CA1040893A - Non-precious alloy for fusion to porcelain - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A nonprecious alloy for dental restorations fused to porcelain includes the following ranges of constituents in per-centages by weight:

Description

104~893 An extremely effective agent for achieving optimum bonding between the alloy and porcelain is the following com-po~ition in percentages by weight, which is painted onto the alloy in slurry form and fired to prepared the surface for bonding to porcelain.
Constituent Proportions ~,old Powder 34.96 ~5-15 microns) Body Porcelain 26.22 ~Hi-Life*) Zirconium oxide 8.74 (10 microns) Bonding Agent Liquid 30O08 (low fusing "flux"
soluble in a vehicle such as glycerine or an alcohol) *Hi-Life is a trademark of Howmedica Inc. Dental Division - of ~hicago, Illinois A metal alloy for making a dental restoration must be strong, tough, resistant to tarnish, oxidation and corro-sion, compatible with the human oral environment, ~biocompa- -tible), have a ~uitable coefficient of thermal expansion, be fu~ible to porcelain and have good castability. Most effective dental alloys are relatively expensive because of their high noble metal content. An object of this invention is to provide a highly effective and relatively simple and economical nonprecious alloy suitable for dental use including fusibility to porcelain.

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- - . ~ --- 1~40893 In accordance with this invention a highly effective and relatively economical nonprecious alloy for dental use incorporates the following ranges of constitutents in per-centages b.,v weight.
Constituent Proportional Range Nickel Balance Chromium 10.0-22,0 Aluminum 1,0-5.0 Silicon 0,5-2,0 Manganese 0.01-0.2 Molybdenum 0.0-7,0 An element selected from the grouP consistinq of Strontium, lanthanum and zirconium or a combination of strontium and zirconium, 0.0-2.0 gallium, and 1O0-3.0 iron 0.0-i~0 Particular examples of alloys of this invention are listed below in Example I giving preferred compositions and pro~
portional ranges in percentages by weightO ~hese alloys have been found particularly useful for dental service and are par-ticularlyeffective for usion and tight adherance to porcelainO
Exam~le I
Element ~ Composition Ra~ge Nickel 78.1 Balance Chromium 13.5 10O0-22.0 Molybdenum 1,5 0O0-3,0 : , Aluminum 3O0 1,0-5,0 Silicon 1.0 0~5-2O0 Manganese 0.1 ODO1-OO2 `` 194~
Element ~3e5~ L5~a~l~bLE1æ~ Composition Range An element selected from ~ group oon-sistin~ of strontium, lanthanum an~or ziroon~um or a ~x~i~ation of 0 0-2 0 strnntlum and zlrcomum~ O.5 -~.allium 2~0 1.0-3.0 Iron 0.3 0.0-1.0 All oxbinations of strontium, lanthanum and zirconium within the recited ranges are effective and a useful such constituent is a 50~-50~ combination of strontium and zirconium.
1~ The bonding system that is necessary to achieve optimum bonding between the alloy and the porcelain is as follows:
Constituent Proportions Gold Powder 34.96 (5-15 microns) lS Hi-Life Body Porcelain 26.22 Zirconium oxide 8.74 ~10 microns) Bonding Agent Liquid 30,08 Hi-Life is a trademark of ~owmedica Inc., Dental 2n Division, Chica~o, Illinois for a porcelain having approximately the followin~ formulation in percentages by weight.
Constituent Composition SiO2 68.64 A123 13.76 CaO 0.36 K2O 13.46 Na2O 2.29 Li20 1.49 The porcelain can also be any porcelain which has a similar formulation, is intended for fabrication of fused por-celain prostheses, and has a softening point of about 1200-1400F.

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~41)~3 ~he bonding agent liquid is a low fusing "flux" soluble in a vehicle such as glycerine or an alcohol. The flux may be boron oxide or its salts, such as sodium borate or light element oxides, i.e. Li20, Na20 and those light element oxides of the first column of the periodic tableO The essential characteristic is that the flux will react with the porcelain and with oxides which are formed on the alloy during firing of the bonding agent, to produce a low solubility, high tenacity, adherent intermediate layer of oxides to which porcelain will adhere during subse~uent application and firing. A range of composi-tions can be effective under these conditions -- a typical range would be that involving the following composition:
500 cc. glycerine 10-30 grams boric anhydride 1.14 cc. wetting agent Another highly suitable bonding agent utilizing the addition of a thixotropic agent such as Cab-o-Sil, maintains all powders in solution for more consistent application and improve the "painting" characteristics.
Such a formulation is as follows by weight per cent -Glycerine 94.954 .. . .

