Swelling and pain at the place where the root of the lower gums and the lips connect may be caused by oral ulcers, apical periodontitis, periodontitis and so on. 1. Mouth ulcers: this disease is mainly caused by infection, endocrine changes, environment, genetics, immunity, stress, food allergies and other factors, the patient will appear in the root of the lower gums and lips connected with the place of swelling and pain, accompanied by low fever, fatigue, headache and other symptoms. 2. Apical periodontitis: this disease is mainly caused by bacterial infection, physical factors and chemical stimulation, resulting in tissue damage, inflammation, resulting in the root of the lower gums and lips connected to the place of swelling and pain, the patient is mainly manifested as a localized abnormal sensation and dysfunction, the patient has pain, there will be discomfort in chewing, and some patients will appear pustules. 3. Periodontitis: due to improper brushing methods, teeth misalignment and crowding, food congestion and other factors, the patient will appear in the root of the lower gums and lips connected to the place of swelling and pain, the patient will feel the root of the teeth localized swelling, bad breath, with the development of the disease, will cause deep periodontal tissue lesions, periodontitis. It is recommended that patients go to the hospital in a timely manner, under the diagnosis of the doctor, according to the patient’s specific condition, to take targeted treatment, life should maintain oral hygiene, eat less spicy stimulation, too cold and too hot food.