What is a crown in dentistry?
A crown is a cap that is shaped like a tooth, which covers and restores the weak tooth structure.
When does a tooth need a crown?
When the tooth structure is extreemly weak and there is possibility to break. For instance when a tooth has root canal treatment or when a tooth has very large filling.
How many types of crowns do we have?
Crowns can be made of different materials.
In a full metal crown, the material can be gold or different type of metals.
Also there is porcelain fused to a metal ( PFM) crown, where the core of the crown is made from metal and the outer part of the crown is made out of porcelain. This way the crown looks like a natural tooth while the metal core supports the tooth.
In zirconia crown, the crown looks like a natural tooth and it is made only of zirconia.
There are other types of materials that can be used to make crowns, but the general idea is to cover the weak tooth structure to support the remaining mass. However, crowns can also improve tooth appearance.
The first step to make a crown is to:
1- Make an impression before doing anything to the tooth. This impression will be used to make a temporary crown and is called a preliminary impression.
2- The dentist will start reducing from all over the tooth structure, to make enough space to put the crown on. This reduction can vary in different parts of the tooth. For instance, the reduction on the biting side of the tooth should be slightly deeper to make a strong biting surface.
3- Taking an impression from the prepared tooth. This impression is called the final impression.
4- Final impressions will be sent to the laboratory with detailed instructions for the crown to be made.
5- Temporary crowns will be made from the preliminary impressions (first impression), and they will be cemented in place.
6- When the permanent crown is made, it will be cemented with permanent cement in place. This step will be done after removing the temporary crown and polishing the tooth to make sure there is no temporary cement left on the tooth. Also before cementing, we will make sure that the crown fits well and that the contacts and the bite is correct.
Dr. Roushanak Shafaghi
Images from Google.