JPH10338541A - Glass and dental ceramic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low expansion glass having a low firing temp. and excellent in chemical durability. SOLUTION: This glass contains silicon dioxide, aluminum oxide, boron oxide, lithium oxide and sodium oxide as essential components and satisfies 61-75 wt.% SiO2 , 3-20 wt.% Al2 O3 , 9-25 wt.% B2 O3 and 5-15 wt.% Li2 O+Na2 O contents (when the oxides are expressed in terms of SiO2 , Al2 O3 , B2 O3 , Li2 O and NaO2 ).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dental porcelain suitable for a novel glass and all-ceramic crown shell.

[0002]

2. Description of the Related Art In the field of ceramics for dental crowns, the demand for materials called all ceramics has been increasing in recent years. Traditionally, for aesthetic inlay or crown restoration,
A material called ceramics bonded to a metal core called metal bond porcelain has been used. However, metal bond porcelain has a problem that the internal metal does not transmit light, so that the same transparent feeling as natural teeth cannot be reproduced, and that gingiva is discolored by the influence of the metal. On the other hand, all-ceramics is a technique of forming the entire crown with ceramics without using a metal core. Since a translucent material is usually used for this ceramic, a natural transparent feeling similar to that of natural teeth is realized, and the problem relating to discoloration of gums is also solved. For this reason, the application range of all ceramics is expanding in combination with the improvement of its own material strength.

[0003] On the other hand, in order to pursue the aesthetics of restorations such as inlays and crowns, it is desirable that the structure has two or more layered structures similar to teeth. This is because the dental hard tissue has a two-layer structure of dentin and enamel, and visible light is scattered in a complicated manner in these layers or at the layer interface, and the scattered light has a significant effect on aesthetics. Therefore, it is indispensable for recent all-ceramic restorations to be a system capable of forming a two-layer structure of a core and a shell.

[0004] Conventional mica, apatite,
Crystallized glass such as diopside is mainly used, and these are formed by casting from a molten state or hot pressing. On the other hand, for the formation of the shell, a crushed product of glass or crystallized glass, which is usually called dental porcelain, is used. By sintering this dental porcelain in the form of a slurry with a kneading liquid, and then serving it on the surface of the core,
A shell is formed. At this time, it is necessary that the thermal expansion coefficients of the shell and the core be close to each other, otherwise, cracks are caused by internal stress in the molded product at the time of cooling after firing. If the thermal expansion coefficient of the core of the conventional crown ceramics, 7 × 10 ^{over 6} to 13 × 10
It was about ^-6 / ° C. However, recently, for example, a diopside crystallized glass having a thermal expansion coefficient of about 6 × 10 ⁻⁶ / ° C. has appeared, and a shell corresponding to such a low expansion core has been developed. Not.

Further, in the case of the above-mentioned diopside crystallized glass, the glass transition temperature is about 730 to 750 ° C.,
In order to prevent deformation of the core during formation, the shell sintering temperature must be lower than this temperature range.

Generally, in glass, since the network structure of silicon dioxide or the like governs various physical properties, the stronger the network structure, the lower the thermal expansion coefficient. However, on the other hand, the fluidity at high temperatures increases, and the firing temperature also increases at the same time. That is, obtaining a glass having both a low expansion and a low firing temperature means overcoming the trade-off with the characteristics of the glass.

In addition to the above conditions, crown ceramics are required to have long-term durability. However, when a shell fired at a low temperature is used, ions have been eluted from the surface due to long-term immersion in the oral environment, causing a subtle change in color tone and a decrease in transparency.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a glass having a low firing temperature, low expansion and excellent chemical durability.

[0009]

Means for Solving the Problems The present inventors have intensively studied to overcome the above technical problems. As a result, it has been found that by using a borosilicate glass having a specific composition, a glass having a low firing temperature, low expansion, and excellent chemical durability can be obtained, and the present invention has been completed.

That is, the present invention relates to a glass containing silicon oxide, aluminum oxide, boron oxide, lithium oxide and sodium oxide as main components, and these components are represented by SiO ₂ , Al ₂ O ₃ and B ₂ , respectively. O ₃ , Li ₂ O, Na ₂
When converted to O and the content is indicated by weight percentage, S
iO _2: 61 to 75 wt%, Al ₂ O _3: 3~20 wt%, B ₂ O _3: 9~25 _{wt%, LiO 2 + NaO 2:} 5~
A glass satisfying 15% by weight, and another invention is a dental porcelain made of the above glass.

