Which PubMed search string would most specifically identify studies on the effect of water fluoridation on caries rates?

Using quotation marks around 'Water fluoridation' forces the database to search for that exact phrase, ensuring results include the specific intervention (community water fluoridation) rather than articles that separately mention 'water' and 'fluoridation.' The AND operator then limits results to those also mentioning 'caries.' Without quotation marks, 'water AND fluoridation AND caries' would retrieve articles where these three words appear anywhere in the text but not necessarily in the phrase 'water fluoridation.' This is an important principle of evidence-based literature searching.