Palladium based alloys

Abstract

A palladium-based alloy having a coefficient of thermal expansion (CTE) of about 12.0 to about 13.0 and having one or more of the following additive metals: platinum, gallium, molybdenum, tin, silicon, ruthenium, rhenium, indium, tungsten, niobium, boron and lithium.

Claims

1. A dental article comprising: a non-magnetic dental alloy substrate free of gold, copper, and silver consisting essentially of palladium, platinum, gallium, molybdenum, ruthenium and rhenium and optionally one or more of tin, silicon, indium, niobium, tantalum, tungsten, boron, and lithium and having a CTE in the range of about 11.5 to about 13.010.sup.6/ C. at 25-500 C.; and a ceramic or glass ceramic having a CTE in the range of about 8.0 to about 1310.sup.6/ C. at 25-500 C. pressed onto the dental alloy substrate.

2. The dental article of claim 1, wherein the CTE of the dental alloy is in the range of about 12 to about 13.010.sup.6/ C. at 25-500 C.

3. The dental article of claim 1, wherein the CTE of the ceramic or glass ceramic is in the range of about 12 to about 12.8010.sup.6/ C. at 25-500 C.

4. The dental article of claim 1, wherein the ceramic or glass ceramic comprises lithium silicate.

5. The dental article of claim 4, wherein the lithium silicate comprises lithium metasilicate, lithium disilicate or a mixture thereof.

6. The dental article of claim 5 fabricated as a crown, bridge, veneer, inlay, onlay, partial crown, fixed partial denture, implant abutment, implant, orthodontic appliance, space maintainer, tooth replacement appliance, splint, dentures, post, teeth, jacket, facing, veneer, facet, cylinder, or connector.

Description

DETAILED DESCRIPTION

(1) The alloy is based on a portion of the palladium-platinum binary system and has a coefficient of thermal expansion (CTE) in the range of about of about 12.0-12.710.sup.6/ C. at 25-500 C. and 12.4-13.010.sup.6/ C. at 25-600 C. The alloy of the invention can have a solidus high enough that no melting occurs during firing of glass ceramics and ceramics, and a coefficient (CTE) in a range that has been demonstrated to be compatible with glass ceramics and ceramics. It may include one or more of the following additive metals: Ga, Sn, Si, Ru, Re, In, Nb, Mo, Ta, W, B, Au, and Li for dental prostheses to improve physical, chemical, mechanical and handling properties.

(2) It may be used for the application of glass ceramics and ceramics having CTEs that are close to/compatible with the CTE of the alloy. Examples of suitable glass ceramics are lithium silicate ceramics including but not limited to, lithium metasilicate and lithium disilicate based glass ceramics. Other ceramics and glass ceramics having similar CTEs are also suitable for use with this alloy. Ceramics and glass ceramics having CTEs in the range of about 8 to about 1310.sup.6/ C. (100-500 C.), and more preferably about 9 to about 1210.sup.6/ C. (100-500 C.) may be used with the alloys described herein.

(3) The glass ceramic or ceramic with a low CTE may be pressed onto the metal substrate. The coefficient of thermal expansion for lithium silicates is about 10.550.3510.sup.6/ C. (100-500 C.). Any type of dental restoration may be fabricated including, but not limited to, single unit, short span and long span bridges.

(4) There are several properties exhibited by alloy(s) of the present invention that make it suitable for press on metal (PoM) applications. The alloy is grey in color with an oxide coating for bonding glass ceramic or ceramic to the oxidized cast alloy substrate. The alloy has mechanical properties for cast prostheses and for the support of the glass ceramic or ceramic and is readily polished to a bright sheen.

(5) The alloy of the invention can be readily cast by normal dental procedures, and can be recast using normal dental laboratory procedures. The cast alloy unit can be ground and polished to a high shine. The alloy can have a light oxide color that does not affect the apparent color of the ceramic or glass ceramic layer and the oxide does not increase during the firing of the ceramic or glass ceramic. When heated to the ceramic or glass ceramic firing temperature, a thin, continuous, and tenacious oxide is formed, which enters into a bond with the ceramic or glass ceramic. The alloy has a strength that withstands loads in excess of those that would cause pain to the patient.

(6) The alloy of the present invention can meet aesthetic needs while using a palladium-platinum base. That is, the alloy system reproduces the normal coloration of natural dentition. The enamel layer of healthy natural dentition is quite translucent and ceramic or glass ceramic can be made with similar translucency. The translucency of enamel allows the color of healthy dentine to be seen. This color normally has a yellowish tint. With the ceramic or glass ceramic alloy combination, a layer of oxide must be present to form a bond with the ceramic or glass ceramic. While high gold alloys may provide a yellowish background for the ceramic or glass ceramic, other metals such as palladium, platinum etc., provide a suitable gray background.

