JP2002256372A - Gold-silver-palladium alloy for laser irradiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a gold-silver-palladium alloy which is hard to be broken, and also has maintenance force and high hardness so as to satisfy a wide demand required, e.g. in a clasp for dental treatment, and which has improved fatigue resistance and discoloration resistance in an operation process in a short time so as to be used for dental materials at the same time. SOLUTION: The gold-silver-palladium alloy to be hardened by YAG(yttrium- aluminum-garnet) laser irradiation contains about 14 to 18% gold, about 18 to 22% palladium, 8 to 42% silver, about 18 to 22% copper and about 2 to 6% zinc. The alloy has two phase structure different in mechanical properties between the surface layer and the deep part, so that the gold-silver-palladium alloy which is hard to be broken, has maintenance force, and is particularly suitable for a clasp in dental use can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a gold-silver palladium alloy, particularly an alloy used for a dental clasp, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, there has been a wide demand for an alloy which is hard to be broken, has a retaining force, and has a high hardness, for example, in dental practice. In dental practice, a local denture is used to perform a prosthesis for a jaw with one tooth missing and one tooth remaining. A clasp is used to maintain and stabilize the local denture in the oral cavity. This clasp includes a wire hook formed by bending a wire and a cast clasp by casting. For the latter cast clasp, gold-silver-palladium alloys (JIS: T6105, gold 12% or more, palladium 20% or more, silver 40% or more) have been used in many cases because of application to health insurance in Japan.

[0003] Since a stress is always applied to the arm portion of the clasp at the time of attaching or detaching a denture or at the time of occlusion, a mechanical property particularly required as an alloy for the clasp is fatigue resistance.
However, conventional gold-silver-palladium alloys have low strain and elastic energy that reach the proportional limit,
The clasp was not excellent, and the clasp made of the above alloy had a disadvantage that it was easily broken.

As a countermeasure to improve the fatigue resistance and the retention of the denture, for example, the temperature is kept at 800.degree. C. for 3 minutes, then cooled in water, and then slowly cooled from 450.degree. It is known to perform a hardening heat treatment on the entire clasp such as cooling in a furnace. But,
The hardening heat treatment is complicated, and requires a long operation time. Therefore, even if the technique is known, it is not practiced in actual dental practice.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to reduce the fatigue resistance of an alloy suitable for a dental clasp, for example, in a short working process. It is intended to improve the properties and the discoloration resistance.

[0006]

SUMMARY OF THE INVENTION To achieve the above objects, the present invention provides gold in the range of about 14% to 18%, palladium in the range of about 18% to 22%, and silver in the range of about 38% to 42%. %, Copper hardened by YAG laser irradiation consisting of a selection in the range of about 18% to 22% and zinc in the range of about 2% to 6%. The invention provides an alloy comprising at least 2% to 6% zinc.
An object of the present invention is to provide a method for producing a gold-silver-palladium alloy cured by irradiation with a YAG laser.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a dental gold-silver-palladium alloy capable of improving the fatigue resistance and discoloration resistance of a clasp upon irradiation with a YAG laser.

The inventor of the present invention has determined that the composition of a dental gold-silver-palladium alloy having the above-mentioned properties, which is hardened by irradiation with a YAG laser, has a range of about 14% to 18% for gold and about 18% to 22% for palladium. % Silver, about 18% to 2%
It has been found that the alloy is comprised of a selection in the range of 2% and zinc in the range of about 2% to 6%. As a feature of this alloy composition, the composition ratio of copper and zinc is higher than that of the conventional dental gold-silver-palladium alloy, but in order to apply it to health insurance as a dental alloy in Japan, In order to conform to JIS, as described above, 72% of the metal composition is constrained, and as a result, the composition of the present invention is similar to the composition of a commercially available gold-silver-palladium alloy. However, when the composition ratio of copper and zinc is high in the present invention, for the first time, a heterogeneous effect such as hardening of the alloy by irradiation with a YAG laser is imparted, resulting in a completely different material.

The additional metals in the dental alloy will be described below. The addition of gold is to improve discoloration resistance and spreadability. Silver is an element having a high noble metal property next to gold and is therefore an important substitute for gold. However, silver has a disadvantage that sulfide blacks easily occur. Palladium has excellent discoloration resistance, but also has a high melting point. Copper is excellent in strength and heat treatment, but reduces discoloration resistance. Zinc is added as a deoxidizer. By blending these metals, JIS
A dental alloy compatible with the above can be produced.

In the present invention, of the composition of the dental gold-silver-palladium alloy, zinc is the composition of the conventional alloy (usually 1% to 2%).
In comparison with, the added amount of zinc and copper is as large as 10% or more. For this role, besides the above purposes,
If a large amount of zinc and copper are added, P
Since the d-Zn phase is formed at a very early stage, and undergoes a stepwise solidification process in which the remaining metal subsequently solidifies,
Utilizing the property that a large strain occurs in composition when solidification of all parts is completed. Therefore, this alloy is hardened by rapid heating and rapid solidification by laser irradiation, and the following two-phase alloy can be produced.

