الفهرس 
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Abstract
Summary
This study aimed to assess the effect of incorporating an amelogenin-inspired peptide, calcium-phosphate supersaturated solution and/or fluoride in the remineralization protocol of artificially demineralized enamel.
A Fluorescein isothiocyanate (FITC) labelled peptide, inspired by amelogenin, three remineralizing solutions (I; Ca 2+& PO43- ions, II; Ca 2+, PO43- & F- ions and III; F- ions) and artificial saliva were prepared. A total of 50 enamel samples were prepared and randomly divided according to the peptide treatment and the remineralizing solution used into 8 experimental groups (n=5), peptide-treated (P/I, P/II, P/III and P/AS) and non-peptide treated (NP/I, NP/II, NP/III and NP/AS). Furthermore, a control healthy and control demineralized enamel groups were prepared (n=5).
A window (4x4mm2) was prepared on the surface of each enamel sample. Fourty-five enamel samples of the control demineralized enamel group and the 8 different experimental groups were then immersed for 3 days in a demineralizing solution to induce artificial demineralized lesions. Fourty enamel samples in the different experimental groups were further subjected to demineralization/remineralization challenge (pH-cycling) for 9 days.
The peptide binding capacity to demineralized enamel was evaluated using confocal laser scanning microscope (CLSM). Moreover, the ability of the tested peptide to induce spontaneous mineralization was evaluated using transmission electron microscope (TEM) with selected area electron diffraction (SAED).
The newly formed mineral layers deposited on the surface of enamel samples in the different experimental groups were evaluated regarding their degree of crystallinity (XC) and degree of orientation (R-value) using X-ray diffraction (XRD).
The mineral content of the newly formed mineral layer was calculated as Raman intensity change ratio (%ICR) from the Raman intensity of phosphate (PO43-) peak of enamel at different conditions as healthy enamel, after demineralization and after remineralization using high-resolution confocal Laser Raman microspectroscopy.
The mechanical properties of the remineralized enamel surfaces were evaluated using Vicker surface hardness test. Young’s modulus and nanohardness were also evaluated using nanoindentation. Moreover, the recovery percentage in microhardness (SMHRR%), Young’s modulus (RE%) and nanohardness (RH%) were calculated with respect to the healthy enamel condition. The morphology of remineralized enamel surfaces were evaluated using field emission scanning electron microscope (FESEM ) supplemented with energy dispersive X-ray spectroscopy (EDX) for elemental analysis.
The results of the current study showed that the tested peptide was able to induce the deposition of hydroxyapatite (HAP) crystals after 20 minutes that transformed into rod-like crystals after 24 hours in peptide-treated groups. On the other hand, the remineralizing solutions in non-peptide treated groups were unable to crystallize HAP up to 24 hours.
Regarding the peptide binding capacity to demineralized enamel surface, image analysis using Image J software showed that the tested peptide was able to bind to approximately 50 % of the total area of demineralized enamel surface.
XRD results showed that the peptide application in peptide-treated groups resulted in a significant enhancement in both XC and R-value in comparison to their corresponding alternatives in non-peptide treated groups.
Regarding the results of Raman microspectroscopic analysis, all peptide-treated groups showed significantly higher mineral content recovery (ICR%) compared to their corresponding counterparts in non-peptide treated groups with the highest significant value recorded by group P/II. Additionally, an upright shift " ~ " 3 cm-1 was detected in the position of (PO43-) peak in groups P/II and NP/II, suggesting the deposition of fluoridated hydroxyapatite (F-HAP) crystals.
Microhardness and nanoindentation tests results showed significantly higher surface microhardness recovery ratio (SMHRR%), elastic modulus recovery (RE%) and nanohardness recovery (RH%) in all peptide-treated groups compared to their corresponding alternatives in non-peptide treated groups.
Scanning electron microscope images showed that the peptide was able to remineralize the enamel with organized and ordered HAP crystals that appeared clumped together in all peptide-treated groups, however, no prismatic structure was detected. A dense layer of HAP that were detected in P/I, P/II and P/III. EDX analysis revealed that HAP crystals were detected in all groups except NP/I, where octa-calcium phosphate was observed.