JPH0518804B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calcium phosphate stain that is most suitable as a coding material for dental glazes or stains (hereinafter simply referred to as stains).

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

However, at the current stage, the application of ceramics in the medical field cannot be said to be sufficient.
The main reason for this is that ceramics have poor moldability and cannot be flexibly adapted to medical materials that often require a variety of shapes. For this reason, for example, in dental materials such as artificial crowns, inlays, and bridges,
It is virtually impossible to handle applications that require precise reproduction of complex and diverse shapes, or even if it is possible, extremely complicated and inefficient work processes are required, resulting in extremely high costs. This will inevitably result in costs.

The inventors of the present invention have conducted repeated research on a method of manufacturing high-strength ceramic by freely and precisely molding ceramic into any shape, and as a result, by selecting calcium phosphate glass as the material,
We have discovered that this is possible and are conducting extensive research on it.

Ceramic materials generally have a three-dimensional structure and therefore have an extremely high melting point, and even in the molten state, the viscosity of the melt is higher than that of metals used in dental materials. cannot be applied to The use of vitreous ceramics has been considered in order to lower the melting point and viscosity of the melt, but the high shrinkage rate during cooling results in poor shape reproducibility and the resulting cast body lacks mechanical strength.

On the other hand, calcium phosphate glass has a relatively low melting temperature because it has a one-dimensional short-chain chain structure, and even if it slightly exceeds the melting temperature, the viscosity of the melt decreases significantly, so it can be used as a metal material. It can be cast into any shape using the lost wax method, which applies an external force in the same way. Furthermore, by adding an appropriate coloring agent to this calcium phosphate glass,
We have also discovered that it is possible to manufacture products with a color tone that is very close to that of natural teeth.

In the case of porcelain, which is one of the ceramic-based dental materials, the surface of the base porcelain is coated with a thin transparent or appropriately colored ceramic layer to fill in the unevenness of the porcelain surface and improve aesthetics. Efforts are being made to improve gender.

With calcium phosphate materials, it is possible to manufacture a sufficiently smooth artificial tooth crown with excellent aesthetics only by casting. However, in order to make the finely processed surface even smoother to match the surrounding natural teeth or to further improve aesthetics, surface coatings can be considered for calcium phosphate materials as well.

However, existing stain materials were developed for porcelain materials, which are feldspathic ceramics, so even if they were applied directly to calcium phosphate dental materials, they would have poor adhesion to the base material and a difference in thermal expansion. Therefore, the coating layer was easily cracked and peeled off, making it impractical. Due to its nature, stains are applied to a base material and then melted and baked, so the melting point of the stain for calcium phosphate materials must be lower than the melting point of the base material, calcium phosphate.

As a result of various studies regarding the above points, the present inventors have completed a low melting point calcium phosphate glass as a stain for calcium phosphate materials.

The low melting point calcium phosphate glass of the present invention is
Since the material itself is calcium phosphate, it has extremely good compatibility and adhesion with the base material, making it ideal for such purposes.

In order to further lower the melting point of the calcium phosphate glass, it is effective to lower the phosphorus to calcium ratio (Ca/P) of the calcium phosphate glass. However, while reducing the Ca/P ratio directly lowers the melting point of calcium phosphate, increasing the phosphoric acid component produces free phosphoric acid in the calcium phosphate glass, which significantly reduces the chemical stability of the glass. . That is, they have the drawback of absorbing atmospheric moisture and disintegrating, or dissolving in acidic or alkaline aqueous solutions.

The low melting point calcium phosphate of the present invention can achieve a significant reduction in melting point and crystallization temperature by adding lithium oxide to the calcium phosphate glass, and the lithium oxide-added calcium phosphate glass has improved physical properties and chemical stability. It was found that there were no problems in terms of surfaces.

For example, calcium phosphate glass (Ca/P=
When 3% by weight (external) of lithium oxide is added to 0.55), a temperature decrease of 125°C in the melting point and 185°C in the crystallization temperature is observed, but its physical properties and chemical stability hardly decrease.

The method for producing and using the low melting point calcium phosphate glass of the present invention will be explained in detail below.

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, and phosphoric acid, polyphosphoric acid, etc., which also produce phosphorus oxides upon calcination. It is a phosphorus-containing compound. Further, calcium salts of phosphoric acids such as calcium phosphate and apatite can be used alone or in combination with other calcium-containing compounds or phosphorus-containing compounds.

Selecting one or more starting materials for calcium-containing compounds and phosphorus-containing compounds,
Calcium-containing compounds and phosphorus-containing compounds are expressed as the atomic ratio of calcium to phosphorus, Ca/P.
Set to 0.35-1.7. When this atomic ratio exceeds 1.7, the melting temperature becomes high and vitrification does not occur. On the other hand, if the atomic ratio is less than 0.35, the melting temperature decreases and vitrification becomes easier, but on the other hand, crystallization becomes difficult and excess phosphoric acid is liberated, resulting in chemical instability, which is not preferable.

