Cynthia R. Biron, RDH
Studies have shown that people who drink large quantities of alcohol daily have an increased incidence of oral cancer. This has raised the question, "Does alcohol-containing mouthwash also cause cancer?" What makes the research a real challenge is that most of those who do drink alcoholic beverages use mouthwash daily to hide related breath odors. In addition, many smokers or users of tobacco products rinse with mouthwashes frequently to hide their "tobacco" breath. Tobacco products, of course, also increases incidence of oral cancer.
So the only studies that could really be valid in evaluating the role of alcohol-containing mouthwash as a causative agent in oral cancer are those studies which have carefully screened patients to ascertain that:
- They did not use alcohol or tobacco daily.
- They did use alcohol-containing mouthwash daily.
Furthermore, the oral cancer associated with alcohol use has not been necessarily from the alcohol itself, but other products in the alcoholic beverages such as urethane. Urethane is not an ingredient in alcohol-containing mouthwashes.
Why was the question posed?
It would only make sense that there could be a correlation between alcohol-containing mouthwash and oral cancer based on the higher incidence of oral cancer among consumers of alcoholic beverages. Manufacturers of alcohol-free mouthwashes, of course, often focus on this correlation. They inform dental professionals and consumers that the mouthwash of choice should be their product, since it contains "no alcohol."
They cite invalid studies to prove the point. Astute dental professionals who did a critical review of such literature found that few of the available stud°ies met basic methodologic principles of case-control design. Methodologic criteria that define a case-control study of acceptable epidemiologic quality for this research would need to include:
- Cancer confirmed from biopsy reports.
- Incident cases.
- Cases that were population-based.
- Controls with equal exclusions.
- Controls that were population based.
- Patients who had used mouthwash before cancer diagnosis.
- Elimination of subjects who had used tobacco, alcohol, or both.
Of seven case-control studies reviewed, odds ratios ranged from a beneficial effect of 0.82 for use of any mouthwash to an increased risk of 2.5 with the highest exposure. Only one small study met all seven criteria. Of the other studies, one met four of the criteria; three studies met three; and two studies met only two of the criteria.
Dr. Samuel Shapiro and others summed it up nicely in the following quotes taken from the American Journal of Epidemiology (1996;144:1091-1095): "When there is clear evidence of uncontrolled confounding due (to underascertainment), we argue that a causal inference for associations of low magnitude is not justified. There are many studies in which it is claimed that, simply because a confounder has been measured and adjusted for, it has been adequately controlled. That claim may not be tenable if there is material underascertainment of the confounder at issue. As illustrated here, such underascertainment may produce antifactual association.
"What`s it all mean? You`ve gotta be extra careful with weak association epidemiology (i.e. studies that report relative risks under 2.0 or increases in risk of less that 100 percent). Now, can Listerine kill the germs that cause bad epidemiology?"
The FDA and the ADA have concluded that alcohol-containing mouthwashes have not been proven to increase the incidence of oral cancer. The ADA Council on Dental Therapeutics suggests that all patients use any ADA-approved mouthwash, as recommended by their dentists.
Other concerns with alcohol-containing mouthwash
Alcohol-containing mouthwash is not recommended for children, since they tend to swallow it rather than rinsing and expectorating as adults do. In addition, children using other products such as home fluoride rinses should be monitored closely to prevent fluorosis from developing. Alcohol-containing mouthwashes have a safety cap unless the product is "senior friendly."
Alcoholics Anonymous or other substance-abuse clinics instruct their clients to refrain from using any product containing alcohol, including mouthwashes, cold remedies, or food products. No significant studies indicate that alcohol-containing mouthwash has been the sole cause of reforming alcoholics relapsing back into their addiction. So do not panic if you ask a patient to rinse with Listerine Cool Mint and find out later that the patient is a reforming alcoholic. It probably will not result in their heading straight out for a drink after the prophylaxis appointment. If patients tell you from the outset that they cannot or refuse to rinse with alcohol-containing mouthwashes, by all means, respect their wishes.
With all due respect to those who are dedicated to helping addicted individuals, we support your efforts and theories. For clinicians, there are other concerns. Antimicrobial rinses are of paramount importance before ultrasonic instrumentation in the prevention of bacteremias in those who are immunocompromised or predisposed to bacterial endocarditis. This leads to more reasons for using alcohol-containing antimicrobial mouthwashes that have received the ADA Seal of Acceptance.
