorative materials made of acrylic polymer and the same monomer. It is characterized by its excellent linear expansion coefficient and mechanical strength, and is widely used by clinicians. However, they are far inferior to natural teeth in terms of wear resistance, surface smoothness, and surface hardness, and there are still points that need to be improved. Various improvement techniques have been proposed to improve the above-mentioned drawbacks. For example, JP-A-1987-
124491 uses inorganic powder as a filler with a particle size in the range of 10 to 400 mμ, of which at least 50% has a particle size of 10 to 40 mμ, without impairing mechanical strength and transparency. Restorative materials have been proposed that have improved surface smoothness, which is one of the drawbacks of conventional inorganic fillers. However, when an inorganic powder containing a large amount of ultrafine particles of 10 to 40 mμ as described above is used as a filler, the surface area of the filler becomes significantly large, so when it is blended into an acrylic monomer liquid, the viscosity increases. rises significantly. Therefore, if the blending ratio of the inorganic filler is increased to take advantage of the characteristics of a composite restorative material consisting of an inorganic filler and an acrylic monomer liquid, kneading operations during use or restorative operations in the oral cavity will become almost impossible. Become. That is, when using the above-mentioned ultrafine particles as a filler, it is necessary to limit the amount to 30 to 60 wt% due to operability requirements. In this way, due to the demand for appropriate operability, the amount of inorganic filler blended is reduced, and although transparency and surface smoothness are improved, the coefficient of thermal expansion is conversely increased. Moreover, there is a drawback that the surface hardness becomes low. Further, such a decrease in the blending ratio of the inorganic filler is undesirable because it results in an increase in the amount of wear in the toothbrush wear test, which is one of the methods for evaluating the wear resistance of dental materials. In addition to the above-mentioned drawbacks, both those using conventional fillers and those using ultrafine inorganic powder as a filler have the practical difficulty of polishing the surface after repair. It has a big drawback. That is, in the former case, it is difficult to obtain a smooth surface by polishing because the filler is large, several tens of micrometers; in the latter case, although a smooth surface can be obtained, it is too easy to scrape and the shape cannot be corrected. It has the disadvantage that it is difficult to do. Therefore, the inventors of the present invention have conducted extensive research, especially regarding inorganic fillers, in order to improve the various drawbacks mentioned above. As a result, the particle size of the inorganic filler is within an appropriate range, and by using spherical particles with a uniform particle size distribution, wear resistance is improved without compromising mechanical strength, and the surface becomes smooth. It was found that the water quality was improved. Even more surprisingly, by using spherical particles with uniform particle sizes as described above,
To have a surface hardness higher than that of known fillers, such as those using ultrafine particle fillers, and in addition, it is very easy to polish the surface after repair, and to easily obtain a smooth and glossy surface. Various unexpected effects can be achieved, such as the ability to The present invention uses a polymerizable vinyl monomer and a particle size
This is a composite restorative material made of amorphous silica, which is a spherical particle in the range of 0.1 to 1.0μ and the standard deviation value of the particle size distribution is within 1.30. One component of the composite restorative material of the present invention is a polymerizable vinyl monomer. The vinyl monomer is not particularly limited, and known ones commonly used as dental restorative materials can be used. The most typical vinyl monomer is a polymerizable vinyl monomer having an acrylic group and/or a methacrylic group. Specific examples of vinyl monomers having an acrylic group and/or methacrylic group include bisphenol A diglycidyl methacrylate, methyl methacrylate, bismethacryloethoxyphenylpropane, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and tetramethylol trimethacrylate. Acrylate, tetramethylolmethane trimethacrylate, trimethylolethane trimethacrylate, etc. are suitable. Also preferably used is a vinyl monomer having a urethane structure represented by the following structural formula. However, in the above formula, R ₁ , R ₂ , R ₃ and R ₄ are the same or different H or CH ₃ , (-A-) is -(CH ₂ -) ₆ ,