Victawet No. 12 00237 Cab-o-sil 2,307 Victawet ~12 is the trademark of Victor Chemical Works for a non-foaming, non-ionic wetting agent of the type (RO)PO-(OR')2, where R is a medium-chain alkyl group, and R' is a water-solubili2ing group. P205 content is 16%. It is an amber-colored liquid; sp,gr. 1.121; pH, 4.7 (005% solution); surface tension, 28.8 dynes/cm. (0.2% solution 29C); Draves test, 902 sec at 0.6~ conc., and 32 sec. at 0.2% conc. (in hard water) insoluble -` 10~ 93 in naphtha; soluble in alcohols, acetone toluene; forms a milky solution in water~ Uses: As a wetting agent in acid and alkaline solutions, and as a carrier for acid dyesO It provides level shades and uniform penetration in package dying of nylon, etc.
Cal-o-sil is the trademark of Godfrey L~ Cabot, Inc.
or a colloidal silica prepared in a hot gaseous environment by a vapor-phase hydrolysis of a silicon compound instead of by the usual a~ueou~ precipitation process~ Its outstanding properties are high chemical purity, low water content, enormous external surface area, and high degree of particle separationO Cab-o-sil functions in extremely small quantities as a reinforcing agent in rubber and plastics, a suspending and flatting agent in paints, a~ a thixotropic agent in various resins, as an emulsion stabili-zer, and as a thickening and gelling agent~
The manner in which the above liquid is used as a bond-ing agent is as follows: A thin slurry is made using Liquid #2A
and the opa~ue or undercoat porcelain~ This is then painted onto the appliance in the areas which are to receive porcelain and the slurry is then fired, A specific ratio of powder/liquid 2~ is not reauired, The conditions which are necessary for success are that the slurry is paintable and, after painting, produce a general blocking out of the underlying metal colorO
It is believed that the particular constitutents have the following functions in the alloys of this invention:
Nickel - Major component chosen for its inherent resistance to corrosive attackO
Chromium - To enhance the corrosion resistance of the alloy and also as a solid solution strenghener 1~
Mol~bdenum - Enhances the corrosion resistance of -` 1()40~3 the alloy and adjusts the coefficient of thermal expansion of the alloyO
Aluminum - Added as a deoxidizer and effects the coefficient of thermal expansion of the alloyO
Silicon - Added as a deoxidizer and also aids in obtaining fluidity for ease of casting~
Manganese - Acts as a safeguard against any possible sulfur contamination Iron - Lowers the coefficient of thermal expansion and contributes to the metal to porcelain bond, Lanthanum~ strontium, zirconium - The function of these elements is to effect a porcelain to metal bondO
~allium - Improves the bonding characteristics and increases the fluidity of the alloy to facilitate casting~ -These alloys were designed for use as an under-struc-ture onto which porcelain is fused for making a fixed bridge type of dental restorationO General characteristics of these alloys are:
lo Ability to successfully melt and cast using either an oxy/acetylene torch or an induction type casting machine.
2, Precision dental castings can be achieved when cast into dental investments,

3. Matching coefficients of thermal expansion between the alloys and the porcelains which are currently - .
3~ being used~ :.

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4. Corrosion resistance to oral cavity fluids and tissue tolerance,

5, Brinell Hardness values in the range of 170-210.

6. Mechanical properties sufficient to withstand the forces employed in the mouth during mastication.
Aside from the practical evaluation of these alloys which involved the construction of porcelain fused to metal bridges, the following specific properties were determined in the manner described below.
-- Coefficient of Thermal Expansion Equipment - Theta Dilatronic I, automatic recording dilatometer D
Test specimen - 2.000 " long x 0.250" diameter Test method - Determine the coefficient of thermal expansion between 200F and 1200F, -- Hardness Equipment - Rockwell Hardness tester Test specimen - cast piece 1/2" x 3/4" x 1/8" thick~
Test method - the hardness numbers were determined in three states:
1, As Cast Condition 2. Annealed - quenched af~er heating for 10 minutes at 1290F.
3, Heat treated - 1800F. for 30 minutes followed by a slow air cool.
Conversion to Brinell hardness via conversion chart for this type of alloy.
-- Tensile Properties Equipment - Instron Tensile Machine Test Specimen: cast piece 2-7/8" long with 12024 ~: , . , ., .-,: :
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- 1~4~)893 threaded ends and a radius of 1/4" from the threaded portion to the test area. The test area is 1-3/8"
long with a diameter of .09" + .01" diameter.
NOTE: This is the specimen required by the ADA in Specification No. 14.
-- Corrosion and Tarnish Resistance Adequate corrosion resistance was determined through a compilation of results of test involving implant studies, in-vitro corrosion resistance vs. a negative control, and through clinical evaluations. Tarnish resi~tance is evaluated by exposure to a dilute iodine-alcohol solution at 37Cr The ~ollowing properties were determined from the afore-mentioned tests:
A tvpical alloy gives the following results: -As Cast Condition proportional Limit ~psi) 60,000 0.2 Yield Stress (psi) 75,000 Ultimate Tensile Strength ~psi) 85,000 Elastic Modulus (psi) 25-26 x 106 Elongation ¢%) 2015 Hardness, Rockwell B 93-99 Heat Treated Condition Proportional Limit (psi) 40,000 -0.2% Yield Strength ¢psi) 51,000 Ultimate Tensile Strength (psi) 75,000 Elastic Modulus ~psi) 25-26 x 106 Elongation ~%) 6~6 Hardness, Roc~well B 85091 Thermal Expansion 8.25 x 10-6 in/in F.
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Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A nonprecious alloy consisting essentially of the following constituents in the indicated percentages by weight:

2. A nonprecious alloy consisting essentially of the following constituents in the indicated ranges of percentages by weight:

3. A nonprecious alloy consisting essentially of the following constituents in the indicated ranges of percentages by weight: