Over-the-Counter Mouthrinses

By Stuart L. Fischman, DMD

Mouthrinses have traditionally been used for cosmetic purposes. Therapeutic products are now available, many of which are sold over the counter. Consumers rely on dental professionals for guidance in the selection of a mouthrinse. The various product categories are reviewed and criteria for patient and/or consumer selection are suggested.

Article copyright 1998 Journal of the California Dental Association.
Photographs copyright of the authors.

Freshening bad breath has been the traditional use for mouthrinses.1 The 1996 market for such products is estimated at $662 million. In addition to the traditional cosmetic types, therapeutic mouthrinses are now available.

The active ingredients of most mouthrinses include quaternary ammonium compounds, boric and benzoic acids, and phenolic compounds.2 Commercial sales of a rinse are closely related to taste, color, smell and the pleasant sensation that follows use. The pleasant sensation is often enhanced by the addition of astringents. Commonly used astringents are alum, zinc stearate, zinc citrate, and acetic or citric acids. Zinc salts have been added to mouthrinses as an antiplaque ingredient. Alcohol in the mouthrinse is used as a solvent and taste enhancer.

Halitosis

Breath, not health, is often the first priority where use mouthwash is concerned. Consumers most commonly use mouthrinses to chemically treat oral malodor. Almost two-thirds of all mouthwash users say they rinse mainly to freshen their breath; curbing plaque and gum disease are a distant second.3 Oral malodor has been a neglected research area. The first scientific symposium on halitosis research was not held until 1991. Identifying the cause of halitosis and developing an appropriate treatment plan can be difficult. Published studies have demonstrated that oral malodor usually derives from the mouth itself and may be reduced following oral hygiene. To motivate improvement in oral hygiene, dental professionals should advise patients that bad breath may result from microbial putrefaction within the mouth. Rosenberg4 notes that "bad breath is a cause of concern, embarrassment, and frustration on the part of the general public. Oral malodor, whether real or perceived, can lead to social isolation, divorce proceedings, and even 'contemplation of suicide.'"

Many things can help oral malodor, but nothing is completely effective against bad breath because the causes are too diverse. In addition to the bacteria that cause "morning breath," common causes of oral malodor include:

- Smoking, chewing tobacco and drinking alcohol;
- Aromatic compounds in foods such as garlic and onions, which enter the bloodstream, are carried to the lungs, then exhaled;
- Gum disease, especially when accompanied by bleeding gums; and
- Respiratory-tract infections, such as chronic bronchitis or sinusitis with postnasal drip.

Instead of relying totally on mouthwash to mask the problem, a person with chronic bad breath should be examined by a dentist and, possibly, a physician.

To combat odors from such divergent sources, many mouthwashes rely in part on their ability to cover odors with pleasant-smelling ingredients. This effect is often quite temporary. Even the best cosmetic mouthwashes give out fairly quickly. Breath tests taken one and two hours after panelists rinse typically fail to distinguish any products as particularly effective. On the other hand, breath freshening effects from mouthrinses that also have strong antiseptic activity persist longer than those relying solely on odor masking because these mouthrinses also affect the bacteria that produce malodorous compounds.

There are methods that permit the quantitative assessment of bad breath and therefore should be able to verify "breath freshening" claims.5 To determine the relative contributions of masking and antisepsis to overall anti-odor effectiveness of a product, it is necessary to simultaneously measure the odor of the mouth, the concentration of malodorous microbial metabolites in mouth air, and populations of oral odorigenic microorganisms in each subject while holding other factors constant.

Antiseptic mouthwash can be highly effective in depressing all determinants of oral malodor. While the effects of the treatments may differ in magnitude, the malodor determinants are well-correlated for all treatments at all times with one important exception: In the first sample taken after antiseptic mouthwash use, oral malodor was substantially less than predicted from volatile sulfur or bacterial levels.5 Analysis of these data demonstrates that re-odoration is important to the overall activity of the product for only about 30 minutes after treatment; and, at post treatment times of 60 to 180 minutes, the anti-odor activity of the product is due to its antimicrobial action.

