2. Gum diseaseAnother major cause that can result in the gum tissue shrinking back from the teeth is gum disease (periodontal disease). As plaque or tartar builds up due to inadequate brushing or flossing, gingivitis or inflammation of the gums can occur. Over time, gingivitis can lead to gum recession which exposes the root of the teeth and causes sensitivity. You can spot gum inflammation rather easily -- swelling and soreness of the gums, and bleeding while you're brushing or flossing.
What to do: Get into the habit of brushing at least twice a day, and floss your teeth daily.
3. Dental erosionSometimes, tooth sensitivity may also signal dental erosion -- which is just a fancy name for tooth decay. In early tooth decay, the outer enamel is worn away, exposing the dentine underneath which can lead to sensitivity.
What to do: If you suspect you have a cavity, go let your dentist take a look.
4. Tooth grindingIf you have a habit of clenching and grinding your teeth together (bruxism), the constant friction can cause the enamel of the teeth to be worn away, making the teeth sensitive. Bruxism is often related to stress, and most often done unconsciously at night during sleep.
What to do: Break the habit now. If you can't, talk to your dentist about the possibility of having a mouthguard made to wear at night.