Salivary NETosis-Related and Oxidative Stress Biomarkers Define a Conventional Cigarette Smoking-Associated Inflammatory Phenotype in Periodontitis: A Cross-Sectional Observational Study

Background/Objectives: Cigarette smoking is a major risk factor for periodontitis, but the salivary host-response profile associated with smoking-related periodontal inflammation remains incompletely characterized. This study compared salivary NETosis-related and oxidative-inflammatory biomarkers among current smokers, former smokers, and never-smokers with periodontitis. Methods: This cross-sectional study included 159 systemically healthy adults with periodontitis (53 per group: current smokers, former smokers, never-smokers). Individuals with systemic diseases or concomitant medications that could interfere were excluded. Unstimulated whole saliva was analyzed for NETosis-related biomarkers (MPO-DNA complexes, citrullinated histone H3, neutrophil elastase, cell-free DNA) and oxidative-inflammatory markers (MMP-8, IL-1β, IL-6, TNF-α, 8-OHdG, total antioxidant capacity). Results: Salivary MPO-DNA complexes differed significantly among groups (current smokers 33.52 ± 9.96, former smokers 26.90 ± 8.38, never-smokers 19.20 ± 7.50 ng/mL; p < 0.001, η2 = 0.317). The composite NETosis score (η2 = 0.702) and oxidative-inflammatory score (η2 = 0.718) showed the same graded pattern. Biochemical verification confirmed clear group separation (salivary cotinine: current smokers 312.3 ± 77.0, former smokers 9.7 ± 5.1, never-smokers 3.2 ± 1.4 ng/mL). Smoking exposure was positively correlated with biomarker levels and the severity of periodontal disease. Smoking status remained independently associated with MPO-DNA complexes and the NETosis score after covariate adjustment. Conclusions: Current smoking was associated with an enhanced salivary NETosis-related and oxidative-inflammatory phenotype. Former smokers displayed an intermediate profile. Salivary MPO-DNA complexes and composite biomarker scores warrant further investigation as candidate non-invasive indicators of smoking-associated periodontal inflammatory burden, pending diagnostic performance analyses and prospective validation.