Bridges are commonly used to replace one or more missing teeth. Gaps left by missing teeth eventually cause the remaining teeth to rotate or shift into the empty spaces, resulting in a bad bite. Bridges are cemented to the natural teeth or implants surrounding the empty space. Bridges are made up of two or more crowns for the teeth on either side of the gap. These teeth, called abutments, serve as anchors for the bridge. A replacement tooth, called a pontic, is attached to the crowns that cover the abutments. Bridges can be made from gold, alloys, porcelain, or a combination of these materials. Bridges are cemented onto existing teeth or implants, and can only be removed by a dentist.