JPH0139402B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dental hydraulic cement composition, and particularly to a composition that has excellent compressive strength, operability, and storage stability. Zinc phosphate cement has traditionally been the mainstream dental cement, but the University of Manchester's
Polycarboxylate cement was developed by DC Smith and others, and was presented at the British Journal in 1968 under the title ``New Dental Cement.'' Since then, further research has been underway to improve it. Polycarboxylate cement has advantages over zinc phosphate cement, such as less irritation to the dental pulp, strong adhesion to tooth structure, and high tensile strength. On the other hand, the compressive strength of zinc phosphate cement is generally 1200 to 1300 Kg/ ^cm2 ;
The compressive strength of polycarboxylate cement is 700
The drawback is that it is only ^about ~900Kg/cm2.
In addition, polycarboxylate cement is generally
Approximately 50% polyacrylic acid aqueous solution (viscosity:
(approximately 5000 cps), but the liquid viscosity during mixing is significantly higher than that of zinc phosphate cement. Therefore, not only is the kneading operation difficult, but also the kneaded material adheres to the spatula filling device etc. during the filling operation into the tooth cavity, making it extremely difficult to operate. Therefore, the present inventor conducted research to develop a hydraulic polycarboxylate cement with emphasis on improving operability and proposed JP-A-53-67290. However, as a result of subsequent research, it was found that (1) although the cement of the earlier invention was considerably improved compared to conventional products, its viscosity was still high, making it somewhat difficult to operate when filling tooth cavities; 2) It has been confirmed that it is hygroscopic and if left unsealed in a storage container for about two weeks, it will become damp and cause problems such as a decrease in physical properties, especially pressure resistance. The present invention has been made with attention to these circumstances, and its purpose is to create a polycarboxylate cement that has the characteristics of the above-mentioned polycarboxylate cement, has high storage stability, and has good operability during filling. The object of the present invention is to provide a hydraulic dental cement containing the above. The cement of the present invention, which has achieved the above objects, is made by adding a carboxylic acid anhydride to a dental cement powder containing silicon oxide as an essential component and a hardening agent powder containing polyacrylic acid as a constituent component. The main point lies in the following points. That is, when the composition of the present invention is compared with the composition of the prior invention, changing the composition of the cement powder to make the compressive strength equal or higher and adding the acid anhydride powder improves the storage stability and the composition during kneading and application. It is characterized by improved operability. That is, by adding the acid anhydride, the cement composition was prevented from hardening due to moisture absorption during storage, and the viscosity of the composition as a whole was reduced by the addition of the acid anhydride, making it easier to fill tooth cavities. Although the mechanism by which hygroscopic hardening is prevented as described above has not yet been elucidated, it is thought that the acid anhydride is involved in the hygroscopic hardening of the cement composition in the following manner. That is, since cement compositions are generally hygroscopic, they absorb moisture from the air, form hydrates within the composition, and harden. However, if an acid anhydride is present here, moisture acts preferentially on the acid anhydride, causing a reaction to produce carboxylic acid from the acid anhydride, which seems to retard the hardening of the cement composition during storage. In addition, the free carboxylic acid produced forms salts with calcium ions, aluminum ions, etc., and also plays a role in improving adhesion to teeth during use. Each component used in the present invention will be described below. Dental cement powder is composed of silicon oxide as an essential main component and other components. In order to ensure strength, particularly compressive strength, as a dental cement composition, silicon oxide is essential, and as will be seen from the examples below, the most preferable content is as follows. Silicon oxide 30-60% by weight Aluminum oxide 5-35% by weight Calcium fluoride 5-25 Aluminum phosphate 5-20 Components other than silicon oxide are reactivity improvers during kneading with the curing agent described later, and especially What is necessary is aluminum oxide, calcium fluoride, and aluminum phosphate, and if necessary, cryolite, aluminum fluoride, etc. may be added. In addition, magnesium oxide or the like may be used in combination for the purpose of improving the crushability of the cement sintered body. The reasons for recommending the above-mentioned mixing ratios for the ingredients are as follows. That is, if the content of silicon oxide is too low, the compressive strength will be poor, and if the content is too high, the reactivity with the curing agent will decrease, which will also lead to a decrease in the compressive strength. Other components have the function of improving reactivity as described above, but if they exceed the above range, they cause deterioration in disintegration after firing. It has been found that an excessive amount of these inorganic fluorides causes a decrease in compressive strength. Furthermore, magnesium oxide, which was mentioned as another compounding agent, tends to disintegrate if too much is added, so it should be kept at 5% by weight or less. Next, we studied the interrelationship of the components within the range of blending ratios and came to the following conclusions. First, α = silicon oxide/aluminum oxide (weight ratio), β
