Traditional literature reviews use informal, unsystematic and subjective methods to collect, analyze, and interpret results from studies.  Such reviews may have issues with biases, and overestimation of the value of the studies.  Critical appraisals and systematic reviews have defined methods to collect, and analyze results of studies in order to reduce bias.  These higher level reviews are important tools for researchers and clinicians.  Many of the methods of systematic research synthesis were developed in the 1960, and are now driven by the Cochrane Collaboration. 

A systematic review is an evaluation of the evidence using clearly formulated topics that uses organized and explicit methods to identify, select, and critically appraise relevant research.  With regard to clinical trials to determine efficacy of procedures to prevent or arrest ECC, systematic reviews can resolve controversies between conflicting findings, and provide a reliable basis for decision making.