The dental gold-silver-palladium alloy of the present invention has Y
The feature of the dental metal alloy irradiated by the AG laser is that even the above-mentioned dental gold-silver palladium alloy is hardened by rapid heating and rapid solidification such as laser irradiation, so that a surface of 100 μm is obtained.
Only the range of m to 200 μm can be locally cured, and the surface layer and the deep part have a two-phase structure with different mechanical properties, and the time required for surface modification is only a few minutes. It is mentioned. The two-phase structure here is characterized by the fact that only the surface is hard and the deep part is soft, and was successfully achieved for the first time by being able to cure only the localized part of the surface layer by applying the high-density energy of the laser. The clasp of the dental gold-silver-palladium alloy of the present invention having the two-phase structure can be characterized in that it is hard to break and has a large retaining force. As a conventional example, carbon steel hardens when rapidly cooled from a temperature 30 ° C. to 50 ° C. higher than the phase transition point, so that the surface can be easily hardened by laser irradiation. For the purpose of improving the friction resistance, some of them have been put to practical use, for example, by hardening the surface of a piston head of a car engine with a laser.
However, in order to harden dental alloys, it is thought that it will not be hardened by instantaneous heating such as laser irradiation because it utilizes the change in the crystal lattice state, and in the field of dental alloys,
Conventionally, all are single-phase alloys, and no alloy has been hardened by laser surface modification.

One of the objects of the present invention is to improve the fatigue resistance of the clasp (FIG. 1), which can be achieved by adopting a two-phase structure in which only the surface layer is hardened as described above. Fatigue accumulates when attaching and detaching dentures and occlusal, and even a weak force can cause the clasp to break. Here, since the surface layer is hardened, a fracture line in which damage propagates is prevented, so that fatigue resistance can be improved (FIG. 2). Comfortable use of dentures
It is an advantage of the clasp according to the invention (FIG. 1) that the clasp is less likely to break and requires a longer period of use since it requires the patient to be "accustomed". Therefore, the laser-processed gold-silver-palladium alloy of the present invention, which is hardened by a laser, is a very excellent alloy.

[0013]

EXAMPLES A gold / silver / palladium alloy for laser processing in the present invention was prepared by the method described below, and its properties were tested. First, selection and melting of alloy materials are performed. Three kinds of alloys having different concentrations of gold shown in the table were produced. Gold, palladium, silver, copper and zinc having a purity of 99.9% or more were weighed to the nearest 1 mg. The metal of each alloy was inserted into an opaque quartz tube, replaced with high-purity argon gas, and then heated and melted with a city gas oxygen flame to produce an alloy.

[0014]

[Table 1]

Second, the alloy is buried and cast. An acrylic pattern for preparing a test piece to which a ready-casting wax was attached as a sprue was planted on the same former. The former and the pattern were placed in a stainless steel ring, and a gypsum-based investment material (GC, cristobalite investment material) was kneaded at a standard water mixing ratio for about 60 seconds, and immersed in a vacuum.
After the investment material was completely cured, the former was removed from the stainless steel ring and used as a mold. 70 molds
Heating was performed in an electric furnace at 0 ° C., the alloy was melted with a city gas-air flame, and a sample was cast using a vertical centrifugal caster (manufactured by HAYASHHI).

Third, laser irradiation is performed (FIG. 3). Each time the casting was irradiated with a pulsed laser beam at 0.5 second intervals, the casting was moved in a constant direction of 0.5 mm, and this was continuously repeated 81 times to make the surface of the irradiation mark 4 × 4 mm ² . .

The hardness of the alloy sample prepared by the method described above,
The discoloration resistance and liquidus point tests were performed to clarify the properties of the gold-silver-palladium alloy of the present invention. In the hardness test, first, a sample (gold-silver-palladium alloy) was subjected to water-resistant SiC paper (# 1500).
And measured using a micro Vickers hardness tester (manufactured by Akashi) under the conditions of a load of 200 g and a load time of 12 seconds (FIG. 2). The results were shown as isohardness curves of the three types of gold-silver-palladium alloys after laser irradiation (FIG. 4). In FIG. 4a, 14% Au-40Ag-20Pb-22Cu-4Z
The results for n alloy are shown, and the hardness is from 234.3 Hv to 27
It is distributed in the range of 8.8 Hv, and as the pulse width becomes narrower overall, the curability of the irradiation mark increases, and the pulse width becomes 3
When the laser energy in ms is 12 J / P, 27
High curing of 5 Hv or more was shown. Similarly, the test results of the 16% gold-added alloy and the 18% gold-added alloy are shown. 16%
The hardness of the gold-added alloy after irradiation is distributed in the range of 201.1 Hv to 255.4 Hv, the pulse width is 4 ms,
In addition, a high curing value was shown under the condition that the laser energy was 12 J / P (FIG. 4B). The hardness of the 18% gold-added alloy after irradiation was distributed in the range of 190.9 Hv to 224.6 Hv, and showed a high hardening value under the conditions of a pulse width of 4 ms and a laser energy of 12 J / P ( FIG. 4c). FIG. 5 summarizes the results before and after laser irradiation in each of the above alloys. The three laser irradiation groups are the left three graphs, and the irradiation conditions are also shown. Here, as the control group, it is shown that the hardness of the laser irradiation group is increased as compared with the non-laser irradiation of each of the same alloys. In the case of the 14%, 16%, and 18% gold-added alloys, 53.4%, 41.5% and 2
The hardness is increased by 5.9% (FIG. 4d). In the control group, the hardness did not change regardless of the change in the amount of gold added, but in the irradiation group, when the amount of gold added was increased, the rate of increase in the degree of hardening was higher than that in the control group. It slows down (FIG. 4d).

