Why can’t I just get a filling? This is a frequently asked question in the dental chair when a patient is advised that they should have a tooth crowned. There are many possible answers to this question.

The longevity of a filling whether it be a composite (white filling) or amalgam (silver filling) depends on the strength and integrity of the remaining tooth structure. Another consideration is that large fillings need to be shaped directly in the mouth. This placement and shaping of filling in the mouth can be extremely difficult for large fillings and result in gaps between teeth causing food impaction. A crown which is also referred to as a cap is a dental restoration which completely covers the tooth they are cemented over. They are fabricated outside of the mouth allowing them to be shaped and fitted correctly. They protect remaining teeth structure from fracture.

Instances in which you may need a crown include a severely broken down or decayed tooth, a cracked tooth or a tooth with a restoration which is too large to adequately protect the remaining tooth structure. Teeth which are severely broken down or decayed do not have enough remaining tooth structure to allow a filling to stay in place or even if a filling could be placed would not provide protection for the remaining tooth structure. When the extent of the decay is large after the removal of the decay often there are just thin walls left. Biting and chewing could cause these walls to fracture off. The placement of a crown in this instance will prevent fracture of remaining tooth structure. If a crown is not placed the remaining tooth structure could fracture in such a way that the tooth could not be saved and would require it to be extracted or pulled.

Cracked teeth need crowns to provide full coverage or a cap to prevent cracks from spreading and splitting the tooth. Crowns prescribed for these reason will restore the form and functionality of your teeth. A tooth receiving a crown will need to have all decay removed. This usually requires that any existing filling be removed. After the removal of all decay the tooth receives a new filling which provides a sound substrate for the crown. This is called a core buildup. At this point the dentist will prepare your tooth to receive a crown by removing a thin layer of tooth structure all around the tooth and also from the top. This gives us room for the metal and/or porcelain contained in a crown. The dentist will then the make an impression of you upper and lower teeth. This allows the lab technician to have an identical copy of your teeth and will use that model to fabricate your new crown. It usually takes two weeks to get your new crown. When you leave the dental office you will have a temporary crown covering you tooth until the new crown is ready to be cemented into place.

It is important to remember that the majority of crowns are needed to fix severely broken down or decayed teeth, a cracked tooth or a tooth with a restoration which is too large to adequately protect the remaining tooth structure. In these cases the nerve of the tooth has been under stress from previous decay and mechanical forces. Sometimes crowning the tooth puts additional stress on the nerve of the tooth from which it cannot recover and pain develops. In these cases a root canal must be performed prior to cementing the final crown. On average, dental crowns last between 5 and 15 years. How long the crown last will depend on how well you take care of your teeth. To prevent damaging or fracturing the crown, habits such as grinding or clenching, chewing ice should be avoided. Remember that simply because a tooth is crowned does not mean the underlying tooth is protected from decay or gum disease. The crown itself cannot decay, but decay can start where the edge of the crown joins the tooth. Therefore, continue to follow good oral hygiene practices, including brushing your teeth at least twice a day and flossing once a day-especially around the crown area where the gum meets the tooth.

Written by Carlos Vallecillo, DDS and Rossana Menna, DDS
www.monalisadental.com