Toothache caused by pulpitis occurs at night, and the pain is so severe that it prevents sleep. The pulp tissue is located in the pulp cavity, and the pulp is connected to the rest of the body through the narrow apical foramen. The pulp is surrounded by the hard dentin wall except for the apical foramen, so it is not easy to establish drainage when inflammation occurs, and the inflammatory exudate accumulates. Once the pulp cavity is penetrated, the pressure drops and the pain decreases abruptly. The causes of pulpitis are bacterial, physical, chemical, and idiopathic factors Bacterial factors: Pulpitis can be considered an infectious disease, and bacteria are an important causative factor in pulp disease. There are three ways to cause pulp infection: transdental infection, periodontal infection and blood-borne infection. Bacteria can directly infect the exposed pulp when caries, traumatic tooth fracture and accidental pulp exposure during drilling and grinding, cuneiform defect pulp exposure, severe abrasion pulp exposure in the elderly, deformed central cusp fracture or abrasion pulp exposure, deformed lingual fossa or bottom of deformed lingual sulcus without enamel coverage, and cryptic fracture deep into the pulp cavity, such as the dentin covering the pulp tissue is very thin, bacteria and their toxic products can cross the dentin tubules to reach the pulp cavity and Bacteria can also enter the pulp cavity through the periodontal pockets to the root tip and through the apical foramen causing retrograde infection; this kind of pulpitis caused by periodontal infection of the pulp is called retrograde pulpitis; pulpitis caused by blood-borne infection is very rare. Physical factors: Acute dental trauma, such as traffic accidents, sports, violent fights, or sudden chewing of hard objects during eating, as well as accidents in medical work, such as mechanical trauma caused by excessive force during orthodontic treatment, moving teeth too fast, accidental injury to the root periapical of adjacent teeth during tooth extraction, injury to the apical vessels during scaling of deep periodontal pockets, traumatic occlusion, filling or other restorations too high, etc. Mechanical trauma caused by chronic bite trauma dentition. Chemical factors: extreme temperature stimulation, such as high-speed, continuous drilling and grinding of teeth, unpadded silver amalgam filling of deep cavities, repeated external temperature stimulation and, rarely, electric current stimulation. Idiopathic factors: Intradental resorption and extradental resorption can cause some pulp lesions of unknown origin.