JP2024144082A - Dental abrasives - Google Patents

Abstract

To provide a dental polisher that can address from intermediate final polishing to final polishing with a single dental polisher in polishing of dental restoration and has excellent working efficiency.SOLUTION: A dental polisher comprises a plurality of laminated grindstone layers. Each of the grindstone layers includes a polishing abrasive grain (A) and a binder (B). Respective grindstone layers are separable from each other.SELECTED DRAWING: Figure 1

Description

The present invention relates to a dental abrasive for polishing dental restorations made of ceramics, metals, composite resins, resins, etc.

When undergoing dental treatment, if a tooth has a 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 a variety of materials, including ceramics, metals, and composite resins.

Dental restorations require shaping and occlusal adjustment during the manufacturing process or when they are set in the oral cavity to create a shape that is in harmony with the body's functions, but these procedures result in a rough surface.

If the surface roughness of a dental restoration is rough, it will not have the same natural feel as natural teeth after being placed in the mouth, and will not be highly aesthetic. Furthermore, areas with rough surfaces can have adverse effects such as staining and plaque adhesion. For these reasons, it is extremely important to polish dental restorations smoothly.

After shaping and occlusal adjustment, when the surgeon (dentist or dental technician) polishes the dental restoration, he or she often attaches an abrasive to a micromotor and polishes it manually while rotating it. In order to achieve an appropriate surface roughness, it is common to polish the surface by gradually changing the abrasive from coarse to fine. For example, the surface roughness is first reduced to a certain degree using a semi-finishing abrasive. Next, the semi-finishing abrasive is removed from the micromotor, and a finishing abrasive is attached to the micromotor, followed by further polishing to the final surface properties. In this way, it is necessary to attach and detach multiple abrasives to the micromotor during polishing, which is a complicated task for the surgeon and takes a lot of time.

When abrasives are used in dental clinics, they become contaminated after use in the oral cavity. Some abrasives can be reused by removing bacteria through regeneration processing, but in recent years, disposable products have also been sold due to increased awareness of hygiene, such as the risk of cross-infection. However, disposing of multiple abrasives after a single use is also a large economic burden. Therefore, it is expected that the demand for disposable abrasives that can be used with as few pieces as possible will continue to increase from both hygiene and economic standpoints.

Patent Document 1 describes a two-layered cup-shaped grinding wheel. The cup-shaped grinding wheel described in Patent Document 1 has a structure in which abrasive grains of different grain sizes are sintered into two layers and attached to the shank. This cup-shaped grinding wheel is characterized by the fact that rough grinding is performed on the moving side of the grinding wheel (coarse grain side), and fine grinding is performed by fine abrasive grains on the rear side of the processing progress (fine grain side), resulting in a smooth processed finished surface. However, the cup-shaped grinding wheel described in Patent Document 1 has a structure in which the rough grinding wheel and the fine grinding wheel are two-layered and cannot be detached, and the rough grinding and fine grinding are controlled by the moving direction of the grinding wheel. For this reason, when polishing small and complex irregularities such as the occlusal surface of a molar tooth, there is a risk of coarsening again if the rough grinding wheel accidentally comes into contact after fine grinding, making precise polishing difficult.

Japanese Utility Model Application Publication No. 6-42064

The objective of the present invention is to provide a dental abrasive that can be used for polishing dental restorations from semi-finishing to finish polishing with a single dental abrasive, and that provides good work efficiency.

The present inventors conducted extensive research to overcome the above problems and have arrived at the present invention.
That is, the dental abrasive of the present invention is composed of a plurality of stacked grinding stone layers, each of which contains abrasive grains (A) and a bonding material (B), and each grinding stone layer is separable from the other layers.

The dental abrasive of the present invention allows a single dental abrasive to be used for everything from semi-finishing to finish polishing without having to attach and detach multiple abrasives to a micromotor or the like, dramatically improving work efficiency.

