A crown is a complete covering generally made of porcelain, metal, or ceramic material. It substitutes the enamel layer of the tooth. It communes on top of a healthy rooted tooth that requires protection and strengthening. A bridge is a device that uses two crowns to fill in a gap in the smile formed from a missing or broken tooth. The crowns cover the two neighbouring teeth, also known as abutments. The centre of the bridge called a pontic is a false tooth designed to fit in with the rest of the smile.