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Dispel the Myths

WHILE MISCONCEPTIONS ABOUT THE SAFETY OF ALCOHOL-CONTAINING MOUTHRINSES CONTINUE TO CIRCULATE, SCIENTIFIC EVIDENCE DEMONSTRATES NOT ONLY THEIR SAFETY, BUT THEIR EFFICACY AS WELL. By Ann Eshenaur Spolarich, RDH, PhD, and JoAnn R. Gurenlian, RDH, PhD


 

Despite the large number of published papers documenting the safety and efficacy of antimicrobial mouthrinses, dental professionals continue to struggle with product recommendations because of concerns about toxicity and other adverse events. Negative perceptions regarding mouthrinse safety are often perpetuated by incorrect and misrepresented "factual" information that has been republished for decades, despite a lack of evidence to support these claims and the presence of research that disputes these concerns. The safety of alcohol-containing mouthrinses continues to inspire debate for many clinicians who have become trapped in this maze of misinformation.

WHY DOES ALCOHOL APPEAR IN MOUTHRINSES?

All mouthrinses that have received the American Dental Association (ADA) Seal of Acceptance for safety and efficacy as antiplaque and antigingivitis agents contain alcohol. Alcohol is added to mouthrinse products to solubilize the active ingredients, making them biologically active. Alcohol is also used to dissolve the flavoring agents and as a preservative. Alcohol is not the biologically active ingredient in any cosmetic or therapeutic mouthrinse.

Essential oil mouthrinse contains 26.9% alcohol in the traditional product and 21.6% alcohol in the flavored products; 0.12% chlorhexidine gluconate mouthrinses generally contain 12.6% alcohol; and traditional cetylpyridinium chloride products contain alcohol levels ranging from 6% to 18%. There are two alcohol-free products that contain a higher concentration of cetylpyridinium chloride (0.07%), neither of which carries the ADA Seal.

IS ALL ALCOHOL THE SAME?

Commercial mouthrinse formulations contain pharmaceutical alcohol, which is pure ethanol. Alcoholic beverages contain ethyl alcohol, which is produced through the fermentation of vegetables, grains, or fruits, and is found in products like beer and wine. Distilled beverages, such as whiskey and vodka, are created by collecting the dilute solutions of ethanol that are produced through the fermentation process.

TOXIC EFFECTS OF ALCOHOL INGESTION

The toxic effects of ethanol are associated with its primary metabolite, acetaldehyde, and secondary metabolite, acetic acid. Acetaldehyde accumulation contributes to the feeling of a "hangover" including nausea, vomiting, dizziness, and headache. Acute alcohol poisoning is associated with alcohol overdose (toxicity), which can lead to central nervous system depression. Signs and symptoms of acute toxicity include loss of consciousness, drop in blood pressure, decreased body temperature, and respiratory depression. Without intervention, acute alcohol poisoning can be fatal.1 

Chronic alcohol exposure is associated with more than a dozen diseases, including numerous cardiovascular disorders, neurological impairments, liver disease, and gastrointestinal complications.2 Fetal alcohol exposure is associated with pregnancy and delivery complications, birth defects, and intellectual and developmental disabilities.3 

There is no evidence that the chronic topical use of alcohol-containing mouthrinses contributes to toxic systemic effects because these products are not swallowed or ingested in any measureable quantity.

IS ALCOHOL CARCINOGENIC?

Alcoholic beverages contain numerous additives and chemicals that are known to cause cancer, one of which is urethane.4 These chemicals arise from the fermentation and distillation processes in which yeasts and plants convert pyruvate into acetaldehyde, which is then converted to ethanol, captured as the by-product in alcoholic beverages.

