The outermost layer of a good natural tooth is the enamel, which is not only hard but also an excellent insulator, so a good tooth will not feel uncomfortable. First of all, the most common condition is dentin hypersensitivity, when the tooth encounters hot or cold temperatures (below 10 degrees and above 60 degrees) there will be a sore or painful uncomfortable feeling. When the enamel is damaged, the more sensitive inner part of the dentin comes into contact with the outside world, making the teeth more sensitive to changes in temperature. As the temperature of the oral environment changes, it sends sensitive messages to the body’s dental nerve, manifesting as soreness and weakness and inability to bite. Desensitizing toothpaste and mouthwash can be used, and if necessary, desensitizing treatment can be done at the dental clinic. Secondly, the more common cause is the wedge-shaped loss of the neck of the teeth. This is due to improper brushing, especially the horizontal brushing of the buccal side of the teeth, coupled with hard-bristled toothbrushes or coarser particles of tooth powder, which will accumulate over decades, resulting in a wedge-shaped defect in the neck of the teeth, the principle is also the thinning of the enamel layer, so that the more sensitive dentin is exposed and exposed to the external environment due to the symptoms of sensitivity. In daily outpatient clinics, about 80% or more of patients have this kind of tooth cervical abrasion to a greater or lesser extent. Although it is different from the cause of tooth decay, the mechanism of causing soreness and softness is the same. The wedge defect can be filled and desensitization treatment can be done at the dental clinic. Finally, it may also be caused by long-term gingivitis or periodontal disease that leads to gum recession or tooth loosening. After gum recession, the neck of the tooth is more sensitive and will have the discomfort of hot and cold stimulation, and periodontal disease will have the feeling of soreness and softness due to tooth loosening and weakness of tooth bite. You can go to the hospital for periodontal cleaning, and use desensitizing toothpaste, mouthwash, etc. In addition, about some people will have short temporary sensitivity after scaling or periodontal surgery. This is due to the loss of the thicker calculus barrier after root planing surgery and the relative exposure of dentin.