Abstract
Thirty-two healthy, dentate volunteers with unexplained non-systemic halitosis took part in this blind, 2-cell (metronidazole and quinine control), randomised, single rinse, crossover study. The effects of both mouthwashes on the tongue bacterial microbiota, salivary microbiota, breath odour and the odour generating potentials of subjects’ saliva were measured. Metronidazole mouthwash reduced both breath odour and incubated salivary odour to a significantly greater extent (p<0.05) than did the quinine control. The odour reduction was associated with a significant reduction in the bacterial counts per unit area of tongue surface. In particular, the reductions in the strict anaerobic species (up to 1.5 log-fold) and proportions of sulphide-producing organisms, were highly significant (p<0.001), even up to 24 hours post-rinse. This study confirmed the highly selective nature of metronidazole. The concomitant reduction of both breath odour and recovery of strict anaerobes from the tongue (correlation, r2=0.776; p<0.005) supports the theory that this group of organisms are the major contributors to oral malodour production.