JPH09141387A - Phosphate-based investment compound composition for dental purpose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a phosphate-based investment compd. compsn. for dental purpose with which the holding of stable performance is possible without the removal of fine particles out of the investment compd. by pneumatic transportation at the time of production of a phosphate-based investment compd. compsn. for dental purpose. SOLUTION: This phosphate-based investment compd. compsn. is prepd. by mixing 0.01 to 0.5 pts.wt. tetrafluoroetylene resin with 100 pts.wt. mixture composed of magnesium oxide and ammonium dihydrogenphosphate as binders and quartz and cristobalite as refractory materials and further, mixing 0.001 to 0.05 pts.wt. one or >=2 kinds anion based surfactants selected form the group consisting of alkyl benzene sulfonate and alkyl sulfonate therewith.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dental phosphate-based investment material composition used in dental precision casting, and more specifically, to an investment material due to the effect of capturing fine particles of tetrafluoroethylene resin. The present invention provides a dental phosphate-based investment material composition capable of maintaining stable performance, since fine particles in the investment material that are pneumatically transported during the production of are separated by a cyclone separator and transported to the packaging process. Is.

[0002]

2. Description of the Related Art Dental metal restorations are made of a wax material in the form of restorations by a precision casting technique using the lost wax method, and sprue wires (molten metal injection ports) are attached to the restorations.
It is produced by a procedure of burying this in a dental investment material, extracting the sprue wire after the dental investment material is hardened, and injecting molten metal into the cavity formed by burning and removing the wax. In particular, a dental metal restoration is required to have high dimensional accuracy because it is used by mounting it in the oral cavity for the purpose of repairing a missing tooth. It is necessary to compensate for casting shrinkage of the metal by utilizing the expansion of the investment material during hardening and heating.

For that purpose, in the dental investment material,
It is necessary to strictly control expansion during condensation (condensation expansion value) and expansion during heating (thermal expansion value) so that stable casting shrinkage compensation is always possible. The particle size distribution of investment material particles is an important factor that affects the setting expansion value and the thermal expansion value. If the particle size distribution is different, the setting expansion value and the thermal expansion value will fluctuate, and the ability to compensate for casting shrinkage will change accordingly, and finally the dimensional accuracy of the metal restoration will be affected. Therefore, controlling the particle size distribution of dental investment materials is an important control item in the production of dental investment materials.

As the dental investment material, a gypsum-based investment material in which a refractory material such as quartz and / or cristobalite is mixed with α-hemihydrate gypsum as a binding material, and a refractory material such as quartz and / or cristobalite as a binding material Two types are generally used: a phosphate-based investment material having high heat resistance, which is a mixture of magnesium oxide and ammonium dihydrogen phosphate. Dental gypsum-based investment materials lack sufficient heat resistance when casting porcelain baking alloys with a melting temperature of over 1100 ° C or cobalt-chromium alloys used for metal denture bases, etc. Wood is mainly used.

The outline of the manufacturing process of the dental phosphate-based investment material is shown below. Grinding process of refractory materials (quartz, cristobalite, etc.). A process of adding magnesium oxide and ammonium dihydrogen phosphate as a binder to the crushed refractory material, and further crushing and mixing. Adjustment process such as curing time, fluidity and particle size after crushing and mixing. Packaging process. Usually and the steps are carried out in a batch processing apparatus such as a ball mill. The adjustment process of (1) is performed before discharge from the mill. The powder discharged from the mill after adjustment is transferred to the packaging process. In order to transport the dental phosphate-based investment material in the packaging process, an air transportation device using air is generally used.

The air transport device is a device for transporting a powder mixed with an air flow, and its system includes a pressure-feed type and a suction type. In either method, it is necessary to finally separate the powder and the air stream, and a cyclone separator is generally used for this separation.In this cyclone separator, fine powder particles are separated from the air stream. Instead of riding on the air flow, it is trapped by the air bag filter installed at the air outlet of the cyclone separator and discarded, or finer particles pass through the air bag filter and are released into the atmosphere. Occurs. This causes a phenomenon that the particle size distribution of the dental phosphate-based investment material when discharged from the mill is different from the particle size distribution after pneumatic transportation. As a result, after air transportation, the fine particles in the dental phosphate-based investment material decreased compared to before transportation, which caused changes in various properties such as condensation expansion value and thermal expansion value. Sisters,
An inconvenient phenomenon has occurred in which the performance expected as a dental phosphate-based investment material cannot be exhibited.

