#sensitive tooth /animated 3 f/s Teeth are usually sensitive because there is some {dentine} exposed in the mouth. This can be the result of decay & development of a cavity, or as a result of gum recession, exposing the tooth root. In case of an exposed root as a result of gum disease, toothpastes for treatment of sensitive teeth can be useful. If you suffer from sensitive teeth, you should see your dentist for advice.