As a dentist, I am asked this question frequently. This happens both in the office as well as on my days off at the grocery store, a party, or a family gathering. People who have not had much experience with crowns are often confused as to what a crown is as well as whether or not it is really necessary.
A dental crown is a cap that covers your entire tooth, fabricated outside of your mouth and cemented or bonded onto the tooth. The tooth must first be prepared for the crown, basically, removing 1-2 mm in all dimensions to make room for the thickness of the crown material. That way, once the crown has been cemented, it restores the tooth to its original size, shape, and function. Crowns can be made from metal, a ceramic material, or combination (porcelain fused to metal). Here at Innovate dental, in 90% of cases, we use e.max crowns, which are made from an all-ceramic material called Lithium Disilicate.
There are several reasons a crown can be necessary in your mouth. One of the major reasons we see on a daily basis are large silver (Amalgam) fillings that are failing, or fractures in your tooth. For better or worse, these types of fillings are very hard. Natural teeth have some elasticity and flexure when you bite down. Unfortunately, Amalgam fillings do not flex with your teeth. In addition, these fillings are often positioned between the cusps (pointed parts of your teeth), and when you bite down, the filling acts like a wedge that drives these cusps apart. As a result, fracture lines are often visible in the tooth. If left untreated, this will eventually result in one or several of these cusps fracturing off. Depending on the nature of the fracture, the tooth could need a root canal (in addition to a crown) or even an extraction. By preventively covering this same tooth with a crown, the tooth is held together from all dimensions which allows the forces on the tooth to be directed down the root to dissipate normally.
Another reason we may suggest a crown is extensive tooth decay. Composite fillings (also known as white, or tooth colored fillings), are a great way of removing decay and restoring teeth in most cases. However, when a cavity becomes too large, restoring the tooth with a filling alone leaves the tooth vulnerable to fracture. As a general rule, if the restoration requires replacing a cusp (or multiple cusps), or if the cavity preparation occupies more than half of the distance between the cusps of the tooth, a crown is indicated.
A final reason for a crown is if a tooth has had a root canal. Root canals are procedures that involve removing the nerve from the root of the tooth. During this process, along with the nerve, the blood supply is also removed from the root of the tooth and this space is replaced with an inert filling material called Gutta Percha. When the blood supply is taken from the tooth, the tooth dries out over time and becomes brittle. This, combined with the fact that the tooth is now essentially hollow, increases the risk of tooth fracture. A crown is fabricated in order to prevent fracture of this weakened tooth.
To conclude, dental crowns are the treatment of choice in many clinical situations. If you have any questions about crowns or any dental treatment, please feel free to ask your dentist. At Innovate Dental, we strive to educate our patients and allow them to make informed decisions about recommended dental treatment.
–Ryan Harrington DMD