JPH0597622A - Production of glass powder for glass ionomer cement - Google Patents

Abstract

PURPOSE:To obtain the subject glass powder substantially extending operational time without having adverse effects on the physical properties of cured cement by heat treatment of a mixture of glass powder with a carboxylic acid. CONSTITUTION:Aluminosilicate glass powder to be used as a powder component for glass ionomer cement is incorporated with 0.1-10 (pref. 0.2-5)wt.% of a carboxylic acid such as acetic acid, salicylic acid, tartaric acid, succinic acid, citric acid or ethylenediaminetetraacetic acid followed by mixing using e.g. a oscillating mill or ball mill. The mixture is treated under heating at 100-400 (pref. 150-250) deg.C for 4-24hr. The resultant aluminosilicate glass powder is kneaded with a polyalkenic acid such as polyacrylic acid in the presence of water to carry out reaction to prepare glass ionomer cement for dental use. By altering kind and/or amount of the carboxylic acid, heating temperature and/or time, etc., the operational time and/or setting time for the glass powder easily be regulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminosilicate glass powder mainly used as a powder component of a dental glass ionomer cement.

[0002]

[Prior Art / Problems] Dental glass ionomer cement is aluminosilicate glass powder (hereinafter referred to as glass powder).
And polyalkenoic acid such as polyacrylic acid (hereinafter referred to as polyacid) are kneaded in the presence of water, and the reaction is cured. This cured product is less harmful to the pulp and has excellent adhesiveness to tooth substances such as enamel and dentin. Further, it has been confirmed that the cured product releases a small amount of fluoride ions in the oral cavity over a long period of time and thus has an effect of imparting caries resistance to enamel and dentin.

As described above, the glass ionomer cement has excellent characteristics that other dental cements such as zinc phosphate cement do not have, but whether or not the cement is actually widely accepted in the market depends on these properties. Of course, not only physical and engineering properties such as crushing resistance, disintegration rate, and translucency, but also easiness in clinical use, that is, operability is emphasized with a specific gravity equal to or higher than these properties. The operability refers to various properties of the kneaded product from the start of kneading the glass powder, the polyacid, and the water at a predetermined weight ratio to a certain period of time, including the operating time and the curing (solidification). There is time, consistency, etc., and the standard for these measuring methods is J
It is defined in detail in IS and BS. In actual clinical practice, dental hygienists and doctors can work with plenty of time, so the operating time is as long as possible, and conversely, cement that can be hardened and put into practical use immediately after being placed (wearing) in the oral cavity is desired. It is rare.

Therefore, much research has been conducted in order to further improve the operability. For example, tartaric acid as a regulator is added to a polyacid solution to extend the operation time (Japanese Patent Publication No. 55-8019), glass powder is washed with acid to remove cations such as calcium ions present on the powder surface. Then, a method of substantially delaying the curing reaction with a polyacid (JP-B-59-5536), a method of adding a fluoro complex salt to a polyacid solution (JP-B-56-37964), and a glass frit in the presence of tartaric acid, Finely pulverized by dry method,
A method of treating tartaric acid and glass powder mechano-chemically (Japanese Patent Laid-Open No. 225567/1988) has been proposed.

As described above, many proposals have been made to improve the operability of the glass ionomer cement, but it is still difficult to say that it is sufficient. In particular, many clinicians (dentists) are familiar with zinc phosphate cement with a long history and are used to it, so it is considered to be insufficient compared with the operability of this cement, which is one of the factors that hinder the spread of glass ionomer cement. ing. In addition, the improvement of operability, especially the extension of operation time, can be applied not only to the field of dentistry but also to the field of surgery and industrial fields such as waterworks (leakage countermeasures) and construction work for interior construction. Expected to be. In addition, in the method in which the third component is simply added, it is necessary to add a large amount of these components, which is likely to cause a remarkable decrease in the physical properties of the hardened cement.