The content of silicon dioxide (SiO ₂ ) in the composition glass of the present invention is 61 to 75% by weight, preferably 61 to 70% by weight. If the content of SiO ₂ exceeds 75% by weight, the melting temperature for preparing the glass becomes too high, and even if the glass can be prepared at a high temperature, the firing temperature of the glass becomes high. On the other hand, if it is less than 61% by weight, the chemical durability decreases.

The content of aluminum oxide (Al ₂ O ₃ ) in the glass composition is 3 to 20% by weight.
Preferably it is 5 to 15% by weight. If the content of Al ₂ O ₃ exceeds 20% by weight, the high temperature viscosity of the glass increases, so that the firing temperature increases. If the content is less than 3% by weight, the chemical durability decreases.

The content of boron oxide (B ₂ O ₃ ) in the glass composition is 9 to 25% by weight, more preferably 12 to 20% by weight. B ₂ O ₃ content of 25
If the content is more than 10% by weight, the chemical durability decreases. On the other hand, if it is less than 9% by weight, the melting temperature for preparing the glass increases,
Even if the glass can be prepared at a high temperature, the degree of firing becomes high.

Further, the content of lithium oxide (Li ₂ O) and sodium oxide (Na ₂ O) (Li ₂ O + Na ₂ O) in the composition glass is 5 to 15% by weight, preferably 5 to 12% by weight. %. If the content of Li ₂ O + Na ₂ O exceeds 15% by weight, the thermal expansion coefficient increases and the chemical durability decreases. If the content is less than 5% by weight, the melting temperature for preparing glass becomes too high, and Even if the glass can be prepared by the above, the firing temperature becomes high.
In particular, regarding the content of lithium oxide, 3% by weight is required to keep the coefficient of thermal expansion low, for example, 750 ° C. or less.
It is preferable that it is above. It is not preferable to add an oxide of potassium which is a homologous element in order to increase the coefficient of thermal expansion.

The glass of the present invention contains at least one divalent metal oxide selected from the group consisting of calcium oxide, magnesium oxide and zinc oxide in addition to the above components, thereby lowering the firing temperature and reducing the temperature of the fired body. Air bubbles in the inside can be reduced. The compounding amount of the divalent metal oxide is preferably 20% by weight or less based on 100% by weight of all components constituting the glass. If the amount exceeds 20% by weight, the coefficient of thermal expansion may increase and the chemical durability may decrease.

Further, various kinds of metal oxides can be added to the above-mentioned glass in addition to the above-mentioned essential components as long as the effects of the present invention are not adversely affected. Examples of these metal oxides include transition metal oxides such as strontium oxide, barium oxide, phosphorus oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, and lanthanum oxide. Lanthanoid oxide, tin oxide, titanium oxide, zirconium oxide, yttrium oxide, tantalum oxide and the like.

By adding titanium oxide among the above metal oxides, the borosilicate glass of the present invention can be easily provided with opal properties. The opal property means a unique visible light scattering state characteristic of opal. More specifically, there are particles having a size similar to the wavelength of light in the substance, and the particles scatter in the short wavelength region of visible light, so that the transmitted light of the object takes on a yellow tint and is scattered. This is a phenomenon in which light becomes bluish. Human tooth enamel has opal properties because it is composed of hydroxyapatite microcrystals called enamel trabeculae. The preferable addition amount of the above titanium oxide is 0.1 to 5% by weight, more preferably 1.0 to 3.0% by weight, based on 100% by weight of all components constituting the glass.

The preferred composition range of the borosilicate glass of the present invention is as follows: SiO ₂ : 61 to 75% by weight, Al ₂ O ₃ :
5 to 15 wt%, B ₂ O _3: 12~20 wt%, Li ₂ O
And Na ₂ O: 5 to 12% by weight, Li ₂ O: 3% by weight or more, and TiO ₂ : 1 to 5% by weight.

A typical method for producing the glass of the present invention will be specifically described below. First, a glass material as a supply source of each of the above essential components is mixed using a V-type mixer, a ball mill, etc., and then the crucible is filled with these mixed materials, and heated and melted at 1400 to 1500 ° C. using an electric furnace. I do. Next, the glass in the molten state is gradually cooled in air or quenched in water to obtain glass.

