Crowns are restorations made of metal, porcelain or both, placed over a compromised tooth for long term strength. A tooth may be compromised in strength if it has a large filling, with or without an underlying root canal, leaving the remaining thinner tooth structure prone to fracture. The crown is made to fully cover the tooth from all sides giving it support and preventing any fracture from developing. A crown is also used to restore a dental implant. Crowns can be made to look and feel very natural.