Xylitol is a natural sugar alcohol that people can use just like regular sugar. It even comes in granules. However, there is one major difference: Unlike most sugars, xylitol stops the growth of bacteria that can cause cavities. Mouth bacteria don't seem to like xylitol all that much. With less sugar to feast on, the bacteria in the mouth, and especially on teeth, diminish, creating less plaque and acid [source: California Dental Association].
Many products, including gum and mints, contain xylitol. Dental experts recommend using these products up to five times a day [source: California Dental Association]. So if you don't have access to your toothbrush, chew a piece of gum with xylitol for a few minutes after lunch instead; it can help prevent cavities just the same.