Specifically, when fine particles are removed from the dental phosphate-based investment material, both the setting expansion value and the thermal expansion value decrease, and the ability of compensating the casting shrinkage of the metal restoration decreases.
As a result, the metal restoration is smaller than expected,
The suitability when worn in the oral cavity is deteriorated, and not only is the recovery of the masticatory function insufficient, but it also causes serious clinical problems such as secondary caries. Further, when the fine particles are removed, the compressive strength of the dental phosphate-based investment material after curing is reduced, and the investment material is susceptible to thermal stress during heating to easily cause mold cracking. Casting defects such as casting burrs occur, making it impossible to use clinically.

[0008] If the conditions of mixing and crushing of the mill can be found so that the expected performance can be exhibited after pneumatic transportation, it can be a measure for preventing the occurrence of the above defects, but in reality, the change in particle size distribution caused by pneumatic transportation. Since (how much fine particles are removed) is not always constant, it is practically impossible to find out the milling / mixing conditions of the mill that anticipate changes in the particle size distribution. In addition, it is difficult to adjust various properties of dental phosphate-based investment materials after pneumatic transportation, and the change in particle size distribution during pneumatic transportation is product stability, and ultimately the size of metal restorations. This is a big problem in terms of accuracy stability.

[0009]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art described above, and when powder is pneumatically taken out from a mill discharge of a dental phosphate-based investment material to a packaging step, a fine powder is taken out. The powder is not separated by the cyclone separator and is not trapped by the air bag filter installed at the air outlet of the cyclone separator, or passes through this air bag filter and is not released into the atmosphere. To develop a dental phosphate-based investment material composition capable of stably obtaining the expected performance with fine powder remaining in the investment material product and always obtaining a metal restoration with high dimensional accuracy. Is an issue.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors composed of magnesium oxide and ammonium dihydrogen phosphate as binders, and quartz and cristobalite as refractory materials. If a powdered dental phosphate-based investment material composition is mixed with a predetermined amount of tetrafluoroethylene resin as a fine powder capturing material, the fine particles of the investment material have the fine particles of the investment material in the final stage of pneumatic transportation. Since it is reliably separated from air by the cyclone separator installed in the plant, it is possible to obtain a dental phosphate-based investment material composition that always maintains stable performance. If one or more anionic surfactants selected from the group consisting of alkylbenzene sulfonates and alkyl sulfates are mixed with the material composition, the kneading operability is improved. Out was to investigate that.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION That is, a dental phosphate-based investment material composition according to the present invention comprises a) magnesium oxide and ammonium dihydrogen phosphate as binders, b) quartz and cristobalite as refractory materials, 100 parts by weight of a mixture composed of tetrafluoroethylene resin
1st invention in which 0.01 to 0.5 parts by weight are mixed, and a) 100 parts by weight of a mixture composed of magnesium oxide and ammonium dihydrogen phosphate as a binder, b) quartz and cristobalite as a refractory material , Tetrafluoroethylene resin
0.01 to 0.5 parts by weight and one or two selected from the group consisting of alkylbenzene sulfonate and alkyl sulfate.
The second invention in which 0.001 to 0.05 parts by weight of one or more anionic surfactants are mixed.

By polymerizing ethylene tetrafluoride in an aqueous solution, a fine particulate resin of tetrafluoroethylene is obtained. The molecular chains of this fine resin have low intermolecular cohesive force,
It becomes fine cobweb-shaped fibers by receiving a slight compressive and shearing stress. Since the tetrafluoroethylene resin, which has become a cobweb-like fiber, captures the fine particles in the investment material, when the investment material particles are transported by air, only the fine particles are separated from the air by the cyclone separator. Instead, it is selectively prevented from being trapped by the air bag filter installed at the air outlet of the cyclone separator or being released through the air bag filter into the atmosphere.

