JP2753501B2 - Dental investment composition - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a powdered dental investment material composition for use in the production of a cast restoration to be installed in the oral cavity in dentistry. .

[Conventional technology]

Dental metal restorations are made of wax material by the lost casting method using precision casting technology, a sprue wire (injection port) is attached to the restoration, and the restoration is buried in the dental investment material. It has been made by a procedure in which a molten metal is poured through a runner made by a sprue wire into a mold made by extracting a wire and burning off the wax. In particular, dental metal restorations are used in the oral cavity for the purpose of restoring missing teeth, so high dimensional accuracy is required.To obtain dental metal restorations with high dimensional accuracy, dental implantation It is necessary to compensate for the shrinkage of the metal upon cooling by utilizing the expansion of the material upon setting and upon heating.

These dental investment materials are made of a refractory material such as quartz and / or cristobalite, a gypsum-based investment material in which hemihydrate gypsum is mixed as a binder, and a heat-resistant material in which soluble phosphate and magnesium oxide are mixed as a binder. Phosphate-based investment materials having high properties are widely and generally used. The surgeon usually weighs the investment material powder using the powder measuring device attached to the container, accurately weighs the specified amount of water or the specified amount of liquid, takes it into a small rubber ball, and removes the gypsum spatula. After the mixture is kneaded to make investment material mud, the wax pattern is poured into a planted casting ring and buried.

Usually, when a dental technician performs such a burial operation, a large number of casting rings are prepared in order to improve the work efficiency, a large amount of investment material is kneaded at a time, and the wax pattern is buried. However, the operable time of the investment material is limited (usually at room temperature, about 10 to 15 minutes). In order to perform the work efficiently, it is necessary that the investment material mud has good fluidity. On the other hand, if the fluidity is too good, the investment material mud may flow out of the gap between the rings, or the liquid may be separated, which is not suitable for actual use.

As described above, it is necessary to adjust the particle size of the investment material powder so that the investment material mud has appropriate fluidity.

However, in this method, the particle size is adjusted many times due to variations in the particle size of the raw material,
In some cases, it has drawbacks such as not being able to obtain desired fluidity. In addition, the investment material powder contains fine particles to obtain a smooth metal restoration on the surface, so once it is opened, it easily absorbs moisture and the like in the atmosphere, causing the setting time and the fluidity to increase and decrease. Has the disadvantage that it significantly affects the value of the setting and thermal expansion of the investment to compensate for the shrinkage of the metal.

[Means for solving the problem]

Accordingly, the present inventors have conducted intensive studies to establish a simple method for adjusting the flowability of investment mud, and as a result, have found that the flowability of investment mud is closely related to pH and completed the present invention. did.

That is, the present invention relates to a powdered dental investment material composition comprising hemihydrate gypsum as a binding material and quartz and / or cristobalite as a refractory material, at least two types having a buffering action selected from acids, bases and salts. The above is contained in an amount of 0.02 to 5.0% by weight, and the flowability of the investment material mud can be easily controlled by the pH, and the storage stability is excellent. However, the same effect was not observed for a phosphate investment material obtained by mixing a soluble phosphate and magnesium oxide as a binder.

Specifically, the relationship between the pH value and the fluidity was ascertained that the fluidity increased when the pH value was low, and decreased when the pH value was high, and the present invention was completed.

When the metal of the dental restoration is a gold alloy, a palladium alloy, a silver alloy, etc., a gypsum-based investment material using hemihydrate gypsum as a binding material and quartz and / or cristobalite as a refractory material is used. Is done. An acid having a buffering action,
The combination of at least two or more selected from bases and salts may be any combination of acids, bases, and salts of any kind generally used when preparing a buffer solution as long as the pH is in the range of 1 to 8. Typical examples are citric acid and potassium citrate, lactic acid and sodium lactate, acetic acid and sodium acetate, tartaric acid and sodium tartrate, potassium hydrogen citrate and borax, potassium hydrogen citrate and citric acid, and potassium dihydrogen phosphate. Sodium hydroxide, disodium hydrogen phosphate and citric acid, disodium hydrogen phosphate and potassium dihydrogen phosphate, and the like can be used.

