JPS6163540A - Preparation of crystallized calcium phosphate glass for dental material - Google Patents

Abstract

PURPOSE:To obtain a crystallized calcium phosphate glass for dental material having transparent and beautiful appearance, by melting a calcium phosphate mixture having specific atomic ratio of Ca/P under normal pressure, cooling the molten mixture, and again melting under reduced pressure. CONSTITUTION:A Calcium phosphate mixture having an atomic ratio (Ca/P) of 0.35-1.7 is melted under atmospheric pressure, and cooled to obtain glass. The glass is melted again under reduced pressure of about <=100Torr, returned to the atmospheric pressure, and cast by a lost-wax process. The cast glass is crystallized by beat-treatment. The water, air, carbon dioxide gas, etc. existing in the glass can be removed, and transparent feeling can be attained by the crystallization of the glass. The damage of the crucible and the furnace can be decreased compared with the case of direct melting.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement in a method for producing calcium phosphate-based crystallized glass, which is most suitable as a dental material.

[Conventional technology]

In recent years, the range of applications for ceramics has expanded rapidly, reaching the medical field, and attempts are being made to apply ceramics to medical materials, such as artificial tooth roots, for which metals and plastics have traditionally been used. .

The inventors of the present invention have repeatedly conducted research on a method of manufacturing high-strength ceramic by forming ceramic into any shape with high precision, and have found that this is possible by selecting a calcium phosphate-based material as the material. He has discovered this and is conducting extensive research on it. Calcium phosphate materials with this excellent feature also had poor aesthetics due to their white color, but this problem was solved by adding a specific metal oxide to react with the calcium phosphate component and crystallize it. .

[Problem that the invention seeks to solve]

By adding this coloring component, it is possible to obtain a color tone that is close to that of natural teeth, but since it is not transparent, when it is inserted between natural teeth, it inevitably feels out of place with the surrounding natural teeth. In an attempt to eliminate this strange feeling, if the operation of crystallizing calcium phosphate glass is stopped midway and a portion of the glass remains to create a transparent appearance, the remaining glass will reduce the toughness of the material and make it brittle. It is also possible that the acidic luciram component gradually dissolves during use, which is not preferable. Moreover, it is difficult to control the amount of glass by stopping crystallization midway, and the degree of crystallinity becomes unbalanced, especially in bridges and the like where the thickness varies depending on location.

Therefore, the present inventors performed the process of heating and melting the raw material mixture under reduced pressure (including in a vacuum; the same applies hereinafter) to improve the transparency of the product and overcome the above-mentioned drawbacks of conventional calcium phosphate-based crystallized glass materials. A patent application was filed for a major improvement (Japanese Patent Application No. 1983-61996).

However, it has been found that melting highly reactive raw material mixtures under reduced pressure causes more damage to the melting vessel and melting furnace than when melting under atmospheric pressure, making it unsuitable for industrial production. .

[Means for solving problems]

As a result of various studies on melting conditions, the present inventors first melted the raw material mixture under atmospheric pressure to vitrify it, and then remelted it under reduced pressure, thereby melting the raw material mixture under atmospheric pressure. We found that exactly the same effect can be obtained when

[Effect]

When the raw material composition is melted under atmospheric pressure, the gas components contained in the glass, such as water, air, carbon dioxide, etc., are removed when melted under reduced pressure, resulting in a lack of transparency when the glass is crystallized. It is thought that this phenomenon occurs.

[Structure of the invention]

The starting materials of the present invention are calcium-containing compounds that produce CaO upon calcination, such as calcium oxide, calcium hydroxide, calcium carbonate, and calcium oxalate; phosphoric acid;
Like polyphosphoric acid, it is a phosphorus-containing compound that produces phosphorus oxide when fired. Further, calcium salts of phosphorus MO such as calcium phosphate and apatite can be used alone or in combination with other calcium-containing compounds or phosphorus-containing compounds.

One or more starting materials for a calcium-containing compound and a phosphorus-containing compound are selected, and the calcium-containing compound and phosphorus-containing compound have an atomic ratio Ca/P of 0.35 to 1.
7. When this atomic ratio exceeds 1.7, the melting temperature becomes high and vitrification does not occur. On the other hand, the atomic ratio is 0.35
If the temperature is lower than □, the melting temperature will decrease and vitrification will become easier, but on the contrary, the crystallization process will become slower and excess phosphoric acid will be liberated, making it chemically unstable, which is not preferable.

The calcium phosphate glass of the present invention is basically composed of two components, Ca and P, but a coloring agent component and, if necessary, a coloring auxiliary component are added to achieve the same color and gloss as a living tooth. I can do it. This colorant component interacts with the calcium phosphate component to develop color, and the color tone can be subtly adjusted by changing the type, combination, and amount of the colorant components. When adding colorant components, Zn, Fe, Mn, W, Ce, Ti, Ni, Co.

