Crowns are designed to protect a tooth from breaking by covering the tooth on four sides, top, back, front, and two sides. Crowns can be made from metal (precious, semiprecious, non-precious), porcelain fused to metal, porcelain alumina, porcelain zirconia, dilithium silicate porcelain, plastic, or all feldspathic porcelain. A crown is made by removing tooth structure to compensate for the thickness of the crown. The thicker the crown, the more removal of tooth. In this way the crown will be about the same size as the original tooth.
A fixed bridge is a replacement for missing teeth. It consists of an attachment of one or more fake teeth attached to the teeth next to the space. Therefore, it requires at least one tooth on each side of the space. It is characterized in several ways; the number of teeth involved, the design, and the materials used.
