Crowns are needed when a large amount of tooth structure has been damaged by trauma or decay. They are made of porcelain or porcelain over metal, and cover the entire tooth surface. With advances in materials and techniques, they can give you the strength, beauty and translucency of a natural tooth.
Bridges are restorations that are fabricated to replace a missing tooth by 'bridging' over the open space. A bridge consists of two or more crowns on natural teeth or surgically placed dental implants, that are attached to an artificial tooth called a pontic, replacing the missing tooth. One or more teeth can be replaced with a single bridge.