Coffee beans, cavity-causing germs. (Biomedicine).

Coffee could be good for your smile. In a new study, compounds in coffee loosen the grip of bacteria that cause tooth decay.

Researchers from the Universities of Pavia and Ancona in Italy prepared coffees from beans of various origins and degrees of roast. They put the brews into test tubes containing saliva-coated hydroxyapatite, a compound in teeth. They also added Streptococcus mutans bacteria, which stick to teeth and cause cavities.

In the test tubes loaded with java, at least 40 percent fewer bacteria attached to the hydroxyapatite than in test tubes with no coffee. Some varieties of beans were more effective at thwarting the microbes when lightly roasted; other beans did a better job when dark roasted. Brews prepared from unroasted beans were least effective. African beans of the species Coffea robusta were slightly more effective than South American beans of Coffea arabica.

Separate tests suggest that several chemical components of coffee contributed to the effect, Gabriella Gazzani of the University of Pavia and her colleagues report in an upcoming issue of the Journal of Agricultural and Food Chemistry.--B.H.