Abstract
Optical coherence tomography (OCT) is a potential clinical tool for enamel lesion monitoring. Swept-source OCT findings were compared with cross-sectional nanohardness findings of enamel. Subsurface bovine enamel lesions in three groups were subjected to (1) deionized water (control), (2) phosphoryl oligosaccharide of calcium (POs-Ca) or (3) POs-Ca with 1 ppm fluoride for 14 days. B-scans images were obtained at 1310-nm center wavelength on sound, demineralized and remineralized areas after 4, 7, and 14 days. The specimens were processed for cross-sectional nanoindentation. Reflectivity from enamel that had increased with demineralization decreased with remineralization. An OCT attenuation coefficient parameter (μt), derived based on the Beer-Lambert law as a function of backscatter signal slope, showed a strong linear regression with integrated nanohardness of all regions (p<0.001, r=-0.97). Sound enamel showed the smallest, while demineralized enamel showed the highest μt. In group three, μt was significantly lower at four days than baseline, but remained constant afterwards. In group two, the changes were rather gradual. There was no significant difference between groups two and three at 14 days in nanohardness or μt POs-Ca with fluoride-enhanced nanohardness of the superficial zone. OCT signal attenuation demonstrated a capability for monitoring changes of enamel lesions during remineralization.
Highlights
Dental caries is a multi-factorial disease process that results in localized dissolution and destruction of the calcified dental tissues
There was a conspicuous prominence of the enamel lesion shown in the Optical coherence tomography (OCT) image of DEM area, with a high reflectivity from the lesion and a sudden drop of the reflectivity just beneath the lesion, which revealed a lesion boundary
The real depth can be calculated by dividing the optical depth over the approximate refractive index of enamel (1.6) which was equal to 134.1 Æ 8 μm. With remineralization in both phosphoryl oligosaccharide of calcium (POs-Ca) groups, the intensity of the optical boundary declined and visual changes were observed in the OCT image
Summary
Dental caries is a multi-factorial disease process that results in localized dissolution and destruction of the calcified dental tissues. An incipient lesion or subsurface lesion is a type of caries that has an intact enamel surface with no cavitation.[1,2] Developing of an enamel lesion without breakdown of the outer surface is more common in case of early lesions. The surface layer covering the lesion is usually a mineral rich area with less dissolution susceptibility, which is unlike the subsurface area where the dissolution takes place and has less mineral content.[1] Once the lesion reaches the dentin, it will spread eventually causing progression of the lesion with intact enamel, at which stage a surgical intervention to remove the caries is inevitable.[3] On the other hand, the demineralization process can be reversed, especially at early stages, in the presence of bioavailable calcium and phosphate ions in the environment. It is believed that remineralization would be accelerated or
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