Data extraction
periodontitis
PERIODONTITIS, EVENT
Based on the inclusion and exclusion criteria, two reviewers independently screened the literature and extracted the data (FF. Liang & YZ. Zhou). In the event of disagreement, a third author was consulted for confirmation (Z. Zhang). The extracted data included: first author, publication year, study time, country, age, gender, sample size, study design, periodontitis diagnostic criteria, periodontitis severity, interventions, influence/ confounding factor, follow-up time, and outcome.