(7) Moreover, applying or pressing a high strength ceramic or glass ceramic such as lithium silicate onto the metal framework provides not only good aesthetic properties but also excellent wear resistance reducing brittleness and chipping that may result when using porcelain-fused-to metal (PFM) restorations.

(8) For proper bonding, the alloying elements form an oxide on the cast metal surface. This dark gray to black colored oxide layer, can affect the apparent color of the ceramic or glass ceramic veneering layer. The alloy system of the present invention may include elements added to regulate the amount and color of the oxide layer and melting characteristics, selected from the group including, but not limited to: indium, tin, boron, silicon, and/or gallium.

(9) The mechanical properties of the alloy follow ANSI/ADA specification #38 and ISO standard ISO22674 and ISO9693 which require a 0.2% offset proof stress/yield stress or yield strength of at least about 250 MPa for the alloy. This alloy exhibits much higher yield strength of greater than about 360 MPa with % elongation greater than about 5.0 to qualify as a Type 4 alloy per ISO 22674. To attain such strength, significant amounts of alloying elements such as, but not limited to, platinum, gallium, indium, tin, silicon, molybdenum and/or tungsten may be added to the alloy formulation.

(10) The above mentioned standards do not require minimum or maximum values for coefficient of thermal expansion (CTE); however, physical properties including the CTE value for both ceramic or glass ceramic and alloy may be regulated. The alloy of the invention may include elements added to regulate the grain size, selected from the group including, but not limited to: gallium, tungsten, rhenium and/or ruthenium. Elements that can be added to regulate oxidation during melting and casting include but are not limited to: boron, lithium, silicon, and/or gallium. Also, heat transfer rate may be taken into consideration. When cooling from the ceramic or glass ceramic firing temperature, shrinkage of both ceramic or glass ceramic and alloy take place and the alloy, which cools faster, shrinks faster and thus puts tensile forces on the ceramic or glass ceramic to metal bond. If this disparity of shrinkage is too much, the ceramic or glass ceramic will no longer be bonded to the alloy or the ceramic or glass ceramic will crack when the composite reaches room temperature. An alloy that is compatible with ceramics or glass ceramics will have a CTE that is in a range that is closely matched to the CTE range of the ceramic or glass ceramic that will be fused to the alloy. Closely matching the CTE of an alloy to the CTE of a ceramic or glass ceramic will diminish the likelihood that the ceramic will debond from the alloy after fusing, or that cracks will develop in the ceramic or glass ceramic after fusing to the alloy. Examples provided herein offer alloys that have been developed that have CTE values that are matched appropriately.

(11) It is readily understood that the solidus of the alloy must be sufficiently higher than the firing temperature of the ceramic or glass ceramic so that the alloy is not even partially melted during firing. Concerning the bonding of the ceramic or glass ceramic to the alloy of the invention, it does not occur between ceramic or glass ceramic and metal, it occurs between ceramic or glass ceramic and the metal oxide layer formed when the alloy is heated prior to and during the firing of the ceramic or glass ceramic. If the oxide is not adherent to the alloy, it can be simply removed by the ceramic or glass ceramic. Some of the bond is simply mechanical but the primary bonding takes place as diffusion of metal oxide in ceramic or glass ceramic and vice versa. If the oxides are not soluble in the ceramic or glass ceramic and/or vice versa, no bond takes place. When the ceramic or glass-ceramic is fired, small particles and larger particle surfaces are fused (melted) and this liquid glass ceramic and the metal oxide layer form a solution by either liquid or solid diffusion. This concept is further described in copending U.S. application Ser. No. 11/892,933 and Ser. No. 13/181,172, which are hereby incorporated by reference.

(12) For certain alloys herein, the solidus point, which is defined by the starting of the melting range, is at least about 750 C. and preferably greater than about 900 C. in order to accommodate the use of high fusing ceramic or glass ceramics in the market without any distortion of the dental prosthesis. It further allows repair work using pre-solders available in the market with no damage to the restoration. For certain alloys herein, the liquidus point, which is defined by the end of the melting range is not greater than about 1350 C. for easy melting of the alloy. For most of the induction casting machines on the market, the maximum temperature limit is 1500 C. In order to melt the metal and reach the proper fluidity for casting, at least 100 C. above the liquidus point of the alloy must be reached.