Specifically, during the production of a dental phosphate-based investment material, a fine tetrafluoroethylene resin is added to the mill during the process of crushing the refractory material and the binder, and shearing / compression is performed by the mill. The stress is also applied to the tetrafluoroethylene resin.
In the tetrafluoroethylene resin, the C—C bond of the main chain of the molecular chain is strong, but on the other hand, the intermolecular attractive force to other molecular chains is extremely small. Ethylene molecules are finely fibrillated. This fiber traps the particles of the fine refractory material and the binder in the investment material in a entangled state. This phenomenon was also confirmed by the results of observation with a scanning electron microscope, and this shows the effect that the investment material particles are agglomerated in appearance, but this is due to the fineness of fine particles caused by the operation of granulating ordinary particles. Unlike such agglomeration, it does not affect the characteristics of the dental phosphate-based investment material because it is a light powder agglomeration in the state where fine particles are captured in the fine fiber mesh.

Since the fine particles in the investment material trapped in the fine fibers of the tetrafluoroethylene resin continue to be in the state of aggregating with the tetrafluoroethylene resin even during the pneumatic transportation, the final state of the pneumatic transportation. Since it is separated from the air by the cyclone separator installed at the stage, only fine particles are selectively captured by the air bag filter installed at the air outlet of the cyclone separator, or this air bag filter is used. It is prevented from passing through and being released into the atmosphere. As a result, since the fine particles in the investment material are contained in the investment material without being removed, the characteristic values of the investment material after pneumatic transportation, such as the investment material without addition of tetrafluoroethylene resin, especially It is possible to prevent such phenomena that the setting expansion value and the thermal expansion value decrease and the compression strength after curing decreases.

If the amount of the mixed tetrafluoroethylene resin is less than 0.01 parts by weight, the action of capturing the fine particles of the dental phosphate-based investment material is insufficient and the loss of the fine particles due to air transportation is prevented. The effect is not sufficiently exerted, and as a result, the settling expansion value and the thermal expansion value, which are important properties of the investment material, become unstable. For this reason, the lower limit of the amount of tetrafluoroethylene resin added is defined as 0.01 parts by weight.

The reason why the upper limit of the amount of the tetrafluoroethylene resin added is set to 0.5 part by weight is as follows. As mentioned above, tetrafluoroethylene resin finely fibrillates when subjected to shearing / compressive stress, but if the amount of addition is excessive with respect to the investment material, it not only captures fine particles but also larger particles. Even if it works, a phenomenon occurs in which the powder aggregates into a granular shape. The step of discharging the investment material powder from the mill is performed by opening the lid of the mill and receiving the powder falling from the discharge port while rotating the mill with the hopper. Agglomeration in the form of granules reduces the amount of powder discharged from the outlet of the mill, and as a result, discharge time is increased as much as possible. Also, the investment material remaining in the mill continues to be pulverized by the rotation at the time of discharge from the mill, but the efficiency of mill pulverization is determined by the amount of powder and the relative proportion of mill balls, and the proportion of mill balls is As the grinding efficiency increases exponentially as the size increases, the discharge time from the mill becomes longer, and the powder finally discharged from the mill is extremely excessively ground compared with the powder discharged first. The nature is completely different,
Adjustment after crushing becomes meaningless. For this reason, the upper limit of the addition amount of the tetrafluoroethylene resin is defined as 0.5 part by weight in view of the limit of the discharge time from the mill.

In the second invention, in addition to the composition of the first invention, 0.001 to 0.001 of one or more anionic surfactants selected from the group consisting of alkylbenzene sulfonates and alkyl sulfates is added. The reason for adding 0.05 part by weight is as follows.

The tetrafluoroethylene resin has a very strong water repellency, and when the investment material containing the same is kneaded with a kneading solution, a feeling of operation in use called "familiarity between the investment material and the kneading solution" is obtained. Adversely affect. Specifically, the wettability of the powder and the liquid deteriorates, the powder and the liquid cannot be mixed in a short time, and the powder floats on the liquid, making it difficult to perform the kneading operation. Although this property does not directly affect the performance and properties of the investment material itself, it causes a problem in operability during use such as kneading property. In order to solve this problem, we added an anionic surfactant to prevent the phenomenon of "familiarity with the kneading liquid" at the time of kneading by adding tetrafluoroethylene resin, and wetting the powder with the liquid. The second aspect of the present invention aims to improve the compatibility and the kneadability.

