New Review Scopes Out Mouthwash Evidence

Ruzanna Harutyunyan's picture

As it turns out, there are actually three certainties in life: death, taxes and bad breath.

Researchers studying the third inevitability say it is a problem for more than half of Americans. And while antibacterial agents can reduce bad breath, researchers want to know more about the mouthwashes readily available on the market or by prescription. A new review of studies looks at cures for the condition formally known as halitosis.

“Because most mouthwash treatments seem to work, careful and strict experimental design and implementation are required,” said review co-author Hamad Aljufairi. He is a researcher with the Medical University of Bahrain, a branch of the Royal College of Surgeons in Ireland.

The reviewers examined five studies involving 293 adult participants who used mouth rinses or placebo rinses with no active ingredients. Studies looked at over-the-counter rinses or prescription rinses.

The studies took place in Thailand, Israel, Holland, Spain and the United States. The reviewers say that study participants had “presented with a clinical or self-assessed diagnosis of halitosis” but had no underlying health conditions — such as diabetes — that might lead to increased bad breath.

Breath was monitored in the morning after participants rinsed their mouths. Participants in three of the studies assessed breath odor by using a monitor or by exam. Two of the studies measured Listerine against placebo, and one of the two measured ingredients found in some mouthwashes: cetylpyridinium chloride and zinc chloride.

The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

One review study spanning 15 days found that a mouth rinse containing extract of Garcinia, an herbal remedy, reduced bad breath levels by about 60 percent from the baseline, compared with the placebo’s 26 percent.


The reviewers concluded that chlorhexidine-containing mouthwashes, found in some brands on drug store shelves, “have been shown to be successful in reducing antibacterial activity … on the tongue and thus are seen as potentially effective agents in controlling halitosis.” They noted, however, that chlorhexidine, “also has some disadvantages, principally with the increased tooth and tongue staining, bad taste and reduction in taste sensation.”

Researchers concluded that mouthwashes containing chlorine dioxide and zinc could be effective for neutralizing the compounds that cause bad breath.

While government or scientific foundations supported two studies, pharmaceutical or oral care products manufacturers assisted three. The fact that businesses sponsored some of the research does not mean that readers should dismiss the science, according to Aljufairi. However, they should be cautious about the results “in view of the likelihood of bias and specifically the issue of vested interest,” he said.

Jan Clarkson is a dentist and researcher with the University of Dundee, Scotland, College of Medicine, Dentistry and Nursing. “We have a lot of research in pharmaceutical products,” she said. “That’s not to say it shouldn’t happen. It should. The industry research is of the highest quality.”

It does not follow that the government should conduct all research, added Clarkson, who is also an editor of the Cochrane Oral Health Group. “Government agencies would argue that if the manufacturers are going to make money, they should bear the burden of the cost of research,” she said. “Maybe there are other priorities for publicly funded research.”

Another researcher agrees that there is room for more studies. “I believe there is a need for randomized clinical trails to document not only the efficacy but the duration of the product effect,” said Patricia Lenton, a research fellow at the Oral Health Clinical Research Center, University of Minnesota School of Dentistry. “The problem is that it is very expensive to fund those types of trials.”

Data show that zinc reduces breath odor, Lenton added. “We know chlorhexidine reduces odor. We know that chlorine dioxide reduces odor. How long they work for is another question. Does it reduce breath odor for 20 minutes or 12 hours?”

One of the review coauthors is also researching effects of herbal mouthwash.

While much of the research mentioned no brand names, the following are examples of some mouthwashes that contain ingredients mentioned in this story:

• Cetylpyridinium chloride: Crest Pro-Health mouthwash.
• Zinc chloride: Tom’s of Maine Natural Mouthwash, Tartar Control
• Chlorhexidine: Prescription rinses
• Chlorine dioxide: ProFresh
• Zinc gluconate: Therabreath Plus


Please, click to subscribe to our Youtube Channel to be notified about upcoming health and food tips.