Pulpitis lesion process, with the body’s own resistance to change and external stimulus response can be divided into the following three cases: 1, remove external stimuli: such as caries tissue and bacteria removed, the inflammation can be controlled immediately, the body’s ability to give full play to the restoration of the tissue gradually return to normal; this situation is mostly seen in the young permanent teeth, due to the inter-root foramen is large, rich in blood, pulp inflammation is light, and the general health status is better; 2, the external stimulus exists for a long time: that is, this patient usually periodontitis stimulus is not strong, weak, after the pulp will present a chronic state, so the patient did not treat pulpitis; 3, the external stimulus is more powerful and has always existed: the pulp inflammation will be further developed, necrosis of tissues, all the pulp to lose vitality, i.e., pulp necrosis. From the process of inflammation development, pulpitis to pulp necrosis depends on a number of factors, so the time can not be predicted. The patient’s general condition, the degree of localized removal of decayed tissue, and the effect of the patient’s medication on the decayed tissue may influence the process of pulpitis to tooth necrosis.