Dental abrasives

Abstract

To provide a dental polishing material that is less likely to cause bleeding of a plasticizer and a change in hardness before and after high-pressure steam sterilization, in a dental rubber polishing material for polishing a dental restoration.SOLUTION: A dental polishing material is made of an abrasive grain, an elastomer binder and a plasticizer. In the plasticizer, two or more types of plasticizers are compounded. At least one of the types of plasticizers is an epoxy type ester compound or epoxy soybean oil.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dental rubber abrasive for polishing dental restorations made of ceramics, metals, composite resins, resins, and the like. [Background technology]

[0002] During dental treatment, if there is a tooth disease such as caries, the tooth substance in the carious area is generally removed and restorative treatment is performed using dental restorations (dental prosthetic devices, dental fillings, etc.) made from various materials such as ceramics, metals, and composite resins.

[0003] Dental restorations require morphological modification and occlusal adjustment during the manufacturing process or when placed in the oral cavity to create a shape that is in harmony with biological functions, but these procedures result in a rough surface.

[0004] If the surface of a dental restoration is rough, it can cause discoloration and plaque buildup after placement in the oral cavity. Therefore, after shaping and occlusal adjustment of the dental restoration, it is necessary to polish the surface smoothly. In particular, in the case of ceramic dental restorations, insufficient surface polishing can act like a file, and the risk of wearing down the opposing teeth has become clear in recent years. Furthermore, if the surface of a dental restoration is not smooth, it will not have the same natural feel as natural teeth and will not achieve high aesthetics. Furthermore, if the surface condition of the dental restoration is unnatural, it can cause discomfort to the patient's tongue and may interfere with normal movement of the oral mucosa and tongue. For these reasons, polishing dental restorations smoothly is extremely important.

[0005] Dental abrasives that contain abrasive grains and an elastomer binder are commonly used to polish dental restorations. Elastomers have rubber elasticity, making them easy to fit to the area being polished, allowing for efficient polishing.

[0006] Dental restorations are made of a variety of materials, including metals, ceramics, composite resins, and resins, and their mechanical properties vary greatly. Therefore, the mechanical properties of dental abrasives are tailored to suit the material being polished, and abrasives suitable for a variety of materials are available. Among the mechanical properties, the hardness of the abrasive in particular affects the fit to the dental restoration during polishing and the polishing effect.

[0007] One method for adjusting the hardness of dental abrasives that use elastomers as binders is to add plasticizers, which can impart flexibility by penetrating between the elastomer molecules.

[0008] Various compounds are used as plasticizers depending on the application and purpose, but ester compounds are known to be the most commonly used. Phthalate ester compounds are particularly used as ester compounds, with bis(2-ethylhexyl) phthalate being a typical example, and are widely used in food packaging, toys, medical supplies, and other applications. However, in recent years, there has been a trend toward reconsidering the use of phthalate ester compounds as additives due to concerns about their impact on the human body and the environment, and there is growing demand for non-phthalate ester compounds as alternative plasticizers.

[0009] On the other hand, dental abrasives are sometimes used inside the oral cavity, and after use in the oral cavity, they must be cleaned, disinfected, and sterilized to remove, inactivate, and kill any infectious agents before they can be reused on a different patient. A sterilization process is required to completely kill the infectious agent, and various sterilization devices using hydrogen peroxide, gas, heat, etc. are used. Among these, high-pressure steam sterilization (autoclave sterilization) is widely used in dentistry because it can be made compact and can reliably sterilize without handling hazardous substances.

[0010] High-pressure steam sterilization is a sterilization method that kills infectious bacteria and viruses by exposing the infectious agent attached to the object to steam under high pressure. Its advantages include high penetration, thorough sterilization of every corner of the object, and no residual toxicity after sterilization. However, because the object is exposed to harsh conditions such as high humidity, high temperature, and high pressure, the sterilized object may be altered and deteriorated, and its original properties may not be maintained. Dental abrasives containing plasticizers are no exception; high-pressure steam sterilization causes the plasticizer to bleed, significantly reducing the plasticizing effect, and in some cases, the original properties may not be obtained.

[0011] Therefore, plasticizers used in dental abrasives are required to have low impact on the human body and the environment, to be resistant to bleeding even after high-pressure steam sterilization, and to maintain the initial properties of the abrasives as much as possible.

[0012] Patent Document 1 discloses a dental abrasive that uses 4-cyclohexene-1,2-dicarboxylate bis(2-ethylhexyl) as a non-phthalate ester compound as a plasticizer.