Congeners are substances that are also produced during fermentation, contributing to the taste of both distilled and nondistilled alcoholic beverages. However, congeners are considered impurities that contribute to ethanol toxicity and include fusel alcohols (highly toxic), acetone, aldehydes (eg, propanol and glycol), and acetaldehyde. Congeners are also implicated in carcinogenesis.5 

Long-term exposure to alcohol is associated with cancer of the mouth, throat, esophagus, liver, colon, and breast. Risk for developing cancer increases with increased alcoholic beverage consumption.6 

ALCOHOL AND ORAL CANCER

Ethyl alcohol is metabolized to acetaldehyde, which can be toxic to oral tissues, causing DNA damage in the cells, leading to cell mutation and carcinogenesis. This is why chronic alcoholic beverage consumption is a leading risk factor for oral and pharyngeal cancers.2 

Alcohol exposure also increases the permeability of oral mucosal cell membranes, allowing cellular DNA to become exposed to toxins and other carcinogens.7,8 This explains why many cases of oral cancer are observed in chronic drinkers, chronic smokers, or in people who drink socially and also smoke.9 Laboratory data that demonstrate increased cell permeability are based on exposure of the cells to large amounts of alcohol and exposures of 1 hour or longer, which reflects what is observed during social drinking.7,9 

Oral bacteria have the ability to convert alcohol to acetaldehyde, and the amount of acetaldehyde produced is associated with poor oral hygiene.9,10 About 15% of people with oral cancer have no known risk factors, thus, their cancer may be related to infections associated with viruses (human papillomavirus), fungi (Candida albicans), and possibly by bacteria via acetaldehyde formation. 10 Certain species of oral bacteria may locally produce enough acetaldehyde to cause DNA damage, leading to cellular mutation and hyperproliferation of the oral epithelium.11,12 Yeasts have also been shown to produce acetaldehyde from alcohol.13 

Dental professionals must remember that oral flora demonstrate multiple, pivotal roles in oral cancer initiation by cellular mechanisms other than acetaldehyde formation. This must be kept in mind when considering possible etiologic factors for cancer in their patients.10 

Pure ethanol (pharmaceutical alcohol) has never been found to cause cancer in any lab - oratory (cellular, animal) or human model.5,9 Pure ethanol is not a carcinogen by itself nor does it contain any added carcinogens.14 The discussion about the role of alcohol-containing mouthrinses and oral cancer has continued for more than three decades. Early studies examining the relationship between alcohol-containing mouthrinses and oral cancer yielded conflicting results.5,15–21 Critical analysis shows numerous methodological problems with these studies, including failure to demonstrate a dose-response relationship based on frequency and/or duration of mouthwash use; failure to control for alcohol ingestion and tobacco use; lack of a biologic or scientific explanation for inconsistent results; and inclusion of other cancers of the head and neck, including pharyngeal cancer.4,22,23 

Recent investigations have shown that the use of an alcohol-containing mouthrinse leads to short-term formation of acetaldehyde that is detectable in saliva for up to 10 minutes. 24–26 However, this increase is short-lived, as salivary acetaldehyde levels drop to low levels within 5 minutes, presumably due to salivary ethanol metabolism.26 Salivary acetaldehyde levels after rinsing with an essential oil mouthrinse were significantly lower than those seen after rinsing with an equivalent ethanol control. This might be explained by the effective antimicrobial activity of essential oils by killing the bacteria before they have the opportunity to metabolize ethanol to acetaldehyde, or that other ingredients in the mouthrinse stimulate salivary flow, which dilutes its level.26 Ingestion of alcoholic beverages also causes prolonged salivary levels of acetaldehyde.27 Clinicians should note that acetaldehyde is also found naturally in the body, as well as in many fruits, vegetables, and dairy and meat products.26 As such, it is not practical to account for all sources of exposure.

The topical exposure of oral mucosa to alcohol from mouthrinses is not comparable to consuming alcoholic beverages. Two or even three topical exposures of a 25% alcohol-containing mouthrinse, each lasting 30 seconds, seems unlikely to produce the same effect as chronic, habitual alcohol consumption. Assuming that the two- to three-times-daily rinsing with alcohol-containing mouthrinse is equivalent to consuming one to two alcohol-containing drinks per day, the current literature does not document a higher risk for oropharyngeal cancer with alcohol beverage consumption at this level.23 

Lachenmeier's group reports that "estimated lifetime cancer risk for twice-daily alcohol-containing mouthwash use (and including additional acetaldehyde exposure from other cosmetics) as being three to four cases per 1,000,000."24,28 "The risk of alcohol- containing mouthwash for public health appears very low compared to other routes of exposure to alcohol and acetaldehyde, so that priority for risk management actions should be placed rather on reducing alcohol consumption and smoking."28 

