Crowns. Crowns are restorations that are placed when there is more extensive loss or weakening of tooth structure due to caries or trauma. A crown is an indirect restoration, which means that it requires an impression and is made outside of the mouth in the lab.
Crowns can be made from many materials but they can be classified into three categories: gold, porcelain fused to metal (PFM), and all porcelain.
Gold. There are many advantages to gold crowns. They require removal of less tooth structure and cause less wear on the opposing teeth. The disadvantage is that they are not as esthetic as a restoration made with porcelain. The gold that is used to make crowns is actually a mix of various noble, precious, and other metals that give the alloy properties that allow for fabrication, are strong enough to withstand forces in the mouth, and resist corrosion. Full gold crowns are especially indicated in posterior teeth in patients with a habit of clenching or grinding.
Porcelain fused to metal. Porcelain can be fused to a thin layer of gold to make a crown that is much more esthetic than a full gold crown. Porcelain is able to mimic the appearance of a natural tooth better than other materials. The gold substructure gives the porcelain strength similar to the porcelain found in a bathtub. The disadvantages are that they require removal of more tooth structure than gold, and the porcelain is more prone to fracture than a full gold crown.
All porcelain. Crowns can also be made completely out of porcelain. These crowns can be made to be more esthetic than other materials. Newer materials have made it possible to fabricate all porcelain restorations that conserve tooth structure and have excellent strength and wear.
When you have a crown made at the dentist, they will give you anesthesia, remove infected or defective tooth structure, take impressions, and place a temporary crown. After the crown is made, you return to the office and it is adjusted and cemented with a permanent cement.