Dental gypsum composition

Abstract

Provided is a dental gypsum composition that has such a hardness that, when a model or the like is placed in a desired position using a slurry prepared by adding water to the gypsum composition, as required in the case of, for example, mounting the model to an articulator, the model can be continuously and stably placed in the desired position without sinking. At the same time, the dental gypsum composition can impart to the aforesaid slurry adequate fluidity (usable time) to achieve good workability.　The dental gypsum composition is characterized by containing gypsum hemihydrate and pregelatinized starch.

Description

Dental plaster composition

[0001] The present invention relates to a dental gypsum composition used, for example, when placing and fixing a dental model on an articulator.

[0002] Gypsum powder is highly safe and functional, and is widely used, for example, as a dental material for obtaining various models required for making dentures (false teeth). One use of dental gypsum compositions is for mounting and fixing dental models in an articulator. An articulator is a device that reproduces jaw movement and occlusion by attaching plaster models made from impressions of upper and lower teeth. For example, when preparing prosthetic devices such as dentures (false teeth) to treat missing teeth, it is used to check whether the occlusion of the prosthetic device is in a good state. Specifically, an articulator is used to actually occlude the dentures (false teeth) being made, check their condition, and then fine-tune the prosthetic device to improve the occlusion.

[0003] Conventionally, various dental gypsum materials have been proposed with various modifications depending on the intended use. For example, Patent Document 1 proposes a dental gypsum powder capable of preparing a gypsum slurry with high consistency and excellent buildability, stating that a gypsum slurry with high consistency and excellent buildability is desired in order to reproduce the details of the oral cavity and to create a three-dimensional model. Specifically, a dental gypsum powder containing 0.5 to 3 parts by mass of gypsum dihydrate, 0.05 to 3 parts by mass of potassium sulfate, and 0.1 to 1 part by mass of a water-soluble saccharide per 100 parts by mass of gypsum hemihydrate has been proposed. According to this proposal, mixing a predetermined amount of dental gypsum powder and water can prepare a gypsum slurry with high consistency and excellent buildability. Furthermore, the gypsum slurry exhibits low fluidity when left stationary, but exhibits high fluidity when subjected to vibration or load, demonstrating thixotropy.

[0004] JP 2017-55850 A

[0005] In contrast to the conventional techniques proposed to suit specific applications as described above, the present inventors recognized that it is important to develop a dental gypsum composition having unprecedented properties suitable for applications such as those described below, and that this would be an effective means of contributing to the advancement of dental technology. As described above, when producing prosthetic appliances such as dentures, an articulator is used to reproduce the jaw movement, bite position, and other parameters, and fine adjustments are made to the prosthetic appliance depending on the condition. One of the tasks required by dental technicians, etc., in this case is to attach a dental model taken from the patient to the articulator and reproduce the bite in the mouth.

[0006] A gypsum composition is also used when mounting a model on the articulator described above. The dental gypsum composition used to mount a model on the articulator is required to have the following two properties. First, in order to mount the model in the correct position, the gypsum composition must be hard enough to prevent the model from sinking when the model is placed in a predetermined position on the articulator using a slurry prepared by adding water to the gypsum composition. Second, in order to ensure that the worker has sufficient working time to set the model in the correct position, the gypsum composition must be hard enough to obtain a slurry with the desired hardness and suitable fluidity (working life) when water is added to the gypsum composition.

[0007] To meet the above-mentioned demands, commercially available plaster products used to attach a cast to an articulator ensure hardness by shortening the hardening time. A shorter hardening time means a shorter usable time (pot life). Therefore, the above-mentioned conventional products have a short usable time, for example, about 3 minutes. However, according to the inventors' research, a usable time of about 3 minutes poses a problem: it is difficult to reliably and stably position and fix the cast in a desired position on the articulator in a favorable condition without relying heavily on the experience of the operator. On the other hand, if the cast cannot be attached to the articulator in a favorable condition, it is necessary to break up the hardened plaster, remove the cast, and then reattach the cast to the articulator, which significantly reduces work efficiency.

[0008] Therefore, an object of the present invention is to provide a dental gypsum composition that solves the above-mentioned problems, and that, when water is added to the gypsum composition to form a slurry, which is required for a dental gypsum composition when a model is attached to an articulator, and the slurry has a hardness that allows the model to be stably placed in the desired position without sinking, and at the same time, the slurry has a desired hardness and appropriate fluidity (use life) that allows good workability.