Two investigations performed by the Food and Drug Administration, in 1996 and 2003, concluded that there was no relationship between alcohol-containing mouthrinses and oral cancer.4,14,29,30 The ADA also states that there is no causal relation ship.30 Reviews of the epidemiologic evidence have failed to link use of alcohol- containing mouthrinses with oral cancer.31–34 Few studies have described why mouthrinse is being used, noting that it is often used to mask drinking and smoking behavior.34 Future studies need to control for smoking and alcohol use, and document reasons for, frequency and duration of use, and particular type of mouthrinse used.34 Table 1 provides the findings of the most recent metaanalysis of 18 epidemiologic studies of mouth - rinse use and oral cancer.34 

 
 

DOES ALCOHOL CAUSE ORAL DRYNESS?

A common misconception is that the use of an alcohol-containing mouthrinse would dry (desiccate) the oral mucosa. However, two published studies have shown that rinsing with an essential oil mouthrinse produced the exact opposite effect.

In a study of 19 women with Sjögren's syndrome, salivary flow rates were measured before and after rinsing with an essential oil mouthrinse and a control mouth rinse. Under exaggerated conditions (three rinses per day instead of the recommended two), post-rinsing salivary flow rates were 28.2% higher in those rinsing with an essential oil mouthrinse compared to the control.35 

A more recent investigation compared the effect of exposure to an alcohol-containing and a nonalcohol-containing mouthrinse on salivary flow and perceptions of dry mouth. Twenty healthy subjects were asked to rate their level of perceived dryness before and after rinsing. Then, subjects rinsed with either an alcohol-containing mouthrinse or a mouthrinse without alcohol. Salivary flow rates increased post-rinse for both subject groups. Subjects' perception of dryness was actually lower before rinsing with both products. There were no differences between rinsing with the alcohol-containing mouthrinse and alcohol-free mouthrinse in either objective (flow rate) or subjective (perception) measures of dryness.36 

HIGH-RISK PATIENT POPULATIONS

Essential oil alcohol-containing mouth - rinses are approved for use in children older than 12. The efficacy and safety of chlorhexidine in children under 18 have not been established. Due to the potential risk of alcohol ingestion, clinicians must assess the child's ability to swish and expectorate without swallowing prior to recommending use.

Patients with a history of alcohol abuse who are in recovery should be advised that the use of an alcohol-containing mouthrinse may induce relapse, and they should consult with their abuse sponsor before using an alcohol-containing mouthrinse. Manufacturers generally state that these products are contraindicated for use in patients either with or recovering from alcoholism.23 Alcohol- containing mouthrinses should also be avoided when patients are using disulfiram (Antabuse®), a drug used as a deterrent in alcohol recovery programs, or metronidazole (Flagyl®), an antibiotic. Concurrent use can produce nausea, vomiting, dizziness, and headache.23,37 

CONCLUSION

Antimicrobial mouthrinses can reach difficult- to-reach areas in the mouth, killing bacteria that mechanical methods may leave behind. By accessing all areas of the mouth, antimicrobial mouthrinses reduce salivary microflora and the overall microbial load, thereby reducing bacteria that would otherwise colonize to form oral biofilm. Strong clinical evidence based on studies of at least 6 months duration supports the safety and efficacy of chlorhexidine and essential oil alcohol-containing mouth - rinses, with weaker evidence supporting the use of cetylpyridinium chloride, to reduce supragingival plaque and gingi - vitis.38,39 Dental professionals should feel confident that it is safe to recommend alcohol- containing mouthrinses to designated patients for daily home use for the prevention and treatment of gingivitis. Claims of oral cancer associations or increased dryness are unsupported.

ACKNOWLEDGEMENTS

PHOTOCREDIT : RUSSELL KIGHTLEY/SCIENCE PHOTO LIBRARY

 

 

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From Dimensions of Dental Hygiene. April 2013; 11(4): 20–22, 24. 

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