Background: In recent years the early detection of such caries has gained importance, since it may avoid unnecessary dental tissue damage and allow minimally invasive dental treatment. A study is made of 5 systems for diagnosing caries: traditional visual and tactile methods, DIAGNOdent, VistaProof and CarieScan. Material and Methods: A prospective study was made in the Department of Stomatology, Dental Pathology and Therapeutics Teaching unit of the University of Valencia (Valencia, Spain), involving the analysis of 32 teeth (molars or premolars of both arches scheduled for filling or for use as posts in dental bridges) in 28 patients. The following caries diagnostic methods were applied: visual, tactile, DIAGNOdent (KAvo, Biberach, Germany), VistaProof (Dürr Dental AG, Bietigheim-Bissingen, Germany) and CarieScan (IDMoS Dental Systems, Dundee, Scotland, United Kingdom). Fissurotomy was subsequently performed for histological validation. Results: Visual inspection showed an area under the receiver operating characteristic curve (AUC-ROC) of 0.75, with a sensitivity and specificity of 0.75. Tactile diagnosis in turn showed AUC = 0.714, with maximum sensitivity (100%) and a specificity of 42.9%. DIAGNOdent (cutoff point 22.5) and VistaProof (cutoff point 1.1) showed AUC = 0.969, while CarieScan (cutoff point 21.5) presented AUC = 0.973. These latter three methods all had a sensitivity of over 92%. The specificity of DIAGNOdent was maximum, while that of CarieScan and VistaProof was 75%. Conclusions: The emergent methods in the diagnosis of caries (DIAGNOdent, VistaProof and CarieScan) yielded similar results, and in all cases proved superior to the traditional visual and tactile methods. DIAGNOdent was seen to be the most effective technique, followed by CarieScan and VistaProof.