The best way to find out why a tooth is sensitive is to have dental professional examine you. They can look for the signs of dentin exposure, and run tests to determine what the true cause of the sensitivity is. Sometimes, the sensitivity is due to a cavity or gum disease - these can be treated to address the sensitivity. Other times, the cause of the sensitivity is because the enamel has been lost through abrasion or erosion, or the gums have receded, causing the roots to be exposed. What Can Be Done? If the sensitivity is due to a cavity, a restoration can be placed. If gum disease is the cause, the dental professional can perform a thorough cleaning of the area. However, if the cause is from dentin being exposed, then there are a number of professional and at home treatments that can be used to reduce the sensitivity. In Office Procedures: Fluoride varnish can be applied to exposed areas, strengthening the enamel and dentin Fluoride foam or gel can be placed into a mouth tray; ...