JPS61193741A - Investment casting material for dental purpose - Google Patents

Abstract

PURPOSE:To obtain an investment casting material having an adequately stabilized coefft. of thermal expansion for dental purpose by compounding gypsum, salt and cristobalite as well as quartz at a specific weight ratio each, adding further alumina thereto at a specific weight ratio and kneading the mixture with water. CONSTITUTION:30-40%, by weight, gypsum which permits easy adjustment of the coefft. of thermal expansion and exhibits substantially a binder effect, 0.6-1.5%, by weight, salt which suppresses the shrinkage of the gypsum, 40-52%, by weight, cristobalite which has a large coefft. of thermal expansion and fills the inside of a casting mold together with the quartz and 4-20%, by weight quartz are compounded. <=8%, by weight, alumina which contributes to an improvement in fire resistance is further added thereto and the mixture is kneaded with water. The investment casting material produced by such compounding is usable as a good casting mold for dental purpose and contributes to a considerable increase in applicable kinds of casting alloys.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to dental materials, and more particularly to investment materials used to embed wax tooth molds in the manufacturing process of cast products such as crowns, bridges, and inlays. It is.

Conventional technology and its problems Conventionally, as this type of investment material, phosphate-based investment materials and gypsum-based investment materials consisting of about 25 parts of gypsum, about 38 parts of quartz, and about 37 parts of cristobalite have been common. there were. However, in the former method, the casting mold obtained by immersing the wax tooth mold in a mixture of investment material and water or colloidal silica and then eluting the wax (hereinafter referred to as the casting mold) has a high crush resistance. There is a problem with destroying the casting mold later, and the latter has an extremely narrow range in which the coefficient of thermal expansion of the casting mold can be adjusted, so casting alloys with a solidification shrinkage rate corresponding to the coefficient of thermal expansion within this range are required. The problem was that alloys with a large solidification shrinkage rate could not be used.

In view of the above-mentioned circumstances, the present invention can greatly expand the range in which the coefficient of thermal expansion of a casting mold can be adjusted, and therefore increase the variety of usable casting alloys.
Moreover, it is an object of the present invention to provide a dental investment material with a new composition that does not cause any problems in terms of destruction of the casting mold.

Means for Solving the Problems In order to achieve the above object, the dental investment material according to the present invention contains 30 to 42% gypsum and 0.6 to 1.5% salt by weight.
, cristobalite 40-52%, and quartz 4-20%
% of each powder.

Gypsum acts as a binder, but if it is less than 30%, the binder effect will not be fully exerted, and if it exceeds 42%, it will be difficult to adjust the coefficient of thermal expansion, so the proportion of gypsum is 3.
Limited to 0-42%.

Salt has the effect of suppressing the shrinkage of gypsum, but if it is less than 0.6%, this effect is not sufficiently exerted.

Since cristobalite and quartz have large coefficients of thermal expansion themselves, they act to increase the coefficient of thermal expansion of the casting mold, but this effect is not sufficiently exerted when cristobalite is less than 40% and quartz is less than 4%.

The upper limit of the blending ratio of salt, cristobalite, and quartz is not particularly limited, but in relation to the blending ratio of gypsum, the upper limit of salt is 1.5%, the upper limit of cristobalite is 52%,
Preferably, the upper limit of quartz is 20%.

In addition, alumina may be added to the investment material according to the present invention if necessary. Alumina has the effect of increasing heat resistance, and its blending ratio is usually 8% or less.

The investment material according to the invention is used as follows. That is, 24 to 31 parts by weight of water is added to 100 parts by weight of the investment material, the investment material is thoroughly kneaded, and the wax tooth mold is embedded in the resulting kneaded material. The wax is then eluted by heating, and then a molten casting alloy is injected into the hollow part of the resulting casting mold under heating to form crowns, bridges, etc.
Obtain the required castings such as inlays.

In this case, a material with a small solidification shrinkage rate (
For example, when using silver alloy, gold-silver-palladium alloy, silver-palladium alloy, gold alloy, etc., the proportion of water added is relatively large within the above range to reduce the coefficient of thermal expansion of the casting mold, and conversely, When using a material with a large solidification shrinkage rate as a casting alloy (for example, nickel-chromium alloy, nickel-chromium alloy for baking, semi-precious metal for baking, etc.), add water at a relatively small proportion within the above range. , increase the coefficient of thermal expansion of the casting mold.

Example An investment material was obtained by blending powders of 32% gypsum, 0.8% common salt, 50.2% cristobalite, 11% quartz, and 6% alumina by weight.

Add 3CH+ of water to 100g of this investment material and knead the investment material well to obtain a mixed material (A>.
A kneaded product (B) was obtained in the same manner as above by adding 4 (l).

A wax tooth mold was embedded using the mixed material (A), and the temperature was set at 700°C in the hollow part of the casting mold obtained after the wax was eluted.
The desired casting was obtained by injecting the melt of the casting silver alloy under heating. Cast products were also obtained in the same manner as described above using a gold-silver-palladium alloy, a silver-palladium alloy, and a gold alloy instead of a silver alloy as a casting alloy. In this way, a desired cast product was obtained using a material with a small solidification shrinkage rate.

Further, using the above mixture (B) and using a material with a high solidification shrinkage rate such as a nickel chromium alloy, a nickel chromium alloy for baking, or a semi-pressure metal for baking as a casting alloy, a cast product is made by the same operation as above. Obtained.

In addition, when using the conventional gypsum-based investment material explained at the beginning of this ms, it was possible to use the above-mentioned casting alloy with a small solidification shrinkage rate, but because the coefficient of thermal expansion of the casting mold was small, However, casting alloys with high solidification shrinkage rates such as those mentioned above could not be used. In addition, when using phosphate-based investment materials, in addition to all of the casting alloys mentioned above, cobalt chromium alloys, nickel chromium alloys for baking, and blessed metal for baking could also be used, but the crushing resistance of the casting mold is large. It was extremely difficult to destroy the casting mold after casting.

The above results are shown in the table below.

(Left below) In the table, O indicates that the alloy for casting can be used, ×
indicates unusable. In the case of phosphate-based investment materials, it was difficult to destroy the casting mold after casting.

Depending on the effects of the invention and above, the dental investment material according to the present invention contains 30 to 42% gypsum, 0.6 to 1.5% salt, 40 to 52% cristobalite, and 4 to 20% quartz in the following amounts: Since it is made by blending various powders, the coefficient of thermal expansion of the casting mold can be adjusted within a wide range by changing the proportion of water added to the investment material. Therefore, by using the investment material of the present invention, the types of usable casting alloys can be greatly increased.

that's all

Claims (2)

[Claims] (1) Weight ratio: gypsum 30-42%, salt 0.6-1.
5%, cristobalite 40-52%, and quartz 4-5%
A dental investment material containing 20% of each powder. (2) The investment material according to claim 1, which contains 8% or less alumina by weight.