The anionic surfactant is added for the above reason, but the nonionic surfactant is effective in improving the property deterioration of "compatibility with the kneading liquid" due to the addition of the tetrafluoroethylene resin. Requires a large amount of addition, and as a result tends to lower the compressive strength of the cured product of the investment material, and causes the mold to break due to the casting pressure when the molten metal flows in, which is not desirable. Alkylbenzene sulfonate and alkyl sulphate are preferable because they improve the "familiarity with the kneading liquid" in a small amount compared with nonionic surfactants, and the compression strength of the cured investment material is not reduced. .

Sodium dodecylbenzene sulfonate is used as the alkylbenzene sulfonate which is an anionic surfactant, and sodium lauryl sulfate, potassium lauryl sulfate, sodium myristyl sulfate, sodium cetyl sulfate and stearyl sulfate are used as the alkyl sulfate. Sodium is used.

The amount of the anionic surfactant added is 0.001
If the amount is more than the weight part, improvement in "familiarity with the kneading liquid" was confirmed, so the lower limit of the addition amount was defined as 0.001 part by weight. On the other hand, the upper limit is defined as 0.05 parts by weight, the larger the amount added, the more "compatibility with the kneading liquid" at the time of kneading,
This is because it was confirmed that if the amount of addition exceeds a certain level, it affects important properties of the investment material, namely "setting time", "storage stability" and "compressive strength". In particular, the decrease in `` compressive strength '' causes casting defects such as casting burrs during casting, and the addition amount that does not adversely affect the properties of the investment material in practice is 0.
Since it was verified by experiments that the amount was 05 parts by weight, the upper limit of the addition amount of the anionic surfactant was defined as 0.05 parts by weight.

[0022]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention. Examples 1 to 10 have the compositions shown in Table 1, Comparative Examples 1 to 9 have the compositions shown in Table 3, magnesium oxide and ammonium dihydrogen phosphate as binders,
Quartz and cristobalite were used as the refractory material, and in Examples 1 to 10 and Comparative Examples 3 to 9, tetrafluoroethylene resin was blended. Further, Examples 6 to 10 and Comparative Example 7 were used.
In Nos. 9 to 9, an anionic surfactant was added.

The characteristic tests shown in Tables 2 and 4 were carried out by the following methods. Specifically, the test compounding ball mill having an internal capacity of 100 liters was used to perform crushing and mixing on a scale with the total weight of the investment material being 50 kg. First, the refractory material such as quartz and cristobalite and, in some cases, a powder of tetrafluoroethylene resin, which is a fine particle capturing material, were charged into a mill and ground until the refractory material exhibited a predetermined particle size distribution. After that, magnesium oxide and ammonium dihydrogen phosphate, which are binders, and, if necessary, an anionic surfactant are added to the mill, and the mixture is pulverized and mixed to adjust the setting time and fluidity, and then the mill. Discharged from the
Stored in hopper. The powder of tetrafluoroethylene resin is
Shear and compression stresses are applied in the crushing and mixing process of refractory materials and binders to form fine fibrous materials that capture the fine particles of the investment material. From the investment material stored in the hopper, 1 kg of each is randomly sampled 5 times for a characteristic test and a total of 5 kg is sampled. The remaining investment material of 45 kg is pneumatically transported by an air transportation device and buried by air transportation. It was verified how much fine particles of the wood were lost, and what kind of effect it had on the properties of the investment material. Samples after air transportation are 5 kg randomly, 1 kg each, as before transportation.
Was sampled and used as a sample.

