JPS62113728A - Production of dental material - Google Patents

Abstract

PURPOSE:To obtain a dental material having a uniformly semitransparent external appearance and improved aesthetic sense, hardness, etc., and suitable for artificial tooth crowns, etc., by casting a calcium phosphate based glass in a casting mold to give a crystallized glass in the mold and demolding and heat-treating the resultant glass. CONSTITUTION:A calcium phosphate based glass containing >=90wt% calcium phosphate material having composition at 0.35-0.7 atomic ratio (Ca/P) is cast in a casting mold, held at 600-800 deg.C for 5min-50hr and crystallized to give >=5% crystallinity of the cast formed material. The resultant crystallized cast glass material is then demolded, heat-treated at 600-900 deg.C for 5min-50hr and converted into a calcium phosphate based crystallized glass having uniformly semitransparent external appearance and afford the aimed dental material. The resultant dental material has a chemical composition close to that of natural teeth and further high hardness.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing dental materials, and in particular to a dental material made of a calcium phosphate crystallized glass casting having a uniform translucent appearance and excellent aesthetic appearance. Artificial dental crowns,
Applicable to inlays, bridges, etc.

(Prior art) Conventionally, metals, plastics, and porcelain stone have been used as the dental materials mentioned above, but except for porcelain stone, the chemical composition and color are essentially different from natural teeth, and they are not biocompatible. There are also problems in terms of quality and aesthetics.Also, since pottery stone is manufactured by sintering powder such as feldspar, it has poor formability, requires grinding after sintering, and cannot be made into complex shapes. be.

Therefore, calcium phosphate glass or its crystallized material has been proposed as a new dental material to solve these problems (Japanese Patent Publication No. 55-11625, Japanese Patent Application Laid-Open No. 59-141509, 60-289
No. 11, No. 60-131835, etc.). This calcium phosphate glass or crystallized glass has a chemical composition consisting of phosphoric acid and calcium, which are the same components as natural teeth, so it has a good affinity with dental bone texture.
In addition, since its melting point is similar to that of metal materials, it can be cast using the lost wax method and has excellent moldability, making it an excellent dental material.

This calcium phosphate-based glass casting rod dental material contains calcium oxide or a component that produces calcium oxide when fired, such as calcium carbonate, calcium hydroxide, etc., and a component that produces phosphorus oxide when fired, such as,
A mixture of phosphoric acid, polyphosphoric acid, etc. in a specific ratio is 900~
It is manufactured by melting at a temperature of 1600°C and casting in a mold preheated to a temperature of 900°C or less. In addition, in order to crystallize this glass and increase its strength and toughness, the glass casting obtained by the above casting is removed from the mold and
A method of crystallizing by heat treatment at a temperature of 0 ° C, or a method of crystallizing by heat treatment at a temperature of about 600 to 900 ° C while holding the glass cast body in the mold used for casting after completing the above casting. A method is proposed or disclosed.

[Problem that the invention seeks to solve]

Since calcium phosphate glass is transparent as it is, it is desirable to crystallize it to give it a color similar to that of natural teeth and to increase its strength and toughness. However, in the first method described above, the glass casting is removed from the mold without crystallizing it and then subjected to heat treatment to crystallize it, so deformation due to heat treatment is significant and precision casting using the lost wax method is not possible. The important advantage of calcium phosphate-based glasses, that is, is lost. In addition, if the glass casting is simply heated and crystallized while being held in the mold as in the second method above, crystallization tends to be uneven and translucent due to the influence of the interface between the glass and the mold. The more opaque δ than the lucium metaphosphate phase,
- Since the calcium metaphosphate phase tends to precipitate, there are aesthetic problems when using it as a dental material such as artificial tooth crowns, especially in areas that are easily visible from the outside, such as front teeth.

[Means for solving problems]

The present inventors believe that the above problem can be solved by once crystallizing the calcium phosphate glass cast in the mold.
They discovered that the problem could be solved by removing the mold and then applying heat treatment, and completed the present invention. The crystallization in the mold only needs to be at least to the extent that the glass obtained here will not be deformed to the minimum extent during the subsequent heat treatment, and therefore the degree of crystallinity should be at least 5%. As a means of obtaining such a degree of crystallinity, 600 to 800='C5 minutes to 50
A means of heating for a period of time is employed. As the degree of crystallinity increases, a δ-calcium metaphosphate phase, which is unfavorable in appearance, is precipitated, but there is no problem even if this δ phase is formed.

