Chronic pulpitis is the most common type clinically, with atypical clinical symptoms, and in some cases there may be no spontaneous pain. If the virulence of the bacteria invading the pulp is low and the resistance of the body is strong, the inflammation of the pulp tissue is mostly manifested as a chronic process. Chronic inflammatory cell infiltration can be maintained for a longer period of time, and the periodontal membrane at the root tip, then, can become a peripheral area of the pulpal inflammatory center, with mild edematous changes, so clinically the affected tooth can have mild percussion pain, or the x-ray shows blurring and widening of the periapical area. If the exudate of acute inflammation is drained, but the inflammation is not completely eliminated, it can also be transformed into chronic inflammation. Conversely, if the body’s resistance is reduced, or if local drainage is poor, chronic pulpitis can be transformed into acute pulpitis, i.e., an acute attack of chronic pulpitis. Chronic pulpitis can be divided into chronic atretic pulpitis, chronic ulcerative pulpitis and chronic proliferative pulpitis according to pathological changes, and a special clinical manifestation, namely, residual pulpitis. In chronic atretic pulpitis, there is no obvious spontaneous pain or occasional dull pain, but almost all patients have a long history of hot and cold stimulation, while in chronic ulcerative pulpitis, there is no obvious spontaneous pain, but patients often complain of severe pain when food is embedded in the cavity of the affected tooth, and another typical symptom is severe pain when hot or cold stimulation irritates the affected tooth. The third type of chronic hyperplastic pulpitis is usually without spontaneous pain, but sometimes patients may complain of pain or bleeding when eating, so they are afraid to chew food with the affected side for a long time.