1 is a schematic cross-sectional view showing a cross-sectional structure including a rotation axis of a dental abrasive according to embodiment 1. FIG. 2 is an enlarged schematic cross-sectional view of each grinding stone layer of the dental abrasive of FIG. 1. FIG. 13 is a schematic front view of a second grinding wheel layer to which a dimple shape is imparted as an example of physical fitting. FIG. 13 is a schematic front view of a second grinding wheel layer having a lattice shape as an example of physical engagement. FIG. 13 is a schematic front view of a second grinding wheel layer having a lattice shape as an example of physical engagement. FIG. 13 is a schematic front view of a second grinding wheel layer having a slit shape as an example of physical engagement. FIG. 13 is a schematic front view of a second grinding wheel layer having a slit shape as an example of physical engagement. FIG. 13 is a schematic front view of a second grinding wheel layer having a slit shape as an example of physical engagement. A schematic cross-sectional view showing a cross-sectional structure including a rotation axis of a dental abrasive according to embodiment 2. A schematic oblique view showing an example of a dental abrasive integrated with a shaft in embodiment 3. A schematic oblique view showing a modified example of the dental abrasive of embodiment 3, which is an example of a dental abrasive with a detachable shaft. 1 is a schematic cross-sectional view showing the cross-sectional structure of a dental abrasive having a separating agent layer between a first grinding stone layer and a second grinding stone layer. FIG. 2 is a schematic front view showing a bullet-shaped dental abrasive. FIG. 2 is a schematic front view showing a spindle-shaped dental abrasive. FIG. 2 is a schematic front view showing a cup-shaped dental abrasive. Table 1 shows the evaluation results of the dental abrasives of Examples 1 to 11.

The dental abrasive according to the first aspect is composed of multiple stacked grinding stone layers, each of which contains abrasive grains (A) and a bonding material (B), and each of which is separable from the others.

In the dental abrasive of the second aspect, in the first aspect described above, the binder (B) in at least one of the multiple grinding stone layers may contain an elastomeric material.

The dental abrasive according to the third aspect is the dental abrasive according to the first or second aspect above, which may have a rotating shaft and multiple grinding stone layers, each layer stacked from the center of the rotating shaft in the outer circumferential direction.

In the dental abrasive of the fourth aspect, in the third aspect, the average particle size of the abrasive grains (A) in the grinding layer on the outer periphery of each grinding stone layer may be larger than the average particle size of the abrasive grains (A) in the grinding layer on the inner periphery of each grinding stone layer.

In the dental abrasive according to the fifth aspect, in any one of the first to fourth aspects, two adjacent grinding stone layers among the multiple grinding stone layers may be held by physical interlocking.

In the dental abrasive according to the sixth aspect, in any one of the first to fifth aspects, two adjacent grinding stone layers among the multiple grinding stone layers may be held together via an adhesive layer.

In the seventh aspect of the dental abrasive, in any one of the first to sixth aspects, two adjacent grinding stone layers among the multiple grinding stone layers may be held together via a separating agent layer.

The dental abrasive according to the embodiment will be described below with reference to the attached drawings. Note that in the drawings, substantially identical components are given the same reference numerals.

(Embodiment 1)
Fig. 1 is a schematic cross-sectional view showing a cross-sectional structure including a rotation shaft 6 of a dental abrasive 10 according to embodiment 1. Fig. 2 is an enlarged schematic cross-sectional view showing the cross sections of each grinding stone layer 1, 2 of the dental abrasive of Fig. 1.
The dental abrasive of embodiment 1 is composed of multiple stacked grinding stone layers, each of which contains abrasive grains (A) and a bonding material (B), and each grinding stone layer is separable from the other layers.
With this dental abrasive, the multiple stacked grinding stone layers can be separated in sequence, allowing intermediate polishing to finish polishing to be performed with a single dental abrasive, thereby dramatically improving work efficiency.

The components that make up this dental abrasive are described below.

<Grinding Stone Layer>
This dental abrasive 10 is constructed by laminating a plurality of grinding stone layers 1 and 2, and the number, material, and shape of the grinding stone layers are arbitrary. In the case of a dental abrasive 10 having a two-layer structure as shown in FIG. 1 as an example of a dental abrasive, for example, the first grinding stone layer 1 is located on the outermost surface of the dental abrasive and mainly functions for semi-finish polishing. The second grinding stone layer 2 is located inside the first grinding stone layer 1 and functions for final polishing. It is preferable that the first grinding stone layer 1 and the second grinding stone layer 2 are in physical contact with each other so that the first grinding stone layer 1 can be detached after the semi-finish polishing with the first grinding stone layer 1. In addition, it is more preferable that the first grinding stone layer 1 has flexibility so that the first grinding stone layer 1 can be easily detached from the second grinding stone layer 2.
1, the first grinding stone layer 1 covers almost the entire outer peripheral surface except for the bottom surface of the second grinding stone layer 2. The first grinding stone layer 1 prevents the second grinding stone layer 2 for final polishing from being exposed, so that the second grinding stone layer 2 can be prevented from being mistakenly used during semi-finish polishing with the first grinding stone layer 1.

