Halitosis is an unpleasant odour that emanates from the oral cavity and can be serious enough to cause personal embarrassment.  The prevalence of halitosis (bad breath or oral malodour) has been reported to be in the order of 50% although this has been questioned. The majority of cases (86%) are considered to be as a result of oral problems. Although , nasal inflammation, diabetes mellitus and uraemia have also  suggested as causes.   The aim of this  review was to investigate the effect of mouthrinses on oral malodour in comparison with placebo⁄control mouthwash in studies with patients who used the mouthwash multiple times for a minimum follow-up period of more than 1 day.

The authors searched the  PubMed-Medline, Cochrane Central Register of Controlled Trials (CENTRAL) and EMBASE databases. Screening and selection was carried out independently by two authors.  Randomized controlled trials (RCTs) or controlled clinical trials (CCTs)  where volatile sulphur compound measurements, organoleptic measurements and tongue coating were used as outcome variables were included. A quality assessment was undertaken , with the GRADE system being used to classify the evidence.

12 RCTs were included ( 6 parallel, 6 cross over) .The risk of bias was low for seven trials, moderate for three and high for two.  A qualitative summary was presented.

The authors concluded

In this review, nearly all mouthwashes with active ingredients had beneficial effects in reducing oral malodour in both short- and longer-term studies. The most compelling evidence was provided for chlorhexidine mouthwashes, and those that contained a combination of cetyl pyridinum chloride and zinc provided the best evidence profile on oral malodour. Little data with respect to tongue coating were available, and none of the studies showed a beneficial effect for this parameter.

Blom T, Slot D, Quirynen M, Van der Weijden G. The effect of mouthrinses on oral malodor: a systematic review. Int J Dent Hyg. 2012 Mar 19. doi:10.1111/j.1601-5037.2012.00546.x. [Epub ahead of print] PubMed PMID: 22429551.

Relavant Cochrane Review

A Cochrane review was published on this topic in 2008. That review included five RCTs, involving 293 participants.  Interestingly,  only 3 of the studies included in the Cochrane review were subsequently included in this new review, which included 12 studies.  Three of the studies included in this new review were specifically excluded by the Cochrane reviewers and of the twelve included, only two were published after the Cochrane review.

The Cochrane review concluded

Mouthrinses containing antibacterial agents such as chlorhexidine and cetylpyridinium chloride may play an important role in reducing the levels of halitosis-producing bacteria on the tongue, and chlorine dioxide and zinc containing mouthrinses can be effective in neutralisation of odouriferous sulphur compounds.  Well designed randomised controlled trials with a larger sample size, a longer intervention and follow-up period are still needed.

It is worth noting that athough the authors of the new review suggest long term benefits – the longest trial is still only 4 weeks!

Fedorowicz Z, Aljufairi H, Nasser M, Outhouse TL, Pedrazzi V. Mouthrinses for the treatment of halitosis. Cochrane Database of Systematic Reviews 2008, Issue 4. Art. No.: CD006701. DOI: 10.1002/14651858.CD006701.pub2.