When you visit a dental office for an examination, the dentist may find a large cavity that requires a porcelain crown. These dental restorations are also used for covering teeth that are damaged during injuries from a vehicular accident or a fall while playing sports. In addition to porcelain crowns that are made to protect damaged or infected teeth, there are full-size crowns that are made to replace missing teeth. These types of crowns are attached to dental bridges, denture supports or dental implant posts. It is also possible for an old crown to degrade, and a dentist can replace it with a new one. In the past, it could take several days to have a porcelain crown made for a tooth, but today, many dentists can order the dental restoration in the morning, and the dental laboratory will have the crown ready in the afternoon.