Examples of methods for bonding (adhering) the grinding stone layers 1 and 2 to each other include, for example, a method of physically pressing the layers together, a method of bonding (adhering) the layers together by physical fitting, a method of bonding the grinding stones together using an adhesive or the like, a method of bonding the layers together by the gripping force of the bonding materials of adjacent grinding stone layers 1 and 2, and so on. On the other hand, the grinding stone layers 1 and 2 must be separable.

For example, in the case of a dental abrasive with a two-layer structure, the first and second grinding stone layers can be held together by residual compressive stress when the first grinding stone layer is molded onto the second grinding stone layer by hot press molding or the like, chemical adhesion between the binder of the first grinding stone layer and the binder of the second grinding stone layer, or physical fusion by heating. This dental abrasive is characterized in that after use of the first grinding stone layer, the first grinding stone layer is detached from the second grinding stone layer and used. Due to its characteristics, it is preferable for the grinding stone layers to be held together by adhesion (adhesion) between the grinding stone layers due to the gripping force between the binders (B) of adjacent grinding stone layers, or by residual compressive stress.

In addition, it is preferable that the multiple grinding stone layers are formed in a laminated shape from the center of the rotation axis to the outer periphery. In this case, as shown in FIG. 2, it is preferable that the average particle diameter of the abrasive grains 11 (A) in the grinding stone layer 1 on the outer periphery of each grinding stone layer is larger than the average particle diameter of the abrasive grains 21 (A) in the grinding stone layer 2 on the inner periphery. For example, in the case of a dental abrasive having a two-layer structure, it is possible to have a structure having a first grinding stone layer 1 used for medium finishing on the outermost surface and a second grinding stone layer 2 used for finish polishing inside the first grinding stone layer. In this case, since the first grinding stone layer 1 is used for medium finishing polishing, it is necessary to have a higher grinding ability than the second grinding stone layer 2, so it is preferable that the particle diameter of the abrasive grains 11 (A) used in the first grinding stone layer 1 is larger than the particle diameter of the abrasive grains 21 (A) used in the second grinding stone layer 2. Furthermore, by making the particle size of the abrasive grains 11 (A) used in the first grinding layer 1 larger than the particle size of the abrasive grains 21 (A) used in the second grinding layer 2, the unevenness increases, and in addition to the retention due to the residual compressive stress, the gripping force of the first grinding layer increases, making it less likely for the first grinding layer to fall off from the second grinding layer even when used at high speed rotation.

Furthermore, in order to further reduce detachment or freewheeling of the grinding stone layers due to high speed rotation and high load, it is more preferable to hold the grinding stone layers together by a physical interlocking force. To achieve physical interlocking, for example, slits or lattice-like grooves or uneven shapes can be provided on the surface of the inner grinding stone layer, but there are no limitations on the shape or size as long as the necessary interlocking force can be obtained.

Fig. 3 is a schematic front view of the second grinding wheel layer 2 to which a dimple shape 7a is imparted as an example of physical fitting. Figs. 4A and 4B are schematic front views of the second grinding wheel layer 2 to which lattice shapes 7b and 7c are imparted as an example of physical fitting. Figs. 5A to 5C are schematic front views of the second grinding wheel layer 2 to which slit shapes 7d, 7e, and 7f are imparted as an example of physical fitting.
As the physical fitting, for example, as shown in Figures 3, 4A, 4B, 5A to 5C, the second grinding wheel layer 2 on the inner circumference side may have a dimple shape 7a, a lattice shape 7b, 7c, a slit shape 7d, 7e, 7f, etc. Also, the first grinding wheel layer 1 and the second grinding wheel layer 2 may be held by screwing. For example, the physical fitting may be performed by providing a portion where the first grinding wheel layer 1 and the second grinding wheel layer 2 overlap in the direction along the rotation axis 6, and screwing (not shown) in the opposite direction to the rotation direction.
By providing a physical fit between the first grinding stone layer 1 and the second grinding stone layer 2, the first grinding stone layer 1 and the second grinding stone layer 2 provided thereon can be held by the physical fit. In addition, this physical fit can suppress free rotation of the first grinding stone layer 1 relative to the second grinding stone layer 2.

