The reasons for tooth pain caused by cold water brushing include the following: 1, when suffering from enamel hypoplasia or poor mineralization, substantial defects appear on the tooth surface, and cold water stimulation can easily reach the pulp through the tooth tissue, thus causing pain; 2, when food fibers are often embedded between the two teeth, vertical resorption of the alveolar bone can occur, resulting in root exposure, which cannot tolerate cold stimulation; 3, when large pieces of dental calculus press the alveolar bone atrophy, resulting in exposure of the root bifurcation area when the dentin tubules are more developed in this area and close to the pulp chamber. The mechanical stimulation and cold stimulation during brushing can cause pulpal soreness; 4. When a wedge-shaped defect is formed in the neck of the tooth, cold water can stimulate the pulpal sensitivity reaction and produce pain and soreness.