Once inflammation of the pulp occurs, it cannot progress to a better condition. The development of pulpitis can cause the death of the pulp, which is medically known as pulp necrosis. Some patients take antibacterial and anti-inflammatory drugs when they have toothache, which is not helpful. 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. In addition to the apical foramen, the pulp is surrounded by the hard dentin wall, so it is not easy to establish drainage when inflammation occurs, so that inflammatory exudate accumulates, and the lack of elasticity of the dentin wall limits the expansion of inflammatory tissue. Once the pulp cavity is penetrated, the pressure drops and the pain decreases abruptly. Pulpitis causes toothache at night, when the pain is so severe that you cannot sleep, but when the pulp is opened and decompressed, the pain decreases. The causes of pulpitis include bacterial, physical, chemical and idiopathic factors. Bacterial factors: Pulpitis can be described as 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 hematogenous 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 The bacteria can also pass through the periodontal tissue from the periodontal pocket to the root tip and enter the pulp cavity 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, damage to the apical vessels during scraping of deep periodontal pockets, traumatic occlusion, filling or other restorations too high, etc. Mechanical trauma caused by chronic bite trauma dentition, etc. Chemical factors: extreme temperature stimuli such as high speed, continuous drilling and grinding of teeth, unpadded silver amalgam filling of deep cavities, repeated external temperature stimuli and, rarely, electrical stimuli. Idiopathic factors: Intradental resorption and extradental resorption can cause some pulp lesions of unknown origin.