FIG. 8 is a schematic cross-sectional view showing the cross-sectional structure of a dental abrasive 10 d in which a separating agent layer 8 is provided between a first grinding stone layer 1 and a second grinding stone layer 2 .
After using the first grinding wheel layer 1 of the dental abrasive 10d, a separating agent may be applied between the first grinding wheel layer 1 and the second grinding wheel layer 2 in anticipation of easy detachment when the first grinding wheel layer 1 is detached from the second grinding wheel layer 2. When the binder of the first grinding wheel layer 1 and the binder of the second grinding wheel layer 2 are the same material or materials of the same type, the first grinding wheel layer 1 and the second grinding wheel layer 2 may be easily adhered to each other. Therefore, in the above case, for example, as shown in FIG. 8, a separating agent layer 8 in which the separating agent is layered may be provided between the first grinding wheel layer 1 and the second grinding wheel layer 2, and the first grinding wheel layer 1 and the second grinding wheel layer 2 may be held via the separating agent layer 8.
The separating agent used in the separating agent layer 8 is not particularly limited, and an optimal one may be used in consideration of compatibility with the material used for the binder. Examples of separating agents include inorganic powders such as talc, zeolite, bentonite, and calcium carbonate, polymer beads, and zinc stearate.

On the other hand, when the first grinding wheel layer 1 and the second grinding wheel layer 2 are made of different materials, for example, when one is made of an elastomer material and the other is made of a glass material, an adhesive layer may be provided between the two and the first grinding wheel layer 1 and the second grinding wheel layer 2 may be held together via the adhesive layer.
The adhesive used in the adhesive layer is not particularly limited, and an optimal adhesive may be used taking into consideration compatibility with the material used for the binder. Examples of adhesives that may be used include vinyl acetate-based, nitrile rubber-based, epoxy resin-based, and acrylic resin-based adhesives.

The first grinding wheel layer 1 and the second grinding wheel layer 2 may be held together by appropriately combining the above-mentioned physical interlocking, the above-mentioned separating agent layer, and the above-mentioned adhesive layer. For example, the physical interlocking and the separating agent layer may be combined, or the physical interlocking and the adhesive layer may be combined. Furthermore, the separating agent layer and the adhesive layer may be combined. Alternatively, the physical interlocking, the separating agent layer, and the adhesive layer may be combined.
Furthermore, the first grinding wheel layer 1 may be, but is not limited to, separable from the second grinding wheel layer 2. For example, the first grinding wheel layer 1 may be detachably provided on the second grinding wheel layer 2 so that the first grinding wheel layer 1 can be reused after being separated.

<Overall shape of dental abrasive>
Fig. 9A is a schematic front view of a bullet-shaped dental abrasive 10e, Fig. 9B is a schematic front view of a spindle-shaped dental abrasive 10f, and Fig. 9C is a schematic front view of a cup-shaped dental abrasive 10g.
The shape of the dental abrasives 10, 10e, 10f, and 10g is not particularly limited, but dental abrasives are generally used while being rotated. Therefore, the overall shape of the dental abrasives consisting of a laminate of a plurality of grinding stone layers may generally be a shape that is rotationally symmetrical about the rotation axis 6, such as a cylindrical shape, a conical shape, a parabolic revolution shape, a bullet shape (FIG. 1, FIG. 9A), a spindle shape (FIG. 9B), or a cup shape (FIG. 9C). Furthermore, the dental abrasives 10, 10e, 10f, and 10g are preferably selected from the range of, for example, 2 to 10 mm for the maximum diameter about the rotation axis 6, and 5 to 30 mm for the height, which is the length along the direction of the rotation axis 6.

<Polishing grains (A)>
The dental prosthetic device to be polished is made of various materials with different mechanical properties, such as metal, composite resin, zirconia, resin, etc. For this reason, it is necessary to select the type and particle size of the polishing abrasive (A) that are optimal for the object to be polished at the appropriate time.

The type of abrasive grains (A) is selected optimally each time depending on the material to be polished, and is not particularly limited. For example, it is preferable to select one or more 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 as the polishing grain (A). On the other hand, if the object to be polished is a relatively soft material such as metal or composite resin, a sufficient polishing effect can be obtained by using silicon carbide or aluminum oxide as the polishing grain (A).

The particle size and shape of the abrasive grains (A) used are not particularly limited, as the optimum ones are selected depending on the required surface roughness. For example, abrasive grains (A) with an average particle size of 30 to 200 μm are often used for rough polishing, and abrasive grains (A) with an average particle size of 1 to 30 μm are often used for finish polishing. The particle size of the abrasive grains is selected based on the average particle size. The average particle size refers to the median diameter (d50), and can be determined using a general particle size distribution measuring device. There are various particle size distribution measuring devices that use various measurement principles, one example of which is a particle size distribution measuring device that uses the electrical resistance method.