[0009] The above-mentioned object can be achieved by the present invention, which proposes the following dental gypsum composition: [1] A dental gypsum composition comprising gypsum hemihydrate and pregelatinized starch.

[0010] The above-mentioned dental gypsum composition preferably further has the following configuration. [2] The dental gypsum composition according to the above-mentioned [1], wherein the pregelatinized starch is contained in an amount ranging from 0.01 to 0.3 parts by mass relative to 100 parts by mass of the gypsum hemihydrate. [3] The dental gypsum composition according to the above-mentioned [1] or [2], wherein the pregelatinized starch is made from at least one raw material selected from the group consisting of potato, corn, wheat, and tapioca. [4] The dental gypsum composition according to any one of the above-mentioned [1] to [3], wherein the gypsum hemihydrate contains alpha-type gypsum hemihydrate and / or beta-type gypsum hemihydrate. [5] The dental gypsum composition according to any one of the above-mentioned [1] to [4], which is used when placing and fixing a dental model on an articulator. [6] The specific surface area of ​​the gypsum hemihydrate is 1,000 to 9,000 cm ２ The dental gypsum composition according to any one of [1] to [5] above, wherein the gypsum content is 1 / g.

[0011] According to the present invention, it is possible to provide a dental gypsum composition that has the hardness required for a dental gypsum composition when, for example, attaching a model to an articulator, the gypsum composition is added with water to form a slurry, and when the slurry is used to place a model or the like in a desired position, the model or the like does not sink and can be maintained in a stable position, and at the same time, the slurry has the desired hardness and appropriate fluidity (use life) to achieve good workability.As a result, by using a slurry obtained by adding water to the dental gypsum composition of the present invention, it is possible to provide a useful dental gypsum composition that allows, for example, when an operator attaches a model to a desired position on an articulator, to place the model in a stable and good state with good workability, thereby improving work efficiency.

[0012] 1 is a schematic diagram showing a state in which a slurry 1 made by adding water to the dental gypsum composition of the present invention is piled on a base 2 of an articulator 10. FIG. 2 is a schematic diagram showing a state in which a model is placed on the articulator 10 in the state of FIG. 1 , and a slurry 1 made by adding water to the dental gypsum composition of the present invention is hardened to set a model 3.

[0013] The present invention will be described below with reference to preferred embodiments. As shown in Fig. 2, the present inventors have intensively studied a dental gypsum composition that has a hardness that allows the model, etc. to be stably maintained in a desired position without sinking when the gypsum composition is added with water to prepare a slurry 1, which is required when attaching a model 3 to an articulator 10, and the slurry 1 is used to place the model 3 at a desired position, and at the same time, allows the slurry to have a desired hardness and appropriate fluidity (use life) that allows good workability, and as a result, the present invention has been achieved.

[0014] In the course of intensive research into a gypsum composition that is required to satisfy the above-mentioned contradictory properties that are the object of the present invention, the present inventors discovered that by using pregelatinized starch, which has not conventionally been used in dental gypsum compositions, remarkable effects that could never be obtained by using a general consistency adjuster (thickening agent), as will be described later, can be obtained, thereby achieving the present invention.

[0015] Examples of the pregelatinized starch that characterizes the present invention include those made from at least one selected from the group consisting of potato, corn, wheat, and tapioca. Here, pregelatinized starch refers to starch obtained by rapidly dehydrating and pulverizing a liquid containing gelatinized starch without allowing it to age. Pregelatinized starch is also known as α-starch, pregelatinized starch, pregel, and instant starch. When starch is heated with water, the starch molecules lose their regularity and become pasty (α-form). This process is called gelatinization (gelatinization). Pregelatinized starch is characterized by its ability to dissolve in water and reproduce a viscous paste. Because it rapidly develops viscosity, it is used for thickening and water retention. For example, it is widely used as an additive in foods such as bread, confectionery, and noodles. According to the studies of the present inventors, pregelatinized starches made from potato, corn, wheat, and tapioca are preferred for use in the present invention. Among these, pregelatinized starches made from potato are particularly preferred because excellent effects can be obtained with a small amount added.

