Australian Dental Perspectives

At the most recent meeting of the PDF, Professor Newell Johnson, Foundation Dean and Head of the School of Dentistry and Oral Health at Griffith University discussed the risks and benefits of mouthwashes containing alcohol and the principle of optimal versus excessive use of broad spectrum antimicrobials. Below is a recap of his presentation.

Professor Johnson commenced by stating that the dental profession in general placed a great deal of emphasis on oral biofilm and plaque control as the basis for preventive dentistry. He argued that most oral diseases are heavily determined by host and systemic health, including optimal diet and nutrition, and not (as some over-simplistically state), predominantly by oral hygiene-related behaviour and attitudes.

He highlighted the fact that at least 50 percent of microorganisms that inhabit the mouth are uncultivated, undescribed and their health/disease potential unknown. While some of these microorganisms are associated with disease, most are associated with health. Professor Johnson stated that plaque should be considered a part of the normal oral environment, and that a health-associated microflora is necessary for the maintenance of a healthy mouth and body. It is not necessary to remove all plaque. Gingivitis can be controlled by reasonably thorough plaque removal every 48 hours.

He went on to explain that at a micro level, fissure plaque is different from supragingival plaque, which in turn is different from sub-gingival plaque: it is the habitat which selects the microbial composition. It is when plaque matures, driven by dietary influences and oral hygiene practice or lack thereof, that it harbours potentially pathogenic microorganisms: it is this ecological shift which is associated with disease.

Professor Johnson expressed concerns about the overuse of non-specific chemical agents such as mouthwashes (some of which contain alcohol) that are designed to target all plaque in a non-specific way. PDF members suggested that a prudent approach is to recommend an antiseptic mouthrinse as an adjunct, (not a substitute), to flossing and brushing for patients with established and active dental or periodontal diseases, or to reach areas that are difficult to access or for particular patients who are highly vulnerable to plaque accumulation. Use of these products can then be assessed for efficacy in the control of mature plaque and gingivitis. The group agreed that patient compliance is an issue with home oral care routines and the dental professional should explain why rinsing with an antiseptic mouthrinse is necessary for some patients under some circumstances.

Professor Johnson's presentation also addressed the concerns which some dental professionals have about the association of alcohol containing mouthwashes with an increased risk of developing oral cancer.

He outlined that while no conclusive evidence exists to prove that alcohol in mouthwashes is linked to an increase in oral cancer, further research was required in this area to obtain a definitive answer. He suggested conducting further research in vitro, and studies comparing users and non users, and involving a variety of products (for example, all six Listerine™ variants). Professor Johnson also stated there was new evidence to suggest the alcohol related effect of increased mucosal permeability to known carcinogens, such as those in tobacco, was greatest at ethanol concentrations of 12 percent – 14 percent and less at concentrations of ethanol above 26 percent.

The PDF suggested the real risk of developing oral cancer through use of mouthwashes containing alcohol may lie with smokers, particularly when they rinse directly after smoking. It is recognised, however, that the risk of oral cancer is related to certain carcinogens found in alcoholic beverages and tobacco use, and these are confounding factors where mouthwash use is concerned.

The group recommended that further research is needed to determine how many Listerine users are smokers and when the smokers use Listerine i.e. if they use it immediately after smoking. The findings could then be used to determine what communication is required to address reeducation to smokers about the appropriate use of mouthwash.

The PDF members' discussion raised the point that mouthwashes with antiplaque properties, including Listerine and some Chlorhexidine™ mouthwashes, contain pharmaceutical grade, denatured ethanol as a vehicle to deliver antiseptic ingredients. A review by the U.S. Food and Drug Administration and the American Dental Association also found that the supporting evidence to date is inconsistent regarding the links between mouthwashes and the development of oral cancer.

In conclusion, it was pointed out that critical analysis of all the published literature, including several reviews, have led British, Canadian, American, Australian and New Zealand dental associations to regard the risks, if any, of developing oral cancer from use of mouthwashes containing alcohol as insignificant and actually endorse certain mouthwash products containing alcohol, which have been clinically proven to control plaque and gingivitis. Nevertheless new evidence from mucosal permeability studies demands further research on the actual risks, and as Professor Johnson highlighted, it is always prudent to remember that absence of evidence for a particular effect is not evidence for the absence of that effect.