A technology to characterize early enamel lesions is needed in dentistry. Optical coherence tomography (OCT) is a noninvasive method that provides high-resolution cross-sectional images. The aim of this study is to compare OCT with microfocus x-ray computed tomography ([Formula: see text]) for assessment of natural enamel lesions in vitro. Ten human teeth with visible white spot-like changes on the enamel smooth surface and no cavitation (ICDAS code 2) were subjected to imaging by μCT (SMX-100CT, Shimadzu) and 1300-nm swept-source OCT (Dental SS-OCT, Panasonic Health Care). In [Formula: see text], the lesions appeared as radiolucent dark areas, while in SS-OCT, they appeared as areas of increased signal intensity beneath the surface. An SS-OCT attenuation coefficient based on Beer-Lambert law could discriminate lesions from sound enamel. Lesion depth ranged from 175 to [Formula: see text] in SS-OCT. A correlation between [Formula: see text] and SS-OCT was found regarding lesion depth ([Formula: see text], [Formula: see text]) and also surface layer thickness ([Formula: see text], [Formula: see text]). The images obtained clinically in real time using the dental SS-OCT system are suitable for the assessment of natural subsurface lesions and their surface layer, providing comparable images to a laboratory high-resolution [Formula: see text] without the use of x-ray.
Regeneration of severely damaged enamel (e.g. deep demineralized lesions) is currently not possible, because the structural units of enamel crystal construction are removed after its maturation. The aim of this in vitro study was to evaluate the effect of surface impregnation by leucine-rich amelogenin peptide (LRAP) on the remineralization of eroded enamel using micro-focus x-ray computed tomography (µCT). Fifteen bovine enamel blocks were embedded in resin and three zones (sound, demineralization, and remineralization) were defined on each specimen. Lesions were prepared by immersing the samples in demineralization solution for 7 d. The samples were soaked in distilled water or 60 or 120 µg mL(-1) solution of LRAP in water for 30 min. After the surface treatment, specimens were incubated in artificial saliva for either 5 or 10 d at 37 °C. The amount of mineral gain (dΔZ%) and the relative changes in the lesion depth (dLD%), obtained from µCT, were used to evaluate the effect of LRAP on the remineralization of lesions. The effects of LRAP on cross-sectional integrated hardness ΔINH were studied after 10 d using nanoindentation. ANOVA test was used to determine the effect of time and/or LRAP concentration on dΔZ%, dLD% and ΔINH mean values. Tukey's analysis was used for multiple comparison testing (α = 0.05). Analysis of µCT data showed significant effect of time and LRAP concentration on the dΔZ% (p = 0.013, p = 0.003) and the dLD% (p< 0.001, p = 0.002) mean values. The nanoindentation hardness was significantly improved by 120 µg mL(-1) LRAP (p = 0.02). Also, the peptide treatment affected the mineral distribution throughout the lesion by inhibiting of superficial deposition. This study showed that the treatment of eroded lesions in enamel by LRAP can improve and regulate the pattern of remineralization in vitro.
This study evaluated low-viscosity resin potential as enamel marginal gap sealant for existing composite restoration. Standard restorations with marginal gaps were created in bovine teeth; gaps were resealed using G-Bond Plus (GB, GC, Tokyo, Japan) or Icon (ICN, DMG, Hamburg, Germany) with or without HCl pretreatment (n=8). Swept-source optical coherence tomography (SS-OCT) images were taken before and after resealing of the margin and thermal cycling to calculate enamel marginal gap extent. Cross-sectional microscopy was performed to confirm SS-OCT findings. SS-OCT showed remarkable reduction of backscatter signal at enamel margins after application of the low-viscosity resin. Enamel margin resealing significantly decreased gap and there was a significant difference between ICN (regardless of HCl pretreatment) and GB, while thermal cycling increased gaps (p<0.05). The low-viscosity resin could effectively infiltrate micro-gaps at enamel margins and improve sealing of an existing composite restoration. Resin infiltration is a viable option for resealing intact restorations with open margins.
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