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Dental Crowns and Bridges
Dental crowns, which are also referred to as caps, are dental restorations which completely cover the tooth they are cemented over. 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. Crowns prescribed for these reason will restore the form and functionality of your teeth. Teeth are also crowned for cosmetic reasons to allow for a more pleasing appearance or to straighten teeth without undergoing orthodontic treatment (braces). Crowns can be joined together to replace missing teeth forming a bridge. Crowns are also placed over implants to replace missing teeth without sacrificing adjacent tooth structure.
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 we 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. Then we take an impression of your 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 your tooth until the new crown is ready to be cemented into place.
Crowns can be made of porcelain, metal or a combination of metal and porcelain. Metals used in crowns include gold alloy, other alloys (for example, palladium) or a base-metal alloy (for example, nickel or chromium). Advantages of metal crowns include less removal of tooth structure because metal is strong in thin thicknesses. They are also less abrasive to opposing teeth and withstand biting and chewing forces well. They main disadvantage for most people is the color of the metal. They are however a good choice for molars in the posterior of the mouth. Porcelain-fused-to-metal dental crowns or PFM’s are a combination of metal and porcelain. The porcelain covering the metal can be color matched to your adjacent teeth (unlike the metallic crowns). The disadvantages of PFM’s is that they are more likely to wear opposing teeth, the porcelain is more susceptible to chipping and fracture and sometimes the metal shows at the gum line although that can be avoided by having a porcelain shoulder at the gum line. The advantage of the PFM is the beauty and naturalness of the porcelain combined with the strength of the metal. All-ceramic or all-porcelain dental crowns provide the best natural color match than any other crown type since they have no metal substructure and current ceramic technology has made them as strong or stronger that PFM crowns. All-ceramic crowns are esthetically beautiful and are used in all areas of the mouth.
It is important to remember that the majority of crowns are needed to fix 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. 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 can not 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, clenching, or 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.