JPS60208902A - Dental embedding commposition for casting having high thermal expansion coefficient - Google Patents

Abstract

PURPOSE:To provide a dental embedding composition for casting, having unusually high thermal expansion coefficient at high temperature, and capable of remarkably improving the accuracy of casting, by using aluminum tertiary phosphate composed mainly of berlinite as the refractory material. CONSTITUTION:The objective dental embedding composition for casting and having extraordinarily high thermal expansion coefficient between 800 deg.C and 900 deg.C can be prepared by using aluminum tertiary phosphate composed mainly of berlinite as the refractory material. The aluminum tertiary phosphate composed mainly of berlinite has low specific surface area measured by BET process, i.e. <=5m<2>/g, preferably <=3m<2>/g. To improve the workability of the casting, it is preferable to mx the composition with a silica aggregate, or to heat the berlinite to convert a part thereof to cristobalite, or to add 0.05-3.0wt% one or more group I or group II metal to the aluminum tertiary phosphate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dental casting investment material composition having a large coefficient of thermal expansion.

Dental metal molded products such as crowns and inlays are usually cast using a casting technique called the lost wax method, according to the following process.

l) With impression materials such as silicone rubber and alginate,
An impression of the patient's mouth is taken and plaster is poured into the impression to create a plaster model.

2) Using wax material on this plaster model, create a prototype of the desired crown or inlay.

3) The obtained wax model is embedded in an investment material made of silica powder or the like, and after the investment material has hardened, it is heated to melt the wax model.

4) Inject the molten water containing the dental casting alloy into the cavity formed in the investment material according to 3) above, and cool and solidify it to create a cast molded product.

In the above casting process, when the molten alloy cools and solidifies, depending on the type of alloy used, the molding cavity when injecting the molten alloy must be expanded in advance to compensate for the shrinkage. . This expansion is performed by using both expansion during curing of the investment material (curing expansion) and expansion during heating (thermal expansion). However, in particular, curing expansion is unstable, so the actual situation is that investment materials that can stably obtain a sufficient expansion coefficient for casting metals with a large expansion coefficient have not been obtained. In particular, cobalt-chromium metal is known to be cheaper than precious metal alloys such as gold alloys and silver alloys as a dental restorative material, and has excellent mechanical properties and corrosion resistance, and the demand for its use has increased in recent years. The melting point of chromium alloy is high, over 1300°C, and the expansion rate to compensate for shrinkage is approximately 2.
As it is as large as 7%, it is currently extremely difficult to cast with sufficient precision using conventional investment materials. Casting metals with such a large coefficient of thermal expansion has resulted in poor productivity at dental laboratories, and has even led to prolongation of dental treatment.

Against the background described above, the emergence of high-temperature investment materials with a large coefficient of thermal expansion is desired.

In view of these circumstances, the present inventors have conducted intensive studies on investment materials with a large coefficient of thermal expansion, and have found that if tertiary aluminum phosphate, which is mainly composed of berlinite, is used as a refractory material, it is possible to It was discovered that the coefficient of thermal expansion becomes dramatically large in the range of 300 to 300 nm, and this led to the completion of the present invention.

That is, the present invention is a dental casting investment material composition characterized by containing tertiary aluminum phosphate mainly composed of berlinite as a refractory material.

The use of tertiary aluminum phosphorus (hereinafter referred to as aluminum phosphate) as a fireproof material for investment materials for dental decay is disclosed in Japanese Patent Application No. 58-45754, which was previously filed by the present inventors. . In this application, aluminum phosphate was used as a medium-low temperature investment material of 700° C. or less to exhibit excellent thermal expansion characteristics. Therefore, the present inventors further investigated aluminum phosphate as an investment material that can be used even at high temperatures exceeding 700°C, and found that berlinite-type aluminum phosphate exhibits large thermal expansion between 800°C and 900°C. No.1
However, it has been discovered that when this aluminum phosphate is used alone as a refractory material, an amazingly high coefficient of thermal expansion of about 5.3% can be obtained.

The reason why the composition of the present invention has a large coefficient of thermal expansion is considered to be as follows.

Aluminum phosphate and silica (S r 02 ) have similar crystal structures, but each undergoes a thermal transition at a unique temperature as follows.

0 Aluminum Phosphate (AAC P04) 0 Silica (SiO2) 57360 220-270 ℃ Therefore, even if quartz is included in the refractory material of the investment material, it will change from quartz to tridymite to cristobalite when heated as the investment material. Virtually no metastasis occurs.

Therefore, when SiO2 is used as an investment material aggregate,
Only the expansion due to the α-→β phase transition of quartz and cristobalite is utilized. In contrast, aluminum phosphate.