It is one type or two or more types selected from oxides of Cr and V, and a combination of two or more types is particularly preferable. The amount added is 0.00 parts per 100 parts by weight of calcium phosphate.
01 to 15 parts by weight. If the amount added is 15 parts by weight or more, the melting point of the mixture will rise, and the viscosity of the melt will increase, making casting difficult, while if it is less than 0.01 part by weight, the coloring will be insufficient.

In the method of the present invention, the transparency of the product after crystallization is increased compared to conventional methods, and the addition of a coloring agent makes it possible to achieve a color tone that is more similar to that of natural teeth.

Furthermore, if necessary, rare earth oxides and Al2 can be used as coloring aids.
Color development can also be subtly adjusted by containing 10 parts by weight or less of one or more selected from O3 and Si02. In addition to oxides, ammonium salts, carbonates, acetates,
Compounds that can become oxides during the melting process are used, such as chlorides and nitrates.

The raw materials are weighed, mixed well, placed in a container, and heated and melted at 900'C or higher, preferably 1000 to 1600'C.

Care must be taken when melting at temperatures above 1700'C, as evaporation of the phosphorus component begins.

This melting takes place under atmospheric pressure. After the melting is completed, it is cooled and made into glass. Next, put this glass into the melting container again and
Melt by heating at a temperature of 0'C or more, preferably 1000 to 1600"C. This melting step is carried out under reduced pressure. The degree of vacuum at this time is 100 Torr or less, preferably 40 to
It is 10 Torr. As the degree of reduced pressure increases, the translucency increases and the transparency increases. In addition, when carrying out this vacuum melting operation, it is also possible to enter the vacuum melting process by melting under atmospheric pressure and then reducing the pressure in the molten state without cooling it once.

After melting is completed, casting is performed under reduced pressure or after returning to normal pressure.

Alternatively, the glass is cooled again to form molten glass under reduced pressure, and then melted and cast under atmospheric pressure or reduced pressure. When melting and casting under atmospheric pressure, the effect of reduced pressure melting will be lost if the melting state continues under atmospheric pressure for a long time, so it is preferable to keep the melting time as short as possible.

Casting by the lost wax method is particularly suitable for calcium phosphate materials. The preheating temperature of the casting mold is 800"C or less, preferably 200-800"C.
It is appropriately selected within the range of 'C' depending on the material of the casting mold and the composition of the glass.

Castings made according to the invention are vitreous.

By applying appropriate heat treatment to this glassy material to make it crystallized glass, the properties can be further improved.

The method for crystallizing the calcium phosphate-based crystallized glass according to the present invention is as follows. A molded body formed by a lost wax method or the like is heated in a suitable heating device such as an electric furnace. The heating rate at this time is 50 to 20 0@C/hr,
Heating temperature: 400-9006C, holding time: 100 h
r or less is sufficient.

〔Effect of the invention〕

Since the calcium phosphate-based dental material according to the present invention basically consists of phosphoric acid and calcium, which are the same as the main components that make up natural teeth, it goes without saying that it has essentially excellent compatibility with living organisms, and it is also compatible with metals and plastics. There are no concerns about any harmful effects on living organisms. In the method of the present invention, the raw material mixture is melted under atmospheric pressure, once cooled and vitrified to eliminate reactivity, and then melted under reduced pressure. It improves toughness and aesthetics through the appearance of transparency, and also extends the lifespan of melting vessels and melting furnaces.

〔Example〕

Example 1 To a mixture of calcium carbonate powder and orthophosphoric acid weighed so that the atomic ratio Ca/P of calcium to phosphorus was 0.55, 40% by weight of CeO2 and Ti0240 were added to 100 parts by weight in terms of calcium phosphate. Weight%, N
0.6 parts by weight of mixed powder with a ratio of i020% by weight, A1
After adding 2033 parts by weight and thoroughly kneading, the mixture was melted in a platinum crucible under atmospheric pressure at 1200@C for 1 hour, and then once cooled to form a glass. The obtained glass was placed again in a platinum crucible for 1200
After melting at 1hr under the conditions of °G + 20 Torr, it was returned to atmospheric pressure and immediately cast by the lost wax method. The obtained glass casting was heat treated in an electric furnace at 7106C+ for 2 hours to crystallize it. The color of the calcium phosphate crystallized glass produced in this way is a very transparent ivory color.
Aesthetics were extremely good. Also, the bending strength is 2620
kg/crn2.

The good aesthetics and bending strength were the same as when the raw material composition was directly melted, and the damage to the crucible and furnace was less than when directly melted, demonstrating the superiority of the present invention.

Claims (1)

[Claims] The atomic ratio of calcium to phosphorus Ca/P is 0.35~
1. A method for producing a calcium phosphate crystallized glass dental material, which comprises first melting and vitrifying a calcium phosphate-based raw material blend in the range of 1.7 under normal pressure and then melting it under reduced pressure.