The causes of sore and soft teeth are periodontitis, wedge-shaped defects, etc., as follows: 1, periodontitis: patients with advanced periodontitis, there will be varying degrees of alveolar bone resorption and gum atrophy, after the resorption of alveolar bone and gum atrophy, it will cause multiple teeth in the mouth root exposure, once the root is exposed in the mouth will appear to eat sweet and sour food, causing the symptoms of sore and soft teeth; 2, wedge-shaped defects Wedge-shaped defect is due to improper brushing method and brushing strength, resulting in the emergence of wedge-shaped grooves of different depths in the neck of teeth, thus causing the exposure of dentin, resulting in dentin hypersensitivity, for this case, you need to go to the hospital for filling treatment of cervical defects, which can quickly relieve the symptoms; 3, other: it may also be caused by hidden cracks in the teeth or dental caries.