Impact of Traditional and Alternative Nicotine-Containing Product Use on Non-Surgical Periodontal Therapy: A Systematic Review and Network Meta-Analysis

Background/Objectives: Alternative nicotine-containing products have gained popularity in recent years. Our aim is to compare clinical periodontal outcomes following non-surgical periodontal therapy (NSPT) among patients with periodontitis according to nicotine exposure status: cigarette smokers (CS), former smokers (FS), quitters (Q), users of electronic cigarettes (EC), smokeless tobacco users (ST), and non-smokers (NS). Methods: A systematic search of four electronic databases (PubMed, EMBASE, Web of Science, CENTRAL) was performed until January 2025. Sixty-seven studies were included in the qualitative synthesis, of which 56 studies were included in a frequentist network meta-analysis. Two researchers independently collected data on probing pocket depth (PPD), clinical attachment loss, bleeding on probing, plaque index, full mouth plaque score, gingival index, and gingival crevicular fluid volume. Results: NS had significantly higher change in PPD compared with CS (MD: 0.25; CI: 0.13, 0.37; 50 studies; 1359 patients; moderate certainty), EC (MD: 0.98; CI: 0.47, 1.49; 2 studies; 56 patients; very low certainty), and ST (MD: 0.99; CI: 0.49, 1.49; 2 studies; 82 patients; low certainty). Q (MD: 0.02; CI: −0.56, 0.60; 2 studies; 52 patients; low certainty) and FS (MD: 0.03; CI: –0.62, 0.69; 4 studies; 267 patients; low certainty) did not differ significantly from NS. In secondary outcomes, NS, FS, or Q were ranked first. Conclusions: FS and Q showed no statistically significant differences from NS; EC and ST generally had less favorable treatment rankings than CS. The certainty of evidence varied across exposure groups and outcomes. Further studies are needed to support firm clinical recommendations.