Application of quantitative light-induced fluorescence for assessing early caries lesions.

Quantitative light induced fluorescence (QLF) is a nondestructive diagnostic method for the longitudinal assessment of early caries lesions in time. When a tooth becomes carious the fluorescence radiance at the location of the caries lesion decreases. The fluorescence image of enamel with incipient lesions can be digitized and then the fluorescence loss in the lesion can be quantified in comparison to the fluorescence radiance level of sound enamel. Changes in fluorescence radiance and lesion area can be followed in time to measure lesion development. The amount of fluorescence radiance loss is related to the mineral loss in the lesion. The technique can be used in vitro, in situ and in vivo to monitor mineral changes in lesions. Applications of QLF are found in the testing of products designed to inhibit demineralization and promote remineralization of caries. The method has been successfully applied to smooth surfaces as well as occlusal surfaces, but application on approximal lesions is not yet possible.