The starting materials and processing operations for producing calcium phosphate glasses are known and reference is made to the publications mentioned above. In particular, the composition of this glass has an atomic ratio of Ca/P of 0.35.
90wt% of calcium phosphate with a composition of ~0.7
It is preferable to include the above. When Ca/P is less than 0.35, it is difficult to uniformly crystallize, and when it exceeds 0.7, it is difficult to obtain a uniform glass. In addition to calcium phosphate, glass contains ^jzOi to control crystallization and improve the water resistance of crystallized glass.

Btax + SIO□ etc. can also be added. As mentioned above, the starting materials for such glasses are selected from calcium oxide, calcium carbonate, calcium hydroxide, calcium hydrogen carbonate, basic calcium carbonate, calcium salts of organic acids, etc., which are calcined to produce calcium oxide. Calcium-containing compounds and orthophosphoric acid, metaphosphoric acid, and pyrophosphoric acid, which are calcined to produce phosphorus oxides.
It consists of a phosphorus-containing compound selected from polyphosphoric acid and ammonium salts of these phosphoric acids. The phosphorus-containing compound may be a calcium salt of the above-mentioned phosphoric acids. Further, the calcium-containing compound and the phosphorus-containing compound may be used alone or in a mixture.

Calcium phosphate glass can be obtained by melting the starting materials at a temperature of 900 to 1600°C. This glass can be used as it is or once cooled and then heated to 980~
It can be melted and cast into molds at temperatures of 1600°C. In addition, the starting materials are melted in a mold to form glass.
It is also possible to cast as is.

The most preferred method for casting dental materials from this calcium phosphate glass is the lost-one-pass method. This casting operation can follow conventional techniques for metals. A piece of wax in the shape of a tooth crown or the like to be created is embedded in a mold ring using an investment material. When this is heated and the wax is melted and flowed out, a mold surface is formed where the wax has disappeared.

For example, phosphate-based or ethyl silicate-based investment materials can be used.

When casting calcium phosphate glass using a mold, for example, the mold is heated to a ring temperature within the range of 300 to 1000° C., and the heated mold is used to cast the glass. Casting is preferably a casting method that applies external force, such as centrifugal casting, compression casting, or vacuum compression casting. If the heating temperature of the mold exceeds 1000°C, the reaction between the casting and the cast glass becomes intense, making it difficult to remove the cast glass from the mold. Further, if the temperature is lower than 300°C, there is a possibility that the molten glass will not flow into the details of the mold.

After casting in the mold is finished in this way, the glass casting body is kept in the mold at a temperature of 600 to 900°C, preferably 630 to 7°C.
The temperature is maintained within the range of 50° C. to allow crystallization. If the holding temperature exceeds 900°C, the precipitated crystals will become coarse and the strength will decrease. If the temperature is lower than 600° C., crystallization will not proceed or will not progress sufficiently, and the cast body may be significantly deformed during subsequent heat treatment outside the mold, which is not preferable.

Crystallization in the mold is carried out until the degree of crystallinity of the glass cast into the mold reaches 5% or more. The degree of crystallinity here can be determined by powder X-ray diffraction. Diffraction angle (2θ) where the glass halo intensity is large and there are no crystal diffraction lines
For example, if 24.15 degrees is selected, the crystallinity Re of the sample can be determined from the diffraction intensity f of the glass at that angle and the diffraction intensity Tc of the sample to be measured. The time for crystallization in this template is, for example, about 1 hour at 680°C.

However, the crystallized glass that is crystallized in such a mold has δ due to the influence of the interface between the mold and the cast glass.
- Opaque crystallized glass enriched in the calcium metaphosphate phase is likely to be formed, and furthermore, the crystallized glass enriched in the opaque δ-calcium metaphosphate phase and the crystallized glass enriched in the translucent β-calcium metaphosphate phase become heterogeneous. It is easily distributed and aesthetically undesirable for use as a dental material such as a dental crown restoration material.

The inventors achieved this by applying appropriate heat treatment to the opaque crystallized glass contained in this δ-calcium metaphosphate phase.
It has been found that it is possible to complete crystallization by converting β-calcium metaphosphate-based crystallized glass into a translucent crystallized glass. In the present invention, it is important that such heat treatment is performed outside the mold.

