Bridges- Crowns can also be used to create a lifelike replacement for a missing tooth. This is done with bridgework, which spans the space of the missing tooth and requires at least three crowns. Two of those crowns will be placed over healthy teeth on either side of the missing tooth; these healthy teeth are referred to as abutment teeth. The two crowned abutment teeth become supports for a third crown placed in between them; that third crown is referred to as a pontic. If more than one tooth is missing, more crowns will be needed to bridge the gap in between the abutment teeth. The number of abutment teeth necessary to replace missing teeth is influenced by the number of missing teeth, the size and length of the abutment tooth roots, the amount of bone support each abutment tooth has, as well as where in the mouth the missing tooth is located. For example, if you have three missing teeth, four abutment teeth may be necessary, thereby creating a seven-tooth bridge. Engineering and designing of the bridge requires an understanding of how to replace teeth, as well as the biology of the supporting gum and bone tissue.