The characteristics of each sample were measured according to the method specified in JIS T 6601 "Gypsum-based investment material for dental casting" before and after pneumatic transportation. In addition, the degree of loss of fine particles is determined by the particle size distribution analyzer “SA” manufactured by Shimadzu Corporation.
LD1100 type "is used, and the measurement range B is automatically measured.
This was done by comparing the volume percentage of particles below 9 μm. As for the evaluation method of the fitting accuracy of the cast body, a wax pattern was prepared according to the usual method on the MOD model of ADA No. 2 test body manufactured by Nissin Co., embedded with each investment material, and heated 60 minutes after the start of kneading After the temperature is raised to 800 ° C in 150 minutes and moored for 30 minutes, the mold is brought to a uniform state of 800 ° C, and a dental centrifugal casting machine is used to make a dental porcelain baking gold alloy made by GC. "Product name: Gicerabond Type II Gold Hard" is cast, and after digging out the cast body, sandblasting with JIS # 240 mesh alumina powder is performed, and the burned investment material and oxide film are removed and returned to the MOD model. The amount of uplift was measured using a projector, and the matching accuracy was evaluated based on its size. Each characteristic value is an average value of repeated 5 times measured with a sample of 1 kg each before and after pneumatic transportation, and the degree of data variation is expressed by standard deviation.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

Confirmation of the effect of trapping fine particles by the addition of the tetrafluoroethylene resin is clear from the composition of Table 1 and the characteristic values of Table 2. In Examples 1 to 10, 0.01 to 0.5 parts by weight of tetrafluoroethylene resin is added as a fine particle capturing material. As is clear from the characteristic values in Table 2, it was confirmed that before and after pneumatic transportation, the values of setting expansion, thermal expansion and compressive strength tended to decrease due to a slight loss of fine powder during pneumatic transportation. On the other hand, the standard deviation, which indicates the degree of variation, may increase slightly or, on the contrary, decrease. However, the decrease in these characteristic values and the variation in the variations do not affect the casting accuracy of the cast body, which is the most important property as a dental phosphate-based investment material, and there is a statistically significant difference between the two. No difference was confirmed, and both had similar casting accuracy. From these facts, in Examples 1 to 10, fine particles of cristobalite or quartz, which are the refractory material in the investment material, are formed into fibers of the ethylene tetrafluoride resin in the pulverization process by the ball mill in which the investment material is added with the tetrafluoroethylene resin. , And the effect of capturing fine particles of the binding material ammonium dihydrogen phosphate and magnesia, and there is no difference in physical properties between before and after pneumatic transportation, and as a result, The effect of the present invention could be confirmed without any deterioration in casting precision, which is the most important characteristic in practical use.

On the other hand, in Comparative Examples 1 and 2, the composition is the same as in Examples 1 and 2 except for the tetrafluoroethylene resin, but in Comparative Examples 1 and 2, no tetrafluoroethylene resin is added. Therefore, fine particles are lost during pneumatic transportation, and as a result, characteristic values are different before and after pneumatic transportation as shown in Table 4. Specifically, the condensation expansion value and the thermal expansion value, which are the characteristics that affect the dimensional accuracy of the cast body, the value after transportation is lower than the value before transportation before and after pneumatic transportation, This reduces the fitting accuracy of the cast body. In addition to that, a big problem is a phenomenon that the value of the standard deviation showing the degree of variation is large. For this reason, when casting is performed using the investment material of Comparative Examples 1 and 2, the casting precision deteriorates and the casting precision easily varies. The deterioration of the casting precision due to the decrease in the expansion value can be solved to some extent by other clinical measures (selection of the thickness and material of the liner backing the inside of the casting ring, etc.). However, the countermeasure against the large variation cannot be solved by the clinical technique, which is a big problem in the clinical use.

Similarly, in Comparative Examples 3 and 4 in which the amount of tetrafluoroethylene resin added is less than the lower limit of the range of the present invention, there is a difference from Examples 3 and 4 before pneumatic transportation. Although not confirmed, a decrease in conformity accuracy and an increase in conformity were confirmed after pneumatic transportation, and the effect of the addition of tetrafluoroethylene resin was not exhibited.

