Researchers from the Osaka University Graduate School of Dentistry in Japan previously demonstrated that oolong tea extract, when added to drinking water, reduced plaque accumulation and inhibited the development of experimental dental caries in rats.
To test the theory on humans, the researchers enrolled 31 volunteers and professionally removed dental plaque on the participants' tooth surfaces. The subjects were asked to refrain from drinking tea, coffee, and alcohol for four days. During that period half of the group drank only oolong tea and the other half drank only water at every meal (at least 200 mL each time) and before sleeping (at least 100 mL).
At the fourth day, staining with erythrocin was used to evaluate the degree of plaque accumulation on participants' teeth. The following week the tea- and nontea-drinking groups were switched and the same protocol followed.
At the end of two weeks, the results showed the plaque indexes of subjects who drank oolong tea in each session were significantly lower (p < 0.01).
Oolong tea polyphenols appear to help prevent dental caries by inhibiting the function of glucosyltransferases, which play a key role in Streptococcus mutans, a primary causative agent of dental caries in humans, the researchers noted.
"We concluded that drinking oolong tea is a useful means of inhibiting dental plaque formation," they wrote.
More research needed
Polyphenols, micronutrients found abundantly in plants such as blueberries and black tea, are valued for their antioxidative properties, and substantial research has evaluated their role in preventing diseases such as cancer and cardiovascular disease.
The role of polyphenols in helping to prevent caries has not been as extensively examined, but previous studies have shown benefits with polyphenols from black tea, for instance. More recent studies have suggested benefits from polyphenols in red wine and cranberries.
A review of scientific evidence supporting the efficacy of cranberry polyphenols to prevent and/or treat diseases of the mouth indicated that, similar to the theories on oolong tea, certain properties also inhibit the formation of biofilms by S. mutans and S. sobrinus, and the adhesion of coaggregation of some oral species of Streptococcus (Journal of the Canadian Dental Association, 2010;76:a130).
In addition, polyphenols isolated from cranberry juice "appear to have potential for preventing and/or treating dental caries and periodontal disease," the authors wrote. More research is needed to determine, among other things, how to best isolate the polyphenols from acidic vehicles such as juice, or even tea with sugar, which would clearly be counterproductive to improving dental health.
In the meantime, some of the most traditional practices for dental caries prevention remain the most reliable, said Matthew Messina, DDS, spokesperson for the ADA and a private practice dentist based in Fairview Park, OH.
"I'm always open to new research that may offer suggestions for patients to avoid dental decay, and everyone would like there to be an easier way (just drink this or eat that), but brush, floss, and see your dentist is still the best," he said. "It's not sexy, but it works."
From a nutritional perspective, an effective approach should still focus on avoiding the sugary foods and beverages that are well-known to compromise dental health, Dr. Messina added.
"Bacteria in the mouth burn sugar, and the byproduct of their metabolism is acid. That acid dissolves tooth enamel, weakening it and causing cavities," he said. "We break this cycle by reducing the number of bacteria by brushing and flossing, reducing the availability of sugars, and strengthening enamel, with fluoride."
Anything that helps break this cycle at any point can be beneficial, he added, "but I still remain a believer in the tried and true methods, and I believe that anything in moderation from a diet perspective can be managed with good oral hygiene."
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