Next, a discoloration resistance test was performed on the gold-silver-palladium alloy. The polished alloy sample was subjected to ultrasonic cleaning in pure water and dried, and then the lightness (L ^* ) was measured using a color / color difference meter (manufactured by Minolta). In order to make the dental gold-silver palladium alloy of the present invention conform to the JIS standard (JIST6106), it is specified that “the brightness after immersion in the JIS standard color chart is less than 7 (Munsell color chart)”. That is, when the L ^* value after immersion is 70 or more, the standard is satisfied. The test results were as control groups without laser irradiation of 14%, 16% and 18% gold-added alloys.
The lightness after immersion in cast was 61.6, respectively.
66.3 and 68.1, while the irradiation group improved to 70.2, 70.1 and 70.1, respectively. Therefore, by performing surface modification with a laser, discoloration resistance was improved, and it was possible to conform to the JIS standard for dental gold-silver palladium alloy. When the three kinds of gold-silver-palladium alloys after the discoloration resistance test were observed with a microscope, the surface modified by laser irradiation (surface alloy) and the other parts (master alloy) were surface modified by laser irradiation. The part becomes visually recognizable to the naked eye that the discoloration resistance has been improved.

The liquidus point of the gold-silver-palladium alloy was measured. 10 g of each alloy sample was placed in a quartz tube, heated and melted with a city gas-air flame, and a K thermocouple was installed at the center of the melted alloy. A thermocouple was connected to the high-sensitivity meter, and the measured temperature was output from the meter as a current. This was read by a recorder, and the temperature change over time during cooling was measured. Based on this data, a cooling curve was drawn to determine the liquidus point of each alloy (FIG. 5). The test results were 14%, 1
6%, 18% gold added alloy after laser irradiation group, asc
Under the conditions in ast, the temperature of the liquidus point was 894.4 ° C., 879.8 ° C., and 838.9 ° C., respectively (FIGS. 5a, b, c), and the liquidus point required to conform to JIS was 1100. The value also satisfies the specification below ° C.

[Brief description of the drawings]

FIG. 1a is a plan view showing how to use a clasp with a local denture.

FIG. 1b is a side view of the same.

FIG. 1c is a front view of the same.

FIG. 2 is a side view showing a state of a cut surface after an alloy bending test of the present invention.

FIG. 3 is an explanatory view showing a laser irradiation method for an alloy to be subjected to a test in the present invention.

FIG. 4a is a graph showing the uniform hardness of an alloy (14% gold-added alloy) after laser irradiation according to the present invention.

FIG. 4b is a graph showing the same hardness of a 16% gold-added alloy.

FIG. 4c is a graph showing the same hardness of the 18% gold-added alloy.

FIG. 5 is a graph showing the hardness of each alloy before and after laser irradiation according to the present invention.

FIG. 6a: Time of alloy of the present invention (14% gold-added alloy)
Graph showing temperature curve

FIG. 6b is a graph showing a time-temperature curve of the same 16% gold-added alloy.

FIG. 6c is a graph showing a time-temperature curve of the same 18% gold-added alloy.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Clasp 2 Teeth 3 Laser-modified surface 4 Mother alloy 5 Liquidus point 6 Irradiated surface

Claims (2)

[Claims] 1. The method according to claim 1, wherein gold is in the range of about 14% to 18%, palladium is in the range of about 18% to 22%, and silver is about 8% to 42%.
%, About 18% to 22% copper, and about 2% zinc.
A gold-silver-palladium alloy characterized by being hardened by irradiation with a YAG laser comprising a selection in the range of 6% to 6%. 2. The method of claim 1, wherein at least zinc is in the range of about 2% to 6%.
Copper in the range of about 18% to 22% and palladium in about 18%.
% To 22% in the range of YA
A method for producing an alloy that is cured by irradiation with a G laser.