JPS6164846A - Corrosion resistant dental ni-cr alloy for cast crown - Google Patents

Abstract

PURPOSE:To obtain a dental alloy having superior mechanical properties such as tensile strength and hardness and superior corrosion resistance by adding very small amounts of Si, B, Zr and other elements to an Ni-Cr alloy as a dental alloy for a cast crown. CONSTITUTION:An Ni-Cr alloy consisting of 18-25% Cr, 0.1-2.5% Si, 0.1-0.5% B, 0.1-1% Zr and the balance Ni or further contg. <=5% Cu and/or <=1.0% Al is used as a dental alloy for a cast crown or a bridge. The dental Ni-Cr alloy has superior mechanical properties and superior corrosion resistance in the mouth without using Be harmful to the human body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a Ni--Cr alloy that has excellent performance in dental casting applications, which is a type of dental prosthesis.

[Prior Art] Various alloys containing Ni and Cr as main components have been known as alloys for use in dental casting or bridge-linked dentures, and these conventional alloys have good mechanical properties. I am satisfied. However, corrosion resistance is still insufficient, and in particular, there has been no available alloy for dental casting that can simultaneously satisfy corrosion resistance and mechanical properties.

In general, alloys for metal casting or cross-linked dentures containing Ni and Cr as main components are required to have a tensile strength of 40 kg/11112 or more, preferably about 60 kg/am2, and the hardness is higher than that of gold teeth. To prevent wear of H
It is said that v220 or less is good, and elongation is required to be 3% or more, preferably about 5 to 7%. Moreover, since dental casting alloys are used in the oral cavity, sufficient safety must be guaranteed.

As a near-use alloy for dental casting with the above-mentioned mechanical properties, Ni-Cr containing a small amount of Be as a modifying element is used.
Ni-Cr alloys or Ni-Cr alloys with reduced Cr content are known. Furthermore, although some research has attempted to improve corrosion resistance by increasing the Cr content, increasing the Cr content makes the alloy too hard, which significantly impairs its suitability as an alloy for near-term casting.

[Problems to be solved by the invention] However, Be is an element that is harmful to the human body, and alloys with low Cr content have insufficient corrosion resistance, and the alloy components are eluted into saliva, which has a negative impact on the human body. affect

In addition, alloys for dental casting are melted and cast into investment materials, but high-melting point alloys are difficult to melt with city gas or oxygen, and they tend to seize into the investment material during casting. It is easy to cause rough skin, so it is desired that the melting point of the alloy be kept below 1330°C.

Also, a method is known in which Be is added for the purpose of lowering the melting point, but this method causes the above-mentioned toxicity problem. On the other hand, in Ni-Cr alloys containing harmless elements such as boron and silicon, attempts to improve corrosion resistance by increasing the Cr content tend to deteriorate the mechanical properties of the alloy, making it easier for cast products to crack. be.

Under these circumstances, the present invention aims to provide a dental casting Ni-Cr alloy that has improved corrosion resistance without containing harmful elements such as Be, and has both excellent mechanical properties and corrosion resistance. .

[Means for solving the problem] The dental casting alloy according to the present invention has a weight percentage of Cr: 1
Contains 8-25% Si: 0.1-2.5% c: O, 1-0.5% B: 0.1-0.5% Zr: 0.1-1%, or further Contains the following Cu and/or Al, Cu: 0 to 5% (however, O is not included) Al: 0 to 1% (however, 0 is not included) The remainder is Ni and inevitable impurities. It is something.

[Function] The reason why the alloy composition is determined as described above in the present invention is as follows.

Cr: 18-25% (weight%: same below) Cr is N
It is an indispensable element to ensure minimum discoloration and corrosion resistance in i-Cr alloys. In addition to these effects, the present invention combines with coexisting C and B to form Cr carbide and Cr boron. This also contributes to improving strength.

In conventional Ni-Cr alloys, it is said that sufficient discoloration and corrosion resistance can be obtained by containing about 15% of Cr, but in the present invention, part of the Cr is Cr.
Since Cr is consumed in the formation of carbides and Cr borides, it must be contained in an amount of 18% or more in order to fully demonstrate its inherent corrosion resistance.However, if the Cr content exceeds 25%, the hardness increases excessively. However, the elongation becomes poor.

Si: 0.1 to 2.5% Si has the function of lowering the melting point of other alloys, acting as a deoxidizing agent, and increasing suitability for near-casting applications. In order to effectively perform its function as a deoxidizing agent, it must be 0.
It must be contained in an amount of 1% or more, but if it exceeds 2.5%, the alloy becomes hard and its suitability for near-casting applications decreases.

B: 0.1 to 0.5% B is a component that exhibits a variety of effects such as lowering the melting point of the alloy, deoxidizing, preventing seizure with investment materials, and improving mechanical properties. In order to effectively exhibit the acid function and the anti-seizure function with investment materials, the content must be 0.1% or more, but if it exceeds 0.5%, the alloy becomes excessively hard and cannot be used as an alloy for cast crowns. Aptitude is hindered.