= fluorine/aluminum oxide (weight ratio), to obtain the most preferable compressive strength, the value of α is preferably in the range of 2.1 to 2.4 under normal firing conditions, and the corresponding value of β is 0.2 to 2.4. The range is 1.1. On the other hand, under the firing conditions shown in Example 2 (firing time: 6 to 10 hours), the value of α is preferably in the range of 4.0 to 5.0, and the corresponding value of β is preferably in the range of 3.0 to 4.0. I understand. Next, although there are no restrictions on the mixing method or manufacturing method for this cement powder, it is desirable to perform a certain degree of firing treatment in order to maintain its strength as a dental cement. Although there are no restrictions on the firing conditions, it is generally recommended that the firing be performed at a temperature of 1000 to 1400°C, and for a firing time of 2 hours or more. Since the obtained fired product is a large, bonded mass, it must be crushed, but it is preferable to crush it to a diameter smaller than 350 mesh, and it is generally recommended to apply the jet crushing method. Next, the curing agent powder in the present invention will be explained. In this curing agent powder, a homopolymer of a compound selected from the group consisting of acrylic acid, methacrylic acid, other unsaturated carboxylic acids, and esters thereof may be used instead of a copolymer of two or more compounds. In this case, the degree of polymerization is preferably 40 to 300. Preferable representative examples of unsaturated carboxylic acids include maleic acid, itaconic acid, aconitic acid, fumaric acid, citraconic acid, and mesaconic acid. Preferred representative examples of corresponding esters of acrylic acid, methacrylic acid, and other unsaturated carboxylic acids include lower alkyl (such as methyl, ethyl, propyl, butyl, tert-butyl, pentyl,
(hexyl, etc.) esters, but these examples are not intended to limit the present invention. Next, regarding the water content of these hardening agent powders, it is generally recommended that it be 10% or less. The reason for this is that if the water content exceeds 10%, it will be difficult to form it into a powder and the effect of the present invention will be diluted. Moreover, if the water content becomes extremely high, there is a risk that a hardening reaction may occur during storage if it is mixed with silicon oxide powder in advance, which is not preferable. It is preferable that the water content in the curing agent powder is as low as possible, but since the economic efficiency of the dehydration process is also an issue, it is usually sufficient to keep it at about 0.05% or more. Next, in the present invention, a major feature different from conventional polycarboxylate cements is the addition of carboxylic acid anhydride, and this point will be explained. In the present invention, by adding a carboxylic acid anhydride, it was possible to obtain a polycarboxylate cement that maintains hydraulic properties and has high storage stability. Furthermore, since the cement has a low viscosity, it has the advantage of improved kneading operability and ease of filling into tooth cavities. Although the mechanism of action regarding these favorable results due to the addition of carboxylic acid anhydride has not been elucidated, it is considered as follows. Originally, the property of hydraulicity means the property that the crystalline compound in dental cement undergoes hydrolysis by mixing with water to create a hydrate, gradually becoming a hard gel-like structure or large crystals. Curing during storage is also thought to be due to similar reactions, and possible preventive measures include preventing the absorption of moisture or preventing the absorbed moisture from being available for the hydrolysis reaction described above. The addition of the acid anhydride of the present invention reduces the hygroscopicity of the composition, and the water absorbed into the cement powder is consumed in the hydrolysis of the acid anhydride itself, thereby delaying the hardening of the cement powder during storage. ing. The produced carboxylic acid then forms salts with calcium ions, aluminum ions, etc. in the cement, and has the secondary effect of improving adhesion to teeth during use. The above reaction can be expressed as follows. (In the formula, R: residue obtained by removing two carboxyl groups from a polybasic carboxylic acid, M: metal) Representative examples of such carboxylic acid anhydrides include aliphatic carboxylic anhydrides (such as glutaric anhydride,
