When a tooth is cracked, decayed, or damaged, a dental crown may need to be fitted onto the tooth. A dental crown is a permanent covering that fits over the original tooth. Crowns can be made of porcelain, gold or a combination of both materials. Porcelain crowns typically have the most realistic appearance, although they tend to be less durable than other materials when used on your back molars. Dental crowns can whiten, reshape and realign existing teeth, adding to a healthy and vibrant smile.