[Formula] or

[Formula] is preferred. Since these vinyl monomers are known as dental materials, they may be used alone or in combination as required. Another component of the composite restorative material of the present invention is amorphous silica. The amorphous silica used in the present invention must be spherical particles with a particle size in the range of 0.1 to 1.0 μm, and the standard deviation value of the particle size distribution must be within 1.30. The above-mentioned particle size, particle shape, and particle size distribution are all very important factors, and the object of the present invention cannot be achieved if any of the conditions is absent. For example, if the particle size of amorphous silica is smaller than 0.1μ, the particle size will increase significantly when it is kneaded with a polymerizable vinyl monomer to form a paste-like mixture, and the blending ratio should be increased to prevent the increase in viscosity. If the material is used as a material, the operability deteriorates, so that it cannot be used as a material for practical use. If the particle size is larger than 1.0 μm, it is not preferable because the resin obtained by polymerizing and curing the vinyl monomer has defects such as a decrease in abrasion resistance or surface smoothness, and also a decrease in surface hardness. Furthermore, if the standard deviation value of the particle size distribution is larger than 1.30, the operability of the composite restorative material will be significantly reduced, so that it cannot be used as a restorative material for practical use. Furthermore, the amorphous silica has a particle size in the range of 0.1 to 1.0μ,
Even if the standard deviation of the particle size distribution is within 1.30, if the shape of the particle is spherical, the effects of the present invention as described above will not be achieved, especially in terms of wear resistance, surface smoothness, surface hardness, etc. It cannot be satisfactory. The method for producing amorphous silica used in the present invention is not particularly limited, and any production method may be used as long as the amorphous silica has the above-mentioned particle size, shape, and standard deviation of particle size distribution. It's okay. Generally, industrially, it is produced by hydrolysis of silicate ester (Inorganic Materials Research Institute Report No. 14)
No. 49 to 58 (1977)) are preferably adopted. Generally, it is preferable to reduce the number of silanol groups on the surface of industrially obtained amorphous spherical silica in order to maintain surface stability. For this purpose, a method of drying the spherical amorphous silica and then firing it at a temperature of 500 to 1000°C is often suitably employed. During the firing, some of the silica particles may be sintered and aggregated, so it is usually preferable to use a crusher, vibrating ball mill, jet pulverizer, etc. to loosen the aggregated particles. Generally, in order to maintain stability, the fired silica particles are most preferably used after surface treatment using an organic silicon compound. The surface treatment method described above is not particularly limited and may be carried out by any known method, for example, by treating silica particles with a known organosilicon compound such as γ-methacryloxypropyltrimethoxysilane or vinyltriethoxysilane in a mixed solvent of alcohol/water for a certain period of time. A method is adopted in which the solvent is removed after contacting. The particle size and shape of the amorphous silica used in the present invention can be confirmed by taking a microscopic photograph, and the standard deviation value of the particle size distribution is determined by the unit area of the microscopic photograph or the unit field of view of the microscope. It can be calculated from the number of particles present in the particle and their respective diameters using the calculation formula described below. The above-mentioned microscopic photograph may be any photograph as long as the shape of the particles of amorphous silica can be observed, but in general, scanning electron micrographs, transmission electron micrographs, etc. are suitable. In addition, if amorphous silica is mixed with another liquid substance such as a polymerizable vinyl monomer to form a paste mixture, first extract and remove the liquid substance using an appropriate organic solvent, and then remove the liquid substance by the same operation as above. It is a good idea to investigate the properties of crystalline silica. As described above, the amorphous silica used in the present invention is a spherical particle, but whether or not it is spherical is confirmed by measuring the specific surface area of the amorphous silica in addition to the above-mentioned microscope. I can do it.
For example, if the specific surface area of amorphous silica having a particle diameter in the range of 0.1 to 1.0 μm is about 4.0 to 40.0 m ² /g, it almost matches the specific surface area calculated assuming a perfect spherical shape. Therefore, the amorphous silica used in the present invention preferably has a specific surface area of 4.0 to 40.0 m ² /g. The composite restorative material of the present invention is used by mixing the polymerizable vinyl monomer component and the specific amorphous silica. For example, when using the above-mentioned composite restorative material as a dental restorative material, not only the operability is an important factor, but also the mechanical strength, abrasion resistance, surface smoothness, etc. of the resulting cured composite resin. Must be well maintained. For this reason, it is generally preferable to select the amount of amorphous silica to be added within a range of 70 to 90%. In addition, when used as the above-mentioned dental composite restorative material, a paste-like mixture consisting of amorphous silica, a polymerizable vinyl monomer, and a polymerization accelerator (for example, a tertiary amine compound), amorphous silica, a vinyl monomer, and A method is preferably used in which a paste-like mixture consisting of a polymerization initiator (for example, an organic peroxide such as benzoyl peroxide) is prepared in advance, and both are kneaded and cured immediately before the repair operation. The composite resin made by curing the composite restorative material of the present invention has mechanical strength such as compressive strength that is comparable to conventional ones, and has excellent wear resistance and surface smoothness, as well as high surface hardness. It has many excellent features such as being very easy to polish the surface. However, the reason why such characteristics appear is not necessarily clear at present, but the inventors of the present invention think as follows. Firstly, by using amorphous silica, which has a spherical particle shape and a uniform particle size with a standard deviation of particle size distribution within 1.30, it is possible to achieve a wide particle size distribution compared to conventional methods. Moreover, compared to the case where fillers with irregular shapes are used, the amorphous silica is more uniformly and densely packed into the composite resin obtained by curing, and secondly, the particle size range is 0.1~ By using particles with a particle size within the range of 1.0 μm, the polished surface of the composite resin after curing becomes smoother than when using conventional inorganic fillers with a particle size of several tens of micrometers. The total specific surface area of the filler is smaller than when using an ultrafine particle filler whose main component is mμ fine particles, and therefore the amount of filler packed