[0013] Patent Document 1 shows that a good plasticizing effect can be obtained by applying a non-phthalate ester compound as a plasticizer to resins, mainly vinyl chloride, but does not disclose the actual extent of the effect. Also, the effect on high-pressure steam sterilization is unclear. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Patent Publication No. 2019-81769 Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention aims to provide a dental abrasive that reduces the risk of plasticizer bleeding from the elastomer binder and whose properties do not deteriorate significantly before and after autoclave sterilization, and that is intended to be reused after use in the oral cavity and autoclave sterilization. [Means for solving the problem]

[0016] As a result of extensive research to overcome the above-mentioned problems, the inventors have discovered that it is possible to provide a dental abrasive comprising abrasive grains (A), an elastomer binder (B), and a plasticizer (C), wherein the plasticizer (C) is composed of at least two types of plasticizers, including an epoxy-based plasticizer, which has good mechanical properties and whose properties do not deteriorate significantly before and after high-pressure steam sterilization.

[0017] It is preferable that the plasticizer (C) is composed of at least two kinds of compounds including an epoxy ester compound and epoxy soybean oil. Furthermore, it is preferable that the plasticizer (C) is contained in an amount of 5 to 30 parts by weight based on 100 parts by weight of the elastomer binder (B). In addition, the blending amount of the epoxy ester compound or epoxy soybean oil in the plasticizer (C) is preferably 40 to 80% by weight based on the total weight of the plasticizer (C). [Effects of the Invention]

[0018] The present invention provides a dental abrasive that can achieve a plasticizing effect without using a phthalate ester compound, has good mechanical properties, and does not significantly deteriorate even after autoclave sterilization. It also provides a dental abrasive that can reduce the risk of plasticizer elution from the elastomer binder after autoclave sterilization. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in detail below. The dental abrasive of the present invention comprises abrasive grains (A), an elastomer binder (B), and a plasticizer (C).

[0020] The abrasive grains (A) are made from a variety of materials with different mechanical properties, such as metals, composite resins, zirconia, and resins, which are the materials to be polished for dental prosthetic devices. Therefore, it is necessary to select the most appropriate type and particle size of abrasive grains at the appropriate time.

[0021] The type of abrasive grains (A) is selected optimally depending on the material to be polished, and is not particularly limited, but is preferably one or more selected from diamond, aluminum oxide, silicon carbide, cerium oxide, and boron nitride. For example, if the object to be polished is a hard ceramic material such as zirconia, it is desirable to select diamond. On the other hand, if the object to be polished is a relatively soft material such as metal or composite resin, sufficient polishing effect can be obtained by using silicon carbide or aluminum oxide. The amount of abrasive grains (A) in the entire dental abrasive is preferably 50 to 90% by weight, more preferably 60 to 80% by weight. If the amount of abrasive grains (A) is less than 50% by weight, sufficient polishing effect cannot be obtained. On the other hand, if it exceeds 90% by weight, the elastomer binder cannot sufficiently hold the abrasive grains, resulting in reduced durability.

[0022] The particle size and shape of the abrasive grain (A) used in the present invention are not particularly limited, because they are selected optimally according to the required surface roughness.When selecting the particle size of abrasive grain, for example, if diamond is boron nitride abrasive grain, JIS B4130 is specified, and if aluminum oxide or silicon carbide is R6001 is specified.

[0023] The elastomer binder (B) used in the present invention can be synthetic rubber with rubber elasticity, such as acrylic rubber, silicone rubber, chlorosulfonated polyethylene, urethane rubber, chloroprene rubber, butadiene rubber, butyl rubber, or ethylene-propylene rubber. In particular, butyl rubber, chlorosulfonated polyethylene, and chloroprene rubber are preferred because they are heat-resistant and water-resistant, preventing deterioration of the rubber's physical properties even after high-pressure steam sterilization. The blending amount of the elastomer binder (B) in the entire dental abrasive is preferably 10 to 50 wt%, more preferably 20 to 40 wt%. If the blending amount of the elastomer binder (B) is less than 10 wt%, the elastomer binder cannot adequately hold the abrasive grains, resulting in reduced durability. Furthermore, if the blending amount exceeds 50 wt%, the ratio of the abrasive grains (A) decreases, resulting in insufficient polishing effect.

[0024] The plasticizer (C) used in the present invention is a compound other than a phthalate ester compound, taking into consideration the human body and the environment. Examples include adipic acid esters, cyclohexene dicarboxylic acid esters, trimellitic acid esters, and polyether esters. Among these, cyclohexene dicarboxylic acid esters and trimellitic acid esters are preferred, as they exhibit a plasticizing effect similar to that of DOP, a representative phthalate ester compound.

