- The anatomy of a tooth can be divided into two basic parts — the root and the crown.
- In a person with healthy gums and underlying bone, the root of the tooth is covered by the gums and bone.
- The crown is the part of the tooth that is visible in the mouth, above the gum line on lower teeth, and below the gum line on upper teeth.
- A cemented restoration that partially or completely covers the outside of the tooth is referred to as a dental crown or just crown.
When is a dental crown needed?
There are a variety of situations that require a tooth to be restored with a dental crown. The following are the most common:
Large filling: When a tooth has decay or fracture that involves half the width of the tooth or more, it needs to be covered with a crown. This is because the remaining tooth around the large filling is so weak that it is prone to fracture. Sometimes a large filling that has been in the mouth for a while will need to be replaced with a crown because the tooth shows signs of stress and cracks around the filling.
Root canal: Root canal treatment leaves the tooth hollowed out and predisposes the remaining tooth to crack. So, a posterior tooth that has had a root canal almost always needs to be restored with a crown immediately to prevent it from fracturing.
Cracked tooth syndrome: This is a condition whereby a patient has fractures inside a tooth that cause pain when it is chewed on a certain way. Chewing produces stress on fracture lines that make it feel like it is splitting apart. A crown will hold the tooth together and redistribute the stress evenly throughout the tooth, eliminating the pain in most instances. In these situations, it is best to leave a temporary crown on for a while to make sure the pain goes away and the tooth doesn’t require a root canal.
Broken cusps: Cusps frequently break off of teeth due to trauma or large existing fillings. Since the cusps are the part of the tooth that takes the most stress during chewing, they need to be completely covered or the tooth or filling will keep fracturing. Sometimes the tooth breaks all the way to the bone, and a crown lengthening procedure is necessary. This means the bone and gums need to be trimmed down below the edge of the fractured part of the tooth so the margin of the crown can be placed on a healthy, strong tooth structure.
Excessive wear of teeth: If a person has a habit of grinding their teeth, the teeth will become shorter over time. The teeth can also wear away due to acid erosion caused by gastrointestinal acid reflux (GERD), bulimia, or an acidic diet. Sometimes, the enamel will wear away completely, leaving small, soft teeth. Over time, the bite can collapse and the only way of restoring the teeth to normal size is by covering the teeth with crowns.
Undesirable appearance of teeth: Teeth that have an unacceptable appearance due to color, shape, or spaces between teeth can be made to look very natural and beautiful with crowns.
Other: Crowns are placed on dental implants to restore spaces left from missing teeth. Another way of filling these spaces is with dental bridges which are made from crowns on the teeth next to the spaces attached to fake teeth in the middle. If teeth are loose, crowns can be placed on multiple teeth and splinted together to provide more stability.
What is the procedure for getting a dental crown?
The dental crown procedure first involves numbing the tooth with local anesthesia. If the tooth has been fractured or had root canal treatment, it will first need to have a buildup — a filling that restores enough of the tooth for the crown to adhere onto. Then the dimensions of the tooth are modified to make room for the crown, and an impression is made utilizing a digital scanner. Dr. Lanza will then determine the shade of the patient’s teeth using a shade guide or take pictures of the teeth to help the lab technician fabricate a crown(s) that will match the rest of the patient’s tooth/teeth. A temporary crown is made from a resin or acrylic material using a molding of the original tooth. This temporary crown is cemented with temporary cement so that it can come off easily once the permanent crown is ready.
One or two weeks after a temporary crown, the patient returns for a second visit. During this visit, the tooth may or may not need to be numbed again and the temporary crown is removed. The permanent crown is placed on the tooth and inspected for acceptable fit, bite, and smooth margins. After any necessary adjustments have been performed, the crown is cemented with permanent cement.