A crown is a restoration that covers, or "caps," a tooth to restore it to its normal shape and size, strengthening and improving the appearance of a tooth. Crowns are necessary when a tooth is generally broken down and fillings won't solve the problem. If a tooth is cracked, a crown holds the tooth together to seal the cracks so the damage doesn't get worse. Crowns are also used to support a large filling when there isn't enough of the tooth remaining, attach a bridge, protect weak teeth from fracturing, restore fractured teeth, or cover badly shaped or discolored teeth.