Crowns provide strength and protection for the weakened tooth. A broken or cracked tooth is a far more serious matter and much more difficult to treat. Crowns prevent this, as well as making for a nice smile. It takes two appointments to restore a tooth with a crown. In the first appointment, any decay is removed from the tooth and it is shaped to accept the crown. Then an impression is made of the tooth for use in fabricating a crown. Between the two visits the crown is made, usually of high-strength porcelain over noble metal, or all ceramic material. During this time a temporary crown is worn. In the second visit this temporary is removed. Then the permanent crown is adjusted as needed and then cemented in place.