JP2013159602A - Dental gypsum powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dental gypsum powder with which generation of air bubbles in a kneaded material is suppressed only by kneading with water without using any special device or any instrument, and without using any emulsifier or any kneading liquid.SOLUTION: A dental gypsum powder includes a cyclic siloxane having three to ten SiO(CH)units of 0.00001 to 0.0005 wt.%. For instance, the cyclic siloxane is preferably hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, or decamethylcyclopentasiloxane.

Description

  The present invention provides a dental mold or a precision shaping mold that is free from defects and prevents a mixture of air bubbles in a paste that is a mixture when dental gypsum powder and water are kneaded. It relates to gypsum powder.

  In the dental field, dental plaster is used as a mold material when various dental prostheses such as inlays, crowns, bridges, partial dentures, and full dentures to be installed in the oral cavity are produced.

  Dental gypsum is usually provided in the form of a powder mainly composed of α hemihydrate gypsum (hard gypsum) and / or β hemihydrate gypsum (calcined gypsum), which are hemihydrate gypsum. Dentists and technicians collect a predetermined amount of dental gypsum composition powder and water for kneading in a small rubber bowl (rubber bowl) and knead it using a special spatula. After making the gypsum slurry, when using it for a model, it is poured into a negative mold obtained by taking an impression in the oral cavity and cured to produce a working model or a jaw model that reproduces the oral state. When used for denture burial, it is used for the purpose of burying a wax denture by pouring it into a dental flask. The working model and jaw model are the basis for making a dental prosthesis, and the dental prosthesis to be produced requires high dimensional accuracy. There is a strong demand for a low surface roughness and a smooth surface property of the cured product.

  What is important for a precise model is that bubbles are not included in the paste, which is an admixture, when kneading dental gypsum powder and water. In general, dental gypsum has a problem that air bubbles easily enter due to a low water mixing ratio and a high paste viscosity.

  Kneading using a vacuum kneader is performed to produce a model with fewer bubbles. However, there are many dental clinics that do not have a relatively expensive vacuum kneader, and a method is widely used in which a paste that has been kneaded without using a vacuum kneader is applied to a vibrator and poured into an impression while crushing bubbles. However, since the bubbles inside the paste cannot be eliminated even if a vibrator is used, the bubbles inside often appear on the model surface during curing, and this is not a fundamental solution.

  Therefore, dental gypsum has been developed with less generation of bubbles during kneading. For example, a method for kneading dental plaster is disclosed in which an emulsion prepared by dispersing a nonionic surfactant in water as an emulsifier is added to silicone oil when water is kneaded with dental plaster. (For example, refer to Patent Document 1 and Patent Document 2.) However, in this method, it is necessary to prepare a dedicated emulsifier in addition to gypsum powder and water, and the operation is complicated. In addition, even if the emulsifier was mixed with water, there was a drawback that a dedicated kneading liquid had to be prepared.

  Also, a defoaming method for a dental material kneaded product that reduces bubbles generated when kneading dental material, using a defoamer in which a handle is attached to a defoaming member having a curved surface There is a method for defoaming a dental material kneaded product that stirs the kneaded product (see, for example, Patent Document 3). However, this method requires the use of a dedicated instrument.

JP-A-5-155731 JP-A-6-133990 JP-A-6-178926

  The present invention provides a dental gypsum powder that can suppress the generation of bubbles in a kneaded product by merely kneading with water without using a special device or instrument and without using an emulsifier or a kneading liquid. This is the issue.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved if a specific siloxane is blended in dental gypsum powder, and the present invention has been completed.

That is, the dental gypsum powder according to the present invention is a dental gypsum powder characterized by containing 0.00001 to 0.0005% by weight of a cyclic siloxane having 3 to 10 SiO (CH ₃ ) ₂ units. is there.

  The dental gypsum powder according to the present invention is a dental gypsum powder that can suppress the generation of bubbles in the kneaded product by simply kneading with water without using a special emulsifier or kneading liquid.

Hereinafter, embodiments of the present invention will be described in detail. The dental gypsum powder according to the present invention contains 0.00001 to 0.0005% by weight of a cyclic siloxane having 3 to 10 SiO (CH ₃ ) ₂ units. By blending this specific cyclic siloxane, generation of bubbles can be suppressed when the dental gypsum powder is kneaded with water. Moreover, since an effect is acquired with a small compounding quantity, it does not have a bad influence on various performances of a gypsum hardened | cured material. SiO _{(CH 3)} cyclic siloxanes having 3 to 10 ₂ units can not be obtained the desired effect is less than 0.00001 wt%, kneading property as dental gypsum is deteriorated when it exceeds 0.0005 wt% .

The cyclic siloxane having 3 to 10 SiO (CH ₃ ) ₂ units has 3 to 10 SiO (CH ₃ ) ₂ units (hereinafter sometimes referred to as D units). For example, when D is 3, hexamethylcyclohexane Trisiloxane, when D is 4, octamethylcyclotetrasiloxane, and when D is 5, decamethylcyclopentasiloxane. The preferred number of SiO (CH ₃ ) ₂ units is 3 to 5, and octamethylcyclotetrasiloxane having D of 4 is most preferred because of ease of blending and high effect. These cyclic siloxanes having different D numbers can be used in combination.

