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2nd. Edition

Microorganisms and Oral Malodor

It has long been acknowledged that most cases of bad breath are the result of microbial putrefaction within the oral cavity (Howe, 1898; Berg and Fosdick, 1946; McNamara et al., 1972). Many oral bacteria produce hydrogen sulfide and other volatiles when incubated anaerobically in the presence of serum, saliva, or other substrates (Persson et al., 1989; 1990).
Indeed, humans classify practically all bacterial odors as foul, perhaps as an age-old mechanism to avoid infections and spoiled food. In their respective chapters, Niles and Gaffar, Kleinberg and Cocadipilly, and Loesche and De Boever describe ongoing work to identify specific species which may be major contributors to oral malodor in situ.. Goldberg and coworkers (this volume) used a decarboxylase medium to obtain in vitro samples that smell similar to bad breath (see also Markovich et al., this volume). However, attempts to isolate individual strains which produce this odor have not yet proven successful.

Even within the oral cavity, odors from different sites have different characteristic smells. For example, the odor emanating from the posterior tongue dorsum differs greatly from the odor characteristic of subgingival plaque (Rosenberg and Leib, this volume). Future research is necessary to determine whether the distinctiveness of the various odors derives from different molecular constituents, different ratios of the same components e.g., hydrogen sulfide and methyl mercaptan (Yaegaki, this volume), or a combination of both these possibilities. Similarly, it is not known whether these variations in odor are associated with distinct microbial communities and/or availability of different putrefiable substrates.