Updated July 03, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

A broken or cracked tooth can occur for a number of reasons. The most common causes for a tooth to fracture or break are:

• Chewing and biting into hard food
• Biting on hard objects, such as a pen cap or pencil
• Brittle tooth structure caused by root canal therapy
• Old restorations that have begun to separate from the tooth's structure
• Clenching or grinding of the teeth
• Trauma to the face and mouth

When a tooth breaks or cracks, there is a good chance that the nerve of the tooth will be exposed.

The one exception is when that tooth has already had root canal performed on it, as the root is removed during the procedure. An exposed nerve is hyper-sensitive to temperature, especially cold, and may cause pain and discomfort if not treated immediately.
What to Do: Gently bite down on a fresh piece of gauze, and avoid eating or drinking cold foods and beverages until the tooth has been repaired by your dentist (which should be as soon as you can get an appointment).
If only part of the tooth has broken off, you may wish to collect the broken piece and take it with you when you see the dentist. Even though she will not be able to use the broken piece of tooth to restore it, she may want to see if the piece that broke was enamel or part of a filling.

When a tooth cracks and the entire tooth remains in the mouth, avoid eating or biting down on the tooth. A cracked tooth may or may not involve the root, so every effort to avoid contact with the tooth should be made in order to prevent the tooth from cracking further and potentially causing a root fracture.

See your dentist as soon as possible in order to prevent further damage from occurring to the tooth and gum tissues.

<sub>Sources:

The American Dental Association. Do You Have a Cracked Tooth? http://www.ada.org/sections/publicResources/pdfs/patient_25.pdf Accessed: July 19, 2010</sub>