The raw materials used for the glass of the present invention are not particularly limited. Hereinafter, a glass raw material serving as a supply source of each essential component will be specifically exemplified.

As a raw material of silicon dioxide, silica sand (SiO ₂ ) is generally used.

As raw materials of aluminum oxide, alumina (Al ₂ O ₃ ), aluminum hydroxide (Al (OH) ₃ ), soda feldspar
(Na ₂ OAl ₂ O ₃ 6SiO ₂ ), anorthite (CaOAl ₂ O ₃ 2SiO ₂ ), kaolin
(Al ₂ O ₃ 2SiO ₂ 2H ₂ O), petalite (Li ₂ OAl ₂ O ₃ 8SiO ₂ ), spodumene (Li ₂ OAl ₂ O ₃ 4SiO ₂ ) and the like.

As a raw material of boron oxide, boric anhydride (B
₂ O ₃ ) and anhydrous borax (Na ₂ B ₄ O ₇ ).

As a raw material of sodium oxide, soda ash (N
a ₂ CO ₃ ), sodium hydroxide (NaOH), sodium sulfate (Na ₂ C
O ₃ ) and sodium nitrate (Na ₂ NO ₃ ) can be used.

The raw material for lithium oxide is lithium carbonate
(Li2 CO3), lithium hydroxide (LiOH), lithium sulfate (Li ₂ C
O ₃ ) and lithium nitrate (Li ₂ NO ₃ ) can be used.

As a raw material of calcium oxide, calcium carbonate, calcium hydroxide, calcium sulfate, calcium nitrate and the like can be used.

As raw materials of magnesium oxide, magnesium carbonate, magnesium hydroxide, magnesium sulfate,
Magnesium nitrate or the like can be used.

As a raw material of zinc oxide, zinc oxide is mainly used.

As a raw material of titanium oxide, rutile type or anatase type titanium oxide is used.

The mixing ratio of these glass raw materials is determined in advance by taking into account the glass composition finally obtained.

The glass of the present invention is suitably used as a dental porcelain, particularly a dental porcelain for a shell. In this case, the glass is usually pulverized and classified, and used as a powder whose particle size is adjusted.

The grinding method for this purpose is not particularly limited, and a known grinding method can be employed. Examples of general crushers include compression crushers such as jaw crushers and cone crushers, ball mills such as vibrating ball mills and planetary mills, and media stirring such as tower type crushers, stirred tank type crushers, and annular type crushers. Examples include a high-speed rotary impact crusher such as a mold crusher, a pin mill, and a disk mill, and a roll mill, a jet crusher, and an autogenous crusher. The classification method is not particularly limited, and a known classification method can be adopted. Examples of general classifiers include vibrating sieves, sieve classifiers such as shifters, centrifugal classifiers such as cyclones,
A wet classifier such as a sedimentation classifier may be used.

When the glass of the present invention is used as dental porcelain, it is possible to mix various inorganic pigments to impart color and control transparency. Illustrative examples of such pigments include vanadium yellow,
Cobalt blue, chrome pink, iron chrome brown, titanium white and the like.

The firing temperature of the shell porcelain used for the all-ceramic crown is preferably 650 to 750 ° C., and the glass of the present invention can satisfy this.
If the glass transition point is higher than this range, the core may undergo thermal deformation. On the other hand, if the glass transition point is lower than this range, the amount of melting often deteriorates due to the properties of glass, and organic substances attached to the porcelain are taken into the shell without being completely decomposed during the technical operation, and the shell is removed. There is a fear that the color tone of the image may be poor.

After the dental porcelain of the present invention is placed on a ceramic core and fired, an all-ceramic crown composed of a core and a shell is obtained. As described above, since many ceramic cores are susceptible to thermal deformation, the dental porcelain of the present invention is particularly suitable as a porcelain for all ceramics. At this time, the coefficient of thermal expansion of the shell is 4.0 × 10 ^{−6 to} 7.0 × 10 ⁻⁶ / ° C.
Is preferable, and the glass of the present invention can satisfy this. If the coefficient of thermal expansion is out of this range, the difference between the coefficient of thermal expansion and the core ceramic will be too large, causing cracks in the shell, or peeling due to concentration of thermal stress between the core and the shell over time. May cause inconvenience.

