Salivary Inflammatory Mediators and a Tongue-Coating Dysbiosis Index as Mechanistic Correlates of Adjunctive Halitosis Therapy: A Randomized Pragmatic Trial

Background: Intra-oral halitosis is sustained by tongue-coating biofilm, but ecological and host inflammatory responses to adjunctive therapy remain unclear. Methods: In a 4-week randomized pragmatic trial (117 adults; 39 per arm; ClinicalTrials.gov NCT05876321), we compared standard care, Streptococcus salivarius K12 lozenges, and a zinc lactate/CPC/chlorhexidine rinse. Mechanistic endpoints reported here included a qPCR-derived tongue-coating dysbiosis index and salivary IL-6, IL-8, TNF-α, and MMP-8. Between-arm effects were assessed by baseline-adjusted ANCOVA, with correlation, responder, GEE, PCA, and mediation analyses. Results: Baseline values were comparable. The probiotic produced the largest dysbiosis-index reduction (−0.7 ± 0.5 vs. −0.5 ± 0.3 with zinc and −0.2 ± 0.4 with standard care, although this difference was attenuated in sensitivity analyses that removed S. salivarius from the index denominator; p < 0.001), whereas the zinc lactate/CPC/chlorhexidine rinse produced the greatest reductions in IL-8, TNF-α, and MMP-8 (all p < 0.001). Dysbiosis-index change correlated strongly with VSC change (ρ = 0.82). The probiotic effect on malodor was statistically consistent with near-complete mediation by dysbiosis reduction, versus approximately half for the rinse. Conclusions: The two adjunctive strategies showed complementary ecological and inflammatory response patterns. The dysbiosis index and mediation findings warrant external validation, and durability beyond 4 weeks remains unknown. Because S. salivarius is both a denominator constituent of the index and the administered probiotic, and because the rinse delivers three active agents together, effects cannot be attributed to a single organism or ingredient; local adverse events were more frequent with the rinse (53.8% vs. 15.4% and 10.3%).