JPS63252942A - Phosphate based crystalline glass for dental material - Google Patents

Abstract

PURPOSE:To enable to stably provide product having mechanical strength, endurance and transparency, by controlling a concentration of water in a glass to a specific range. CONSTITUTION:When transmittance of infrared radiation having 2.5mu wavelength (4,000cm<-1>) and 3.45mu wavelength (2,900cm<-1>) to a glass plate having (t)mm thickness are A% and B%, respectively, the titled glass being 0.5-4mm<-1> in absorbance originated in OH group expressed by the formula is provided. Although it is difficult to express water concentration in a glass as direct value, the water concentration can be determined by measuring transmittance at 3.45mu wavelength based on transmittance at 2.5mu wavelength. When betaOH is less than the lower limit, viscosity of glass in crystallization is high and it is difficult to relax inner stress caused by volume shrinkage by crystallization with viscosity fluid of glass phase and the strength is remarkably reduced. When betaOH is less than the upper limit, water discharged from a crystal part in crystallization becomes excess and the water is concentrated in residual glass phase and partially evaporated to form foam and glass is devitrified and reduced also in strength and endurance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a phosphate-based crystalline glass for dental materials.

[Prior Art] Conventionally, the application of crystallized glass obtained by crystallizing phosphate glass to dental materials, artificial bones, etc. has been studied.

Phosphate glass is obtained, for example, by calcining raw materials prepared to have a predetermined composition and then melting them in a platinum crucible. A crystallized glass material is obtained by molding this glass by a vI manufacturing method or the like and then crystallizing it by heat treatment.

1 Problem to be solved by the invention 1 However, although the raw materials are prepared so that the chemical composition is the same, the glass crystallization is uneven depending on the melting batch, and as a result, the crystallization of crystallized glass is uneven. Appearance 5 Mechanical strength, conversion'? Properties such as physical durability vary widely, making it difficult to obtain materials with appropriate physical properties.

[Means for Solving the Problem 1] The present inventor searched for the cause of non-uniform crystallization in this type of glass, and found that phosphate glass has a tendency to be exposed to fine water compared to silicate glass. contains water, and the concentration of this water changes greatly with slight differences in manufacturing conditions.
It was confirmed that the cause was a change in the viscosity characteristics of the glass, which caused large fluctuations in the crystallization temperature and crystallization rate.

By controlling the concentration of water (011 group) in glass within a specific range, mechanical strength, chemical durability, and a transparent appearance, which is especially required when used as a dental material, can be stabilized. I found out that it can be obtained by

Although it is difficult to express the concentration of water (leaf groups) directly as a numerical value, it can be determined indirectly from the magnitude of absorption caused by 011 groups that appear around the wavelength of 3.45 μm in the infrared transmission spectrum of glass. ;11. For example, water [
11 can be determined.

Thus, the present invention provides phosphate-based crystalline glass for dental materials with a wavelength of 2.5 μm for a mm-thick glass plate.
(4000cm-1) infrared light transmittance is A%, wavelength 3
．． When the transmittance of infrared light at 45 μm (2900 cm-1) is set as B%, βot+= -In (B/A) 8...... Due to the old 1 group expressed by the formula (ri) The absorbance is 0.5-4
An object of the present invention is to provide a phosphate-based crystalline glass for dental materials, which has a diameter of 1 mm-'.

In the present invention, the term "crystalline glass" refers to both a vine glass material in which crystals are precipitated inside by crystallization treatment, and a material after crystallization, that is, crystallized glass.

The phosphate glass of the present invention has an absorbance β due to the OH group. 0. is required to be 0.5 to 4 mm-'. β. 1. When is less than 0.5rnffi-', the viscosity of the glass during crystallization becomes high, and the internal stress generated in the crystallized glass due to volumetric contraction due to crystallization cannot be alleviated by the viscous flow of the glass phase. It becomes difficult. As a result, cracks occur in the crystallized glass or residual stress occurs, resulting in a significant decrease in mechanical strength.

On the other hand, when βOH exceeds 4 mm'-', excess water is discharged from the crystal part during crystallization, so water is concentrated in the remaining glass phase and some of it evaporates, resulting in the formation of bubbles. As a result, the appearance of crystallized glass becomes opaque, making it unsuitable as a dental material, and its mechanical strength and chemical durability also deteriorate.

As a method for controlling the amount of 011 groups in phosphate glass, there is a method by controlling glass melting temperature and melting time.

In this method, the higher the melting temperature and the longer the melting time, the lower the amount of carbon atoms in the glass. However, in such a method, the 011 group is reduced and the phosphoric acid content is also volatilized, and the concentration of the 011 groups in the glass is reduced to the above β. 4m in □
It is difficult to control the concentration of phosphoric acid in the glass to a desired concentration under conditions where the concentration is below l'.

The present inventor prefers the bubbling method using gas and the remelting method of crystallized glass as methods for controlling the concentration of 011 groups in glass with good reproducibility without reducing the concentration of phosphoric acid in glass. I found out.

