When a failing filling, a broken cusp, or decay do not leave a tooth with enough natural structure to allow for its repair with a filling, bonding, or inlay/onlay restoration, it becomes necessary to restore the tooth with a full crown.
In most instances these full coverage dental restorations are made of an outer layer of porcelain fused to a precious metal shell, so that the metal is not visible. In some instances, it is possible to make crowns of a porcelain/ceramic material that affords optimal esthetics, especially for anterior teeth and posterior teeth that are visible within the patient's "smile display" . It sometimes becomes necessary to make a crown entirely out of a gold alloy, usually on the backmost teeth, especially in people who have very strong bites or teeth-grinding (bruxism) habits.
All of these crowns are strong, long-lasting and absolutely stunning in their recreation of natural teeth. And the color in the porcelain and combination porcelain/gold crowns is so natural, you'll have a very difficult time telling these from your original teeth.