When the tooth is broken & filling does not solve the problem, tooth is covered with crown to restore its normal function & to strengthen & improve the appearance.
Crowns are also used to cover badly shaped or doscolored tooth.
When one or more teeth are missing they can be replaced by bridge by taking support from adjacent teeth. It is most acceptable & natural choice to fill the space in mouth left by missing tooth.
IF LEFT UNFILLED,
This space can cause the surrounding teeth to drift out of position & can cause tooth caries & gum disease, that can cause future tooth loss.