Sharp pain when you bite down on a piece of food may signal a cracked tooth.

Here are common causes for tooth cracks, courtesy of the American Dental Association:

Chewing or biting foods like hard candy, nuts, or ice cubes.
Injury to the mouth.
Grinding or clenching your teeth.
Chewing unevenly.
Loss of parts of the tooth, often from fillings or wear.
Procedures like root canals that cause teeth to become brittle.
Teeth being exposed to extreme temperatures, such as from eating very hot foods or drinking ice water.

source: http://health.msn.com/

####