WO1998003688A1

WO1998003688A1 - Matrix alloy for making dental alloys for dental crowns and bridges, with a gold addition

Info

Publication number: WO1998003688A1
Application number: PCT/IT1997/000041
Authority: WO
Inventors: Paolo Battaini; Giampaolo Arnaldo Italo Bartoli
Original assignee: Prosor Llc (Limited Liability Company)
Priority date: 1996-07-24
Filing date: 1997-02-28
Publication date: 1998-01-29
Also published as: ITMI961555A1; IT1283498B1; AU2230097A; ITMI961555A0

Abstract

The present invention relates to a matrix alloy for making, by adding gold, dental alloys for dental crowns and bridges, which alloy comprises on a rate by weight base, at least palladium from 0.0 to 16.0 %, copper from 20.0 to 41.0 %, silver from 35.0 to 60 % and iridium from 0.0 to 1.5 %.

Description

MATRIX ALLOY FOR MAKING DENTAL ALLOYS FOR DENTAL CROWNS AND BRIDGES, WITH A GOLD ADDITION Technical Field

The present invention relates to a matrix alloy for making, with the addition of gold, dental alloys for dental crowns and bridges. Background Art

As is known, the alloys which are at present used for making dental crowns and bridges, and which conventionally have therein different contents of gold, have different compositions, depending on the amount of gold contained therein.

By changing the gold amount, the physical-mechanical characteristics of the alloy are greatly changed, and, accordingly, an operator must buy and store a lot of different types of alloys, depending on their specific applications.

Thus, a dentist must have available five or six types of different dental alloys, of different gold contents, in order to meet all of the application requirements .

Actually, it is known that for making front prostheses it is necessary to use alloys having good aesthetic properties and accordingly a greater gold contents, whereas the rear prostheses require a comparatively high mechanical strength, with comparatively smaller gold contents and greater palladium, copper and/or silver contents. Disclosure of the Invention

Accordingly, the aim of the present invention is to overcome the above mentioned problem, by providing a new type of matrix alloy, which allows to meet all of the mentioned requirements and, in particular, which can be easily mixed with different amounts of gold, depending on the specific applications, while preserving a very high mechanical strength and a very good aesthetic aspect.

Within the scope of the above mentioned aim, a main object of the present invention is to provide such a matrix alloy which, independently from the gold amount added for making a dental prosthesis, has a melting point and physical-mechanical characteristics substantially analogous to those of the known types of dental alloys.

Yet another object of the present invention is to provide such a dental alloy which is very reliable and safe in operation.

Yet another object of the present invention is to provide such a matrix alloy, for making dental alloys for dental crowns and bridges, by adding a set amount of gold, which can be easily prepared by mixing easily commercially available products and materials.

According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a matrix alloy for making, by adding gold to said matrix alloy, dental alloys for dental crowns and bridges, characterized in that said matrix alloy comprises, in a per weight rate base, the following elements: palladium from 0.0 to 16.0%, copper from 20.0 to 41.0%, silver from 35.0 to 60.0% and iridium from 0.0 to 1.5%. Ways of carrying out the Invention

Further characteristics and advantages of the present invention will become more apparent hereinafter from the following detailed disclosure of a preferred, though not exclusive, embodiment, of a matrix alloy for making, by adding gold to said matrix alloy, dental alloys for dental crowns and bridges.

In particular, the subject matrix alloy is usually used by adding to said matrix alloy gold having a purity of 999.9%, into the alloy making crucible, during the melting process, performed by the so-called lost-wax casting method.

Thus, dental prostheses of a gold alloy are obtained which are suitable to be used as dental crowns and bridges.

The subject matrix alloy can be used for making dental prostheses with a gold contents which can be varied from 30% to 75% by weight.

The made alloys are suitable to meet the requirements of mechanical strength imposed in the dental field.

The matrix alloy according to the present invention, which can be indifferently used with any desired gold amount or rate, is mainly constituted by: palladium from 0.0 to 16.0% by weight, copper from 20.0 to 41.0% by weight, silver from 35.0 to 60.0% by weight and iridium from 0.0 to 1.5% by weight.

To the above mentioned elements it is possible to add the following elements:

Pt 0.0 ÷ 8.0% by weight Au 0.0 ÷ 5.0% by weight Ge 0.0 2.0% by weight Zn 0.0 ÷ 4.0% by weight Fe 0.0 ÷ 1.5% by weight Mn 0.0 ÷ 1.5% by weight Ga 0.0 ÷ 2.5% by weight In 0.0 ÷ 3.5% by weight Sn 0.0 ÷ 3.5% by weight The balance being constituted by Ru, Rh, Re and other impurities For making a dental prosthesis, the matrix alloy and gold are simultaneously introduced into the melting crucible and then are molded according to conventional methods.

The matrix alloy according to the present invention allows to make, by suitably adding a set amount of gold, dental alloys having a chemical composition which is very even through the overall cast piece, i.e. independently from the weight of the cast piece or casting, which usually varies from 10 to 100 grams.

The subject alloy is prepared by using conventionally available dental apparatus, by introducing the matrix alloy and the set gold amount into the crucible, by melting the metals and then by spinning the crucible containing the liquid alloy in order to cast the molten alloy into a refractory material mold, preferably by the lost-wax casting method.

The matrix alloy, in particular, is made by allouing the several elements constituting said matrix alloy according to any suitable method, and without using any mixing procedure during the gold addition step by the operator.

This requires to specifically design the chemical composition of the matrix alloy, by setting the admissible concentration ranges for the several alloy elements and, moreover, the matrix alloy must be made in amounts equal to or greater than 1,000 g per ingots, in order to better amalgamate the alloy components.

From experimental texts it has been found that the optimum rate ranges are the followings:

Pd 10.0 ÷ 12.8% by weight Cu 32.0 ÷ 34.0% by weight Ag 48.5 ÷ 51.0% by weight Pt 0.0 ÷ 0.01% by weight Au 0.0 ÷ 0.01% by weight Ge 0.5 ÷ 1.5% by weight Zn 2.1 2.7% by weight Ir 0.05 ÷ 0.3% by weight Fe 0.0 0.2% by weight Mn 0.0 0.06% by weight Ga 0.0 ÷ 0.1% by weight

In 0.0 0.1% by weight

Sn 0.0 ÷ 0.2% by weight

The balance being constituted by Ru, Rh, Re and other impurities Preferably, palladium is used with rates from 10 to 12.8% by weight, in order to provide the dental alloys to be made starting from the matrix alloy greater resistance to oxidation and corrosion.

Moreover, the palladium rate range will also prevent the oxidation of the matrix alloy, thereby allowing this matrix alloy to be preserved for a long period of time.

The iridium contents can be changed from 0.05% to 0.3% by weight, in order to provide the dental matrix alloy to be made with a proper crystalline grain size, with an iridium amount sufficient to overcome a possible loss of this element due to at least five subsequent re-melting operations of the processing waste material, without adding any new matrix alloy amounts.

The made dental alloys, actually, will provide a refined crystalline grain of an average size of about 40 microns .

The structural characteristics of the subject alloys can be understood from an examination of the microstructural photos shown in figures 1 and 2.

In particular, in figure 1 is shown an alloy made by 75% Au and 25% of the subject matrix alloy.

Figure 2 illustrates the microstructure of an alloy obtaining 50% of Au and 50% of the subject matrix alloy.

The re-melting of the processing waste materials, even with the sole addition of gold, does not cause any increase of the crystalline grain over an average size of 60 microns, even after five subsequent re elting operations.

The melting ranges of the dental alloys which can be made by using the subject matrix alloy, are analogous to those which are typical of the similar commercially available dental alloys; thus, the melting method can be easily carried out, and this either by using a melting flame from an oxygen-propane mixture fed torch or by other melting techniques such as an induction melting process or an electric resistance melting process.

The dental alloys made by using the matrix alloy according to the present invention can be processed in a very efficient and easy manner, with Vickers hardness values which can vary depending on the end gold contents of the alloy, likewise the commercially available products.

All of the made alloys can be subjected to typical thermal annealing and hardening treatments, as conventionally used in alloys for crowns and bridges, in order to change the hardness thereof.

The melting temperature ranges of the matrix alloy and the dental alloy made thereby, have been determined by a differential scanning calorimeter, by performing a temperature scanning with a rise speed of 1.5°C/min, up to a temperature of about 100 °C greater than the temperature of the liquid.

The obtained data is resumed in the following table.

TABLE Au Contents Temperature of the Temperature of the solidus ( °C) liquidus (°C) matrix alloy 1005 1125

30% 805 870

35% 800 865

40% 800 860

45% 805 870

50% 825 890

55% 850 900

60% 865 920

65% 870 930 70% 875 945

75% 905 970

The solidus and liquidus temperatures of the alloys, made from the subject matrix alloy, are related to the gold contents.

