Abstract Objective. To assess the diagnostic accuracy of adjunct methods used to detect and quantify dental caries. Study design. A systematic literature search for relevant papers was conducted with pre-determined inclusion and exclusion criteria. Abstracts and full text articles were assessed independently by two reviewers. The study characteristics were compiled in tables and quality graded according to the QUADAS tool. The level of evidence for each diagnostic technology (fiber-optic methods, fluorescence methods, electrical methods) was based on studies of high or moderate quality according to the GRADE approach. Results. Twenty-five reports fulfilled the inclusion criteria. One study was of high quality, 10 were graded as moderate, while the remaining 14 reports were of low quality. Electrical methods (ECM) and laser fluorescence (DIAGNOdent) displayed sensitivities and specificities around 70-80% regarding occlusal dentin lesions with a mean Youden's index of 0.52-0.54. The mean accuracy of laser fluorescence for detecting enamel and dentin lesions was 0.68 and 0.91, respectively. The heterogeneity of the published reports hampered the analysis. Conclusions. There was insufficient scientific evidence for diagnostic accuracy regarding fiber-optic methods and quantitative light-induced fluorescence (+OOO). The electrical methods and laser fluorescence could be useful adjuncts to visual-tactile and radiographic examinations, especially on occlusal surfaces in permanent and primary molars, but evidence was graded as limited (++OO). No conclusions could be drawn regarding the cost-effectiveness of the methods. There is an obvious need to standardize study designs for in vitro and in vivo validation of the different methods.