Modeling of the oral malodor system and methods of analysis

Bacterial putrefaction is the central metabolic process involved in oral malodor and can easily be modeled in the salivary sediment system developed from centrifuged whole saliva. Methods used in this system for examining malodor have included measurement of (1) head space (gaseous-phase) and liquid-phase odors, organoleptically; (2) volatile sulfur compounds, by means of an electrochemical sensory instrument; (3) pH, Po2, and oxidation-reduction potential with appropriate respective electrodes; (4) the malodorous compounds indole and skatole, colorimetrically; (5) substrate levels and their effects; and (6) bacterial numbers and types. The simplicity of the system permits other analyses to be easily added, if needed, and the influence of factors and agents that affect oral malodor to be assessed. Addition of odorigenic or non-odorigenic pure cultures to the mixed bacterial flora of the system enables modification of the microflora composition and high- and low-odor-production microflora to be simulated and compared. Modeling validity has been enhanced by the use of complementary in vivo methods, such as a method used to measure the ability or potential of an oral microbial flora to produce malodor. The method involves in vivo challenge testing with cysteine, an amino acid, and measuring the hydrogen sulfide produced. Oral malodor is a multifactorial condition and models enable its systematic study and the quantitative testing of antimalodor agents.