Which study design provides the highest level of evidence in evidence-based dentistry?

In the evidence hierarchy, a systematic review with meta-analysis occupies the highest level. It synthesizes data from multiple high-quality RCTs using rigorous, pre-specified methods to reduce bias in study selection, data extraction, and analysis. The statistical pooling of results in a meta-analysis increases statistical power and precision of effect estimates. Below it (in descending order) are: individual RCTs, cohort studies, case-control studies, case series, case reports, and expert opinion. For clinical decision-making, systematic reviews and meta-analyses provide the most reliable estimates of treatment effects.