Crowns (or Caps) are custom-made restorations that cover the entire tooth restoring it to its original shape and size.  They can be all metal, porcelain fused to metal, or all porcelain.  Dental crowns protect and strengthen teeth that cannot be restored with regular fillings.  They are ideal for teeth that have large, fractured or broken fillings, as well as those that are badly decayed.  A Crown is usually (but not always) required after a Root Canal has been performed, because Root Canals render teeth more brittle and prone to fracture.  Crowns are a two-visit procedure: the tooth is prepared or shaped, a temporary crown is fabricated, and an impression is taken and sent to the lab for fabrication.  A couple of weeks later, the temporary crown is removed and the permanent Crown is fit and cemented.