Dental Crowns: A crown, also known as "cap", is a type of dental restoration which completely caps or encircles a tooth or dental implant. Crowns are often needed when a large cavity threatens the ongoing health of a tooth, to protect a cracked tooth, restore functionality of a tooth with excessive decay or replace a pre-existing crown. Crowns are often used to improve the strength or appearance of teeth, as to encase a needy tooth with a custom-designed material. They are typically bonded to the tooth using a dental cement. Crowns can be made from many materials, which are usually fabricated using indirect methods. Those materials can be: metal fused to porcelain, full porcelain and zirconium. The purpose of a dental crown is to encase a needy tooth with a custom-designed material.