Research has shown that “Xylitol consumption decreases counts of mutans streptococci.” However, the method of action isn’t understood as well. Researchers wanted to better understand the mechanism behind xylitol’s ability. They found, “Both xylitol and erythritol can decrease polysaccharide-mediated cell adherence contributing to plaque accumulation through a mechanism not dependent on growth inhibition.”
Söderling, E. M., & Hietala-Lenkkeri, A.-M. (2010). Xylitol and erythritol decrease adherence of polysaccharide-producing oral streptococci. Current Microbiology, 60(1), 25–29.
