Halitosis is primarily the result of anaerobic Gram-negative proteins and producing volatile sulfur compounds (VSCs) – mostly methyl mercaptans and hydrogen sulphides (Tonzetich 1977). Oral malodor may also occur due to mouth breathing, oral infections, dietary constituents, as well as extra-oral factors. Meticulous oral hygiene reduces the level of oral bacteria, the production of VSCs, and therefore oral malodor. Tongue cleaning has also been recommended to help combat oral malodor since odorproducing bacteria commonly reside on the tongue (Figure 16; Outhouse et al. 2006; Tonzetich & Ng 1976, Van der Sleen et al. 2010).
Figure 16. Coating on tongue and heavy bacterial load
VSCs are the bacterial byproducts of metabolic activity, especially in anaerobic Gram-negative bacteria that proliferate on the tongue. Stannous fluoride exerts its anti-bacterial effect, primarily through metabolic inhibition. Ultimately, this leads to a reduction in the production of VSCs. Stannous ion can also bind directly to the sulfur sites in the sulfur-containing metabolic substrates (e.g. the sulfur-containing amino acids methionine and cysteine) creating competitive antagonism for their metabolism. The net effect of either mechanism of action is to reduce the level of foul-smelling VSCs (Figure 17)..
Figure 17. Source of Oral Malodor: GNA bacteria use protein as an energy source and produce volatile sulfur-containing by-products