Photonic Methods for the Assessment of Lesion Activity

Background/Objectives: This review describes the advantages of new photonic-based approaches for assessing the activity of caries lesions. Many lesions have been arrested or are non-carious developmental defects, such as fluorosis, which do not require intervention. New methods are needed to assess lesion activity and avoid unnecessary removal of the tooth structure. Methods: At present, there are no reliable methods for assessing lesion activity in vivo. Nondestructive optical monitoring of lesion structure and the changes in light scattering that occur during drying offer the potential for lesion activity assessment during a single examination. Since optical diagnostic instruments exploit changes in the porosity and the permeability of the lesion, they have the potential to assess whether lesions are active and expanding or arrested and undergoing remineralization. Optical coherence tomography (OCT), Raman imaging and fluorescence loss, thermal and short-wavelength infrared (SWIR) reflectance measurements during lesion dehydration with forced air are presented. Results: Clinical studies have shown that optical coherence tomography is capable of showing distinct structural differences between active and arrested lesions on coronal and root surfaces. Differences in the kinetics of dehydration measured using reflectance measurements at SWIR wavelengths coincident with water absorption bands also show great potential. Conclusions: OCT and dehydration imaging at SWIR wavelengths have great potential for assessing lesion activity since they can also be used for caries screening, are safe for frequent monitoring and do not require the application of external agents.