Why is My Tooth Sensitive to Cold or Hot?

Is the thought of having ice cream or a cup of hot coffee upsetting?  Does brushing your teeth with cold water make you wince occasionally?  If so, you may have sensitive teeth.

Possible causes of tooth sensitivity include: 

  • Tooth decay (cavities)
  • Exposed root surface from gum recession
  • Broken down fillings
  • Gum disease
  • Worn tooth enamel
  • Fractured tooth structure

In healthy teeth, the outermost layer is enamel which is the most dense substance in your body.  The enamel layer protects the crowns of your teeth—the part above the gum line.  Below the gum line is the root of the tooth.  The outer layer of the root is cementum.  Cementum is softer (or less dense) than enamel.  When the cementum layer is exposed due to gingival recession, cold and hot can irritate the nerve. Underneath both the enamel and the cementum is dentin. The dentin is the inner tooth layer which is less dense than enamel and cementum.  The dentinal layer contains microscopic tubules (small hollow tubes). When dentin loses its protective covering of enamel or cementum these tubules allow heat and cold to reach the nerves and cells inside the tooth. The result can be hypersensitivity.

If there is a fracture line within the tooth, the nerve can be irritated when you bite down on the area that has the fracture due to the movement of the fractured tooth structure.  If a tooth has a portion missing due to it fracturing off, the nerve is not as protected and can be aggravated.

Treatment for sensitive teeth

Your dentist will recommend treatment for your sensitive tooth depending on the cause of the sensitivity.  Your dentist may suggest one of the following treatments:

  • Desensitizing toothpaste. This contains compounds that help block transmission of sensation from the tooth surface to the nerve, and usually requires several applications before the sensitivity is reduced.  It typically takes three weeks of consistent use to start to relieve sensitivity.
  • Fluoride gel. An in-office technique which strengthens tooth enamel and reduces the transmission of sensations.  Your dentist will apply the gel with a small brush to the sensitive area.
  • A crown.  A crown is used when a large portion of the tooth is missing due to decay or fracture.  Also, a dental crown is placed on a tooth that has a symptomatic fracture line to immobilize the segment that is fractured.
  • Root canal. If sensitivity is severe and persistent and is diagnosed to be irreversible, your dentist may recommend root canal therapy to treat the problem.

Poor oral hygiene contributes to many of the causative factors behind tooth sensitivity.  If plaque is not removed properly and consistently, it can lead to tooth decay and/or gum recession.  It is important that you maintain good oral hygiene habits and visit your dentist regularly.