WO2009120752A1

WO2009120752A1 - Zirconia compatible dental alloy composition

Info

Publication number: WO2009120752A1
Application number: PCT/US2009/038197
Authority: WO
Inventors: Paul J. Cascone; Arun Prasad
Original assignee: The Argen Corporation
Priority date: 2008-03-28
Filing date: 2009-03-25
Publication date: 2009-10-01

Abstract

A novel titanium-noble metal dental alloy suitable for use with zirconia compatible porcelains, dental devices formed from such an alloy and a method of forming a dental device using such an alloy are provided. Generally the titanium-noble metal alloy of the invention has a composition comprising up to about 75 wt % titanium and about 25 wt % of at least one noble metal, such that the alloy has a thermal expansion coefficient of from about 9 to 11 x 10^-6 at 25-600 °C.

Description

ZIRCONIA COMPATIBLE DENTAL ALLOY COMPOSITION

FIELD OF THE INVENTION

The current invention is directed to a novel dental alloy that may be used with zirconia compatible porcelains; and particularly to a titanium-noble metal alloy for such use.

BACKGROUND OF THE INVENTION

Many new processes have recently been adopted for use in manufacturing dental prostheses using a stabilized zirconia material. For example, one new rapid prototyping process uses selective laser melting to manufacture dental devices. While there are some questions concerning the economic benefits of producing non-precious crowns and bridges using this technique due to the high capital cost of the equipment, there is little doubt that the technology results in very high productivity. For example, many more restorations can be prepared by one person over traditional labor-intensive fabrication methods. Despite the significant promise of these techniques, the utilization of stabilized zirconia for the fabrication of dental prostheses results in its own complications. In particular, the development of the technology is being impeded because there are relatively few dental alloys that have been developed that are compatible with the types of porcelains zirconia requires. Accordingly, a need exists to develop more desirable alloy compositions that can be used in conjunction with such porcelains to allow for the full benefits of these technologies to be exploited.

SUMMARY OF THE INVENTION

The current invention is directed to a novel dental alloy that may be used with stabilized zirconia compatible porcelains, and more particularly to titanium-noble metal alloys for use with such materials. In one embodiment, the dental alloy of the current invention comprises up to about 75 wt % of titanium and at least 25 wt% of at least one noble metal selected from the group consisting of gold and the platinum group metals. In such an embodiment, the noble metal may be, for example, ruthenium or palladium. In another embodiment, the dental alloy further contains at least one additional alloying material selected from the group consisting of aluminum, nickel, chromium, cobalt, molybdenum, niobium, vanadium, hafnium, zirconium, manganese, tin, iron and rare earth elements.

In still another embodiment, the dental alloy has a thermal expansion coefficient of from about 9 to 1 1 x 10 ⁶ at 25-600⁰C.

In still yet another embodiment, the dental alloy is nitrided.

In still yet another embodiment, the dental alloy may be used with either additive or subtractive manufacturing processes. In one such embodiment, the additive process is a rapid prototyping process such as selective laser melting. In another such embodiment, the subtractive process is a milling process such as CAD/CAM milling.

In still yet another embodiment, the invention is directed to a method of forming a dental device using a manufacturing process, such as a rapid prototyping process or a milling process, that includes providing an alloy comprising about 75 wt% of titanium and at least 25 wt% of at least one noble metal selected from the group consisting of gold and the platinum group metals, and shaping the alloy using the rapid prototyping process into a dental device.

In still yet another embodiment, the invention is directed to a dental device made using an alloy comprising about 75 wt% of titanium and at least 25 wt% of at least one noble metal selected from the group consisting of gold and the platinum group metals that may be used in conjunction with a zirconia compatible porcelain. DETAILED DESCRIPTION OF THE INVENTION

Over the last ten years the use of yttrϊa stabilized zirconia for the fabrication of dental copings has grown geometrically. However, the use of zirconia leads to complications. For example, zirconia requires a special porcelain with a low thermal expansion coefficient since the zirconia has a thermal expansion coefficient of about 10 (x10^"6 at 25-600°C), whereas traditional porcelains are designed to match alloys with expansion coefficients of 14 to 15 (x10^"6 at 25-600⁰C). Accordingly, it would be desirable to have an alloy that would be compatible with the porcelains currently used with zirconia copings. Such an alloy would have a thermal expansion coefficient of around 10 (x10^"6 at 25-600⁰C) and would allow dental labs to stock a single type of porcelain.

