Bridges are made to restore gaps between natural teeth. They can be held in place by a crowned adjacent tooth, or they can be stuck onto the adjacent tooth by a metal wing, with a special adhesive. Sometimes bridges are held in place on either side of the gap (conventional), sometimes on just one side (cantilever); it depends on the size of the gap and how the teeth function. Bridges can look very good, but sometimes the bridges that are stuck on with a metal wing darken the adjacent tooth a little. They are, however, much more conservative of tooth structure than if the adjacent tooth is crowned in order to hold the bridge.