This article has such a bad headline.

The important thing to note here is that this review is looking for the impacts of fluoridation since the 1970s. The evidence remains clear that fluoridation is better than nothing at preventing cavities! The question at hand is whether it's still important now that we have widespread adoption of fluoride toothpaste.

This Cochrane study concludes, as many Cochrane reviews do, that there's not yet enough high quality evidence to answer this question.

The takeaway here shouldn't be the absurd headline that "fluoridation may not prevent cavities," it should be "we should study how effective fluoridation is now that we have added other successful interventions."