"In 2013, the Cochrane Collaboration published a systematic review of the evidence on sealants. It assessed the results of 34 studies involving 6,529 children and adolescents. Some studies compared one sealant material with another, but 12 of the studies, with 2,575 total participants, compared outcomes of sealants versus no sealants. From these, the review concluded that sealants are effective in reducing cavities for at least four years after each application."
Read more: http://www.nytimes.com/2016/09/20/upshot/defending-your-childrens-teeth-and-dentists-the-value-of-sealants.html?_r=0