A crown, also known as a cap, is a tooth-shaped cover placed over a damaged, decayed, or misshapen, or badly discolored teeth. There are several situations where dental crown may be needed such as protection of a weak or a cracked tooth from breaking, covering and supporting a tooth with a large filling when there isn't a lot of tooth left, holding a dental bridge, or simply making a cosmetic modifications. A crown can also be placed on top of an implant to provide a tooth-like shape and structure.
Crowns can be all metals, Zirconia, Porcelain fused to metal (PFM), Porcelain fused to zirconia, 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 than ceramic crowns. PFM and all-ceramic crowns are the same color as your natural teeth. They look just like normal teeth.” Which type is best for you will be determined in part by your occlusion (how your teeth meet) and whether you grind your teeth. The final choice is up to you and your dentist.
Crowns usually last at least 7 years. In many cases they last much longer, up to 40 years or so. In many cases the crown is fine, but the tooth underneath it has developed a cavity. Therefore, maintaining good oral hygiene, including brushing and flossing, will help your crown last longer.