# Dental Microstructural Imaging: From Conventional Radiology to In Vivo Confocal Microscopy
## 4 In Vivo Dental Imaging
### DIAGNOdent and Fluorescent Methods  
With a different technical approach, and despite the heterogeneity of verifiable data, DIAGNOdent has been highlighted as a fluorescence-based method that demonstrates high values of sensitivity for the in vivo diagnosis of dental caries [73]. DIAGNOdent is a commercial device that works on the principle of tissue autofluorescence, similar to VELscope and other clinical tools used in dentistry and in oral medicine to establish the emitted fluorescence from oral soft tissues affected by suspicious lesions [41]. In general, \"fluorescence is the property of some intrinsic molecules called fluorophores to absorb light at a particular wavelength and to re-emit it at a longer wavelength\" [41]. DIAGNOdent consists of a pen-like probe that enlightens the tooth with a safe and painless laser beam at a wavelength of 655 nm to measure its internal fluorescence [74]. The same optic also has a fluorescence detector to quantify the amount of light reflected from the tooth. In detail, the fluorescence emitted by decayed tissue is higher than the sound enamel, and the entity is shown on the display of the device as a numeric value ranging from 0 to 99.  
[PERSON] et al. investigated this laser fluorescence-based device for detecting primary molar caries [75]. The authors performed both in vitro and in vivo analysis, achieving high validity data showing good repeatability for caries assessment.  
Such fluorescence-based devices have been profoundly illustrated in the literature for their potential feasibility for in vivo visualization of caries lesions [76; 77; 78; 79]. In 2020, [PERSON] et al. performed a meta-analysis to evaluate the diagnostic accuracy of fluorescence-based devices for detecting and diagnosing enamel decays, including 133 studies [80]. That large amount of papers used led to non-uniform results concerning the sensitivity and sensibility of the different instruments and approaches. Nevertheless, one year later, the same authors conducted a similar meta-analysis investigation to assess the diagnostic accuracy of electrical conductance devices in evaluating non-cavitated coronal tooth decay [81]. On this occasion, their design included only seven studies; thus, their study and the reported data should be considered insufficient due to the lack of significant evidence.  
In 2021, [PERSON] et al. compared the DIAGNOdent pen(tm) device for the in vivo assessment of incipient caries on the occlusal surfaces of permanent teeth with visual examination according to ICDAS clinical criteria [17; 82]. However, the accuracy values obtained through the use of the DIAGNOdent pen(tm) device did not prove to be able to contribute significantly in comparison with ICDAS visual examination.  
[PERSON] and colleagues sustained a similar investigation to the abovementioned one, comparing the validity of DIAGNOdent pen(tm) data with clinical observations based on ICDAS criteria [83]. Their study evaluated pit-and-fissure non-cavitated lesions in young permanent molars; statistical analysis showed no difference between the ICDAS code and DIAGNOdent pen(tm) measurements, highlighting a significant agreement between these two methods.  
Lastly, in 2022, [PERSON] et al. compared DIAGNOdent pen(tm) examination and clinical photographs to detect white spot lesions in patients subjected to multi-bracketed fixed orthodontic treatment [84]. Their results showed higher sensitivity and specificity values for clinical photographs than the DIAGNOdent pen(tm), thus concluding that photographs deliver more relevant data in the diagnosis and estimation of the severity of demineralized lesions during multi-bracketed fixed orthodontic treatment.