The following methods can be used to relieve tooth decay pain at night: 1.When deep cavity is formed in the crown of the tooth, you can place clove flowers or pepper grains inside the cavity to play a soothing and analgesic effect. 2.When deep cavity causes pulpitis attack and the pain is fluctuating jumping pain, it may be that the pulp has become abscessed, you can rinse ice water or place ice cubes to the jaw surface of the affected tooth to induce the pulp volume to contract and reduce the pressure in the pulp cavity, so as to relieve the pain. 3.You can take diclofenac sodium type pain medication orally. If the pain is unbearable, you can go to a nearby hospital, where the doctor will administer local anesthesia to relieve the pain and then perform pulp drainage on the affected tooth.