Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/07—Alloys based on nickel or cobalt based on cobalt
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K6/00—Preparations for dentistry
  • A61K6/80—Preparations for artificial teeth, for filling teeth or for capping teeth
  • A61K6/84—Preparations for artificial teeth, for filling teeth or for capping teeth comprising metals or alloys

Definitions

• This invention pertains to an alloy having high strength and improved elongation and toughness that is particularly adapted for the production of cast dentures. More. particularly, this invention concerns an alloy having as its principal constituents cobalt, chromium and nickel, and containing minor but critical amounts of molybdenum and carbon.
• Cobalt-chromium alloys are widely used in the production of castings for denture appliances, either partial or complete. Dentists, dental technicians and patients have been dissatisfied with the performance of the available alloys because of certain inadequate physical properties. More specifically, due to the low elongation, inadequate toughness, and high hardness of the known chrome-cobalt alloys, minor but necessary adjustments required at the time of delivery to the patient are diflicult and consume valuable chair time. The technician or dentist must be extremely cautious to avoid bending a clasp attachment through more than about a five to ten degree angle or breakage occurs. Moreover, the available alloys lack of toughness is dramatically demonstrated by ready breakage of the dentures when accidentally dropped on the floor by the dentist or patient.
• the cobalt-chromium alloy of this invention alleviates the foregoing difliculties because of improved properties flowing from an unexpected critical combination of narrowly defined molybdenum and carbon contents.
• an alloy containing as essential ingredients at least 50 and up to 60 but preferably up to 55 percent cobalt, 20 to 28 percent chromium, 10 to 20 percent nickel, 3.7 to 4.1 percent molybdenum and 0.18 to 0.22 percent carbon, said alloy having an elongation of at least ten percent and a tough ness factor of at least 9000.
• the yield point of the alloy is greater than 50,000 p.s.i. and its hardness is not greater than about 310 DPH.
• the percentage of elongation is a measure of the amount an alloy will increase in length as it is drawn from a zero to the breaking point. Percentage of elongation has a direct relationship to cold shaping of an alloy as in the use of pliers to shape wire into clasps.
• the yield point is an indication of the behavior of a clasp as well as the entire denture frame under biting forces, which forces can easily produce stresses above the yield strength of an alloy deficient in that property causing the denture to shift out of proper occlusal' relationship to which it was originally designed.
• Toughness is the ability of an alloy to Withstand sudden shocks and blows that stress the alloy beyond its yield point but within its breaking strength.
• the toughness factor is defined herein as the product obtained by multiplying the percentage of elongation and the ultimate tensile strength of the alloy in pounds per square inch. Ultimate tensile strength (UTS) is the greatest unit stress an alloy will withstand in tension to the point of breaking.
• Other physical properties which may be evaluated in describing the alloys embodied herein are as follows: Hardness is the resistance of an alloy to surface penetration and is a measure of surface Wear effects. The hardness is determined herein as Diamond Point Hardness (DPH).
• the elongation is at least 10%, but in the preferred alloys can range to about 15%; the toughness factor is at least 9000 and can range up to about 13,000.
• This remarkable toughness feature is demonstrated by the fact that clasp attachment elements are highly adjustable, e.g., through an angle of from about forty to sixty degrees compared to only five to ten degrees of adjustment permitted without breakage for prior known alloys.
• iron content should not exceed 2%; manganese content should not exceed 1%; silicon content should not exceed 1%; boron content should not exceed 0.01%; and sulfur content should not exceed 0.02%. Phosphorus contamination should be avoided as this element causes hardness and embrittlement.
• the chromium content of the alloy should not be materially reduced not increased beyond the aforementioned ranges.
• An alloy having a low chromium content readily corrodes and high chromium causes brittleness.
• Increased cobalt content produces a harder alloy, whereas increased nickel content produces a softener material.
• the alloy of this invention provides an excellent balance of properties.
• molybdenum and tungsten are substantial equivalents in cobalt-chromium alloys, although in the present invention somewhat inferior results are obtained by such a substitution.
• tungsten When a portion of the molybdenum requirement of the alloy is replaced by an equivalent amount of tungsten, hardness is increased and castability is reduced; however the toughness value of the alloy, although somewhat reduced, is sufiicient for the uses intended.
• the alloys of Examples 9 and 10 contain the claimed amounts of Mo, Ni and Co, but carbon contents are outside the critical range; the alloys of Examples 11 and 12 contain the proper amount of carbon, Ni and Co, but the Mo content is not in the claimed range.
• the alloy of Example 8 that contains the proper amounts of Mo and carbon but the improper amounts of cobalt and nickel shows inferior properties.
• the alloy of Example 13 a composition as disclosed by E. R. Touceda in Fe Si Mn TABLE I Alloy composition, weight percent Cr N1 Mo US. 2,103,500, has a very low and unacceptable yield 15 strength.
• the alloy of Example 14 a composition as described by E. M. Prosen in US. 2,674,571, has poor elongation and toughness.
• a toughness factor of at least 9000 the toughness factor being the product obtained by multiplying the percentys p perties age of elongation and the ultimate tensile strength of said Yield alloy in pounds per square inch.

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• Health & Medical Sciences (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Chemical & Material Sciences (AREA)
• Veterinary Medicine (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Epidemiology (AREA)
• Plastic & Reconstructive Surgery (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Dental Preparations (AREA)

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Cited By (8)

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Citations (2)

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• 1969
  • 1969-03-12 US US806669A patent/US3544315A/en not_active Expired - Lifetime
• 1970
  • 1970-03-05 GB GB1264587D patent/GB1264587A/en not_active Expired
  • 1970-03-11 FR FR7008644A patent/FR2034842B1/fr not_active Expired
  • 1970-03-12 DE DE19702011854 patent/DE2011854A1/de active Pending

Patent Citations (2)

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