All the solidus and liquidus temperatures are suitable for the lost-wax casting method and substantially correspond to the characteristics of the at present commercially available dental alloys.

Hereinbelow are indicated the characteristics related to the elastic limit and to the ultimate elongation rate, depending on the different rates of gold contents. Au contents Elastic Ultimate elongation Type of limit 0.2% % in thi s annealed the dental

(MPa) status al loy

30% 380 18 4

35% 390 19 4

40% 405 23 4

45% 460 18 4

50% 440 21 4

55% 360 22 4

60% 340 30 4

65% 300 38 4

70% 285 37 3

75% 230 43 2

The Vickers hardnesses of the made dental alloys have been measured on samples used for micro-structural analysis, thereby obtaining the data shown in the following table: IABLE

Au contents HV5/30 iafter HV5 /30 after anneal;ing the hardening treatment

30% 185 275

35% 190 280

40% 180 295

45% 195 300

50% 200 305

55% 190 280

60% 180 295

65% 180 275

70% 160 170

75% 150 150

The annealing thermal processing was characterized, for all of the alloys, by a holding time of the alloys at 680 °C of 30 minutes, with a subsequent quick cooling in water.

The hardening thermal treatment has been performed, for all the alloys, after the annealing treatment, and comprised a holding of the alloy at 360 °C for 30 minutes, with a subsequent cooling in air.

The obtained Vickers hardnesses are optimum for the mechanical processing of the main alloys, and, in particular, this is true for the maximum obtained hardnesses.

The hardness values are similar to those of the at present available dental alloys and, in some cases, they are much greater.

From the above disclosure it should be apparent that the matrix alloy according to the invention provides the possibility of greatly reducing the capital expenses for making a lot of different alloys to be stored, since the cost of the matrix alloy does not depend on the cost of the gold material and since the gold can be added as it is necessary.

Moreover, the subject matrix alloy provides the possibility of greatly reducing the processing waste, since the subject matrix alloy can be easily transformed into a new alloy, even of different chemical composition, by adding to the matrix alloy or gold, depending on the requirements.

A further advantage provided by the invention is that it is possible to produce exclusively the alloy amount which is required, without being bound to the standard weights of the alloy packages which are at present commercially available.

The invention as disclosed is susceptible to several modifications and variations, all of which will come within the scope of the invention.

Moreover, all of the details can be replaced by other technically equivalent elements.

In practicing the invention, the used materials, provided that they are compatible to the intended application, can be changed depending on the contingent requirements.

Claims

1. A matrix alloy for making, by adding gold to said matrix alloy, dental alloys for dental crowns and bridges, characterized in that said matrix alloy comprises, on a weight rate base, the following elements: palladium from 0.0 to 16.0%, copper from 20.0 to 41.0%, silver from 35.0 to 60.0% and iridium from 0.0 to 1.5%.

2. A matrix alloy, according to the preceding claim, characterized in that said matrix alloy comprises one or more of the following elements:

Pt 0.0 ÷ 8.0% by weight

Au 0.0 ÷ 5.0% by weight

Ge 0.0 ÷ 2.0% by weight

Zn 0.0 ÷ 4.0% by weight

Ir 0.0 ÷ 0.3% by weight

Fe 0.0 ÷ 1.5% by weight

Mn 0.0 ÷ 1.5% by weight

Ga 0.0 ÷ 2.5% by weight

In 0.0 ÷ 3.5% by weight

Sn 0.0 ÷ 3.5% by weight

The balance being constituted by Ru, Rh, Re and other impurities

3. A matrix alloy, according to Claims 1, 2, characterized in that said matrix alloys comprises preferably the following components in the following ranges:

Pd 10.0 - 12.8% by weight

Cu 32.0 - 34.0% by weight

Ag 48.5 - 51.0% by weight

Pt 0.0 - 0.01% by weight

Au 0.0 - 0.01% by weight Ge 0.5 1.5% by weight

Zn 2.1 2.7% by weight

Ir 0.0 0.3% by weight

Fe 0.0 0.2% by weight

Mn 0.0 0.06% by weight

Ga 0.0 0.1% by weight

In 0.0 0.1% by weight

Sn 0.0 0.2% by weight The balance being constituted by Ru, Rh, Re and other impurities.

4. A matrix alloy, according to one or more of the preceding claims, characterized in that said matrix alloy can be used for making dental alloys by adding to said matrix alloy gold having a purity of 999.9%, in set amounts.