Salivary Flow, Tongue-Coating Burden, and Morning Breath Odor: A Cross-Sectional Study

Background and Objectives: Morning halitosis undermines social well-being, yet the combined influence of basal salivary flow and tongue coating in healthy adults is unclear. Methods: In a cross-sectional study of 92 university students (18-35 years), we measured unstimulated salivary flow rate (uSFR), tongue-coating index (TCI), total volatile sulfur compounds (VSCs; Halimeter^®), organoleptic score (0-5), and self-perceived halitosis (yes/no) under standardized early-morning conditions. Results: Thirty-seven participants (40.2%) reported morning halitosis and showed lower uSFR (0.2 ± 0.1 vs. 0.3 ± 0.1 mL·min^-1) and higher TCI (2.3 ± 0.5 vs. 1.9 ± 0.4), with higher organoleptic scores (3.4 ± 0.6 vs. 2.1 ± 0.7) and VSCs (272.9 ± 39.8 vs. 163.7 ± 45.9 ppb; all p < 0.001). VSCs correlated inversely with uSFR (ρ = -0.58) and positively with TCI (ρ = 0.44). In multivariable models, uSFR (β = -0.53) and TCI (β = 0.31) explained 54% of VSC variance; each 0.1 mL·min^-1 fall in uSFR increased the odds of self-perceived halitosis 1.9-fold (p = 0.001). Conclusions: Even among healthy young adults, lower basal saliva and heavier tongue coating are independent contributors to morning malodor. Hydration, daily tongue cleaning, and addressing mouth breathing are pragmatic, first-line strategies.