Having sensitive teeth can mean anything from getting a mild twinge to having severe discomfort that can continue for several hours. The part of the tooth we can see is covered by a layer of enamel that protects the softer dentine underneath. If the dentine is exposed, a tooth can become sensitive.
This usually happens where the tooth and the gum meet and the enamel layer is much thinner. There are many different causes of sensitivity ranging from toothbrush abrasion, gum recession, tooth erosion to tooth grinding. You may find that hot and cold foods bring on sensitivity. It is important to have your dentist or oral hygienist determine and treat the cause of the sensitivity.