Optical clearing agents based on metallic and dielectric nanoparticles for caries diagnostic by optical coherence tomography

Objective This study aimed to assess the effect of titanium dioxide (TiO 2 ) and silver (Ag) nanoparticles dispersed in glycerol or water, serving as optical clearing agents nanocolloids (OCAs-NC), for improving optical coherence tomography (OCT) images and highlighting incipient lesions in ex vivo human teeth. Materials and methods Twelve human teeth with incipient lesions were divided into seven groups according to the OCA-NC; they were subjected to G1 (air), G2 (glycerol), G3 (TiO 2 0.1%), G4 (TiO 2 0.01%), G5 (TiO 2 0.001%), G6 (AgNO 3 10%), and G7 (AgNO 3 100%). The OCA-NC was applied to the occlusal surface, and two-dimensional images of the specimens were analyzed using OCT (930 nm central wavelength; 100 nm bandwidth; 5 mW output power; axial resolution of 7/5.3 μm in water and air, respectively; lateral resolution of 8 μm; and light penetration depth of 1.6 mm inside the sample). Results The findings demonstrated that the utilization of OCAs-NC containing metallic or dielectric nanoparticles (AgNO 3 and TiO 2 ) led to improved differentiation between sound and demineralized enamel on occlusal surfaces. Additionally, it enhanced the depth of image penetration when analyzing this hard tissue with OCT. Clinical relevance In the current context of minimally invasive dentistry, the use of OCAs-NC in conjunction with OCT can provide clinicians with early diagnosis, allowing for the determination of less/more invasive therapies and consequently halting the disease before cavitation of dental tissues occurs.