A toothache at night is commonly caused by pulpitis. In general, the most common cause of pulpitis is tooth decay, also called tooth decay, and when tooth decay occurs, you need to go to the dentist to fill the tooth in time. If the tooth is not filled in time, the caries will continue to aggravate and invade the pulp cavity, leading to the phenomenon of infection in the pulp cavity. Once the infection occurs in the pulp cavity, the pressure will increase and severe pain will occur, which may be relatively mild in the daytime but very severe at night. It is recommended to visit the endodontic department of the hospital for a detailed examination of the specific situation. If pulpitis is diagnosed, root canal treatment is required, which means drilling the pulp cavity, removing the infected pulp, preparing the root canal for irrigation and disinfection, and finally filling the treatment.