Probably not on its own. The only xylitol product with decent evidence is fluoride toothpaste with 10% xylitol added — over 2.5 to 3 years, it may cut cavities about 13% compared with the same toothpaste without it. For gum, mints, and syrups, the trials are too thin to say.
What the research found
In 2015, Cochrane reviewers gathered every trial of xylitol products for preventing tooth decay: ten studies, 5,903 people. The one product with evidence worth reporting was the toothpaste — the 13% figure above, from 4,216 children, rated low-quality evidence. For the products xylitol is actually famous for — gum, mints, lozenges — the evidence was insufficient to show an effect either way.
Xylitol's reputation comes largely from Finnish chewing-gum studies in the 1980s, which reported big reductions. Those studies built the field, but their designs — small groups, no blinding, school-based assignment — wouldn't clear today's bar, which is why the Cochrane review leaned on the newer, stricter trials.
The mechanisms are real, just modest. Plaque bacteria can't turn xylitol into acid, so every mint sweetened with it is one that isn't feeding them sugar. And chewing itself stimulates saliva — the mouth's own repair system. Displacement and saliva are honest benefits; they're not the same thing as proof of prevention.
Where the evidence stops
The trials that showed effects used xylitol in grams per day, spread across several sittings — more than casual use. No trial shows gum or mints alone preventing cavities, and nothing about xylitol treats decay that already exists. If you enjoy gum or mints, xylitol-sweetened is the sensible swap. If you're buying them to treat your teeth, the evidence isn't there yet.
See a dentist if you're chewing gum at a specific tooth — a spot that aches or catches sweets isn't a gum decision, it's an exam.