I think that we have been fooled by numbers again into thinking that a product is much more effective than it really is.
What does “kills 99% of the germs that cause…” really mean?
It means that after treatment, only about 1% of the germs in a mouth swab can be cultured under standard aerobic conditions. That is not the same as killed.
The causal claims are just plain silly – germs do not cause tooth decay, bad breath, or gingivitis. Germs are nothing more than “challenges” to our defense systems, just contributory factors to the adverse conditions. Good nutrition is the best antidote to all three conditions, not an antiseptic mouthwash.
Let’s look more molecularly at the issue of tooth decay.
The glycolytic enzymes in oral bacteria convert glucose into lactic acid, which leaches calcium from teeth. The bacterial enzyme dextran sucrase converts sucrose into dextran, which helps hold bacteria and the acid they produce to the surface of the teeth.
The question is, by what percent are these key enzymes of tooth decay inhibited? If it is only by 30-50% or so, as I suspect, then mouthwash makes a two-fold difference in the rate of production of acid and dextran, or less, not the 100-fold difference the ad appears to be implying.
Consider data monitoring the conversion of ethanol to acetaldehyde by the bacterial enzyme alcohol dehydrogenase. This enzyme lost only about 30-50%* of its activity following a treatment with germ-killing mouthwash. Is this more typical of the effect? Clearly, if enzymes are inhibited only 30-50%, we need to remove the bacteria from the teeth and from the mouth and throat (debridement with agents such as hydrogen peroxide?), and not merely “kill” them, to seriously inhibit the process of tooth decay, and conceivably also inhibit bad breath and gingivitis.
* “Salivary acetaldehyde concentrations are decreased after an antiseptic mouthwash by approximately 30–50%, underlining the importance of oral bacteria in acetaldehyde generation” – Nature Reviews: Cancer. August 2007, p. 599 ff, citing: Homann, N., Jousimies-Somer, H., Jokelainen, K., Heine, R. & Salaspuro, M. High acetaldehyde levels in saliva after ethanol consumption: methodological aspects and pathogenetic [sic] implications. Carcinogenesis 18, 1739-1743 (1997).