In addition to reducing inventory stocking costs, having such an alloy would simplify processing costs for the lab. For example, one of the more demanding aspects of processing such materials is modifying the materials to attain the proper shade of porcelain. Each commercial porcelain system has its own shade. As a consequence, the dental lab technician must make adjustments when working the material to match the proper shade. Were the lab able to use a single standard porcelain system, the entire process for the lab - from training through production and quality control - would be dramatically simplified.

The current invention provides titanium noble metal alloys that are capable of use with such zirconia compatible porcelains. Broadly speaking, the invention is directed to a composition comprising up to about 75 wt% of titanium and about 25 wt% of at least one noble metal alloy, selected from the group of gold and the platinum group elements; the invention is also directed to dental devices made using such a composition. This weight percent can be converted into atomic percent for convenience. For example, a titanium-palladium alloy with a composition of 75 wt% titanium and 25 wt% palladium in accordance with the invention, would have a composition in atomic percentages of about 87 at% titanium and 13 at% palladium. For a titanium-25 wt% ruthenium alloy in accordance with the invention, the composition in atomic percentages would be approximately the same. Noble metal additions while being helpful to adjust thermal properties of titanium, also dramatically improve the electrochemical properties of titanium.

It is appreciated that these are the principal components of the alloys, and that the alloys in accordance with the invention may have additional alloying elements common to titanium and noble alloys (e.g., 0-15% selected from the group of aluminum, nickel, chromium, cobalt, molybdenum, niobium, vanadium, hafnium, zirconium, manganese, tin, iron and rare earth elements etc.] to provide for modified properties.

The titanium-noble alloys of the inventive composition provide materials uniquely suited for a wide variety of dental prosthesis manufacturing techniques, including additive processes, for example, rapid prototyping and subtractive processes, for example, advanced milling. In all these techniques, the alloys in accordance with the invention solve the problem described above in connection with the thermal expansion coefficient of zirconia. First, titanium has a thermal expansion coefficient of about 9.7 (x10^~6 at 25-600°C], below that of zirconia, while the noble metals have thermal expansion coefficients that range from about 9 x 10^"6 (Ru at 25-600⁰C) to about 12 x 10^"6 (Pd at 25-600⁰C). Combining the titanium with the noble metals in the ratio given produces alloys having the desired thermal expansion number of from around 9 to 1 1 (x10^"6 at 25-600⁰C), and more preferably around 10 (x10 ⁶ at 25-600⁰C), making the alloy compatible with zirconia porcelains.

In addition, the noble metal (i.e., palladium, ruthenium, etc.) stabilizes the high temperature form of the titanium. This situation is expected to provide high temperature creep resistance allowing for porcelains to be pressed onto the alloy as well as baked. Moreover, the formation of inter-metallics is expected to harden the alloy and provide sufficient strength for the dental restoration.

Another advantage of this composition is that the minimum level of a noble metal at 25% wt% allows the alloy to be classified as ^"Noble^" under the American Dental Association classification system. This dramatically increases the economic potential for the alloy, since ^"noble^" alloys are the most widely used type of alloy in the United States.

Yet another advantage of the alloys in accordance with the invention is that they may be used in connection with already existing rapid prototyping processes. Most of the commercially available selective laser melting systems allow for the use of titanium alloys or titanium powders. One exemplary system is the MCP Realizer^SM manufactured by Mining and Chemical Products Limited of England that operates on the Titanium SLM alloy, such as that manufactured by Electro Optical Systems GmbH. Thus, the efficiency of the existing rapid prototyping technology can be readily exploited with the alloy compositions of the invention for which there is a built-in market demand.

Finally, an additional advantage to using titanium specifically is that the alloy may be nitrided as described by Knapp in US Patent No. 6,994-,55O, the disclosure of which is incorporated herein by reference, producing a pleasant yellow color on the alloy surface. This eliminates the black color of the titanium oxide, which can sometimes be difficult to cover with porcelains. By making the surface yellow, the porcelain shades appear ^"warmer" and more natural.