succinic anhydride, diglycolic anhydride, acetylmalic anhydride, cisaconitic anhydride, itaconic anhydride, 2,3-dimethylmaleic anhydride, cis-4-cyclohexene-1,2-dicarboxylic anhydride, maleic anhydride, etc.) and dibasic acid anhydrides such as aromatic acid anhydrides (e.g. phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, 1,8-naphthalene dicarboxylic anhydride, etc.), as well as symmetrical and asymmetrical mixed acids. Anhydrous materials may also be used. Finally, regarding the blending ratio of dental cement powder, curing agent powder, and carboxylic acid anhydride, the preferred range is (95 to 50): (3 to 44): (2 to 6), and these can be used, for example, in a ball mill, etc. The mixture is uniformly mixed by The reason why the blending ratio in the above range is recommended is as follows. That is, for dental cement, if the mixing ratio exceeds the upper limit of the range, the composition becomes brittle in terms of material, and if it falls below the lower limit, the compressive strength decreases. Next, regarding the curing agent, if the upper limit is exceeded, there will still be problems with pressure resistance, and if it is below the lower limit, the bonding strength of the composition will be weakened and the material will become brittle. Furthermore, if the acid anhydride exceeds the upper limit, the hydraulic properties of the composition will be diluted, and if it falls below the lower limit, the storage stability, which is a characteristic effect of the present invention, will be lost. When using these compositions, weigh the required amount of the powder composition and use powder:water = 2.4:0.5 (weight ratio) when used for filling, and powder: water when used for bonding. Tap water may be added and kneaded so that the water ratio is 2.0:0.5 (weight ratio). When the composition of the present invention was stored in a sealed container and an accelerated deterioration test was performed, it was confirmed that the composition remained stable for two years. Furthermore, even if the cement is left open for a whole day, it has a longer storage stability of approximately one month than the previous hydraulic cement, making it very convenient to handle. Next, examples of the present invention will be described, but the following examples are not intended to limit the present invention. Example Cement powder, curing agent powder, and carboxylic acid anhydride powder were prepared according to the compounding ratio shown in Table 1, and the mixture was uniformly mixed to obtain a cement composition. However, the cement powder used was one obtained by mixing the raw materials, firing them, and then jet-pulverizing them into fine particles of 350 mesh passes. The three agents were processed in a ball mill for 3 hours and mixed uniformly. Add a predetermined amount of water to each of the obtained cement compositions (mixed powder) and knead them to a standard composition according to JIS standards.
The compressive strength, kneading state, and disintegration rate were measured according to the standard T-6602 "Dental Zinc Phosphate Cement", and the results shown in Table 1 were obtained. Nao 3
The formulation of the agent in Examples 1 to 4 was as follows: 3 to 5 parts by weight of acid anhydride powder was added to a mixed powder of 75 parts by weight of cement powder and 25 parts by weight of hardening agent.

[Table] *1 Since the cement contains a lot of fluorine, the firing time is longer to volatilize the fluorine.

Claims (1)

[Scope of Claims] 1. A dental cement powder containing silicon oxide as an essential component having the following component composition, a curing agent powder consisting of a homopolymer or copolymer of an unsaturated carboxylic acid or its ester, and an organic carboxylic acid anhydride. (95-50):(3-44):(2-6)
A hydraulic dental cement composition characterized in that it is composed of a mixture in a weight ratio of . Silicon oxide 30-60% by weight Aluminum oxide 5-35% by weight Calcium fluoride 5-25% by weight Aluminum phosphate 5-20% by weight 2. Cryolite: 15% by weight or less and/or fluorite in claim 1 Aluminum chloride: 15% by weight
A cement composition consisting of a dental cement powder containing: 3 In claim 1 or 2,
Dental cement powder is made from a mixture of each component.
Bake at 1000-1400℃ for at least 2 hours,
A cement composition that is finely ground to a diameter smaller than 350 mesh. 4. In claim 3, the dental cement is a cement composition finely pulverized by jet pulverization. 5. In any one of claims 1 to 4, the unsaturated carboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, itaconic acid, aconitic acid, fumaric acid, citraconic acid, and mesaconic acid. A cement composition that is more than a species. 6. The cement composition according to any one of claims 1 to 5, wherein the carboxylic anhydride is an aliphatic carboxylic anhydride or an aromatic carboxylic anhydride. 7. The cement composition according to any one of claims 1 to 6, wherein the polymer has a degree of polymerization of 40 to 300. 8. The cement composition according to any one of claims 1 to 7, wherein the curing agent has a water content of 0.05 to 10%.