Pocket closure in stage III–IV grade C periodontitis: A multilevel analysis following non-surgical periodontal therapy

Background: Risk of disease progression and tooth loss is higher in cases where deep probing pocket depths (PPDs) and bleeding on probing (BOP) persist after active periodontal treatment. This study aimed to investigate the efficacy of non-surgical periodontal therapy on pocket closure (PC), defined as PPD ≤4 mm without BOP (PC1) or PPD ≤4 mm solely (PC2) 3 months after non-surgical periodontal treatment and to compare PC between smokers and non-smokers. Methods: This cohort study is a secondary analysis from a controlled clinical trial consisting of systemically healthy patients with stage III or IV grade C periodontitis. All the sites with baseline PPD ≥5 mm are included as diseased sites and PC at 3 months after completion of non-surgical periodontal treatment was calculated. PC was compared between smokers and non-smokers at site and patient levels. Multilevel analysis is used to investigate factors at patient, tooth and site levels affecting PPD changes and the probability of PC. Results: A total of 1998 diseased sites in 27 patients were included in the analysis. The rates of PC1 and PC2 were 58.4% and 70.2% and were significantly correlated to smoking habits at site level (r (1) = 7.03, p = 0.008; r (1) = 36.17, p < 0.001). Tooth type, mobility, clinical attachment level (CAL) and PPD at baseline significantly affected PC. Conclusions: The present findings indicate that non-surgical periodontal treatment is effective in PC, but its performance is influenced by baseline PPD and CAL and residual pockets may remain.