[0006]

[Means for Solving the Problems] As a result of earnest research on the properties of the glass powder, the present inventor surprisingly solved the above problems, and as a result, surprisingly, the glass powder as a powder component of the glass ionomer cement was treated in the presence of carboxylic acid. It was found that the operability was significantly improved in the subsequent kneading and curing reaction with the cement liquid component (polyalkenoic acid) by simply heat-treating, and the present invention was completed. Usually, when the operation time is increased, the solidification (curing) time also becomes remarkably long, and the upper limit of the solidification time of JIS standard (T6602) often exceeds 8 minutes in many cases. However, according to the present invention, the operation time can be greatly extended while maintaining the coagulation time within the range of JIS standard by an extremely simple process.
In the present specification, the operation time is the British standard “dental glass ionomer cement” BS6039 (198).
Comply with 1).

The present invention is widely applicable to glass for glass ionomer cement, that is, aluminosilicate glass powder used as a powder component of glass ionomer cement. This glass powder is usually silica (Si
O ₂ ), alumina (Al ₂ O ₃ ) and calcium component (C
aO) as a main component, and further contains 0 to 20 wt% of a fluorine component (F), 0 to 10 wt% of a phosphorus component (P ₂ O ₅ ), 0 to
It contains 10 wt% of sodium component (Na ₂ O) and the like. For example, Japanese Examined Patent Publications 50-24328 and 59-553.
See 6. However, it is not intended to be limited to these, as long as the operability improving effect of the present invention is obtained,
It includes aluminosilicate glass powders of various compositions. The glass for glass ionomer cement is manufactured by a conventional method, for example, as follows. That is, a natural or artificial raw material is weighed in a predetermined weight and sufficiently mixed. Next, this mixture is homogeneously melted at a high temperature of 1100 ° C. to 1500 ° C. and then rapidly cooled to prepare a glass frit. The glass frit is dry finely pulverized by an ordinary pulverizing method, for example, a ball mill, a vibration mill, a jet mill, etc., but the final particle size of the powder is 50 μm or less at the maximum, preferably 40 μm, and 25 μm or less for wearing. Is desirable. On the other hand, when the amount of fine powder of 1 μm or less is increased, the physics and engineering characteristics are improved, but the operability and the like are decreased. Then, the glass powder thus obtained is subjected to a heat treatment in the presence of the carboxylic acid of the present invention. Glass powders suitable for use according to the invention are untreated (without treatment according to the invention) when kneaded with a commercially available polyacid solution containing tartaric acid, for example by the method specified in British Standard (BS) 6039. The effect is remarkably exerted on the glass powder showing the characteristics that the operation time is within 3 minutes, preferably within 2 minutes, and the coagulation time is within 7 minutes, preferably within 5 minutes.

The carboxylic acid used in the heat treatment of the glass powder improves the operability by slightly delaying the initial curing reaction between the glass powder and the polyacid, and does not affect the properties of the cement hardened product at the end of the reaction. Select. Carboxylic acid has a carboxyl group (-COO in the molecule).
H) is an organic acid having a carboxyl group 1
Acetic acid, lactic acid, salicylic acid, gluconic acid, 2 oxalic acid, tartaric acid, succinic acid, maleic acid, malic acid, 3 citric acid, 4 ethylenediaminetetraacetic acid (E
DTA) acid and the like. Also, a mixture of these may be used. The property is solid or liquid, for example, tartaric acid,
Many of the above carboxylic acids such as succinic acid are solid (powder) at room temperature. In the case of powder, the average particle size is preferably fine in order to efficiently achieve a uniform mixed state with the glass powder with a small amount, and is preferably equal to or smaller than the average particle size of the glass powder.

A predetermined amount of such solid or liquid carboxylic acid is added to the glass powder, and both are mixed. The glass powder and the carboxylic acid can be mixed by using a V-type or ribbon-type mixer, but when the carboxylic acid is a powder, the difference in specific gravity between the powders and the difference in the starting particle size cause a sufficient mixing. For this purpose, it is preferable to use a vibration mill, a ball mill, or the like that causes shearing force or impact force. Then, this mixture is transferred to an oven or a heat treatment furnace and heat-treated at a temperature of 100 ° C. or higher and 400 ° C. or lower for a predetermined time. If it is less than 100 ° C, the effect of heating is small even for a long time, while if it exceeds 400 ° C, the heat-treated product is colored from gray to black due to thermal decomposition of carboxylic acid or the like for a relatively short time, so that its commercial value is significantly reduced. .. Depending on the purpose of use of cement and the type of carboxylic acid used, the treatment temperature and holding time may be appropriately selected,
Usually, the operability is sufficiently improved by keeping the temperature at 150 to 250 ° C for several hours. The treatment time is too short at 0.1 hours, preferably 4 to 24 hours. Regarding the amount of carboxylic acid required, it is 0.1 based on the weight of the glass powder.
If it is less than wt%, its effect is insufficient, and if it exceeds 10 wt%, it affects the physical properties of the hardened cement, so it is preferably 0.2% or more and 5% or less.