[0025] In the present invention, two or more types of plasticizer (C) are used as a blend. When the plasticizer (C) is a non-phthalate ester compound alone, for example, a trimellitic acid ester has poorer cold resistance than a phthalate ester compound, and the kneaded product cooled during production becomes hard when re-kneaded, making it difficult to knead and resulting in poor workability. Furthermore, cyclohexene dicarboxylic acid esters have drawbacks such as low heat resistance, easy bleeding of the plasticizer, and a significant decrease in the plasticizing effect over time, making it difficult to use alone.

[0026] To overcome these drawbacks, the dental abrasive of the present invention always incorporates at least one type of epoxy ester compound or epoxy soybean oil as the plasticizer (C), which has an epoxy backbone in its polar moiety. The epoxy ester compound is composed of a polar moiety that is compatible with the elastomer binder and a non-polar moiety that increases the intermolecular distance between the elastomer binder, weakening the intermolecular forces and exhibiting a plasticizing effect. Examples of such compounds include 4,5-epoxycyclohexane-1,2-dicarboxylate (2-ethylhexyl) and 4,5-epoxycyclohexane-1,2-dicarboxylate (di(9,10-epoxystearyl)). Epoxidized soybean oil is produced by reacting soybean oil with peracetic acid or performic acid to generate epoxy groups in its structure. These compounds have high heat resistance and are effective in preventing the plasticizer (C) from bleeding out from the elastomer binder (B) even when exposed to high humidity and high temperatures during high-pressure steam sterilization. By combining them with plasticizers such as epoxy ester compounds or epoxy soybean oil, it is possible to compensate for the drawbacks of trimellitic acid esters and cyclohexene dicarboxylic acid esters and improve their properties as dental abrasives.

[0027] As the plasticizer of the present invention, any other plasticizer may be combined with the epoxy ester compound, epoxy soybean oil, etc., but from the viewpoint of compatibility with various elastomer binders, cyclohexene dicarboxylic acid esters and trimellitic acid esters are preferred.

[0028] The amount of plasticizer (C) to be blended into the dental abrasive of the present invention is preferably in the range of 5 to 30 parts by weight per 100 parts by weight of elastomer binder (B). If the amount is less than 5 parts by weight, a sufficient plasticizing effect is not obtained, and the dental abrasive does not exhibit the flexibility required. Furthermore, when kneading with the abrasive grains (A) and elastomer binder (B) during preparation of the dental abrasive, the plasticizer is hard and difficult to knead, resulting in poor workability. If the amount exceeds 30 parts by weight, the abrasive is too soft, resulting in a poor usability and low durability.

[0029] Of the plasticizers (C) included in the dental abrasive of the present invention, the amount of epoxy ester compound and epoxy soybean oil is preferably 40 to 80% by weight, more preferably 50 to 60% by weight, of the total amount of plasticizer (C). If it is less than 40% by weight, sufficient heat resistance is not obtained, and bleeding of the plasticizer (C) is promoted. If it exceeds 80% by weight, the plasticizing effect of the epoxy ester compound and epoxy soybean oil is too high, resulting in an excessively soft abrasive, poor usability, and low durability.

[0030] The dental abrasive of the present invention can be appropriately blended with various compounding agents commonly used in elastic rubbers, such as colorants and fillers, within the range that does not impair the effects of the present invention. Furthermore, various vulcanizing agents and vulcanization accelerators are appropriately blended to crosslink the elastic rubber. Furthermore, a combination of these components can be blended.

[0031] For example, colorants are blended to improve the visibility of remaining dental abrasives and to identify products. It is desirable to use inorganic pigments such as natural mineral pigments and synthetic inorganic pigments as colorants. Specific examples of such colorants include titanium oxide, iron oxide, cobalt aluminate, and ultramarine.

[0032] Fillers can be blended for the purpose of adjusting the hardness of the dental abrasive and for the purpose of reinforcing the abrasive, and specific examples of fillers include carbon black, thickening silica fine particles, titanium dioxide, diatomaceous earth, aluminum silicate, calcium carbonate, zinc oxide, magnesium oxide, etc. These fillers can be used alone or in combination.