Acids having a buffering action, bases, at least two or more combinations selected from salts are used in dental investment materials at 0.02 to 5.
By adding 0% by weight, the fluidity of the investment material mud could be controlled very easily and the storage stability was improved. If the pH adjuster is less than 0.02%, it will not be possible to control the fluidity of the investment material mud. If it exceeds 5.0% by weight, the setting and expansion of the investment material composition will decrease, and the compressive strength will also decrease, resulting in a decrease in dental strength. The characteristics as an investment material for use are significantly reduced.

Since the dental investment material composition according to the present invention adjusts and stabilizes the fluidity by the pH buffering action, it is not necessary to strictly adjust the particle size of the raw material powder as in the prior art, and the storage stability is improved.

It should be noted that the powdery dental investment material according to the present invention may be added with a gypsum setting time modifier as usually used. As the gypsum setting time regulator, any of those conventionally known can be used. For example, organic acids and salts thereof such as citric acid, succinic acid, oxalic acid and malic acid; sodium salts such as hydrochloric acid, boric acid and sulfuric acid; inorganic salts such as potassium salts, magnesium salts, calcium salts and aluminum salts; aspartic acid and glutamic acid , Cysteine and other amino acids and salts thereof, sugars such as sucrose, starch and pectin, or coloring agents such as pigments.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples.
It should be noted that such examples are merely examples, and there is no particular limitation on at least two or more combinations selected from acids, bases, and salts having a buffering action employed in carrying out the present invention.

Examples 1 to 6 and Comparative Examples 1 and 2 In each of the examples and comparative examples, the kneading method at the time of preparing the sample was such that water having a standard mixing ratio of 23 ± 2 ° C. was put into a small rubber ball for dental use. , And after putting 100g of investment material for 15 seconds,
Using a gypsum mixing spatula, kneading was performed at a mixing speed of about 100 times per minute for 30 seconds.

Setting time, fluidity and compressive strength are based on Japanese Industrial Standard T660
1 (Gypsum-based investment material for dental casting)
C).

The pH was measured by placing 100 ml of distilled water in a 200 ml beaker, gently throwing a 10 g sample into the beaker, stirring the mixture lightly with a glass rod for about 30 seconds, and measuring the pH value with a glass electrode type pH meter.

The storage stability is measured by the forced deterioration method in which the investment material powder in a polyethylene bag is stored in a thermo-hygrostat at a temperature of 37 ° C and a relative humidity of 100% for 60 days. After the forced deterioration, the setting time and fluidity of the investment material are measured. And the setting time fluctuation (min) after subtracting the initial setting time and fluidity previously measured by the same method.
And fluctuation of fluidity (mm).

[Effect of the Invention] As is clear from the table, a combination of at least two or more selected from acids, bases and salts having a buffering action is 0.02 to 5.
With the dental investment material containing 0% by weight, the fluidity of the investment material mud could be easily controlled by the pH value. Each fluidity depends on the pH value, and when the pH value is low, the fluidity increases, and when the pH value is high, the fluidity decreases. In addition, in the change of the setting time and the fluidity after the forced deterioration, in any of the examples, the behavior was smaller than that of the comparative example, the storage stability was excellent, and the performance required for the dental investment material composition was improved. It turned out to be something.

Claims (3)

(57) [Claims] 1. A dental investment material composition comprising a hemihydrate gypsum as a main component of a binder and at least two types selected from acids, bases and salts. 2. A dental implant according to claim 1, wherein at least two or more selected from acids, bases and salts have a buffering action and a pH in the range of 1 to 8. Material composition. 3. The dental investment material composition according to claim 1, wherein a combination of at least two or more selected from acids, bases and salts is 0.02 to 5.0% by weight.