There are many reasons why the numbness of teeth lasts for several months, and the common reasons are trauma, tumor, and extraction injury. 1. Trauma: the periodontal membrane is damaged due to impact or knocking on the teeth, which causes numbness of the teeth and lasts for several months. 2. Tumor: if the numbness lasts for several months, it is necessary to exclude whether the tumor presses on the alveolar bone, which leads to the compression of the nerve, making the teeth feel numb. You need to go to the doctor for radiographs to rule out the problem. 3. Damage caused by tooth extraction: the nerve of the tooth may be touched when the tooth is extracted, resulting in numbness of the tooth that lasts for a long time. There may be other reasons such as malignant tumors in the oral and maxillofacial region, which may cause numbness for several months, and it is recommended to go to the hospital in time.