Correlation between oral malodor and bacterial composition in saliva

Objectives: Oral malodor generally originates from bacterial populations in the oral cavity. However, the relationship between the bacterial composition of the oral microflora and oral malodor remains unclear. This study sought to discover and characterize the pattern of the bacterial flora in saliva correlated with oral malodor. Methods: Paraffin-stimulated saliva was collected from 69 patients who visited the Oral Malodor Clinic of Fukuoka Dental College Medical and Dental Hospital complaining of oral malodor and 61 undergraduate and graduate students in Kyushu University Faculty of Dental Science. All of the subjects had no periodontal pockets deeper than 4 mm. Terminal restriction fragment length polymorphism (T-RFLP) analysis was performed for each saliva sample, and 130 subjects were classified into three clusters based on the T-RFLP patterns found in the bacterial population composition in their saliva. The concentrations of three volatile sulfur compounds (VSCs; hydrogen sulfide, methyl mercaptan and dimethyl sulfide) in the mouth air were then compared among the three clusters. Results: The amounts of three VSCs differed significantly among the three clusters although there were no statistical differences in the amount of tongue coating. A cluster producing high levels of VSCs had a drastically different bacterial flora, in which Prevotella and Veillonella species were predominant, as compared with other clusters. Conclusion: These results suggest that the comprehensive bacterial composition of saliva should be considered when dealing with oral malodor, and reveal that T-RFLP can be used to demonstrate characteristic patterns of salivary microflora correlated with oral malodor.