  In the dental gypsum powder according to the present invention, the effect can be obtained even if only the above-mentioned cyclic siloxane is blended, but it can also be used in combination with a conventional silicone oil. Examples of the silicone oil include various dimethyl silicone oils and methylphenyl silicone oils.

  In the dental gypsum powder according to the present invention, the above-mentioned cyclic siloxane is blended with conventional dental gypsum powder mainly composed of hemihydrate gypsum. Hemihydrate gypsum includes α hemihydrate gypsum, β hemihydrate gypsum, and a mixture of α hemihydrate gypsum and β hemihydrate gypsum.

  Dental gypsum powder has operability and physical properties that are set according to the purpose of use, such as model materials and denture-embedding materials. It has been added. As curing retarders, known curing retarders such as salts such as citrate, borate, carboxylate and acetate, and water-soluble polymers such as den powder, gum arabic, carboxymethylcellulose, and gelatin are used. In general, it is contained in an amount of 0.00001 to 0.2 parts by weight per 100 parts by weight of hemihydrate gypsum powder.

  When a delicate adjustment of the curing time is required, a curing accelerator may be further used. As a hardening accelerator, well-known hardening accelerators, such as inorganic salts, such as sodium chloride and potassium sulfate, and a dihydrate gypsum fine powder, can be used, Usually, when mix | blending, it is 0 with respect to 100 weight part of hemihydrate gypsum powder. 0.001 to 2 parts by weight are contained.

  The dental gypsum powder according to the present invention may contain a curing expansion inhibitor such as potassium tartrate. The curing expansion inhibitor is preferably contained in an amount of 0.01 to 1 part by weight with respect to 100 parts by weight of the hemihydrate gypsum powder. In addition, the dental gypsum powder according to the present invention may contain a known colorant or lightening material as necessary.

  The dental gypsum powder according to the present invention may contain a water reducing agent. As a water reducing agent, sodium dodecylbenzenesulfonate can be used as an alkylbenzenesulfonate. Further, as the alkyl sulfate, conventionally used substances such as sodium lauryl sulfate, potassium lauryl sulfate, sodium myristyl sulfate, sodium cetyl sulfate, sodium stearate and the like can be used.

  Since the dental gypsum powder according to the present invention is obtained by adding and mixing a specific cyclic siloxane on the powder side of the dental gypsum, it retains the same powder form as the conventional dental gypsum, and an appropriate amount of this powder is obtained. A gypsum model can be made by adding 18 to 28 parts by weight of water, for example, 100 parts by weight of powder, to form a paste, and molding and curing to an arbitrary shape. That is, it is not necessary to prepare a special emulsifier or a dedicated kneading liquid.

  Examples of dental gypsum powder according to the present invention will be described in detail below.

<Raw Powder A Mixed with Cyclic Siloxane-Containing Silicone Oil>
1 g of silicone oil (polydimethylsiloxane) containing 4% by weight of hexamethylcyclotrisiloxane and 1% by weight of octamethylcyclotetrasiloxane is mixed with 99 g of α-hemihydrate gypsum powder and stirred for 1 hour to give 1% by weight of silicone oil. A diluted powder of (cyclic siloxane 0.05% by weight) was prepared. This is designated as raw powder A. Raw powder A was mixed with the dental gypsum powder described in the examples in the proportions shown in Table 1.

<Raw Powder B Mixed with Cyclic Siloxane-Containing Silicone Oil>
1 g of silicone oil (polydimethylsiloxane) containing 10% by weight of octamethylcyclotetrasiloxane is mixed with 99 g of α-hemihydrate gypsum powder by the above method to dilute 1% by weight of silicone oil (0.1% by weight of cyclic siloxane). A powder was prepared. This is designated as raw powder B. Raw powder B was mixed with the dental gypsum powder described in the examples in the proportions shown in Table 1.

<Raw powder C mixed with silicone oil only (for comparative example)>
1 g of silicone oil (polydimethylsiloxane) was mixed with 99 g of dental gypsum powder shown in Table 1 by the method described above to prepare a diluted powder of 1% by weight of silicone oil (0% by weight of cyclic siloxane). This is designated as raw powder C. Raw powder C was mixed with the dental gypsum powder described in the comparative example in the ratio shown in Table 1.
The final formulation and test results of each example and comparative example are summarized in Table 1.

<Evaluation of antifoaming properties>
100 g of dental gypsum powder and 23 g of tap water prepared in each example and comparative example are put in a rubber bowl, mixed with a gypsum spatula, poured into a mold having a diameter of 25 mm and a height of 50 mm, and left for 30 minutes. did. After the dental gypsum hardened, the model was cut in half, and the degree of bubbles observed on the cut surface was visually evaluated. In the case of bubbles of the same level as the conventional hardened gypsum, X was marked. The results are summarized in Table 1.

<Evaluation of kneadability during mixing>
The kneadability at the time of mixing was sensorially evaluated. The results are summarized in Table 1.

<Characteristic test>
The physical properties (curing time and fluidity) of the dental gypsum powders of Examples and Comparative Examples were measured by the methods defined in JIS T6605 “Dental hard gypsum” and JIS T6604 “Dental gypsum”. The results are summarized in Table 1.

<Table 1> Blending unit Weight%

Claims (1)

Dental gypsum powder SiO _{(CH 3) 2} units is cyclic siloxane having 3 to 10, characterized in that it contains from 0.00001 to 0.0005% by weight.