<Binding material (B)>
The binder (B) may be an elastomer material, a glass-based material, a resin-based material, or the like. In terms of adhesion (adhesion) between the grindstone layers and operability during separation, an elastomer material is particularly preferably used. The elastomer material used is not particularly limited, but may be synthetic rubber or natural rubber having rubber elasticity, such as acrylic rubber, silicone rubber, chlorosulfonated polyethylene, isoprene rubber, urethane rubber, chloroprene rubber, butadiene rubber, butyl rubber, ethylene-propylene rubber, and urethane rubber. Examples of the glass-based material include oxide glass such as borosilicate glass, non-oxide glass such as chalcogenide glass, and feldspar. Examples of the resin-based material include epoxy resin, polyolefin resin, and polyvinyl chloride.

When an elastomer material is used as the binder (B), it is preferable that the two grinding stone layers that come into contact with each other are composed of different elastomer materials. This is because when grinding stone layers made of the same type of elastomer material come into contact with each other, adjacent grinding stone layers may adhere to each other due to heating during molding, making them difficult to separate. When adjacent grinding stone layers made of the same type of elastomer material are used, adhesion during molding can be prevented by changing the grain size or material of the abrasive grains in each grinding stone layer.

The mixing ratio of the abrasive grains to the binder used can be arbitrary, but in order to balance abrasiveness and durability, it is preferable that the mixing ratio by weight of the abrasive grains to the binder is, for example, 90:10 to 30:70.

When an elastomer material or a resin-based material is used as the binder (B), various compounding agents that are often used in elastic rubbers, such as colorants, fillers, and plasticizers, can be appropriately compounded within a range that does not impede the effects of the present invention. In addition, various vulcanizing agents and vulcanization accelerators may be appropriately compounded to crosslink the elastic rubber. Furthermore, these components can be compounded in combination.

For example, colorants are blended to improve the visibility of remaining dental abrasives and to identify products. It is preferable 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.

Fillers can be added to adjust the hardness of dental abrasives and to provide reinforcement. Specific examples of fillers include carbon black, thickening silica particles, titanium dioxide, diatomaceous earth, aluminum silicate, calcium carbonate, zinc oxide, and magnesium oxide. These fillers can be used alone or in combination.

When a glass-based material is used for the binder (B), various compounding agents that are often used in vitrified grinding wheels, such as colorants and fillers, can be appropriately mixed within a range that does not impede the effects of the present invention. In addition, these components can be mixed in combination.

The coloring agent is added, for example, to improve the visibility of the remaining dental abrasive and to identify the product, as described above. Metal oxides such as cobalt oxide, copper oxide, chromium oxide, nickel oxide, and manganese oxide are preferably used as coloring agents.

Fillers are used to adjust the hardness of dental abrasives and to form pores that prevent clogging. Examples of fillers include hollow bodies made of graphite, silica, calcium carbonate, alumina glass, etc.

(Embodiment 2)
FIG. 6 is a schematic cross-sectional view showing a cross-sectional structure including a rotation shaft 6 of a dental abrasive 10a according to the second embodiment.
This dental abrasive 10a differs from the dental abrasive of the first embodiment in that it uses a second grinding stone layer 2 having a dimple pattern 7a as shown in FIG.
Since the second grinding wheel layer 2 has a dimple shape, the first grinding wheel layer 1 and the second grinding wheel layer 2 can be held by physical fitting. This makes it possible to prevent the first grinding wheel layer 1 from spinning freely relative to the second grinding wheel layer 2, increases the gripping force of the first grinding wheel layer 1, and makes the first grinding wheel layer 1 less likely to fall off the second grinding wheel layer 2 even during high-speed rotation.