The acid dissolution amount of the shell obtained by firing the dental porcelain of the present invention indicates durability in an acidic aqueous solution. Although a specific measuring method will be described later, it is calculated as a weight loss of the pulverized shell in a dilute aqueous nitric acid solution. If this value is 1.0 or more, the durability of the shell may be poor. When the glass of the present invention is used, the acid dissolution amount is 1.0.
Less than.

It should be noted that the physical properties of the shell obtained by firing the dental porcelain, such as the coefficient of thermal expansion and the amount of dissolved acid, can be generally considered to be substantially the same as those of the original glass.

It is also a preferred embodiment to use two or more of the glasses of the present invention in a mixture. In particular, when the glass of the present invention is used as a dental porcelain, by mixing two or more types of glasses having a difference of about 20 ° C. to 100 ° C. in the firing temperature, the bubbles of the fired body are reduced, and the firing is performed. It is possible to improve the strength and transparency of the body.

The method of using the dental porcelain of the present invention is not particularly limited, and a known method can be employed. In general, the procedure is to knead glass powder with water, build up the ceramic on the core, and then fire it. At this time, using a kneading liquid having a refractive index similar to that of the porcelain in place of water is a preferable method in that the kneaded mud becomes translucent and the color tone after firing is easily predicted. In addition, the glass of the present invention is given a color tone and transparency corresponding to each part of the tooth such as dentin, enamel, incised end, and cervical part, and a method of embedding these in multiple layers is also for reproducing a good natural color tone. This is a preferred method.

[0040]

The glass of the present invention is characterized by having a low coefficient of thermal expansion, a low acid dissolution amount, and a low firing temperature of the glass powder. For this reason, the glass of the present invention is suitable as a dental porcelain, especially when used as a shell for an all-ceramic crown, without deformation of the core after firing on the core, without causing the occurrence of cracks, In addition, it is possible to maintain its aesthetics for a long time in an oral environment.

[0041]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. The methods for evaluating the firing temperature, the coefficient of thermal expansion, and the solubility shown in the examples are as follows.

(1) Firing temperature The glass obtained by melting was pulverized with an alumina mortar, classified by a 200-mesh sieve, and the amount passed through the sieve was collected to obtain a porcelain sample. This porcelain sample was kneaded with water, and filled into a mold having a hole having a thickness of 2 mm and a diameter of 10 mm while performing condensation, to produce a molded body. This molded body is made of Porcelain Furnace TDF Sigma 120
After drying in a furnace at 600 ° C. for 5 minutes using (Tokuyama Co., Ltd.), vacuum firing was performed at 10 ° C. intervals near the firing temperature appropriately predicted from the glass composition. The heating rate from 600 ° C. was 50 ° C./min, and the holding time at the firing temperature was 2 minutes.

Observing the fired body, the firing temperature when the whole was completely sintered and became translucent, and the surface was not completely melted and slight irregularities due to the porcelain particles were observed, was set to the firing temperature of the porcelain sample. Sintering temperature.

(2) Coefficient of thermal expansion 3 mm × 3 mm × 10 m from glass obtained by melting
m is cut out as a measurement sample and the thermal analyzer TM
The sample was heated from room temperature to 500 ° C. with A120 (manufactured by Seiko Instruments Inc.), and the coefficient of thermal expansion was measured. (3) Acid dissolution amount The glass obtained by melting was coarsely pulverized in an alumina mortar, and then passed through a mesh sieve, and components not passing through the mesh sieve were collected. Take 3g of this ingredient,
It was immersed in 100 ml of 0.01 N aqueous nitric acid and boiled for 1 hour. After separating the glass from the liquid by filtration, 100 ° C
And then weighed after drying for 15 hours. The acid dissolution amount was calculated by the following equation.

[0045]

(Equation 1)

Example 1 31.75 g of silicon dioxide (special grade reagent, manufactured by Wako Pure Chemical Industries, Ltd.)
Aluminum hydroxide (reagent grade, manufactured by Kanto Chemical Co.) 3.8
2 g, boron oxide (special grade reagent, manufactured by Wako Pure Chemical Industries) 6.00
g, lithium carbonate (special grade reagent, manufactured by Wako Pure Chemical Industries) 5.56
g, sodium carbonate (reagent grade, Wako Pure Chemical Industries) 5.1
3g, zinc oxide (reagent grade, Wako Pure Chemical Industries) 6.00g
After being weighed and mixed in a dry manner, the mixture was melted at 1500 ° C. for 15 minutes, then poured out onto a stainless steel plate and cooled. After crushing the obtained coarse glass in an alumina mortar,
The mixture was re-melted at 00 ° C for 15 minutes, cooled on a stainless steel plate, and cooled to obtain a uniform glass.

