Swelling of the bed behind the big teeth may be caused by wisdom tooth pericoronitis, apical periodontitis, depending on the situation, need to carry out local medication rinsing or root canal treatment. 1. Wisdom tooth pericoronitis. The teeth at the back of the mouth if the gums are swollen caused by wisdom teeth may be wisdom teeth pericoronitis attack, due to wisdom teeth blocking the gums will form deep blind pockets, swollen and painful gums, usually for local hydrogen peroxide rinse, the use of iodine glycerin medication, to be eliminated after the inflammation, consider wisdom teeth extraction. 2. Periapical inflammation. The teeth at the back of the mouth may also be due to dental caries, causing periapical inflammation, inflammation through the apical part of the periosteum to reach the submucosa, causing swelling of the gums around the teeth, usually root canal treatment of the affected teeth to open the pulp drainage, the swelling will slowly reduce. Swelling of the gums behind the big teeth, it is recommended to seek medical treatment in time to avoid inflammation aggravation caused by interstitial infection.