This is a protocol for a Cochrane Review (Diagnostic test accuracy). The objectives are as follows: To undertake a series of Cochrane Reviews to establish the diagnostic accuracy of index tests for the detection and diagnosis of dental caries. We propose a new review for each identified method for the detection and diagnosis of coronal caries in children and adults (five reviews in total); and one new review of the comparative accuracy of the identified methods, used alone or in combination. Review 1. Visual or visual-tactile examination according to detailed criteria. Review 2. Radiography. Review 3. Fluorescence. Review 4. Electrical conductance. Review 5. Fibre-optic transillumination. Review 6. Comparative accuracy review which will bring together the results of these reviews in a review of the comparative accuracy of the identified methods. Additional statistical analyses will be undertaken using the extracted data from all eligible studies that have evaluated one or more methods. To undertake a series of Cochrane Reviews to establish the diagnostic accuracy of index tests for the detection and diagnosis of root dental caries, in adults. We propose the following new diagnostic test accuracy (DTA) review. Review 7. Diagnostic tests for root caries in adults. A single review for root caries will be completed due to a smaller volume of studies identified through a scoping search. The scoping search was completed during the grant application (January 2017) and interrogated MEDLINE only, in combination with existing systematic reviews of DTA for caries there is an anticipation that the visual, radiography and fluorescence reviews will each include over 100 studies (Bader 2002; Bader 2004; Gimenez 2013; Gimenez 2015; Schwendicke 2015). Where sufficient studies are available, each individual review (numbers 1 to 5) will include evaluation of comparative accuracy of different index test methods/approaches, for example visual to evaluate differences between measurement indices i.e. ICDAS, Nyvad, ERK and other caries detection indices. Aligned to the objectives listed above, the specific research questions answered through the suite of systematic reviews will include. What is the diagnostic test accuracy of different tests for different purposes (detection or diagnosis), in different roles (adjunct to visual examination or independent test), in different populations (children: primary/mixed dentition, adolescents: immature permanent dentition, or adults: mature permanent dentition), and when tested against different reference standards. What is the diagnostic test accuracy of each of the index tests compared to an appropriate reference standard for detecting and diagnosing initial stage decay on the occlusal and approximal tooth surfaces? Do measures of sensitivity and specificity for single tests differ from the sensitivity and specificity of tests used in combination? Is there a benefit to using more than one index test as opposed to a single test? What is the potential value of each index test at different positions in the clinical pathway? For example, 'disease-free' individuals could be 'screened out' on the basis of a clinical examination, whilst those with a suspicion of disease would receive an x-ray. What is the comparative diagnostic test accuracy of the different index tests?