Late last year, the U.S. Food and Drug Administration warned three mouthwash manufacturers to stop suggesting that their products that have fluoride as the main active ingredient would prevent gum disease and remove dental plaque, the sticky biofilm of bacteria and other substances that collects on teeth above and below the gumline. And several years ago, a federal judge ordered Pfizer, which owned the Listerine brand at the time, to stop an ad campaign that said the mouthwash was as effective as flossing for preventing tooth and gum decay.
Mouthwash manufacturers started making claims about their products preventing plaque and gingivitis (inflammation of the gums) in the early 1980s, after experiments conducted in the mid-1960s showed that gingivitis developed in a matter of weeks in the absence of oral hygiene.
Many of the mouthwashes are highly artificial concoctions that contain sweeteners for taste and artificial colorings. Alcohol is often included because it keeps other ingredients in solution and tends to accentuate the flavor. Mouthwash will make your breath smell better for some period of time. The question is whether that's achieved by ingredients that kill off bacteria or by strong flavors that merely mask the problem.
A 2008 review of the existing research (only five studies passed muster) concluded that two of the antibacterial agents most commonly used in mouthwashes, cetylpyridinium chloride and chlorhexidine, may reduce the levels of bacteria that produce halitosis (bad breath), and that other ingredients (zinc, chlorine dioxide) may neutralize smelly sulfur compounds.
Cetylpyridinium chloride is an ingredient in Scope, Cepacol, and other popular brands. In this country, mouthwashes containing chlorhexidine, such as Peridex, are available by prescription only and used mainly after oral surgery. The problem with chlorhexidine is that it creates brown stains on the teeth and gums.
Bacteria cause both cavities and gum disease, but the species that cause cavities are different from those that cause gum disease, said Dr. Nadeem Karimbux, an associate professor at the Harvard School of Dental Medicine.
The dozen or so species of bacteria that cause gum disease interact with gum tissue, causing inflammation, which can break down gum tissue as well as the bone that holds teeth in place. Brushing and flossing is the best way to remove plaque, but the antibacterial ingredients in mouthwash do have a modest effect.
If it weren't for those brown stains, we might see a lot more mouthwashes bragging about their chlorhexidine content, because it may be the most effective of the commonly available — and tested — agents.
The 19th century inventors of Listerine were on to something because the four essential oils in Listerine (eucalyptol, menthol, methyl salicylate, thymol) have also come out of the clinical trials looking quite effective, even if Pfizer did overreach with claims of equivalence to flossing. Listerine has the American Dental Association's "Seal of Acceptance" as a plaque fighter. A review done several years ago found the evidence for cetylpyridinium chloride more mixed.
The conventional mouthwashes do not prevent cavities, nor do they claim to. The bacteria that cause tooth decay need to be removed by mechanical means, principally brushing. However, there are now mouthwashes on the market that contain fluoride, and some of them, like ACT Fluoride Rinse, have the ADA's blessing as proven cavity fighters.