Ni-Cr alloys containing C: 0.1-0.5%, Zr:O, and 1-1% B generally have low high temperature strength and tend to crack in cast products, but if an appropriate amount of C and Inclusion of Zr significantly improves high temperature strength and eliminates problems such as cracks. In order to effectively exhibit this high-temperature strength improvement effect, it is necessary to contain 0.1% or more of C and 0.1% or more of Zr, but C
If it exceeds 0.5%, the amount of carbide precipitation increases, making the alloy hard and brittle, resulting in poor elongation. Moreover, if Zri exceeds 1%, seizure with the investment material is likely to occur and the casting surface will deteriorate significantly.

Cu20-5% Cu is not an essential component, but it lowers the melting point of the alloy to improve castability, and acts as a deoxidizer to improve the physical properties of the alloy. However, if the Cu content exceeds 5%, the color fastness of the cast product will deteriorate, so it must be kept below 5%.

Although Al5o~5% At is also not essential, it has the effect of improving the elongation of the alloy as well as the castability, and can further improve the quality of the alloy as a near-use dental casting alloy. But At
If the amount is too large, it tends to cause seizure with the investment material and also tends to reduce the gloss of the cast body after polishing, so it must be kept at 1% or less.

Note that C and Zr are Fe-B and high carbon Fe-
It is also possible to use it as an iron alloy such as Cr, and in this case iron will be mixed into the alloy, but if the iron content is 5% or less, the above characteristics of the invention alloy will not be inhibited at all. Not done.

The remaining components of the alloy of the present invention other than the above elements are substantially N.
i, with trace amounts of Co, Mn, and Hf as inevitable impurities.
etc., but if these amounts are about 2% or less, they have almost no effect on the performance of the alloy.

[Example] As shown in Table 1, a large number of Ni-
Cr alloys were prepared and casting experiments were conducted using phosphate investment materials as the investment material, and the physical properties and corrosion resistance of the cast products were compared. In addition, the corrosion resistance of each alloy was measured using a 1% lactic acid aqueous solution (37
Amount of Ni eluted after full immersion for 7 days (±2°C) (g/c
Judgment was made according to 2). The results are summarized in Table 1.
For comparison, experimental results using conventional dental casting alloys are also shown.

(See below for Yu Xiang Hu. As is clear from Table 1, No. 6 (comparative example) is Cr
Corrosion resistance is poor due to insufficient amount, and N017 (comparative example)
Because the amount of Si is too high, the product becomes hard and has poor elongation. Although conventional products have obtained good results in terms of mechanical properties, they have poor corrosion resistance and pose safety problems.

On the other hand, alloys (No. 1 to 1) that meet the specified requirements of the present invention
It can be seen that the material 5) exhibits good mechanical properties on average and excellent corrosion resistance, and is also extremely safe as a dental material. In addition, in the example alloys,
Castability was also good, no reaction occurred with the investment material, and a sound cast product without cracks etc. could be obtained.

[Effects of the Invention] The present invention is configured as described above, but the point is that both mechanical properties and corrosion resistance can be improved without containing any toxic elements such as Be, and the present invention can be applied to the oral cavity. We were able to dramatically improve the quality, especially the safety, of the alloy for dental cast crowns. Furthermore, this alloy has many features such as good castability, no seizure with investment materials, and a beautiful surface with no cracks or the like.

Claims (4)

[Claims] (1) Weight percentage: Cr: 18-25% Si: 0.1-2.5% C: 0.1-0.5% B: 0.1-0.5% Zr: 0.1-1% A corrosion-resistant Ni-Cr alloy for use in dental casting crowns, characterized in that the remainder is Ni and unavoidable impurities. (2) Weight percentage: Cr: 18-25% Si: 0.1-2.5% C: 0.1-0.5% B: 0.1-0.5% Zr: 0.1-1% A corrosion-resistant Ni-Cr alloy for dental casting crowns, characterized in that it contains Cu: 0 to 5% (however, 0 is not included), and the remainder consists of Ni and unavoidable impurities. (3) Weight percentage: Cr: 18-25% Si: 0.1-2.5% C: 0.1-0.5% B: 0.1-0.5% Zr: 0.1-1% A corrosion-resistant Ni-Cr alloy for use in dental casting crowns, characterized in that it contains Al: 0 to 1% (but not including 0), and the remainder consists of Ni and unavoidable impurities. (4) Weight percentage: Cr: 18-25% Si: 0.1-2.5% C: 0.1-0.5% B: 0.1-0.5% Zr: 0.1-1% A corrosion-resistant Ni-Cr for dental cast crowns, characterized by containing Cu: 0 to 5% (but not including 0), Al: 0 to 1% (but not including 0), and the remainder being Ni and inevitable impurities. alloy.