Although the above discussion has focused on the dental alloy itself, it should be understood that the invention is also directed to dental devices and methods of forming dental devices using any available technique such as rapid prototyping from the alloy of the current invention. The method in accordance with the current invention would entail the following steps:

• providing an alloy, as described above, comprising about 75 wt% of titanium and at least 25 wt% of at least one noble metal selected from the group consisting of gold and the platinum group metals; and • manufacturing the alloy into a dental device with or without a zirconia compatible porcelain. DOCTRINE OF EQUIVALENTS

Those skilled in the art will appreciate that the foregoing examples and descriptions of various preferred embodiments of the present invention are merely illustrative of the invention as a whole, and that variations in the steps and various components of the present invention may be made within the spirit and scope of the invention. For example, it will be clear to one skilled in the art that typical impurities and/or additives may be included in the compositions discussed above that would not affect the improved properties of the alloys of the current invention nor render the alloys unsuitable for their intended purpose. Accordingly, the present invention is not limited to the specific embodiments described herein but, rather, is defined only by the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A dental alloy for use in conjunction with porcelains compatible with zirconia comprising up to about 75 wt% of titanium and at least 25 wt% of at least one noble metal selected from the group consisting of gold and the platinum group metals.

2. The dental alloy of claim 1 , wherein the noble metal is palladium.

3. The dental alloy of claim 1 , wherein the noble metal is ruthenium.

4. The dental alloy of claim 1 , wherein the alloy further comprises a total of up to 15% of at least one additional alloying material selected from the group consisting of aluminum, nickel, chromium, cobalt, molybdenum, niobium, vanadium, hafnium, zirconium, manganese, tin, iron and rare earth elements.

5. The dental alloy of claim 1 , wherein the alloy has a thermal expansion coefficient of about 9 to 1 1 x 10 ⁶ at 25-600°C.

6. The dental alloy of claim 1 , wherein the alloy has a thermal expansion coefficient of about 1 O x 10^'6 at 25-600°C.

7. The dental alloy of claim 1 , wherein the alloy is nitrided.

8. A dental alloy for use in conjunction with porcelains compatible with zirconia comprising up to about 75 wt% of titanium and at least 25 wt% of at least one noble metal selected from the group consisting of gold and the platinum group metals, wherein the alloy has a thermal expansion coefficient of from about 9 to 11 x 10^~6 at 25- 600⁰C.

9. A method of forming a dental device comprising: providing an alloy comprising about 75 wt% of titanium and at least 25 wt % of at least one noble metal selected from the group consisting of gold and the platinum group metals; and manufacturing the alloy into a dental device.

10. The method of claim 9, wherein the noble metal is palladium.

1 1. The method of claim 9, wherein noble metal is ruthenium.

12. The method of claim 9, wherein the alloy further comprises a total of up to 15% of at least one additional alloying material selected from the group consisting of aluminum, nickel, chromium, cobalt, molybdenum, niobium, vanadium, hafnium, zirconium, manganese, tin, iron and rare earth elements.

13. The method of claim 9, wherein the alloy has a thermal expansion coefficient of about 9 to 11 x 10^'6 at 25-600⁰C.

14. The method of claim 9, wherein the alloy has a thermal expansion coefficient of about 10 x 10 ⁶ at 25-600⁰C.

15. The method of claim 9, wherein the step of manufacturing uses a rapid prototyping process.

16. The method of claim 9, wherein the rapid prototype process is selective laser melting.

17. The method of claim 9, wherein the step of manufacturing uses a milling process.

18. The method of claim 9, further comprising nitriding the alloy.

19. The method of claim 9, wherein the dental device further comprises a zirconia compatible porcelain.

20. A dental device comprising a dental body formed of an alloy comprising about 75 wt% of titanium and at least 25 wt% of at least one noble metal selected from the group consisting of gold and the platinum group metals.

21. The dental device of claim 20, wherein the noble metal is palladium.

22. The dental device of claim 20, wherein noble metal is ruthenium.

23. The dental device of claim 20, wherein the alloy further comprises a total of up to 15% of at least one additional alloying material selected from the group consisting of aluminum, nickel, chromium and cobalt, molybdenum, niobium, vanadium, hafnium, zirconium, manganese, tin, iron and rare earth elements.

24. The dental device of claim 20, wherein the alloy has a thermal expansion coefficient of about 9 to 1 1 x 10 ⁶ at 25-600°C.

25. The dental device of claim 20, wherein the device further comprises a zirconia compatible porcelain.