There are a number of reasons why a crown might be recommended these might include decay, accidents, missing teeth and for cosmetic reasons.
When a tooth is missing crowns may be placed on teeth either side to support an artificial replacement to fill the gap, this is known as a bridge.
Crowns also provide a way of improving the appearance of crooked or misshaped teeth. Once the dentist has prepared the tooth/teeth impressions of your mouth will be taken, and then the crown or bridge will be made by a skilled technician at a dental labortatory. The crown or bridge will match your other teeth and fit perfectly. Modern crown materials can combine excellent appearence with great strength.
There are several materials available which your dentist will discuss with you.