(Embodiment 3)
Fig. 7A is a schematic perspective view showing an example of a dental abrasive 10b integrated with a shaft 3 according to embodiment 3. Fig. 7B is a schematic perspective view showing an example of a dental abrasive 10c according to a modified example of embodiment 3.
The dental abrasive 10b according to the third embodiment is integrated with the shaft 3 for attachment to a dental handpiece (not shown) as shown in FIG. 7A. Alternatively, the dental abrasive 10c according to the modified example has a shaft detachable portion 4 to which the shaft 5 can be detached as shown in FIG. 7B. The method of fixing the shaft 3 to the dental abrasive 10b is not particularly specified, but an example of a dental abrasive having two layers laminated is shown below. First, in the dental abrasive 10b according to the third embodiment, the shaft 3 is inserted in advance into the center of the bottom surface of the second grinding stone layer 2 and fixed by pressure bonding or adhesive. In addition, when the shaft 5 is made detachable as in the dental abrasive 10c according to the modified example, the shaft detachable portion 4 having a hole similar to the shaft 5 to be inserted is formed in the center of the bottom surface of the second grinding stone layer 2, and the shaft 5 can be appropriately detached during use.

<Method of manufacturing dental abrasive>
The dental abrasive material according to the present invention can be manufactured by any method. As an example of an abrasive material having two laminated layers, the following describes a case in which an elastomer material is used as the bonding material (B) of the first grinding stone layer and the second grinding stone layer.
(1) First, the second grinding wheel layer is molded into a predetermined shape. First, the polishing grains (A) and other compounding agents are added to the elastomer material, and the mixture is kneaded in a mixer such as a kneader or a kneading roll to produce a kneaded product. Then, the kneaded product is pressurized and molded into a predetermined shape by a hot press. At that time, it is possible to produce a dental abrasive material with an integrated shaft by molding it together with a shaft for mounting on a rotary tool such as a handpiece. In addition, it is also possible to apply an uneven shape or slit processing to the surface of the second grinding wheel layer in order to provide physical interlocking with the first grinding wheel layer. The molding conditions depend on the elastomer material used.

(2) Next, the first grinding stone layer is prepared by the same method as the second grinding stone layer, and a kneaded material consisting of an elastomer material, abrasive grains (A), and other compounding agents is prepared.The kneaded material that forms the first grinding stone layer is then pressure molded into a predetermined shape by a hot press.At that time, the second grinding stone layer is covered with the kneaded material of the first grinding stone layer and pressure molded to adhere the first grinding stone layer and the second grinding stone layer to each other, thereby making it possible to prepare the dental abrasive according to the first to third embodiments.
If necessary, a release agent may be applied to the surface of the second grinding stone layer before covering the surface of the second grinding stone layer with the kneaded material of the first grinding stone layer. When preparing a dental abrasive having three or more grinding stone layers, the above steps can be repeated.

As another example, when a glass material is used as the binder for the first grinding layer and an elastomer material is used as the binder for the second grinding layer, the first grinding layer is first produced, and then the mixture constituting the second grinding layer is pressure molded inside the first grinding layer, and the first grinding layer and the second grinding layer are adhered to each other, thereby producing the dental abrasive according to the first to third embodiments. When producing the grinding layer using a glass-based material, a mixture consisting of the glass-based material, abrasive grains (A) and other compounding agents is produced, and then the mixture is pressure molded into a predetermined shape, and then the glass-based material is sintered by firing at a high temperature of about 600 to 1500°C to obtain a predetermined grinding layer. The firing temperature and time depend on the glass-based material used.

The following provides a detailed description of examples and comparative examples, but the present invention is not limited to these examples. The dental abrasives shown are compositions for polishing dental composite resins. Table 1 in Figure 10 shows the compounding compositions of the first grinding wheel layer and the second grinding wheel layer. The components were compounded and kneaded to obtain a molded mixture for use in each grinding wheel layer. After that, the ones using an elastomer material as a binder were press molded, and the ones using a glass binder were press molded and then sintered to obtain dental abrasives.

<Preparation of dental abrasive (second grinding stone layer)>
The abrasive grains (A) and other compounding ingredients were added to the elastomer material, and the mixture was kneaded until it was uniform using a mixer such as a kneading roll to prepare a kneaded product. The obtained kneaded product was pressurized and molded into a predetermined shape using a hot press. At that time, it was molded together with the shaft, and the shaft was made into a state of being integrated. The molding conditions depend on the elastomer material used. The elastomer material and molding conditions used in this example are as follows. In addition, a sample that was pressurized and molded into a bullet shape of φ5×8 mm was used. In addition, as another example, in order to improve the physical fit between the first grinding wheel layer and the second grinding wheel layer, a dimple 7a (FIG. 3), a lattice pattern 7b, 7c (FIG. 4A, FIG. 4B), and slits 7d, 7e, 7f (FIG. 5A, FIG. 5B, FIG. 5C) were also provided on the surface of the second grinding wheel layer.
Chlorosulfonated polyethylene: molding conditions were 170°C and 7 minutes.
Silicone rubber: molding conditions were 120°C for 5 minutes.

