Analysis of the transparent surface layer formed at the surfaces of arrested enamel caries lesions with tomographic imaging methods

Abstract

BackgroundOptical coherence tomography (OCT) can acquire high-resolution images of lesion structure in vivo to assess lesion activity. The surface layers of arrested enamel caries lesions (ECLs) have a higher mineral content than the lesion body with a reduced porosity that inhibits the penetration of fluids into the lesion and appears with reduced reflectivity OCT. This study aimed to use microcomputed tomography (microCT) to measure the mineral content of the transparent surface layer (TSL) that appears on OCT images. MethodsOCT and microCT were used to measure the reflectivity and relative mineral density profiles of 20 bovine enamel samples that had simulated arrested ECLs, 44 extracted teeth with 17 proximal ECLs, 10 occlusal ECLs, and 17 lesions caused by fluorosis. TSL thickness (OCT), surface layer thickness (microCT), and the minimum and maximum densities of the TSLs were determined from matched OCT and microCT profiles. ResultsFor all samples, the TSL thickness measured with OCT was significantly less than the surface layer thickness measured with microCT (P < .05). Mean maximum mineral densities in the TSL were statistically similar to sound human enamel (P > .05) and significantly higher (P < .05) than the mean minimal mineral densities of the TSL. ConclusionsThe maximum mineral densities of the TSL measurable with OCT approach those of sound enamel suggesting that almost complete remineralization has occurred in the TSLs. This study provides further confirmation that the presence of a TSL in OCT images is a key indicator of lesion arrest.