Essential Oils

Listerine antiseptic, a combination of phenol-related essential oils, thymol and eucalyptol, mixed with menthol and methylsalicylate, is the first over-the-counter, or OTC, antiplaque and antigingivitis mouthrinse to be accepted by the ADA Council on Scientific Affairs.6 Listerine has been marketed for more than 110 years. Patients are directed to rinse twice daily with 20 ml of Listerine for 30 seconds, in addition to their usual oral hygiene regimen. Microorganisms do not develop a resistance to the antimicrobial effects of essential oils. Two generic versions of original Listerine have also been granted the ADA seal and are marketed under numerous trade names.7

In long-term clinical trials, Listerine has been shown to reduce both plaque accumulation and severity of gingivitis by up to 34 percent.6 Microbial sampling of plaque in these trials has demonstrated no undesirable shifts in the composition of the microbial flora. As with chlorhexidine, rinsing with Listerine per se is unlikely to be effective in treating periodontitis because the solution does not reach the depths of the periodontal pockets. Irrigation studies, using irrigator tips designed to deliver solutions subgingivally, suggest that Listerine may have some value as an adjunct to mechanical therapy.

Herbal Extract -- Sanguinarine

Viadent rinse and toothpaste each contain sanguinaria, an extract of the bloodroot plant. Several long-term studies of the toothpaste showed no significant plaque reduction. One six-month study in which subjects used both the toothpaste and mouthwash twice daily showed a 21 percent reduction in plaque and a 25 percent reduction in gingivitis.8

Quaternary Ammonium Compounds

This group of cationic surface active agents has been in use for many years. The most commonly used member of the group is CPC or cetylpyridinium chloride, the active ingredient in Cepacol. One six-month study reported a 14 percent reduction in plaque, accompanied by a 24 percent reduction in gingivitis. Scope and some generic mouthwashes also contain cetylpyridinium chloride.

Oxygenating Agents

Agents such as peroxides and perborates have been used in the short-term treatment of acute necrotizing gingivitis and pericoronitis. Several oxygenating rinses, such as those containing chlorine dioxide (e.g., Oxyfresh), are marketed as breath freshening agents. However, little scientific data demonstrating efficacy is available.

Fluorides

Some short-term studies indicate that stannous fluoride is a more effective antiplaque agent than sodium fluoride. Stannous fluoride (SnF2) used as a gel or rinse may provide a reduction in plaque and/or gingival inflammation. Contrary reports are found in the literature, and considerable reservation has been voiced on the efficacy of SnF2 as an anti-plaque/gingivitis agent.8 It may provide a significant anticaries benefit in special patient populations, such as those with orthodontic appliances, xerostomia or bulimia.

Surfactants

A detergent prebrushing rinse, Plax, contains sodium lauryl sulfate and sodium benzoate. There is a disparity in studies of the clinical efficacy of this product. A reduction in plaque has been reported in some studies, while others show no difference between the rinse and a placebo.8

Preprocedural Rinsing

For the dental professional, it may be important for patients to use a mouthrinse prior to aerosol-generating procedures. Unless an effective dry-field technique is used, the bacterial aerosol generated by a high-speed turbine in 30 seconds is roughly equivalent to the patient sneezing in the dentist's face. A study by Wyler9 and colleagues found that even a preliminary water rinse temporarily reduced the bacterial aerosol population by 61 percent, brushing alone by 85 percent, and an antibacterial mouthrinse by 97 percent. Fine10 and colleagues, using a simulated office visit model, showed that preprocedural use of an antimicrobial mouthrinse (Listerine) resulted in a 93.6 percent reduction in the number of viable bacteria in a dental aerosol produced by ultrasonic sealing. The effect of this reduction on actual disease transmission has not been determined.

Xerostomia Mouthrinses

Many people experience dry mouth (xerostomia) that can be traced to several possible causes, such as damage to the salivary glands following radiation therapy for head and neck cancer, Sjögren's syndrome, and the use of tranquilizing drugs, especially the tricyclic antidepressants. In such cases, the mucous membrane is continually dry and uncomfortable. To ameliorate the dryness, artificial salivas have been developed to be used ad libitum by the patient to moisten the mucous membrane.11

Because xerostomia is correlated with an increased caries incidence, the rinses usually contain fluoride as well as chemical compounds in concentrations that closely parallel those of saliva. The rinses that contain fluoride may, in reality, be remineralizing solutions. Several artificial salivas have been accepted by the ADA, among which are Glandosane, Moi-Stir, Salivart, and Xero-Lube.7

Biotene, a mouthrinse said to be alcohol-free, contains three antibacterial enzymes that kill bacteria found in oral infections and gum disease. It is marketed as "an orally balanced enzyme system for reduction of cavities, plaque and gum disease due to xerostomia." Biotene is not an artificial saliva and does not carry the ADA Seal.

Conclusion

In addition to the traditional cosmetic use, therapeutic mouthrinses are available. There are many OTC formulations with a variety of active ingredients, including quaternary ammonium compounds, boric and benzoic acids, and phenolic compounds. The conscientious dental professional should look to the contemporary literature for guidance in making recommendations.