A crown is used to restore a tooth that has had a large amount of damage due to decay or wear. Crowns cover the entire tooth and strengthen and protect it. Bicuspids and molars endure high amounts of compression during chewing and especially with teeth grinding and clenching. Zirconia is a special kind of ceramic that has a higher compression strength than some metals and as an added bonus has a high bio-compatibility. Where some metal crowns may be strong, many metals in many people cause low level allergy. With Zirconia crowns, this instance is lower.
Crowns are used to restore a tooth that has a filling that is large and has tooth decay around it. When a tooth has had a large enough cavity that more of the tooth is made of filling than tooth, it is time to consider a crown. Fillings only fill in the space where the cavity was, thus called a filling. Fillings do more to split a tooth than strengthen it and when the filling is too big, it can lead to a cracked or broken tooth. A crown can prevent this.
Crowns are also used when a tooth is cracked. Cracked teeth occur for many reason: biting on something that is too hard, teeth grinding, large fillings. You know when you have a cracked tooth because it hurts to chew or bite down. Depending on how deep the crack is, a crown alone can support the tooth and take these symptoms away. Occasionally, the tooth will need a root canal to stop the symptoms.
When a tooth has had to have a root canal, the tooth will need a crown. In order to complete a root canal in a tooth, the tooth is significantly weakened in its structure and needs to be strengthened by a crown before chewing on it. It is considered the "Standard of Care" in to place crowns on teeth that have had root canals.
Crowns also may need to be replaced. After they have been in the mouth many years they can begin to leak bacteria around the margin causing caries or decay to the tooth. If the crown is removed and any underlying caries or decay is removed the tooth can be crowned again starting the clock over again with a fresh new crown. If the crown is not removed and the bacteria is allowed to continue to leak under the crown, the tooth can be overcome with decay and not be solid enough to hold a new crown. At this point removal and replacement must be considered. Replacement options include a bridge or an implant.
When having a crown procedure you can expect the tooth to be anesthetized. The tooth is prepared for a crown by removing a layer of tooth structure from the top and the four sides of the tooth to leave room for the material the crown is made of. Once the tooth is adequately prepared, an impression is made for the dental laboratory to make the crown and a temporary crown is made for you to wear while the crown is being made.
During the time just following the appointment, the tooth may be slightly sensitive to very sensitive depending on how much preparation the tooth needed during the appointment. Usually an over the counter pain medication like Tylenol or Advil is sufficient, and usually for only a day or two. Once the crown is completed at the lab, you will return to the dental office. The dentist removes the temporary crown and places the new crown. At this appointment it is common to not need anesthesia, however it can be used if requested or needed.