In traditional research, the "level of significance" refers to the probability value used to reject the null hypothesis. In evidence-based research, a similar term, "the level of evidence" refers to the quality of the published report that is analyzed critically in the context of a systematic review. A systematic review, the principal research tool of evidence-based dentistry, is distinct from a classical narrative literature review in that it is focused to examine the strengths and weaknesses of the research methodology, design and data analysis of each report included in the review. A systematic review is very clearly defined, and sets out to find what evidence there is for prescribing a particular intervention for a given patient. Evidence-based recommendations are grounded on systematic reviews, and the evaluation of systematic reviews in a given domain of dentistry is critical for the successful implementation of evidence-based dental practice. In the context of sealants, the evidence indicates that the intervention is effective in preventing dental decay on the molars and premolars of susceptible children and adolescents (Level of evidence: II-1). The preventive effect for second-generation sealants ranges from 33 percent to 71 percent. The median preventive effect is higher when sealants are reapplied, compared to a single application, because sealant effectiveness decreases over time. The majority of studies have focused on molars, and fewer studies have examined the preventive effect of sealants on premolars. In this paper, the authors have developed evidence-based recommendations for the use of sealants by discussing the level of evidence and, when applicable, the number needed to treat (NNT) and the prevented fraction (PF), two fundamental criteria in evidence-based dental practice.