A dental crown is a cap that is usually made of porcelain or metal. It is placed over the tooth, sometimes permanently and sometimes just as a temporary measure. Crowns can be used for a variety of purposes in dentistry. Sometimes it is for purely practical reasons, for example, if the tooth has become weakened through decay or if the tooth has lots of plaque. It may also be used for cosmetic reasons. Often, the reasons for using a crown will be cosmetic and practical. If a tooth has been broken, it will be capped using a crown. This will make the tooth look better and will restore it to something close to its original appearance. It will also make it easier for the person to eat and will get rid of any sharp edges that could cut the mouth or cause pain to the tooth itself due to damaged or exposed nerves.