Crowns and most bridges are fixed prosthetic devices
A crown is used to entirely cover or "cap" a damaged tooth. Besides strengthening a damaged tooth, a crown can be used to improve its appearance, shape or alignment. A crown can also be placed on top of an implant to provide a tooth-like shape and structure for function.
A bridge may be recommended if you're missing one or more 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 commonly used to replace one or more missing teeth