A dental crown is a custom-made, fixed restoration. It is placed over a prepared natural tooth. It is also used in implant cases to replace missing teeth. A crown may be needed when a cavity threatens the tooth. It is typically bonded to the tooth by dental adhesive.

Dental bridges are the arrangements to bridge the gap created by one or more missing teeth.
A bridge is created by two or more crowns that sit on anchoring teeth(called abutment teeth) and a false tooth/teeth in between.
These false teeth are called pontics and can be made generally from gold, alloys, porcelain, or a combination of these materials.
Usually, dental bridges are supported with the help of natural teeth or implants.