Electrical resistance has been used over the years in various forms in an attempt to detect caries. It basically uses a change in resistance to indicate mineral content. It has been used for occlusal caries detection42, as well as for an in vitro and in vivo assessment of remineralization of lesions with toothpaste. Some difficulties existed and statistical significance was not seen, but the conclusions indicated that with modifications, "...electrical resistance measurements may be a means of comparing the remineralization performance of toothpastes." Even more recently, electrical resistance (using the Electric Caries Monitor – ECM) has been used in vitro in a comparison to transversal micro-radiography to measure remineralization (root lesion depth and mineral loss) with several fluoride treatment regimes. It appears ECM specificity is only 80%, which makes it inappropriate for clinical use at this time.43 Although not ready for clinical application at present, it does indicate alternative possibilities for measuring remineralization/demineralization of difficult to detect root surface lesions in the future.
In a 2013 publication by Twetman and colleagues44, the authors reviewed the available literature regarding adjunct methods for caries detection. They concluded: “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.”
Clearly there is a need to increase the sensitivity of our methods of caries detection while maintaining the highest level of specificity. Our desire is to be able to detect caries activity even before it is clinically or radiographically visible so that we can institute effective methods for remineralization and stop the net demineralization. The caries process is a dynamic continuum, and current detection methods need more study and comparison to the "gold standard."45 With improved methods for caries detection, Ekstrand46 suggests the need for potential clinical trials using non-cavitated lesions. These early detection methods need evaluation but are suggested for clinical trials of therapies aimed at correcting the demineralization/remineralization imbalance in individuals at risk. Imrey and Kingman47 reviewed this area and suggested data analysis will be needed that fully exploits ordinal or continuous-scale outcome measures. Hopefully, we will continue to see more clinical trial data with methods that measure early carious lesions in a quantitative manner. We will then be able to apply these methods for individual patient therapy involving remineralization approaches.