(13) It is preferable that the composition comprises the following components:

(14) TABLE-US-00001 TABLE 1 Weight Percent Weight Percent Weight Percent Weight Percent Element Range 1 Range 2 Range 3 Range 4 Palladium about 74.5%-about about 76.0%-about about 79.5%-about about 79%-about 88.5% 86.0% 85.0% 85% Platinum about 3.6%-about about 4%-about about 5.0%-about about 5.5%-about 12.0% 10.0% 9.0% 7.0% Gallium about 1.7%-about about 2.5%-about about 4.2%-about about 5.0%-about 9% 8.5% 8.5% 8% Molybdenum about 0.1-about about 0.1-about about 0.1-about about 0.5-about 5.0% 4.5% 4.0% 3.6% Tin 0-about 7.0% about 0.5-about about 0.5-about about 0.5-about 6.0% 5.0% 3.5% Silicon 0-about 1.2% 0-about 1.2% 0-about 1.2% 0-about 1.2% Ruthenium about 0.1%-about about 0.1%-about about 0.1%-about about 0.1%-about 0.8% 0.8% 0.8% 0.8% Rhenium about 0.1%-about about 0.1%-about about 0.1%-about about 0.1%-about 0.8% 0.8% 0.8% 0.8% Indium 0-about 7.0% about 0.5-about about 0.5-about about 0.5-about 6.0% 5.0% 3.5% Niobium 0-about 1.0% 0-about 1.0% 0-about 0-about 1.0% 1.0% Tungsten 0-about 0.5% 0-about 0.5% 0-about 0.5% 0-about 0.5% Boron 0-about 0.1% 0-about 0.1% 0-about 0.1% 0-about 0.1% Lithium 0-about 0.10% 0-about 0.1% 0-about 0.1% 0-about 0.1% Tantalum 0-about 1.0% 0-about 0.4% 0-about 0.3% 0.5-about 0.2% Gold 0-about 8% about 0.6-about about 0.6-about 0-about 1.6 6.0% 5.0%

(15) The C.T.E (at 25-600 C.) of the alloy should be between about 12.0 and about 13.810.sup.6 PC. The CTE (at 25-500 C.) of the alloy should be between about 11.5 and about 13.010.sup.6/ C. and preferably between about 12.0 and about 13.010.sup.61 C. more preferably between about 12.0 and about 12.810.sup.61 C. in order to work with most of the high fusing ceramic or glass ceramics on the market. It is preferable that the CTE not exceed 13.010.sup.6/ C.

(16) It should be noted that any incremental sub-ranges within the ranges specifically identified are also covered as useable alloys herein. Ranges of increments of 0.001% within those ranges are contemplated to be possible examples of the present invention.

(17) The gallium, indium, tin, silicon and boron in the composition aid in controlling the liquidus temperature and improve the melting and casting properties. The platinum, niobium, molybdenum and tungsten in the composition assist in controlling the CTE, more specifically, in reducing the CTE.

(18) The combination of In, Sn, Si, Ga, B, and Li reduces the temperature, improves the fluidity of the molten alloy and controls the CTE. The combination of Pt and Pd increases the corrosion resistance, controls the CTE and improves biocompatibility. The combination of Pt, Mo and W controls the CTE by reducing the number. It is preferable that the combination of Pt and Pd are equal to or greater than about 75%. It is preferable that the Pt is greater than about 10% to assist in lowering the CTE of the alloy.

(19) Although the combination of Au having a melting temperature of 1065 C. and Pd having a melting temperature of 1554 C. provides an optimal melting temperature for the dental alloy, compatible with many dental ceramic or glass ceramics, it is preferable to have a gold-free, copper-free and silver-free alloy in order to achieve a low CTE compatible with the low CTEs of the glass ceramics and ceramics such as lithium silicate ceramics.

(20) Moreover, the compositions set forth in Tables are nonmagnetic.

(21) The following examples are for the purpose of illustration. It is understood that such detail is solely for that purpose, and variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention which is defined by the following claims.

