SAN DIEGO -- The latest weapon to prevent cavities is a pack of gum with a bacteria-fighting ingredient.

"Now, we finally have something that's really, really simple. It's really, really easy and it's really, really cheap," said Margaret Alisa Hardardottir, who has had frequent visits to her dentist because of cavities.

Chewing gum containing xylitol, a natural sugar from the birch tree, can help eliminate bacteria that lead to cavities.

"It's too complex of a sugar for the bacteria to eat, so essentially the bacteria is starved and die in the mouth," said Dr. Jeffrey Gray of Gray & Williams Dental Care.

Hardardottir is cavity-prone, even though she cleans her teeth to perfection.

"It was never enough to just floss and brush," said Hardardottir.

She is not alone, said Gray. About 10 percent of adults continue to have cavities in spite of religious hygiene, according to Gray.

"No matter how well they clean their mouth, brush their teeth, floss, rinse or do everything else they can, the bad bacteria in some people's body chemistry builds up, and that causes them to get cavities no matter what happens," said Gray.

Hardardottir started chewing gum sweetened with xylitol twice a day a few months ago.

"Once you get the bacteria down to a lower level, it has a hard time coming back up," said Gray.

A handheld test can measure the amount of harmful bacteria on teeth. Hardardottir took a quick swab for her teeth and passed the test. She said she thinks it is because of the chewing gum with xylitol.

Dentists have known its cavity-preventing effects for years, but now many stores carry most chewing gum and mint products with xylitol.