There is general agreement that the degree of bad breath (as reported by trained odour judges) correlates well with objective measurements (e.g. by halimeter, OralChroma, GC, GC-MS, D-MS). Since all processes in the mouth are continuous, it seems likely that a continuous [high, intermediate or low] level of malodour assumes a continuous [high, intermediate or low] generation rate. It has also been shown that oral malodour correlates strongly with microbial population numbers (i.e. quantity of cells or load) that can be recovered from the tongue surface biofilm. In other words, the amount or thickness (aerial density) of an individual’s biofilm is the most important predictor of bad breath. We have found that oral malodour levels and tongue biofilm aerial densities (i.e. load) and ecological compositions are remarkably stable over a 10-month period (for n=24 individuals) and that high, intermediate and low tongue population numbers correlate with high, intermediate and low VSC and organoleptic scores. The specific theory of oral malodour suggests that specific microbial species are responsible (i.e. are aetiological) whilst the non-specific theory suggests that the tongue biofilm “as a whole” is important, without any specific aetiological agents required. Since it is inconceivable that, whatever the species present, any significant amount of VSC can be produced from zero or close to zero amount of cells [and transforming enzymes], then it appears that “amount” is a far more important predictive factor than ecological composition; although this remains to be proven. In a diverse biofilm there may be many species present that can transform cysteine to H2S, and it seems likely that many species can “substitute for others” in different human individuals in terms of niche occupation and their role in biogenesis (i.e. generating VSC).
From a modelling perspective, the tongue surface biofilm can be classed as a continuously perfused matrix biofilm system. The nearest equivalent in vitro laboratory model is the cellulose matrix (Sorbarod) perfusion system using a real tongue-derived biofilm as the inoculum and matching the physicochemical conditions (T°C, pH and nutrient composition and flow) to what may be observed from real mouth. Data from using the in vitro model also shows that microbial growth rates (in both model and reality) are slow (μ<0.05h-1), that the cell population numbers, and ecology remain remarkably constant (quasi-steady state) and that VSC production (H2S generation rates) is also constant and proportional to amount of cells present (population density or “load”) rather than its specific composition. In this presentation, in addition to providing data that support the “load” theory of malodour, the in vitro matrix perfusion model will be compared with the real mouth in terms of responses to putative “anti-breath odour” treatments (e.g. CHX and Zn2+). |