Since the tridymite type is very unstable, the transition from berlinite to cristobalite type progresses quickly with the heating used as an investment material. Therefore, in the case of aluminum phosphate, in addition to berlinite, thermal expansion due to the transition from berlinite to cristobalite type can be utilized, so it is thought that larger thermal expansion can be obtained than with silica-based aggregates.

As mentioned above, when berlinite-type aluminum phosphate is used as a refractory material for burial materials and lubricating materials, investment materials with various coefficients of thermal expansion are required, which is approximately 5.3%. 1. If the berlinite-type aluminum phosphate of the present invention is mixed with a conventionally used silica-based aggregate, or if berlinite is heat-treated and a part of it is transformed into a cristobalite-type, it can be used for casting. It is now possible to freely adjust the coefficient of thermal expansion to suit the dental alloy being used.
Casting accuracy is greatly improved.

In addition, in order to further improve the workability of casting, Li, N
a, at least one metal atom belonging to Group 1 or Group 2 of the periodic table, such as Be, Mg, Ca, Sr, etc., at 0.05
By using aluminum phosphate containing aluminum phosphate in the range of % by weight to 3% (hereinafter % indicating content 171 refers to % by weight unless otherwise specified), large thermal expansion that occurs at temperatures higher than 900°C can be avoided. The starting temperature is lowered to 750-800℃]. The content of these different metal atoms is 0.
It is preferable to add sardine in a range of 0.05% to 3%, preferably in a range of 0.1% to 1.5%.

If the amount added is less than the above 0.05%, no effect of lowering the transition temperature will appear. On the other hand, if it is added in an amount exceeding 3%, the fire resistance of the berlinite-type aluminum phosphate decreases, and the investment material shrinks in a high temperature range, which is contrary to the purpose of the present invention, which is not preferable.

Furthermore, the Het method specific surface area of the aluminum phosphate mainly composed of berlinite used in the present invention is 5 m' / g or less,
It is necessary to use one having a low specific surface area, preferably 3 m'/g or less. When using aluminum phosphate, which has a large specific surface area, the amount of liquid required when adding and kneading colloidal silica gel or water to the investment material powder increases, resulting in a large amount of liquid in the investment material after hardening. This is undesirable because the porosity increases and these pores absorb expansion.

Furthermore, when berlinite-type aluminum phosphate is used as a refractory material, although it exhibits rapid thermal expansion between 750°C and 1000°C, there is almost no cracking in the investment material, compared to conventional silica-based Compared to using only refractory materials, there is no need to pay close attention to controlling the heating rate, which is a major advantage of using berlinite aluminum phosphate. , will be explained in more detail, but of course the present invention is not limited thereto.

In the examples, all percentages indicating content indicate 1%, and specific surface areas indicate values measured by the BET method.

Example 1 Berlinite type aluminum phosphate (its X-ray diffraction pattern is shown in Figure 7) was used as a refractory material.
m'/g, (manufactured by Goi Toatsu Chemical Co., Ltd.) 80%, ammonium monophosphate as a binder (prepared by Taisei Dental Co., Ltd.) 10
%, and magnesium oxide (manufactured by Taisei Dental Co., Ltd.) 10%
were mixed in a mixer for 30 minutes to prepare an investment material.

Next, to 100 g of this investment material, 30 m of coloital silica dispersion (silica concentration 30%, trade name Chikara Taloid, manufactured by Catalysts Kagaku Kogyo Co., Ltd.) was added, and the mixture was mixed at 350 g using a vacuum mixer (manufactured by G-C Co., Ltd.). Mixed at rps. A test specimen was prepared from the investment material mixture thus prepared in accordance with JIS T 6601 (investment material for dental casting), and the coefficient of thermal expansion was measured. The results are shown in FIG.

Example 2 Herlinite type aluminum phosphate containing 0.85% of sodium as a refractory material (its X-ray diffraction pattern is shown in Figure 8: particle size of 74 pm or less, specific surface area of 1 m')
/ g, manufactured by Mitsui Toatsu Chemical Co., Ltd.) 80%, a test specimen was prepared in the same manner as in Example 1, and the coefficient of thermal expansion was measured. The results are shown in FIG.

Example 3 Aluminum phosphate (berlinite) (same as that used in Example 2) was fired at 900°C for 10 minutes in an electric furnace to prepare aluminum phosphate containing a mixture of berlinite and cristobalite types. A test specimen was prepared in the same manner as in Example 1 except that 80% of the refractory material was used, and the coefficient of thermal expansion was measured. The results are shown in FIG.

