Swollen gums behind the last big tooth may be caused by wisdom tooth pericoronitis, gingivitis, acute apical periodontitis, etc. General treatment, medication and surgery can be taken according to the different causes. 1. Wisdom tooth pericoronitis: when wisdom teeth erupt incompletely, the distal part is often covered by the gums, and these positions are deeper and not easy to brush, and the gums in this part are easy to be swollen repeatedly. It is recommended to take oral anti-inflammatory treatment such as cefadroxil extended-release tablets and cefdinir dispersible tablets. It can also be combined with anti-inflammatory mouthwash such as compound chlorhexidine gargle, ciprofloxacin gargle and other mouthwashes to assist in the treatment. 2. Gingivitis: If the wisdom teeth have been extracted or have not erupted, there may be inflammation, redness, swelling and pain in the distal part of the teeth. It is recommended to use hydrogen peroxide solution, cephidium chloride gargle for repeated rinsing of the peri-coronary area, and at the same time, oral cefadroxil extended-release tablets, cefixime granules, cefdinir capsules, etc. to control inflammation. 3. Acute periapical: At the roots of the first and second molars, apical periapical inflammation occurs, which can lead to swelling of the gums. Periapical periodontitis first open the pulp chamber with chlorhexidine gluconate gargle, hydrogen peroxide solution alternately rinsed to remove infected tissues, placed in the pulp chamber camphor phenol solution, calcium hydroxide and other disinfectant drugs, to be completely removed after the inflammation, and then root canal filling. There may be other reasons for the swollen gums behind the last big tooth, and patients are advised to seek prompt medical attention and follow the doctor’s instructions for dental treatment and medication to avoid delays.