Periodontitis, commonly known as fire tooth, is a chronic inflammation of the soft tissues at the gum margin caused mainly by various types of causes. Toothache can be judged from subjective and objective causes, mainly whether the gingival margin has a long-term accumulation of the initiating factors of fire – plaque, calculus and other promoting factors, poor restorations, food impaction, breathing through the mouth, etc. During the examination, it is found that the gums are dark red in color, the gingival margin thickens and does not cling to the tooth surface, the gingival papillae are congested X-ray examination is very important for the diagnosis, prognosis and evaluation of the efficacy of periodontitis, and is also one of the important means of clinical diagnosis. Early diagnosis and timely treatment of periodontitis is important to prevent the aggravation of the disease and to preserve the integrity of the tooth, so it is important to go to the regular hospital dentistry in time to avoid missing the best time for treatment.