[0016] According to the studies of the present inventors, the amount of pregelatinized starch added is preferably within a range of 0.01 to 0.3 parts by mass relative to 100 parts by mass of gypsum hemihydrate. As will be described later, for example, in the case of pregelatinized starch made from potato, the desired properties aimed at in the present invention can be more effectively and stably obtained in a range of 0.01 to 0.1 parts by mass, or even in a range of 0.03 to 0.1 parts by mass, relative to 100 parts by mass of gypsum hemihydrate. Furthermore, for example, in the case of pregelatinized starch made from corn, the desired properties aimed at in the present invention can be more effectively and stably obtained in an amount of 0.05 to 0.3 parts by mass relative to 100 parts by mass of gypsum hemihydrate. Considering the cost of the material, it is desirable to add as little pregelatinized starch as possible. Therefore, from an economical standpoint, it is preferable to use pregelatinized starch made from potato.

[0017] The dental gypsum composition of the present invention is characterized by the use of gypsum hemihydrate in combination with the above-mentioned pregelatinized starch. As the gypsum hemihydrate, either alpha-type gypsum hemihydrate or beta-type gypsum hemihydrate can be used, and both may be appropriately blended and used. Note that alpha-type gypsum hemihydrate has advantages such as requiring less water for hardening than beta-type gypsum hemihydrate and exhibiting higher strength when hardened. Furthermore, in the dental gypsum composition of the present invention, the specific surface area of ​​the gypsum hemihydrate (both alpha-type and beta-type) used is 1000 to 9000 cm ２ The specific surface area is the value of the specific surface area measured by a Blaine air permeation device specified in JIS R 5201.

[0018] Since the dental gypsum composition of the present invention is used as a slurry by adding mixing water, a setting time adjuster may be added in addition to gypsum hemihydrate as needed. Common set accelerators, such as gypsum dihydrate and potassium sulfate, can be added to accelerate the setting of gypsum. Also, common set retarders, such as sodium citrate and potassium tartrate, can be added to delay the setting of gypsum. By using these additives, it becomes possible to easily adjust the "use time" of the dental gypsum composition of the present invention, when used as a slurry by adding mixing water, to a desired value that provides excellent workability.

[0019] The present invention will be specifically described below based on examples, comparative examples, and study examples. The present invention is not limited to these examples. In the examples, comparative examples, and study examples, "parts" and "%" are by mass unless otherwise specified.

[0020] [Study Example 1] <Study on Consistency Adjuster (Adhesive)> The present inventors first added water to a gypsum composition to form a slurry, and when the resulting slurry is used to place a model in a desired position, the hardness of the slurry is such that the model does not sink and can be stably maintained in the desired position, and at the same time, the slurry has an appropriate fluidity (use life) that allows good workability. The inventors conducted studies on the composition of the gypsum composition in order to find a dental gypsum composition that has such a hardness that the model does not sink and can be stably maintained in the desired position when used. In particular, the study focused on easily achieving a hardness that allows the model to be stably maintained in the desired position when made into a slurry.

[0021] At that time, a known setting time adjuster was appropriately blended to adjust the basic performance so that the usable time of the slurry would be about 5 to 10 minutes. The "usable time" was determined as follows. A gypsum composition was mixed with mixing water to prepare a slurry, which was then left to stand for 15 seconds in a rubber bowl and mixed for 15 seconds, and this process was repeated. The usable time was determined as the time when the fluidity decreased, i.e., the viscosity of the slurry increased, making it impossible to use in dental applications. Specifically, in this study, the usable time was defined as the time from when a worker added water to the gypsum composition to prepare a slurry to when the worker could no longer apply the slurry 1 to the base 2 of the articulator 10 shown in FIG. 1 .

[0022] The gypsum composition used in the study was mixed with mixing water (the point at which water was added was considered "wetted") to produce a mixed slurry, which was operated under the following fixed conditions to prevent differences due to the amount of water that would affect the consistency or the mixing conditions. Specifically, a specified amount of water for mixing was measured into a dental rubber bowl, and the gypsum composition powder was added thereto over 30 seconds, followed by mixing (stirring) for 60 seconds (up to 1 minute and 30 seconds after the start of adding the gypsum composition powder). A dedicated spatula with a blade tip of 13 to 20 mm and a blade length of 95 to 105 mm was used for mixing, and the stirring speed was kept constant at 100 rpm.