Although the details of the action of the carboxylic acid in the present invention are not clear, there are some species in which the divalent alkaline earth metal such as calcium (Ca) existing near the glass surface and the added carboxylic acid are reacted by heating. This is probably because a compound, for example, a calcium salt is produced, and thus the curing and polymerization reaction of ordinary polyacid and calcium or the like is suppressed. or,
As a means for detecting the formation of calcium salt, a Fourier transform infrared spectroscopic analysis method (DRFT-I) by the diffuse reflection method is used because of its small amount and the presence on the powder surface.
R) is suitable, and changes in the state of organic substances such as carboxylic acids can be measured. Then, the glass ionomer glass powder obtained by the production method of the present invention is 1700 in DRFT-IR.
A clear absorption peak was observed between ˜1600 cm ⁻¹ (see FIG. 4).

[0011]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

[0012]

Example 1 Fluoroaluminosilicate glass powder having an average particle size of 4.2 μm by X-ray transmission method (specific composition (wt
_{%) SiO 2: 31, Al} 2 O 3: 28, CaO: 9, B
aO: 11, F: 12, P 2 O 5: 7, ZnO: 2 in),
A predetermined amount of d-tartaric acid (purity of 98% or more) was added, and the mixture was dry-mixed for 30 minutes in a menor mortar. Then, the mixture was transferred to an oven, heated at each temperature for 5 hours, and then taken out and allowed to cool in a desiccator. This heat-treated glass powder was kneaded with a commercially available polyacid solution for curing (registered trademark, Hybond C polyacrylic acid copolymer manufactured by Matsufu Co., Ltd., containing tartaric acid at about 8%) at a powder / liquid ratio of 1.5 / 1. Then, the operation time of the cement (paste) at that time was examined with BS6039, and the coagulation time was examined according to JIS T6602.

Heat treatment temperature and carboxylic acid (d-tartaric acid)
Table 1 shows the relationship between the added amount and the operation time and the coagulation time.
The comparative example is a case where the glass powder was simply heat-treated (without addition of tartaric acid).

[0014]

[Table 1]

According to Table 1, as compared with the comparative example in which tartaric acid was not added, 0.5 to 5% of tartaric acid was added and the sample was heat treated. The heat-treated glass powders 1 to 4 have extended operating time. Further, it can be seen that the operation time can be further extended when the heat treatment is performed at each temperature of 150 ° C. to 300 ° C., as compared with the case of simply treating with tartaric acid at room temperature (RT).

Although the coagulation time is extended,
Except when the amount of tartaric acid added is large (5.0 wt%) and the heat treatment temperature is high (300 ° C.), all are within 8 minutes of the JIS standard. In addition, most of the examples are within the more preferable coagulation time of 6 minutes.

[0017]

Example 2 Fluoroaluminosilicate glass powder having an average particle size of 3.5 μm (composition: SiO ₂ : 30 wt%, A
_{l 2 O 3: 24%,} SrF 2: 33%, AlPO 4: 12
%, Na ₂ O: 1%) to which various carboxylic acids were added,
Heat treatment was performed at 0 ° C. for 7 hours. Then, this heat-treated glass powder was kneaded with a curing polyacid solution in the same manner as in the above-mentioned examples, and the operating time and setting time of the cement were examined. The results are shown in Table 2.

[0018]

[Table 2]

According to Table 2, the heat treatment glass powder heat-treated by adding various carboxylic acids other than tartaric acid also had a coagulation time within 8 minutes of JIS standard (within 6 minutes in all Examples). It was confirmed that the operation time was remarkably extended while it was contained.