The composition of the glass and the measured firing temperature,
Table 1 shows the coefficient of thermal expansion and the amount of acid dissolution.

Examples 2 to 16 Glasses were prepared from the raw material compositions shown in Table 1 in the same manner as in Example 1, and the firing temperature, the coefficient of thermal expansion, and the amount of acid dissolution were measured. Table 1 shows the results.

The glass prepared in Example 12 was replaced with 7
After a heat treatment at 20 ° C. for 10 minutes, this glass showed opal properties.

[0050]

[Table 1]

Example 17 A core of an anterior tooth crown was prepared using diopside crystallized glass, and the powder obtained by grinding the glass obtained in Example 1 in an agate mortar was kneaded with water. Build up, 7
It baked at 40 degreeC. No cracks on the shell surface, peeling of the shell and the core, etc. were observed, indicating good seizure.
When this fired body was returned to the gypsum model to check the compatibility, the compatibility was good, and no deformation due to baking of the porcelain was observed. A similar test was conducted for Examples 2 and 3, but no cracks on the shell surface, no separation between the shell and the core, etc. were observed, and good seizure was shown. The compatibility of the core after firing was also good.

Examples 2, 4, 5, and 6 are glasses made of silicon dioxide, aluminum oxide, barium oxide, lithium oxide, and sodium oxide, all of which show good firing temperature, coefficient of thermal expansion, and amount of acid dissolution. Was. Example 1,
Nos. 3 and 8 are systems to which zinc oxide was added, and all showed good firing temperature, thermal expansion coefficient, and acid dissolution amount. Examples 7 and 9 are systems to which an oxide of an alkaline earth metal is added, and Examples 10 to 16 are systems to which other metal oxides are added. The amount of dissolution was indicated.

Comparative Example 1 Using a commercially available porcelain material (Noritake Super Titan Body, manufactured by Noritake Co., Ltd.), a firing test was performed on the core in the same manner as in Example 17. The porcelain is borosilicate glass powder. The firing temperature was 760 ° C. specified by the manufacturer. Observation of the fired shell revealed that the surface had cracks. In the compatibility test on the gypsum model, slight distortion of the core was observed.

Comparative Examples 2 to 9 Using the raw material compositions shown in Table 2, glass was prepared in the same manner as in Example 1, and the firing temperature, the coefficient of thermal expansion, and the amount of acid dissolution were measured. Table 2 shows the results.

[0055]

[Table 2]

Comparative Example 2 contained no aluminum oxide, Comparative Example 5 had a small amount of silicon dioxide, Comparative Example 7 had a large amount of boron oxide, and Comparative Example 9 had a large amount of alkali metal oxide. Also, the acid dissolution amount was large. In Comparative Example 3, the firing temperature was high because the amount of aluminum oxide was excessive. Comparative Example 4 did not melt at 1500 ° C. because of an excessive amount of silicon dioxide, Comparative Example 6 had a small amount of boron oxide, and Comparative Example 8 had a small amount of alkali metal. In Comparative Example 9, sodium was replaced with potassium in Example 6, but the coefficient of thermal expansion was large.

Claims (3)

[Claims] 1. A glass containing silicon oxide, aluminum oxide, boron oxide, lithium oxide and sodium oxide as main components, each of which is made of Si
Converted to O ₂ , Al ₂ O ₃ , B ₂ O ₃ , Li ₂ O, Na ₂ O,
When viewing the content by weight percent, SiO _2: 61 to 75 wt%, Al ₂ O _3: 3~20 wt%, B ₂ O _3: 9~25 _{wt%, LiO 2 + NaO 2:} 5~15 wt Glass that satisfies%. 2. A dental porcelain made of the glass according to claim 1. 3. An all-ceramic crown in which a shell obtained by firing the dental porcelain according to claim 2 is laminated on a ceramic score.