Example 4 30% sodium-containing aluminum phosphate (same as that used in Example 2) and silica aggregate (quartz,
Cristobalite mixture, particle size 74 μm or less, prepared by Taisei Dental Industry Co., Ltd.) 56%, monoammonium phosphate (same as that used in Example 1) 7%, magnesium oxide (same as that used in Example 1) as a binder. ) and 7% in a mixer for 30 minutes to prepare an investment material.Next, 29m of colloidal silica dispersion (same as that used in Example 1) was added to 100g of this investment material. A test specimen was prepared in the same manner as in Example 1, and the coefficient of thermal expansion was measured. The results are shown in FIG.

Comparative Example 1 As a representative of conventional commercially available investment materials using silica-based aggregate and phosphoric acid binding material, Cerabest (manufactured by Taisei Dental Kamiri Co., Ltd.) 1
A test specimen was prepared in the same manner as in Example 1, and the coefficient of thermal expansion was measured. The results are shown in FIG.

Comparative Example 2 Berlinite-type aluminum phosphate (the X-ray diffraction diagram of which is shown in Figure 9) was used as a refractory material.
n'/g) 80%, 10% monoammonium phosphate (same as that used in Example 1) as a binder, and 10% magnesium oxide were mixed in a mixer for 30 minutes to prepare investment material 1.
A test specimen was prepared in the same manner as in Example 1 by adding 40 m of colloidal silica dispersion (same as that used in Example 1) to 00 g, and the coefficient of thermal expansion was measured. The results are shown in FIG.

Test Example Using the investment material prepared in Example 3, ANS IMD 15
Immediately after creating the MOD inlay-wax pattern according to 6-2-4-3-8, it was buried, and a Ni-Cr alloy for dental casting (manufactured by Thai Crown Ni-Taisei Dental Industry Co., Ltd.) was used for dental casting at a mold temperature of 1 and 900°C. Molded in accordance with the law. After cooling, the MOD inlay casting was taken out and adapted to the original model.

As a result, the surface of the cast body was smooth and showed good compatibility.

As is clear from the results of the above-mentioned Examples and Comparative Examples, the investment material of Comparative Example 1 has an expansion coefficient of about 1 at 1000°C.
．． It is 3%. On the other hand, in Example 1, about 850°C
Expanding more rapidly, ioo.

It exhibits a large coefficient of thermal expansion of about 5.3% at 0C.

In Example 2, by adding Na to berlinite-type aluminum phosphate, the starting temperature of transition expansion was lowered to about 7
Expansion begins rapidly at 80°C, reaching approximately 4°C at too'c.
．． It shows a thermal expansion of 9%.

The results of Example 3 show that by heat-treating berlinite-type aluminum phosphate to form a mixture of berlinite and cristobalite types, and using this as a refractory material, it is possible to adjust the coefficient of thermal expansion to be smaller than that of the berlinite type alone. One thing is clear.

The results of Example 4 show that by using aluminum phosphate and silica in combination as a refractory material, the expansion coefficient required for casting dental casting alloys with large thermal and expansion coefficients can be obtained. Furthermore, in Comparative Example 2, berlinite-type aluminum phosphate is used as the refractory material, but because the specific surface area is as large as 8 m'/g, the mixing ratio of colloidal silica has to be increased. It can be seen that a lower coefficient of thermal expansion can be obtained than when aluminum phosphate with a low specific surface area is used.

As described above, all investment materials in which berlinite-type aluminum phosphate is added as a refractory material have a higher coefficient of thermal expansion than investment materials in which only silica is used as a refractory material. This effect is particularly noticeable when aluminum phosphate, which has a small specific surface area, is used. Furthermore, by adding a small amount of an alkali metal such as Na or an alkaline earth metal to the berlinite-type aluminum phosphate, the expansion start temperature can be lowered, and an investment material that is easier to use can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the coefficient of thermal expansion of each investment material obtained in Example 1, FIG. 2 in Example 2, FIG. 3 in Example 3, and FIG. 4 in Example 4. FIG. 5 is a graph showing the coefficient of thermal expansion of each investment material obtained in Comparative Example 1 and FIG. 6 in Comparative Example 2. Furthermore, FIG. 7 is an X-ray diffraction diagram of aluminum phosphate used in Example 1, and FIG. 8 is an X-ray diffraction diagram of aluminum phosphate used in Comparative Example 2. It is. Patent Applicant: Mitsui Toatsu Chemical Co., Ltd. No. 10 Snake 120 i degrees 1℃) No. 31 Official No. 1 No. 41″?1 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1) An investment material composition for dental casting, characterized in that it contains tertiary aluminum phosphate mainly composed of berlinite as a refractory material. 2) The Bett method specific surface area of tertiary phosphorous aluminum is 5
The dental casting investment material composition according to claim 1, characterized in that the ratio is not more than m'/g. 3) At least one metal selected from metals belonging to Groups 1 and 2 of the periodic table is added to tribasic aluminum phosphate.
．． The dental casting investment material composition according to claim 1 or 2, characterized in that the composition contains 0.05 to 3.0% coul.