Numbness of the tooth after root canal treatment may be caused by inferior alveolar nerve damage, which can cause numbness in the corresponding area when the inferior alveolar is damaged. The factors leading to inferior alveolar nerve injury are chemical irritation and mechanical irritation. 1. Chemical irritants: the filling materials used in root canal treatment to fill the root canal beyond the apical foramen to reach the periapical tissues are called overfilling, and the filling materials are neurotoxic, which may cause damage to the inferior alveolar nerve when they enter the mandibular canal. 2. Mechanical stimulation factors: filling materials or surgical instruments exceed the apical foramen, generating mechanical pressure on the inferior alveolar nerve and causing damage. There may be other reasons for the numbness of the tooth after root canal treatment, so it is recommended to go to the hospital in time.