Examples 1-25

(22) TABLE-US-00002 TABLE 2 Example No. 1 2 3 4 5 6 7 8 9 Pd 74.5 76 79.5 79.5 79.2 84.9 85.2 85.9 85.5 Pt 5 4.6 5 5 5 4.5 5.2 4.5 4.5 Ga 6.5 6 3.8 3.9 1.7 9 7.8 5.6 8.4 Sn 7 7 4.5 4 3.6 0.8 1.0 1.4 0.5 Si 0.8 0.8 1.2 1.2 0.5 0.1 0.1 Ru 0.1 0.1 0.1 0.1 0.1 0.6 0.6 0.5 0.8 Re 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.5 0.3 In 1.2 Nb 0.6 Mo B Li Au 6 5 5.8 6.2 8 1.6 Melting 816.9- 815.5- 771- 763- 794- 1076- 820- 810- 812- Range 834 C. 836 C. 803 C. 796 804 1217 1112 C. 1100 C. 1113 C. CTE 12.55 12.6 12.62 12.43 12.24 12.97 13.1 12.66 13.2 (25-500 C.) CTE 12.96 13.01 12.83 12.7 12.52 13.25 13.3 13.0 13.4 (25-600 C.) Hardness HvAC: HvAC: HvAC: 278 181 250 HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: 284 170 241

(23) TABLE-US-00003 TABLE 3 Example No. 10 11 12 13 14 15 16 17 18 Pd 88.1 88.5 84.9 85 84 84 84 83 81.5 Pt 3.9 3.6 4.5 4.5 5.5 5.5 5.5 6 7 Ga 6.0 5.3 8 8.6 7.1 8.1 8.1 7.5 7.5 Sn 0.8 1.2 0.8 0.7 0.6 0.6 0.7 0.7 Si Ru 0.8 0.8 0.6 0.6 0.6 0.8 0.8 0.6 0.6 Re 0.4 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 In 0.6 Nb 1.0 0.8 0.6 Mo 0.4 0.4 0.8 1.5 B Li Au 0.6 0.6 Melting 932.7- 971.4- 1204- 1180- 1004- 1206- 1194- 1168- 1189- Range 1095 C. 1131 C. 1287 C. 1258 C. 1244 C. 1272 C. 1257 C.; 1228 C.; 1209 C. 1201- 1197- 1273 C. 1220 C. CTE 12.78 12.84 12.97 13.41- 13.5 13.47 13.36 13.10- (25-500 C.) 13.57 13.25 CTE 13.10 13.14 13.20 13.62- 13.75 13.74 13.58 13.35- (25-600 C.) 13.75 13.54 Hardness HvAC: HvAC: HvAC: HvAC: HvAC: HvAC: HvAC: HvAC: HvAC: 189 179 221 247 227 234 245 237 233 HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: 187 177 188 237 240 231 246 242 235

(24) TABLE-US-00004 TABLE 4 Example No. 19 20 21 22 23 24 25 26 Pd 80.6 80 79.2 79.07 78.85 70.05 68.70 80.0 Pt 7.4 7.2 7.4 7.5 7.5 9.0 12.0 7.5 Ga 8 8 8 8 8 8.5 8.0 7.5 Sn 0.6 0.5 0.6 0.5 0.5 0.5 Si Ru 0.5 0.4 0.4 0.4 0.4 0.5 Re 0.5 0.4 0.4 0.4 0.4 0.8 0.6 0.5 In 6.0 7.5 Ta 0.1 Nb 0.4 0.4 0.4 0.5 0.5 Mo 2 3.1 3.6 3.5 3.5 5.0 3.0 W 0.5 B 0.08 0.08 0.05 0.10 Li 0.05 0.10 0.10 0.10 0.1 Au Melting 1100- 1101- 1087- 1083- 1100- 1040- 1039- 1131.9- Range 1180 C. 1185 C.; 1169 C.; 1206 C.; 1205 C. 1089 C. 1091 C. 1190 C. 1092- 1109- 1080- 1208 C. 1200 C. 1181 C. CTE 13.19 12.99 12.92- 12.67; 12.45 12.8 13.00 12.5 (25-500 C.) 13.09 12.46; 12.63 CTE 13.5 13.29 13.16- 12.87; 12.70 13.09 13.30 (25-600 C.) 13.35 12.79; 12.96 Hardness HvAC: HvAC: HvAC: HvAC: HvAC: HvAC: HvAC: 231 239 249 247; 245 396; 414; HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: HvPC.sub.IL: 231 212 223 245 240 389 398

(25) All numbers expressing quantities of ingredients, constituents, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term about. Notwithstanding that the numerical ranges and parameters set forth, the broad scope of the subject matter presented herein are approximations, the numerical values set forth are indicated as precisely as possible. Any numerical value, however, may inherently contain certain errors resulting, for example, from their respective measurement techniques, as evidenced by standard deviations therefrom.

(26) Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.