In the initial stage of apical infection, there is no obvious damage to the root tip, and even dental radiographs are not always able to visualize the apical infection. For chronic apical infections, however, dental radiographs are a better diagnostic tool, but it is not impossible to diagnose apical infections without dental radiographs. There are typical clinical signs of apical infection, the most typical being vertical percussion pain. For acute apical infection, even without percussion, the patient will have a sharp throbbing pain accompanied by a feeling of tooth emergence and sometimes tooth loosening, while chronic apical infection is a dull pain and a mild pain on percussion. Systematic endodontic treatment is required for both acute and chronic apical infections and must be performed in a specialized dentistry department.