<Preparation of dental abrasive (first grinding stone layer)>
The abrasive grains (A) and other compounding ingredients were added to the elastomer material, and the mixture was kneaded until it was uniform using a mixer such as a kneading roll to prepare a kneaded product. The kneaded product obtained was pressurized and molded into a predetermined shape using a hot press. At that time, the first grindstone layer was molded so as to cover the second grindstone layer, and a dental abrasive material in which the first grindstone layer and the second grindstone layer were in close contact with each other was obtained. The molding conditions depend on the elastomer material used.
In another example, in order to improve the adhesion between the first grindstone layer and the second grindstone layer, a vinyl acetate adhesive was applied to the second grindstone layer before molding the first grindstone layer. The elastomer material and molding conditions used in this example are as follows. In addition, a sample molded under pressure into a bullet shape of φ7×11 mm was used.
Chlorosulfonated polyethylene: molding conditions were 170°C and 7 minutes.
Silicone rubber: molding conditions were 120°C for 5 minutes.
Urethane rubber: molding conditions were 170°C for 7 minutes.

(Modification)
As another example, a case where the first grinding wheel layer uses a glass-based material and the second grinding wheel layer uses an elastomer material will be described.

<Preparation of dental abrasive (first grinding stone layer)>
The glass-based material was mixed with the abrasive grains (A) and other compounding agents, and the mixture was kneaded until it was uniform using a mixer such as a crusher to produce a kneaded product. The kneaded product was pressurized and molded (primary molding) into a predetermined shape using a hot press. The mixture was then completely sintered in an electric furnace to produce a first grinding wheel layer. The glass-based material used in the examples, the molding conditions (primary molding) using the hot press, and the firing conditions in the electric furnace are as follows. The first grinding wheel layer produced was in the shape of a bullet with a diameter of 7 mm x 11 mm, and a cavity with a diameter of 5 mm x 8 mm was formed inside so that the second grinding wheel layer could be molded.
Borosilicate glass: molding conditions were 170°C for 10 minutes, and firing conditions were 700°C for 2 hours.
Feldspar: Molding conditions were 170°C for 10 minutes, and firing conditions were 1300°C for 5 hours.

<Preparation of dental abrasive (second grinding stone layer)>
The abrasive grains (A) and other compounding ingredients were added to the elastomer material, and the mixture was kneaded until it was uniform using a mixer such as a kneading roll to produce a kneaded product. The resulting kneaded product was filled into the inside of the first grindstone layer, and molded under pressure using a hot press so that the surface of the second grindstone layer was in close contact with the inside of the first grindstone layer. At that time, a holding hole was formed inside the bottom surface of the second grindstone layer to allow a separate shaft to be detached. The molding conditions depend on the elastomer material used. The elastomer material (B) and molding conditions used in this example are as follows.
Silicone rubber: molding conditions were 120°C for 5 minutes.

<Preparation of test specimen>
The test specimens were prepared as follows: First, a stainless steel ring with an inner diameter of 15 mm and a thickness of 2 mm was placed on a glass slide, and dental composite resin (Beautifil 2, Matsukaze Co., Ltd.) was filled in and polymerized in the usual manner to obtain a cylindrical test specimen.

The dental abrasives prepared were evaluated as follows. The evaluation results are shown in Table 1 in Figure 10.

<Retention of the first grindstone layer>
The prepared sample was used to polish a dental composite resin at a rotation speed of 15,000 rpm for 10 seconds at 3 N, and the retention of the first grinding stone layer was evaluated according to the following evaluation criteria A to D.
In the case of A, the first grindstone layer did not fall off during grinding even after repeated grinding two or more times, and no loosening of the first grindstone layer was confirmed after grinding. In the case of B, the first grindstone layer did not fall off from the second grindstone layer during the first grinding, and no loosening of the first grindstone layer was confirmed after grinding. In the case of C, the first grindstone layer did not fall off from the second grindstone layer during the first grinding, but loosening of the first grindstone layer was confirmed after grinding. In the case of D, the first grindstone layer fell off from the second grindstone layer during the first grinding, and it was not usable. In this test, an evaluation of C or higher was considered to be a pass.
A: The first grinding layer does not fall off even after two or more polishing cycles, and there is no loosening of the first grinding layer after polishing. B: The first grinding layer does not fall off during the first polishing cycle, and there is no loosening of the first grinding layer after polishing. C: The first grinding layer does not fall off during the first polishing cycle, and there is loosening of the first grinding layer after polishing. D: The first grinding layer falls off during the first polishing cycle.