[0020]

Third Embodiment Sample No. 1 of the first embodiment. For 3 and its comparative sample (glass powder was simply heat-treated without adding tartaric acid), the physical and engineering properties of the cured (solidified) cement were investigated in accordance with JIS6602. The results are shown in Table 3.

[0021]

[Table 3]

As can be seen from Table 3, the sample of the example shows the same physical and engineering properties as the sample of the comparative example. Incidentally, the thinner the coating thickness, the higher the adhesive strength, the longer the life and the less discomfort, which is preferable, and the glass powders of the examples are also very excellent in this respect.

[0023]

Example 4 a) Tartaric acid (purity of 98% or more), b) Glass powder (having the composition of Sample No. 1 of Example 1), and c) Sample No. 1 of Example 1. Tartaric acid-added glass powders having the same composition as in Example 4 were weighed in glass petri dishes, lightly capped, and then heat-treated at 200 ° C. for 8 hours. The change in weight and the residue after the treatment were examined by diffuse reflectance Fourier transform infrared spectroscopy (DRFT-IR). The results are shown in Table 4 and FIGS.

[0024]

[Table 4]

From Table 4, c) Example 1 Sample No. It can be seen that the tartaric acid-added glass powder according to No. 4 retains carboxylic acid (tartaric acid) 3 times or more as compared with a) tartaric acid alone.

1 to 4 show the results of DRFT-IR measurement. FIG. 1 shows a) tartaric acid (at room temperature), FIG. 2 a) tartaric acid (after heat treatment at 200 ° C. for 8 hours), and FIG. 3 b). Is glass powder (at room temperature: same after heat treatment), and in Fig. 4 c).
[Example 1] The results of tartaric acid-added glass powder (after heat treatment at 200 ° C for 8 hours) having the same composition as that of Sample 4 are shown. As is clear from the comparison between FIG. 3 and FIG. 4, the sample c) according to the example shows that CO is between 1700 and 1600 cm ^−1.
There is a clear absorption peak that is probably due to
Incidentally, in Japanese Patent Laid-Open No. 63-225567 (in which carboxylic acid is added during grinding but no heat treatment is applied), tartaric acid is 1%.
Sharp absorption peaks were shown at about 3300 and 3400 cm ⁻¹ after the addition, but they did not appear in the sample of this example.

[0027]

[Example 5] Tartaric acid and Example 1 Sample No. TG-DTA (weight, differential thermal analysis method) was used to measure the state change (weight, heat generation, decomposition, etc.) of 5% tartaric acid-added glass powder, which is the same sample as in No. 4, when heated to 300 ° C at 5 ° C / min in air. ).

FIG. 5 is a TG-DTA curve for tartaric acid. It can be seen from FIG. 5 that tartaric acid is stable up to about 170 ° C. and melts at about 172 ° C. But 17
The TG curve changes to the right from 5 ° C, becomes sharper from 257 ° C, and becomes 0 at 275 ° C or higher. On the other hand, the DTA curve shows a large absorption peak at 172 ° C, that is, an endothermic peak (melting), and shows a second endothermic peak at 275 ° C. From these, it is understood that tartaric acid alone starts to decompose at 175 ° C., rapidly at 257 ° C., and dissipates at 270 ° C. or higher.

FIG. 6 shows the sample No. 1 of Example 1. TG-DT about 5% tartaric acid addition glass powder which is the same sample as 4
It is an A curve. As in FIG. 5, the unreacted tartaric acid is about 175.
Thaw at ℃. At temperatures above this, the TG curve shows a downward slope to the right (indicating a decrease in weight) due to the decomposition of tartaric acid, but the decomposition rate above 200 ° C is slower than in the case of Fig. 5, and even at 300 ° C the weight is 4%. A reduction (5% weight loss with tartaric acid alone), ie 1% tartaric acid remains.

Therefore, it is clear from this point that in the case of the samples of the examples, the rate of weight loss at high temperature is slow, and tartaric acid remains even after heating at 300 ° C.

