Dental gold alloys with age-hardenability at intraoral temperature

Dental gold alloys with age-hardenability at intraoral temperature were developed. Either 3 or 6 at% Ga, Al, Zn, In, Ni or Pd were added to an equiatomic AuCu alloy and the effect of additives on the low-temperature age-hardenability was examined. Alloys containing Ga, Al or Zn exhibited excellent low-temperature age-hardenability. The hardness of an alloy containing 6 at% Ga or 6 at% Al was doubled in one to ten days by ageing at 37 °C. Pronounced hardening was not demonstrated in an as-cast alloy, but solution treatment for only a few minutes provided enough age-hardenability. The age-hardening rate at low temperature related closely with the melting temperature of the alloy. Experimental gold alloys exhibited electrochemical behaviour similar to that of a commercial Type IV gold alloy. It is therefore concluded that AuCu alloy with added Ga, Al or Zn is expected to have enough age-hardenability and corrosion resistance for clinical use in the oral environment.