John C. Chao, D.D.S.

Research Associate Professor, University at Buffalo, SUNY
Adjunct Assistant Professor, Ostrow School of Dentistry, USC

(626) 308-9104

News & Press

Cracked Tooth Syndrome

For about three months George (not his real name) has sometimes been experiencing sharp pain in a lower right molar when he bites into something hard. For the last two weeks, the pain has been getting worse and has been become a long lasting dull pain after he chews. He likes to chew ice and knows he grinds his teeth at night. Now he has a constant ache from the tooth.

X-rays were taken of the teeth on the lower right side. No cavities or any gross abnormalities were present. A bite test was done. George was asked to bite down repeatedly on a special "bite stick" that is placed on different parts of the lower teeth. Whenever he bites on a cusp of the lower first molar, he experiences some pain. But he gets a sharp "twinge" of pain when he releases pressure on the tooth. Intraoral camera that magnifies the image forty times reveals a crack line at the same cusp. When ice is applied to the crack, there is extreme sensitivity. The diagnosis is "crack tooth syndrome." Whenever pressure is brought to bear on that cusp, the crack is minutely opened. When the pressure is released, the snap back motion introduced pain to the "pulp," or nerve of the tooth. Bacteria and oral fluids continue to flow into the pulp continuously. Eventually the tooth will probably abscess. If the patient is seen in time, and a crown is placed on the tooth, generally the situation is corrected. Sometimes the nerve will abscess even with treatment. Such cases may require root canal treatment. The sooner a cracked tooth is restored with a crown, the less the risk of root canal treatment. Needless to say, see your dentist at the first sign of biting pain.

One study indicates that 10% of patients referred for root canal treatment have cracked tooth syndrome. It is generally believed that bruxism (habit of clenching or grinding teeth) increases the risk of tooth cracking. Forces generated by clenching can be measured in hundred of pounds per square inch. Such continuous wear and tear causes enamel abrasion and "fault" lines to form in the tooth structure. This predisposes the tooth to fracture when the patient bites down on something hard and sharp.

Therefore to avoid crack tooth syndrome, bruxism should be controlled. This can be accomplished by the use of a bite guard. This is a plastic device, shaped like a retainer that the patient wears at night and during the day, if possible. This is will help control the clenching, grinding habit. Of course, avoid hard, crunchy foods as much as possible, especially if you have already experienced fracture of teeth or crack tooth syndrome.

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