Reasons to use alcohol-containing mouthwashes
Mouthwashes with phenolic compounds that contain 21 to 26 percent alcohol and have completed the associated clinical trials are awarded the ADA Seal of Acceptance for their ability to statistically and significantly reduce plaque and gingivitis. They do not require a prescription for purchase. Chlorhexidine gluconate is the generic mouthwash similar to Peridex or PerioGard, which are prescription mouthwashes. All contain 11.6 percent alcohol.
The over-the-counter phenolic compounds are preferred by most clinicians and patients. They are much less expensive than the chlorhexidine products, do not have the adverse effects of staining, and the 10 percent increased production of calculus. Other antimicrobial mouthwashes have not received the ADA Seal of Acceptance because they have not been shown to reduce plaque and gingivitis to a significant degree. These include Cepacol, Viadent, Plax, and OxyRich, as well as a host of others.
Alcohol is not the ingredient that actually kills the bacteria; it acts as an agent to solubilize the essential oils present in the phenolic compound antimicrobial mouthwashes, including thymol, eucalyptol, menthol, and methyl salicylate. When patients are not maintaining oral health through mechanical removal of plaque, phenolic-compound, antimicrobial mouthwashes are indicated. In acute gingivitis, chlorhexidine is indicated.
Subgingival irrigation with Listerine, for example, has been shown to reduce bacteremia-inducing pathogens by more than 80 percent. This should be part of the protocol for patients at risk for bacterial endocarditis, since 12 percent of the patients with adequate prophylactic, antibiotic blood levels during oral prophylaxis still develop endocarditis. The American Heart Association suggests that gingival crevicular irrigation with antimicrobial mouthwashes be used in conjunction with the prophylactic antibiotic regimen established by the AHA.
A study compared aerosolized bacteria from antimicrobial pre-rinsing and nonpre-rinsing ultrasonically scaled patients. After a 40-minute ultrasonic scaling period, there was a 93.6 percent reduction in aerosolized bacteria. All hygienists should have their patients pre-rinsing before ultrasonic scaling. We must prevent the contraction of diseases from bloodborne pathogens that are suspended in aerosols ? not only for ourselves, but our coworkers and all patients brought into our operatories.
Both types of antimicrobial mouthwashes, phenolic compound and chlorhexidine, have been proven effective in reducing Candida Albicans population, as well as mucositis associated with immunosuppresive therapy. Both mouthwashes have also been shown to be effective in aiding the healing process of postsurgical patients. The alcohol content is not detrimental to wound healing. Chlorhexidine has reduced drug-induced gingival hyperplasia by 20 percent for one year or more.
There are numerous reasons to use and recommend alcohol-containing mouthwashes. They have been proven safe and effective, do not cause oral cancer, and decrease a vast number of pathogens in the oral cavity (more importantly, in the air we breathe where we practice dental hygiene).
References are available upon request by sending e-mail to [email protected]
Cynthia R. Biron, RDH, is chair of the dental hygiene program at the Tallahassee Community College. She is also a certified emergency medical technician.
A closer look at urethane
Alcoholic beverages have been shown to increase the incidence of oral cancer; pure alcohol has not - at least not in studies conducted using ethanol with laboratory animals and humans. This led researchers to believe that studies about the chemical constituents of alcoholic beverages needed to be conducted, determining which chemicals were associated with oral cancer. As a result, the chemical that has been associated with oral cancer is urethane.
When urea reacts with ethyl alcohol after fermentation, urethane (ethyl carbamate) is formed. Studies have suggested that the enzyme urease be added to fermented drinks to reduce the levels of urethane. American manufacturers have determined that "acceptable" levels of urethane in beverages be at 15 ppb for table wines, 60 ppb for fortified wines, and 125 ppb for distilled beverages. While domestic beverages maintain that standard, imported beverages do not always meet such standards. Some fruit brandies contain urethanes ranging as high as 255 ppb.
The FDA has advised countries that export alcoholic beverages to our country to meet our standards on accepted levels of urethane. To date this has not been mandated, and Americans continue to purchase and consume alcoholic beverages with high urethane levels.
No available mouthwashes, however, contain urethane, even if they do contain alcohol, simply because there is not a fermentation process in the production of mouthwash.