Severe periodontitis does not require annual subgingival scraping, but maintenance treatment should be performed every 6~12 months. 1. Patients with severe periodontitis should undergo scaling every 6~12 months after active treatment, as well as targeted treatment for factors causing plaque retention, such as caries, overhanging fillings, and exposed rough root surfaces. 2. Because plaque is constantly formed, periodontitis patients simply self oral health care is not enough to maintain periodontal health, some deep periodontal pockets or root bifurcation area of the lesion depth there is still chronic inflammation, and severe periodontitis after treatment, periodontal tissue and root surface tissue healing mode is mostly long combined with the epithelial healing, in the bacterial invasion of inflammation is prone to recurrence. If the symptoms of periodontitis recur, it is recommended to go to the hospital in time.