As a bubbling method using a gas, for example, a gas that does not react with the glass (for example, Ns, Oa) is added to the molten glass.
, ^r, lie, air and mixtures thereof) to 30
An example of this method is to quickly volatilize the water in the phosphate glass by blowing it into the glass for up to 180 minutes, thereby stabilizing it at the equilibrium concentration of water at that temperature. In addition, as a method for remelting crystallized glass, for example, once solidified glass is heat treated at the crystallization temperature of the glass or at a temperature 200°C above that temperature for 5 to 24 hours to crystallize it as much as possible. An example of this method is to crush the powder and re-melt it to vitrify it.

As the phosphate glass of the present invention, calcium phosphate glass is preferably used. In addition, magnesium phosphate glass, strondium phosphate glass, or a mixture thereof can also be used. In addition, 20 mol% or less of Aln0+, CeJ3.
La11Os or less than 15 mol% l-i x O*
N a 20 may include 0. ^I
iL, Ce5O+1. If the lag exceeds 20 mol%, even if the water content is appropriate, the viscosity of the glass during crystallization will increase, which may cause cracks in the crystallized glass and reduce its strength, which is undesirable. ,
If Nag-20 exceeds 15 mol%, even if the water content is appropriate, the chemical durability of the crystallized glass may decrease, which is not preferable.

[Effects of the Invention] The present invention has the effect of stabilizing the mechanical strength and chemical durability at a high level when the glass is crystallized by keeping the water content in the phosphate glass constant. be. In particular, it has the effect of creating a transparency similar to natural teeth, which is required when used as a dental material. Moreover, since the crystallization temperature and crystallization rate are stabilized, the crystallization time becomes constant, and there is no need to perform an unnecessarily long heat treatment in consideration of variations in crystallization. As a result, there is an effect of substantially shortening the manufacturing time.

[Example] Example! After vitrification, the components outside the waterside are PJs 50 mol%, Ca
048 mol%, ^1□032 mol% of chemicals 113P a, CaCL, AI 1oll+
3 was mixed to make a 200g raw material batch. 50 nl of ion-exchanged water was added to this and thoroughly stirred to prepare a uniform slurry. After calcining this at 400℃ for 5 hours, it was crushed, transferred to a platinum crucible, and placed in an electric furnace at 1300℃.
A uniform glass melt was obtained.

Next, a platinum vibrator was inserted into the melt, and while keeping the temperature at 1300℃, 03 gas was added at a flow rate of 300nl/min.
It blew for a minute. Thereafter, the mixture was allowed to stand for 10 minutes to remove bubbles, and then poured onto an iron plate to obtain glass.

This glass was formed into a plate shape with a thickness of Inm, the surface was optically polished, and the infrared transmission spectrum was measured.

□ was determined, and the glass transition point was determined by differential thermal analysis. Furthermore, glass was placed in a platinum crucible and melted at 1200℃, and the same process as dental metal casting was performed to produce 2mm+φx25n+m.
After casting into a cylindrical shape, it was heated at 700℃ for 20 minutes in the mold.
Time crystallization treatment was performed. Table 1 shows the results of measuring the bending strength and observing the appearance of the obtained crystallized glass.

Example 2 A platinum vibrator was inserted into the glass melt obtained by the same method as in Example 1, and Ni gas was supplied at 30 On+ while keeping the temperature at 1300°C.
42/min flow rate for 120 minutes, then 1
The mixture was allowed to stand for 0 minutes to remove bubbles, and then poured onto an iron plate to obtain glass.

β obtained for this glass in the same manner as in Example 1. 13
, glass transition point, bending strength and appearance of crystallized glass
Shown in the table.

Example 3 A glass melt obtained in the same manner as in Example 1 was poured onto an iron plate, vitrified, and then heat-treated at 750° C. for 20 hours to obtain crystallized glass. Next, this was ground to a particle size of approximately 2 to 3 mm and placed in the platinum crucible again. 30 at 1300℃
The glass was melted for a minute, and then the melt was poured onto an iron plate to obtain glass.

β obtained for this glass in the same manner as in Example 1. Table 1 shows the glass transition point, bending strength and appearance of the crystallized glass.

Comparative Example A glass melt obtained in the same manner as in Example 1 was immediately poured onto an iron plate-L without blowing gas into it to obtain a glass.

β obtained for this glass in the same manner as in Example 1. II
s glass transition point, bending strength and appearance of crystallized glass
Shown in the table.

Seal Table

Claims (1)

[Claims] (1) In phosphate-based crystalline glass for dental materials, the wavelength of 2.5 μm (4000 cm^) of a glass plate with a thickness of t mm
-^1) Infrared light transmittance is A%, wavelength 3.45 μm (
When the transmittance of infrared light at 2900 cm^-^1) is set as B%, the absorbance due to the OH group expressed as β_O_H=-In(B/A)/t is 0.5 to 4 mm^- ^1
Phosphate-based crystalline glass for dental materials.