[0033] The dental abrasive of the present invention can be produced by any method, but one example is shown below. The abrasive grains (A), plasticizer (C), and other compounding ingredients are added to the elastomer binder (B) and kneaded in a mixer such as a kneader or kneading roll to produce a kneaded mixture. To prevent scorching of the rubber due to heat generation during kneading, a cooling step may be inserted between each kneading step. The kneaded mixture is then pressure-molded into a desired shape using a hot press. By molding the mixture together with a shaft for attachment to a rotary tool such as a handpiece, a dental abrasive with an integrated shaft can be produced. Molding conditions depend on the elastomer binder (B) used. It is also possible to produce a masterbatch by pre-mixing the elastomer binder (B) with the plasticizer (C) and other compounding ingredients. [Example]

[0034] Examples and comparative examples of the present invention will be described in detail below, but the present invention is not limited to these examples. The dental abrasives exemplified have compositions for polishing dental metals. A kneaded product for molding was obtained by blending and kneading the components in the proportions shown in Table 1. Then, a dental abrasive was obtained by pressure press molding.

[0035] The plasticizers (C) used in this example are as follows: Plasticizer 1: TOTM (trimellitic acid ester compound) Plasticizer 2: DOTH (cyclohexene dicarboxylic acid ester compound) Plasticizer 3: E-145 (epoxy ester compound) Plasticizer 4: E-PS (epoxy ester compound) Plasticizer 5: E-2000H (epoxy compound) Plasticizer 6: DOP (phthalate ester compound)

[0036] [Table 1]

[0037] [Table 2]

[0038] <Preparation of dental abrasives> Abrasive grains (A), plasticizer (C), and other compounding ingredients were added to the elastomer binder (B), and the mixture was kneaded until homogeneous using a mixer such as a kneading roll to produce a kneaded product. If heat generation from the rubber was observed during kneading, a cooling process was inserted before moving on to the next kneading step to prevent scorching of the rubber. The cooling process involved storing the mixture in a refrigerator at 5°C for 10 minutes to ensure sufficient cooling. The resulting kneaded material was pressure-molded into a predetermined shape using a hot press. At that time, it was molded together with the shaft to form a dental abrasive with an integrated shaft. The molding conditions depend on the elastomer binder (B) used. Since chloroprene rubber and chlorosulfonated polyethylene were used as the elastomer binder (B) in this example, the molding conditions were 160°C for 15 minutes for chloroprene rubber and 170°C for 7 minutes for chlorosulfonated polyethylene.

[0039] The dental abrasives thus prepared were evaluated as follows. The workability during production of the dental abrasives was also evaluated. The evaluation results are shown in Table 2.

[0040] <Increase in hardness of dental abrasives before and after sterilization> The samples used were pressure-molded into a φ12 x 1 mm disk shape. One cycle consisted of sterilizing the sample in a high-pressure steam sterilizer (RISA) at 134°C for 4 minutes, and a total of 30 cycles were performed. The samples before sterilization and those after 30 sterilization cycles were placed vertically in a universal testing machine with the 1 mm thick surface facing downwards, and a compressive load was applied at a crosshead speed of 1 mm / min. The compressive load value at 1 mm of displacement was used as an index of hardness. The rate of increase in compressive load was calculated using the following formula. Compression load increase rate [%] = (compression load value after 30 cycles - compression load value before sterilization) / compression load value before sterilization × 100 The calculated increase rate was evaluated according to the following criteria. ◯ indicates that there is no change in the hardness of the abrasive material compared to before sterilization, △ indicates that the hardness of the abrasive material is acceptable but slightly harder than before sterilization, and × indicates that the hardness of the abrasive material is clearly too hard to be tolerated. ○: Increase rate is less than 60% △: Increase rate is 60% to 100% ×: Increase rate exceeds 100%

[0041] <Measurement of plasticizer elution rate before and after sterilization> The samples were pressure-molded into a φ25 x 3 mm disk shape. One cycle consisted of sterilizing the sample in a high-pressure steam sterilizer (RISA) at 134°C for 4 minutes, and a total of 30 cycles were performed. The plasticizer elution rate was calculated using the following formula. Dissolution rate [%] = (sample weight before sterilization - sample weight after 30 cycles) / sample weight before sterilization × 100 The calculated elution rate was evaluated according to the following criteria: Note that, since there was almost no weight change before and after sterilization in the abrasive material containing no plasticizer, it is believed that most of the weight change in this test was due to the elution of plasticizer, and therefore the above formula was defined as the elution rate of plasticizer. In the case of ◎, the amount of plasticizer eluted is less than that of DOP, and the plasticizer continues to exist stably in the elastomer binder; ◯, the amount of plasticizer eluted is about the same as that of DOP; △, although acceptable, the amount of plasticizer eluted is slightly more than that of DOP; and ×, the amount eluted is even more, and the plasticizer lacks stability. ◎: Dissolution rate is 2.0% or less ○: Dissolution rate is over 2.0% to 2.5% or less △: Dissolution rate is over 2.5% to 3.0% or less ×: Dissolution rate exceeds 3.0%