can be increased under conditions with appropriate operability. There could be a reason. By blending the specific amorphous silica and a polymerizable vinyl monomer, the composite restorative material of the present invention exhibits a number of previously unanticipated advantages as described above. The above-mentioned composite restorative material of the present invention exhibits the above-mentioned merits by a two-component combination of a polymerizable vinyl monomer component and a specific amorphous silica component, but in addition to these components, dental restorative materials are generally used. Additional components used as additives can also be added as necessary. Typical of these additive components are as follows. Examples include radical polymerization inhibitors, coloring pigments for color matching, and ultraviolet absorbers. EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to these Examples. In addition, measurements of various properties (particle size, standard deviation value of particle size distribution, specific surface area) of inorganic fillers containing amorphous silica shown in the following Examples and Comparative Examples, preparation of paste of composite restorative materials, and The curing method and the physical property values (compressive strength, bending strength, toothbrush wear depth, surface roughness, surface hardness) of the cured composite resin were measured according to the following methods. (1) Standard deviation value of particle size and particle size distribution Take a scanning electron micrograph of the powder, and calculate the number of particles (n) observed within the unit field of view of the photo and the particle size (diameter x _i ). It is calculated using the following formula. (2) Specific surface area Shibata Chemical Equipment Co., Ltd. Rapid surface measuring device SA−
1000 was used. The measurement principle is the BET method. (3) Method for preparing and curing paste of composite restorative material First, amorphous silica surface-treated with γ-methacryloxypropyltrimethoxysilane and vinyl monomer were placed in an agate mortar in a predetermined ratio to form a uniform paste. Knead thoroughly until smooth. Next, the paste was divided into two equal parts, and a polymerization accelerator was further added to one paste and thoroughly mixed (this was referred to as paste A). In addition, an organic peroxide catalyst was added to the other paste and mixed thoroughly (this was added to paste B).
). Next, equal amounts of paste A and paste B were kneaded for about 30 seconds, filled into a mold, and hardened. (4) Compressive strength Mix paste A and paste B and
After polymerizing for 30 minutes, the test piece was immersed in water at 37°C for 24 hours. Its size and shape are 6 in diameter
It is cylindrical with a height of 12 mm. This test piece was mounted on a testing machine (UTM-5T manufactured by Toyo Baudouin), and the compressive strength was measured at a crosshead speed of 10 mm/min. (5) Bending strength: Mix paste A and paste B and
After polymerizing for a minute, the test pieces were immersed in water at 37°C for 24 hours. Its size and shape are 2×2×
It is a 25mm prismatic shape. For the bending test, we used a bending test device with a distance between fulcrums of 20 mm made by Toyo Baudouin.
The test was carried out by attaching it to UTM-5T, and the crosshead speed was 0.5 mm/min. (6) Toothbrush wear depth and surface roughness Mix paste A and paste B and heat at room temperature for 30 minutes.
After polymerizing for a minute, the test pieces were immersed in water at 37°C for 24 hours. Its size and shape are 1.5×10
It is a plate-shaped piece with a size of 10 mm. Load the test piece at 400g
After abrasion of 1500 m with a toothbrush, the 10-point average roughness was determined using a surface roughness meter (Surfcom A-100).
Further, the wear depth was determined by dividing the wear weight by the density of the composite resin. (7) Surface hardness: Mix paste A and paste B to 30 at room temperature.
After polymerizing for a minute, the test pieces were immersed in water at 37°C for 24 hours. Its size and shape are 2.5×10
It is in the shape of a mm disc. The measurement used a micro Brinell hardness test. In addition, the abbreviations used in Examples and Comparative Examples are as follows unless otherwise specified. Example 1 Ethyl silicate (manufactured by Nippon Colcoat Co., Ltd.) 500
g and 1.2 methanol were placed in a beaker with a capacity of 3 and mixed. (This solution is hereinafter referred to as the feed solution.) In another glass container with a capacity of 10 methanol.
6.0, ammonia water (ammonia concentration 25-28%)
I prepared 650g. (This solution is called the reaction tank liquid.)
The temperature of the reaction tank liquid was maintained at 20°C, and the feed liquid was added over 30 minutes while stirring. After the reaction is complete, remove the solvent from the cloudy reaction tank liquid using an evaporator and dry it.
It was baked at 1000°C for 1 hour. After firing, the fired product was crushed in an agate mortar to obtain silica particles. This silica particle has a particle size of 0.18~ as observed with a scanning electron microscope.
It is in the range of 0.24μ, the shape is a true sphere, the standard deviation value of the particle size distribution is 1.04, and the specific surface area is 20.6m ² /
It was hot at g. The obtained silica particles were further surface-treated with γ-methacryloxypropyltrimethoxysilane. The treatment is γ-
methacryloxypropyltrimethoxysilane
Added 6wt% and incubated at 80℃ in water-ethanol solvent for 2 hours.
After refluxing for an hour, remove the solvent with an evaporator.
Furthermore, a method of vacuum drying was used. Next, as a vinyl monomer, a mixture of bisphenol A diglycidyl methacrylate (hereinafter referred to as Bis-GMA) and triethylene glycol dimethacrylate (hereinafter referred to as TEGDMA) (mixing ratio is Bis-GMA/TEGDMA = 3/7 molar ratio). A paste-like composite restorative material was obtained by blending the above-mentioned silica particles with the above-mentioned silica particles and thoroughly kneading the mixture. At this time, the filling amount of silica particles in the composite restorative material was 75.8 wt%, and the viscosity of the paste was appropriate for operation. Next, divide the paste into two equal parts, one with N and N as polymerization accelerator.
-Dimethyl-p-toluidine was added to the other side, and benzoyl peroxide as a polymerization initiator was added at 1 wt% to the vinyl monomer to make paste A (former).
and Paste B (latter) was prepared. Take equal amounts of Paste A and Paste B above and 30
After kneading and hardening at room temperature for a few seconds, the physical properties were measured, and the results showed a compressive strength of 3420 Kg/cm ² and a bending strength.
The weight was 750 kg/cm ² , the surface roughness was 0.5 μm, the surface hardness was 60.0, and the toothbrush wear depth was 7.0 μm. When the surface was polished using Soflex (manufactured by 3M), a smooth surface was easily obtained without excessively abrading the surface of the composite resin. Examples 2 to 4 In the same manner as in Example 1, silica particles having different particle sizes and particle size distributions were prepared by changing the feed liquid composition and the reaction tank liquid composition. The results are summarized in Table 1. Using these three types of silica particles, a paste was prepared in the same manner as in Example 1 using the same vinyl monomer, and the paste was further cured and the physical properties of the composite resin were measured. . The results are also summarized in Table 1.

