Noble and high-noble alloys used in casting crowns are generally based on alloys of gold.
Gold is not used in its pure form as it is too soft and has poor mechanical strength.
Other metals included in gold alloys are copper, platinum, palladium, zinc, indium and nickel.
All types of gold casting alloys used in prosthodontics (Type I - IV) are categorised by their percentage content of gold and hardness, with Type I being the softest and Type IV the hardest.
Generally, Type III and IV alloys (62 - 78% and 60 - 70% gold content respectively) are used in casting of full crowns, as these are hard enough to withstand occlusal forces.
Gold crowns (also known as gold shell crowns) are generally indicated for posterior teeth due to aesthetic reasons.
They are durable in function and strong in thin sections, therefore require minimal tooth preparation.
They also have similar wear properties to enamel, so they are not likely to cause excessive wear to the opposing tooth.
They have good dimensional accuracy when cast which minimises chair-side/appointment time and can be relatively easy to polish if any changes are required.
Palladium based alloys are also used.
These were introduced as a cheaper alternative to gold alloys in the 1970s.
Palladium has a strong whitening effect giving most of its alloys a silverish appearance.
Noble and high-noble alloys used in casting crowns are generally based on alloys of gold. Gold is not used in its pure form as it is too soft and has poor mechanical strength. Other metals included in gold alloys are copper, platinum, palladium, zinc, indium and nickel. All types of gold casting alloys used in prosthodontics (Type I - IV) are categorised by their percentage content of gold and hardness, with Type I being the softest and Type IV the hardest. Generally, Type III and IV alloys (62 - 78% and 60 - 70% gold content respectively) are used in casting of full crowns, as these are hard enough to withstand occlusal forces. Gold crowns (also known as gold shell crowns) are generally indicated for posterior teeth due to aesthetic reasons. They are durable in function and strong in thin sections, therefore require minimal tooth preparation. They also have similar wear properties to enamel, so they are not likely to cause excessive wear to the opposing tooth. They have good dimensional accuracy when cast which minimises chair-side/appointment time and can be relatively easy to polish if any changes are required. Palladium based alloys are also used. These were introduced as a cheaper alternative to gold alloys in the 1970s. Palladium has a strong whitening effect giving most of its alloys a silverish appearance.
Crown (dentistry)