Endodontitis diagnosis is a three-step process: the first step is to ask the patient to get the initial impression, then to check the possible causes and the affected teeth, and then to verify the pulp temperature and related examinations on the suspected teeth. 1. The clinical manifestations of patients with pulpitis are mostly characterized by spontaneous and paroxysmal pain, which is heavier at night than during the day, and is more significant especially when lying down. Early stage of the disease can be aggravated by both hot and cold stimulation, but late stage of the disease can be relieved by cold stimulation instead. 2. Examine the maxillary and mandibular teeth on the painful side carefully, and make clear whether there is a way to cause pulpal infection. Determine the suspect tooth by performing a routine oral examination. 3. A very important step in the diagnosis of endodontics is the pulp vitality test. The diagnosis of pulpitis relies on the results of the pulp temperature test. It is recommended that the patient should be guided by the doctor and combined with professional examination instruments to help clarify the diagnosis. In general, pulpitis can be prevented by paying attention to oral hygiene, regular oral checkups and treatment of dental caries. The treatment mainly consists of root canal therapy, along with anti-inflammatory and analgesic medications.