Dental Caries
Drinking green tea is recommended to help prevent or even reverse the effects of a host of maladies, including cancer, autoimmune disorders and metabolic syndrome. The sub-class of polyphenols called catechins, found in green tea. They are effective antioxidants and have antibacterial properties. It only goes to reason that green tea benefits your mouth as well.
You probably know these as “cavities”. They are the little holes in our teeth that cause us grief and cost us money. Caries are caused by acids produced by several different species of bacteria. In a study published in 2009 researchers reported that polyphenols in green tea interfere with the ability of bacteria to produce plaque necessary to attach to tooth surfaces.1 The primary bacteria involved is Streptococcus mutans. Other microorganisms, Lactobacilli and actinomycetes, also contribute to plaque formation but there is little published information about their susceptibility to green tea.
Plaque
By slowing plaque production, less acid is produced by bacteria and tooth surface erosion is reduced leading to fewer dental caries. In the study mentioned above, Streptococcus mutans was treated with green tea in vitro (in the laboratory).1 Researchers simulated a tooth surface with saliva-coated synthetic beads. In the presence of green tea polyphenols S. mutans cell membranes were altering, making the bacteria less able to adhere to the synthetic tooth surfaces. It is important to note that the antibacterial activity only occurred when streptococcus was in direct contact with green tea.
Antibacterial properties of green tea in the mouth
The growth and survival of S. mutans is also reduced by green tea polyphenols in the sub-class of catechins. There are 8 different catechins in green tea that are concentrated enough to be effective. Epigallocatechin gallate (EGCG) is the catechin in the highest concentration and has the most effective action on the bacteria.
One method of action is to inhibit the production of an enzyme necessary for streptococcus to thrive. Published results show that the catechins can act on the bacteria either alone or in various combinations. Otake and others found a concentration of 167 mg EGCG per liter inhibited streptococcal growth by 91%.2 A study published in 1990 reported a 50% reduction in streptococcal growth at a concentration of 450 mg EGCG per liter.3
Another mechanism is that green tea prevents enzymes that turn starch into sugar from acting on food while it is in the mouth. Zhang and Kashket conducted an experiment where test subjects ate soda crackers then rinsed with black tea, green tea or water for 30 seconds.4 They observed up to a 70% reduction in the conversion of starch to sugar in the mouth following rinsing with the teas.
These findings are significant since tooth decay is not treated with antibiotics. Results on the amount of green tea required to adversely affect streptococcus vary. According to Hamilton-Miller, consensus is that “cup of tea” concentration inhibits and often kills streptococcal bacteria.5 A typical cup of tea contains between 0.5-1.0 g catechins per liter of brewed tea.6
Perhaps in the near future we’ll be using toothpaste, mouthwash and dental floss enriched with green tea extracts.
1Anti-cariogenic effects of polyphenols from plant stimulant beverages (cocoa, coffee, tea). Ferrazzano, GF; Amato, I; Ingenito, A; De Natale, A; and Pollio, A. Fitoterapia. 2009. 80(5):255-62. Epub 2009 May 3.
2Anticaries effects of polyphenolic compounds from Japanese green tea. Otake, S; Makimura, M; Kuroki, T; Nishihara, Y and Hirassawa, M. Caries Res. 1991. 25: 438-443.
3Effect of tea polyphenols on glucan synthesis by glucosyltransferase from Streptococcus mutans. Hattori, M; Kusumoto, IT; Namba, T; Ishigami, T and Hara, Y. Chem Pharm Bull. 1990. 38: 717-720.
4Inhibition of salivary amylase by black and green teas and their effects on the intraoral hydrolysis of starch. Zhang, J and Kashket, S. Caries Res. 1998. 3: 233-238.
5Anti-cariogenic properties of tea (Camellia sinensis). JMT Hamilton-Miller. J Med Microbiol. 2001. 50:299-302.
6Antibacterial substance in Japanese green tea extract against Streptococcus mutans, a cariogenic bacterium. Sakanaka, S; Kim, M; Taniguchi, M and Yamamoto, T. Agr Biol Chem. 1989. 53: 2307-2311.