Next, the additive for lowering the melting point, which is a feature of the present invention, is lithium oxide, and the amount thereof is 100 parts by weight as calcium phosphate in terms of Li ₂ O.
The amount is 0.1 to 30 parts by weight. As for the form of the compound to be added, compounds that become oxides during melting can be used, such as hydroxides, carbonates, chlorides, nitrates, and organic acid salts.
If the amount of lithium oxide added is less than 0.1 part by weight, the melting point will hardly decrease and the addition effect will not be exhibited. As the amount added increases, the melting point gradually decreases, but when the amount exceeds 20 parts by weight, the melting point does not decrease even though it is added, and at the same time, it gradually begins to become chemically unstable; , the melting point hardly decreases anymore and the glass becomes very chemically unstable.

The calcium phosphate glass of the present invention is basically composed of three components: Ca, P, and Li.When used as a glaze, this composition is used, and when used as a stain, it is colored to have exactly the same color as that of a living tooth. Add the agent component and, if necessary, the coloring aid component. This colorant component acts with the calcium phosphate component to develop a color, and the color tone can be finely adjusted by changing the type, combination, and amount of the colorant components. Colorant components are Zn, Fe, Mn,
It is one or more selected from the oxides of W, Ce, Ti, Ni, Co, Cr, and V, and a combination of two or more is particularly preferred. The amount added is 0.01 to 15 parts by weight per 100 parts by weight of calcium phosphate. 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. Furthermore, if necessary, Al ₂ O ₃ and/or as a coloring aid are added.
Color development can also be subtly adjusted by containing 10 parts by weight or less of SiO ₂ . In addition to oxides, compounds that can become oxides during the melting process, such as ammonium salts, carbonates, acetates, chlorides, and nitrates, are used when adding the above-mentioned coloring agents and coloring aids to the raw materials.

Mix the raw materials well, put it in a container, and heat it to over 800℃.
Preferably, it is heated and melted at 900 to 1600°C. Platinum is the most preferable melting container, but it is expensive, so crucibles made of alumina or zirconia can also be used, although the inner surface may be slightly corroded depending on the temperature. Care must be taken when melting at temperatures above 1700°C, as the phosphorus component begins to evaporate. Heating is continued until the bubbles in this melt are sufficiently removed, and then the melt is cooled and vitrified. The cooling method is not particularly limited.

The calcium phosphate glass thus produced is pulverized into a stain material. To use as a stain, this powder is dispersed in a suitable solvent, applied thinly onto a calcium phosphate base material, and then heated at a temperature lower than the softening point of the calcium phosphate base material and higher than the melting point of the stain material to melt it. Burn.

This coating layer is glassy. Even in this glassy state, it has relatively high abrasion resistance and can be put to practical use as it is. but,
The characteristics can be further improved by heat-treating this glassy material at a temperature below the melting point of the coating layer in a suitable heating device such as an electric furnace to form a crystallized glassy material.

As described above, the present invention is to produce a stain material by adding lithium oxide to calcium phosphate glass to lower its melting point, and will be described below with reference to Examples.

Example 1 The atomic ratio of calcium to phosphorus Ca/P is 0.55
Add a mixture of calcium carbonate powder and orthophosphoric acid weighed so that
3.0 in terms of lithium oxide per 100 parts by weight
Lithium carbonate in an amount corresponding to parts by weight was added and kneaded well, pre-calcined at 300°C for 2 hours to remove moisture, and then melted at 1300°C in a platinum crucible. After completely melting, it was poured onto a graphite plate and rapidly cooled to vitrify it.

This glass was finely ground, kneaded with a small amount of water, and applied to the surface of a calcium phosphate cast tooth crown (Ca/P = 0.55). After drying at 300°C, the coating was completed by heating at 770°C for 0.5 hours. .

After completion, the surface was extremely smooth, and the hardness of the surface was almost the same as that of the base material, calcium phosphate.

Example 2 In addition to the formulation of Example 1, based on 100 parts by weight of calcium phosphate, 40% by weight of CeO ₂ , 40% by weight of TiO ₂ ,
0.6 parts by weight of mixed powder with a proportion of 20% by weight of NiO;
The artificial tooth crown was coated in the same manner as in Example 1, except that 0.3 parts by weight of SiO ₂ was added, and then the whole was heated in an electric furnace at 780°C for 0.5 hours to crystallize the coating layer. did.

The obtained tooth crown had a very smooth surface, a pale yellowish brown color that was very close to that of a natural tooth, and excellent shape reproducibility.

Claims (1)

[Claims] 1. The atomic ratio of calcium to phosphorus, Ca/P, is
A calcium phosphate stain characterized in that 0.1 to 30 parts by weight of lithium oxide is added to 100 parts by weight of calcium phosphate in the range of 0.35 to 1.7. 2 The atomic ratio of calcium to phosphorus, Ca/P, is
0.1 to 30 parts by weight of lithium oxide to 100 parts by weight of calcium phosphate in the range of 0.35 to 1.7, Zn, Fe, Mn, W, Ce, Ti, Ni, Co, Cr, as coloring components.
One or more selected from the oxides of V
0.01-15 parts by weight, as a coloring aid if necessary
A calcium phosphate stain characterized by adding 10 parts by weight or less of Al ₂ O ₃ and/or SiO ₂ .