The causes of severe toothache at night include pulpitis, periodontitis and apical periodontitis. 1. Pulpitis: mainly refers to the inflammatory lesions occurring in the pulp tissue, including acute pulpitis and chronic pulpitis. The main clinical manifestation is severe tooth pain, patients will be difficult to sleep because of the pain, and the pain is paroxysmal aggravation. 2. Periodontitis: a chronic inflammation that occurs in the periodontal support tissues. Periodontitis can change the relationship between tissue resistance and commensal bacteria in the mouth to a certain extent, and its main features are periodontal abscesses and gradual loosening of teeth. However, it can aggravate the toothache when relaxing at night. 3. Periapical periodontitis: It is an inflammation of the tissues around the root tip of the tooth. This inflammation is triggered by an infection, and the infectious material comes from inside the pulp cavity. The main symptom is pain, the tooth will feel ambidextrous, there will be biting pain, and some of the teeth will seem loose. The pain may worsen at night. To summarize, there are many reasons for a severe toothache at night, and it is recommended to consult a doctor in time to clarify the cause of the disease before carrying out targeted treatment.