Teeth feeling cool and sensitive usually indicate the following conditions: i. Teeth have symptoms of dentin hypersensitivity. The appearance of dentin allergy, may be the patient’s root exposure, gum recession caused by the need for patients to choose desensitizing toothpaste, desensitization treatment. Second, the tooth has a defect and the defect site is close to the nerve, the symptoms of sensitivity, in this case, it is recommended that patients go to the regular hospital stomatology department as soon as possible, especially the endodontics department for defect filling treatment, after filling, tooth sensitivity symptoms will disappear immediately.