[0031]

Example 6 5 parts of tartaric acid was added to 100 parts of glass powder of various particle sizes having the composition of sample 1 and thoroughly dry mixed. Next, this mixture was heat-treated at 200 ° C. for 8 hours to prepare cement at a powder / liquid ratio of 1.5 / 1, and the operation time and coagulation time at that time were examined (Table 5).

[0032]

[Table 5]

According to Table 5, even when tartaric acid is added to glass powders having various particle sizes and heat treated, the operation time can be remarkably extended while keeping the coagulation time within 8 minutes of JIS standard.

[0034]

Example 7: SiO ₂ : 26 wt%, Al ₂ O ₃ : 15
%, CaF ₂ : 23%, AlF ₃ : 12%, ZnO: 12
%, AlPO ₄ : 12%, average particle size 3.2
A glass powder of μm was treated in the same manner as in Example 2 to examine the heat treatment effect of carboxylic acid addition (Table 6). In Comparative Example, the heat treatment was performed in the same manner without adding carboxylic acid.

[0035]

[Table 6]

Table 6 shows that even when a relatively large amount of carboxylic acid is added, the operation time can be remarkably extended while keeping the coagulation time within 8 minutes of JIS standard.

[0037]

EFFECT OF THE INVENTION By the extremely simple treatment of mixing carboxylic acid and heat treatment, the operating time of the glass ionomer glass powder can be remarkably extended with almost no adverse effect on the physical properties of the hardened cement. Further, the operation time and the coagulation time of the glass ionomer glass powder can be easily adjusted by changing the kind and amount of the carboxylic acid or the heating temperature and time according to the application.

[Brief description of drawings]

FIG. 1 DRFT-IR spectrum diagram (tartaric acid: at room temperature)

FIG. 2 is a DRFT-IR spectrum diagram (tartaric acid: 200
After heat treatment at ℃ x 8 hours)

FIG. 3 DRFT-IR spectrum diagram (glass powder: at room temperature, the same after heat treatment)

FIG. 4 is a DRFT-IR spectrum diagram (Sample 1 of Example 1).
Glass powder with tartaric acid having the composition of 200 ° C. × 8 h
r After heat treatment)

FIG. 5 TG-DTA curve (tartaric acid)

FIG. 6 TG-DTA curve (tartaric acid-added glass powder having the composition of Example 1, sample 4)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Shibata, No. 1-36, Noritake Shinmachi, Nishi-ku, Nagoya-shi, Aichi Prefecture Noritake Company Limited Limited (72) Hideki Nonogawa 3-chome, Noritake Shin-cho, Nishi-ku, Aichi Prefecture No. 36 Noritake Company Limited Limited (72) Inventor Tetsuya Nakamura 2-20-3 Kasuga, Tsukuba City, Ibaraki Prefecture (72) Inventor Yoshitaka Goto 2-24-5 Umezono, Tsukuba City, Ibaraki Prefecture (72) Inventor Masa Nakayama Yang 1132-9, Ekuni, Tsuchiura-shi, Ibaraki Prefecture (72) Inventor Eiichi Masuhara 2-5-11, Honkomagome, Bunkyo-ku, Tokyo (72) Shigeo Komiya 3-7-10 Minamiurawa, Urawa-shi, Saitama Prefecture

Claims (6)

[Claims] 1. A method for producing glass powder for glass ionomer cement, which comprises heat-treating a mixture of glass powder and carboxylic acid. 2. The method according to claim 1, wherein the carboxylic acid for heat treatment is a carboxylic acid having 1 to 4 carboxyl groups in the molecule. 3. The method according to claim 1, wherein the glass powder before heat treatment has an operating time of 2 minutes or less and a solidification time of 5 minutes or less. 4. The method according to claim 1, wherein the carboxylic acid is added in an amount of 0.1 to 10 wt% based on the weight of the glass powder. 5. The manufacturing method according to claim 1, wherein the heat treatment temperature is 100 ° C. or higher and 400 ° C. or lower. 6. The production method according to claim 1, wherein the heat-treated glass powder shows a clear absorption peak between 1700 and 1600 cm ^{−1 by} a diffuse reflection method Fourier transform infrared spectroscopic analysis.