Dental techniques have improved greatly in the past few years, but once teeth have been damaged by cavities they can never be restored to their original condition. It is of the highest priority, therefore, to prevent cavities from developing in the first place. By the end of the 19th century, it had been determined that cartes are caused by cariogenic bacteria. The cariogenic bacteria first produce non-watersoluble glucan from sugar or other foods, and this glucan adheres to the tooth enamel as hard plaque. Next, they feed on sugar to generate acids such as lactic acid in the plaque. These acids then dissolve the tooth enamel. That in brief is the mechanism of cavity production. To prevent cavities it is necessary, then, to keep plaque off the teeth by hrushing an important tool in good dental hygiene. But according to experiments by Dr. Hattori(#15) green tea catechin can suppress the process (glucosyl transferase) by which cariogenic bacteria create glucan.Other experiments by Dr. Sakanaka(#16) have verified that green tea catechin can destroy cariogenic bacteria. That is, it is antibacterial. Clearly, then, green tea catechin not only suppresses the formation of plaque by cariogenic bacteria but also kills the bacteria themselves.
It has been known for some time that small amounts of fluorine can strengthen teeth and help prevent cavities. For this reason, many cities add fluorine to their drinking water. Green tea, however, contains natural fluorine and is thought to help prevent cavities. That may explain those reports that show a reduction in cavities among grade school children who drank green tea after lunch.
Halitosis or bad breath embarrasses many people. It is caused by a number of bacteria that flourish in the mouth. Green tea can also kill other oral bacteria besides those causing cartes. It has, therefore, some ability to prevent bad breath by destroying the cause of bad breath. Why not enjoy gleaming white teeth and a fresh breath by drinking green tea?

(#15) M. Hattori et al., Chem. Pharm.. Bull., 38, 717 (1990).
(#16) S. Sakanaka et al.. Agric. Biol. Chem., 53, 2307 (1989).