Patients with sensitive teeth may experience pain or discomfort when their teeth are exposed to certain stimuli, such as cold or hot drinks and foods, cold air and sweet foods. At least 45 million adults in the United States have sensitive teeth, according to the Academy of General Dentistry.

There are two major types of sensitivity that affect the teeth: dentinal sensitivity and pulpal sensitivity.

Dentinal sensitivity results when the middle layer of the tooth (dentin) becomes exposed. Normally, the dentin of a tooth is housed in an outer protective layer that divides into two parts. A layer of hard enamel protects the top of the tooth (crown) while a layer of cementum protects the part of the tooth under the gums (root).

When the enamel or cementum wears away, it leaves dentin exposed. Tiny hollow tubes and canals (tubules) run through the dentin, and each tubule contains a nerve branch that connects to the pulp at the center of the tooth. When these tubules are exposed to certain stimuli, they stimulate the nerves in the tooth and cause pain.  

Pulpal sensitivity occurs when the pulp of the tooth reacts to stimuli, causing pain. The pulp is the mass of blood vessels and nerves at the center of a tooth. Frequently, pulpal sensitivity affects only one tooth. The irritation to the pulp does not necessarily cause permanent damage to the pulp itself.

People with sensitive teeth often feel pain when they eat sweets or cold food or drinks. Patients also may feel pain when chewing, breathing in through the mouth or touching the teeth. Less commonly, hot foods or drinks may cause pain.

In some cases, patients feel pain that lasts for just a few seconds before fading. Sensitivity that lingers after the stimulus is gone may indicate the need for a root canal treatment. Pain that occurs when consuming hot food or drinks may indicate that the nerve in the tooth is dying, a condition that may also require root canal treatment.

Patients with tooth sensitivity are encouraged to speak to their dentist about treatment options. The prognosis for patients with sensitive teeth varies. Some people experience sensitivity that lasts for only a short period before it subsides. Others may experience sensitivity that lasts throughout their lifetimes.

Sometimes tooth sensitivity may indicate other problems. Patients should contact their dentist immediately if any of the following occur:

• Sensitivity occurs long after stimulus is removed. If sensitivity lasts for a length of time (e.g., for more than just several seconds or a minute or two) after exposure to stimuli, it may indicate damage to the pulp of the tooth.
  
  
• Sensitivity persists despite treatment. If tooth sensitivity does not decrease after two to four weeks of desensitizing treatment (e.g., regular use of desensitizing toothpaste), patients should consult their dentist. Persistent sensitivity that does not respond to desensitizing agents may indicate another problem or the need for certain types of treatment (e.g., gum graft, root canal treatment).
  
  
• A single tooth is sensitive. This may indicate tooth decay or infection that has damaged the pulp of the tooth. Treatment by a dentist is necessary. Even if sensitivity subsides, treatment may be necessary to prevent the spread of infection.
  
  
• Sensitivity occurs upon biting or chewing. This may indicate a crack or fracture in a tooth. A dentist can determine the extent of the break and whether the pulp of the tooth has been damaged.
  
  
• Sensitivity is accompanied by signs of disease or decay. If the gums change color, or there is an obvious cavity, crack or fracture in the tooth or dental restorations, it may indicate a condition that needs to be treated by a dentist.