A dental crown is a tooth shaped "cap" that is placed over a tooth to cover the tooth to restore its shape and size, strength, and improve its appearance.

A bridge spans a space where one or more teeth have been lost in the dental arch. The teeth on either end of the gap are crowned, and are referred to as abutments. The false teeth in a bridge that join the abutments are referred to as pontics. 

Crowns and bridge may be made of metal, porcelain, or newer restorative materials like metal free ceramics( Zirconia, Ultratranslucent, Bruxzir & Robust, Ivoclar Zenostar, 3M Lava Essential). 

The biggest disadvantage with dental bridge is the grinding down of healthy neighbouring teeth to support missing teeth. But you can save healthy neighbouring teeth by dental implants.