<Removability of the first grinding wheel layer>
When the first grinding stone layer of the prepared sample was manually detached from the second grinding stone layer, the releasability of the first grinding stone layer was evaluated according to the following evaluation criteria A to D.
In the case of A, the first grinding layer can be easily detached, and no damage such as chipping is observed in the second grinding layer, in the case of B, no damage such as chipping is observed in the second grinding layer when the first grinding layer is detached, in the case of C, the second grinding layer is in a usable state when the first grinding layer is detached, but some chipping occurs, and in the case of D, the second grinding layer is clearly damaged after the first grinding layer is detached, and is in an unusable state. In this test, an evaluation of C or higher was considered to be a pass.
A: The first grinding layer can be easily detached, and the second grinding layer is not damaged. B: The first grinding layer can be detached, and the second grinding layer is not damaged. C: The first grinding layer can be detached, but there is resistance, or after the first grinding layer is detached, a chip or the like occurs in part of the second grinding layer. D: The first grinding layer cannot be detached, or after the first grinding layer is detached, the second grinding layer is clearly damaged.

The dental abrasives according to Examples 1 to 9 passed all the evaluation items, and good results were obtained. In particular, Examples 1 and 2 achieved good releasability by adopting flexible silicone rubber as the binder (B) used in the first grinding layer. In addition, Examples 6 to 9 showed good retention by providing physical interlocking or applying adhesive, and the first grinding layer did not fall off even after repeated grinding two or more times, and no loosening of the first grinding layer was observed. Example 10 had no problems in use, but there was no difference in the grain size of the abrasive grains used in the first and second grinding layers, and when the first grinding layer was peeled off from the second grinding layer, it was possible to detach it, but there was a sense of resistance, and even after detachment, chipping occurred in part of the working part, and it was inferior to Examples 1 to 9. In addition, in Example 11, there were no problems in use, but the grain size of the abrasive grains used in the first grinding stone layer was smaller than that of the second grinding stone layer, and the first grinding stone layer was found to loosen during grinding with the first grinding stone layer, and the original grinding characteristics could not be exhibited. In addition, there was resistance when peeling off the first grinding stone layer, and it was difficult to remove, so this example was also inferior to Examples 1 to 9.

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

1 First grinding stone layer 2 Second grinding stone layer 11 Abrasive grains of first grinding stone layer 12 Binder of first grinding stone layer 21 Abrasive grains of second grinding stone layer 22 Binder of second grinding stone layer 3 Shaft integrated with dental abrasive 4 Shaft detachable portion 5 Detachable shaft 6 Rotating shaft 7 Fitting portion 7a Dimples 7b, 7c Lattice pattern 7d, 7e, 7f Slit 8 Separation layer 10 Dental abrasive 10a Dental abrasive (with dimple shape)
10b Dental abrasive (with shaft)
10c Dental abrasive (separate shaft type)
10d Dental abrasive (with separating agent layer)
10e Dental abrasives (bullet shaped)
10f Dental abrasive (spindle shape)
10g Dental abrasive (cup shape)

Claims (7)

A dental abrasive material that is composed of multiple stacked grinding stone layers, each of which contains abrasive grains (A) and a bonding material (B), and each of which is separable from the other. The dental abrasive material according to claim 1, wherein the bonding material (B) in at least one of the plurality of grinding stone layers includes an elastomeric material. The dental abrasive has a rotating shaft,
The dental abrasive according to claim 1 , wherein the plurality of grinding stone layers are stacked from the center of the rotation shaft in a peripheral direction. The dental abrasive material according to claim 3, wherein the average particle size of the abrasive grains (A) in the grinding layer on the outer periphery of each grinding stone layer is larger than the average particle size of the abrasive grains (A) in the grinding layer on the inner periphery of each grinding stone layer. The dental abrasive material according to claim 1, wherein two adjacent grinding stone layers among the plurality of grinding stone layers are held by physical interlocking. The dental abrasive material according to claim 1, wherein two adjacent grinding stone layers among the plurality of grinding stone layers are held together via an adhesive layer. The dental abrasive material according to claim 1, wherein two adjacent grinding stone layers among the plurality of grinding stone layers are held together via a separating agent layer.

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