Toothache is no longer painful after drilling, due to the release of pressure in the pulp cavity and the drainage of secretions, so there is no pain. 1. Pulpitis and periapical inflammation can cause toothache, it is necessary to relieve the pain through root canal treatment, the first step of root canal treatment needs to open the pulp drainage, by releasing the pressure in the pulp cavity to quickly relieve the pain. 2. Pulpitis is caused by infection of the pulp and liquefaction and exudation of pulp cells, which leads to a sharp rise in pressure in the pulp cavity, resulting in spontaneous pain, hot and cold pain, night pain and other symptoms. By opening the pulp cavity with a dental drill, the pressure inside the pulp cavity is reduced and the pain is relieved. 3. Periapical periodontitis, after pulp necrosis, the purulent secretion in the root canal can not be drained through the defect, the purulent secretion stimulates the periapical tissues to produce symptoms such as occlusal pain, spontaneous pain, etc. It is also necessary to open up the pulpal cavity with endodontics, so that the thick secretion can be drained, and the pain symptoms are relieved. Toothache needs to be treated in a timely manner.