By Joyce Cohen, Special for USA TODAY
So the person you're talking to decides to chew on some gum or mints and offers you some, too. Hmmm. Does she think her breath smells bad — or is she hinting yours does?
It's a vexing and often taboo topic. Despite shelves full of products to fight bad breath, there's little solid information on whether they really work.
Now, though, there seem to be alternate solutions to what some delicately call "breath control," with mouthwashes touting new combinations of ingredients.
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Bad breath is a challenge. There are multiple causes — from medical problems (like diabetes and sinus conditions) to dry mouth to stinky food to rare cases of tonsillolith, little reeking balls of hardened plaque that form in the tonsils.
There are also multiple variables — from time of day to oral care — that affect even garden-variety bad breath, which results from gaseous byproducts of bacteria that flourish in plaque.
Despite assorted rating techniques and machines to measure mouth gases, the "primary reference standard" remains the human nose, the American Dental Association says.
"You know it when you smell it," says Clifford Whall, director of the ADA's Seal of Acceptance program.
Some researchers say nearly all adults have, at the very least, some morning breath. Others claim that half the adult population has bad breath, with half of those having a severe, chronic problem.
In 2007, Americans spent nearly $6.7 billion on mouth-freshening products, according to Euromonitor International, a market-research firm.
That says nothing, however, about how well these products work. "I think most of them work, to varying levels," says Patricia Lenton, a dental hygienist and research fellow at the University of Minnesota School of Dentistry, who participated last summer in the seventh annual conference of the International Society for Breath Odor Research.
Sodium chlorite to the rescue?
There is a big difference, of course, between an odor-masker that will turn breath minty fresh for a few minutes and a rinse that will keep bad breath at bay all day. Oral malodor is a "complex problem," says Marvin Cohen, who studied microbiology before becoming a dentist. Cohen, of St. Louis, is the developer of SmartMouth, a mouthwash invented by Israel Kleinberg, professor of oral biology and pathology at Stony Brook University.
The brand-name "germ-killing" mouthwashes include mainstays like Listerine and Scope. They do kill bacteria, Lenton says, but it's unclear what that means for bad breath.
Says Laura Brinker, spokeswoman for Scope: "We think of fresh breath as provided by the minty flavor experience." Bad breath, she adds, "is very subjective." And Listerine spokeswoman Meghan Marschall argues that the product not only kills bad-breath germs but also fights gum disease, delivering "additional therapeutic oral care benefits."
The primary ingredient in this newer class of mouthwashes with clinical-sounding names such as TheraBreath, Oxyfresh, CloSYS and ProFresh is sodium chlorite, also known as stabilized chlorine dioxide, sometimes used as a water purifier. These rinses claim to freshen breath for up to six hours. But one independent study found that several different sodium chlorite rinses worked for anywhere from four to 42 minutes.
These products change the chemical composition of odiferous gases so they no longer smell, but underlying bacteria remain potent and continue producing odors, Cohen says.
SmartMouth uses sodium chlorite, but in a new twist, it must be mixed with zinc chloride just before use. The zinc ions find the bacteria that produce rancid gases after eating amino acids, then block the amino-acid receptor sites so the bacteria cannot produce gas, Cohen says. After the bacteria die in around 12 hours, they are replaced by new bacteria. Again, it's time to rinse.
The National Advertising Division of the Council of Better Business Bureaus recently announced that a review of dental literature substantiated SmartMouth's claim that it prevents bad breath 12 times longer than any other mouthwash.
Another brand, Biotene, with its mouthwashes that combat dry mouth, takes a different approach. Its new PBF, or plaque-biofilm dissolving mouthwash, contains two enzymes that break down the biofilm and put the mouth bacteria into a healthy balance, says Michael Pellico, a Biotene chemist.
There's promising research on yet another liquid — a combination of zinc and chlorhexidine.
Still, without reliable comparative testing, it is hard to know what works well, Lenton says. "People will tell you they have data, but then you see it" and find flawed methodology, she says. A report on oral malodor by the ADA found that results of most studies are "equivocal and proprietary."
The ADA's Whall stands by the report. Though the companies claim to have studies showing their mouth products are effective, "we can't verify" those claims, Whall says.
Even with the most effective products, however, some people practice such bad oral hygiene that nothing will help.
"There is still a lot of work to be done on bad breath," says Harold Katz, the California dentist who developed TheraBreath products.