Clinical studies have shown that chewing sugarless gum for 20 minutes following meals can help prevent tooth decay. The chewing of sugarless gum increases the flow of saliva, which washes away food and other debris, neutralizes acids produced by bacteria in the mouth and provides disease-fighting substances throughout the mouth. Increased saliva flow also carries with it more calcium and phosphates to help strengthen tooth enamel.
The only varieties of gum with the ADA Seal are sugarless. They are sweetened by non-cavity causing sweeteners such as aspartame, xylitol, sorbitol or mannitol. Of course, chewing sugar-containing gum increases saliva flow, too, but it also contains sugar which is used by plaque bacteria to produce decay-causing acids. Further research needs to be done to determine the effects of chewing sugar-containing gum on tooth decay.
Don't let chewing sugarless gum replace brushing and flossing. It's not a substitute. The ADA still recommends brushing twice a day with fluoride toothpaste and cleaning plaque from between your teeth once a day with dental floss or other interdental cleaners.