Sugar-Free Gum Helps Prevent Cavities Cleans and protects teeth. Helps prevent cavities. So say the most popular brands of sugar-free gum. But do their claims stand up to scrutiny? Many brands contain an additive called xylitol, a natural sweetener known to fight cavity-causing bacteria. In practice, though, it's not clear that xylitol has much impact. Some research suggests that while sugar-free gum does prevent cavities, xylitol per se is not responsible. Instead, it is the act itself of chewing gum that seems to prevent cavities. One new study, published this month in The Journal of the American Dental Association, seems to confirm this. The largest and most thorough look at the subject to date, the study tracked 691 adults recruited from dental clinics around the country for three years. The subjects were randomly assigned to groups consuming xylitol lozenges five times a day or a similar tasting placebo. Ultimately, those who received the xylitol had no statistically significant reduction in cavities, a finding that came as a surprise, said Dr. James D. Bader of the University of North Carolina at Chapel Hill. "We assumed there was a reasonably good chance that xylitol was going to be effective," he said. While xylitol itself may not be so protective, the increased salivary flow caused by chewing gum may be beneficial, as it rinses away plaque and acid. And chewing sugar-free gum beats chewing gum made with sucrose, which is definitely detrimental, Dr. Bader said. There is evidence that sugar-free gum reduces cavities, though that may have nothing to do with the gum's additives.