That is, the crystallized glass casting with a crystallinity of 5% or more obtained by crystallization in a mold is then demolded and heated at 600 to 900°C.
heat treated at a temperature of By this heat treatment, the β-
As the calcium phosphate phase transforms into the β-calcium phosphate phase, crystallization is completed, and the crystallized glass cast body exhibits a uniform translucent appearance. This heat treatment is desirably performed at, for example, 800° C. for about 1 hour. Processing temperature is 9
If the temperature exceeds 00℃, the crystallized glass may be deformed, and if the temperature is lower than 600℃, the β-calcium phosphate phase may deform.
-Transition to a calcium phosphate phase does not occur and crystallization progresses slowly, making it impossible to obtain crystallized glass with a translucent and homogeneous appearance. This heat treatment after demolding may be carried out in a normal air atmosphere, but preferably in a dry gas atmosphere.

The heat treatment can also be carried out in a powder of BN, StO□, or the like.

〔Example〕

The calcium phosphate glass used in the following examples was composed of CaCO3 powder corresponding to 45 mo1% (25 wt%) as CaO and ls+o1% (^1,03).
A 1 (OH) corresponding to 1-t%)! 53+wol% (74wt%) as P2O in the powder mixture
The reaction product obtained by dropping phosphoric acid containing 13PO4 (corresponding to
After preliminarily calcining at 1250° C. for 3 hours to remove moisture, it was melted in a platinum crucible at 1250° C. for 90 minutes, then poured into a stainless steel mold and slowly cooled.

The mold was created using the lost wax method, and α- was used as the investment material.
A phosphate-based investment material consisting of a mixture of quartz, α-cristobalite, magnesia, ammonium dihydrogen phosphate, and boron nitride was used. The wax model has a wall thickness of 115 mm, an inner diameter of the upper base of 7.0 fl, an inner diameter of the lower base of 8.0 fl,
A truncated conical cylinder with a height of 4.8H was created and used in all experiments.

After the wax model was embedded in a stainless steel mold ring using an investment material, the mold was heated in an electric furnace at 700° C. for 30 minutes to remove the wax by incineration.

The above-mentioned calcium phosphate glass was remelted at 1250° C. into the heat-treated mold, and then cast by a centrifugal casting method.

The above cast bodies were heat treated in a mold under the conditions shown in Table 1. The heat-treated samples were demolded by breaking the mold. The properties, crystallization rate, and content of β-calcium metaphosphate in the crystal phase of the obtained crystallized glass sample were as shown in Table 1.

The thus obtained crystallized glass samples were heat-treated in dry air under the conditions shown in Table 1. The properties, crystallization rate, β-calcium metaphosphate content in the crystal phase, and deformation of the sample of the obtained crystallized glass sample were as shown in Table 1.

11 A glass casting was obtained in the same manner as in the example, and then demolded without crystallization. When the glass castings were heat-treated and crystallized as shown in Table 1, crystallized glass as shown in Table 1 was obtained which was so deformed that it could no longer retain its original shape.

A glass cast body obtained in the same manner as in the Kitakasa 1 Worker Example was crystallized in a mold under the conditions shown in Table 1, and the properties of the obtained sample were not heat-treated after demolding.Table 1 shows the properties of the obtained sample. It was white, opaque, and had a non-uniform appearance.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a calcium phosphate cast body that is precision cast using the lost wax method, has a chemical composition close to that of natural teeth, and has high hardness, is excellent as a dental material. A uniform translucent beauty can be provided.

Claims (1)

[Claims] 1. After casting calcium phosphate glass in a mold and turning it into crystallized glass in the mold, the crystallized glass casting is removed from the mold and heat-treated to give it a uniform translucent appearance. 1. A method for producing a dental material, comprising converting it into a calcium phosphate-based crystallized glass having the following properties. 2. Calcium phosphate glass is made of calcium phosphate with a Ca/P atomic ratio of 0.35 to 0.7.
The manufacturing method according to claim 1, wherein the glass contains 90 wt% or more. 3. Crystallization in the mold occurs at a temperature of 600-800°C.
The manufacturing method according to claim 1, which is carried out for min to 50 hr. 4. The manufacturing method according to claim 1, wherein the crystallization in the mold is carried out until the crystallinity of the cast body reaches 5% or more. 5. Heat treatment after demolding is performed at a temperature of 600 to 900°C.
The manufacturing method according to claim 1, which is carried out for min to 50 hr.