The specific reasons are as follows: 1.Dental jaw abrasion: When chewing hard food for a long time, resulting in heavy abrasion on the jaw surface of teeth, sweet and sour stimulation can be transmitted to the pulp along the end of the exposed dentin tubules, causing pain. 2.Dental neck defect: When brushing the teeth horizontally with a hard toothbrush, resulting in wedge-shaped defect on the neck of teeth, the dentin is thin, and sweet food can stimulate the pulp and cause pain. 3.Cavity in crown: When there is deep cavity in the crown, the bottom of the cavity is close to the pulpal angle, sweet food stays in the cavity, and acid is produced under the fermentation of bacteria, which causes the sensitive reaction of pulp. 4.Periodontal disease: When suffering from periodontal disease, the root surface of the tooth is exposed in the mouth after periodontal atrophy, and the thinner dentin will produce pain when encountering sweet food.