[Table] Examples 5 to 7 Using the silica particles obtained in Example 3, U-4HMA, U-4TMA, U-
A paste composite restorative material was prepared in the same manner as in Example 1 except that 4BMA, tetramethylolmethane triacrylate (hereinafter referred to as TMMT) and methyl methacrylate (hereinafter referred to as MMA) were used. The mixing proportions of the vinyl monomer components are shown in Table 2. The paste-like composite restorative material was further cured in the same manner as in Example 1, and its physical properties were measured. The results are also shown in Table 2.

[Table] Comparative Examples 1 to 3 A paste was prepared in the same manner as in Example 1, except for quartz powder, amorphous silica ultrafine particle powder (Erosil R-972 manufactured by Nippon Aerosil), and amorphous silica as the inorganic filler. A composite restorative material was prepared, cured, and its physical properties were measured. The results are also shown in Table 3.
The amorphous silica used in Comparative Example 3 was Example 1, 2,
10wt% of each of the amorphous silica used in 3 and 4,
A mixture of 20wt%, 30wt%, and 40wt% was used.

【table】

Claims (1)

[Claims] 1. A polymerizable vinyl monomer and a particle size of 0.1 to
A composite restorative material comprising amorphous silica having spherical particles in the range of 1.0μ and a standard deviation value of the particle size distribution within 1.30. 2. The composite restorative material according to claim 1, which contains 70 to 90% (by weight) of amorphous silica. 3. The composite restorative material according to claim 1, wherein the amorphous silica has a specific surface area of 4.0 to 40.0 m ² /g. 4. The composite restorative material according to claim 1, wherein the amorphous silica is surface-treated with an organic silicon compound. 5. The composite restorative material according to claim 1, wherein the polymerizable vinyl monomer is a vinyl monomer having an acrylic group and/or a methacrylic group.