Effectiveness of two supportive periodontal care protocols and outcome predictors during periodontitis: A randomized controlled trial

Background: A randomized, controlled trial was conducted to evaluate the effectiveness of two supportive periodontal care (SPC) approaches in patients with periodontitis and to evaluate possible predictors influencing bleeding on probing (BoP) changes at 24-month follow-up. Methods: Fifty-six periodontitis patients who first received active periodontal treatment by means of quadrant-wise subgingival instrumentation were subsequently assigned to either a control group (oral hygiene instruction with supragingival instrumentation and dental polishing, n = 28) or a test group (oral hygiene instruction with both supra- and subgingival instrumentation and dental polishing, n = 28). BoP was the primary outcome, and probing pocket depth (PPD), clinical attachment level (CAL), full-mouth plaque score (FMPS), gingival bleeding index (GBI), and the number of pocket sites were secondary outcome measures, recorded up to 24 months of follow-up. A mixed generalized linear regression analysis also assessed the potential confounding factors that influenced BoP changes at 24 months. Results: At 24 months, both groups showed significant improvement in periodontal outcomes (p < 0.05). The test intervention was more effective than the control in reducing median BoP (p = 0.033), GBI (p = 0.023), the number of pockets ≥4 mm with BoP (p = 0.018), 4-5 mm (p = 0.048), 5-6 mm (p = 0.011), and >6 mm (p = 0.023). Among all follow-up sessions, the reduced BoP was significantly negatively influenced by the number of median PPD (p = 0.031), the number of pockets 4-5 mm (p = 0.029), PPD 5-6 mm (p = 0.036), smoking (p = 0.039), and by the number of cigarettes/day (p = 0.042) and positively by test treatment (p = 0.033). Conclusion: SPC that included subgingival instrumentation yielded better results than the control to reduce BoP at 24-month follow-up. Smoking and deep pockets negatively influenced the BoP reduction in patients who underwent SPC. Plain language summary: Supportive periodontal care (SPC) is a series of individualized, site-specific treatments aimed at preventing periodontitis recurrence/progression after successful completion of active periodontal therapy. SPC approaches performed by means of oral hygiene instruction with supra- and subgingival instrumentation and dental polishing (test group) compared to oral hygiene with supragingival instrumentation alone and dental polishing (control group) were both effective in reducing median periodontal outcomes, such as bleeding on probing (BoP), probing pocket depth (PPD), clinical attachment level (CAL), and full-mouth plaque score (FMPS) after active periodontal treatment. However, the SPC approach that included subgingival instrumentation yielded better results compared to oral prophylaxis alone in reducing BoP, a parameter that was significantly influenced also by smoking, median PPD, a high number of sites with PPD 4-5 mm, 5-6 mm, and no sites >6 mm at 24-month follow-up.