Apical periodontitis mainly from the following aspects to confirm the diagnosis: 1, clinical symptoms: apical periodontitis teeth generally have bite discomfort or pustules on the gums, the patient will say that the bite is uncomfortable, a pustule on the gums, repeated pus, repeated bad; 2, the examination found that the affected teeth have caries, bad restorations, bad fillings or other periodontal diseases; percussion examination discomfort, sinus tracts on the gums, can be suggestive of Periapical tissue lesions; 3, the main diagnosis is still with the help of X-rays, through X-rays, you can clearly see whether the caries cavities spread to the pulp tissue, whether the affected teeth periapical bone damage, to provide an accurate basis for diagnosis. When the affected teeth appear obvious bite discomfort, pulp vitality has been necrosis, X-ray film suggests periapical bone lesions, can be diagnosed as chronic apical periodontitis.