A crown is a tooth-shaped cover placed over a tooth that is badly damaged or decayed. A crown, which many people call a cap, is made to look like your tooth.

Crowns may be placed for several reasons, but generally the tooth has been extensively damaged by decay or breakage and filling material can't replace the missing tooth structure and make the tooth strong enough. A crown may hold together parts of a cracked tooth and can be used to hold a bridge in place. Crowns also are used for cosmetic purposes to cover misshapen or badly discolored teeth.

Crowns can be prefabricated or made in a laboratory. Prefabricated crowns are made of plastic or stainless steel and can be used as a temporary restoration until a permanent crown is manufactured. In some cases, prefabricated crowns can be used as a permanent restoration.

Crowns can be all metal, porcelain fused to metal (PFM), or all ceramic. Metals include gold alloy, other alloys (palladium) or a base-metal alloy (nickel or chromium). The all-metal or PFM crowns are stronger and are better choices for back teeth. PFM and all-ceramic crowns look just like normal teeth.

Usually, crowns last at least 7 years, but in many cases they last much longer, up to 40 years or so.