When it comes to fighting bad breath, tongue scrapers were found to be only slightly better than tongue brushing, although neither was effective for very long. This is according to a review by the Cochrane Collaboration.
Tongue scrapers, like toothbrushes, work by dislodging food, cells, and bacteria trapped on your tongue. Food that collects and is not removed from between teeth, on the tongue, and around the gums can decompose. This causes an unpleasant odor.
If you continue to have bad breath, keep a written log of the foods you eat. Make a list of medications you take, too. Some medications may cause mouth odors. Let your dentist know if you've had any surgery or illness since your last appointment.
Bad breath can be caused by a number of diseases. These include chronic sinusitis, postnasal drip, chronic bronchitis, diabetes, gastrointestinal disease, and liver or kidney problems. So if your bad breath persists, don't keep relying on your tongue scraper or toothbrush. Talk with your dentist and family doctor.
"Tongue Scraping for Treating Halitosis." T.L. Outhouse et al. The Cochrane Collaboration. April 19, 2006, no. 4, http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD005519.pub2/abstract;jsessionid=A94F63A1D350D25C135FC817CF57365A.d04t04. Accessed 2013.
"Bad Breath." Mouth Healthy, American Dental Association. http://www.mouthhealthy.org/en/az-topics/b/bad-breath.aspx. Accessed 2013.