Introduction: the needle fracture during the inferior alveolar nerve block is not a common accident, but when it occurs can cause great inconvenience to the professional and patient, because the surgical removal should only be performed without risk of sequelae to the patient. Aim: relate a case of broken dental needle during inferior alveolar nerve block and the needle fragment dislocation to the skull base becoming impossible its surgical removal. Described preventive procedures to avoid that complication with anatomical considerations related to the inferior alveolar nerve block. Case report: a young female, 18 years old required care after fracture of the dental needle during inferior alveolar nerve anesthesia. She was submitted to CT scan that determined the impossibility of surgical removal of the fragment because it has migrated to the skull base becoming close to vital anatomic structures because its could produce irreparable sequelae such loss of tongue sensation and movement of the lip. A conservative treatment was offered. Conclusions: surgical removal of its instrument should be correctly evaluated to avoided irreparable sequelae to the patient. The knowledge of anatomical structures in the pterigomandibular region may reduce the risk of injury to nerves and another structures and prevent further complications.