The document discusses supportive periodontal therapy (SPT). It defines SPT as therapeutic measures needed to support a patient's efforts to control periodontal infections and avoid reinfection. The document outlines the rationale for SPT, noting that no definitive periodontal treatment exists and continuous monitoring and treatment is needed to prevent disease recurrence. It describes patients susceptible to periodontitis as being at high risk of reinfection and progression without SPT. Regular SPT including subgingival scaling is important for long-term benefits of periodontal treatment.