Whether deep caries has rotted into the nerve can be determined by clinical manifestations, pulp vitality test and imaging examination. 1. Clinical manifestations: If deep caries rots into the nerve, the patient will experience pain, such as temperature stimulation pain, radiating pain, night pain, and when the pain is severe, it can radiate to half of the head and face, and even can’t sleep at night. 2. Pulp vitality test: Pulp vitality test is divided into temperature test and electric power test, through the pulp vitality test, we can understand the degree of tooth response to the electric current, so as to judge whether the deep caries has rotted to the nerve. 3. Imaging examination: Clinical judgment can be made through imaging examination, such as taking oral X-rays. If it is found that the pulp angle is connected with the carious tooth or the pulp cavity is connected with the carious tooth, it can be confirmed that the deep caries has rotted to the nerve of the tooth. When the patient’s teeth show the above symptoms, he/she should consult the doctor in time and give targeted treatment or therapy under the doctor’s guidance.