Examples in which the addition amount of the tetrafluoroethylene resin exceeds the upper limit of the present invention are Comparative Examples 5, 6, 8 and 9. The tetrafluoroethylene resin is a substance having a particularly strong water repellency, the addition amount thereof is 0.8 to 1.0 part by weight, and the anionic surfactant for improving the kneading operability is not blended. 6
In this case, the kneading operability was extremely deteriorated, and it was impossible to knead with the usual method of kneading the investment material in dentistry, and it was also impossible to measure the characteristics. In Comparative Examples 8 and 9 in which an anionic surfactant was added, the kneading operability was evaluated as “good”, but the investment material was discharged from the mill due to the excessive addition of the tetrafluoroethylene resin. In the process, the phenomenon that the investment material powders agglomerate with each other reduces the amount discharged from the discharge port, and the rotation of the mill for discharging crushes the remaining investment material and causes excessive crushing and further aggregation. However, there was a vicious cycle in which the discharge from the mill was delayed, and the characteristics of the powder, especially condensation expansion and thermal expansion, became large at the beginning of the discharge and at the end of the discharge, causing variations in the investment material before pneumatic transportation. . In addition, the time required for discharge became longer, and the actual operation became impossible. In addition, there was also a test piece in which the setting expansion and the thermal expansion value became too large due to excessive pulverization and the casting precision deteriorated. From the above results, it was confirmed that the upper limit of the addition amount of the tetrafluoroethylene resin is 0.5 parts by weight due to the problem of pulverization due to the time of discharging and the rotation during discharging.

Further, in Examples 1 to 4 of Table 1, when a tetrafluoroethylene resin, which is a highly water-repellent substance, is added to the investment material, if the addition amount is up to 0.1 part by weight, The property of "familiar with the kneading liquid" was evaluated as "normal" even if the surfactant was not mixed in the investment material. This “ordinary” rating is specifically compared to the current dental phosphate-based investment material product, “good” is higher than the current product, and “ordinary” is the current product. It shows that they are equivalent. In Example 4, when the amount of the tetrafluoroethylene resin added increased to 0.3 parts by weight, the "familiarity with the kneading liquid" showed a tendency to decrease and the evaluation was "slightly difficult". The specific meaning of the evaluation of "somewhat difficult" is that it can be mixed in practice, but it is "familiar with the mixing liquid" rather than the current product.
Indicates that the blendability is poor and that the blending is poor.
When the amount of the tetrafluoroethylene resin added in Example 5 was 0.5 parts by weight, the miscibility was lowered, but it was barely usable in clinical use.

As described above, the addition of a tetrafluoroethylene resin having strong water repellency to the phosphate-based investment material reduces the kneading property, but Examples 6 to 10 exhibit this characteristic. An anionic surfactant was added for improvement, and it was confirmed that the kneading operability was improved by adding the anionic surfactant. Specifically, in the comparison between Example 1 and Example 6, the only difference in formulation is the presence or absence of the addition of an anionic surfactant, but in Example 1, the evaluation of the kneading operability was " It is "normal" but is "good" in Example 6. Similarly, in the comparison between Example 2 and Example 7, there is a difference in kneading operability depending on whether or not an anionic surfactant is added, but Table 2
As can be seen from the above, in addition to properties such as condensation expansion, thermal expansion, compressive strength, and volume of particles of 1.9 μm or less, the accuracy of fitting, which is the most important property as an investment material, is affected by the addition of an anionic surfactant. Was not confirmed.

As an effect of adding an anionic surfactant, in Examples 9 and 10, 0.3 parts by weight and 0.5 parts by weight of tetrafluoroethylene resin were added, respectively, which were considerable amounts. The operability was evaluated as “good”.
On the other hand, in Examples 4 and 5 having the same composition other than the anionic surfactant, the kneading operability was evaluated as “somewhat difficult” because no anionic surfactant was blended. By comparing these examples, it was confirmed that if the amount of the anionic surfactant added was up to 0.05 parts by weight, the physical properties were not significantly affected.

