The causes of soreness when teeth bite into hard things are deeper hidden cracks on the tooth surface, deeper cavities in the crown, habitual grinding or clenching of teeth, and different degrees of loosening of tooth roots, etc., as follows: 1. deeper hidden cracks on the tooth surface: stimulation of hard objects can be transmitted along the cracks, leading to soreness in the tooth pulp; 2. deeper cavities in the crown: large pieces of food can squeeze the pulp cavity below, leading to pain; 3. suffering from night grinding or clenching teeth and other habits: heavy wear and enamel loss on the tooth surface, exposing the weak dentin, chewing hard objects can stimulate the sensitive reaction of the pulp; 4, different degrees of loosening of the tooth root: heavy resorption of the alveolar bone and gum recession cause different degrees of loosening of the tooth root, chewing hard objects can pull the periodontal membrane fibers around the tooth root, resulting in soreness, pain, and even bleeding.