Crowns are placed over a tooth when a large portion of the tooth is lost to decay or has broken off. Usually when a filling is more than half of the size of the tooth, the tooth is weakened. If the filling would comprise a significant portion of the tooth, often the tooth can fracture under the stresses of chewing and therefore, placing a crown over the tooth protects the chewing surface and prevents that from happening. Crowns that are white are made of porcelain and are usually placed in areas of esthetic concern. Gold crowns might be placed in the molar region or when there is heavy grinding that might damage the opposing teeth.