Crowning of teeth are indicated when teeth need to be restored to their normal shape in order to function correctly and to improve aesthetics. Teeth are crowned when broken, decayed, old and large restorations need replacing, sometimes in root canal treated teeth and if severely worn down.
Different materials can be used, for example, porcelain fused to metal. Personally, I have a preference for using metal free restorations like zirconium or a porcelain type material called E-Max.
Bridges are used to replace missing teeth, but the more modern approach is using implants, if possible.