The basis for defining the lower limit of the addition amount of the anionic surfactant as 0.001 part by weight is as follows.
In Comparative Example 7, 0.5 part by weight of tetrafluoroethylene resin was added, and the kneading operability was “slightly difficult”. As an example of adding 0.5 parts by weight of tetrafluoroethylene resin, there are Example 5 and Example 10 in addition to Comparative Example 7. In Example 10, 0.05 part by weight of an anionic surfactant was added. The sum operability is evaluated as "good". On the other hand, Example 5
No anionic surfactant was added, and the evaluation is "somewhat difficult". In Comparative Example 7, the anionic surfactant was 0.
[0007] Although added in parts by weight, it is also "slightly difficult",
The effect of adding the anionic surfactant was not confirmed.
On the other hand, comparing Example 1 and Example 6, the difference in composition is only the presence or absence of an anionic surfactant, and the addition amount is 0.00
Although the amount was 1 part by weight, the effect on the kneading operability was clearly shown, and the evaluation was changed from “normal” to “good”. For the above reasons, the lower limit of the addition of the anionic surfactant for improving the kneading operability is defined as 0.001 part by weight.

The upper limit of the amount of anionic surfactant added is set to 0.
The basis for defining 05 parts by weight is as follows. Comparative Example 8
And the addition amount of the tetrafluoroethylene resin of Comparative Example 9 is 0.8 to
Although it exceeds 1.0 part by weight and the upper limit of the present invention, the addition amount of the anionic surfactant is also 0.1 to 0.2 parts by weight and exceeds the upper limit of the present invention, and therefore the evaluation of the kneading operability is “good”. Is.
However, excessive addition of the anionic surfactant significantly reduces the compressive strength among the characteristic values. Although not shown in Table 2, it causes a serious clinical defect that the setting time, which is an important property as a phosphate-based investment material, is delayed. A decrease in compressive strength is a phenomenon that must be avoided because it decreases the strength of the mold and causes the mold to break due to the pressure caused by the inflow of molten metal during casting, which is a major cause of fatal casting defects such as the formation of casting burrs. . It has been concluded from conventional experiments and experience that the value of the compressive strength at which casting burrs do not occur should be 4.0 MPa or more, and in Comparative Examples 8 and 9, the value is below this value, and therefore, it is cast in a cast body. A test body having a burr defect was confirmed. It is considered that this theory is correct because there were no casting burrs in the test pieces produced by other molds. From the above experimental results, the upper limit of the amount of the anionic surfactant added was defined as 0.05 parts by weight in view of the compressive strength and in consideration of safety.

[0038]

As described above in detail, the dental phosphate-based investment material composition according to the present invention comprises magnesium oxide and ammonium dihydrogen phosphate as a binder, and quartz and cristobalite as a refractory material. The tetrafluoroethylene resin is added to the mixture to be mixed, and the fine particles of the tetrafluoroethylene resin are made into fine fibers in the crushing step to capture the fine particles in the investment material and Since it is possible to prevent the loss of fine particles, as a result, a dental phosphate-based investment material with stable characteristic values such as setting expansion and thermal expansion can be obtained, and it is possible to manufacture a dental metal restoration with high dimensional accuracy. It has become possible.

As for the deterioration of the kneading operability due to the addition of the tetrafluoroethylene resin having high water repellency, one or more selected from the group consisting of alkylbenzene sulfonates and alkyl sulfates. It has become possible to solve the above problems by adding the anionic surfactant. And as an attendant effect, the effect of preventing the scattering of fine particles in the investment material during the kneading operation of the investment material at the time of the mold preparation by the addition effect of tetrafluoroethylene resin and the effect of capturing fine particles by fiberizing in the crushing process Also got.

The value of the dental phosphate-based investment material composition according to the present invention having various effects as described above is extremely great for contributing to the field of dentistry.

Claims (2)

[Claims] 1. A tetrafluoroethylene resin based on 100 parts by weight of a mixture composed of a) magnesium oxide and ammonium dihydrogen phosphate as a binder, b) quartz and cristobalite as a refractory material.
A dental phosphate-based investment material composition, characterized in that 0.01 to 0.5 parts by weight are mixed. 2. A tetrafluoroethylene resin based on 100 parts by weight of a mixture composed of a) magnesium oxide and ammonium dihydrogen phosphate as a binder, b) quartz and cristobalite as a refractory material.
0.01 to 0.5 parts by weight and one or two selected from the group consisting of alkylbenzene sulfonate and alkyl sulfate.
A dental phosphate-based investment material composition, wherein 0.001 to 0.05 parts by weight of one or more anionic surfactants are mixed.