[0042] <Measurement of wear amount of dental abrasives> A specimen was prepared that was integrated with the axis and a conical working part of φ3×7mm. The specimen was subjected to a test at 20,000 min -1 Cobalt-chromium alloy was ground under the conditions of 1000 kJ / min, 20 seconds, and 2 to 2.5 N. The wear amount was calculated using the following formula. Abrasion amount [mg] = sample weight before test - sample weight after test The calculated wear amount was evaluated according to the following criteria. In the case of ◯, the product has durability that can withstand use, but in the case of ×, the product has a large amount of wear and is not durable enough to withstand use. ○: Wear amount is 10 mg or less ×: Wear amount exceeds 10 mg

[0043] <Evaluation of the usability of dental abrasives> The actual usability of the various evaluation samples was confirmed. To evaluate the usability, a 12mm diameter x 1.5mm thick disc-shaped dental abrasive with a shaft was prepared as a sample, and the surface of a 15mm x 30mm x 1mm cobalt chromium alloy plate was polished for 20,000 min before and after sterilization. -1 The abrasive was polished with a load of approximately 1N for 30 seconds, and the vibration, hardness, and fit of the abrasive and cobalt-chrome plate during contact were measured to confirm the differences in these indicators before and after sterilization. The surface of the cobalt-chrome alloy was prepared in advance with #120 waterproof abrasive paper. A dental abrasive using a phthalate ester compound (DOP) was used as a comparison, and evaluation was based on the following criteria. In the case of ◎, there was little change in the feel of the sample before and after sterilization compared to DOP, and the vibration, hardness, and fit while in contact with the cobalt-chromium alloy were maintained both before and after sterilization. Also, ○ indicated that the feel of the sample was about the same as DOP, and although there was a slight difference in the feel of the sample before and after sterilization, it was at a level that did not pose any problems in use. △ indicated that the feel of the abrasive material after sterilization was slightly worse than DOP, and × indicated that the feel of the sample was clearly worse than DOP. ◎: Feels better than DOP 〇: Usability is about the same as DOP △: Usability is slightly worse than DOP ×: Usability is worse than DOP

[0044] <Workability during manufacturing of dental abrasives> The workability during the production of various evaluation samples was confirmed. The comparison was based on the workability when produced using a phthalate ester compound (DOP), and the evaluation was based on the following criteria. Here, workability refers to the ease of work in all steps in the production of dental abrasives (mixing, molding, and other processes necessary for producing the abrasive), and is particularly evident in the process of mixing the elastomer binder with abrasive grains, plasticizers, and other ingredients to form a kneadable sheath and a desired shape. ◎ indicates that the abrasive is easier to produce than DOP. 〇 indicates that the ease of production is the same as DOP, △ indicates that the process is slightly more difficult than DOP and is slightly less processable, and × indicates that the process is clearly worse than DOP and is more difficult to produce. ◎: Workability is better than DOP 〇: Workability is the same as DOP △: Workability is slightly worse than DOP ×: Workability is worse than DOP

[0045] The dental abrasives of Examples 1 to 12 had the optimal amount of plasticizer (C) relative to the elastomer binder (B) and the optimal amount of epoxy ester compound or epoxy soybean oil in the plasticizer (C), and all evaluation results were good.

[0046] Comparative Examples 1 to 10 were inferior to the Examples because the amount of plasticizer (C) relative to the elastomer binder (B) and the amount of epoxy ester compound or epoxy soybean oil in the plasticizer (C) were not optimal. [Industrial Applicability]

[0047] The present invention can be used as a dental abrasive for polishing dental prosthetic devices such as ceramics, metals, and composite resins.

Claims

1. The abrasive grains (A), the elastomer binder (B), and the plasticizer (C) are included. A dental abrasive, characterized in that the plasticizer (C) comprises at least two kinds of plasticizers including an epoxy-based plasticizer.

2. 2. The dental abrasive according to claim 1, wherein the plasticizer (C) comprises an epoxy ester compound or epoxy soybean oil.

3. 2. The dental abrasive according to claim 1, wherein the plasticizer (C) is contained in an amount of 5 to 30 parts by weight per 100 parts by weight of the elastomer binder (B).

4. 2. The dental abrasive according to claim 1, wherein the amount of the epoxy ester compound or epoxy soybean oil in the plasticizer (C) is 40 to 80% by weight based on the total weight of the plasticizer (C).

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