Scientific studies on QLF are accumulating in the literature. Technical validation of QLF has generally been favorable (see, for example the work done by the group of Angmar-Månsson in 199636) showing good correlation between mineral loss and deltaF. Its use for smooth surfaces and occlusal surfaces was reported by van der Veen and de Josselin de Jong,37 and data was published on its use for demineralization and remineralization as a potential tooth for clinical assessment by Amaechi and Higham.38 Its use for the detection and monitoring of secondary caries was published by Gonzalez-Cabezas et al.39 Later, its use was coupled with fluorescent dye to effectively measure root surface demineralization/remineralization and shows promise as an in vivo method for root caries detection and classification.40

QLF detection of red fluorescence is showing promise as a key method for determining the presence of caries activity. More and more studies are suggesting a strong correlation between active caries and red fluorescence. A study by Lee et al.41 demonstrated that the red fluorescence measured using QLF-D correlated with the cariogenic properties of dental microcosm biofilms in vitro. According to the authors, these data indicate “that this device can be used to detect the levels of cariogenicity of a dental biofilm.” Both of the QLF systems are broadly used in the dental research community, and the QLF-D system is quickly becoming established in dental practices outside the US. Future prospects of using this type of technology in the US for identifying and quantifying early caries, along with the ability to track progress over time, are exciting. The ability to take non-ionizing radiation measurements with QLF, recommending a treatment such as a fluoride toothpaste, and then monitoring remineralization at regular recalls, is an exciting prospect for all dental professionals.