Well from what we are taught, the idea behind treating bad breath is bacterial management. Kill the bacteria that create bad breath = no more bad breath. However, the idea behind listerine, crest pro-health, and others is that they kill "all" bacteria (All is used loosely, because they cannot penetrate and kill bacteria in biofilms). Killing of "all" bacteria is not necessarily a good thing. As you know, there are plenty of bacteria in the oral cavity that are considered normal flora, and in fact can help maintain the mouth in a healthy state, for example by maintaining a healthy pH in biofilms.
To my knowledge chlorhexidine is not an OTC, but as far as I know it too is considered a broad spectrum anti-microbial, which will have the net result as the others in killing "all" the bacteria.
Moreover, some of these products, namely Listerine, have a high alcohol content which when used long-term has been indicated in an increase of oral cancer. Other products, Like Colgate Total, contain triclosan which if I recall shows a marked resemblance to agent orange. Some feel that there is a cancer risk here too. (from what I remember from organic chemistry)
Now, I am no microbiologist and I cannot vouch for the efficacy of these so-called "3rd Generation" mouth washes, like the aforementioned Smart Mouth, but from what I have read that you guys have posted, is that they single out and block the metabolism of bacteria that create hydrogen sulfide as a byproduct, via zinc, which is the culprit for halitosis.
I have used a similar product, something by the name of Dr. Katz's. Personally, despite the warnings, I am old school. If it aint burnin', It aint workin' But I don't really use mouth rinses. I brush once a day with Colgate Total (yes the agent orange one) and have strangely good oral health.
And there it is, my I HATE STUDYING FOR THE BOARDS, procrastination.
-C
