There are more possible causes for the left tooth pain, and the treatment varies from patient to patient with different causes. The details are as follows: 1. If it is a disease of the tooth itself, such as tooth decay, pulpitis, periapical inflammation, etc., it is necessary to actively consult a doctor for filling treatment, root canal treatment, etc. 2. If it is a disease of periodontal tissue, such as gingivitis, periodontitis, periodontal abscess, etc., it is possible to do local periodontal rinsing and medication in the acute period of pain. After the acute period, systematic periodontal treatment, including scaling and scraping, is required. 3. If the disease is in other tissues near the tooth, such as septic maxillary sinusitis, its invasion of nerve endings can also lead to tooth pain, which requires surgery, usually sinus drainage treatment. 4. If the disease is in the nervous system, such as trigeminal neuralgia, drugs such as carbamazepine can be taken under the guidance of a doctor. Therefore, if there is pain in the left side of the tooth, it is recommended to actively seek medical examination and carry out targeted treatment according to different etiologies.