[0023] For the study, as shown in Table 1, slurries were prepared under the same conditions as described above using each gypsum composition containing a different type of consistency adjuster (thickening agent), and the consistency and usable life of each slurry were measured and evaluated. The following were used as the components shown in Table 1: α-type hemihydrate gypsum (manufactured by Yoshino Gypsum Co., Ltd., specific surface area: 2000 cm ２ / g) - β-type hemihydrate gypsum (manufactured by Yoshino Gypsum Co., Ltd., specific surface area: 7000 cm) ２ / g) Hardening accelerator: gypsum dihydrate, potassium sulfate Hardening retarder: sodium citrate, sodium succinate Pregelatinized starch: (raw material: potato, corn) Starch: (raw material: potato) PVA Guar gum Dextrin

[0024] The consistency was measured as follows. First, each mixed slurry was weighed into a ring with an inner diameter of 40 mm and a height of 60 mm placed on the upper surface of glass plate A (the operation was to be completed within 2 minutes after contact with water). Then, the ring was lifted and the slurry was gently poured onto the upper surface of glass plate A (2 minutes 30 seconds). Then, 3 minutes after contact with water, a square glass plate B measuring 11 cm in length and width and weighing 150 g was placed on the slurry poured onto glass plate A, and the size of the circularly expanded gypsum hardened body was measured and used as the consistency. Specifically, the arithmetic mean value of the maximum and minimum diameters of the hardened body in contact with the upper surface of glass plate A was used as the consistency. The consistency obtained as described above is shown in Table 1. A product with a consistency of less than 70 mm was considered to be acceptable and indicated by a circle. Furthermore, when the consistency was 70 mm or more, it was regarded as unacceptable and was indicated by x.

[0025] The "pot life" in Table 1 is a value measured by the following method. That is, mixing water was added to the gypsum composition for investigation, and a slurry was mixed under the above conditions. The slurry was left standing for 15 seconds in a rubber bowl, and then mixed for 15 seconds repeatedly. The time until the fluidity decreased (the viscosity of the slurry increased) and the slurry could no longer be piled on the base of an articulator was measured and defined as the pot life.

[0026]

[0027] As shown in Table 1, it was confirmed that the use of pregelatinized starch made it possible to obtain a dental gypsum composition with an appropriate consistency and a sufficient working life for stable work. In contrast, when other consistency adjusters were used, the consistency became too high and the desired appropriate viscosity was not obtained.

[0028] [Study Example 2] As the results of the study example shown in Table 1 indicate, the usefulness of using pregelatinized starch in blending a gypsum composition was found, and further studies were conducted. Specifically, two types of pregelatinized starch made from different raw materials were used, and the blending amounts of each were changed. The consistency and pot life were measured and evaluated in the same manner as described above. The components used in the blending were the same as those described in the study example above. The results obtained are shown in Tables 2-1 and 2-2. In Table 2-1, pregelatinized starch made from potato was used as the raw material, and in Table 2-2, pregelatinized starch made from corn was used as the raw material. Tests were conducted by changing the blending amount of pregelatinized starch in stages from 0.01 to 0.30 parts by mass per 100 parts by mass of gypsum hemihydrate. In addition, to adjust the consistency, the amount of mixing water was increased as the blending amount of pregelatinized starch increased, as shown in Table 2.

[0029]

[0030]

[0031] As shown in Table 2, it was confirmed that by using pregelatinized starch, regardless of the difference in raw materials or blending amounts, when mixing water was added to form a slurry and the slurry was used to attach a model to an articulator, a dental gypsum composition with appropriate consistency and a necessary and sufficient pot life for stable work could be obtained. Furthermore, it was found that by using pregelatinized starch made from potato as a raw material, it was possible to provide a dental gypsum composition that exhibits better properties when formed into a slurry, even with a small amount added.

[0032] 1: Plaster slurry 2: Base 3: Model 10: Articulator

Claims

1. A dental gypsum composition comprising gypsum hemihydrate and pregelatinized starch.

2. The dental gypsum composition according to claim 1, wherein the pregelatinized starch is contained in an amount within a range of 0.01 parts by mass to 0.3 parts by mass per 100 parts by mass of the hemihydrate gypsum.

3. 3. The dental gypsum composition according to claim 1, wherein the pregelatinized starch is made from at least one raw material selected from the group consisting of potato, corn, wheat, and tapioca.

4. The dental gypsum composition according to claim 1 or 2, wherein the hemihydrate gypsum contains α-type hemihydrate gypsum and / or β-type hemihydrate gypsum.

5. The dental gypsum composition according to claim 1 or 2, which is used when placing and fixing a dental model on an articulator.

6. The specific surface area of ​​the hemihydrate gypsum is 1000 to 9000 cm ２ The dental gypsum composition according to claim 1 or 2, wherein the gypsum composition is 0.01 to 0.1 g.