The main reasons for sore roots are as follows: First, patients suffering from periodontitis, periodontitis due to long-term chronic inflammation of periodontal soft tissues, resulting in the resorption of alveolar bone, leading to gum atrophy and root exposure. When the roots of the teeth are exposed in the mouth, it will cause the symptoms of dentin hypersensitivity. Once you eat cool, hot, sour, sweet or hot foods, your teeth will feel sour at the roots. Secondly, due to wedge-shaped defect in the neck of the tooth, wedge-shaped defect is caused by the bite stress concentration of the tooth, or incorrect method and strength of brushing, it will lead to the formation of a wedge-shaped groove in the root of the tooth, resulting in a sour and soft feeling of the tooth. Thirdly, the sourness of tooth root may also be due to the caries of tooth root, when the tooth root is exposed in the mouth, because the surface of tooth root is not smooth, it is easy to accumulate bacteria and food residue, and it is very easy to induce the root surface caries of tooth. The root surface caries will lead to the loss of hard tissue of teeth and cause the feeling of soreness of tooth roots.